Nest architecture and colony composition in two populations of Ectatomma ruidum sp. 2 (E. ruidum species complex) in southwestern Colombia

Carlos Santamaría; Inge Armbrecht; Jean-Paul Lachaud

doi:10.1371/journal.pone.0263382

. 2022 Feb 2;17(2):e0263382. doi: 10.1371/journal.pone.0263382

Nest architecture and colony composition in two populations of Ectatomma ruidum sp. 2 (E. ruidum species complex) in southwestern Colombia

Carlos Santamaría ^1,^*, Inge Armbrecht ¹, Jean-Paul Lachaud ^2,^3,^*

Editor: Nicolas Chaline⁴

PMCID: PMC8809609 PMID: 35108326

Abstract

Nest architecture plays a fundamental role in the adaptation of ants to their habitat, favoring the action of economically important species. Ectatomma ruidum sp. 2 (ruidum species complex) is a biological control agent in Neotropical agroecosystems, exhibiting high bioturbation impact due to high nest densities. The architecture and composition of 152 nests were studied in two Andean populations of southwestern Colombia, 24 of them being cast using the paraffin wax technique. Nest entrance was a single, circular, 4 mm hole at ground level, without any special external structure, connected to a single vertical tunnel communicating with successive half ellipsoidal chambers. Nests were extremely shallow (depth range: 28.7–35.4 cm), with an average of six chambers and an overall volume of 92.2 cm³ per nest. The deeper the chamber, the smaller its volume. Nest building was independent of plants or roots, and no surface or underground physical connections were found between neighboring nests. Few nests possessed a queen, and neither ergatoids nor microgynes were recorded. Despite significant interactions between localities and the number of both males and workers, queen presence had an overall highly positive effect on the number of workers and larvae and a negative one on the number of gynes. Overall, the studied Colombian populations of E. ruidum sp. 2 retained the simple nest structure described for other species of this species complex and for colonies of the same species from other geographical areas, though they constrasted in their extreme shallowness. Our data suggest that E. ruidum sp. 2, at the local level, does not follow the usual monodomic pattern of this species with facultative polygyny but, rather, has a polydomic pattern with monogyny, perhaps related to the extreme shallowness of the nests due to soil structure, which could significantly enhance the queen’s reproductive inhibition previously reported for this species.

Introduction

Ants are considered ecosystem engineers [1] and their functional role on soil dynamics is directly related to both their key impact as soil modifiers and their considerable bioturbation activity through nest-building [2–6]. Nest architecture and nesting material choice play a fundamental role in the adaptation of ant colonies to their habitat and their survival through changes in soil physical properties and the resulting effects on both flooding resistance and thermal and humidity regulation [3, 7]. In Africa, for example, the workers of Brachyponera sennaarensis use the hydrophobic properties of the surface sand, lining the interior of the galleries with this dry sand to prevent flooding [8]. On the other hand, humidity and temperature conditions can vary according to both the location of the nest and the insulation properties of the nest material [9, 10] but also according to the depth of the chambers. In various species, adults position themselves within the nest according to a temperature gradient according to their physiological state and age [11, 12]. Similarly, immature individuals are distributed in the chambers according to their developmental stage and the thermal requirement ensuring ideal conditions for their development [11, 13].

Numerous works have highlighted that ant nest architecture is species-specific and influences not only the development of the colonies, their composition, and their spatial structuration [12, 14–18] but also their collective behavior [18, 19]. Nest architecture has been described with some details for a few species of the ectatommine Neotropical ant genus Ectatomma (E. opaciventre [20], E. planidens [21] (mistakenly identified as E. edentatum [22]), E. brunneum [23, 24], and E. vizottoi [25]), but a detailed account of the population found within each nest chamber has never been included. Furthermore, for E. ruidum and E. tuberculatum, the two most common and important species of the genus due to their economic impact as biological control agents [26–28], much of the information concerning their nest architecture has been obtained indirectly, with only the description of a few nests and a lack of information concerning the volume of the chambers and the distribution of the individuals among them [26, 29, 30].

Ectatomma ruidum sp. 2 belongs to the E. ruidum species complex, which currently consists of at least five derived morphospecies. These are Ectatomma ruidum sp. 1, 2, 3–4, 5 and a possible 2x3 hybrid [31–34]. In terms of habitat, this species complex is widely distributed, occupying agricultural systems, savannas, and forests from sea level to an altitude of 1500–1600 m [26] and up to 2200 m [35]. Its latitudinal distribution in the Americas ranges from the states of Jalisco and Nayarit in Mexico to southeast Ecuador and northern Brazil in the Amazon region [31, 36]. In Colombia, both morphospecies E. ruidum sp. 1 and sp. 2 have been recorded [37, 38]. Regarding their feeding habits, although Ectatomma species are considered to be hunters, the E. ruidum complex is characterized by a very broad generalist diet that includes a great variety of prey, vegetable carbohydrates (fruits, extrafloral nectaries), honeydew produced by hemipterans, carcasses of both invertebrates and other animals, and seeds [27, 30, 39–41]. This species is a functional agent in Neotropical agroecosystems [30, 38, 39], exhibiting a high bioturbation impact during nest excavation due to high nest densities [6]. In Mexico, Costa Rica, and Panama, this species has been considered monodomous (each colony occupies a single nest structure) due to the architecture of its nests being characterized by only one nest per colony and each nest being an individual entity independent from other, neighboring nests (each nest contains at least one queen and shows territoriality against neighboring homospecific nests) [30, 42, 43]. However, the common occurrence of intraspecific cleptobiosis, that is, the theft of food resources between neighboring nests [42, 44, 45], and, on some occasions, the transport of workers and even brood between them [46], suggest the possible existence of a more complex nesting structure. More specifically, in southwestern Colombia, this assertion is not at all clear given that various fragmentary observations [47–49] have reported quite frequent surface relationships between neighboring nests and the absence of queens in most of them, suggesting a polydomic nesting strategy (a colony occupies two or more spatially separated nests) [6, 28].

The purpose of this study was both to obtain basic information about the physical structure of the nest of E. ruidum sp. 2 by studying its nest architecture (structure of the entrance, number, volume, and depth of the chambers, depth of the nest), the composition of its colonies (number of queens, alate females (gynes), males, workers, pupae and larvae, and presence of possible myrmecophilic organisms), and the distribution of the individuals within the different chambers, and to try to correlate this information with the local nesting strategy (monodomy vs. polydomy). The aim of the study was to answer the following questions: (1) Does the nest architecture of E. ruidum sp. 2 show species-specific characteristics? (2) Are the colonies monogynous or polygynous and does the presence of the queen influence the physical and populational characteristics of the nests? (3) Does the nest architecture confirm the physical independence of neighboring nests and support a polydomic nesting strategy?

Material and methods

Ethics statement

N/A. Collection and transport of insect specimens were authorized by the Autoridad Nacional de Licencias Ambientales (Permit No. 1070 to the Universidad del Valle). The collection did not involve endangered or protected species. Research and fieldwork complied with the current laws of Colombia.

Study areas and nest extraction

The Andean populations of E. ruidum sp. 2 from two locations in southwestern Colombia were studied. The first locality was in the municipality of Santiago de Cali (3°22’33.52" N, 76°31’47.48" W), in the Department of Valle del Cauca, specifically in the Mélendez Campus of the Universidad del Valle (henceforth referred to as ‘Cali’). The mean altitude and temperature are 974 m.a.s.l. and 24.7°C, respectively, with an annual rainfall of 1400 mm distributed in a bimodal pattern with two high peaks in April-May and October-November [50]. With a total area of 100 ha, this is a predominantly urban zone, with tree-lined areas and others without major tree cover. In a completely open 50 x 50 m plot (without bushes or trees) situated at the eastern end of the campus, all E. ruidum sp. 2 nests present were located through the use of bait and the tracking of foragers. The number of nests present in the area was recorded twice: between June and July 2016, coinciding with the dry season, and in January 2017, usually coinciding with a less drastic dry period during the transition season (period of transition from the rainy season to the dry season), although the climatic conditions were not respected because unusual rainfall for this period was recorded in January 2017. All the nests found in the first sampling were marked with flags (Fig 1A) and GPS and mapped with grids in the field. Subsequently, to avoid problems associated with the loss of flags, they were marked with plastic bottle caps, buried in the ground next to the nest opening, so they could be compared to those found in the following sampling. During the two last weeks of January 2017, a sample of 118 E. ruidum sp. 2 nests was extracted, from which 15, containing less than 10 workers and no sexual adults and brood, were considered abandoned and were not considered for subsequent analysis. For each nest, the number of chambers and the total nest depth were recorded.

Fig 1 — (A) study area at the Campus of Universidad del Valle, Cali, with the entrances of the nests marked by a flag, (B) wax casting of nest #8 embedded in its natural habitat prior to extraction, (C) the same nest #8 once cleared of its soil matrix; the scale bars correspond to 10 cm. Photos: C. Santamaría.

For 24 of these randomly chosen nests, the extraction was performed using the paraffin wax technique [51]. In previous studies, materials such as molten zinc or lead, dental plaster, cement, paraffin wax, or even ice have been used [15, 16, 19, 51–53]. We used paraffin wax because it is an inexpensive material and is easy to obtain and handle. Primarily, it allows the composition of each chamber to be easily determined as, by melting the wax in each section, both the workers and the brood can be obtained intact [51]. The paraffin wax was poured into the entrance hole of each nest and left to dry for 24 hours; subsequently, each nest was extracted as gently as possible to prevent the paraffin from breaking (Fig 1B). Photographs were taken of the structure of the nests during the extraction process, ensuring that, if the nests were to disintegrate, their original structure could be recovered. Photographs of the nests cleared of their soil matrix were taken against a black background to obtain an enhanced definition of the contours in terms of nest shape and structure (Fig 1C). Using the geometric shape of structural elements in a similar way to that described for studying morphological transitions in the Lasius niger nest shape [54], we defined the start and end of both the tunnels and the chambers that were easily distinguishable because chambers were horizontal to the ground while the tunnel was rather vertical and clearly elongated. Chambers began at the point where the tunnel leading to them widened. Following extraction and photography, the dimensions (length, width, height) of each chamber were measured with a millimeter ruler to obtain an estimate of the chamber volume; additionally, tunnel length and total depth of the nests were recorded. Then the nests were melted down chamber by chamber and the content of each one was recorded: number of queens, gynes, males, workers, pupae, and larvae, as well as the presence of other associated arthropods, if any.

The second locality was the Vereda El Rosal, in the southwestern region of the Colombian Andes, municipality of Caldono, Department of Cauca (2°49’ N, 76°32’ W) (henceforth referred to as ‘Cauca’). The mean altitude and temperature are 1450 m.a.s.l. and 21.5°C, respectively, with an annual rainfall of 2191 mm distributed in a bimodal pattern with two high peaks in April-May and October-November [55]. Between October and December 2016, 49 nests were extracted, with only the total depth of the nest recorded, and not the number of chambers.

Data analysis

Pearson’s correlation tests were performed to identify possible relationships between the numbers of workers, larvae, and pupae, and between chamber volume or group size (adults + brood) and nest depth. A Chi-squared test was performed to determine whether the proportion of queenright nests differed between both populations. A Binomial Generalized Linear Model (Binomial GLM) was performed to test for differences between the population composition of the excavated nests (number of larvae, pupae, workers, males, and gynes) and nest structure (nest depth) depending on whether or not a queen was present. Twelve exploratory models were first adjusted. The final chosen model used was as follows: glm (formula = Queens ~ locality + gynes + workers + larvae + depth + locality * male + locality * workers, family = binomial, data), with ‘queen presence’ as the random variable and using the library "car" [56].

To detect trends among all variables in nests with or without a queen, we performed a Principal Component Analysis (PCA) to determine which variables clustered with respect to queen presence. The explored variables were number of gynes, males, workers, larvae, and pupae and nest depth. We used the libraries "FactoMineR", "factoextra" and "corrplot". A separate test was conducted for all excavated nests and each locality. All statistical analyses were performed using R (version 4.1.1) [56], with a significance level of 5%.

Results

Nest abundance and general considerations on E. ruidum sp. 2 nest architecture

During the first nest sampling in June-July 2016, 457 nests of E. ruidum sp. 2 were recorded in the 50 x 50 m plot in ‘Cali’ (i.e., 1828 nests ha^-1). In contrast, in January 2017, 942 nests of this species were found in the same plot (i.e., 3768 nests ha^-1), with some of the former nests having disappeared, while many new nest entrances appeared. Although the difference between the first and second assessments was 485 nest entries, it was estimated that about 200 entries recorded during the first sampling had disappeared, making the number of new nests built between the two samplings actually 685. The average distance between neighboring nests was about 74 cm, indicative of the high nest density at this site. There was some worker traffic between nests, but we did not record an average per nest. However, we regularly observed workers transporting other individuals from one nest to another nearby.

All the E. ruidum sp. 2 nests extracted in this study were built without the presence of roots or plants, although in some cases they were found near the base of grass. Small supplementary chambers with refuse material or stored food were not present in any of the nests. In particular, no surface or underground communication was observed using tunnels or galleries between the different nests, which all had the same isolated vertical arrangement, typical of the nests of this genus (Fig 2).

Fig 2 — (A) nest #3 (depth: 28 cm), (B) nest #6 (depth: 27 cm), (C) nest #22 (depth: 29 cm) (see S1 Table for detailed nest features). The scale bars correspond to 5 cm. Photos: C. Santamaría.

Although not quantified, some specimens of Nicoletiidae (Zygentoma) could be observed in most nests. However, no other associated organisms were found during this study.

Nest casts

The nests had only one circular entrance/exit hole, with an average diameter of 4.2 ± 0.2 mm (mean ± SEM) (see S1 Table); no specific structure (cone, tumulus, or chimney) was observed. In all cases, both the access tunnel and the chambers connected through this single tunnel were vertically arranged (Fig 2). Only one of the nests extracted using the paraffin wax technique (nest #6, Fig 2B) presented a second vertical tunnel connecting two non-contiguous chambers.

No galleries were found interconnecting the chambers or tunnels of different nests, either above or below ground, and no small ‘appendix’ chambers containing waste or stored materials (seeds, food, or insect remains) were observed. The first chamber was very superficial, at a mean distance from the entrance of 6.7 ± 0.2 cm (Table 1), and all the nests were very shallow with a mean depth of 29.1 ± 0.8 cm (range: 22–36 cm) (see S1 Table). Spacing between the chambers was relatively constant with no significant differences in the length of the tunnels connecting contiguous chambers (Table 1).

Table 1. Mean (± SEM) volume and depth of the chambers, tunnel length, and composition of the population of each chamber according to its relative position for the 24 E. ruidum sp. 2 nests extracted using the paraffin wax technique.

* The average values reported for the ninth chamber concerning the number of workers and gynes, must be considered with reservation because only one nest with nine chambers could be cast; they cannot be directly compared to the mean values found in the other chambers.

Chamber	n	Volume (cm³)	Chamber depth (cm)	Tunnel length (cm)	Queen	Workers	Males	Gynes	Larvae	Pupae
#1	24	28.6 ± 2.6	6.7 ± 0.2	4.6 ± 1.1	0.1 ± 0.1	10.2 ± 2.6	1.2 ± 0.3	0.1 ± 0.1	1.9 ± 0.8	3.9 ± 1.4
#2	24	23.0 ± 2.6	9.6 ± 0.4	3.0 ± 1.3	-	10.1 ± 2.0	0.9 ± 0.3	0.2 ± 0.1	1.3 ± 0.7	1.6 ± 0.8
#3	24	16.0 ± 2.2	14.2 ± 0.7	4.7 ± 2.3	-	15.5 ± 3.3	0.8 ± 0.3	0.3 ± 0.1	1.5 ± 0.7	2.6 ± 1.1
#4	22	11.0 ± 1.5	18.5 ± 0.7	5.1 ± 1.9	-	10.5 ± 3.3	0.1 ± 0.1	0.1 ± 0.1	0.9 ± 0.7	1.6 ± 0.9
#5	21	9.3 ± 1.9	23.1 ± 0.8	4.8 ± 1.9	-	8.2 ± 1.8	0.1 ± 0.1	0.1 ± 0.1	0.1 ± 0.1	0.2 ± 0.2
#6	17	5.8 ± 0.9	26.5 ± 0.9	4.2 ± 0.9	-	7.9 ± 1.8	0.1 ± 0.1	0.1 ± 0.1	-	-
#7	10	4.6 ± 0.9	29.2 ± 0.8	3.7 ± 1.5	-	4.4 ± 1.6	-	0.6 ± 0.4	-	-
#8	5	2.4 ± 1.0	31.6± 1.2	3.0 ± 0.7	-	5.0 ± 2.4	-	0.2 ± 0.2	-	-
#9	1	2.2	33.8	5.0		5.0 *	-	4.0 *	-	-

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The tunnel walls and both the walls and floors of the chambers were lined with a cement-like, very compact, thin surface, smooth in appearance. The shape of the chambers was a half ellipsoid, and the deeper the chamber, the smaller its volume and group size (adults + larvae + pupae) per chamber (Table 1 and S2 Table), as evidenced by a significant negative correlation between chamber volume and depth (R(148) = - 0.6112; p < 0.001; Fig 3A) and between group size per chamber and chamber depth (R(148) = - 0.2656; p = 0.001; Fig 3B). However, there was no significant relationship between the number of workers, larvae, or pupae found in each chamber and the volume of that chamber nor between the distribution of the larvae and pupae in the chambers and their developmental stage. The GLM binomial analysis indicated that the distribution of the intranidal worker population was significantly concentrated in the three upper chambers (F = 4.18, p < 0.0001), but not directly associated with the volume of each chamber because it was especially concentrated in the third chamber (Fig 4). Although no statistical test could be performed due to the large variation in the number of samples for each relative position of the chamber, a decreasing trend of the chamber volume was observed according to its relative position (see Table 1). The mean total volume of all the chambers was 92.2 ± 7.4 cm³ per nest (n = 24).

Fig 3 — Correlation between chamber depth and (A) chamber volume or (B) group size per chamber. The deeper the chamber, the smaller its volume (R(148) = - 0.6112, p < 0.001) and the number of ‘adults + brood’ per chamber (R(148) = - 0.2656; p = 0.001).

Fig 4 — See Table 1 for the sample size and the depth corresponding to each chamber’s relative position.

Relationships between colony composition and architectural variables

Considering the set of the 152 complete nests collected, some highly significant positive correlations, such as those found between the total number of workers per nest and the total number of larvae (S1A Fig) or pupae (S1B Fig) or between these last two categories of brood (S1C Fig), provided a good description of both the temporal and colony-level life of the colonies and their success because the higher the number of workers, the higher the brood production. Only 33 queenright colonies were found, all monogynous (S1 and S3 Tables). Depending on whether or not a queen was present, several significant correlations between the different variables related to the composition of the intranidal population and the structure of the nest were highlighted by the binomial GLM analysis (Table 2) and pairwise comparisons (S3 Table).

Table 2. Binomial GLM comparing queenright vs. queenless nests.

Only significant results of the deviance analysis between population and structural variables of the 152 complete nests of E. ruidum sp. 2 extracted during the whole study are presented here. The number of workers and larvae was significantly higher in queenright nests while queenless nests had a significantly higher number of gynes. Queenright nests at ‘Cauca’ tended to have fewer males and more workers than at ‘Cali’.

	Chi-square	Df	Probability
Gynes	47.072	1	0.0300357
Workers	315.728	1	0.921e-08
Larvae	53.687	1	0.0205009
Locality: Males	130.404	1	0.0003048
Locality: Workers	51.177	1	0.0236824

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The presence of a queen had an overall significant positive impact on the number of workers and larvae, and a negative one on the number of gynes (p < 0.00001, p < 0.02, and p < 0.03, respectively; Table 2). In a comparison between localities (Table 2 and S3 Table), there was a highly significant negative impact of the presence of a queen on the number of males in ‘Cauca’ and a significant positive one on the number of workers (p = 0.0003 and 0.02, respectively). Although nest depth in the ‘Cali’ sample (28.7 ± 0.5, n = 103, range: 19–38 cm) tended to be shallower than that in the ‘Cauca’ sample (35.4 ± 1.8, n = 49, range: 21–80 cm) (see S3 Table), the binomial GLM did not indicate a significant difference. However, the numbers of workers (65.4 ± 3.3, range: 10–190 vs. 99.1 ± 7.6, range: 21–212), larvae (25.6 ± 2. 1, range: 0–92 vs. 74.2 ± 6.8, range: 6–203), and pupae (11.5 ± 1.1, range: 0–51 vs. 57.0 ± 7.0, range: 0–194) were significantly lower in the ‘Cali’ sample than those in the ‘Cauca’ sample (see S1 and S3 Tables) as was the proportion of queenright nests (12/103 vs. 21/49; χ² (1, N = 152) = 19.0244, p = 0.000013, S3 Table). In addition, the larva-to-worker and pupa-to-larva ratios (i.e., the number of larvae or pupae inside the nest divided by the number of workers inside the nest, respectively), both good indicators of colony growth efficiency, were significantly higher in the ‘Cauca’ sample than in the ‘Cali’ sample (0.75 and 0.77 vs. 0.39 and 0.45, respectively), indicating higher efficiency and a better growth rate in the ‘Cauca’ sample.

Overall, the PCA analysis (Fig 5) provided more details, with over 80% of the total variance in each of the three situations (all nests together, ‘Cali’ nests, and ‘Cauca’ nests) explained by the five main axes (dimensions 1 to 5 on the right plots) considered. In all three situations, the PCAs evidenced a strong positive impact of the presence of a queen on the number of workers and larvae and on the depth of the nests (Fig 5A–5C), but also a negative correlation between the number of gynes and males and the other variables. When all the nests were considered and at ‘Cauca’ (Fig 5A and 5C, respectively), the presence of a queen also had a strong impact on the number of pupae. When the data from ‘Cali’ were separated (Fig 5B), where the number of chambers per nest was recorded contrary to what occurred at ‘Cauca’, such an impact of the presence of a queen on the number of pupae was not observed but there was an additional strong positive impact on the number of chambers per nest, and the negative impact on the number of gynes was particularly clear.

Globally, the number of workers (135.1 ± 7.9 vs. 60.0 ± 2.3), larvae (86.8 ± 9.0 vs. 28.7 ± 2.1), and pupae (57.9 ± 9.3 vs. 17.4 ± 2. 1), as well as the depth of the nest (37.1 ± 2.3 vs. 29.1 ± 0.5), were significantly higher in queenright nests than in queenless ones (S3 Table). In contrast, in terms of the number of sexuals (gynes and males), the mean was higher in queenless nests as compared to queenright nests (0.7 ± 0.1 vs. 0.2 ± 0.1, and 1.7 ± 0.2 vs. 1.0 ± 0.5, respectively) (S3 Table).

Discussion

Nest distribution and nest architecture traits

Nest densities recorded in ‘Cali’ (1828 and 3768 nests ha^-1) tended to be higher than the range of densities previously reported in Colombia (360 to 3020 nests ha^-1 [40, 57]) and, in particular, that found in paddocks adjacent to ‘Cauca’, which had previously been estimated between 568 and 1945 nests ha^-1 [40]. The high rate of nest relocation and new entrance openings recorded in ‘Cali’ between the first and the second nest samplings (685 nests) was likely related to the action of the rain (unusual for this period of the year) in making the soil softer and easier to dig. It probably also resulted in some level of natural deterioration of the nests or of their quality, as suggested by the presence of 12.7% of abandoned nests among the 118 collected in this plot, a rate over twice as high as that observed (5.6%) for the same species in southern Mexico [58]. Because only one collecting event was conducted in ‘Cauca’, and, furthermore, without prior sampling of nest distribution, it was not possible to disentangle the extent to which differences were the result of seasonality, site differences, or both. Nest relocation is a common phenomenon in ants [59–61] and many hypotheses exist to explain it, including colony growth, intra- and inter-specific competition, nest deterioration, and seasonality. Although our data did not allow us to determine the exact causes of these high rates of nest relocation and new nest building, they did highlight that E. ruidum sp. 2 nest-building activity in this geographic area is apparently not limited to a period of only two months as recently suggested [6] but, rather, is spread over several months of the year. This could result in a significantly greater than expected soil bioturbation impact at the local level, well above the 0.9 to 3.1 kg of dry soil ha^-1 day^-1previously reported in Colombian Andean coffee plantations over two months of digging activity [6]. A conservative, rough estimate of the overall impact of bioturbation at ‘Cali’ could probably range from 2.9 to 6.0 kg of dry soil ha^-1 day^-1 throughout a nest building period longer than two months and could even reach 6.3 to 13.0 kg of dry soil ha^-1 day^-1 under more optimal conditions (see [6]).

In previous works that focused on Ectatomma species [20, 21, 23–26], the nest architecture in this genus has been described as simple, characterized by a single entrance/exit hole connected to a unique tunnel and a chamber system arranged vertically and occasionally associated with a lodge forming an appendix. In a few species (E. opaciventre, E. brunneum and E. ruidum), depending on either habitat characteristics or climatic conditions, entrances may be more elaborate, in the form of a chimney that generally consists of a mixture of soil and plant material [20, 24, 62]. In the E. ruidum nests described in Trinidad, Mexico, and Costa Rica [26, 30, 40, 42], the entrance hole is generally 3–5 mm in diameter, followed by a more or less vertical tunnel leading to 4–6 chambers, but occasionally up to 12 [62]. Our results showed that the general structure of the nests collected in southwestern Colombia followed the same pattern with a simple ground-level entrance/exit hole of approximately 4 mm in diameter, connecting to a vertical tunnel and an average of six chambers per nest, rather evenly spaced. None of the 152 excavated nests exhibited any external structure such as a cone, mound, or chimney of compacted earth, and none of them presented the structures that some authors call ‘appendices’, as reported for E. planidens, E. brunneum, and E. vizottoi [21, 23, 25], that contain colony remains and probably serve as nest refuse or could correspond to additional chambers under construction [23]. However, in nests of E. ruidum sp. 2 from Mexico [38, 46, 62], such auxiliary chambers were rarely observed and were usually empty, although we suspected that they were sometimes used to store garbage or food. Surprisingly, apart from the regular presence of silverfishes (Nicoletiidae) in the nests of E. ruidum sp. 2 collected during our study, the absence of any other associated organisms contrasted with previous studies that identified numerous associations with species of Ectatomma, in particular the E. ruidum complex, including E. ruidum sp. 2 in the same study area [47, 63, 64].

Comparable to several species of the genus, such as E. opaciventre, E. planidens, E. brunneum, and E. vizottoi [20–23, 25], the location of E. ruidum sp. 2 nests collected in this study was independent of the plants present in the habitat, confirming previous reports for this species in southeastern Mexico [65]. This characteristic contrasts with the case of E. tuberculatum, which, in almost all cases, builds its nests at the base of the trees on which it forages, closely associating the galleries and chambers with the roots of the vegetal (tree or shrub) support [29, 65, 66].

The internal cement-like surface lining the tunnel and chambers of E. ruidum sp. 2 was similar to the tightly-packed soil coating the inner walls of the chambers and the tunnels of E. opaciventre nests [20] and, as for this species, probably consisted of earth mixed with salivary secretions. It was similar to the clay-lining of the galleries and chambers used by the attine ant Trachymyrmex turrifex [67], the adobe-like lining of chambers in Forelius chalybaeus [68] and Pogonomyrmex occidentalis [69], or the mud-like material lining used by subterranean termites [70]. Such inorganic material lining probably helps regulate the internal climate of the nest by preventing both humidity escape from the chambers and humidity entrance during rainfall [8, 67] or by stabilizing the tunnel and chamber walls [68, 71].

The mean total volume (92.2 cm³) of the nests extracted with the paraffin wax technique corresponded relatively well with the mean values of soil removed per nest (between 104.4 g and 228.8 g) reported for E. ruidum sp. 2 in this geographic area [6]. The volume of the chambers was similar to that observed in E. brunneum nests [23], although this species is slightly larger in size than E. ruidum sp. 2. The significant negative correlation found in nest casts between the volume of the chambers and their depth was in contrast to the positive correlation reported for E. opaciventre and E. brunneum, for which chamber volume generally tended to increase accordingly with depth (see Table 1 in [20] and [23], respectively). At ‘Cali’, both the number of chambers and the depth of the nests of E. ruidum sp. 2 showed a highly significant positive correlation with the worker population size. Furthermore, similar to what has been reported for E. opaciventre and E. brunneum [20, 23], adult + brood population was concentrated in the chambers with the largest volumes (52.3 ± 7.6 vs. 29.9 ± 5.6 for all the other chambers) which, contrary to these species, however, corresponded to the upper three chambers rather than to the deepest ones. As in various other ground-dwelling ant species [11, 13, 72–74], field colonies of E. ruidum sp. 2 exhibited clear brood sorting with brood piles generally clustered in specific chambers. However, contrary to what is commonly observed in laboratory nests of this species (J.-P. Lachaud, unpubl. obs.), but similar to what has been reported in field nests of Pogonomyrmex badius, where larvae and pupae are not distributed differently from one another even though the vertical distribution of the brood is skewed toward the lower chambers [12], no clear relationship was found between the distribution of the larvae and pupae in the chambers and their developmental stage.

The most significant structural characteristic of the E. ruidum sp. 2 nests from southwestern Colombia concerns, in fact, the extreme shallowness of their depth. Their mean depth, even for the deepest ones found in the ‘Cauca’ sample (35.4 ± 1.8 cm), was considerably lower than the mean depth reported for E. ruidum sp. 2 in Mexico [38, 62], where they commonly reach 80–120 cm and, occasionally, up to two meters in the dry season [58, 62]. Such a difference in nest depth between southeastern Mexican populations and our Colombian populations of E. ruidum sp. 2 cannot be satisfactorily explained by a difference in the number of adults present in the nests, as the mean global number of adults per nest was quite similar (87.0 ± 2.4, n = 683 (J.-P. Lachaud, unpubl. data) vs. 78.7 ± 3.6, n = 152, respectively). A more likely explanation could involve the very different characteristics of soil structure in both habitats (the soil in the Mexican area where nest structure has been observed, near Tapachula in Chiapas, was comparatively very loose and essentially of volcanic origin (J.-P. Lachaud, unpubl. data)), or some local biological or ecological specificities.

Queen influence on nest physical and populational characteristics and possible relationship between nest architecture and polydomy

The number of 33 queens obtained in the 152 E. ruidum sp. 2 nests extracted was extremely low, especially considering that Mexican and Costa Rican populations of this species are known to exhibit facultative polygyny [42, 75–78]. All queenright nests appeared to be monogynous and all queens were macrogynes, as were all other queens of E. ruidum sp. 2 found previously in the study area [47]. No ergatoid queens were found, though they were previously reported (as ’gynecoid’) in this geographical zone [79], and no microgyne queens (small reproductive queens) were recorded, although they have been frequently reported in different Mexican populations of E. ruidum sp. 2 from Chiapas and Quintana Roo [28, 62, 76, 78].

The large predominance of queenless nests (78.3%) in our Colombian populations of E. ruidum sp. 2, and in particular at ‘Cali’ (88.4%), contrasts sharply with the situation in southeastern Mexican populations, in which queenless colonies represented only between 8% and 11.3% of two samples of 408 and 203 complete colonies, respectively [58, 75]. As previously highlighted by Debout et al. [80], such a predominance of queenless nests, combined with the fact that gynes were significantly more numerous in these queenless nests, could indicate that this species is polydomous. Based on the total number of complete nests collected (152) and the number of queenright nests among them (33), one could argue that an average polydomous colony has 4.6 nests. However, this figure should be taken with caution and probably overestimates the actual number of satellite nests in our study area since previous results [58, 75] indicate that the absence of queens, at least in a fraction of the population, is a phenomenon that probably reflects the average natural mortality of colonies due to queen death or severe damage from heavy rains, as confirmed by the relatively high rate of abandoned nests (12.7%) reported in our study.

Queen presence in E. ruidum sp. 2 nests was positively correlated with both nest population size (number of workers, larvae, and pupae) and nest structure size (number of chambers and nest depth). A similar finding has been reported in the Spanish monogynous polydomic desert ant Cataglyphis iberica, in which queenright nests have significantly more workers than queenless nests and sexual brood is found only in queenless nests [81]. Such significant differences between queenright and queenless nests of E. ruidum sp. 2 could be related to the extreme shallowness of the Colombian nest in comparison to other known populations from Mexico, Costa Rica, and Panama and could account for the polydomic nesting strategy observed in the population studied [6, 47–49]. Nest size and, consequently, the number of chambers in which the nest population is segregated, may have important implications for the potential reproductive control by the queen because the fewer the chambers, the greater the diffusion of any regulatory pheromones released by the queen [82]. Some degree of functional inhibition, presumably of pheromonal origin, has been shown to occur in polygynous Mexican populations of E. ruidum sp. 2 [75, 77]. For example, in a study of a population of 226 nests, 42.1% of 83 polygynous colonies had only a single functional queen, although 94.4% of the 220 queens found in these polygynous colonies had been previously inseminated and would potentially have been capable of producing fertile eggs [77]. Such functional inhibition, confirmed later in another Mexican population using mitochondrial markers [78], may be better expressed in the Colombian nests due to their extreme shallowness. This hypothesis appears to be supported by the fact that at ‘Cali’, where the nests were significantly shallower than those at ‘Cauca’, both the number of queenright nests and the nest population size were significantly lower, while the presence of gynes was significantly higher than in queenright nests. Local soil constraints and the resulting nest shallowness could result in a more significant queen control in the studied Colombian populations, especially at ‘Cali’, and explain the necessity of nest splitting leading to the emergence of polydomy at the local level. In addition, high nest densities such as those observed in ‘Cali’ during this study, as well as the spatial aggregation of nests reported in some localities in southwestern Colombia [40], are probably also related to the expression of polydomy [80]; the annual cycle of this species would deserve to be studied in detail to verify the validity of such a hypothesis.

Overall, the studied Colombian populations of E. ruidum sp. 2 maintained the simple nest structure described for other species of this species complex from other geographical areas. However, our data suggest that E. ruidum sp. 2, at the local level, does not follow the usual monodomic pattern of this species with facultative polygyny but, rather, a polydomic pattern with monogyny, perhaps related to the extreme shallowness of the nests, which could significantly enhance the queen’s reproductive inhibition previously reported for this species.

Supporting information

S1 Table. Composition of the population of the E. ruidum sp. 2 nests extracted at the University Campus of the Universidad del Valle (‘Cali’) and at Vereda El Rosal, Caldono (‘Cauca’).

Nests 1–24 were extracted using the paraffin wax technique. Q: queens; G: gynes; M: males; W: workers; P: pupae; L: larvae. The number of chambers was considered only for the nests collected at ‘Cali’ (103 nests). Nests 36, 44, 48, 52, 60, 72, 76, 81, 84, 88, 96, 99, 104, 106, and 114, containing fewer than 10 workers and no sexual adults and brood, were considered abandoned and were not considered for subsequent analysis. They are not reported in this table.

(PDF)

Click here for additional data file.^{(116.2KB, pdf)}

S2 Table. Chamber dimensions (in cm), volume (in cm³), and population within each chamber for the 24 E. ruidum sp. 2 nests extracted using the paraffin wax technique at ‘Cali’.

Q: queens; G: gynes; M: males; W: workers; P: pupae; L: larvae.

(PDF)

Click here for additional data file.^{(149.2KB, pdf)}

S3 Table. Mean (± SEM) nest population and nest depth for all collected nests according to the locality or the presence (queenright) or absence (queenless) of a queen, and at each locality according to the presence or absence of a queen.

‘Cali’: Campus of the Universidad del Valle; ‘Cauca’: Vereda El Rosal, Caldano; n: nest sample size; Q: queens; G: gynes; M: males; W: workers; P: pupae; L: larvae. Student t tests were performed to compare whether the presence or absence of a queen had any effect, with *: p < 0.05; **: p < 0.01; ***: p < 0.001; ****: p < 0.0001. ^#A Chi-square test was performed to compare the proportion of queenright nests in both localities with χ² (1, N = 152) = 19.0244, p = 0.000013.

(PDF)

Click here for additional data file.^{(125.4KB, pdf)}

S1 Fig. Relationship between different categories of nest population for the 152 complete nests of E. ruidum sp. 2. extracted.

(A) between the total number of workers per nest and the total number of larvae (R(152) = 0.6976, p < 0.001) or (B) the total number of pupae (R(152) = 0.6050, p < 0.001) and (C) between both categories of brood (R(152) = 0.7252, p < 0.001).

(PDF)

Click here for additional data file.^{(947KB, pdf)}

Acknowledgments

We are indebted to Dagoberto Sinisterra, Omar Marín, Andrés López, Sebastián Narváez, Paula Palacios, Nicole Vargas, Bryan Ospina, Anderson Arenas, Sebastián Cañas and María Fernanda Rondón for their help during the hard work of nest excavation, to Julian Flavell for english revision, to Wilmar Torres, from The Universidad del Valle, Graduate Program in Biology, for statistical support, and to Nataly Amarillo for her help in designing Fig 5. We also thank four anonymous referees for helpful comments on a previous version of the manuscript.

Data Availability

All relevant data are within the paper and its Supporting Information files.

Funding Statement

Funds to CS were provided by COLCIENCIAS (National Basic Sciences Program, Code 110656933821, Contract RC. No. 0648-2013), by the ‘Vicerrectoría de Investigaciones de la Universidad del Valle’ (‘International Visibility’ call, code CI 71000), and by the founding of the research projects (2015's call #727) for National PhD students by COLCIENCIAS and the Postgraduate Department of Biological Sciences of the Universidad del Valle. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

References

1.Folgarait PJ. Ant biodiversity and its relationship to ecosystem functioning: a review. Biodivers Conserv. 1998; 7: 1221–1244. 10.1023/A:1008891901953. [DOI] [Google Scholar]
2.Lobry de Bruyn LA, Conacher AJ. The bioturbation activity of ants in agricultural and naturally vegetated habitats in semi-arid environments. Aust J Soil Res. 1994; 32: 555–570. 10.1071/SR9940555. [DOI] [Google Scholar]
3.Cammeraat ELH, Risch AC. The impact of ants on mineral soil properties and processes at different spatial scales. J Appl Entomol. 2008; 132: 285–294. [Google Scholar]
4.Tschinkel WR. Biomantling and bioturbation by colonies of the Florida harvester ant, Pogonomyrmex badius. PLoS ONE. 2015; 10: e0120407. doi: 10.1371/journal.pone.0120407 [DOI] [PMC free article] [PubMed] [Google Scholar]
5.Tschinkel WR, Seal JN. Bioturbation by the fungus-gardening ant, Trachymyrmex septentrionalis. PLoS ONE. 2016; 11: e0158920. doi: 10.1371/journal.pone.0158920 [DOI] [PMC free article] [PubMed] [Google Scholar]
6.Santamaría C, Lachaud J-P, Armbrecht I. Effects of nest building by the dominant hunting ant, Ectatomma sp. 2 (ruidum complex), on Andean coffee plantations. Pedobiologia. 2020; 79: 150626. [Google Scholar]
7.Bollazzi M, Roces F. The thermoregulatory function of thatched nests in the South American grass-cutting ant, Acromyrmex heyeri. J Insect Sci. 2010; 10: 137. doi: 10.1673/031.010.13701 [DOI] [PMC free article] [PubMed] [Google Scholar]
8.Dejean A, Lachaud J-P. Ecology and behavior of a seed-eating ponerine ant: Brachyponera senaarensis (Mayr). Insect Soc. 1994; 41: 191–210. [Google Scholar]
9.Kadochová Š, Frouz J. Thermoregulation strategies in ants in comparison to other social insects, with a focus on red wood ants (Formica rufa group). F1000Research. 2014; 2: 280. doi: 10.12688/f1000research.2-280.v2 [DOI] [PMC free article] [PubMed] [Google Scholar]
10.Elahi R. The effect of water on the ground nesting habits of the giant tropical ant, Paraponera clavata. J Insect Sci. 2005; 5: 34. doi: 10.1093/jis/5.1.34 [DOI] [PMC free article] [PubMed] [Google Scholar]
11.Ceusters R. Simulation du nid naturel des fourmis par des nids artificiels placés sur un gradient de température. Actes Coll Insect Soc. 1986; 3: 235–241. [Google Scholar]
12.Tschinkel WR. Sociometry and sociogenesis of colonies of the harvester ant, Pogonomyrmex badius: distribution of workers, brood and seeds within the nest in relation to colony size and season. Ecol Entomol. 1999; 24: 222–237. [Google Scholar]
13.Fresneau D, Corbara B, Lachaud J-P. Organisation sociale et structuration spatiale autour du couvain chez Pachycondyla apicalis. Actes Coll Insect Soc. 1989; 5: 83–92. [Google Scholar]
14.Tschinkel WR. The nest architecture of the Florida harvester ant, Pogonomyrmex badius. J Insect Sci. 2004; 4: 21. doi: 10.1093/jis/4.1.21 [DOI] [PMC free article] [PubMed] [Google Scholar]
15.Tschinkel WR. The nest architecture of the ant, Camponotus socius. J Insect Sci. 2005; 5: 9. doi: 10.1093/jis/5.1.9 [DOI] [PMC free article] [PubMed] [Google Scholar]
16.Moreira AA, Forti LC, Boaretto MAC, Andrade APP, Lopes JFS, Ramos VM. External and internal structure of Atta bisphaerica Forel (Hymenoptera: Formicidae) nests. J Appl Entomol. 2004; 128: 204–211. [Google Scholar]
17.Caldato N, Camargo RS, Forti LC, Andrade APP, Lopes JFS. Nest architecture in polydomous grass-cutting ants (Acromyrmex balzani). J Nat Hist. 2016; 50: 1561–1581. [Google Scholar]
18.Tschinkel WR. Ant Architecture: The Wonder, Beauty, and Science of Underground Nests. Princeton, New Jersey: Princeton University Press; 2021. [Google Scholar]
19.Pinter-Wollman N. Nest architecture shapes the collective behaviour of harvester ants. Biol Lett. 2015; 11: 20150695. doi: 10.1098/rsbl.2015.0695 [DOI] [PMC free article] [PubMed] [Google Scholar]
20.Antonialli-Junior WF, Giannotti E. Nest architecture and populations dynamics of the ponerine ant, Ectatomma opaciventre Roger (Hymenoptera: Formicidae). J Adv Zool. 1997; 18: 64–71. [Google Scholar]
21.Antonialli WF Jr, Giannotti E. Nest architecture and population dynamics of the ponerine ant Ectatomma edentatum (Hymenoptera, Formicidae). Sociobiology 2001; 38: 475–486. [Google Scholar]
22.Antonialli-Junior WF, Tofolo VC, Giannotti E. Population dynamics of Ectatomma planidens (Hymenoptera: Formicidae) under laboratory conditions. Sociobiology. 2007; 50: 1005–1013. [Google Scholar]
23.Lapola DM, Antonialli Júnior WF, Giannotti E. Arquitetura de ninhos da formiga neotropical Ectatomma brunneum F. Smith, 1858 (Formicidae: Ponerinae) em ambientes alterados. Rev Bras Zoo. 2003; 5: 177–188. [Google Scholar]
24.Vieira AS, Antonialli Junior WF. Populational fluctuation and nest architecture of Ectatomma brunneum (Hymenoptera, Formicidae) in remaining areas of pasture, Dourados- MS, Brazil. Sociobiology. 2006; 47: 275–287. [Google Scholar]
25.Vieira AS, Antonialli-Junior WF, Fernandes WD. Modelo arquitetônico de ninhos da formiga Ectatomma vizottoi Almeida (Hymenoptera, Formicidae). Rev Bras Entomol. 2007; 51: 489–493. [Google Scholar]
26.Weber NA. Two common ponerine ants of possible economic significance, Ectatomma tuberculatum (Olivier) and E. ruidum Roger. Proc Entomol Soc Washington. 1946; 48: 1–16. [Google Scholar]
27.Lachaud J-P, López Méndez JA, Schatz B, De Carli P, Beugnon G. Comparaison de l’impact de prédation de deux ponérines du genre Ectatomma dans un agroécosystème néotropical. Actes Coll Insect Soc. 1996; 10: 67–74. [Google Scholar]
28.Lachaud J-P. Ectatomma. pp. 358–365. In: Starr C (ed) Encyclopedia of Social Insects. Cham: Springer; 2019. 10.1007/978-3-319-90306-4_41-1. [DOI] [Google Scholar]
29.Delabie JC. The ant problems of cocoa farms in Brazil. pp. 555–569. In: Vander Meer RK, Jaffe K, Cedeno A (eds) Applied myrmecology: A world perspective. Boulder, Colorado, USA: Westview Press; 1990. [Google Scholar]
30.Lachaud J-P. Foraging activity and diet in some Neotropical ponerine ants. I. Ectatomma ruidum Roger (Hymenoptera, Formicidae). Folia Entomol Mex. 1990; 78: 241–256. [Google Scholar]
31.Aguilar-Velasco RG, Poteaux C, Meza-Lázaro R, Lachaud J-P, Dubovikoff D, Zaldívar-Riverón A. Uncovering species boundaries in the Neotropical ant complex Ectatomma ruidum (Ectatomminae) under the presence of nuclear mitochondrial paralogues. Zool J Linn Soc. 2016; 178: 226–240. doi: 10.1111/zoj.12407 [DOI] [Google Scholar]
32.Meza-Lázaro RN, Poteaux C, Bayona-Vásquez NJ, Branstetter MG, Zaldívar-Riverón A. Extensive mitochondrial heteroplasmy in the neotropical ants of the Ectatomma ruidum complex (Formicidae: Ectatomminae). Mitochondrial DNA A. 2018; 29: 1203–1214. doi: 10.1080/24701394.2018.1431228 [DOI] [PubMed] [Google Scholar]
33.Peña-Carrillo KI, Poteaux C, Leroy C, Meza-Lazáro RN, Lachaud J-P, Zaldívar-Riverón A, et al. Highly divergent cuticular hydrocarbon profiles in the cleptobiotic ants of the Ectatomma ruidum species complex. Chemoecology. 2021; 31: 125–135. [Google Scholar]
34.Peña Carrillo KI, Lorenzi MC, Brault M, Devienne P, Lachaud J-P, Pavan G, et al. A new putative species in the Ectatomma ruidum complex (Formicidae: Ectatomminae) produces a species-specific distress call. Bioacoustics. In press. doi: 10.1080/09524622.2021.1938226 [DOI] [Google Scholar]
35.Arias-Penna TM. Subfamilia Ectatomminae. pp. 53–107. In: Jiménez E, Fernández F, Arias TM, Lozano-Zambrano FH (Eds). Sistemática, biogeografía y conservación de las hormigas cazadoras de Colombia. Bogotá, Colombia: Instituto de Investigaciones de Recursos Biológicos Alexander von Humboldt; 2008. [Google Scholar]
36.Dáttilo W, Vásquez-Bolaños M, Ahuatzin DA, Antoniazzi R, Chávez-González E, Corro E, et al. Mexico ants: incidence and abundance along the Nearctic-Neotropical interface. Ecology. 2020; 101: e02944. doi: 10.1002/ecy.2944 [DOI] [PubMed] [Google Scholar]
37.Passera L, Lachaud J-P, Gomel L. Individual food source fidelity in the neotropical ponerine ant Ectatomma ruidum Roger (Hymenoptera Formicidae). Ethol Ecol Evol. 1994; 6: 13–21. [Google Scholar]
38.Perfecto I. Indirect and direct effects in a tropical agroecosystem: the maize-pest-ant system in Nicaragua. Ecology. 1990; 71: 2125–2134. [Google Scholar]
39.Ibarra-Núñez G, García JA, López JA, Lachaud J-P. Prey analysis in the diet of some ponerine ants (Hymenoptera: Formicidae) and web-building spiders (Araneae) in coffee plantations in Chiapas, Mexico. Sociobiology. 2001; 37: 723–755. [Google Scholar]
40.Lachaud J-P, Fresneau D, García-Pérez J. Étude des stratégies d’approvisionnement chez 3 espèces de fourmis ponérines (Hymenoptera, Formicidae). Folia Entomol. Mex. 1984; 61: 159–177. [Google Scholar]
41.Santamaría C, Armbrecht I, Lachaud J-P. Nest distribution and food preferences of Ectatomma ruidum (Hymenoptera: Formicidae) in shaded and open cattle pastures of Colombia. Sociobiology. 2009; 53: 517–541. [Google Scholar]
42.Breed MD, Abel P, Bleuze TJ, Denton SE. Thievery, home ranges, and nestmate recognition in Ectatomma ruidum. Oecologia. 1990; 84: 117–121. doi: 10.1007/BF00665604 [DOI] [PubMed] [Google Scholar]
43.Schatz B, Lachaud J-P. Effect of high nest density on spatial relationships in two dominant ectatommine ants (Hymenoptera: Formicidae). Sociobiology. 2008; 51: 623–643. [Google Scholar]
44.De Carli P, Lachaud J-P, Beugnon G, López-Méndez JA. Études en milieu naturel du comportement de cleptobiose chez la fourmi néotropicale Ectatomma ruidum (Hymenoptera, Ponerinae). Actes Coll Insect Soc. 1998; 11: 29–32. [Google Scholar]
45.Guénard B, McGlynn TP. Intraspecific thievery in the ant Ectatomma ruidum is mediated by food availability. Biotropica. 2013; 45: 497–502. [Google Scholar]
46.De Carli P. Interactions intraspécifiques chez une fourmi néotropicale: Ectatomma ruidum Roger (Hymenoptera, Ponerinae). PhD Thesis, University Paul Sabatier, Toulouse; 1997.
47.Quevedo Vega CJ. Interacciones competitivas y variabilidad en las estrategias de nidificación de Ectatomma ruidum (Formicidae: Ectatomminae). Trabajo de Grado. Universidad del Valle, Cali; 2015. [Google Scholar]
48.Berrod L. Étude de la polydomie chez la fourmi Ectatomma ruidum Roger (Hymenoptera, Formicidae). M. Sci. Thesis, Université Paris 13; 2017.
49.Santamaría C. Interacciones entre nidos de Ectatomma ruidum, ¿polidomia o cleptobiosis? Bol Mus Entomol Univ Valle. 2017; 18 (Supl. 1): 12. [Google Scholar]
50.CVC-CIAT-DAGMA. Identificación de Zonas y Formulación de Propuestas para el Tratamiento de Islas de Calor, Municipio de Santiago de Cali. Convenio CVC–CIAT–DAGMA No. 110 de 2015 Informe Técnico. p. 22; 2015.
51.Tschinkel WR. Methods for casting subterranean ant nests. J Insect Sci. 2010; 10: 88. doi: 10.1673/031.010.8801 [DOI] [PMC free article] [PubMed] [Google Scholar]
52.Tschinkel WR. A method for using ice to construct subterranean ant nests (Hymenoptera: Formicidae) and other soil cavities. Myrmecol News. 2013; 18: 99–102. [Google Scholar]
53.Forti LC, Moreira AA, Camargo RS, Caldato N, Castellani MA. Nest architecture development of grass-cutting ants. Rev Bras Entomol. 2018; 62: 46–50. [Google Scholar]
54.Toffin E, Di Paolo D, Campo A, Detrain C, Deneubourg J-L. Shape transition during nest digging in ants. Proc Nat Acad Sci USA 2009; 106: 18616–18620. doi: 10.1073/pnas.0902685106 [DOI] [PMC free article] [PubMed] [Google Scholar]
55.Pardo-Lorcano LC, Montoya J, Bellotti AC, van Schoonhoven A. Structure and composition of the white grub complex (Coleoptera: Scarabaeidae) in agroecological systems of northern Cauca, Colombia. Fla Entomol. 2005; 88: 355–362. [Google Scholar]
56.R Development Core Team. 2020. R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. URL https://www.R-project.org/. [Google Scholar]
57.Santamaría CA, Domínguez-Haydar Y, Armbrecht I. Cambios en la distribución de nidos y abundancia de la hormiga Ectatomma ruidum (Roger 1861) en dos zonas de Colombia. Bol Mus Entomol Univ Valle. 2009; 10(2): 10–18. [Google Scholar]
58.Lachaud J-P, Pérez-Lachaud G. Impact of natural parasitism by two eucharitid wasps on a potential biocontrol agent ant in southeastern Mexico. Biol Control. 2009; 48: 92–99. [Google Scholar]
59.McGlynn TP. The ecology of nest movement in social insects. Annu Rev Entomol. 2012; 57: 291–308. doi: 10.1146/annurev-ento-120710-100708 [DOI] [PubMed] [Google Scholar]
60.Tschinkel WR. Nest relocation and excavation in the Florida harvester ant, Pogonomyrmex badius. PLoS ONE. 2014; 9: e112981. doi: 10.1371/journal.pone.0112981 [DOI] [PMC free article] [PubMed] [Google Scholar]
61.Rocha FH, Lachaud J-P, Hénaut Y, Pozo C, Pérez-Lachaud G. Nest site selection during colony relocation in Yucatan Peninsula populations of the ponerine ants Neoponera villosa (Hymenoptera: Formicidae). Insects. 2020; 11: 200. [DOI] [PMC free article] [PubMed] [Google Scholar]
62.Poteaux C, Prada-Achiardi FC, Fernández F, Lachaud J-P. Diversidade genética e fenotípica no gênero Ectatomma. pp. 127–144. In: Delabie JHC, Feitosa RM, Serrão JE, Mariano CSF, Majer JD (Eds). As formigas poneromorfas do Brasil. Ilhéus: Editus; 2015. [Google Scholar]
63.Vásquez-Ordóñez AA, Armbrecht I, Pérez-Lachaud G. Effect of habitat type on parasitism of Ectatomma ruidum by eucharitid wasps. Psyche. 2012; Article ID 170483. [Google Scholar]
64.Pérez-Lachaud G, Klompen H, Poteaux C, Santamaría C, Armbrecht I, Beugnon G, et al. Context dependent life-history shift in Macrodinychus sellnicki mites attacking a native ant host in Colombia. Sci Rep. 2019; 9: 8394. doi: 10.1038/s41598-019-44791-2 [DOI] [PMC free article] [PubMed] [Google Scholar]
65.Schatz B, Lachaud J-P, Fourcassié V, Beugnon G. Densité et distribution des nids chez la fourmi Ectatomma ruidum Roger (Hymenoptera; Formicidae; Ponerinae). Actes Coll Insect Soc. 1998; 11: 103–107. [Google Scholar]
66.Wheeler WM. Courtship of the Calobatas. The kelep ant and the courtship of its mimic, Cardiacephala myrmex. J Hered. 1924; 25: 485–495. [Google Scholar]
67.Wheeler WM. The fungus-growing ants of North America. Bull Am Mus Nat Hist. 1907; 23: 669–807. [Google Scholar]
68.Bruch C. Contribución al estudio de las hormigas de la provincia de San Luis. Rev Mus La Plata. 1916; 23: 291–357. [Google Scholar]
69.Halfen AF, Hasiotis ST. Neoichnological study of the traces and burrowing behaviors of the western harvester ant Pogonomyrmex occidentalis (Insecta: Hymenoptera: Formicidae): Paleopedogenic and paleoecological implications. Palaios. 2010; 25: 703–720. [Google Scholar]
70.Noirot C, Darlington JPEC. Termite nests: architecture, regulation and defence. pp. 121–139. In: Abe Y, Bignell DE, Higashi T (eds) Termites: Evolution, Sociality, Symbioses, Ecology. Dordrecht, The Netherlands: Springer; 2000. doi: 10.1046/j.1365-2222.2000.00751.x [DOI] [Google Scholar]
71.Wang D, McSweeney K, Lowery B, Norman JM. 1995. Nest structure of ant Lasius neoniger Emery and its implications to soil modification. Geoderma. 1995; 66: 259–272. [Google Scholar]
72.Le Masne G. Observations sur les relations entre le couvain et les adultes chez les fourmis. Ann Sc Nat Zool. 1953; 15: 1–56. [Google Scholar]
73.Dejean A, Lachaud J-P. Polyethism in the ponerine ant Odontomachus troglodytes: interaction of age and interindividual variability. Sociobiology. 1991; 18: 177–196. [Google Scholar]
74.Cassill D, Tschinkel WR, Vinson SB. Nest complexity, group size and brood rearing in the fire ant, Solenopsis invicta. Insect Soc. 2002; 49: 158–163. [Google Scholar]
75.Lachaud J-P, Cadena A, Pérez-Lachaud G, Schatz B. Polygynie et stratégies reproductives chez une ponérine néotropicale, Ectatomma ruidum. Actes Coll Insect Soc. 1999; 12: 53–59. [Google Scholar]
76.Lachaud J-P, Cadena A, Schatz B, Pérez-Lachaud G, Ibarra-Núñez G. Queen dimorphism and reproductive capacity in the ponerine ant, Ectatomma ruidum Roger. Oecologia. 1999; 120: 515–523. doi: 10.1007/s004420050885 [DOI] [PubMed] [Google Scholar]
77.Cadena A, Pérez-Lachaud G, Schatz B, Lachaud J-P. Inhibition de la ponte dans les sociétés polygynes de Ectatomma ruidum (Hymenoptera, Formicidae, Ponerinae). Actes Coll Insect Soc. 2001; 14: 87–93. [Google Scholar]
78.Lenoir J-C, Lachaud J-P, Nettel A, Fresneau D, Poteaux C. The role of microgynes in the reproductive strategy of the neotropical ant Ectatomma ruidum. Naturwissenschaften. 2011; 98: 347–356. doi: 10.1007/s00114-011-0774-3 [DOI] [PubMed] [Google Scholar]
79.Fernández F. Las hormigas cazadoras del género Ectatomma (Formicidae: Ponerinae) en Colombia. Caldasia. 1991; 16: 551–564. [Google Scholar]
80.Debout G, Schatz B, Elias M, McKey D. Polydomy in ants: what we know, what we think we know, and what remains to be done. Biol J Linn Soc. 2007; 90: 319–348. [Google Scholar]
81.Cerdá X, Dahbi A, Retana J. Spatial patterns, temporal variability, and the role of multi‐nest colonies in a monogynous Spanish desert ant. Ecol Entomol. 2002; 27: 7–15. doi: 10.1046/j.0307-6946.2001.00386.x [DOI] [Google Scholar]
82.Anderson C, McShea DW. Individual versus social complexity, with particular reference to ant colonies. Biol Rev. 2001; 76: 211–237. [DOI] [PubMed] [Google Scholar]

PLoS One. doi: 10.1371/journal.pone.0263382.r001

Decision Letter 0

Maykon Passos Cristiano

7 Jul 2021

PONE-D-21-13547

Nest architecture and colony composition in two populations of Ectatomma ruidum sp. 2 (E. ruidum species complex) in southwestern Colombia

PLOS ONE

Dear Dr. Lachaud,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

As can you see below, your paper was revised by four reviewers. After a careful reading of the manuscript, and the reviewers’ suggestions, my decision is a major revision of your paper. I recommend that you do a thorough review of English, and answer all the reviewers’ questions in detail. (Note that reviewer 1 has included an attachment with their comments)

Please, I would like you to know that the final acceptance of your manuscript will depend on the quality of the review of your manuscript and the responses to the reviewers' comments. Please let me know if you have any questions.

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Maykon Passos Cristiano, D. Sc.

Academic Editor

PLOS ONE

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Partly

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: Partly

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: No

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: I Don't Know

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3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: No

Reviewer #3: Yes

Reviewer #4: Yes

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4. Is the manuscript presented in an intelligible fashion and written in standard English?

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Reviewer #1: No

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: Yes

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: General comment

The paper brings information about the nest architecture of an ant species of economic importance in Colombia, which are relevant to this research field. However, the writing is very confusing and the applied analyses and their interpretation are very poor. It is necessary to reanalyze and rewrite the text. The discussion must be more reliant on your own results, instead of only existing literature.

Abstract

This section lacks an introduction with the theorical background that justifies your study. Also, you say in this section that you have strong correlations between the variables, but any correlation is near 90%. The conclusion here is much better than what is presented at the end of the discussion, but you need to write and present your data and analyses in a way that you can make the readers agree with you.

Introduction

The second and third paragraph seem like a review and up to there I can not know what is the point of your study. And even with all these information, the importance/justificative of knowing the relation between nest architecture and population for these ant species is not presented.

Figure 1A is really very beautiful, but it does not illustrate the “high bioturbation impact during nest excavation” as is called in the text. The same is true for the figure caption “nest excavation”. What I see is an ant transporting a pellet of soil (?) with its mandibles. The same goes for the other photos of Figure 1. What do you want to show with these photos? The figure 1 is once again called for the images B, C and D at material and methods (line 151), but I still cannot see why the feeding habits are relevant to your study.

The most important justificative of your study is presented only after line 110, which is related to question: Are the nests monodomous or polidomous? On my point of view this is the main justificative of your study. I recommend you to shorten the text before this point and highlight this issue.

In the last paragraph, you first presented two objectives:

• to evaluate the spatio-temporal competitive relationships of their nests

• to validate, or not, the existence of a possible polydomy.

Material and Methods

Line 163-164. Why did you sample the nests in 2 different seasons? Furthermore, why did you choose these seasons? Please, justify.

Line 165. How did you mark the nests?

Line 166-170. You report that from 188 nests, 15 were not used as data due their small population. Following, you state that you molded 24 nests. What happened to the others? Please explain.

Line 179. Change “nests” for “chambers”.

Line 188-189. Why were the nests from Vereda El Rosal not molded?

Line 193. What exactly did you mean with chamber size? Chamber area? Chamber volume? Size is too vague. Please be more specific about what kind of data you analyzed.

Line 193-194. “Student-t tests were performed to compare whether the presence or absence of queens had any effect …” Effect of what over what?

Results

In general, the applied statistical analyses and specially their interpretations are not adequate (see detailed comments below). I strongly suggest that instead of doing a lot of paired correlations, you consider applying a multivariate analysis, in which you can verify which variables were associated to the similarities and dissimilarities between the nests. Even the locale can be incorporated in the multivariate analysis, making your result more robust. This way you can examine several variables (population parameters) to see if one or more of them are predictive of a certain outcome, in this case the nest architecture.

Line 242. “The tunnels walls and the floors of the chambers were lined with a very compact and thin surface …” This is very confusing to read and understand, please review the English writing.

Line 245-246. The negative correlation between chamber volume, not size, and depth does not mean that superficial chambers are larger. Instead, the analysis indicates that as the chamber was deeper, its volume was smaller. Also, the R value (-0.62) is too small. Please interpret the analysis according to the results it gives to you.

Lines 246-250. What is the MLGM analysis? It was not described in material and methods. Also, which chambers did you consider as the upper ones? The third chamber is not one of these upper chambers. Once again you can not say that the 3rd chamber was smaller than the 2nd or the 1st, as you did not apply any statistical test.

At Table 2, what does “nb” mean after the word worker or larvae? Here there is another statistical problem. Queen presence and population should not be analyzed with a linear regression, but instead with a logistic one, as presence/absence of the queen is a binomial variable.

Discussion

Just like the introduction section, the text is too long. The ideas are not well coordinated. Also, I can not find the answers to the proposed questions addressed at the end of the introduction. Especially in relation to the status of the species’ polidomy or monodomy. You suggested at the last line that they were probably monodomous, based in the fact that there are queenless nests. However, you did not find horizontal connecting tunnels among nests or any evidence of external communication. Thus, in which evidences is your answer based on? I recommend that while restructuring this section, you follow your proposed questions.

Reviewer #2: In this very interesting study authors have investigated the nest structure, colony composition and the overlap between these features in Ectatomma ruidum sp. Combining excavation with paraffin casts authors have studied a large number of colonies across two different populations at two different time points in Southwest Colombia. Having read the manuscript with enthusiasm as there are so few studies regarding this aspect and this part of the world, I have the following suggestions to improve the analysis and presentation.

• Lines 141 to 151 needs to be moved away from the methods. This is background information about the study species and not related to how this study was performed. Further, the images mentioned are also not particularly relevant and the version with the current manuscript is not of sufficient resolution. As the current study is about nest structure and not the food or foraging of these ants its best to replace these images. An image of the nest entrance, image of the wax cast embedded in its natural habitat before the extraction and one image of the model organism would complement this manuscript in a better manner.

• Line 180 – Mentions that the different parameters of the nest was measured. How exactly was this performed? The tunnel and chamber would be hard to distinguish from each other. How do the authors understand which part of the nest is a chamber and which part is simply a blind extension of the tunnel or the tunnel itself? While the images of the wax cast indicate that the first couple of chambers are clear, how do the authors delineate the other chambers and measure the irregular structures. Other researchers have performed this in a quantitative manner for example see Bhattacharyya & Annagiri 2019.

• The organization of the results section needs to be improved. Abundance, Architecture, Relationships between the architectural elements and Relationship between colony composition and architectural elements are some of the sub-headings one can consider. Currently some results have a sub headings others do not, also “global set of nests” (line 252 ) is not a particularly meaningful sub heading.

• Also, it would be useful if the authors end the nest architecture section with an overview of an average nest for this species in its natural habitat features across all the parameters examined.

• Were there any changes across the seasons in the architecture?

I have read your manuscript carefully and I believe it is an interesting contribution. In overall the manuscript is reasonable; it is well written, the ideas are clearly presented, but I think that the figures and tables would be improved.

Specifically, I would recommend using the name of the species and explain that it could comprise a species complex, removing the sp. 2 from the text.

The limitations due the differences in sample size need to be addressed and better highlighted for readers.

Further, the discussion could be better explored if information and comparison with other species of taxa were considered in the discussion see the reference above as example.

I believe that these points must be addressed before it is ready to be published in Plos One.

Since the authors used the wax-casting method that recovers all nest contents in place, why do they report these data in such crude form in the main text (+, ++, +++, etc)? They report actual numbers as supplementary material, and do so by chamber, but under analyze these data in the main body of the paper. Most ants sort brood by stage, depth, conditions, etc. Indicative of the failure to see the importance of such details is line 255 where the authors refer to the correlations between worker numbers, pupae, larvae etc. as "very trivial." Rather than being trivial, they describe both the temporal and colony-level life of the colony and its success. The number of pupa in a colony is a measure of the current birth rate, the worker-larva ratio is a measure of efficiency, both predict the current growth rate. The density of workers is potentially an important social measure. If callows can be recognized, then this gives a crude measure of the age-structure of the nest population. I see these and many more as lost opportunities.

While there is a comparison between collection sites, these confound season with site. The authors report site differences in the nest depth, the number of workers and brood, as well as in the rate of queenrightness. To what degree are differences the result of differences in season, site or both? Among the most interesting are differences in queen number. The predominance of queenless nests indicates that this species is polydomous, but polydomy can be seasonal as well as related to colony size. Some ant species rear sexuals in either the presence or absence of queens. I think these data can tell us something about the annual cycle of this species. The high nest density is probably also relevant to polydomy. What was the spacing between nests like? Was there worker traffic between them?

Some other points: Line 44 citations on bioturbation should include papers by Tschinkel on Pogonomyrmex and Trachymyrmex bioturbation. Then, after introducing bioturbation as a subject, the authors do not discuss how Ectotomma contributes to bioturbation in its habitat. Since they have data on nest volumes and their rates of abandonment and new appearance, they could conceivably comment on bioturbation.

Line 71-2, Tschinkel provided such data for several other species as well, and never made any claims about plant roots (Line 75). The authors might find his recently published book on Ant Architecture helpful. I think the Introduction needs to be briefer and more focused, and that is true for the discussion too.

I think this could be made into a paper that reveals much more about the biology of this ant than it currently does. I hope the authors will succeed at doing this.

**********

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Reviewer #1: No

Reviewer #2: No

Reviewer #3: No

Reviewer #4: No

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Attachment

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PLoS One. 2022 Feb 2;17(2):e0263382. doi: 10.1371/journal.pone.0263382.r002

Author response to Decision Letter 0

19 Sep 2021

Reviewer #1: General comment

R: Please, see our answers point-by-point below.

Abstract

This section lacks an introduction with the theorical background that justifies your study. R: This was added in the revised version (see lines 17-20).

Also, you say in this section that you have strong correlations between the variables, but any correlation is near 90% R: We don’t really understand what the problem is that the reviewer raised. Probably because our cast nest sample size was high enough, the fact is that the correlations we are presenting are significant even for relatively small R-values and that is what we are reporting.

The conclusion here is much better than what is presented at the end of the discussion, but you need to write and present your data and analyses in a way that you can make the readers agree with you R: We tried to focus the revised discussion more directly on our own results and to present more convincing arguments.

Introduction

The text of this section is too long and takes too long to approach the issue of the study. For example, the first paragraph has 27 lines and addresses different points concerning the nest architecture, such as how the construction material interferes with internal temperature, strategies to avoid flooding and also thermal preferences of individuals inside the nest. These issues are presented without any cohesion, making the text awkward. Also, the English needs improvement. R: We agree with the reviewer and have considerably reduced this first paragraph, removing a number of details that made the text cumbersome. We hope that now the sequence of arguments is easier to follow. On the other hand, with regard to the English, as noted in the acknowledgements and as has been our practice for the past seven years, this manuscript has been checked by an English-speaking colleague, Julian Flavell, whose quality of expression in his own language has so far never been questioned.

The second and third paragraph seem like a review and up to there I can not know what is the point of your study. R: The reviewer is right. The second paragraph and the first two sentences of the third paragraph have been removed to get more directly to the presentation of the issue of our study.

And even with all these information, the importance/justificative of knowing the relation between nest architecture and population for these ant species is not presented. R: We have added a sentence to introduce this topic just before addressing the architecture of the nests in the genus Ectatomma (see lines 57-59 in the revised version).

In the last paragraph, you first presented two objectives:

• to evaluate the spatio-temporal competitive relationships of their nests

• to validate, or not, the existence of a possible polydomy.

Following, you presented as objective what actually is your methodology. And then you presented some questions. The first one I can not understand at all. Please clarify. The others seem unrelated with your proposed objectives (listed above). Please clarify how answering these questions can help you reach your objective. R: We agree with the reviewer that this paragraph lacked clarity and that there was some confusion and redundancy in the questions asked. We have therefore modified this paragraph by making it clearer (at least we hope so) which parameters were recorded and which questions were asked, avoiding redundancy (see lines 92-102 in the revised version).

Material and Methods

Line 163-164. Why did you sample the nests in 2 different seasons? Furthermore, why did you choose these seasons? Please, justify. R: Because in our manuscript we didn’t really analyze the effects of seasonality on nest architecture, and because seasonality is only marginally addressed when we talk about nest relocation, we decided to avoid mentioning seasons in this paragraph. However, we left the indication of the months in which the number of nest entrances were recorded and specified that, theoretically, the two sampling periods chosen were supposed to be during the dry season, although, beyond our control, the climatic conditions were not respected since unusual rainfall for this period were recorded in January 2017 (see lines 121-124 of the revised version).

Line 165. How did you mark the nests? R: Thanks for the comment; this is now specified in the revised version (see lines 124-128). Nests were marked with flags and GPS and mapped with grids in the field. Subsequently, to avoid problems associated with the loss of flags, they were marked with plastic bottle caps, buried in the ground next to the nest opening.

Line 166-170. You report that from 188 nests, 15 were not used as data due their small population. Following, you state that you molded 24 nests. What happened to the others? Please explain. R: It was not possible to cast all nests for logistical reasons. Furthermore, we consider 24 randomly chosen nests to be a representative sample of the population, and it should be noted that this sample size is similar or even larger than those typically used in this type of research. Finally, we had clearly stated, in lines 144-145 of the previous version before discussing the 24 nests that were used to make the casts, that: "For each nest, the number of chambers and the total nest depth were recorded". This information collected from the 79 nests on the University Campus in Cali that were not wax cast has been used in combination with that obtained for the 24 cast nests to calculate average values for the number of chambers and nest depth at the population level in ‘Cali’ (the complete data are presented in Table S2). In fact, as specified on line 143 of the previous version of our manuscript, 118 nests were extracted at ‘Cali’ (including the 15 incomplete ones), not 188 as reported by the reviewer.

Line 179. Change “nests” for “chambers”. R: Here, we are actually talking about "nests", not "chambers".

Line 188-189. Why were the nests from Vereda El Rosal not molded? R: Besides the fact that this technique takes a lot of time, the reason we didn’t cast the nests in Vereda El Rosal is that the coffee plots owners didn’t authorize pouring wax on their land, since these plots were productive and they feared that we would burn their soil. The difference with the University Campus is that, in this case, it was an experimental field and we were able to get the permits easily.

Line 193. What exactly did you mean with chamber size? Chamber area? Chamber volume? Size is too vague. Please be more specific about what kind of data you analyzed. R: We specified in the revised version (see lines 26, 94 and 149) that the parameter taken into account was the volume and we changed 'chamber size' by 'chamber volume' everywhere in the text where it was necessary.

Line 193-194. “Student-t tests were performed to compare whether the presence or absence of queens had any effect ...” Effect of what over what? R: Student-t tests were performed to compare whether the presence or absence of queens had any effect on the physical and populational characteristics of the nests. Given that we re-analyzed our data using a Binomial Generalized Linear Model, we changed this part of the “Data analysis” in the Material and Methods section (see lines 168-183 in the revised version).

Also, in the section Data Analysis you must tell the readers which was your random variable in the GLMM, which program and packages of statistical analyses you used. There are a lot of information that are lacking in this section. R: As noted in our previous response just above, we made changes in the “Data analysis” of the Material and Methods section of our revised version and provided the missing information.

Results

Line 242. “The tunnels walls and the floors of the chambers were lined with a very compact and thin surface ...” This is very confusing to read and understand, please review the English writing. R: We are sorry, but we don’t understand what was not understandable in this sentence which, by the way, had already been checked by an English-speaking colleague, Julian Flavell. We are referring here to the inner lining of the chambers and tunnels which was very compact and smooth in appearance. We have only slightly modified the sentence to make it clearer (see lines 236-237 in the revised version). Such internal lining of chamber and tunnel walls with inorganic material has rarely been described in detail but is known in various soil-dwelling ants and termites. This is now specified and developed in the discussion of the revised version (see lines 375-383).

Line 245-246. The negative correlation between chamber volume, not size, and depth does not mean that superficial chambers are larger. Instead, the analysis indicates that as the chamber was deeper, its volume was smaller. R: To avoid confusion, we changed the formulation to: ‘the deeper the chamber, the smaller its volume’ and provide a new figure (Fig. 3 in the revised version) supporting this result (see lines 238-241).

Also, the R value (-0.62) is too small. Please interpret the analysis according to the results it gives to you. R: We didn’t do anything else. Because of the large sample size of cast nests, the number of pairs compared (chamber volume vs. chamber depth) was hight (n = 148). As a consequence, although the R-value was small it was statistically highly significant (p < 0.001). We therefore concluded that there was a significant negative relationship beyond mere chance.

Lines 246-250. What is the MLGM analysis? It was not described in material and methods. R: We thank the reviewer for highlighting this error. The correct abbreviation was 'GLMM', which was described in the Material and Methods section. However, this remark is no longer relevant because this part has been modified in the new version using different methods of analysis (see "Data Analysis" in the Material and Methods section of the revised version).

Also, which chambers did you consider as the upper ones? R: We now specify that we consider the three first chambers, closest to the surface, as the upper ones (see line 245 in the revised version).

The third chamber is not one of these upper chambers. R: In fact, that’s just the case! As the mean depth of the 24 cast nests was 29.1 ± 0.8 cm (see Table S1) and the mean depth of the third chamber was 14.2 ± 0.7 cm (see Table 1), the third chamber was indeed one of the upper ones, located in the upper half of the nests, closest to the surface.

Once again you can not say that the 3rd chamber was smaller than the 2nd or the 1st, as you did not apply any statistical test. R: We have rewritten this section and explained why a statistical test couldn’t be performed (see lines 244-250 in the revised version).

At Table 2, what does “nb” mean after the word worker or larvae? R: “nb” used to mean “number”, but this remark is no longer relevant because both Tables 2 and 3 presented in the previous version have now been removed.

Here there is another statistical problem. Queen presence and population should not be analyzed with a linear regression, but instead with a logistic one, as presence/absence of the queen is a binomial variable. R: We hope that with the new analysis (Binomial GLM) this problem is now fixed (see lines: 171-177 in the new version).

Discussion

Just like the introduction section, the text is too long. The ideas are not well coordinated. Also, I can not find the answers to the proposed questions addressed at the end of the introduction. R: Changes have been made in the discussion and several additional details have been provided to explain our results and hypothesis. Consequently, the discussion was not really shortened, but we hope that, at least, it is now clearer.

Especially in relation to the status of the species’ polidomy or monodomy. You suggested at the last line that they were probably monodomous, based in the fact that there are queenless nests. However, you did not find horizontal connecting tunnels among nests or any evidence of external communication. Thus, in which evidences is your answer based on? R: We suspect there was some confusion here between what is considered as ‘polydomy’ and ‘unicoloniality’. In the new version of the manuscript, we have made various changes and dedicated a special section of the discussion to present our evidences and hypothesis concerning the polydomic stucture observed in our Colombian populations (see lines 417-467).

I recommend that while restructuring this section, you follow your proposed questions.

• Introduction is well written and sets the stage for the questions is a nice manner. The one improvement required is the usage of certain terms. Abstract and introduction has certain terms like “monodomic” which researchers with a social insect background can understand, but for readers of this journal it would be useful if authors include the definition of these terms when it is used for the first time. I really like how line 31 reads, but if the meaning comes across to a non- specialist reader remains a question. R: Due to space limitations, we were unable to include the definitions of the terms "monodomic" and "polydomic" in the abstract, but we now provide a brief definition of these terms in the revised version when they are first used in the introduction (see lines 81 and 91).

• Lines 141 to 151 needs to be moved away from the methods. This is background information about the study species and not related to how this study was performed. R: Insofar as we had to significantly reduce our introduction to address the criticisms raised by reviewer #1 and get more directly to the presentation of our study problem, moving this paragraph into the introduction was somewhat counterproductive. However, we took into consideration the reviewer's suggestion and did so (see lines 68-78).

Further, the images mentioned are also not particularly relevant and the version with the current manuscript is not of sufficient resolution. As the current study is about nest structure and not the food or foraging of these ants its best to replace these images. R: We agree that this figure was not really relevant for our study as noted also by Reviewer #1. It has been removed.

An image of the nest entrance, image of the wax cast embedded in its natural habitat before the extraction and one image of the model organism would complement this manuscript in a better manner. R: We have attempted to address this comment by composing a new figure (Figure 1) that shows: 1) the collecting area at ‘Cali’, 2) the wax cast of a nest embedded in its natural habitat prior to extraction, and 3) the same nest once cleared of its earthy gangue.

• Line 180 – Mentions that the different parameters of the nest was measured. How exactly was this performed? R: Measurements were made with a millimeter ruler. This precision has been added within the text (see line 149).

The tunnel and chamber would be hard to distinguish from each other. R: In fact, the distinction between tunnel and chamber was less complicated than it seems because the two structures were clearly different: the chambers were horizontal to the ground whereas the tunnel was rather vertical and clearly elongated. We hope that the new Figure 1 will help the reader to distinguish the tunnel from the chambers. We think that if there was any confusion, it was extremely small and that the error was negligible. Chamber height was measured from the point where the tunnel that leads to it widens. Furthermore, because the same criterion was always used by the same researcher (CS), we are confident that the information is reliable. This information has been summarized and added to the revised version when describing the wax cast extraction (see lines 141-147).

How do the authors understand which part of the nest is a chamber and which part is simply a blind extension of the tunnel or the tunnel itself? While the images of the wax cast indicate that the first couple of chambers are clear, how do the authors delineate the other chambers and measure the irregular structures. Other researchers have performed this in a quantitative manner for example see Bhattacharyya & Annagiri 2019. R: Given it can sometimes be tricky to define, without ambiguity, where exactly a chamber started, we used the geometric shape of the tunnel or the chamber to determine the morphological transition of the structure and define their starting (or ending) point. In this way, the point where the tunnel begins to widen, and the wax begins to form an oval or circular shape was defined as a chamber. This is now explained in the revised version (see lines 141-147).

• Lines 184 - Authors need to think critically if this second population of ants is really adding to the over all view of the manuscript. Getting in complete information for part of the time from 49 nests, may just be adding variation to the data without the benefit of enhancing the information about the species. I can understand that a lot of effort has gone into collecting this data and the authors can consider using this data at a later date with complete information. R: We thank the reviewer for this suggestion, but we strongly believe that the information from the second study site (Vereda El Rosal) actually helps to strengthen the evidence we provide against our objectives. Indeed, the comparison of the average nest depth between the two studied areas and with the nests observed in Mexico, along with the significant difference in the proportion of queenright nests between ‘Cali’ and ‘Cauca’ that suggests a decrease in the expression of polydomy when nest depth increases, is essential for the hypothesis we proposed on the role of the queen's inhibitory control as a factor triggering polydomy (see lines 408-468 in the revised version). Therefore, we chose to retain these data.

• Lines 199: Can the abundance be reported per unit area and how this changed within each grid over time. From what is reported here we can only get a very rough idea. This kind of information would be very useful if it is done in a systematic manner. R: Because we didn’t initially plan to compare nest density or relocation over time and we only have two points recorded at different times, we can’t conclude on any trend over time. Therefore, we are unable to respond to this comment. We would need at least several records spread over longer periods of time to obtain a reliable pattern of nest relocation over time in a systematic manner.

• What was the relationship between colonies that were excavated and those that were cast? If they were performed in the same area at about the same time it would be very useful to see if the results from these two methods match with each other. R: The colonies that were excavated in ‘Cali’ and those that were cast were from the same area and were extracted at the same time. Unfortunately, our results don’t allow to see if the results from these two methods match with each other because, for the colonies that were excavated, it was not possible to obtain the details of the internal composition of each chamber. First, because the workers didn’t remain still in the chambers due to disturbance during the excavation. Second, because workers couldn’t be collected chamber by chamber but in aggregate and as fast as possible due to logistical constraints and the number of nests to be collected.

• Also, it would be useful if the authors end the nest architecture section with an overview of an average nest for this species in its natural habitat features across all the parameters examined.

R: Considering that there is no previous report on E. ruidum´s nest architecture for Colombia, we think that this comment has been addressed, at least partially, in the “Discussion” section where we compared the known traits of nest architecture for E. ruidum colonies from different geographic areas (see lines 351-357 and 403-411 in the revised version).

• Were there any changes across the seasons in the architecture? R: That question is very interesting, but we don’t have the data to answer it, because we didn’t plan initially to study a possible seasonality effect on nest architecture and didn’t cast nests in ‘Cali’ over different seasons. Please, see also our response above to the comment of Reviever #1 on lines 163-164 of the previous version about a possible seasonality effect.

Reviewer #3: Dear editor, I appreciate the reminder of my name as reviewer of the paper “Nest architecture and colony composition in two populations of Ectatomma ruidum sp. 2 (E. ruidum species complex) in southwestern Colombia ”,and I hope to contribute to it. The authors show an important data about ant species nesting and colony structure. However, I can recommend the publication of this article after major revisions. I think that there are major flaw is in the methods because different number of colonies has been evaluated, and is not clear if the colonies was studied in a disturbed area since they basically used colonies sampled at the University. Further, the results do not bring to much novelty and should be explored in the discussion (see https://doi.org/10.1007/s00040-018-0666-z). Thus, I would recommend to accept after major revisions. Thanks, I enjoy read the paper. R: Thanks for the overall positive comment; however, we partially disagree with some of the arguments regarding the flaws due to differences in the number of colonies studied at the two sites and “disturbed area” status of our sites. First, we consider our research valid and novel because no previous studies on nest architecture had been made in Colombian populations of E. ruidum sp. 2, and for the first time we report evidences linking nest architecture and possible polydomy in this species. Regarding the comment on the ‘disturbed areas’, we must emphasize that both study sites were located in disturbed open areas. In the southwestern geographic area of Colombia, E. ruidum sp. 2 tends to colonize disturbed areas, and we assumed that the specificities of each habitat might induce different nesting strategies. The objective of our study was not to make a detailed comparison of the nests of this species between the two areas, but rather to determine if, due to a different nesting strategy, there might be variations in the population and nest structure. On the other hand, we are confident that, because the large sample size of nests at both sites allowed for statistically significant differences even when R-values were low, the difference in the total number of nests analyzed at the two sites can’t be a source of problem or bias.

Specifically, I would recommend using the name of the species and explain that it could comprise a species complex, removing the sp. 2 from the text. R: We are sorry to disagree, but we can’t remove the ‘sp. 2’ from the text. The fact that we are studying here the species sp. 2 of the E. ruidum complex is important since four other cryptic species have been distinguished until now in this complex, and various of them, presenting different biological traits, can be found in a same geographical zone. This has been reported for Mexico (see references 39–42, and 80 in the manuscript) and this is also the case for E. ruidum sp. 1 and sp. 2 that are present in Colombia (see ref. 39 and 41). We explain this situation in the presentation of the species in the introduction of the revised version (see lines 68-70 and 74-75).

The limitations due the differences in sample size need to be addressed and better highlighted for readers. R: As mentioned above, because of the large sample size at both study sites, there are no limitations due to the differences in sample size. The number of nests collected in both areas is more than sufficient for the analyses we performed, and, in fact, is significantly larger than most sample sizes reported in the literature and typically used in this type of study. We didn’t intend to statistically compare the two sites but rather to describe the characteristics of the nests at each site. Therefore, we are confident that this important information for both study sites is valid and worthy of presentation in the manuscript.

Further, the discussion could be better explored if information and comparison with other species of taxa were considered in the discussion see the reference above as example.

I believe that these points must be addressed before it is ready to be published in Plos One. R: Both in the introduction and the dsicussion of the revised version of the manuscript, we are referring to various articles regarding nest architecture of other species of Ectatomma (see lines 59-67, 346-373, 385-395). Nevertheless, the focus of our study was E. ruidum sp. 2, and in our objectives we believe we have clearly specified that it is precisely the variation in nest architecture between populations of the same species, so far very poorly defined, that could provide insight into the factors triggering variations in nesting strategy.

Reviewer #4: This paper is based on a very large sample of ant nests. I commend the authors for that, and for the application of wax casting to the nest-census problem. They have collected a large amount of valuable data, but in my opinion, these data are under-analyzed. The story of this ant could be much more completely laid out. R: We thank the reviewer for this advice. We will take it into account in the near future, in a study more focused on the sociometry of the colonies, to understand better this ant species.

Since the authors used the wax-casting method that recovers all nest contents in place, why do they report these data in such crude form in the main text (+, ++, +++, etc)? R: The reviewer is perfectly right. It was our mistake to use (+, ++, +++, etc) in Table 1 while the complete detailed values were available in Table S2. This has been modified in the revised version (see new Table 1).

They report actual numbers as supplementary material, and do so by chamber, but under analyze these data in the main body of the paper. Most ants sort brood by stage, depth, conditions, etc. Indicative of the failure to see the importance of such details is line 255 where the authors refer to the correlations between worker numbers, pupae, larvae etc. as "very trivial." Rather than being trivial, they describe both the temporal and colony-level life of the colony and its success. The number of pupa in a colony is a measure of the current birth rate, the worker-larva ratio is a measure of efficiency, both predict the current growth rate. R: Thank you for this relevant and stimulating comment. Given that we completely changed the data analyses and used a Binomial GLM and PCAs for comparing queenright vs. queenless nests, the way the results were presented changed. However, when significant correlations were found, we tried to present them better, highlighting their relevance to the biology of the species (see Figs. 3 and S1 and lines 238-251, 258-263, 287-291).

The density of workers is potentially an important social measure. If callows can be recognized, then this gives a crude measure of the age-structure of the nest population. R: It is true that, as in many other ants, callow workers of Ectatomma have a distinctly lighter and softer cuticle than adults and, a priori, can be quite easily distinguished. Unfortunately, when melting the paraffin, due to a probably too high temperature, the workers were ‘cooked’ so that it was not possible to differentiate callows from adults as Tschinkel did for example with Pogonomyrmex badius (see ref. 16) and, therfore, the age-structure of the nest population couldn’t be assessed on the basis of the data presented here.

I see these and many more as lost opportunities. R: The reviewer is quite right, and we have obviously neglected to take into account a number of parameters that would have been important for a sociometric analysis of E. ruidum sp. 2 colonies. We can only admit that he is right in considering this lack of data as lost opportunities. However, we would like to emphasize that the essential objective of our work was not to perform a sociometric study of the Colombian populations of this species, but to investigate, at the level of the differences in nest architecture, which could be the factors explaining the use of a polydomic strategy at the local scale.

I don't see much value in publishing lists of correlations unless the lists include the slope and the R2 of the relationship. How much of the variance is associated with a factor, and how fast is the change in y as x changes, and in which direction? These are the relationships of interest. What is the increase in nest area (or volume) per worker? Brood per worker? Etc. Overall, I think the authors missed a meaningful analysis of the nest populations, focusing instead on minor details of nest architecture, both within and across populations. R: The reviewer is correct. However, we probably don't need to add the R2 slopes anymore because the analyses have changed. In fact, the new statistical analyses are more robust and help to better understand how the population and nest structure variables change with the presence/absence of a queen. On the other hand, as stated slightly above, although our main objective was not a sociometric study of the Colombian populations of E. ruidum sp. 2, when significant correlations were found, we have tried to present them with emphasis on their relevance to the biology of the species. In view of the various comments of the reviewer on this subject, we are convinced not only of the usefulness of reprocessing all these data but especially of the need to complete them to prepare, in what we hope will be a not too distant future, a publication centered on the sociometry of E. ruidum sp. 2 colonies. However, this requires working conditions that the current pandemic situation doesn’t yet allow.

While there is a comparison between collection sites, these confound season with site. The authors report site differences in the nest depth, the number of workers and brood, as well as in the rate of queenrightness. To what degree are differences the result of differences in season, site or both? R: The reviewer is correct; we can’t discard a simultaneous effect of stationality and site. However, the exact way in which each of these factors affect nest architecture, that is, the contribution of each one separately, can’t be distinguished here. Therefore, we can’t conclude or try to compare both sites. We addressed this point in the revised discussion of our manuscript (see lines 335-337).

Among the most interesting are differences in queen number. The predominance of queenless nests indicates that this species is polydomous, but polydomy can be seasonal as well as related to colony size. Some ant species rear sexuals in either the presence or absence of queens. I think these data can tell us something about the annual cycle of this species. R: This is an interesting point. For the moment, we don’t have the data to verify if polydomy is seasonal or related to the size of the colony. However, the influence of colony size seems unlikely because, as noted in the discussion of the revised version (see lines 410-412) the overall average number of adults per nest reported for monodomous populations of E. ruidum sp. 2 in southern Mexico (87.0 ± 2.4, n = 683) is quite similar to that found in our polydomous Colombian populations (78.7 ± 3.6, n = 152). A study following the annual cycle of the species would deserve to be done.

The high nest density is probably also relevant to polydomy. R: Although we don’t have a definitive, precise answer regarding the influence of nest density on polydomy, we have briefly addressed this point in the revised discussion (see lines 457-461).

What was the spacing between nests like? Was there worker traffic between them? R: The average distance between neighboring nests was about 74 cm and a few individual transports were observed between nests. We have added this information in the presentation of the results in the revised version. (see lines 193-195).

Commendably, the authors present much of their raw data as Supporting Information, but the data I see there should have been more thoroughly analyzed and presented as graphs and figures in the main text. R: We performed new analyses (binomial GLM and PCA), removed unnecessary tables, and presented new figures both in the main text (Figures 3 and 5) and in the Supplementary Information (Figure S1) that hopefully provide more useful information.

Some other points: Line 44 citations on bioturbation should include papers by Tschinkel on Pogonomyrmex and Trachymyrmex bioturbation. R: Thanks for the suggestion. This was done. (see lines 44-45 and -497).

Then, after introducing bioturbation as a subject, the authors do not discuss how Ectotomma contributes to bioturbation in its habitat. Since they have data on nest volumes and their rates of abandonment and new appearance, they could conceivably comment on bioturbation. R: The reviewer is right. In fact, the bioturbation impact of E. ruidum sp. 2 nests has been addressed in a previously published paper and our objective here was not to focus on that aspect. We therefore simply refer merely to our publication in Pedobiologia (Ref. 9 in the manuscript) and only provide some complementary information resulting from our new data in the discussion of the revised version (see lines 340-346).

Line 71-2, Tschinkel provided such data for several other species as well, and never made any claims about plant roots (Line 75). R: While it is true that such a mention for Pogonomyrmex badius didn’t appear in Tschinkel's papers, in contrast in the last part of the discussion of the paper on Formica pallidefulva (Mikheyev & Tschinkel 2004), the authors clearly stated "Second, the high concentration of roots in the upper soil regions may provide structural support for the chambers, allowing the ants to build large chambers without risking cave-ins". In any case, this clarification is no longer relevant here since this part has been removed in the revised version.

The authors might find his recently published book on Ant Architecture helpful. R: Thank you for the suggestion. The recent book of Tschinkel was very interesting for a comprehensive view of nest architecture in ants and we quoted it in the introduction when presenting the influence of the nest architecture on both the spatial structuration of the colony population within the nest and their collective behavior (see lines 57-59 and 539-540). However, we didn’t find other new specific information useful for our discussion.

I think the Introduction needs to be briefer and more focused, and that is true for the discussion too. R: This has been made for the introduction. Regarding the discussion, some changes have been made in the presentation and several additional details have been provided to explain our results and hypothesis. Consequently, the discussion was not really shortened, but we hope that, at least, it is now clearer.

Minor points: Line 201-203 doesn't really describe turnover in the literal sense. In turnover, the total numbers remain more or less stable, but the membership changes. Here we have disappearances matched with far more new nests. A different description is needed, as well as an interpretation of what the patterns may mean. R: The sentence was modified as follows “Although the difference between the first and second assessments was 485 nest entries, it was estimated that about 200 entries recorded during the dry season had disappeared, making the number of new nests built between the two periods actually 685” (see lines 190-193). Additionally, an attempt to interpret this pattern is now presented in the revised discussion (see lines 330-336).

I think this could be made into a paper that reveals much more about the biology of this ant than it currently does. I hope the authors will succeed at doing this. R: Thanks for the suggestion. Although it was not the aim of the present study, we have attempted to reveal more about ant biology, and we hope that the new version has succeeded better. However, future work focusing on sociometric analysis of colonies would definitely be needed.

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PLoS One. doi: 10.1371/journal.pone.0263382.r003

Decision Letter 1

Maykon Passos Cristiano

15 Nov 2021

PONE-D-21-13547R1

Nest architecture and colony composition in two populations of Ectatomma ruidum sp. 2 (E. ruidum species complex) in southwestern Colombia

PLOS ONE

Dear Dr. Lachaud,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we have decided that your manuscript does not meet our criteria for publication and must therefore be rejected.

I forwarded the manuscript to the reviewers again and received input from two reviewers. After consideration of all revisions, I have decided that your manuscript does not reach scientific soundness for publications.

I am sorry that we cannot be more positive on this occasion, but hope that you appreciate the reasons for this decision.

Yours sincerely,

Maykon Passos Cristiano, D. Sc.

Academic Editor

PLOS ONE

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #3: All comments have been addressed

Reviewer #4: All comments have been addressed

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

Reviewer #3: Yes

Reviewer #4: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #3: Yes

Reviewer #4: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

Reviewer #3: Yes

Reviewer #4: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

Reviewer #3: Yes

Reviewer #4: Yes

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6. Review Comments to the Author

Reviewer #3: Dear authors,

The manuscript was improved and the majority of questions and suggestions has been explained or corrected in the main text. Now the mansucript can be accepted for publication.

Reviewer #4: The authors have greatly improved this paper since the first review. I understand that they did not always have the data to follow some of my suggestions, but they did a good job in bringing the message across. I have very few suggestions for improvement.

I had to look up the meaning of gangue. I don't think I would have used the word in that context, but it is colorful. I doubt it is often used outside the context of mining, but then, you never know how many miners will read this paper.

Line 265. This calculates to 4.6 nests per queen. Couldn't you claim that the average polydomous colony has 4.6 nests? Or do you think some colonies are truly queenless? You even state that there are no gamergates or ergatoid queens, so doesn't it follow that there are 4.6 nests per polydomous colony? Obviously, it would be nice to know the range, but at least you have a mean.

Line 346 and 388. Why not make an estimate of the amount of soil excavated by your population, especially since you did a second count and discovered many new nests? The mean weight and depth of the bioturbation rate could be estimated.

There are too many references. I suggest culling the list to be more targeted and relevant to the subject. This is not a review article.

**********

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Reviewer #3: No

Reviewer #4: No

- - - - -

For journal use only: PONEDEC3

PLoS One. 2022 Feb 2;17(2):e0263382. doi: 10.1371/journal.pone.0263382.r004

Author response to Decision Letter 1

24 Nov 2021

Reviewer #3: Dear authors,

The manuscript was improved and the majority of questions and suggestions has been explained or corrected in the main text. Now the mansucript can be accepted for publication.

Response: We thank the reviewer. The comment is sufficiently explicit and clear and does not require any specific response from us.

Response: We particularly appreciated the gently mocking tone of this comment. Not being English speakers ourselves, we followed the advice of the English colleague who revised our text, but we have to admit that the term "gangue" is perhaps too specific to mining, even if this term is perfectly appropriate in our respective languages of origin (Spanish and French). In our revision, we have replaced "earthy gangue " with "soil matrix " which is perhaps more commonly used and understandable to English speakers (see lines 142 and 157 in the new revised version).

Response: It is true that, based on our data, we can propose that an average polydomous colony has 4.6 nests even though the precise range is difficult to specify. However, as indicated in manuscript PONE-D-21-13547R1 (see lines 432-435 of the previous version), at least some of these queenless nests truly reflect a natural phenomenon of queen death or colony weakening. We have added a few lines in the discussion to take this comment into account (see lines 441-448 in the new revised version).

Response: The reviewer is absolutely right. Therefore, we have added in the discussion the requested bioturbation estimate (in kg of dry soil per hectare per day) taking into account the available values on our population (see lines 346-351 of the new revised version).

There are too many references. I suggest culling the list to be more targeted and relevant to the subject. This is not a review article.

Response: We have done our best to address this comment by reducing the total number of citations by over 20%.

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PLoS One. doi: 10.1371/journal.pone.0263382.r005

Decision Letter 2

Nicolas Chaline

19 Jan 2022

Nest architecture and colony composition in two populations of Ectatomma ruidum sp. 2 (E. ruidum species complex) in southwestern Colombia

PONE-D-21-13547R2

Dear Dr. Lachaud,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

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Kind regards,

Nicolas Chaline

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

PLoS One. doi: 10.1371/journal.pone.0263382.r006

Acceptance letter

Nicolas Chaline

24 Jan 2022

PONE-D-21-13547R2

Nest architecture and colony composition in two populations of Ectatomma ruidum sp. 2 (E. ruidum species complex) in southwestern Colombia

Dear Dr. Lachaud:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org.

If we can help with anything else, please email us at plosone@plos.org.

Thank you for submitting your work to PLOS ONE and supporting open access.

Kind regards,

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on behalf of

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Academic Editor

PLOS ONE

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

S1 Table. Composition of the population of the E. ruidum sp. 2 nests extracted at the University Campus of the Universidad del Valle (‘Cali’) and at Vereda El Rosal, Caldono (‘Cauca’).

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S2 Table. Chamber dimensions (in cm), volume (in cm³), and population within each chamber for the 24 E. ruidum sp. 2 nests extracted using the paraffin wax technique at ‘Cali’.

Q: queens; G: gynes; M: males; W: workers; P: pupae; L: larvae.

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S1 Fig. Relationship between different categories of nest population for the 152 complete nests of E. ruidum sp. 2. extracted.

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Data Availability Statement

All relevant data are within the paper and its Supporting Information files.

[pone.0263382.ref001] 1.Folgarait PJ. Ant biodiversity and its relationship to ecosystem functioning: a review. Biodivers Conserv. 1998; 7: 1221–1244. 10.1023/A:1008891901953. [DOI] [Google Scholar]

[pone.0263382.ref002] 2.Lobry de Bruyn LA, Conacher AJ. The bioturbation activity of ants in agricultural and naturally vegetated habitats in semi-arid environments. Aust J Soil Res. 1994; 32: 555–570. 10.1071/SR9940555. [DOI] [Google Scholar]

[pone.0263382.ref003] 3.Cammeraat ELH, Risch AC. The impact of ants on mineral soil properties and processes at different spatial scales. J Appl Entomol. 2008; 132: 285–294. [Google Scholar]

[pone.0263382.ref004] 4.Tschinkel WR. Biomantling and bioturbation by colonies of the Florida harvester ant, Pogonomyrmex badius. PLoS ONE. 2015; 10: e0120407. doi: 10.1371/journal.pone.0120407 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0263382.ref005] 5.Tschinkel WR, Seal JN. Bioturbation by the fungus-gardening ant, Trachymyrmex septentrionalis. PLoS ONE. 2016; 11: e0158920. doi: 10.1371/journal.pone.0158920 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0263382.ref006] 6.Santamaría C, Lachaud J-P, Armbrecht I. Effects of nest building by the dominant hunting ant, Ectatomma sp. 2 (ruidum complex), on Andean coffee plantations. Pedobiologia. 2020; 79: 150626. [Google Scholar]

[pone.0263382.ref007] 7.Bollazzi M, Roces F. The thermoregulatory function of thatched nests in the South American grass-cutting ant, Acromyrmex heyeri. J Insect Sci. 2010; 10: 137. doi: 10.1673/031.010.13701 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0263382.ref008] 8.Dejean A, Lachaud J-P. Ecology and behavior of a seed-eating ponerine ant: Brachyponera senaarensis (Mayr). Insect Soc. 1994; 41: 191–210. [Google Scholar]

[pone.0263382.ref009] 9.Kadochová Š, Frouz J. Thermoregulation strategies in ants in comparison to other social insects, with a focus on red wood ants (Formica rufa group). F1000Research. 2014; 2: 280. doi: 10.12688/f1000research.2-280.v2 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0263382.ref010] 10.Elahi R. The effect of water on the ground nesting habits of the giant tropical ant, Paraponera clavata. J Insect Sci. 2005; 5: 34. doi: 10.1093/jis/5.1.34 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0263382.ref011] 11.Ceusters R. Simulation du nid naturel des fourmis par des nids artificiels placés sur un gradient de température. Actes Coll Insect Soc. 1986; 3: 235–241. [Google Scholar]

[pone.0263382.ref012] 12.Tschinkel WR. Sociometry and sociogenesis of colonies of the harvester ant, Pogonomyrmex badius: distribution of workers, brood and seeds within the nest in relation to colony size and season. Ecol Entomol. 1999; 24: 222–237. [Google Scholar]

[pone.0263382.ref013] 13.Fresneau D, Corbara B, Lachaud J-P. Organisation sociale et structuration spatiale autour du couvain chez Pachycondyla apicalis. Actes Coll Insect Soc. 1989; 5: 83–92. [Google Scholar]

[pone.0263382.ref014] 14.Tschinkel WR. The nest architecture of the Florida harvester ant, Pogonomyrmex badius. J Insect Sci. 2004; 4: 21. doi: 10.1093/jis/4.1.21 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0263382.ref015] 15.Tschinkel WR. The nest architecture of the ant, Camponotus socius. J Insect Sci. 2005; 5: 9. doi: 10.1093/jis/5.1.9 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0263382.ref016] 16.Moreira AA, Forti LC, Boaretto MAC, Andrade APP, Lopes JFS, Ramos VM. External and internal structure of Atta bisphaerica Forel (Hymenoptera: Formicidae) nests. J Appl Entomol. 2004; 128: 204–211. [Google Scholar]

[pone.0263382.ref017] 17.Caldato N, Camargo RS, Forti LC, Andrade APP, Lopes JFS. Nest architecture in polydomous grass-cutting ants (Acromyrmex balzani). J Nat Hist. 2016; 50: 1561–1581. [Google Scholar]

[pone.0263382.ref018] 18.Tschinkel WR. Ant Architecture: The Wonder, Beauty, and Science of Underground Nests. Princeton, New Jersey: Princeton University Press; 2021. [Google Scholar]

[pone.0263382.ref019] 19.Pinter-Wollman N. Nest architecture shapes the collective behaviour of harvester ants. Biol Lett. 2015; 11: 20150695. doi: 10.1098/rsbl.2015.0695 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0263382.ref020] 20.Antonialli-Junior WF, Giannotti E. Nest architecture and populations dynamics of the ponerine ant, Ectatomma opaciventre Roger (Hymenoptera: Formicidae). J Adv Zool. 1997; 18: 64–71. [Google Scholar]

[pone.0263382.ref021] 21.Antonialli WF Jr, Giannotti E. Nest architecture and population dynamics of the ponerine ant Ectatomma edentatum (Hymenoptera, Formicidae). Sociobiology 2001; 38: 475–486. [Google Scholar]

[pone.0263382.ref022] 22.Antonialli-Junior WF, Tofolo VC, Giannotti E. Population dynamics of Ectatomma planidens (Hymenoptera: Formicidae) under laboratory conditions. Sociobiology. 2007; 50: 1005–1013. [Google Scholar]

[pone.0263382.ref023] 23.Lapola DM, Antonialli Júnior WF, Giannotti E. Arquitetura de ninhos da formiga neotropical Ectatomma brunneum F. Smith, 1858 (Formicidae: Ponerinae) em ambientes alterados. Rev Bras Zoo. 2003; 5: 177–188. [Google Scholar]

[pone.0263382.ref024] 24.Vieira AS, Antonialli Junior WF. Populational fluctuation and nest architecture of Ectatomma brunneum (Hymenoptera, Formicidae) in remaining areas of pasture, Dourados- MS, Brazil. Sociobiology. 2006; 47: 275–287. [Google Scholar]

[pone.0263382.ref025] 25.Vieira AS, Antonialli-Junior WF, Fernandes WD. Modelo arquitetônico de ninhos da formiga Ectatomma vizottoi Almeida (Hymenoptera, Formicidae). Rev Bras Entomol. 2007; 51: 489–493. [Google Scholar]

[pone.0263382.ref026] 26.Weber NA. Two common ponerine ants of possible economic significance, Ectatomma tuberculatum (Olivier) and E. ruidum Roger. Proc Entomol Soc Washington. 1946; 48: 1–16. [Google Scholar]

[pone.0263382.ref027] 27.Lachaud J-P, López Méndez JA, Schatz B, De Carli P, Beugnon G. Comparaison de l’impact de prédation de deux ponérines du genre Ectatomma dans un agroécosystème néotropical. Actes Coll Insect Soc. 1996; 10: 67–74. [Google Scholar]

[pone.0263382.ref028] 28.Lachaud J-P. Ectatomma. pp. 358–365. In: Starr C (ed) Encyclopedia of Social Insects. Cham: Springer; 2019. 10.1007/978-3-319-90306-4_41-1. [DOI] [Google Scholar]

[pone.0263382.ref029] 29.Delabie JC. The ant problems of cocoa farms in Brazil. pp. 555–569. In: Vander Meer RK, Jaffe K, Cedeno A (eds) Applied myrmecology: A world perspective. Boulder, Colorado, USA: Westview Press; 1990. [Google Scholar]

[pone.0263382.ref030] 30.Lachaud J-P. Foraging activity and diet in some Neotropical ponerine ants. I. Ectatomma ruidum Roger (Hymenoptera, Formicidae). Folia Entomol Mex. 1990; 78: 241–256. [Google Scholar]

[pone.0263382.ref031] 31.Aguilar-Velasco RG, Poteaux C, Meza-Lázaro R, Lachaud J-P, Dubovikoff D, Zaldívar-Riverón A. Uncovering species boundaries in the Neotropical ant complex Ectatomma ruidum (Ectatomminae) under the presence of nuclear mitochondrial paralogues. Zool J Linn Soc. 2016; 178: 226–240. doi: 10.1111/zoj.12407 [DOI] [Google Scholar]

[pone.0263382.ref032] 32.Meza-Lázaro RN, Poteaux C, Bayona-Vásquez NJ, Branstetter MG, Zaldívar-Riverón A. Extensive mitochondrial heteroplasmy in the neotropical ants of the Ectatomma ruidum complex (Formicidae: Ectatomminae). Mitochondrial DNA A. 2018; 29: 1203–1214. doi: 10.1080/24701394.2018.1431228 [DOI] [PubMed] [Google Scholar]

[pone.0263382.ref033] 33.Peña-Carrillo KI, Poteaux C, Leroy C, Meza-Lazáro RN, Lachaud J-P, Zaldívar-Riverón A, et al. Highly divergent cuticular hydrocarbon profiles in the cleptobiotic ants of the Ectatomma ruidum species complex. Chemoecology. 2021; 31: 125–135. [Google Scholar]

[pone.0263382.ref034] 34.Peña Carrillo KI, Lorenzi MC, Brault M, Devienne P, Lachaud J-P, Pavan G, et al. A new putative species in the Ectatomma ruidum complex (Formicidae: Ectatomminae) produces a species-specific distress call. Bioacoustics. In press. doi: 10.1080/09524622.2021.1938226 [DOI] [Google Scholar]

[pone.0263382.ref035] 35.Arias-Penna TM. Subfamilia Ectatomminae. pp. 53–107. In: Jiménez E, Fernández F, Arias TM, Lozano-Zambrano FH (Eds). Sistemática, biogeografía y conservación de las hormigas cazadoras de Colombia. Bogotá, Colombia: Instituto de Investigaciones de Recursos Biológicos Alexander von Humboldt; 2008. [Google Scholar]

[pone.0263382.ref036] 36.Dáttilo W, Vásquez-Bolaños M, Ahuatzin DA, Antoniazzi R, Chávez-González E, Corro E, et al. Mexico ants: incidence and abundance along the Nearctic-Neotropical interface. Ecology. 2020; 101: e02944. doi: 10.1002/ecy.2944 [DOI] [PubMed] [Google Scholar]

[pone.0263382.ref037] 37.Passera L, Lachaud J-P, Gomel L. Individual food source fidelity in the neotropical ponerine ant Ectatomma ruidum Roger (Hymenoptera Formicidae). Ethol Ecol Evol. 1994; 6: 13–21. [Google Scholar]

[pone.0263382.ref038] 38.Perfecto I. Indirect and direct effects in a tropical agroecosystem: the maize-pest-ant system in Nicaragua. Ecology. 1990; 71: 2125–2134. [Google Scholar]

[pone.0263382.ref039] 39.Ibarra-Núñez G, García JA, López JA, Lachaud J-P. Prey analysis in the diet of some ponerine ants (Hymenoptera: Formicidae) and web-building spiders (Araneae) in coffee plantations in Chiapas, Mexico. Sociobiology. 2001; 37: 723–755. [Google Scholar]

[pone.0263382.ref040] 40.Lachaud J-P, Fresneau D, García-Pérez J. Étude des stratégies d’approvisionnement chez 3 espèces de fourmis ponérines (Hymenoptera, Formicidae). Folia Entomol. Mex. 1984; 61: 159–177. [Google Scholar]

[pone.0263382.ref041] 41.Santamaría C, Armbrecht I, Lachaud J-P. Nest distribution and food preferences of Ectatomma ruidum (Hymenoptera: Formicidae) in shaded and open cattle pastures of Colombia. Sociobiology. 2009; 53: 517–541. [Google Scholar]

[pone.0263382.ref042] 42.Breed MD, Abel P, Bleuze TJ, Denton SE. Thievery, home ranges, and nestmate recognition in Ectatomma ruidum. Oecologia. 1990; 84: 117–121. doi: 10.1007/BF00665604 [DOI] [PubMed] [Google Scholar]

[pone.0263382.ref043] 43.Schatz B, Lachaud J-P. Effect of high nest density on spatial relationships in two dominant ectatommine ants (Hymenoptera: Formicidae). Sociobiology. 2008; 51: 623–643. [Google Scholar]

[pone.0263382.ref044] 44.De Carli P, Lachaud J-P, Beugnon G, López-Méndez JA. Études en milieu naturel du comportement de cleptobiose chez la fourmi néotropicale Ectatomma ruidum (Hymenoptera, Ponerinae). Actes Coll Insect Soc. 1998; 11: 29–32. [Google Scholar]

[pone.0263382.ref045] 45.Guénard B, McGlynn TP. Intraspecific thievery in the ant Ectatomma ruidum is mediated by food availability. Biotropica. 2013; 45: 497–502. [Google Scholar]

[pone.0263382.ref046] 46.De Carli P. Interactions intraspécifiques chez une fourmi néotropicale: Ectatomma ruidum Roger (Hymenoptera, Ponerinae). PhD Thesis, University Paul Sabatier, Toulouse; 1997.

[pone.0263382.ref047] 47.Quevedo Vega CJ. Interacciones competitivas y variabilidad en las estrategias de nidificación de Ectatomma ruidum (Formicidae: Ectatomminae). Trabajo de Grado. Universidad del Valle, Cali; 2015. [Google Scholar]

[pone.0263382.ref048] 48.Berrod L. Étude de la polydomie chez la fourmi Ectatomma ruidum Roger (Hymenoptera, Formicidae). M. Sci. Thesis, Université Paris 13; 2017.

[pone.0263382.ref049] 49.Santamaría C. Interacciones entre nidos de Ectatomma ruidum, ¿polidomia o cleptobiosis? Bol Mus Entomol Univ Valle. 2017; 18 (Supl. 1): 12. [Google Scholar]

[pone.0263382.ref050] 50.CVC-CIAT-DAGMA. Identificación de Zonas y Formulación de Propuestas para el Tratamiento de Islas de Calor, Municipio de Santiago de Cali. Convenio CVC–CIAT–DAGMA No. 110 de 2015 Informe Técnico. p. 22; 2015.

[pone.0263382.ref051] 51.Tschinkel WR. Methods for casting subterranean ant nests. J Insect Sci. 2010; 10: 88. doi: 10.1673/031.010.8801 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0263382.ref052] 52.Tschinkel WR. A method for using ice to construct subterranean ant nests (Hymenoptera: Formicidae) and other soil cavities. Myrmecol News. 2013; 18: 99–102. [Google Scholar]

[pone.0263382.ref053] 53.Forti LC, Moreira AA, Camargo RS, Caldato N, Castellani MA. Nest architecture development of grass-cutting ants. Rev Bras Entomol. 2018; 62: 46–50. [Google Scholar]

[pone.0263382.ref054] 54.Toffin E, Di Paolo D, Campo A, Detrain C, Deneubourg J-L. Shape transition during nest digging in ants. Proc Nat Acad Sci USA 2009; 106: 18616–18620. doi: 10.1073/pnas.0902685106 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0263382.ref055] 55.Pardo-Lorcano LC, Montoya J, Bellotti AC, van Schoonhoven A. Structure and composition of the white grub complex (Coleoptera: Scarabaeidae) in agroecological systems of northern Cauca, Colombia. Fla Entomol. 2005; 88: 355–362. [Google Scholar]

[pone.0263382.ref056] 56.R Development Core Team. 2020. R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. URL https://www.R-project.org/. [Google Scholar]

[pone.0263382.ref057] 57.Santamaría CA, Domínguez-Haydar Y, Armbrecht I. Cambios en la distribución de nidos y abundancia de la hormiga Ectatomma ruidum (Roger 1861) en dos zonas de Colombia. Bol Mus Entomol Univ Valle. 2009; 10(2): 10–18. [Google Scholar]

[pone.0263382.ref058] 58.Lachaud J-P, Pérez-Lachaud G. Impact of natural parasitism by two eucharitid wasps on a potential biocontrol agent ant in southeastern Mexico. Biol Control. 2009; 48: 92–99. [Google Scholar]

[pone.0263382.ref059] 59.McGlynn TP. The ecology of nest movement in social insects. Annu Rev Entomol. 2012; 57: 291–308. doi: 10.1146/annurev-ento-120710-100708 [DOI] [PubMed] [Google Scholar]

[pone.0263382.ref060] 60.Tschinkel WR. Nest relocation and excavation in the Florida harvester ant, Pogonomyrmex badius. PLoS ONE. 2014; 9: e112981. doi: 10.1371/journal.pone.0112981 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0263382.ref061] 61.Rocha FH, Lachaud J-P, Hénaut Y, Pozo C, Pérez-Lachaud G. Nest site selection during colony relocation in Yucatan Peninsula populations of the ponerine ants Neoponera villosa (Hymenoptera: Formicidae). Insects. 2020; 11: 200. [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0263382.ref062] 62.Poteaux C, Prada-Achiardi FC, Fernández F, Lachaud J-P. Diversidade genética e fenotípica no gênero Ectatomma. pp. 127–144. In: Delabie JHC, Feitosa RM, Serrão JE, Mariano CSF, Majer JD (Eds). As formigas poneromorfas do Brasil. Ilhéus: Editus; 2015. [Google Scholar]

[pone.0263382.ref063] 63.Vásquez-Ordóñez AA, Armbrecht I, Pérez-Lachaud G. Effect of habitat type on parasitism of Ectatomma ruidum by eucharitid wasps. Psyche. 2012; Article ID 170483. [Google Scholar]

[pone.0263382.ref064] 64.Pérez-Lachaud G, Klompen H, Poteaux C, Santamaría C, Armbrecht I, Beugnon G, et al. Context dependent life-history shift in Macrodinychus sellnicki mites attacking a native ant host in Colombia. Sci Rep. 2019; 9: 8394. doi: 10.1038/s41598-019-44791-2 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0263382.ref065] 65.Schatz B, Lachaud J-P, Fourcassié V, Beugnon G. Densité et distribution des nids chez la fourmi Ectatomma ruidum Roger (Hymenoptera; Formicidae; Ponerinae). Actes Coll Insect Soc. 1998; 11: 103–107. [Google Scholar]

[pone.0263382.ref066] 66.Wheeler WM. Courtship of the Calobatas. The kelep ant and the courtship of its mimic, Cardiacephala myrmex. J Hered. 1924; 25: 485–495. [Google Scholar]

[pone.0263382.ref067] 67.Wheeler WM. The fungus-growing ants of North America. Bull Am Mus Nat Hist. 1907; 23: 669–807. [Google Scholar]

[pone.0263382.ref068] 68.Bruch C. Contribución al estudio de las hormigas de la provincia de San Luis. Rev Mus La Plata. 1916; 23: 291–357. [Google Scholar]

[pone.0263382.ref069] 69.Halfen AF, Hasiotis ST. Neoichnological study of the traces and burrowing behaviors of the western harvester ant Pogonomyrmex occidentalis (Insecta: Hymenoptera: Formicidae): Paleopedogenic and paleoecological implications. Palaios. 2010; 25: 703–720. [Google Scholar]

[pone.0263382.ref070] 70.Noirot C, Darlington JPEC. Termite nests: architecture, regulation and defence. pp. 121–139. In: Abe Y, Bignell DE, Higashi T (eds) Termites: Evolution, Sociality, Symbioses, Ecology. Dordrecht, The Netherlands: Springer; 2000. doi: 10.1046/j.1365-2222.2000.00751.x [DOI] [Google Scholar]

[pone.0263382.ref071] 71.Wang D, McSweeney K, Lowery B, Norman JM. 1995. Nest structure of ant Lasius neoniger Emery and its implications to soil modification. Geoderma. 1995; 66: 259–272. [Google Scholar]

[pone.0263382.ref072] 72.Le Masne G. Observations sur les relations entre le couvain et les adultes chez les fourmis. Ann Sc Nat Zool. 1953; 15: 1–56. [Google Scholar]

[pone.0263382.ref073] 73.Dejean A, Lachaud J-P. Polyethism in the ponerine ant Odontomachus troglodytes: interaction of age and interindividual variability. Sociobiology. 1991; 18: 177–196. [Google Scholar]

[pone.0263382.ref074] 74.Cassill D, Tschinkel WR, Vinson SB. Nest complexity, group size and brood rearing in the fire ant, Solenopsis invicta. Insect Soc. 2002; 49: 158–163. [Google Scholar]

[pone.0263382.ref075] 75.Lachaud J-P, Cadena A, Pérez-Lachaud G, Schatz B. Polygynie et stratégies reproductives chez une ponérine néotropicale, Ectatomma ruidum. Actes Coll Insect Soc. 1999; 12: 53–59. [Google Scholar]

[pone.0263382.ref076] 76.Lachaud J-P, Cadena A, Schatz B, Pérez-Lachaud G, Ibarra-Núñez G. Queen dimorphism and reproductive capacity in the ponerine ant, Ectatomma ruidum Roger. Oecologia. 1999; 120: 515–523. doi: 10.1007/s004420050885 [DOI] [PubMed] [Google Scholar]

[pone.0263382.ref077] 77.Cadena A, Pérez-Lachaud G, Schatz B, Lachaud J-P. Inhibition de la ponte dans les sociétés polygynes de Ectatomma ruidum (Hymenoptera, Formicidae, Ponerinae). Actes Coll Insect Soc. 2001; 14: 87–93. [Google Scholar]

[pone.0263382.ref078] 78.Lenoir J-C, Lachaud J-P, Nettel A, Fresneau D, Poteaux C. The role of microgynes in the reproductive strategy of the neotropical ant Ectatomma ruidum. Naturwissenschaften. 2011; 98: 347–356. doi: 10.1007/s00114-011-0774-3 [DOI] [PubMed] [Google Scholar]

[pone.0263382.ref079] 79.Fernández F. Las hormigas cazadoras del género Ectatomma (Formicidae: Ponerinae) en Colombia. Caldasia. 1991; 16: 551–564. [Google Scholar]

[pone.0263382.ref080] 80.Debout G, Schatz B, Elias M, McKey D. Polydomy in ants: what we know, what we think we know, and what remains to be done. Biol J Linn Soc. 2007; 90: 319–348. [Google Scholar]

[pone.0263382.ref081] 81.Cerdá X, Dahbi A, Retana J. Spatial patterns, temporal variability, and the role of multi‐nest colonies in a monogynous Spanish desert ant. Ecol Entomol. 2002; 27: 7–15. doi: 10.1046/j.0307-6946.2001.00386.x [DOI] [Google Scholar]

[pone.0263382.ref082] 82.Anderson C, McShea DW. Individual versus social complexity, with particular reference to ant colonies. Biol Rev. 2001; 76: 211–237. [DOI] [PubMed] [Google Scholar]

PERMALINK

Nest architecture and colony composition in two populations of Ectatomma ruidum sp. 2 (E. ruidum species complex) in southwestern Colombia

Carlos Santamaría

Inge Armbrecht

Jean-Paul Lachaud

Roles

Abstract

Introduction

Material and methods

Ethics statement

Study areas and nest extraction

Fig 1. Wax cast nest collection.

Data analysis

Results

Nest abundance and general considerations on E. ruidum sp. 2 nest architecture

Fig 2. Examples of nests of Ectatomma ruidum sp. 2 of similar depth, cast in paraffin wax.

Nest casts

Table 1. Mean (± SEM) volume and depth of the chambers, tunnel length, and composition of the population of each chamber according to its relative position for the 24 E. ruidum sp. 2 nests extracted using the paraffin wax technique.

Fig 3.

Fig 4. Mean (± SEM) of E. ruidum sp. 2 workers per chamber in the 24 nests collected using the paraffin wax technique.

Relationships between colony composition and architectural variables

Table 2. Binomial GLM comparing queenright vs. queenless nests.

Fig 5. Principal Component Analysis (PCA) including all structural and population variables of excavated nests according to the presence or absence of a queen.

Discussion

Nest distribution and nest architecture traits

Queen influence on nest physical and populational characteristics and possible relationship between nest architecture and polydomy

Supporting information

Acknowledgments

Data Availability

Funding Statement

References

Decision Letter 0

Maykon Passos Cristiano

Roles

Author response to Decision Letter 0

Decision Letter 1

Maykon Passos Cristiano

Roles

Author response to Decision Letter 1

Decision Letter 2

Nicolas Chaline

Roles

Acceptance letter

Nicolas Chaline

Roles

Associated Data

Supplementary Materials

Data Availability Statement

ACTIONS

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RESOURCES

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