Fine-scale associational effects: Single plant neighbours can alter susceptibility of focal plants to herbivores

Patrick B Finnerty; Peter B Banks; Adrian M Shrader; Clare McArthur

doi:10.1371/journal.pone.0330572

. 2025 Aug 21;20(8):e0330572. doi: 10.1371/journal.pone.0330572

Fine-scale associational effects: Single plant neighbours can alter susceptibility of focal plants to herbivores

Patrick B Finnerty ^1,^*, Peter B Banks ¹, Adrian M Shrader ², Clare McArthur ¹

Editor: Showkat Ahmad Ganie³

PMCID: PMC12370084 PMID: 40839639

Abstract

The neighbourhood of plants in a patch can shape vulnerability of focal plants to herbivores, known as an associational effect. Associational effects of plant neighbourhoods are widely recognised. But whether a single neighbouring plant can exert an associational effect is unknown. Here, we tested if single neighbours indeed do influence the likelihood that a focal plant is visited and eaten by a mammalian herbivore. We then tested whether any refuge effect is strengthened by having more neighbours in direct proximity to a focal plant. We used native plant species and a browser/mixed feeder mammalian herbivore (swamp wallabies (Wallabia bicolor)) free-ranging in natural vegetation. We found that a single neighbouring plant did elicit associational effects. Specifically, plant pairs consisting of one high-quality seedling next to a single low-quality plant were visited and browsed by wallabies later and less than pairs of two high-quality seedlings. Having more neighbours did not strengthen these associational effects. Compared with no neighbours, one or five low-quality neighbours had the same effect in delaying time taken for wallabies to first visit a plot and browse on a high-quality focal seedling. While traditionally a ‘patch’ refers to a broad sphere-of-influence neighbouring plants have on a focal plant, our findings suggest the influence of plant neighbours can range from the nearest individual neighbour to the entire plant neighbourhood. Such fine-scale associational effects are fundamentally important for understanding intricate plant-herbivore interactions, and ecologically important by potentially having knock-on effects on plant survival, in turn influencing plant community structure.

Introduction

The assemblage of plants in a patch forms a neighbourhood. This plant neighbourhood can influence the susceptibility of an individual plant to being found and eaten by herbivores, known as an associational effect [1–5]. Associational effects are often a consequence of herbivores seeking high-quality ‘palatable’ patches and avoiding low-quality patches [6–9] to maximise their foraging efficiency. For example, when herbivores select among patches, a focal plant in a high-quality patch is more likely to be visited by a herbivore hence more susceptible to being consumed, known as associational plant susceptibility [10–13]. In contrast, a focal plant in a low-quality patch (e.g., a high density of low nutrient, structurally, and/or chemically defended species) that is avoided by herbivores will be safe from being eaten, known as associational plant refuge [1,2,14,15].

While associational effects of plant patches are widely recognised, the boundaries that define a patch are often nebulous. Generally, ‘patch’ is used as a short-cut term recognising a sphere-of-influence that neighbouring plants may have on a focal plant [5]. To date, research into the influence of plant patches on focal plant susceptibility to herbivores has largely focused on maximal spheres-of-influence, exploring the effects of the type of plant neighbours and how far they can be from focal plants while still exerting an effect. For example, susceptibility of European beech, Fagus sylvatica, to deer browsing decreases with greater distance from, and lower densities of high-quality neighbours (sycamore maple, Acer pseudoplatanus) [16]. Similarly, focal heather, Calluna vulgaris, are less susceptible to browsing by both red deer, Cervus elaphus, and sheep, Ovis aries, when further from higher-quality neighbours [12]. However, when considering the influence a patch may have on susceptibility of focal plants to herbivores, the other end of the spectrum has been overlooked: how small can a neighbourhood be, yet still exert an effect?

Selective foraging by herbivores occurs across multiple spatial scales and is hierarchical in nature [17,18]. These spatial scales—from plant communities, to plant neighbourhoods within these communities, to plants within neighbourhoods, and even parts within plants—are effectively nested patches. But the boundaries defining a patch around a focal plant can be ambiguous. A continuum of influence likely exists in shaping focal plant susceptibility to herbivores, from the closest single neighbour to an entire plant neighbourhood. As the number of neighbours in direct proximity to a focal plant increases, associational effects are expected to strengthen, for a range of reasons. More neighbours could change absolute patch quality, convey more information about that quality (e.g., through visual or olfactory cues [19,20]), impose greater costs in terms of search time, and/or provide greater physical or visual obstruction to focal plants from herbivores. Whether single plant neighbours can elicit associational effects, altering the susceptibility of focal plants to herbivores, has been largely explored.

Testing the influence of single plant neighbours on focal plant susceptibility to herbivores has fundamental significance by advancing our understanding of intricate plant-herbivore interactions. Understanding associational effects at these finer spatial scales also has broader ecological significance because, by impacting focal plant survival, plant neighbours may have knock-on effects influencing plant community structure.

Here our first aim was to test whether single neighbours can influence if a focal plant is visited and eaten by a mammalian herbivore. In deciding whether to visit or avoid an area, if herbivores respond to food quality at the scale of a couple of plants, then a single high- or low-quality neighbour should increase or delay time to first visit by a herbivore, influencing a focal plant’s vulnerability to being eaten (Fig 1a, 1b, 1c). Our second aim was to test whether any refuge effect is strengthened by more, low-quality neighbours in direct proximity to a focal plant (Fig 1a, 1b, 1d). For this aim, we focused on one of our species pairs—the most relevant to associational plant refuge.

In our study, the herbivore we used was a browser/mixed feeder, the swamp wallaby (Wallabia bicolor) [21–23], free-ranging in native eucalypt woodland. The swamp wallaby is an Australian macropod (mean body weight female 15 kg, male 19 kg; [24], abundant, and ecologically equivalent to many mammalian herbivores in ecosystems around the world, such as various species of deer in Asia, Europe and America, and antelope and elephant in Africa and Asia. Like these species, swamp wallabies are abundant and a key driver of plant community dynamics [25–27].

To select a low-quality plant species, we conducted haphazard transects in search for a plant that displayed no signs of browsing damage. From these transects we selected Boronia pinnata, a small, highly odorous native shrub species. This species has been previously shown to be avoided by swamp wallabies within the study site [28]. At the study site, B. pinnata plants generally grow alone, and not in clumps with other B. pinnata. We selected two eucalypt species (Eucalyptus punctata and Corymbia gummifera) as higher-quality plants. These were both a known food source of wallabies at the study site (based on [19] and on unpublished work by [29] and [30]). We confirmed the quality of these plants to wallabies as part of the experiment

Materials and methods

Study site

Experiments were run in Ku- ring- gai Chase National Park, New South Wales, Australia (33°41′33″S, 151°08′44″E) from May 2021 to November 2022. All experimental sites were in Eucalyptus woodland dominated by scribbly gum (Eucalyptus haemastoma), red bloodwood (Corymbia gummifera), yellow bloodwood (Corymbia eximia), and grey gum (Eucalyptus punctata, our focal plant species) with complex shrub and ground vegetation layers. Animal ethics approval was granted by the University of Sydney’s Animal Ethics Committee (protocol number 2022/2196) and scientific license (SL102186) was obtained from New South Wales Office of Environment and Heritage to undertake the fieldwork.

Aim 1: Does a single plant neighbour elicit an associational effect?

Using these three species, we tested three paired treatments (Pair, 3 levels) using one plant of each of two species adjacent to one another, and one pair per plot. One treatment paired an E. punctata seedling with a C. gummifera seedling (n = 17 plots). Another paired an E. punctata seedling with a B. pinnata plant (n = 23 plots). The third treatment paired a C. gummifera seedling with a B. pinnata plant (n = 10 plots). The smaller sample size for the C. gummifera and B. pinnata combination was due to limited availability of C. gummifera seedlings. All three pairs were deployed in a completely randomised design at our study site (total n = 50 plots). We placed plots a minimum of 30 m apart, so one plot could not be seen from another. We used naturally occurring B. pinnata shrubs growing at the site (375 ± 19 mm). Seedlings of E. punctata and C. gummifera were of similar height (370 ± 25 mm), planted in soil in tube stock pots (10 cm diam), and supplied by one nursery (Plants Plus Cumberland Forest Nursery, West Pennant Hills, Sydney).

For the treatment pairing E. punctata and C. gummifera, seedlings were placed 20 cm apart at either end of a clear tub (Fig 2a), allowing easy identification of which species was browsed in video footage For treatments involving B. pinnata, the eucalypt seedling was positioned at one end of a clear plastic tub, with the ‘free’ end of the tub placed next to a B. pinnata shrub, again 20 cm apart. A seedling pot with soil was included at the B. pinnata end of the tub to account for any effects of open soil (Fig 2b). The side on which each species was presented within each treatment was randomised by coin toss.

At each Pair we set one motion-triggered infra-red trail camera (ScoutGuard SG560K or SG2060-K; Professional Trapping Supplies Pty Ltd, Molendinar, QLD, Australia) fastened to a wooden stake (camera height = 0.7 m) and placed directly over the pair of plants. Cameras were set to record for 1- minute with instant re-trigger. These videos were used to quantify the time to first visit a plot (days) by a wallaby (hereafter time to 1^st visit), and time to first browse a plant (days) within a plot by a wallaby (hereafter time to 1^st browse). If browsed, we visually estimated the percentage of foliage consumed (% intervals of 0, 25, 50, 75 and 100%) from each plant as seen on camera.

Aim 2: Does a neighbourhood of plants elicit stronger associational effects?

Here, we tested whether a refuge effect is strengthened by more low-quality neighbours in direct proximity to a focal plant, using the high-quality E. punctata and low-quality B. pinnata Pair. All plants, including B. pinnata, were in soil in pots (25 cm diam), and obtained from one nursery (Plants Plus Cumberland Forest Nursery, West Pennant Hills, Sydney).

We compared four Treatments (n = 16 per Treatment); a single focal E. punctata seedling next to a single B. pinnata (single neighbour, Fig 3a), a single focal E. punctata surrounded by five B. pinnata (neighbourhood, Fig 3b), a single focal E. punctata with no neighbours as an untreated control (Fig 3c), and a single focal E. punctata surrounded by five pots filled with soil as a procedural control (Fig 3d). All four Treatments were deployed at our study site in plots at least 30 m apart in a completely randomised design (total n = 64 plots). In the single neighbour treatment, B. pinnata was placed 50 cm away from the focal E. punctata. In the neighbourhood treatment, B. pinnata plants, and in the procedural control, pots with soil, were evenly spaced around the focal E. punctata at a 50 cm radius. This spacing ensured that B. pinnata did not completely visually obscure or physically obstruct wallabies’ access to the focal E. punctata seedlings.

We calculated a visibility score for the single focal plant per plot, to be used in later analyses as a potential explanation of any observed associational refuge effects. Ordinal scores using visual estimates were used to determine how much of the focal E. punctata seedling could be seen from 1 m distance at an average adult swamp wallaby height of 70 cm [31]; 0 = 0%, 1 = 1–25%, 2 = 26–50%, 3 = 51–75%, 4 = 76–100%; where percentages refer to the proportion of the focal E. punctata seedling visible. Visibility point scores were taken at 10 evenly spaced locations around each seedling. Point scores were later converted to midpoint values and an average used as a single visibility score.

At each plot we set a motion-triggered infra-red trial camera (ScoutGuard SG560K or SG2060-K; Professional Trapping Supplies Pty Ltd, Molendinar, QLD, Australia). The camera was fastened to a wooden stake (camera height = 0.7 m, distance to seedling = 1.5 m) at an approximate 45° angle towards the plants (Fig 3c and 3d). Cameras were set to record for 1-minute with instant re-trigger. As per the single neighbour trial, these videos were used to quantify the time to 1^st visit a plot (by a wallaby, in days), and time to 1^st browse a focal E. punctata (by a wallaby, in days) within a plot. If browsed, we estimated the percentage of foliage consumed from the E. punctata seedling as for the single neighbour trial. We ran this experiment for 9 weeks, which was the time it took for at least 90% of plots of each Treatment to be visited by wallabies.

Statistical analysis

Aim 1: Does a single plant neighbour elicit an associational effect?.

We tested effect of neighbours in three ways: time to 1st visit a plot, time to 1^st browse a focal plant, and % of focal plant browsed. To test whether there was an effect of Pair on time to 1st visit we used a Cox proportional-hazards model (‘survival’ package [33]) to model ‘survival’ (where failure is based on time to 1st visit a plot) as a function of Pair (3 levels, fixed factor). This model takes into account right-censored data (i.e., if a plot was not visited within the experimental timeframe). Data were censored for any un-visited plots (i.e., plots where no visit occurred during the study). The model was also used to calculate hazard ratios (HR) (exp(coef)) between Pairs for time to 1^st visit for the three pairwise comparisons.

To test whether there was an effect of neighbour on time to 1^st browse a focal plant (either E. punctata or C. gummifera), we used a mixed effects Cox proportional hazard model to model ‘survival’ (where failure is based on time to 1^st browse) as a function of neighbour within Pair (fixed factor, 4 levels). There were 4 levels because there were four focal plant—neighbour combinations: focal E. punctata with neighbour C. gummifera; focal C. gummifera with neighbour E. punctata; focal E. punctata with neighbour B. pinnata (never browsed); and focal C. gummifera with neighbour B. pinnata (never browsed).We included Plot in the model as a random factor to account for two focal plants (hence possible covariance for browsing) in the E. punctata–C. gummifera combination

The model was: Survival (time to 1^st browse focal plant) ~ neighbour within Pair + (1|Plot).

This model takes into account right-censored data. Data were censored for any plots visited but plants un-browsed. Plots that were not visited were excluded. The model was also used to calculate pairwise hazard ratios between focal species within a Pair.

To compare foliage browsed of focal E. punctata between the E. punctata–C. gummifera and E. punctata–B. pinnata combinations, and on focal C. gummifera between the C. gummifera–E. punctata and C. gummifera–B. pinnata combinations, we ran two beta regressions (‘betareg’ package [34]) with a logit link function. Percentage browsed data for a given species (E. punctata or C. gummifera) was included if a plot was visited and at least one plant within the plot was browsed. We excluded data if neither plant was browsed (2 out of 35 valid visits).

To confirm that B. pinnata was a low-quality species, and E. punctata and C. gummifera were higher-quality species, we compared percentage foliage browsed of each species within a Pair at first browsing visit. We ran a paired t-test for each of the three Pairs. Percentage browsed data for both species was included if a plot was visited and at least one plant within the plot was browsed. We excluded data if neither plant was browsed (2 out of 35 valid visits). Data met assumptions for normality and heterogeneity of variance. All statistical analysis was conducted in R (version 4.2.0; R Core Team, 2022)). Data were plotted using ‘ggplot2’ [32].

Aim 2: Does a neighbourhood of plants elicit stronger associational effects?.

To test whether there was an effect of Treatment on time to 1st visit we used a Cox proportional-hazards model (‘survival’ package [33]) to model ‘survival’ (failure as time to 1st visit a plot) as a function of Treatment (fixed factor, 4 levels), taking into account right-censored data (i.e., un-visited plots). Pairwise hazard ratios were calculated as for Aim 1.

To test whether there was an effect of Treatment on time to 1^st browse a focal E. punctata, we used a Cox proportional hazard model to model ‘survival’ (failure as time to 1^st browse) as a function of Treatment (fixed factor, 4 levels). Plots that were not visited were excluded but data were censored for any plots visited but focal E. punctata un-browsed. Pairwise hazard ratios were calculated (as for Aim 1) between Treatments.

To test whether there was a difference in percentage of focal E.punctata foliage consumed at first browsing visit between Treatments we used a beta regression as a function of Treatment with a logit link function. We excluded data if the focal plant was visited, but not browsed (3 out of 53 valid visits).

To test for differences in focal E. punctata visibility among Treatments we used a one-way ANOVA. Data met assumptions for normality and heterogeneity of variance. If significant, we compared visibility among treatments by performing multiple pairwise comparisons with the Tukey–Kramer adjustment (indicated by alphabetical superscript in figure) (‘emmeans’ package [35]). All statistical analysis was conducted in R (version 4.2.0; R Core Team, 2022)). Data were plotted using ‘ggplot2’ [32].

Results

Aim 1: Does a single plant neighbour elicit an associational effect?

Time to 1st visit differed significantly as a function of Pair (LR $χ_{2}^{2}$ = 13.17, p = 0.001, Fig 4a). Pairwise hazard ratios showed that the combination of E. punctata and C. gummifera (both high-quality species), was 5.2 times more likely to be visited than the combination of E. punctata and B. pinnata (z = 3.55, p < 0.001) (high-quality and low-quality species respectively) and 4.2 times more likely to be visited the combination of C. gummifera and B. pinnata (z = 2.46, p = 0.01) (high-quality and low-quality species respectively) (Table 1). The E. punctata–B. pinnata and C. gummifera–B. pinnata combinations were equally likely to be visited (z = −0.39, p = 0.67).

Table 1. Pairwise comparisons between time to 1st visit a Pair. Hazard ratios indicate the likelihood of the first listed Pair being visited compared to the second Pair. If hazard ratios are significantly higher than 1, then the first listed Pair is significantly more likely to be visited than the second.

Pairwise comparison	Hazard ratio	z	p-value
E. punctata and C. gummifera vs E. punctata and B. pinnata	5.17	3.55	<0.001
E. punctata and C. gummifera vs C. gummifera and B. pinnata	4.15	2.46	0.01
E. punctata and B. pinnata vs C. gummifera and B. pinnata	0.81	−0.39	0.67

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Time to 1st browse a focal species differed significantly as a function of neighbour within Pair ( $χ_{3}^{2}$ = 8.34, p = 0.04, Fig 4b). Only E. punctata and C. gummifera (both high-quality species) were considered as focal species because B. pinnata (low-quality) was never browsed. Pairwise hazard ratios showed that focal E. punctata when next to one C. gummifera was 15.9 times more likely to be browsed than if next to one B. pinnata (z = 2.29, p = 0.02) (Table 2). Similarly, focal C. gummifera when next to one E. punctata was 35.9 times more likely to be browsed than if next to one B. pinnata (z = 2.27, p = 0.02) (Table 2).

Table 2. Pairwise comparisons between time to 1^st browse a focal plant as a function of neighbour within Pair (noted outside the brackets). Hazard ratios indicate the likelihood that a focal species (in first listed Pair) will be browsed versus another (in second listed Pair). If hazard ratios are significantly higher than 1, than the first listed focal species is significantly more likely to be browsed than the second listed focal species.

Pairwise comparison	Hazard ratio	z	p-value
E. punctata (neighbour C. gummifera) vs E. punctata (neighbour B. pinnata)	15.98	2.29	0.02
C. gummifera (neighbour E. punctata) vs C. gummifera (neighbour B. pinnata)	35.88	2.27	0.02
E. punctata (neighbour C. gummifera) vs C. gummifera (neighbour E. punctata)	1.25	0.58	0.26
E. punctata (neighbour C. gummifera) vs C. gummifera (neighbour B. pinnata)	44.99	2.41	0.02
C. gummifera (neighbour E. punctata) vs E. punctata (neighbour B. pinnata)	12.74	2.11	0.03
E. punctata (neighbour B. pinnata) vs C. gummifera (neighbour B. pinnata)	2.81	0.65	0.51

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When comparing percentage foliage browsed on focal E. punctata between Pairs, wallabies consumed significantly more when E. punctata was next to C. gummifera (another high-quality species) than when it was next to B. pinnata (a low-quality species) ( $χ_{1}^{2}$ = 21.77, p < 0.001, Fig 5). Similarly, when comparing percentage foliage browsed on focal C. gummifera between Pairs, wallabies consumed significantly more when C. gummifera was next to E. punctata (high-quality) than when it was next to B. pinnata ( ( $χ_{1}^{2}$ = 8.52 p = 0.004, Fig 5).

Fig 5 — Boxplots shows median, 1st and 3rd quartile, and maximum and minimum values (within 1.5 × IQR). Raw data points are displayed as jittered full black points. Asterisks indicate significant differences for each focal plant species.

When comparing percentage foliage browsed from both species within a Pair, wallabies browsed significantly more E. punctata than C. gummifera when these two high-quality species were paired together (t = −2.64, df = 15, P = 0.02, Fig 6a). When E. punctata was paired with B. pinnata (high vs. low-quality), wallabies browsed significantly more E. punctata (t = −7.37, df = 11, P < 0.001, Fig 6b). Similarly, when C. gummifera was paired with B. pinnata (high vs. low-quality), wallabies browsed significantly more C. gummifera (t = −5.72, df = 14, P < 0.001, Fig 6c).

Fig 6 — Boxplots shows median, 1st and 3rd quartile, and maximum and minimum values (within 1.5 × IQR). Raw data points are displayed as jittered full black points. Asterisks indicate significant difference. Panel a) shows *E. punctata* and *C. gummifera*, b) shows *E. punctata* and *B. pinnata*, and c) shows *C. gummifera* and *B. pinnata.*

Aim 2: Does a neighbourhood of plants elicit stronger associational effects?

Time to 1^st visit differed significantly as a function of Treatment (LR $χ_{3}^{2}$ = 21.65, P < 0.001, Fig 7a). Pairwise hazard ratios show that E. punctata (high-quality) with no neighbours (untreated control) were 2.8 times more likely to be visited than E. punctata with one B. pinnata (low-quality) neighbour (z = 2.50, P = 0.01), 3.0 times more likely to be visited than E. punctata with five B. pinnata neighbours (z = 2.74, P = 0.006). E. punctata were equally likely to be visited by wallabies when surrounded by five or one B. pinnata neighbour (z = 0.21, P = 0.84). There was no “pot” effect, as E. punctata with no neighbours (untreated control) were equally likely to be visited as E. punctata with five pots with soil (procedural control) (z = 0.22, P = 0.59) (Table 3).

Table 3. Pairwise comparisons between time to 1^st visit a Treatment. Hazard ratios indicate the likelihood of the first listed Treatment being visited compared to the second Treatment. If hazard ratios are significantly higher than 1, than the first listed Treatment is significantly more likely to be visited than the second.

Pairwise comparison	Hazard ratio	z	p-value
Untreated control (no neighbours) vs B. pinnata x 1 (Single neighbour)	2.75	2.50	0.01
Untreated control (no neighbours) vs B. pinnata × 5 (Neighbourhood)	2.98	2.74	0.006
B. pinnata x 1 (Single neighbour) vs B. pinnata × 5 (Neighbourhood)	1.08	0.21	0.84
Untreated control (no neighbours) vs Procedural control (pots with soil)	1.24	0.22	0.59
Procedural control (pots with soil) vs B. pinnata x 1 (Single neighbour)	3.40	3.06	0.002
Procedural control (pots with soil) vs B. pinnata × 5 (Neighbourhood)	3.68	3.34	< 0.001

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Time to 1^st browse differed significantly as a function of treatment (LR χ 3 2 = 21.65, P < 0.0001, Fig 7b). Pairwise hazard ratios show that E. punctata (high-quality) with no neighbours (untreated control) were 2.5 times more likely to be browsed than E. punctata with one B. pinnata (low-quality) neighbour (z = 2.16, P = 0.03), and 4.5 times more likely to be browsed than E. punctata with five B. pinnata neighbours (z = 3.40, P < 0.001). E. punctata were equally likely to be browsed by wallabies when surrounded by one or five B. pinnata neighbour (z = 1.34, P = 0.18). There was no “pot” effect, as E. punctata with no neighbours (untreated control) were equally likely to be browsed as E. punctata with one pot with soil (procedural control) (z = 1.22, P = 0.39) (Table 4). If browsed, the percentage of E. punctata foliage browsed was high (mean 87%) and did not differ between Treatments (LR $χ_{3}^{2}$ = 3.60, P = 0.31).

Table 4. Pairwise comparisons between time to 1^st browse a focal E. punctata as a function of Treatment. Hazard ratios indicate the likelihood of focal E. punctata being browsed within the first listed Treatment compared to E. punctata being browsed within the second listed Treatment. If hazard ratios are significantly higher than 1, than a E. punctata within the first listed Treatment is significantly more likely to be browsed than a E. punctata within the second listed Treatment.

Pairwise comparison	Hazard ratio	z	p-value
Untreated control (no neighbours) vs B. pinnata x 1 (Single neighbour)	2.49	2.16	0.03
Untreated control (no neighbours) vs B. pinnata × 5 (Neighbourhood)	4.49	3.40	< 0.001
B. pinnata x 1 (Single neighbour) vs B. pinnata × 5 (Neighbourhood)	1.80	1.34	0.18
Untreated control (no neighbours) vs Procedural control (pots with soil)	1.40	1.22	0.39
Procedural control (pots with soil) vs B. pinnata x 1 (Single neighbour)	3.61	2.95	0.003
Procedural control (pots with soil) vs B. pinnata × 5 (Neighbourhood)	6.31	4.16	< 0.001

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Visibility of focal E. punctata differed significantly as a function of Treatment (F_{3, 57} = 29.01, p < 0.0001, Fig 8). Visibility was lowest when surrounded by five B. pinnata but the visibility score was still high (mean 83%).

Discussion

Our results demonstrate that single neighbours can elicit associational effects. In deciding whether to visit or avoid a pair, wallabies responded to a single plant neighbour, in turn influencing vulnerability of a focal plant to being browsed. Specifically, pairs of one high-quality E. punctata or C. gummifera seedling next to a single low-quality B. pinnata plant were visited and subsequently browsed later by wallabies than a pair of E. punctata and C. g ummifera seedlings. In delaying time to first visit a pair, a single low-quality neighbour influences herbivore behaviour at a crucial, early stage in the foraging process, when investment is low and hence easier to alter [36,37]. Our results also show that later stages of the foraging process were shaped by single low-quality neighbours, with time to first browse delayed and amount eaten lower for both E. punctata and C. gummifera seedlings when next to B. pinnata then when next to each other. These results are the first to demonstrate associational refuge effects of neighbouring plants occurring at such fine—single neighbour—spatial scales.

Contrary to our predictions (from Fig 1), associational refuge effects were not strengthened by having more low-quality neighbours. Specifically, the delay in wallabies visiting a plot and subsequently browsing a focal E. punctata seedling was equivalent whether it was next to a single B. pinnata plant or surrounded by a neighbourhood of five plants. Given wallabies can use odour cues from afar to judge plant quality [28,38–41] and quantity [19], it is perhaps not surprising that the slight reduction in visibility of E. punctata caused by five rather than one B. pinnata had no impact on foraging. Nevertheless, although a single B. pinnata plant may have the same effect on wallabies’ ultimate foraging choice as five plants, having five B. pinnata plants would likely emit a stronger quantitative odour cue that could be detected from greater distances, potentially influencing how far away wallabies make their foraging decisions, rather than changing their choice itself, or possibly masking the odour of focal plants altogether. Regardless, here, wallabies seem to have avoided B. pinnata (hence adjacent E. punctata) irrespective of quantity. This implies that at finer spatial scales, the quantity of low-quality neighbours may not be as important in shaping wallaby, and possibly other mammalian herbivore foraging decisions than at larger spatial scales, where the quantity and proximity of low-quality neighbours does matter in influencing associational effect strength [16].

For the single neighbour experiment (Aim 1, which tested whether a single plant neighbour elicits an associational effect), high-quality focal plants were browsed less by wallabies when next to a single low-quality neighbour. In contrast, in the neighbourhood experiment (Aim 2, which tested whether multiple neighbours elicit stronger associational effects), if browsed, high-quality focal E. punctata were almost always completely consumed regardless of Treatment. This difference in browsing severity may reflect a difference in focal E. punctata quality [8,42] and/or a difference in B.pinnata quality between the two experiemnts. Although from the same nursery, E. punctata seedlings were purchased at different times within a year and possibly grown under different conditions. Similarly, B. pinnata was naturally occurring in Aim 1 but nursery-grown in Aim 2. Different abiotic growing conditions could affect nutrient and plant secondary metabolite concentrations (e.g. [43]).

Our study highlights that individual plant neighbours can indeed exert significant associational effects, comparable in strength to those observed from a neighbourhood of plants. In demonstrating the influence of single plant neighbours on herbivore foraging decisions, our study reveals a nuanced plant-herbivore interaction of fundamental importance. While traditionally a ‘patch’ refers to a broad sphere-of-influence neighbouring plants have on a focal plant, our findings suggest the influence of plant neighbours ranges from the nearest individual neighbour to the entire plant neighbourhood.

These subtle and more localised associational effects could have important ecological implications. Selective browsing by herbivores can play a pivotal role in shaping ecosystems [44,45]. Thus, by impacting focal plant susceptibility to herbivores, even single plant neighbours may have knock-on effects influencing plant community structure, and indirectly impact other organisms in these communities via a trophic cascade [46–48].

Supporting information

S1 File. Supplementary data and code files.

(ZIP)

pone.0330572.s001.zip^{(16.1KB, zip)}

Data Availability

The datasets generated during and/or analysed during the current study are available on figshare (https://doi.org/10.6084/m9.figshare.29525723).

Funding Statement

Authors CM and PB acknowledge funding from the Australian Research Council (grant number DP190101441).

References

1.Tahvanainen JO, Root RB. The influence of vegetational diversity on the population ecology of a specialized herbivore, Phyllotreta cruciferae (Coleoptera: Chrysomelidae). Oecologia. 1972;10(4):321–46. doi: 10.1007/BF00345736 [DOI] [PubMed] [Google Scholar]
2.Atsatt PR, O’dowd DJ. Plant defense guilds. Science. 1976;193(4247):24–9. doi: 10.1126/science.193.4247.24 [DOI] [PubMed] [Google Scholar]
3.Milchunas DG, Noy‐Meir I. Grazing refuges, external avoidance of herbivory and plant diversity. Oikos. 2002;99(1):113–30. doi: 10.1034/j.1600-0706.2002.990112.x [DOI] [Google Scholar]
4.Root RB. Organization of a Plant‐Arthropod Association in Simple and Diverse Habitats: The Fauna of Collards (Brassica Oleracea). Ecological Monographs. 1973;43(1):95–124. doi: 10.2307/1942161 [DOI] [Google Scholar]
5.Underwood N, Inouye BD, Hambäck PA. A conceptual framework for associational effects: when do neighbors matter and how would we know?. Q Rev Biol. 2014;89(1):1–19. doi: 10.1086/674991 [DOI] [PubMed] [Google Scholar]
6.Emlen JM. The Role of Time and Energy in Food Preference. The American Naturalist. 1966;100(916):611–7. doi: 10.1086/282455 [DOI] [Google Scholar]
7.MacArthur RH, Pianka ER. On Optimal Use of a Patchy Environment. The American Naturalist. 1966;100(916):603–9. doi: 10.1086/282454 [DOI] [Google Scholar]
8.Champagne E, Moore BD, Côté SD, Tremblay J. Intraspecific variation in nutritional traits of neighbouring plants generates a continuum of associational effects. J Vegetation Science. 2020;31(5):920–33. doi: 10.1111/jvs.12914 [DOI] [Google Scholar]
9.Miller AM, McArthur C, Smethurst PJ. Spatial scale and opportunities for choice influence browsing and associational refuges of focal plants. Journal of Animal Ecology. 2009;78(6):1134–42. [DOI] [PubMed] [Google Scholar]
10.Bergman M, Iason GR, Hester AJ. Feeding patterns by roe deer and rabbits on pine, willow and birch in relation to spatial arrangement. Oikos. 2005;109(3):513–20. doi: 10.1111/j.0030-1299.2005.13794.x [DOI] [Google Scholar]
11.Thomas CD. Butterfly larvae reduce host plant survival in vicinity of alternative host species. Oecologia. 1986;70(1):113–7. doi: 10.1007/BF00377118 [DOI] [PubMed] [Google Scholar]
12.Palmer SCF, Hester AJ, Elston DA, Gordon IJ, Hartley SE. The perils of having tasty neighbors: grazing impacts of large herbivores at vegetation boundaries. Ecology. 2003;84(11):2877–90. doi: 10.1890/02-0245 [DOI] [Google Scholar]
13.Courant S, Fortin D. Foraging decisions of bison for rapid energy gains can explain the relative risk to neighboring plants in complex swards. Ecology. 2010;91(6):1841–9. doi: 10.1890/09-1226.1 [DOI] [PubMed] [Google Scholar]
14.Hambäck PA, Inouye BD, Andersson P, Underwood N. Effects of plant neighborhoods on plant-herbivore interactions: resource dilution and associational effects. Ecology. 2014;95(5):1370–83. doi: 10.1890/13-0793.1 [DOI] [PubMed] [Google Scholar]
15.Wang L, Wang D, Bai Y, Huang Y, Fan M, Liu J, et al. Spatially complex neighboring relationships among grassland plant species as an effective mechanism of defense against herbivory. Oecologia. 2010;164(1):193–200. doi: 10.1007/s00442-010-1676-3 [DOI] [PubMed] [Google Scholar]
16.Holík J, Janík D, Hort L, Adam D. Neighbourhood effects modify deer herbivory on tree seedlings. Eur J Forest Res. 2021;140(2):403–17. doi: 10.1007/s10342-020-01339-8 [DOI] [Google Scholar]
17.Senft RL, Coughenour MB, Bailey DW, Rittenhouse LR, Sala OE, Swift DM. Large Herbivore Foraging and Ecological Hierarchies. BioScience. 1987;37(11):789–99. doi: 10.2307/1310545 [DOI] [Google Scholar]
18.Johnson DH. The Comparison of Usage and Availability Measurements for Evaluating Resource Preference. Ecology. 1980;61(1):65–71. doi: 10.2307/1937156 [DOI] [Google Scholar]
19.Finnerty PB, Stutz RS, Price CJ, Banks PB, McArthur C. Leaf odour cues enable non-random foraging by mammalian herbivores. J Anim Ecol. 2017;86(6):1317–28. doi: 10.1111/1365-2656.12748 [DOI] [PubMed] [Google Scholar]
20.Stutz RS, Banks PB, Proschogo N, McArthur C. Follow your nose: leaf odour as an important foraging cue for mammalian herbivores. Oecologia. 2016;182(3):643–51. doi: 10.1007/s00442-016-3678-2 [DOI] [PubMed] [Google Scholar]
21.Hollis C, Hollis C, Robertshaw J, Robertshaw J, Harden R, Harden R. Ecology of the Swamp Wallaby (Wallabia-Bicolor) in Northeastern New-South-Wales .1. Diet. Wildl Res. 1986;13(3):355. doi: 10.1071/wr9860355 [DOI] [Google Scholar]
22.Osawa R. Feeding Strategies of the Swamp Wallaby, Wallabia Bicolor, on North Stradbroke Island, Queensland. I: Composition of Diets. Wildl Res. 1990;17(6):615. doi: 10.1071/wr9900615 [DOI] [Google Scholar]
23.Di Stefano J, Newell GR. Diet Selection by the Swamp Wallaby (Wallabia bicolor): Feeding Strategies under Conditions of Changed Food Availability. J Mammal. 2008;89(6):1540–9. doi: 10.1644/07-mamm-a-193.1 [DOI] [Google Scholar]
24.Garnick S, Di Stefano J, Elgar MA, Coulson G. Do body size, diet type or residence time explain habitat use in a vertebrate herbivore community?. Aust J Zool. 2016;64(2):91. doi: 10.1071/zo15061 [DOI] [Google Scholar]
25.Dexter N, Hudson M, James S, MacGregor C, Lindenmayer DB. Unintended Consequences of Invasive Predator Control in an Australian Forest: Overabundant Wallabies and Vegetation Change. PLoS ONE. 2013;8(8):e69087. doi: 10.1371/journal.pone.0069087 [DOI] [PMC free article] [PubMed] [Google Scholar]
26.Di Stefano J, Butler K, Sebire I, Fagg P. Mammalian browsing impact on regenerating Eucalyptus seedlings in a large commercially managed native forest estate. New Forests. 2008;37(2):197–211. doi: 10.1007/s11056-008-9117-4 [DOI] [Google Scholar]
27.Morgan JW. Overabundant native herbivore impacts on native plant communities in south‐eastern Australia. Eco Management Restoration. 2021;22(S1):9–15. doi: 10.1111/emr.12437 [DOI] [Google Scholar]
28.Finnerty PB, Possell M, Banks PB, Orlando CG, Price CJ, Shrader AM, et al. Olfactory misinformation provides refuge to palatable plants from mammalian browsing. Nat Ecol Evol. 2024;8(4):645–50. doi: 10.1038/s41559-024-02330-x [DOI] [PMC free article] [PubMed] [Google Scholar]
29.Nettle J. Investigating the Impact of Plant Odour and Atmospheric Pollution on the Foraging of Mammalian Herbivores. The University of Sydney. 2018. [Google Scholar]
30.Guest L. How do neighbours at different spatial scales affect plant vulnerability to being eaten?. The University of Sydney. 2021. [Google Scholar]
31.Van Dyck S, Gynther I, Baker A. Field companion to the mammals of Australia. London: New Holland Publishers. 2013. [Google Scholar]
32.Wickham H, Chang W, Wickham MH. Package ‘ggplot2’. Create elegant data visualisations using the grammar of graphics. 2016;2(1):1–189.
33.Therneau M. Package ‘coxme’. 2015. [Google Scholar]
34.Cribari-Neto F, Zeileis A. Beta regression in R. Journal of statistical software. 2010;34:1–24. [Google Scholar]
35.Lenth R, Lenth MR. Package ‘lsmeans’. The American Statistician. 2018;34(4):216–21. [Google Scholar]
36.Price C, McArthur C, Norbury G, Banks P. Olfactory misinformation: creating “fake news” to reduce problem foraging by wildlife. Frontiers in Ecol & Environ. 2022;20(9):531–8. doi: 10.1002/fee.2534 [DOI] [Google Scholar]
37.Price CJ, Bytheway JP, Finnerty PB, Grant LS, Masani S, Orlando CG, et al. Altering reality – sensory tactics to manage wildlife and conserve threatened species. Australian Zoologist. 2024;43(4):510–7. doi: 10.7882/az.2024.010 [DOI] [Google Scholar]
38.Bedoya-Pérez MA, Isler I, Banks PB, McArthur C. Roles of the volatile terpene, 1,8-cineole, in plant-herbivore interactions: a foraging odor cue as well as a toxin?. Oecologia. 2014;174(3):827–37. doi: 10.1007/s00442-013-2801-x [DOI] [PubMed] [Google Scholar]
39.Finnerty PB, McArthur C, Banks P, Price C, Shrader AM. The Olfactory Landscape Concept: A Key Source of Past, Present, and Future Information Driving Animal Movement and Decision-making. Bioscience. 2022;72(8):745–52. doi: 10.1093/biosci/biac039 [DOI] [PMC free article] [PubMed] [Google Scholar]
40.Finnerty PB, Shrader AM, Banks PB, Schmitt MH, McArthur C. Odour information enables patch choice by mammalian herbivores from afar, leading to predictable plant associational effects. Functional Ecology. 2024;38(11):2478–92. doi: 10.1111/1365-2435.14665 [DOI] [Google Scholar]
41.McArthur C, Finnerty PB, Schmitt MH, Shuttleworth A, Shrader AM. Plant volatiles are a salient cue for foraging mammals: elephants target preferred plants despite background plant odour. Animal Behaviour. 2019;155:199–216. doi: 10.1016/j.anbehav.2019.07.002 [DOI] [Google Scholar]
42.Moore BD, Lawler IR, Wallis IR, Beale CM, Foley WJ. Palatability mapping: a koala’s eye view of spatial variation in habitat quality. Ecology. 2010;91(11):3165–76. doi: 10.1890/09-1714.1 [DOI] [PubMed] [Google Scholar]
43.O’Reilly-Wapstra JM, Potts BM, McArthur C, Davies NW. Effects of nutrient variability on the genetic-based resistance of Eucalyptus globulus to a mammalian herbivore and on plant defensive chemistry. Oecologia. 2005;142(4):597–605. doi: 10.1007/s00442-004-1769-y [DOI] [PubMed] [Google Scholar]
44.Gill RMA. The impact of deer on woodlands: the effects of browsing and seed dispersal on vegetation structure and composition. Forestry. 2001;74(3):209–18. doi: 10.1093/forestry/74.3.209 [DOI] [Google Scholar]
45.Western D, Maitumo D. Woodland loss and restoration in a savanna park: a 20‐year experiment. African Journal of Ecology. 2004;42(2):111–21. doi: 10.1111/j.1365-2028.2004.00506.x [DOI] [Google Scholar]
46.Fortin D, Beyer HL, Boyce MS, Smith DW, Duchesne T, Mao JS. Wolves influence elk movements: behavior shapes a trophic cascade in yellowstone national park. Ecology. 2005;86(5):1320–30. doi: 10.1890/04-0953 [DOI] [Google Scholar]
47.Foster CN, Barton PS, Lindenmayer DB. Effects of large native herbivores on other animals. Journal of Applied Ecology. 2014;51(4):929–38. doi: 10.1111/1365-2664.12268 [DOI] [Google Scholar]
48.Foster CN, Barton PS, Wood JT, Lindenmayer DB. Interactive effects of fire and large herbivores on web-building spiders. Oecologia. 2015;179(1):237–48. doi: 10.1007/s00442-015-3323-5 [DOI] [PubMed] [Google Scholar]

PLoS One. doi: 10.1371/journal.pone.0330572.r001

Decision Letter 0

Showkat Ganie

26 May 2025

PONE-D-25-16194Fine-scale associational effects: single plant neighbours can alter susceptibility of focal plants to herbivoresPLOS ONE

Dear Dr. Finnerty,

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.

Both reviewers offer minor suggestions to improve clarity and coherence, such as refining the introduction by including plant descriptions earlier, adjusting figure legends for clarity, and considering alternative explanations for results based on environmental factors. Additionally, one reviewer recommends replacing numerical notation (e.g., (1), (2)) with clearer wording, while the other suggests defining key terms like "neighborhood" earlier and ensuring Aims are referred to by their specific content rather than labels. Overall, the feedback is highly positive, with both reviewers commending the novelty of the study and its contribution to the field.

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Additional Editor Comments:

Reviewers offer minor suggestions to improve clarity and coherence, such as refining the introduction by including plant descriptions earlier, adjusting figure legends for clarity, and considering alternative explanations for results based on environmental factors. Additionally, one reviewer recommends replacing numerical notation (e.g., (1), (2)) with clearer wording, while the other suggests defining key terms like "neighborhood" earlier and ensuring Aims are referred to by their specific content rather than labels. Overall, the feedback is highly positive, with both reviewers commending the novelty of the study and its contribution to the field.

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Reviewer #2: Yes

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Reviewer #2: Yes

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Reviewer #1: Review of PONE-D-25-16194 “Fine-scale associational effects: single plant neighbours can alter susceptibility of focal plants to herbivores”

The authors describe a well-designed study that determined that a single unpalatable plant can reduce visitation and browsing of a palatable plant. The methodology and analysis of the experiment are sound and the results are both important and interesting. I just have a few minor comments that I hope will help with the clarity of the manuscript.

Introduction: Lines 95-100 The herbivore used for the study, the swamp wallaby, is described but not the plants used. A sentence or two about your three plants selected for the study would be helpful here. That information is provided in material and methods so could just be moved into the introduction.

Materials and Methods: Lines 124-127: Naturally occurring B. pinnata shrubs were used, while nursery grown E. punctata and C. gummifera were used. You state the size of the nursery grown plants were of similar size but did not give any description of the size of the B. pinnata plants chosen. Did you choose B. pinnata plants of similar size? If you did please include that information in methods. If similarly sized B. pinnata were not chosen that needs to be addressed as a possible limitation to the study.

Material and methods, results, and figures: For Aim 1 and 2, you use the term Pair or Treatment and then (1),(2) etc to denote your different Pairs or Treatments. The (#) is often distracting and makes the number seem important rather than just denoting the different pairs or treatments. I suggest removing the () around your numbers. It is especially distracting in the figure legends since there are (a), (b) etc to denote which panel is being described.

Figures: Figure 6 legend: lines 294-297 need to describe what panels (a), (b), and (c) denote.

Discussion: Lines 375-387: Reasons for why more of the focal plant E. punctata was foraged in Aim 2 versus Aim 1 are discussed here. Is it also possible that the reason more E. punctate was foraged on in Aim 2 is that the plots seem to have less undergrowth/browse nearby than the plots in Aim 1. I am basing this off the pictures of the experimental setups in Figures 2 and 3.

Reviewer #2: This is an excellent manuscript that sheds new light on the understudied question of how small a plant’s neighborhood can be while still influencing its susceptibility to herbivores. By shifting focus to the smallest spatial scale at which neighborhood effects operate, the authors provide a novel perspective on plant–herbivore interactions. This manuscript was well-written, the experimental design and statistical approaches were robust, and the interpretations of the data appropriate. This manuscript was a delight to review. I have a few general, but minor comments that I think would strengthen the manuscript.

A general suggestion: This manuscript has a quite a few moving parts with multiple plant species and combinations and numbers of said species. Given this, it can be hard to keep track of what “Aim 1” vs. “Aim 2” when they are used in a sentence out of context (e.g. L376). While I think it is fine to name them Aim 1 and Aim 2, I suggest referring to them based on their content (i.e., what they are actually testing).

The opening paragraph is well-written, however, I think a few tweaks to it might strengthen the foundational ideas for the rest of the manuscript. For example:

L43: I think it might be helpful to define a neighborhood (in your context) here, given that it is a term heavily used through the manuscript. For example, it might be useful to say something along the lines of “The assemblage of plants in a patch forms a neighborhood, which can…”

L46: I suggest adding an additional sentence between the ones that start and end on L46 to set up the idea that the neighborhood can either have a positive or negative effect on a given plant. The sentence beginning with 'When herbivores…' could be revised to start with 'For example, when herbivores…,' which would create a smoother transition and more clearly set up the contrast with the following sentence that begins 'In contrast…,' highlighting the opposing effects of a neighborhood.

In the Statistical Analysis section:

L185: Is it possible to include this information elsewhere to omit an orphan paragraph?

In the Discussion:

L368-374: Might it be possible that more plants could emit a strong smell that might be detectable from larger distances? Ultimately, this could influence the distance at which decisions could be made rather than the choice itself.

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Reviewer #1: No

Reviewer #2: No

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PLoS One. 2025 Aug 21;20(8):e0330572. doi: 10.1371/journal.pone.0330572.r002

Author response to Decision Letter 1

9 Jul 2025

Response to reviewers – PLOS One PONE-D-25-16194

“Fine-scale associational effects: single plant neighbours can alter susceptibility of focal plants to herbivores”

We thank the two reviewers for providing comment on our manuscript and suggestions for improvement. We have revised the manuscript in response to the reviewers’ queries and suggestions. We have listed every comment raised by each reviewer below, with a statement of how and where the manuscript has been amended in response to these comments, or our justification for making no change. All line numbers referenced below refer to the clean version of the manuscript uploaded.

Journal Requirements:

When submitting your revision, we need you to address these additional requirements.

1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming.

RESPONSE: The manuscript meets PLOS ONE’s style requirements.

RESPONSE: Additional information regarding the permits you obtained for the work have been provided.

RESPONSE: L116 – 119: Animal ethics approval was granted by the University of Sydney’s Animal Ethics Committee (protocol number 2022/2196) and scientific license (SL 102186) were obtained from New South Wales Office of Environment and Heritage to undertake the fieldwork.

3. Thank you for stating the following financial disclosure: [Authors CM and PB acknowledge funding from the Australian Research Council (grant number DP190101441).].

RESPONSE: The financial disclosure statement has been removed from the manuscript as per comment below. However in the cover letter and the online Funding Statement section we have amended our wording as such:

C.M. and P.B.B. acknowledge funding from the Australian Research Council (grant number DP190101441). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Please include this amended Role of Funder statement in your cover letter; we will change the online submission form on your behalf.

RESPONSE: As above.

4. Thank you for stating the following in the Acknowledgments Section of your manuscript: [C.M. and P.B.B. acknowledge funding from the Australian Research Council (grant number DP190101441).]

RESPONSE: As above.

Please include your amended statements within your cover letter; we will change the online submission form on your behalf.

RESPONSE: As above.

RESPONSE: The datasets generated during and/or analysed during the current study are currently available in the Sydney eScholarship Repository - https://hdl.handle.net/2123/33752.

RESPONSE: Additional information regarding the permits you obtained for the work have been provided.

L116 – 119: Animal ethics approval was granted by the University of Sydney’s Animal Ethics Committee (protocol number 2022/2196) and scientific license (SL 102186) were obtained from New South Wales Office of Environment and Heritage to undertake the fieldwork.

RESPONSE: Supporting information has been removed as was R code and data in the oringally submitted manuscript. The datasets generated during and/or analysed during the current study are now currently available in the Sydney eScholarship Repository and hence no longer required as supplementary material - https://hdl.handle.net/2123/33752.

RESPONSE: Reference list is complete and correct.

Editor’s comments

RESPONSE: We agree with the reviewers’ comments and have gone through and ensured all minor suggested changes have been addressed in the revised manuscript.

Reviewer #1

RESPONSE: We appreciate the reviewer’s comments and suggested corrections. All suggested edits have been included in the revised manuscript.

RESPONSE: As suggested, we have now moved the information provided on the three plant species from the materials and methods section into the introduction.

L101-108: To select a low-quality plant species, we conducted haphazard transects in search for a plant that displayed no signs of browsing damage. From these transects we selected Boronia pinnata, a small, highly odorous native shrub species. This species has been previously shown to be avoided by swamp wallabies within the study site [28]. At the study site, B. pinnata plants generally grow alone, and not in clumps with other B. pinnata. We selected two eucalypt species (Eucalyptus punctata and Corymbia gummifera) as higher-quality plants. These were both a known food source of wallabies at the study site (based on [19] and on unpublished work by [29] and [30]). We confirmed the quality of these plants to wallabies as part of the experiment

RESPONSE: Thank you for pointing this out. We did record naturally occurring B. pinnata size, and yes, they were of similar size to the nursery grown E. punctata and C. gummifera we used. We have now included naturally occurring B. pinnata size in the revised manuscript (L129).

RESPONSE: Thank you for this suggestion. We agree that the notation was distracting and have now removed all “Pair (1) etc.” and “Treatment (1) etc.” notation throughout the manuscript, including in the Materials and Methods, Results, and figure legends, to aid simplicity and readability.

Figures: Figure 6 legend: lines 294-297 need to describe what panels (a), (b), and (c) denote.

RESPONSE: Included

L306-307: Panel a) shows E. punctata and C. gummifera, b) shows E. punctata and B. pinnata, and c) shows C. gummifera and B. pinnata.

RESPONSE: Thanks for pointing this out. Aims 1 and 2 were conducted within the same study site, where undergrowth was relatively consistent across all plots. While the photographs in Figures 2 and 3 suggest that there may have been less undergrowth in the plots shown for Aim 2, this is not representative of broader site conditions. We agree this is a valid potential explanation; however, given that undergrowth was similar across the entire site, we do not expect this to have influenced the amount of E. punctata browsing observed between Aims 1 and 2. Unfortunately, we did not take additional photos that better capture the undergrowth in the Aim 2 plots to clarify this point.

Reviewer #2

This is an excellent manuscript that sheds new light on the understudied question of how small a plant’s neighborhood can be while still influencing its susceptibility to herbivores. By shifting focus to the smallest spatial scale at which neighborhood effects operate, the authors provide a novel perspective on plant–herbivore interactions. This manuscript was well-written, the experimental design and statistical approaches were robust, and the interpretations of the data appropriate. This manuscript was a delight to review. I have a few general, but minor comments that I think would strengthen the manuscript.

RESPONSE: We appreciate the reviewer’s comments and suggested corrections. All suggested edits have been included in the revised manuscript.

RESPONSE: Thank you for this helpful suggestion. We have revised the manuscript to refer to each aim by its content (i.e., the specific experiment being tested) rather than solely as “Aim 1” or “Aim 2” throughout, to improve clarity for readers.

L140-143: Aim 1 (single neighbour experiment) images show a motion-triggered camera above a tub holding (a) an E. punctata seedling (left) next to one C. gummifera seedling (right) and (b) an E. punctata seedling (left) next to one naturally occurring B. pinnata plus pot with soil (right); the C. gummifera and B. pinnata treatment is not shown.

L168 – 172: Aim 2 (neighbourhood experiment) Treatments: (a) a single neighbour of one B. pinnata next to one E. punctata (left), (b) a neighbourhood of five B. pinnata surrounding one E. punctata, (c) an untreated control, one E. punctata on its own and (d) a procedural control, five pots with soil surrounding one E. punctata. Image (c) and (d) show experimental set up of motioned-triggered cameras fastened to wooden stakes. Focal plants are circles in yellow.

L388-397: For the single neighbour experiment (Aim 1, which tested whether a single plant neighbour elicits an associational effect), high-quality focal plants were browsed less by wallabies when next to a single low-quality neighbour. In contrast, in the neighbourhood experiment (Aim 2, which tested whether multiple neighbours elicit stronger associational effects), if browsed, high-quality focal E. punctata were almost always completely consumed regardless of Treatment. This difference in browsing severity may reflect a difference in focal E. punctata quality [8, 40] and/or a difference in B.pinnata quality between the two experiemnts. Although from the same nursery, E. punctata seedlings were purchased at different times within a year and possibly grown under different conditions. Similarly, B. pinnata was naturally occurring in Aim 1 but nursery-grown in Aim 2. Different abiotic growing conditions could affect nutrient and plant secondary metabolite concentrations (e.g. [43]).

The opening paragraph is well-written, however, I think a few tweaks to it might strengthen the foundational ideas for the rest of the manuscript. For example:

RESPONSE: Noted and updated.

L43-45: The assemblage of plants in a patch forms a neighbourhood. This plant neighbourhood can influence the susceptibility of an individual plant to being found and eaten by herbivores, known as an associational effect [1-5].

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Fine-scale associational effects: single plant neighbours can alter susceptibility of focal plants to herbivores

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[pone.0330572.ref001] 1.Tahvanainen JO, Root RB. The influence of vegetational diversity on the population ecology of a specialized herbivore, Phyllotreta cruciferae (Coleoptera: Chrysomelidae). Oecologia. 1972;10(4):321–46. doi: 10.1007/BF00345736 [DOI] [PubMed] [Google Scholar]

[pone.0330572.ref002] 2.Atsatt PR, O’dowd DJ. Plant defense guilds. Science. 1976;193(4247):24–9. doi: 10.1126/science.193.4247.24 [DOI] [PubMed] [Google Scholar]

[pone.0330572.ref003] 3.Milchunas DG, Noy‐Meir I. Grazing refuges, external avoidance of herbivory and plant diversity. Oikos. 2002;99(1):113–30. doi: 10.1034/j.1600-0706.2002.990112.x [DOI] [Google Scholar]

[pone.0330572.ref004] 4.Root RB. Organization of a Plant‐Arthropod Association in Simple and Diverse Habitats: The Fauna of Collards (Brassica Oleracea). Ecological Monographs. 1973;43(1):95–124. doi: 10.2307/1942161 [DOI] [Google Scholar]

[pone.0330572.ref005] 5.Underwood N, Inouye BD, Hambäck PA. A conceptual framework for associational effects: when do neighbors matter and how would we know?. Q Rev Biol. 2014;89(1):1–19. doi: 10.1086/674991 [DOI] [PubMed] [Google Scholar]

[pone.0330572.ref006] 6.Emlen JM. The Role of Time and Energy in Food Preference. The American Naturalist. 1966;100(916):611–7. doi: 10.1086/282455 [DOI] [Google Scholar]

[pone.0330572.ref007] 7.MacArthur RH, Pianka ER. On Optimal Use of a Patchy Environment. The American Naturalist. 1966;100(916):603–9. doi: 10.1086/282454 [DOI] [Google Scholar]

[pone.0330572.ref008] 8.Champagne E, Moore BD, Côté SD, Tremblay J. Intraspecific variation in nutritional traits of neighbouring plants generates a continuum of associational effects. J Vegetation Science. 2020;31(5):920–33. doi: 10.1111/jvs.12914 [DOI] [Google Scholar]

[pone.0330572.ref009] 9.Miller AM, McArthur C, Smethurst PJ. Spatial scale and opportunities for choice influence browsing and associational refuges of focal plants. Journal of Animal Ecology. 2009;78(6):1134–42. [DOI] [PubMed] [Google Scholar]

[pone.0330572.ref010] 10.Bergman M, Iason GR, Hester AJ. Feeding patterns by roe deer and rabbits on pine, willow and birch in relation to spatial arrangement. Oikos. 2005;109(3):513–20. doi: 10.1111/j.0030-1299.2005.13794.x [DOI] [Google Scholar]

[pone.0330572.ref011] 11.Thomas CD. Butterfly larvae reduce host plant survival in vicinity of alternative host species. Oecologia. 1986;70(1):113–7. doi: 10.1007/BF00377118 [DOI] [PubMed] [Google Scholar]

[pone.0330572.ref012] 12.Palmer SCF, Hester AJ, Elston DA, Gordon IJ, Hartley SE. The perils of having tasty neighbors: grazing impacts of large herbivores at vegetation boundaries. Ecology. 2003;84(11):2877–90. doi: 10.1890/02-0245 [DOI] [Google Scholar]

[pone.0330572.ref013] 13.Courant S, Fortin D. Foraging decisions of bison for rapid energy gains can explain the relative risk to neighboring plants in complex swards. Ecology. 2010;91(6):1841–9. doi: 10.1890/09-1226.1 [DOI] [PubMed] [Google Scholar]

[pone.0330572.ref014] 14.Hambäck PA, Inouye BD, Andersson P, Underwood N. Effects of plant neighborhoods on plant-herbivore interactions: resource dilution and associational effects. Ecology. 2014;95(5):1370–83. doi: 10.1890/13-0793.1 [DOI] [PubMed] [Google Scholar]

[pone.0330572.ref015] 15.Wang L, Wang D, Bai Y, Huang Y, Fan M, Liu J, et al. Spatially complex neighboring relationships among grassland plant species as an effective mechanism of defense against herbivory. Oecologia. 2010;164(1):193–200. doi: 10.1007/s00442-010-1676-3 [DOI] [PubMed] [Google Scholar]

[pone.0330572.ref016] 16.Holík J, Janík D, Hort L, Adam D. Neighbourhood effects modify deer herbivory on tree seedlings. Eur J Forest Res. 2021;140(2):403–17. doi: 10.1007/s10342-020-01339-8 [DOI] [Google Scholar]

[pone.0330572.ref017] 17.Senft RL, Coughenour MB, Bailey DW, Rittenhouse LR, Sala OE, Swift DM. Large Herbivore Foraging and Ecological Hierarchies. BioScience. 1987;37(11):789–99. doi: 10.2307/1310545 [DOI] [Google Scholar]

[pone.0330572.ref018] 18.Johnson DH. The Comparison of Usage and Availability Measurements for Evaluating Resource Preference. Ecology. 1980;61(1):65–71. doi: 10.2307/1937156 [DOI] [Google Scholar]

[pone.0330572.ref019] 19.Finnerty PB, Stutz RS, Price CJ, Banks PB, McArthur C. Leaf odour cues enable non-random foraging by mammalian herbivores. J Anim Ecol. 2017;86(6):1317–28. doi: 10.1111/1365-2656.12748 [DOI] [PubMed] [Google Scholar]

[pone.0330572.ref020] 20.Stutz RS, Banks PB, Proschogo N, McArthur C. Follow your nose: leaf odour as an important foraging cue for mammalian herbivores. Oecologia. 2016;182(3):643–51. doi: 10.1007/s00442-016-3678-2 [DOI] [PubMed] [Google Scholar]

[pone.0330572.ref021] 21.Hollis C, Hollis C, Robertshaw J, Robertshaw J, Harden R, Harden R. Ecology of the Swamp Wallaby (Wallabia-Bicolor) in Northeastern New-South-Wales .1. Diet. Wildl Res. 1986;13(3):355. doi: 10.1071/wr9860355 [DOI] [Google Scholar]

[pone.0330572.ref022] 22.Osawa R. Feeding Strategies of the Swamp Wallaby, Wallabia Bicolor, on North Stradbroke Island, Queensland. I: Composition of Diets. Wildl Res. 1990;17(6):615. doi: 10.1071/wr9900615 [DOI] [Google Scholar]

[pone.0330572.ref023] 23.Di Stefano J, Newell GR. Diet Selection by the Swamp Wallaby (Wallabia bicolor): Feeding Strategies under Conditions of Changed Food Availability. J Mammal. 2008;89(6):1540–9. doi: 10.1644/07-mamm-a-193.1 [DOI] [Google Scholar]

[pone.0330572.ref024] 24.Garnick S, Di Stefano J, Elgar MA, Coulson G. Do body size, diet type or residence time explain habitat use in a vertebrate herbivore community?. Aust J Zool. 2016;64(2):91. doi: 10.1071/zo15061 [DOI] [Google Scholar]

[pone.0330572.ref025] 25.Dexter N, Hudson M, James S, MacGregor C, Lindenmayer DB. Unintended Consequences of Invasive Predator Control in an Australian Forest: Overabundant Wallabies and Vegetation Change. PLoS ONE. 2013;8(8):e69087. doi: 10.1371/journal.pone.0069087 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0330572.ref026] 26.Di Stefano J, Butler K, Sebire I, Fagg P. Mammalian browsing impact on regenerating Eucalyptus seedlings in a large commercially managed native forest estate. New Forests. 2008;37(2):197–211. doi: 10.1007/s11056-008-9117-4 [DOI] [Google Scholar]

[pone.0330572.ref027] 27.Morgan JW. Overabundant native herbivore impacts on native plant communities in south‐eastern Australia. Eco Management Restoration. 2021;22(S1):9–15. doi: 10.1111/emr.12437 [DOI] [Google Scholar]

[pone.0330572.ref028] 28.Finnerty PB, Possell M, Banks PB, Orlando CG, Price CJ, Shrader AM, et al. Olfactory misinformation provides refuge to palatable plants from mammalian browsing. Nat Ecol Evol. 2024;8(4):645–50. doi: 10.1038/s41559-024-02330-x [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0330572.ref029] 29.Nettle J. Investigating the Impact of Plant Odour and Atmospheric Pollution on the Foraging of Mammalian Herbivores. The University of Sydney. 2018. [Google Scholar]

[pone.0330572.ref030] 30.Guest L. How do neighbours at different spatial scales affect plant vulnerability to being eaten?. The University of Sydney. 2021. [Google Scholar]

[pone.0330572.ref031] 31.Van Dyck S, Gynther I, Baker A. Field companion to the mammals of Australia. London: New Holland Publishers. 2013. [Google Scholar]

[pone.0330572.ref032] 32.Wickham H, Chang W, Wickham MH. Package ‘ggplot2’. Create elegant data visualisations using the grammar of graphics. 2016;2(1):1–189.

[pone.0330572.ref033] 33.Therneau M. Package ‘coxme’. 2015. [Google Scholar]

[pone.0330572.ref034] 34.Cribari-Neto F, Zeileis A. Beta regression in R. Journal of statistical software. 2010;34:1–24. [Google Scholar]

[pone.0330572.ref035] 35.Lenth R, Lenth MR. Package ‘lsmeans’. The American Statistician. 2018;34(4):216–21. [Google Scholar]

[pone.0330572.ref036] 36.Price C, McArthur C, Norbury G, Banks P. Olfactory misinformation: creating “fake news” to reduce problem foraging by wildlife. Frontiers in Ecol & Environ. 2022;20(9):531–8. doi: 10.1002/fee.2534 [DOI] [Google Scholar]

[pone.0330572.ref037] 37.Price CJ, Bytheway JP, Finnerty PB, Grant LS, Masani S, Orlando CG, et al. Altering reality – sensory tactics to manage wildlife and conserve threatened species. Australian Zoologist. 2024;43(4):510–7. doi: 10.7882/az.2024.010 [DOI] [Google Scholar]

[pone.0330572.ref038] 38.Bedoya-Pérez MA, Isler I, Banks PB, McArthur C. Roles of the volatile terpene, 1,8-cineole, in plant-herbivore interactions: a foraging odor cue as well as a toxin?. Oecologia. 2014;174(3):827–37. doi: 10.1007/s00442-013-2801-x [DOI] [PubMed] [Google Scholar]

[pone.0330572.ref039] 39.Finnerty PB, McArthur C, Banks P, Price C, Shrader AM. The Olfactory Landscape Concept: A Key Source of Past, Present, and Future Information Driving Animal Movement and Decision-making. Bioscience. 2022;72(8):745–52. doi: 10.1093/biosci/biac039 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0330572.ref040] 40.Finnerty PB, Shrader AM, Banks PB, Schmitt MH, McArthur C. Odour information enables patch choice by mammalian herbivores from afar, leading to predictable plant associational effects. Functional Ecology. 2024;38(11):2478–92. doi: 10.1111/1365-2435.14665 [DOI] [Google Scholar]

[pone.0330572.ref041] 41.McArthur C, Finnerty PB, Schmitt MH, Shuttleworth A, Shrader AM. Plant volatiles are a salient cue for foraging mammals: elephants target preferred plants despite background plant odour. Animal Behaviour. 2019;155:199–216. doi: 10.1016/j.anbehav.2019.07.002 [DOI] [Google Scholar]

[pone.0330572.ref042] 42.Moore BD, Lawler IR, Wallis IR, Beale CM, Foley WJ. Palatability mapping: a koala’s eye view of spatial variation in habitat quality. Ecology. 2010;91(11):3165–76. doi: 10.1890/09-1714.1 [DOI] [PubMed] [Google Scholar]

[pone.0330572.ref043] 43.O’Reilly-Wapstra JM, Potts BM, McArthur C, Davies NW. Effects of nutrient variability on the genetic-based resistance of Eucalyptus globulus to a mammalian herbivore and on plant defensive chemistry. Oecologia. 2005;142(4):597–605. doi: 10.1007/s00442-004-1769-y [DOI] [PubMed] [Google Scholar]

[pone.0330572.ref044] 44.Gill RMA. The impact of deer on woodlands: the effects of browsing and seed dispersal on vegetation structure and composition. Forestry. 2001;74(3):209–18. doi: 10.1093/forestry/74.3.209 [DOI] [Google Scholar]

[pone.0330572.ref045] 45.Western D, Maitumo D. Woodland loss and restoration in a savanna park: a 20‐year experiment. African Journal of Ecology. 2004;42(2):111–21. doi: 10.1111/j.1365-2028.2004.00506.x [DOI] [Google Scholar]

[pone.0330572.ref046] 46.Fortin D, Beyer HL, Boyce MS, Smith DW, Duchesne T, Mao JS. Wolves influence elk movements: behavior shapes a trophic cascade in yellowstone national park. Ecology. 2005;86(5):1320–30. doi: 10.1890/04-0953 [DOI] [Google Scholar]

[pone.0330572.ref047] 47.Foster CN, Barton PS, Lindenmayer DB. Effects of large native herbivores on other animals. Journal of Applied Ecology. 2014;51(4):929–38. doi: 10.1111/1365-2664.12268 [DOI] [Google Scholar]

[pone.0330572.ref048] 48.Foster CN, Barton PS, Wood JT, Lindenmayer DB. Interactive effects of fire and large herbivores on web-building spiders. Oecologia. 2015;179(1):237–48. doi: 10.1007/s00442-015-3323-5 [DOI] [PubMed] [Google Scholar]

PERMALINK

Fine-scale associational effects: Single plant neighbours can alter susceptibility of focal plants to herbivores

Patrick B Finnerty

Peter B Banks

Adrian M Shrader

Clare McArthur

Roles

Abstract

Introduction

Materials and methods

Study site

Aim 1: Does a single plant neighbour elicit an associational effect?

Aim 2: Does a neighbourhood of plants elicit stronger associational effects?

Statistical analysis

Aim 1: Does a single plant neighbour elicit an associational effect?.

The model was: Survival (time to 1st browse focal plant) ~ neighbour within Pair + (1|Plot).

Aim 2: Does a neighbourhood of plants elicit stronger associational effects?.

Results

Aim 1: Does a single plant neighbour elicit an associational effect?

Fig 5. Comparison of percentage foliage browsed from focal C. gummifera and E. punctata seedlings (high-quality species) between Pairs at first browsing visit.

Fig 6. Percentage foliage browsed from each species within a Pair by wallabies at first browsing visit.

Aim 2: Does a neighbourhood of plants elicit stronger associational effects?

Fig 8. Boxplots of average percentage visibility of focal E. punctata within each Treatment.

Discussion

Supporting information

Data Availability

Funding Statement

References

Decision Letter 0

Showkat Ganie

Roles

Author response to Decision Letter 1

Decision Letter 1

Showkat Ganie

Roles

Acceptance letter

Showkat Ganie

Roles

Associated Data

Supplementary Materials

Data Availability Statement

ACTIONS

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The model was: Survival (time to 1^st browse focal plant) ~ neighbour within Pair + (1|Plot).