Abstract Abstract
The terrestrial ecosystems of Victoria Land, Antarctica are characteristically simple in terms of biological diversity and ecological functioning. Nematodes are the most commonly encountered and abundant metazoans of Victoria Land soils, yet little is known of their diversity and distribution. Herein we present a summary of the geographic distribution, habitats and ecology of the terrestrial nematodes of Victoria Land from published and unpublished sources. All Victoria Land nematodes are endemic to Antarctica, and many are common and widely distributed at landscape scales. However, at smaller spatial scales, populations can have patchy distributions, with the presence or absence of each species strongly influenced by specific habitat requirements. As the frequency of nematode introductions to Antarctica increases, and soil habitats are altered in response to climate change, our current understanding of the environmental parameters associated with the biogeography of Antarctic nematofauna will be crucial to monitoring and possibly mitigating changes to these unique soil ecosystems.
Keywords: Biodiversity, dispersal, climate change, Eudorylaimus, freeliving nematodes, Geomonhystera, habitat suitability, invasive species, Panagrolaimus, Plectus, Scottnema, soil
Introduction
Understanding the global distribution of biodiversity is critical for studying the evolution, ecology and dynamics of ecosystems and to address how global scale changes in climate, invasive species, and land use will affect ecosystems, ecosystem services, and subsequently, people. Antarctic terrestrial ecosystems might seem less sensitive to global change because this polar desert has low species diversity distributed across a limited area of biologically active ice-free land, comprising less than 0.32% of the continent’s 14 million km2 (Chown and Convey 2007). However, terrestrial ecosystems of Antarctica are not immune to global changes (Adams et al. 2009; Chown et al. 2012b). Small changes in polar climate are amplified through biophysical feedbacks leading to biologically significant alterations in soil habitats and their communities (Doran et al. 2002; Nielsen et al. 2011a). The low species diversity of Antarctic soils makes them uniquely suited for studying the relationships between soil biodiversity and ecosystem functioning, and identifying how global changes may affect species level changes in biodiversity, community composition and distribution (Barrett et al. 2008; Simmons et al. 2009). Measures to conserve, manage and sustain ecosystem functioning in Antarctic and Earth’s other low diversity terrestrial environments will rely on knowledge of species diversity, distributions, and their role in ecosystem processes (Adams et al. 2006; Barrett et al. 2008; Wall 2004).
Aboveground, the diversity and biogeography of terrestrial flora (mosses, lichens and liverworts) has been recently assessed and used to further refine the geographic floral regions of Antarctica (Peat et al. 2007). It is well known that the warmer maritime and subantarctic ecosystems have higher precipitation, organic soils, a more diverse and abundant vegetation (Bölter et al. 2002; Maslen 1979; Nielsen et al. 2011b; Peat et al. 2007) and greater soil faunal diversity (including earthworms and beetles) than continental Antarctica (Block and Christensen 1985; Chown and Van Drimmelen 1992). For example, the northern maritime Antarctic has 100-115 moss and c. 350 lichen species compared to continental Antarctica’s 20–30 moss and c. 90 lichen species (Peat et al. 2007). Throughout Victoria Land vascular plants are absent and fauna are reduced to only a few soil groups and are represented by a patchy spatial distribution of protozoans, nematodes, rotifers, tardigrades, springtails (Collembola), and mites (Acarina) (Adams et al. 2006; Bamforth et al. 2005; Frati et al. 1997; Moorhead et al. 1999; Stevens and Hogg 2002; Virginia and Wall 1999).
Nematoda are a major component of soil food webs in all terrestrial ecosystems including the exposed lands of Antarctica, though their spatial distribution and abundance are highly heterogeneous. In more productive ecosystems, they typically have much higher diversity (Wall Freckman and Virginia 1998) than the Antarctic (Boag and Yeates 1998; Bunt 1954; Maslen 1981). For example, 431 nematode species were recorded from a Cameroon tropical forest ecosystem, with a maximum of 89 species found in 200 individuals enumerated in a soil core (Bloemers et al. 1997). In contrast, the diversity of nematodes in all of Antarctica, including the continental, maritime, and Sub- Antarctic is 54 nematode species, of which only c. 22 species, all endemic, occur on the ice-free terrestrial areas of the continent (Andrássy 1998; Andrássy 2008).
In Antarctica, soil nematodes have been studied primarily in localized and easily accessible areas largely centered around research bases and concentrated on the Antarctic peninsula and islands of the maritime Antarctic and further south in ice-free areas. As a consequence there is relatively little known of their regional biogeography or of the habitats that are suitable for functioning communities. Additionally, there are many remote inland ice-free areas which have yet to be sampled (Convey 1996; Wall 2005), adding to questions on how widespread species are, and whether species rich communities and habitats exist in the more extreme climate zones of the continent.
Regional to continental-scale descriptions of the Antarctic nematofauna have pointed to a paucity of distributional records for much of the continent (Andrássy 1998; Velasco-Castrillón and Stevens 2014). Amongst all regions of Antarctica, Victoria Land is arguably the most intensively studied (Adams et al. 2006). Victoria Land is “ that part of Antarctica which fronts on the western side of the Ross Sea, extending southward from about 70°30'S to 78°00'S, and westward from the Ross Sea to the edge of the polar plateau” (USGS 2003). Here, we synthesize information on the nematode biodiversity, geographic distribution and soil and sediment habitats of the terrestrial nematodes in Victoria Land, Antarctica. Much of this information comes from a series of studies to assess nematode diversity and distribution begun in austral summer 1989–1990 by Wall (formerly Freckman) and Virginia and extending to the present as part of the McMurdo Dry Valley Long Term Ecological Research program funded by the US National Science Foundation (www.mcmlter.org). We report on findings of these studies through 2004 which captures most of the biodiversity information gathered by this research group, whereas more recent research has focused on nematode species response to climate change and soil resource manipulations (Ayres et al. 2010; Doran et al. 2002; Simmons et al. 2009). For purposes of our synthesis, we define two areas, Northern Victoria Land - the area from about 70°30'S to about 76°S, encompassing Terra Nova Bay, Edmonson Point and Cape Hallett (Figure 1); and Southern Victoria Land - the area from about 76°S to about 78°S including all of the McMurdo Dry Valleys and nearby coastal regions (Adams et al. 2006) (Figure 2).
Figure 1.
Victoria Land, Antarctica. Labeled areas represent study locations and major geographic features referenced in the tables and text. Box inset of the McMurdo Dry Valleys is rotated 180 °and expanded in Figure 2.
Figure 2.
McMurdo Dry Valleys, Antarctica. Labeled areas represent study locations and major geographic features referenced in the tables and text.
The McMurdo Dry Valleys (76°5'to 78°5'S, 160°0' to 164°0'E) are located along the TransAntarctic Mountains in Southern Victoria Land and comprise about 4,800 km2 of ice-free land and have different geo/ecological legacies and climatic conditions (Lyons et al. 2000; Moorhead et al. 1999). They are the oldest, driest and coldest deserts on earth (Beyer et al. 1999; Campbell et al. 1998; Fountain et al. 1999). Annual precipitation is less than 10 cm water equivalent, most of which sublimates before it melts (Doran et al. 2002; Fountain et al. 1999). Mean annual air temperature is –20°C (Fountain et al. 1999) and surface soil temperature ranges from -59 °C in winter to 26 °C for short periods during summer (Doran et al. 2002). No vertebrate animals or vascular plants are present and mosses and lichens are rare and mostly confined to ephemeral meltponds, streams and lake moats (Cameron et al. 1970; Horowitz et al. 1972; Kappen 1993). Across the region soils are poorly developed, coarse textured (95 to 99% sand by weight) (Bockheim 1997), low in organic carbon (<1%) (Burkins et al. 2000), saline, and have low biological activity compared to warmer ecosystems (Ball et al. 2009; Barrett et al. 2006a; Parsons et al. 2004). Nematodes are the dominant soil invertebrate, but many soils (~35%) lack extractable soil invertebrates and approximately 50% of McMurdo Dry Valleys soils that contain invertebrates have only one invertebrate species (Freckman and Virginia 1997; Wall Freckman and Virginia 1998).
The distributions of the Dry Valley metazoan species are associated with specific sites and correlate to soil habitat differences in organic matter content, moisture and salinity, and microclimate differences encountered over environmental gradients of coastal to interior sites, latitude, and soil chronosequences and differences in glacial tills (Barrett et al. 2006a).
Coastal areas of Victoria Land are a moister environment than the Dry Valleys and are habitat for birds and marine mammals (e.g. skua gulls, penguins, and seals). Penguin rookeries are associated with ornithogenic soils with significant inputs of carbon and nitrogen transferred from the marine environment to the soil (Bargagli et al. 1997). Ornithogenic soils are the only soils south of the Antarctic Circle containing high concentrations (14–21%) of organic matter (Campbell and Claridge 1966; Heine and Speir 1989). However, even with high C and N availability these soils often have lower nematode diversity than soils of the Dry Valleys, probably owing to very high concentrations of salts and soil compaction and cementing (Porazinska et al. 2002a; Sinclair 2001).
Each of the unique soil ecosystems of Victoria Land imposes considerable physiological constraints on nematode life history traits, requiring adaptive responses to freeze/thaw cycling, osmotic and desiccation stress, and a short growing season (Convey 1996). Nematode responses include cryoprotective dehydration via anhydrobiosis (Adhikari et al. 2009; Adhikari and Adams 2011; Crowe et al. 1992), as well as tolerance to inter and intracellular freezing (Adhikari et al. 2010; Wharton 2003, 2010) and multiyear lifecycles (de Tomasel et al. 2013; Overhoff et al. 1993; Yeates et al. 2009). In addition to stress survival, anhydrobiosis also facilitates long-distance aeolian dispersal (Barrett et al. 2006a), an important mechanism implicated in explanations of their geographic distributions and population genetic structure (Adams et al. 2006; Courtright et al. 2000). All of the nematodes of Victoria Land are inferred to be microbivores with the exception of Eudorylaimus, which is omnivorous (Yeates et al. 1993) (but see Wall 2007).
Nematodes were first collected in Victoria Land by the British ‘Discovery’ expedition of 1901-1903, from Discovery Bay, South Victoria Land and described by Steiner (1916) as Dorylaimus antarcticus (syn. Eudorylaimus antarcticus (Yeates 1970)). The nematodes of Victoria Land then remained largely unstudied for over half a century, until the work of Yeates (1970) and Timm (1971). Between them, these two papers described or redescribed all Victoria Land genera of the time and laid the foundation for future taxonomic work. Yeates (1970) recorded Plectus from southern coastal Victoria Land and synonymized Dorylaimus antarcticus and Antholaimus antarcticus with Eudorylaimus antarcticus. However, subsequent studies have described further Eudorylaimus species from continental Antarctica: Eudorylaimus glacialis (Andrássy 1998), Eudorylaimus nudicaudatus (Heyns 1993) and Eudorylaimus shirasei (Kito et al. 1996), Eudorylaimus quintus (Andrássy 2008) and Eudorylaimus sextus (Andrássy 2008). Due to the taxonomic uncertainty of early accounts (Adams et al. 2006), we will henceforth use Eudorylaimus sp. in reference to all previous reports of distribution. Timm (1971) synonymized Plectus murrayi with Plectus antarcticus (de Man 1904) and studied parts of southern and northern coastal Victoria Land and the McMurdo Dry Valleys. He also re-described three known species: Eudorylaimus antarcticus (Steiner 1916), Monhystera villosa (Bütschli 1873) and Plectus frigophilus (Kirjanova 1958), and described two new species, Scottnema lindsayae and Panagrolaimus davidi. Monhystera villosa was later synonymized with Geomonhystera antarcticola (Andrássy 1998). These early studies focused exclusively on the identification and description of nematode species and not their ecologies.
In the McMurdo Dry Valley Region, most nematological studies have investigated the diversity, ecology and distribution patterns of up to three nematode genera; Eudorylaimus, Plectus, Scottnema (Adams et al. 2006), while the coastal areas of Victoria Land remain less well known (Adams et al. 2006; Bargagli et al. 1997; Barrett et al. 2006a; Porazinska et al. 2002a; Raymond et al. 2013a; Sinclair and Sjursen 2001; this paper; Timm 1971; Vinciguerra 1994). Our effort here is a synthesis of the biogeographic distribution of nematodes in Victoria Land and a consideration of the soil habitats that are associated with nematode distribution, diversity and abundance.
Materials and methods
Based on published and unpublished data, we summarized biogeographic information on the species represented within each nematode genus described in Victoria Land. In addition to published papers, we present information obtained from data on soil, and lake and stream sediment samples collected throughout Victoria Land, by the authors and team members during the austral summers between and including 1990 and 2004. Data referred to as “this study (year)” were derived from nematode soil extraction procedures optimized for Antarctic soils and all nematodes were identified to species (Freckman and Virginia 1993). Frozen soils from these samples are archived at the Wall lab in the Department of Biology at Colorado State University, Fort Collins, CO, USA. Formalin-preserved extracted specimens from these soils are archived in the meiofauna collection of the Monte L. Bean Life Science Museum at Brigham Young University, Provo, UT, USA. Non-occurrences are not reported but can be extrapolated from Tables 1–5. A brief summary of published information on the ecology of each genus is also provided (Table 6).
Table 1.
Biogeographic distribution of Scottnema lindsayae in Victoria Land, Antarctica. NP = not published. NA = specific coordinates not available within the named locale identified above. For references to “this paper”, the year collected refers to the year at the beginning of the austral summer in which samples were collected at 0-10 cm depth unless otherwise indicated. For abundance, ‘Present’ indicates no abundance information available, Low = >0 to 20 nematodes per kg dry soil, M-low = 21 to 200 nematodes per kg dry soil, Medium = 201 to 600 nematodes per kg dry soil, M-high = 601 to 1000 nematodes per kg dry soil, High = 1001 to 2000 nematodes per kg dry soil, V-high = >2000 nematodes per kg dry soil, n = number of samples and % = percentage of samples in which Scottnema lindsayae occurred. AThere may have been a typographical error in the original publication reporting this latitude/longitude. *Geographic coordinates associated with the recognized Antarctic place name for a general feature as listed by the USGS Advisory Committee on Antarctic Names (http://geonames.usgs.gov/antarctic/) and updated by the Polar Geospatial Center (http://www.pgc.umn.edu).
| Biogeographic location | Lat, Long | Habitat | Abundance | Reference | |
|---|---|---|---|---|---|
| Victoria Land | *74°15.00'S, 163°00.00'E | ||||
| - | NP, NP | “river”, wet mosses | Present | (Vinciguerra 1994) | |
| McMurdo Dry Valleys | *77°30.00'S, 162°00.00'E | ||||
| - | NP, NP | soil | Present | (Freckman and Virginia 1990) | |
| - | NP, NP | soil | M-high | (Freckman and Virginia 1993) | |
| - | NP, NP | soil | Present | (Freckman and Virginia 1997) | |
| Alatna Valley | *76°52.82'S, 161°13.82'E | ||||
| East, middle and south west end | NA, NA | soil | Medium (n = 20, 40%) | This paper, collected in 1995 | |
| Battleship Promontory | *76°54.85'S, 160°59.34'E | ||||
| - | NA, NA | soil | Medium (n = 17, 88%) | This paper, collected in 1993 | |
| - | 76°55.30'S, 161°04.79'E | soil | M-high (n = 9, 22%) | This paper, collected in 1994 | |
| - | NA, NA | soil | Medium (n = 6, 83%) | This paper, collected in 1996 | |
| - | 76°52.00'S, 161°05.00'E | soil | Present | (Courtright et al. 2000) | |
| Southwestern Bluff | 76°55.00'S, 161°03.00'E | soil | Medium (n = 14, 57%) | This paper, collected in 2001 | |
| - | 76°55.30'S, 161°04.22'E | soil | Medium (n = 6, 83%) | This paper, collected in 2003 | |
| Barwick Valley | *77°20.71'S, 161°06.09'E | soil | Medium (n = 10, 40%) | This paper, collected in 1994 | |
| Beacon Valley | *77°49.00'S, 160°39.00'E | soil | Low (n = 24, 4%) | This paper, collected in 1990 | |
| Garwood Valley | *78°02.00'S, 164°10.00'E | ||||
| - | NA, NA | soil | High (n = 6, 100%) | This paper, collected in 1993 | |
| - | 78°02.00'S, 164°10.00'E | soil | Medium | (Wall Freckman and Virginia 1998) | |
| - | 78°02.00'S, 164°10.00'E | soil | Present | (Courtright et al. 2000) | |
| - | NA, NA | soil | V-high (n = 13, 100%) | This paper, collected in 2002 | |
| McKelvey Valley | *77°26.00'S, 161°33.00'E | ||||
| Upper | NA, NA | soil | High (n = 18, 50%) | This paper, collected in 1990 | |
| Lower | NA, NA | soil | Low (n = 14, 14%) | This paper, collected in 1990 | |
| Miers Valley | *78°06.00'S, 164°00.00'E | ||||
| Miers Glacier | *78°05.00'S, 163°40.00'E | moraine | Present | (Timm 1971) | |
| - | NA, NA | soil | M-high (n = 24, 88%) | This paper, collected in 1990 | |
| Taylor Valley | *77°38.82'S, 163°03.08'E | ||||
| Canada Glacier | *77°37.00'S, 162°59.00'E | soil | Present | (Timm 1971) | |
| Lacroix Glacier | *77°40.00'S, 162°33.00'E | ||||
| Between Lake Bonney and Lacroix Glacier | NP, NP | small runoff stream | Present | (Timm 1971) | |
| Southeast of Lacroix Glacier | *77°40.00'S, 162°30.00'E | sandy soil | Present | (Timm 1971) | |
| Lake Bonney | *77°43.00'S, 162°25.00'E | ||||
| South side East Lobe | 77°42.92'S, 162°27.65'E | soil | Low (n = 9, 29%) | This paper, collected in 1993 | |
| NA, NA | soil polygons | Medium (n = 99, 64%) | This paper, collected in 1994 | ||
| - | NA, NA | soil | Medium (n = 2, 50%) | This paper, collected in 1995 | |
| - | 77°42.92'S, 162°27.65'E | soil | Low | (Courtright et al. 1996) | |
| - | NP, NP | soil polygons | Medium | (Moorhead et al. 1999) | |
| South side West Lobe | 77°42.5'S, 162°31.2'E | soil | Medium (n = 18, 94%) | This paper, collected in 1999, 2001 and 2002 (Simmons et al. 2009) | |
| - | 77°42.92'S, 162°27.65'E | soil | Present | (Courtright et al. 2000) | |
| - | NA, NA | soil and stream sediment | Medium (n = 20, 45%) | This paper, collected in 2000 | |
| South side West Lobe | NA, NA | soil | M-low (n = 96, 45%) | This paper, collected in 2000, 2002 and 2003 | |
| South side East Lobe | 77°42.55'S, 162°27.39'E | soil | Low | (Courtright et al. 2001) | |
| Lake Chad | *77°38.55'S, 162°45.70'E | soil | Medium (n = 9, 22%) | This paper, collected in 1995 | |
| - | 77°38.10'S, 162°48.15'E | soil | Present | (Boström et al. 2011) | |
| Lake Fryxell | *77°36.58'S, 163°09.10'E | ||||
| - | NA, NA | soil | Medium (n = 26, 23%) | This paper, collected in 1990 | |
| South side | 77°35.94'S, 163°22.68'E | soil | V-high (n = 9, 100%) | This paper, collected in 1993 | |
| - | 77°35.94'S, 163°22.68'E | soil | High (n = 10, 80%) | This paper, collected in 1993 | |
| - | NA, NA | soil | High (n = 102, 87%) | This paper, collected in 1994 | |
| - | NA, NA | soil | Medium (n = 4, 75%) | This paper, collected in 1995 | |
| - | 77°35.94'S, 163°22.68'E | soil | V-high | (Courtright et al. 1996) | |
| Von Guerard (F6) stream | 77°36.49'S, 163°14.95'E | soil | V-high (n = 30, 100%) | This paper, collected in 1996, 1997, 1998, 2001 and 2003 | |
| - | NA, NA | soil | V-high (n = 5, 100%) | This paper, collected in 1997 | |
| Von Guerard Stream/ Harnish Creek network | *77°37.00'S, 163°15.00'E | soil and stream sediments | Medium | (Treonis et al. 1999) | |
| - | NP, NP | soil polygons | High | (Moorhead et al. 1999) | |
| Huey Creek stream | *77°36.00'S, 163°06.00'E | soil | Medium (n = 7, 29%) | This paper, collected in 1999 | |
| Von Guerard stream | *77°37.00'S, 163°15.00'E | soil | High (n = 8, 100%) | This paper, collected in 1999 | |
| South side F6 stream | 77°36.49'S, 163°14.92'E | soil | V-high (n = 12, 100%) | This paper, collected in 1999 and 2001 | |
| - | A77°55.94'S, 163°22.68'E | soil | Present | (Courtright et al. 2000) | |
| Harnish Creek transect | *77°37.00'S, 163°13.00'E | soil and stream sediment | M-high (n = 20, 90%) | This paper, collected in 2000 | |
| South side by F6 (SF) | NA, NA | soil | V-high (n = 96, 100%) | This paper, collected in 2000, 2002 and 2003 | |
| South-east shore | 77°35.56'S, 163°22.41'E | soil | V-high | (Courtright et al. 2001) | |
| - | 77°36.00'S, 162°15.00'E | soil | V-high | (Treonis et al. 2002) | |
| South side near F6 | 77°36.40'S, 163°15.30'E | soil and lake sediment | High (n = 12, 67%) | This paper, collected in 2002 | |
| South side near Green Creek | 77°37.36'S, 163°03.91'E | soil | M-high (n = 20, 85%) | This paper, collected in 2003 | |
| South side near F6 | 77°36.72'S, 163°15.18'E | soil | High (n = 20, 90%) | This paper, collected in 2003 | |
| Von Guerard stream | 77°37.00'S, 163°15.00'E | soil | High | (Barrett et al. 2006c) | |
| Green Creek | 77°37.36'S, 163°03.91'E | soil | M-High | (Barrett et al. 2006c) | |
| Lake Hoare | *77°38.00'S, 162°51.00'E | ||||
| North side | 77°37.49'S, 162°54.31'E | soil | M-low (n = 18, 100%) | This paper, collected in 1993 | |
| South side | 77°38.03'S, 162°52.75'E | soil | High (n = 9, 100%) | This paper, collected in 1993 | |
| South side | 77°37.59'S, 162°52.57'E | soil | High (n = 56, 100%) | This paper, collected in 1993, 1994, 1995, 1996, 1997 and 2001 | |
| North side | 77°38.00'S, 162°53.00'E | soil (0-2.5, 2.5-5, 5-10, 10-20 cm | High | (Powers et al. 1994a; 1995a) | |
| South shore | NP, NP | soil at varying elevation | Medium | (Powers et al. 1998) | |
| - | NA, NA | soil polygons | High (n = 104, 96%) | This paper, collected in 1994 | |
| South side | 77°38.02'S, 162°52.23'E | soil | High (n = 40, 83%) | This paper, collected in 1994, 1995, 1996, 1997 and 2001 | |
| North side | 77°38.00'S, 162°53.00'E | soil | Medium | (Powers et al. 1995a) | |
| South side | 77°38.00'S, 162°53.00'E | soil at varying elevation | M-high | (Powers et al. 1995a) | |
| South side | 77°38.00'S, 162°53.00'E | soil (0-2.5, 2.5-5, 5-10, 10-20 cm) | Medium | (Powers et al. 1995b) | |
| South side | NA, NA | soil polygons | M-high (n = 24, 100%) | This paper, collected in 1995 | |
| North side | 77°37.49'S, 162°54.31'E | soil | M-low | (Courtright et al. 1996) | |
| South side | 77°38.03'S, 162°52.75'E | soil | M-high | (Courtright et al. 1996) | |
| - | NP, NP | soil | Medium | (Freckman and Virginia 1997) | |
| South side | NA, NA | soil | M-high (n = 12, 100%) | This paper, collected in 1997 | |
| South side | 77°38.00'S, 162°53.00'E | soil | Medium | (Powers et al. 1998) | |
| - | NP, NP | soil polygons | High | (Moorhead et al. 1999) | |
| North side | NA, NA | soil | V-high (n = 8, 100%) | This paper, collected in 1999 | |
| South side | NA, NA | soil | M-high (n = 8, 100%) | This paper, collected in 1999 | |
| South side | 77°38.07'S, 162°52.59'E | soil | M-high (n = 18, 100%) | This paper, collected in 1999, 2001 and 2002 | |
| North side | 77°37.49'S, 162°54.31'E | soil | Present | (Courtright et al. 2000) | |
| South side | 77°38.03'S, 162°52.75'E | soil | Present | (Courtright et al. 2000) | |
| South side | 77°38.00'S, 162°53.00'E | soil | M-high | (Treonis et al. 2000) | |
| North side | 77°37.29'S, 162°54.19'E | soil | M-low | (Courtright et al. 2001) | |
| South side | 77°38.02'S, 162°52.45'E | soil | M-high | (Courtright et al. 2001) | |
| South side | 77°38.00'S, 162°53.00'E | soil | M-high | (Porazinska et al. 2002b) | |
| - | 77°38.00'S, 162°53.00'E | soil | Medium | (Treonis et al. 2002) | |
| - | 77°37.90'S, 162°53.20'E | soil and lake sediments | M-high (n = 11, 73%) | This paper, collected in 2002 | |
| - | NP, NP | soil | Present | (Overhoff et al. 1993) | |
| North side | NP, NP | lake bottom detritus | Present | (Vinciguerra 1994) | |
| - | 77°37.00'S, 160°50.00'E | soil | Medium | (Wall Freckman and Virginia 1998) | |
| South side | NA, NA | wetlands (upland ponds) | M-low (n = 48, 19%) | This paper, collected in 2000 | |
| - | NP, NP | soil | High | (Treonis et al. 2000) | |
| - | NP, NP | 0-5 cm soil (exposed and subnivian) | High | (Gooseff et al. 2003) | |
| South side | NP, NP | bare soil >80 m from wetlands (upland ponds) | Medium | (Moorhead et al. 2003) | |
| Mummy Pond | 77°40.06'S, 162°39.00'E | soil | Low (n = 5, 20%) | This paper, collected in 1997 | |
| Nussbaum Riegel | 77°38.52'S, 162°46.89'E | soil | V-High (n = 5, 20%) | This paper, collected in 1997 | |
| Victoria Valley | *77°23.00'S, 162°00.00'E | ||||
| Lower Victoria Valley | 77°21.81'S, 162°19.11'E | soil | High (n = 10, 60%) | This paper, collected in 1993 | |
| NP | 77°21.81'S, 162°19.11'E | soil | High (n = 9, 100%) | This paper, collected in 1993 | |
| Lake Vida | *77°23.29'S, 161°56.05'E | ||||
| - | NA, NA | soil | Medium (n = 16, 19%) | This paper, collected in 1990 | |
| - | 77°23.35'S, 162°02.60'E | soil | Medium (n = 10, 50%) | This paper, collected in 1993 | |
| - | NA, NA | soil | Medium (n = 11, 27%) | This paper, collected in 1994 | |
| - | 77°22.58'S, 161°13.56'E | soil | NA (n = 2, 100%) | This paper, collected in 2000 | |
| Vida Met Station | NA, NA | soil | Low (n = 4, 50%) | This paper, collected in 2002 | |
| - | NA, NA | soil | M-high (n = 10, 80%) | This paper, collected in 1997 | |
| - | 77°23.00'S, 162°00.00'E | soil | M-high | (Wall Freckman and Virginia 1998) | |
| - | NA, NA | soil | NA (n = 6, 83%) | This paper, collected in 2003 | |
| Victoria Lower Glacier | *77°18.00'S, 162°40.00'E | ||||
| - | 77°21.81'S, 162°19.11'E | soil | High | (Courtright et al. 1996) | |
| - | 77°22.57'S, 162°13.56'E | soil | NA (n = 6, 83%) | This paper, collected in 2000 | |
| - | 77°21.81'S, 162°19.11'E | soil | Present | (Courtright et al. 2000) | |
| South-west | 77°21.49'S, 162°19.07'E | soil | High | (Courtright et al. 2001) | |
| Victoria Upper Glacier | *77°16.00'S, 161°25.00'E | ||||
| - | 77°17.35'S, 161°33.03'E | soil | High (n = 10, 60%) | This paper, collected in 1993 | |
| - | 77°17.35'S, 161°33.03'E | soil | Low (n = 9, 11%) | This paper, collected in 1993 | |
| Victoria Upper Lake | *77°19.00'S, 161°35.00'E | soil | M-high (n = 20, 35%) | This paper, collected in 1990 | |
| Wright Valley | *77°31.39'S, 161°58.70'E | ||||
| Dais | *77°33.00'S, 161°16.00'E | ||||
| - | NP, NP | soil | Present | (Courtright et al. 2000) | |
| - | NA, NA | soil | NA (n = 3, 100%) | This paper, collected in 2000 | |
| East of Meserve Glacier | *77°31.00'S, 162°17.00'E | algal mat | NP | (Timm 1971) | |
| Labyrinth | *77°33.00'S, 160°50.00'E | ||||
| West | 77°33.04'S, 160°43.15'E | soil | M-low (n = 9, 100%) | This paper, collected in 1993 | |
| - | 77°33.04'S, 160°43.15'E | soil | M-low (n = 9, 78%) | This paper, collected in 1993 | |
| - | 77°33.04'S, 160°43.15'E | soil | Low | (Courtright et al. 1996) | |
| - | 77°31.00'S, 161°50.00'E | soil | M-low | (Wall Freckman and Virginia 1998) | |
| West | 77°33.02'S, 160°43.09'E | soil | Low | (Courtright et al. 2001) | |
| - | NA, NA | soil | Low (n = 12, 17%) | This paper, collected in 2003 | |
| Lake Brownworth | *77°26.00'S, 162°45.00'E | ||||
| - | NP, NP | soil | Present | (Overhoff et al. 1993) | |
| - | 77°26.13'S, 162°42.61'E | soil | M-low (n = 9, 33%) | This paper, collected in 1993 | |
| - | 77°26.13'S, 162°42.61'E | soil | M-low | (Courtright et al. 1996) | |
| - | 77°26.13'S, 162°42.61'E | soil | Present | (Courtright et al. 2000) | |
| South-west shore | 77°26.08'S, 162°42.37'E | soil | M-low | (Courtright et al. 2001) | |
| Met Station | NA, NA | soil | Medium (n = 4, 75%) | This paper, collected in 2002 | |
| Bull Pass | *77°28.00'S, 161°46.00'E | soil | Medium (n = 22, 23%) | This paper, collected in 1990 | |
| Lake Bull | *77°31.51'S, 161°42.68'E | soil | Low (n = 12, 17%) | This paper, collected in 1990 | |
| - | 77°28.00'S, 161°46.00'E | soil | High (n = 24, 33%) | (Poage et al. 2008) | |
| Lake Vanda | *77°32.00'S, 161°33.00'E | ||||
| Near Lake Vanda | 77°32.00'S, 161°33.00'E | soil | Present | (Timm 1971) | |
| Vanda Station | 77°31.00'S, 161°40.00'E | soil | M-low (n = 2, 100%) | This paper, collected in 2002 | |
| Unspecified Locations | |||||
| - | NA, NA | soil | M-low (n = 5, 80%) | This paper, collected in 1997 | |
| - | NA, NA | soil | Present (n = 1, 100%) | This paper, collected in 2000 | |
| - | NA, NA | soil | Present (n = 10, 60%) | This paper, collected in 2003 | |
| Koettlitz Glacier and Southern Coastal Regions | *78°15.00'S, 164°15.00'E | ||||
| Péwé Lake | *77°56.67'S, 164°16.87'E | stony soil near the lake | Present | (Timm 1971) | |
| Strand Moraines | *77°45.04'S, 164°29.90'E | sandy soil | Present | (Timm 1971) | |
| Marble Point | *77°26.00'S, 163°50.00'E | mossy soil (Bryum antarcticum) | Present | (Timm 1971) | |
| Northern Coastal Region | |||||
| Cape Hallett | 72°19.29'S, 170°13.52'E | soil | Low (n = 67, 56%) | (Raymond et al. 2013a) | |
| Crater Cirque | *72°37.49'S, 169°22.48'E | lake bottom detritus and wet mosses | Present | (Vinciguerra 1994) | |
| Edmonson Point | *74°20.00'S, 165°08.00'E | ||||
| - | NA, NA | soil | Medium (n = 10, 80%) | This paper, collected in 1996 | |
| - | NA, NA | soil | Present (n = 28, 36%) | This paper, collected in 1996 | |
| - | NP, NP | soil | Present | (Bargagli et al. 1997) | |
| - | NA, NA | soil | Medium (n = 8, 63%) | This paper, collected in 2001 | |
| Gondwana Station | 74°37.57'S, 164°11.91'E | soil | M-Low (n = 371, 79%) | (Raymond et al. 2013a) | |
| Luther Peak | *72°21.88'S, 169°50.91'E | ||||
| Luther Cirque | 72°22.20'S, 169°53.10'E | soil | Medium (n = 40, 85%) | This paper, collected in 2003 | |
| Luther Vale North | 72°22.00'S, 169°53.00'E | soil | Medium | (Barrett et al. 2006c) | |
| Luther Vale South | 72°22.00'S, 169°53.00'E | soil | Medium | (Barrett et al. 2006c) | |
| Terra Nova Bay | *74°54.51'S, 164°27.19'E | ||||
| 600 km north and south of the Italian station | NP, NP | mosses, lichens, fresh water sediments and penguin excrements (there are no details of whether Scottnema lindsayae occurred in all habitats or only in some) | Present | (Vinciguerra et al. 1994) | |
| - | 74°20.00'S, 165°08.00'E | soil | Present | (Courtright et al. 2000) | |
Table 5.
Biogeographic distribution of Geomonhystera antarcticola in Victoria Land, Antarctica. NP = not published. NA = not available. For references to “this paper”, the year collected refers to the year at the beginning of the austral summer in which samples were collected. For abundance, Low = >0 to 20 nematodes per kg dry soil, M-low = 21 to 200 nematodes per kg dry soil, n = number of samples and % = percentage of samples in which Geomonhystera occurred.
| Biogeographic location | Lat, Long | Habitat | Abundance | Reference | |
|---|---|---|---|---|---|
| McMurdo Dry Valleys | *77°30.00'S, 162°00.00'E | ||||
| Alatna Valley | *76°52.82'S, 161°13.82'E | ||||
| Battleship Promontory | *76°54.85'S, 160°59.34'E | ||||
| - | NA, NA | soil | Low (n = 17, 47%) | This paper, collected in 1993 | |
| Southwestern Bluff | 76°55.00'S, 161°03'.00E | soil | Low (n = 14, 14%) | This paper, collected in 2001 | |
| - | NA, NA | soil | Low (n = 6, 50%) | This paper, collected in 2003 | |
| Taylor Valley | *77°38.82'S, 163°03.08'E | ||||
| Lake Bonney | *77°43.00'S, 162°25.00'E | soil | M-low (n = 2, 50%) | This paper, collected in 1998 | |
| Wright Valley | *77°31.39'S, 161°58.70'E | ||||
| 183 m east of Meserve Glacier | *77°31.00'S, 162°17.00'E | algal mat on soil | Present | (Timm 1971) | |
| Between Lake Vanda and Lake Bull | NP, NP | dry algae from the edge of a small pond | Present | (Wharton and Brown 1989) | |
| - | soil | Low (n = 10, 20%) | This paper, collected in 2003 | ||
| Northern Coastal Region | |||||
| Edmonson Point | *74°20.00'S, 165°08.00'E | soil | Present | (Bargagli et al. 1997) | |
Table 6.
Ecology of Nematode Genera in Victoria Land.
| Genus | Co-occurs with | Nematode community complexity | Feeding | Reproduction |
|---|---|---|---|---|
| Scottnema |
Eudorylaimus, Plectus, Geomonhystera, Panagrolaimus (rare, only in Dry Valleys; Bargagli et al. 1997; Courtright et al. 2001; this paper), |
1 species- most common 2 species- often (usually Eudorylaimus antarcticus), 3 or 4 species- rare 5 species- not recorded (Courtright et al. 2001; Freckman and Virginia 1997; this paper) |
bacteria, yeast (Overhoff et al. 1993) |
amphimictic (Overhoff et al. 1993) |
| Plectus | Scottnema, Eudorylaimus, Geomonhystera, Panagrolaimus | 1 species- rare 2 species- most common (usually with Eudorylaimus), 3- often 4 species- rare 5 species- not recorded |
bacteria (Wharton and Brown 1989) | usually unisexual (parthenogenic), males do exist but are very rare (Andrássy 2008; Kito et al. 1991; Vinciguerra 1994) |
| Eudorylaimus |
Scottnema, Plectus, Geomonhystera, Panagrolaimus |
1 species- not recorded 2 species- most common (usually with Scottnema or Plectus), 3- often 4 species- rare 5 species- not recorded |
Eudorylaimus are thought to feed on fungi, unicellular algae and soil invertebrates (Raymond et al. 2013a; Yeates et al. 1993); presence of chloroplasts in esophagus (Wall 2007) | amphimictic (Eudorylaimus antarcticus) (Yeates 1970) |
| Panagrolaimus | Scottnema (rare, only in Dry Valleys), Eudorylaimus, Plectus | 1 species- common (most common outside of Victoria Land) 2 species- rare 3- common (with Eudorylaimus and Plectus), 4 species- rare, only in Dry Valleys 5 species- not recorded (Porazinska et al. 2002a; this paper) |
bacteria (Wharton 1994; Wharton and Barclay 1993) |
amphimictic (Timm 1971) |
| Geomonhystera | Scottnema, Eudorylaimus, Plectus | 1 species- not recorded 2 species- often (with Eudorylaimus antarcticus) 3- most common (with Scottnema lindsayae and Eudorylaimus antarcticus) 4 species- often 5 species- not recorded (this paper) |
algae, fungi, actinobacteria (Newsham et al. 2004) | amphimictic (Andrássy 1981; Timm 1971) |
Results and discussion
Only five genera of terrestrial nematodes are recorded from Victoria Land Antarctica: Scottnema, Plectus, Eudorylaimus, Panagrolaimus, and Geomonhystera. For some genera species delimitation remains unresolved (Andrássy 1998; Velasco-Castrillón and Stevens 2014).
Scottnema (Rhabditida: Cephalobidae)
Scottnema is an exclusively Antarctic genus comprised of only one species, Scottnema lindsayae (Timm 1971). Scottnema lindsayae (synonymous with Scottnema lindsayi) is thought to have evolved from a common ancestor of the genus Acrobeles (Shishida and Ohyama 1986), with a recent phylogenetic analysis placing the genus Stegelletina as its closest relative (Boström et al. 2011). Scottnema lindsayae is the most southerly known occurring nematode in the world, found as far south as Mt Harcourt (83°08.99'S, 163°21.81'E) near the base of the Beardmore Glacier (Adams et al. 2007).
Biogeographic distribution. Scottnema lindsayae is the dominant nematode of Victoria Land (Table 1) based on abundance and widespread distribution in numerous samples from the McMurdo Dry Valleys (Courtright et al. 2001; Freckman and Virginia 1990; 1993, 1997; Moorhead et al. 1999; Porazinska et al. 2002b; Powers et al. 1995b; Powers et al. 1998; Treonis et al. 1999, 2000). Scottnema lindsayae was first described in Victoria Land in samples from Wright Valley and the southern coastal region (Marble Point, Strand Moraines) (Timm 1971) and has since been recorded in the northern coastal region occurring as far north as Luther Cirque (72°22.20'S, 169°53.10'E) (Table 1).
Scottnema lindsayae also occurs on two islands off the coast of Victoria Land: Ross Island (Porazinska et al. 2002a; Sinclair 2001; Timm 1971) and Kay Island (Vinciguerra 1994). On the opposite side of Antarctica, Shishida and Ohyama (1986) report Scottnema lindsayae from Rundvågshetta, East Ongul Island (69°01'S, 39°58'E), and Mouratov et al. (2001) report Scottnema lindsayae near Machu Picchu station (62°05.51'S, 58°28.21'W) on the coast of Admiralty Bay, although Andrássy (1998) questions this report.
Habitat. Scottnema lindsayae survives in a wide range of terrestrial habitats (Table 1). In Victoria Land Scottnema lindsayae occurs most commonly in dry, bare and sandy or rocky soils and has been found at 30–40 cm soil depth near south shore of Lake Hoare (Powers et al. 1995b). Less frequently, Scottnema lindsayae occurs in the moister habitats such as: snow covered soil (subnivian); near streams and in lake sediments (this paper; Treonis et al. 1999; Vinciguerra 1994); and, under mosses (e.g. Bryum antarcticum) (Timm 1971; Vinciguerra 1994). Scottnema lindsayae has also been found associated with an algal mat (Timm 1971) but whether the algal mat was from soil, a lake or a stream is unknown.
In comparison with other nematodes of Victoria Land, Scottnema lindsayae occurs most frequently and at greater abundances in soil habitats with lower moisture, higher pH, higher EC, and higher inorganic C (Courtright et al. 2001; Freckman and Virginia 1997; Moorhead et al. 1999; Porazinska et al. 2002b; Powers et al. 1998; Treonis et al. 1999). In these habitat types, Scottnema lindsayae may comprise >99% of invertebrates present (Treonis et al. 1999, 2002), and may be the only invertebrate present. Treonis et al. (2000) found that Scottnema lindsayae becomes anhydrobiotic in coarse textured Dry Valley soils at a gravimetric soil moisture threshold of ~2%. In a study of 32 samples from one site on King George Island (62°05.51'S, 58°28.21'W), Mouratov et al. (2001) suggested soil moisture content may be one of the main factors determining the distribution of Scottnema lindsayae and found that the species has a preference for soil moisture of 2–5%. Many studies in the McMurdo Dry Valleys (Barrett et al. 2006c; Courtright et al. 2001; Porazinska et al. 2002b; Powers et al. 1998) have identified a relationship between greater abundance of Scottnema lindsayae and low soil moisture. Scottnema lindsayae tolerates a wide range of soil moistures, but is typically absent from flowing meltstreams and saturated soils. Interactions between soil moisture and salinity are complex and create changing osmotic conditions in soils. In a comparative study of dry soil and moist soil under snowpacks no correlation was found between Scottnema lindsayae and soil moisture (Gooseff et al. 2003), which could be attributed to changing osmotic potential and salinity. Soil salinity factors (EC and pH) have a significant influence on the distribution of Scottnema lindsayae in the Dry Valleys (Freckman and Virginia 1997; Poage et al. 2008; Porazinska et al. 2002b). For example, Scottnema lindsayae are found predominantly in soils with an EC<700 mS cm-1 (Courtright et al. 2001; Nkem et al. 2006a; Poage et al. 2008), and appear unable to tolerate salinity over 4100 mS cm-1 (Nkem et al. 2006a).
Scottnema lindsayae is recorded at a range of elevations, from the McMurdo Dry Valley floors to about 600 and 1300 m above sea level (at Mt. Suess and Battleship Promentory, respectively) in Victoria Land (Moorhead et al. 2003; Porazinska et al. 2002b; Powers et al. 1998; this paper) and 800 m above sea level outside of Victoria Land (Adams et al. 2006). On Ross Island, Scottnema lindsayae occurs in soils located away from penguin rookeries and in soils with ornithogenic inputs (Sinclair and Sjursen 2001), but is absent within rookeries (Porazinska et al. 2002a; Sinclair 2001; Yeates et al. 2009). Similar observations are not recorded for Victoria Land. Other studies recording the presence of Scottnema lindsayae outside of Victoria Land have found the nematode amongst mosses (e.g. Saniona uncinata) and at King George Island, associated with a perennial plant (Deschampsia antarctica) (Mouratov et al. 2001; Shishida and Ohyama 1986; Vinciguerra 1994; Wharton and Brown 1989).
Plectus (Plectida: Plectidae)
Several Plectus species have been described from Antarctica: Plectus antarcticus (de Man 1904), Plectus parietinus (Bastian 1865), Plectus parvus (Bastian 1865), Plectus cirratus (Bastian 1865), Plectus belgicae (de Man 1904), Plectus murrayi (Yeates 1970), Plectus acuminatus (Bastian 1865) and Plectus frigophilus (Kirjanova, 1958). Many species are morphologically similar and several taxonomic statements remain unresolved (Andrássy 1998; Boström 2005; Velasco-Castrillón and Stevens 2014).
Biogeographic distribution. Four Plectus species have been recorded from Victoria Land: Plectus antarcticus, Plectus frigophilus, Plectus murrayi and Plectus acuminatus. Specimens of Plectus antarcticus previously described from Victoria Land have been reinterpreted as synonymous with Plectus murrayi (and Plectus belgicae and Plectus parvus) (Kito et al. 1991; Timm 1971; Yeates 1979) such that there are only three currently recognized Plectus species in Victoria Land. Most studies have described Plectus spp. (murrayi and frigophilus) from the McMurdo Dry Valleys (Gooseff et al. 2003; Porazinska et al. 2002b; Timm 1971; Wall Freckman and Virginia 1998) with only two studies reporting the occurrence of Plectus spp. in other areas of Victoria Land. Bargagli et al. (1997) reported Plectus spp. from Edmonson Point and Vinciguerra et al. (1994) found Plectus antarcticus, Plectus frigophilus and Plectus acuminatus at Terra Nova Bay.
In the McMurdo Dry Valleys, only Plectus murrayi and Plectus frigophilus occur, with Plectus murrayi the most abundant and widespread (Table 2). Plectus murrayi and Plectus frigophilus (Kito et al. 1991; Shishida and Ohyama 1986) are endemic to the Antarctic, but not solely to Victoria Land. Close to Victoria Land, Plectus murrayi and Plectus frigophilus have been recorded frequently from Ross Island (e.g. Cape Royds, Cape Evans, Cape Crozier, McMurdo Station and Rocky Point) (Dougherty et al. 1960; Murray 1910; Porazinska et al. 2002a; Sinclair 2001; Wharton and Brown 1989) and Plectus frigophilus has been recorded on Dunlop Island (Timm 1971; USGS 2003). Plectus antarcticus occurs primarily in the maritime, and thus most of the recordings of Plectus antarcticus on the continent are assumed to be Plectus murrayi (Andrássy 1998).
Table 2.
Biogeographic distribution of Plectus species in Victoria Land, Antarctica. NP = not published, NA = not available, mur = Plectus murrayi. frig = Plectus frigophilus, where both exist = spp. For abundance, A abundance is per kg moss and adhering rock fragments not soil, Low = >0 to 20 nematodes per kg dry soil, M-low = 21 to 200 nematodes per kg dry soil, Medium = 201 to 600 nematodes per kg dry soil, M-high = 601 to 1000 nematodes per kg dry soil, High = 1001 to 2000 nematodes per kg dry soil, V-high = >2000 nematodes per kg dry soil, n = number of samples and % = percentage of samples in which Plectus occurred. For references to “this paper”, the year collected refers to the year at the beginning of the austral summer in which samples were collected to 0-10 cm depth. BThis publication refers to a map for more details on sample location.
| Biogeographic location | Lat, Long | Habitat | Species | Abundance | Reference | |
|---|---|---|---|---|---|---|
| McMurdo Dry Valleys | *77°30.00'S, 162°00.00'E | |||||
| - | NP, NP | soil | spp. | Present | (Freckman and Virginia 1990) | |
| - | NP, NP | soil | spp. | Low | (Freckman and Virginia 1993) | |
| - | NP, NP | soil | mur | Present | (Freckman and Virginia 1997) | |
| - | NP, NP | streams | spp. | Present | (Moorhead et al. 1999) | |
| Alatna Valley | *76°52.82'S, 161°13.82'E | |||||
| Battleship Promontory | *76°54.85'S, 160°59.34'E | soil | mur | Low (n = 17, 6%) | This paper, collected in 1993 | |
| East, middle and southwestern end | NA, NA | soil | mur | Low (n = 20, 10%) | This paper, collected in 1995 | |
| Garwood Valley | *78°02.00'S, 164°10.00'E | |||||
| Garwood Lake | *78°02.00'S, 164°15.00'E | NP | frig | Present | (Timm 1971) | |
| - | NA, NA | soil | mur | M-low (n = 6, 50%) | This paper, collected in 1993 | |
| - | 78°02.00'S, 164°10.00'E | soil | mur | M-low | (Wall Freckman and Virginia 1998) | |
| - | NA, NA | soil | mur | Low (n = 13, 8%) | This paper, collected in 2002 | |
| Miers Valley | *78°06.00'S, 164°00.00'E | |||||
| Miers Glacier | *78°05.00'S, 163°40.00'E | mossy soil from glacier foot, runoff stream | frig | Present | (Timm 1971) | |
| - | NA, NA | soil | mur | M-low (n = 24, 29%) | This paper, collected in 1990 | |
| Taylor Valley | *77°38.82'S, 163°03.08'E | |||||
| Canada Glacier | *77°37.00'S, 162°59.00'E | |||||
| Near the glacier | NP, NP | soil | frig | Present | (Timm 1971) | |
| - | 77°37.31'S, 162°58.26'E | windblown sediment on top of glacier | mur | Present (n = 2, 100%) | This paper, collected in 1997 | |
| Waterfall (upper west) | NA, NA | cryconite hole | mur | Present | This paper, collected in 2001 | |
| Lake Bonney | *77°43.00'S, 162°25.00'E | |||||
| - | NP, NP | lake, soil nearby | frig | Present | (Timm 1971) | |
| - | NA, NA | soil polygon cracks | mur | Low (n = 99, 5%) | This paper, collected in 1994 | |
| - | NA, NA | soil | mur | Medium (n = 2, 100%) | This paper, collected in 1995 | |
| - | NA, NA | algal mat | spp. | Present (n = 5, 100%) | This paper, collected in 1995 | |
| West Lobe | 77°43.50'S, 162°18.95'E | soil | mur | Low (n = 18, 33%) | This paper, collected in 1999, 2001 and 2002 | |
| - | NA, NA | soil and stream sediment | mur | M-low (n = 20, 30%) | This paper, collected in 2000 | |
| West Lobe | NA, NA | soil | mur | Low (n = 72, 7%) | This paper, collected in 2000 and 2003 | |
| - | 77°43.40'S, 162°18.40'E | soil and sediment | mur | Low (n = 12, 25%) | This paper, collected in 2002 | |
| Lake Chad | *77°38.55'S, 162°45.70'E | |||||
| - | NP, NP | NP | frig | Present | (Timm 1971) | |
| - | NA, NA | algal mat | spp. | NA (n = 1, 100%) | This paper, collected in 1995 | |
| - | NA, NA | soil | mur | M-low (n = 9, 56%) | This paper, collected in 1995 | |
| Lake Fryxell | *77°36.58'S, 163°09.10'E | |||||
| - | NP, NP | NP | frig | Present | (Timm 1971) | |
| - | NP, NP | algae in a drift stream near the lake | spp. | Present | (Wharton and Brown 1989) | |
| - | NA, NA | algal mat | ant | M-low (n = 10, 100%) | This paper, collected in 1990 | |
| - | NA, NA | soil | mur | M-high (n = 26, 77%) | This paper, collected in 1990 | |
| - | 77°35.94'S, 163°22.68'E | soil | mur | Low (n = 10, 10%) | This paper, collected in 1993 | |
| - | NA, NA | algal mat | spp. | NA (n = 1, 100%) | This paper, collected in 1995 | |
| - | NA, NA | soil | mur | Medium (n = 4, 75%) | This paper, collected in 1995 | |
| Von Guerard stream / Harnish Creek network | *77°37.00'S, 163°15.00'E | stream sediments and surrounding soils | spp. | M-low | (Treonis et al. 1999) | |
| Huey Creek | *77°36.00'S, 163°06.00'E | soil | mur | M-low (n = 7, 57%) | This paper, collected in 1999 | |
| Harnish Creek | *77°37.00'S, 163°13.00'E | soil and sediment | mur | M-low (n = 20, 60%) | This paper, collected in 2000 | |
| South side | NA, NA | soil | mur | Low (n = 72, 4%) | This paper, collected in 2000 and 2002 | |
| South side | 77°36.40'S, 163°15.30'E | soil and sediment | mur | V-High (n = 12, 75%) | This paper, collected in 2002 | |
| South side | 77°36.49'S, 163°14.95'E | soil | mur | Low (n = 6, 17%) | This paper, collected in 2003 | |
| South side | 77°36.49'S, 163°14.92'E | soil | mur | Low (n = 6, 17%) | This paper, collected in 2003 | |
| South side near Green Creek | 77°37.36'S, 163°03.91'E | soil | mur | Medium (n = 20, 60%) | This paper, collected in 2003 | |
| Green Creek | 77°37.36'S, 163°03.91'E | soil | mur | Medium | (Barrett et al. 2006c) | |
| Lake Hoare | *77°38.00'S, 162°51.00'E | |||||
| North side | 77°37.49'S, 162°54.31'E | soil | mur | Low (n = 18, 6%) | This paper, collected in 1993 | |
| South side | NP, NP | soil at varying elevation | spp. | Low | (Powers et al. 1994b; 1998) | |
| South side | 77°38.00'S, 162°53.00'E | soil (0-2.5, 2.5-5, 5-10, 10-20 cm) | mur | Low | (Powers et al. 1995a) | |
| South side | 77°37.93'S, 162°53.19'E | soil at varying elevation | mur | Low (n = 150, 6%) | This paper, collected in 1995, 1998 and 2002 | |
| North side | 77°37.49'S, 162°54.31'E | soil | mur | Low | (Courtright et al. 1996) | |
| South side | 77°38.00'S, 162°53.00'E | soil | mur | Low | (Powers et al. 1998) | |
| North side | NA, NA | soil | mur | M-low (n = 8, 50%) | This paper, collected in 1999 | |
| North side | 77°37.29'S, 162°54.19'E | soil | mur | Low | (Courtright et al. 2001) | |
| South side | 77°38.02'S, 162°52.23'E | soil | mur | Low (n = 8, 13%) | This paper, collected in 2001 | |
| South side | 77°38.00'S, 162°53.00'E | soil | mur | Low | (Porazinska et al. 2002b) | |
| - | 77°37.90'S, 162°53.20'E | soil and lake sediment | mur | V-High (n = 11, 82%) | This paper, collected in 2002 | |
| South side | 77°38.02'S, 162°53.05'E | soil | mur | Low (n = 6, 17%) | This paper, collected in 2003 | |
| - | 77°37.00'S, 162°50.00'E | soil | mur | M-low | (Wall Freckman and Virginia 1998) | |
| - | NP, NP | soil | mur | M-low | (Treonis et al. 2000) | |
| South side | NA, NA | high elevation upland pond areas | spp. | Low (n = 48, 19%) | This paper, collected in 2000 | |
| - | NP, NP | 0-5 cm soil (subnivian) | mur | M-low | (Gooseff et al. 2003) | |
| South side | NP, NP | high elevation upland pond areas | spp. | M-low | (Moorhead et al. 2003) | |
| Taylor Glacier | *77°44.00'S, 162°10.00'E | windblown sediment on top of glacier | mur | Present (n = 1, 100%) | This paper, collected in 1998 | |
| Suess Glacier | *77°38.00'S, 162°40.00'E | soil nearby | frig | Present | (Timm 1971) | |
| Suess Lake | NP, NP | NP | frig | Present | (Timm 1971) | |
| Victoria Valley | *77°23.00'S, 162°00.00'E | soil | mur | Present (n = 6, 17%) | This paper, collected in 2003 | |
| Wright Valley | *77°31.39'S, 161°58.70'E | |||||
| Along Onyx River | *77°31.31'S, 161°49.39'E | pond | spp. | Present | (Timm 1971) | |
| East of Meserve Glacier | *77°31.00'S, 162°17.00'E | algal mat | spp. | Present | (Timm 1971) | |
| Canopus Pond | NP, NP | NP | frig | Present | (Timm 1971) | |
| Lake Vanda | *77°32.00'S, 161°33.00'E | lake, soil nearby | frig | Present | (Timm 1971) | |
| Lower Wright Lake (=Lake Brownworth) | *77°26.00'S, 162°45.00'E | NP | frig | Present | (Timm 1971) | |
| Edge of Lake Canopus | *77°33.00'S, 161°31.00'E | algal growth at the edge of the lake | spp. | Present | (Wharton and Brown 1989) | |
| Between Lake Vanda and Lake Bull | NP, NP | dry algae around the edge of small ponds | spp. | Present | (Wharton and Brown 1989) | |
| Between Lake Vanda and Lake Bull | NP, NP | wet algae in meltwater and around the edge of small ponds | spp. | Present | (Wharton and Brown 1989) | |
| Bull Pass | *77°28.00'S, 161°46.00'E | soil | mur | M-low (n = 22, 18%) | This paper, collected in 1990 | |
| Lake Bull | *77°31.51'S, 161°42.68'E | soil | mur | Low (n = 12, 8%) | This paper, collected in 1990 | |
| - | 77°31.00'S, 161°50.00'E | soil | mur | M-low | (Wall Freckman and Virginia 1998) | |
| Koettlitz Glacier and Southern Coastal Regions | *78°15.00'S, 164°15.00'E | |||||
| Cape Chocolate (just north of) | *77°56.05'S, 164°34.70'E | moraine | frig | Present | (Timm 1971) | |
| Marble Point | *77°26.00'S, 163°50.00'E | |||||
| - | NP, NP | moss (Bryum antarcticum) | mur | V-highA | (Yeates 1970) | |
| - | NP, NP | mossy soil and melt pools with abundant algae (Nostoc commune) | mur | Present | (Timm 1971) | |
| - | NP, NP | meltpools w/ abundant algae (Nostoc commune), mossy soil | frig | Present | (Timm 1971) | |
| Pewe Lake | NP, NP | NP | frig | Present | (Timm 1971) | |
| Strand Moraines | *77°45.04'S, 164°29.90'E | |||||
| - | NP, NP | mossy soil and melt pools with abundant algae (Nostoc commune) | spp. | Present | (Timm 1971) | |
| - | NP, NP | sandy soil, mossy soil, stream with abundant algae | frig | Present | (Timm 1971) | |
| Northern Coastal Region | ||||||
| Cape Hallett | *72°19.00'S, 170°16.00'E | |||||
| - | NP, NP | NP | spp. | Present | (Timm 1971) | |
| Willett Cove | 72°19.00'S, 170°14.00'E | soil | mur | Medium | (Barrett et al. 2006c) | |
| - | NA, NA | soil amongst penguin rookery | mur | M-low (n = 20, 30%) | This paper, collected in 2003 | |
| - | 72°19.29'S, 170°13.52'E | soil | Low (n = 67, 56%) | (Raymond et al. 2013a) | ||
| Edmonson Point | *74°20.00'S, 165°08.00'E | |||||
| -B | NP, NP | wet moss near a brook | mur | Present | (Vinciguerra 1994) | |
| - | NP, NP | soil | spp. | Present | (Bargagli et al. 1997) | |
| - | NA, NA | soil | mur | M-high (n = 10, 70%) | This paper, collected in 1996 | |
| - | NA, NA | soil | mur | NA (n = 28, 50%) | This paper, collected in 1996 | |
| - | NA, NA | soil | mur | M-low (n = 8, 63%) | This paper, collected in 2001 | |
| Gondwana Station | 74°37.57'S, 164°11.91'E | soil | Low (n = 371, 84%) | (Raymond et al. 2013a) | ||
| Luther Peak | 72°22.20'S, 169°53.10'E | soil | mur | Low (n = 40, 8%) | This paper, collected in 2003 | |
| Luther Vale South | 72°22.00'S, 169°53.00'E | soil | mur | Low | (Barrett et al. 2006c) | |
| Terra Nova Bay | *74°54.51'S, 164°27.19'E | |||||
| 600 km north and south of the Italian station | NP, NP | mosses, lichens, fresh-water sediments and penguin excrements (no details of whether Plectus occurred in all habitats or only in some) | spp. | Present | (Vinciguerra et al. 1994) | |
| Barclay Glacier | ||||||
| - | NP, NP | algae growing in meltwater | mur | Present | (Wharton and Brown 1989) | |
Habitat. All Plectus spp. of Victoria Land occupy similar habitats. They are present in soils and sediments (Ayres et al. 2007) and are frequently associated with moist environments and areas supporting algae (e.g. Nostoc commune) and moss (e.g. Bryum antarcticum) (Table 2). This is consistent with the habitats in which Plectus spp. are found in other regions of Antarctica (Andrássy 1998; Andrássy and Gibson 2007; Timm 1971; Wharton and Brown 1989; Yeates 1970).
Soil moisture is a critical factor determining the suitability of habitats for Plectus spp. Mouratov et al. (2001) studying Plectus spp. in the maritime Antarctic found that they had a preference for soil water content of 7-10%. In the McMurdo Dry Valleys, Courtright et al. (2001) similarly observed Plectus murrayi was more likely to occur in habitats with higher moisture contents. This moisture requirement may explain other distributional trends in the occurrence of Plectus. In the maritime Antarctic, Mouratov et al. (2001) found Plectus spp. abundance to be highest in the deepest soil layer they studied and under the moss, Saniona uncinata. In these environments soil moisture is likely to be higher at depth in the soil profile and also under mosses than in bare surface soil habitats. Courtright et al. (2001) also noted that Plectus murrayi were more frequently found in soils with higher NH4-N, NO3-N, organic C, and organic C/organic N ratios than other nematode genera (e.g. Scottnema). Plectus spp. seem to be sensitive to variation in soil salinity and only occur in soils with low EC (<100 mS cm-1), which typically are moist environments where salts have been leached from the soil or sediment. Shishida and Ohyama (1986) noted that Plectus frigophilus seems to prefer habitats of fresh water algae to those of mosses.
Eudorylaimus (Dorylaimida: Dorylaimidae)
There are six recognized Eudorylaimus species endemic to continental Antarctica: Eudorylaimus antarcticus (Yeates, 1970), Eudorylaimus nudicaudatus (Heyns, 1993), Eudorylaimus shirasei (Kito, Shishida & Ohyama, 1996), Eudorylaimus glacialis (Andrássy, 1998), Eudorylaimus quintus (Andrássy 2008) and Eudorylaimus sextus (Andrássy 2008). Eudorylaimus antarcticus is nearly universally reported as the sole species recovered from Victoria Land, but it has been suggested that this species is widely codistributed with Eudorylaimus glacialis (Andrássy 2008). We report both where two distinct morphotypes were observed.
Biogeographic distribution. Eudorylaimus antarcticus is widely distributed within Victoria Land (Table 3). Steiner (1916) described the original specimens, which were collected by the Discovery Expedition from Discovery Bay (no notes were made on habitat). Later studies list Eudorylaimus antarcticus from locations throughout the McMurdo Dry Valleys, (reported most frequently from Taylor Valley) and in northern Victoria Land at Edmonson Point and Terra Nova Bay (Table 3).
Table 3.
Biogeographic distribution of Eudorylaimus species in Victoria Land, Antarctica. NP = not published. NA = not available. ant = Eudorylaimus antarcticus. gla = Eudorylaimus glacialis. For abundance, Low = >0 to 20 nematodes per kg dry soil, M-low = 21 to 200 nematodes per kg dry soil, Medium = 201 to 600 nematodes per kg dry soil, M-high = 601 to 1000 nematodes per kg dry soil, High = 1001 to 2000 nematodes per kg dry soil, V-high = >2000 nematodes per kg dry soil, n = number of samples and % = percentage of samples in which Eudorylaimus occurred. AThere may have been a typographical error in the original publication reporting this longitude. BASPA = Antarctic Specially Protected Area (previously Site of Special Scientific Interest). For references to “this paper”, the year collected refers to the year at the beginning of the austral summer in which samples were collected at 0-10 cm depth.
| Biogeographic location | Lat, Long | Habitat | Species | Abundance | Reference | |
|---|---|---|---|---|---|---|
| McMurdo Dry Valleys | *77°30.00'S, 162°00.00'E | |||||
| - | NP, NP | soil | ant | Present | (Freckman and Virginia 1990) | |
| - | NP, NP | soil | ant, gla | M-low | (Freckman and Virginia 1993) | |
| - | NP, NP | soil | ant | Present | (Freckman and Virginia 1997) | |
| - | NP, NP | soil, sediment | ant | Present | (Moorhead et al. 1999) | |
| Alatna Valley | *76°52.82'S, 161°13.82'E | |||||
| Battleship Promontory | *76°54.85'S, 160°59.34'E | |||||
| - | NA, NA | soil | ant | M-low (n = 17, 65%) | This paper, collected in 1993 | |
| - | 76°55.30'S, 161°04.79'E | moist soil, green with algae and between dolomite rocks | ant | Low (n = 9, 22%) | This paper, collected in 1994 | |
| - | NA, NA | soil | ant | M-low (n = 6, 17%) | This paper, collected in 1996 | |
| Southwestern Bluff | 76°55.00'S, 161°03.00'E | soil | ant | Low (n = 14, 7%) | This paper, collected in 2001 | |
| - | NA, NA | soil | ant | Low (n = 6, 50%) | This paper, collected in 2003 | |
| Garwood Valley | *78°02.00'S, 164°10.00'E | |||||
| Garwood Lake | *78°01.58'S, 164°15.42'E | NP | ant | Present | (Timm 1971) | |
| - | NA, NA | soil | ant | M-low (n = 6, 100%) | This paper, collected in 1993 | |
| - | 78°02.00'S, 164°10.00'E | soil | ant | M-low | (Wall Freckman and Virginia 1998) | |
| - | NA, NA | soil | ant | M-low (n = 13, 23%) | This paper, collected in 2002 | |
| McKelvey Valley | *77°26.00'S, 161°33.00'E | |||||
| Upper | NA, NA | soil | ant | M-low (n = 18, 33%) | This paper, collected in 1990 | |
| Miers Valley | *78°06.00'S, 164°00.00'E | |||||
| Miers Glacier (the foot of) | *78°05.00'S, 163°40.00'E | moss | ant | Present | (Timm 1971) | |
| Runoff stream from the Miers Glacier | *78°05.00'S, 163°40.00'E | NP | ant | Present | (Timm 1971) | |
| Miers Lake | *78°06.00'S, 163°51.00'E | NP | ant | Present | (Timm 1971) | |
| - | NA, NA | soil | ant | M-low (n = 24, 50%) | This paper, collected in 1990 | |
| Taylor Valley | *77°38.82'S, 163°03.08'E | |||||
| Lake Bonney | *77°43.00'S, 162°25.00'E | |||||
| - | NP, NP | NP | ant | Present | (Timm 1971) | |
| - | NA, NA | soil | ant | Low (n = 99, 52%) | This paper, collected in 1994 | |
| - | NA, NA | soil | ant | M-low (n = 2, 100%) | This paper, collected in 1995 | |
| - | NA, NA | algal mat | ant | NA (n = 5, 60%) | This paper, collected in 1995 | |
| - | NP, NP | soil, sediment | ant | Low | (Moorhead et al. 1999) | |
| West Lobe | 77°43.50'S, 162°18.95'E | soil | ant | Low (n = 18, 61%) | This paper, collected in 1999, 2001 and 2002 | |
| - | NA, NA | soil, sediment | ant | M-low (n = 20, 35%) | This paper, collected in 2000 | |
| West Lobe | NA, NA | soil | ant | Low (n = 48, 2%) | This paper, collected in 2000 | |
| Lake Chad | *77°38.55'S, 162°45.70'E | |||||
| - | NP, NP | NP | ant | Present | (Timm 1971) | |
| - | NA, NA | soil | ant | M-low (n = 9, 56%) | This paper, collected in 1995 | |
| - | NA, NA | algal mat | ant | NA (n = 1, 100%) | This paper, collected in 1995 | |
| Lake Fryxell | *77°36.58'S, 163°09.10'E | |||||
| - | NP, NP | NP | ant | Present | (Timm 1971) | |
| - | NP, NP | algae in a drift stream near the lake | ant | Present | (Wharton and Brown 1989) | |
| - | NA, NA | plant material | ant | Present (n = 10, 100%) | This paper, collected in 1990 | |
| - | NA, NA | soil | ant | Medium (n = 26, 77%) | This paper, collected in 1990 | |
| South side | 77°35.94'S, 163°22.68'E | soil | ant | Low (n = 9, 11%) | This paper, collected in 1993 | |
| - | NA, NA | soil | ant | Low (n = 102, 41%) | This paper, collected in 1994 | |
| South side | 77°36.49'S, 163°18.95'E | soil | ant | Low (n = 18, 33%) | This paper, collected in 1996, 1998 and 2001 | |
| - | NA, NA | soil | ant | Low (n = 5, 20%) | This paper, collected in 1997 | |
| - | NA, NA | algal mat | ant | Present (n = 1, 100%) | This paper, collected in 1998 | |
| - | NA, NA | soil | ant | Medium (n = 4, 75%) | This paper, collected in 1998 | |
| Von Guerard stream/ Harnish Creek | *77°37.00'S, 163°15.00'E | stream sediments and surrounding soils | ant, gla | Medium | (Treonis et al. 1999) | |
| - | NP, NP | soil, sediment | ant | Low | (Moorhead et al. 1999) | |
| Von Guerard stream | *77°37.00'S, 163°15.00'E | soil | ant | M-low (n = 8, 63%) | This paper, collected in 1999 | |
| Huey Creek stream | *77°36.00'S, 163°06.00'E | soil | ant | M-low (n = 7, 29%) | This paper, collected in 1999 | |
| South side | 77°36.49'S, 163°14.92'E | soil | ant | M-low (n = 12, 83%) | This paper, collected in 1999 and 2001 | |
| Harnish Creek | *77°37.00'S, 163°13.00'E | soil and stream sediment | ant | Medium (n = 20, 70%) | This paper, collected in 2000 | |
| South side | NA, NA | soil | ant | M-low (n = 96, 97%) | This paper, collected in 2000, 2002 and 2003 | |
| - | 77°36.00'S, 162°15.00'E | soil | ant | Low | (Treonis et al. 2002) | |
| South side near F6 stream | 77°36.40'S, 163°15.30'E | soil and lake sediment | ant | M-low (n = 12, 33%) | This paper, collected in 2002 | |
| South side near Green Creek | 77°37.36'S, 163°03.91'E | soil | ant | Medium (n = 20, 45%) | This paper, collected in 2003 | |
| South Side near F6 stream | 77°36.72'S, 163°15.18'E | soil | ant | M-low (n = 20, 35%) | This paper, collected in 2003 | |
| Green Creek | 77°37.36'S, 163°03.91'E | soil | ? | Medium | (Barrett et al. 2006c) | |
| Von Guerard stream | *77°37.00'S, 163°15.00'E | soil | ? | M-Low | (Barrett et al. 2006c) | |
| Lake Hoare | *77°38.00'S, 162°51.00'E | |||||
| North side | 77°37.49'S, 162°54.31'E | soil | ant | Low (n = 18, 78%) | This paper, collected in 1993 | |
| South side | 77°38.03'S, 162°52.75'E | soil | ant | Low (n = 9, 33%) | This paper, collected in 1993 | |
| South side | NA, NA | soil | ant | Low (n = 12, 25%) | This paper, collected in 1993 | |
| South side | 77°37.59'S, 162°52.57'E | soil | ant | M-low (n = 56, 77%) | This paper, collected in 1993, 1994, 1995, 1996, 1997 and 2001 | |
| North side | 77°38.00'S, 162°53.00'E | soil (0-2.5, 2.5-5, 5-10, 10-20 cm) | ant | M-low | (Powers et al. 1994a) | |
| South side | NP, NP | soil at varying elevations | ant, gla | M-low | (Powers et al. 1994b) | |
| - | NA, NA | soil polygons | ant | Low (n = 104, 17%) | This paper, collected in 1994 | |
| North side | 77°38.00'S, 162°53.00'E | soil (0-2.5, 2.5-5, 5-10, 10-20 cm) | ant | M-low | (Powers et al. 1995b) | |
| South side | 77°38.00'S, 162°53.00'E | soil at varying elevations | ant | Low | (Powers et al. 1995a) | |
| South side | NA, NA | soil polygons | ant | Low (n = 24, 54%) | This paper, collected in 1995 | |
| South side | 77°37.93'S, 162°53.19'E | soil | ant | M-low (n = 150, 51%) | This paper, collected in 1995, 1998 and 2002 | |
| North side | 77°37.49'S, 162°54.31'E | soil | ant | Low | (Courtright et al. 1996) | |
| - | NP, NP | soil | ant | M-low | (Freckman and Virginia 1997) | |
| South side | 77°38.00'S, 162°53.00'E | soil | ant, gla | Medium | (Powers et al. 1998) | |
| - | NP, NP | soil, sediment | ant | Low | (Moorhead et al. 1999) | |
| North side | NA, NA | soil | ant | Low (n = 8, 38%) | This paper, collected in 1999 | |
| South side | NA, NA | soil | ant | M-low (n = 8, 75%) | This paper, collected in 1999 | |
| South side | 77°38.00'S, 162°53.00'E | soil | ant | M-low | (Treonis et al. 2000; 2002) | |
| North side | 77°37.29'S, 162°54.19'E | soil | ant | Low | (Courtright et al. 2001) | |
| South side | 77°38.07'S, 162°52.59'E | soil | ant | Low (n = 12, 58%) | This paper, collected in 2001, 2002 | |
| South side | 77°38.00'S, 162°53.00'E | soil | ant | M-low | (Porazinska et al. 2002b) | |
| - | 77°37.90'S, 162°53.20'E | soil and lake sediment | ant | M-low (n = 11, 64%) | This paper, collected in 2002 | |
| - | 77°37.00'S, 160°50.00'E | soil | ant | M-low | (Wall Freckman and Virginia 1998) | |
| - | NP, NP | soil | ant | M-low | (Treonis et al. 2000) | |
| - | NP, NP | 0-5 cm soil (subnivian) | ant | M-low | (Gooseff et al. 2003) | |
| Nussbaum Riegel | 77°38.52'S, 162°46.89'E | soil | ant | Low (n = 5, 60%) | This paper, collected in 1997 | |
| Suess Glacier, 50 m away | *77°38.00'S, 162°40.00'E | soil | ant | Present | (Timm 1971) | |
| Suess Pond | NP, NP | NP | ant | Present | (Timm 1971) | |
| Victoria Valley | *77°23.00'S, 162°00.00'E | |||||
| Lake Vida | *77°23.29'S, 161°56.05'E | NP | ant | Present | (Timm 1971) | |
| Upper | NA, NA | soil | ant | Low (n = 20, 5%) | This paper, collected in 1990 | |
| Victoria Upper Glacier | 77°17.35'S, 161°33.03'E | soil | ant | Low (n = 10, 43%) | This paper, collected in 1993 | |
| - | 77°23.00'S, 162°00.00'E | soil | ant | Low | (Wall Freckman and Virginia 1998) | |
| - | NA, NA | soil | ant | Present (n = 6, 50%) | This paper, collected in 2003 | |
| Wright Valley | *77°31.39'S, 161°58.70'E | |||||
| Between Lake Vanda and Lake Bull | NP, NP | dry algae around the edge of small ponds | ant | Present | (Wharton and Brown 1989) | |
| Dais | *77°33.00'S, 161°16.00'E | soil | ant | Low (n = 3, 67%) | This paper, collected in 2000 | |
| East of Meserve Glacier | *77°31.00'S, 162°17.00'E | algal mat | ant | Present | (Timm 1971) | |
| Labyrinth | *77°33.00'S, 160°50.00'E | |||||
| West | 77°33.04'S, 160°43.15'E | soil | ant | Low (n = 9, 89%) | This paper, collected in 1993 | |
| - | 77°33.04'S, 160°43.15'E | soil | ant | Low (n = 9, 11%) | This paper, collected in 1993 | |
| - | 77°33.04'S, 160°43.15'E | soil | ant | Low | (Courtright et al. 1996) | |
| West | 77°33.02'S, 160°43.09'E | soil | ant | Low | (Courtright et al. 2001) | |
| - | NA, NA | soil | ant | Low (n = 12, 8%) | This paper, collected in 2003 | |
| Bull Pass | *77°28.00'S, 161°46.00'E | soil | ant | Low (n = 12, 33%) | This paper, collected in 1990 | |
| Bull Lake | *77°31.51'S, 161°42.68'E | soil | ant | Low (n = 22, 5%) | This paper, collected in 1990 | |
| - | *77°28.00'S, 161°46.00'E | soil | ant | M-Low (n = 24, 12.5%) | (Poage et al. 2008) | |
| Lake Vanda | *77°32.00'S, 161°33.00'E | |||||
| - | NP, NP | NP | ant | Present | (Timm 1971) | |
| Near Lake Vanda and Péwé Lake | *77°32.00'S, 161°33.00'E | stony soil | ant | Present | (Timm 1971) | |
| Met Station | NA, NA | soil | ant | M-low (n = 2, 100%) | This paper, collected in 2002 | |
| Lake Brownworth | *77°26.00'S, 162°45.00'E | NP | ant | Present | (Timm 1971) | |
| - | NA, NA | soil | ant | Low (n = 5, 60%) | This paper, collected in 1997 | |
| - | 77°31.00'S, 161°50.00'E | soil | ant | M-low | (Wall Freckman and Virginia 1998) | |
| - | NA, NA | soil | ant | Present (n = 10, 50%) | This paper, collected in 2003 | |
| Onyx River pond | *77°32.00'S, 161°45.00'E | NP | ant | Present | (Timm 1971) | |
| Linnaeus Terrace ASPAB | 77°35.83'S, 161°05.00'E | soil | ant | Low (n = 16, 6%) | This paper, collected in 1990 | |
| Koettlitz Glacier and Southern Coastal Regions | *78°15.00'S, 164°15.00'E | |||||
| Cape Chocolate(north) | *76°56.00'S, 164°35.00'E | moraine | ant | Present | (Timm 1971) | |
| Strand Moraines | *77°45.04'S, 164°29.90'E | algal mat (in stream bed), sandy soil | ant | Present | (Timm 1971) | |
| Marble Point | *77°26.00'S, 163°50.00'E | NP | ant | Present | (Timm 1971) | |
| Northern Coastal Regions | ||||||
| Cape Adare | *71°17.00'S, 170°14.00'E | NP | ant | Present | (Timm 1971) | |
| Cape Hallett | *72°19.00'S, 170°16.00'E | |||||
| Hallett Station | *72°19.00'S, 170°16.00'E | NP | ant | Present | (Timm 1971) | |
| - | NA, NA | soil | ant | Low (n = 20, 20%) | This paper, collected in 2003 | |
| Cape Hallett | 72°19.29'S, 170°13.52'E | soil | Low (n = 67, 67%) | (Raymond et al. 2013a) | ||
| Edmonson Point | *74°20.00'S, 165°08.00'E | |||||
| - | NA, NA | soil | ant | Low (n = 10, 30%) | This paper, collected in 1996 | |
| - | NA, NA | soil | ant | Present (n = 28, 7%) | This paper, collected in 1996 | |
| - | NP, NP | NP | ant, gla | Present | (Bargagli et al. 1997) | |
| - | NA, NA | soil | ant | Low (n = 8, 25%) | This paper, collected in 2001 | |
| Gondwana Station | 74°37.57'S, 164°11.91'E | soil | ant | Low (n = 371, 37%) | (Raymond et al. 2013a) | |
| Luther Peak | *72°21.88'S, 169°50.91'E | soil | ant | M-low (n = 40, 85%) | This paper, collected in 2003 | |
| Luther Vale North | 72°22.00'S, 169°53.00'E | soil | ? | M-Low | (Barrett et al. 2006c) | |
| Luther Vale South | 72°22.00'S, 169°53.00'E | soil | ? | M-Low | (Barrett et al. 2006c) | |
| Terra Nova Bay | *74°54.51'S, 164°27.19'E | |||||
| 600 km north and south of the Italian station | NP, NP | mosses, lichens, fresh-water sediments and penguin excrement (there are no details of whether Eudorylaimus occurred in all habitats or only in some) | ant | Present | (Vinciguerra et al. 1994) | |
| Barclay Glacier | NP, NP | algae in meltwater | ant | Present | (Wharton and Brown 1989) | |
Outside of the Victoria Land region, Eudorylaimus antarcticus has been reported from several of the maritime islands (Signy, Alexander, King George, Anvers) (e.g. Maslen 1982; Mouratov et al. 2001; Shishida and Ohyama 1989; Spaull 1973a, b; Wharton and Block 1993). Andrássy (1998, 2008), in contrast, argues for a more restricted distribution within Victoria Land (Andrássy 2008).
Habitat. Eudorylaimus antarcticus in Victoria Land occurs at varying elevation and most commonly in soils and in lake sediments. The genus has also frequently been associated with algal mats, both dry and moist found in meltwater, streambeds and lakes. Eudorylaimus antarcticus has been reported less frequently in areas of moss and from soils. In contrast, outside Victoria Land (e.g. Ross Island) the occurrence of Eudorylaimus antarcticus in a moss habitat (e.g. Bryum argenteum) is common, but it does not occur in penguin rookeries (on Ross Island or in Victoria Land). In soils of the McMurdo Dry Valleys Eudorylaimus antarcticus tends to be found in soils with higher moisture, NH4-N, NO3-N, organic C, and organic C/organic N ratios, and only occurs in soils with low salinity (EC <100 mS cm-1) (Courtright et al. 2001).
Panagrolaimus (Panagrolaimida: Panagrolaimidae)
Biogeographic distribution. The Antarctic Panagrolaimus consists of two species, Panagrolaimus magnivulvatus and Panagrolaimus davidi (but see Raymond et al. 2013b). Both are endemic (Andrássy 1998). Panagrolaimus davidi is the only species recorded from Victoria Land and its occurrence is rare (see Table 4). Until the present study, the only record of Panagrolaimus davidi in Victoria Land was from Marble Point (Timm 1971). The current study shows that Panagrolaimus davidi is also present in the northern coastal region of Victoria Land, at Edmonson Point and Cape Hallett and in Miers Valley, one of the McMurdo Dry Valleys. Thus, Panagrolaimus davidi occurs most frequently in coastal regions but is not necessarily restricted to them.
Table 4.
Biogeographic distribution of Panagrolaimus davidi in Victoria Land, Antarctica. NP = not published. NA = not available. For references to “this paper”, the year collected refers to the year at the beginning of the austral summer in which samples were collected. For abundance, M-low = 21 to 200 nematodes per kg dry soil, Medium = 201 to 600 nematodes per kg dry soil, n = number of samples and % = percentage of samples in which Panagrolaimus occurred.
| Biogeographic location | Lat, Long | Habitat | Abundance | Reference | |
|---|---|---|---|---|---|
| McMurdo Dry Valleys | *77°30.00'S, 162°00.00'E | ||||
| Miers Valley | *78°06.00'S, 164°00.00'E | soil | M-low (n = 24, 29%) | This paper, collected in 1990 | |
| Southern Coastal Region | |||||
| Marble Point | *77°26.00'S, 163°50.00'E | mossy soil (Bryum antarcticum) | Present | (Timm 1971) | |
| Northern Coastal Region | |||||
| Cape Bird | 77°13.00'S, 166°26.00'E | soil in penguin rookery | Medium (n = 29, 52%) | (Porazinska et al. 2002a) | |
| Cape Crozier | 77°27.00'S, 169°11.00'E | soil in penguin rookery | M-low (n = 27, 48%) | (Porazinska et al. 2002a) | |
| Cape Hallett | *72°19.00'S, 170°16.00'E | ||||
| - | NA, NA | soil in penguin rookery | Low (n = 2, 50%) | This paper, collected in 2002 | |
| Willet Cove | 72°19.00'S, 170°14.00'E | soil | M-High | (Barrett et al. 2006c) | |
| Seabee Spit | 72°18.83'S, 170°13.00'E | soil | Low | (Barrett et al. 2006c) | |
| Cape Hallett | 72°19.29'S, 170°13.52'E | soil | M-Low (n = 56, 56%) | (Raymond et al. 2013a) | |
| Cape Royds | 77°33.00'S, 166°10.00'E | soil amongst penguin rookery | M-low (n = 66, 20%) | (Porazinska et al. 2002a) | |
| - | NA, NA | soil pits amongst penguin rookery | Med (n = 20, 70%) | This paper, collected in 2003 | |
| Edmonson Point | *74°20.00'S, 165°08.00'E | soil | Present (n = 28, 4%) | This paper, collected in 1996 | |
| Gondwana Station | 74°37.57'S, 164°11.91'E | soil | M-Low (n = 371, 34%) | (Raymond et al. 2013a) | |
Panagrolaimus davidi has been recorded from Ross Island (e.g. Freckman and Virginia 1993; Porazinska et al. 2002a; Sinclair 2001; Sinclair and Sjursen 2001; Timm 1971; Wharton and Brown 1989). Panagrolaimus spp. have also been reported from several of the maritime islands (summarized in Andrássy 1998 and references therein, see also Raymond et al. 2013b).
Habitat. Penguin rookeries and moss-covered soils appear to be the most favorable habitats for Panagrolaimus davidi in Victoria Land and are consistent with the habitats where Panagrolaimus davidi has been found in other Antarctic ice-free areas (Porazinska et al. 2002a; Sinclair 2001; this paper; Timm 1971; Wharton and Brown 1989). Evidence indicates Panagrolaimus davidi occurs in habitats of high primary productivity and soil organic matter (as does Panagrolaimus magnivulvatus) regardless of its source of origin (e.g. mosses or penguin guano) though it is primarily associated with penguin rookeries (Porazinska et al. 2002a; Sinclair and Sjursen 2001). The presence of Panagrolaimus davidi is strongly correlated with organic carbon, organic nitrogen, chlorophyll a (a measure of primary productivity) and ammonium (Porazinska et al. 2002a; Sinclair and Sjursen 2001). The species is also more abundant in the highly productive areas of moss and algae along snow melt streams than in adjacent soils (Sinclair and Sjursen 2001).
Geomonhystera (Monhysterida: Monhysteridae)
Several nematode species originally described as Monhystera were redescribed by Andrássy in 1981 as Geomonhystera. Among these was Monhystera villosa from the Antarctic (Timm 1971), which Andrássy subsequently redescribed as a new species, Geomonhystera antarcticola (Andrássy 1998). It is the only known species of Geomonhystera on the continent, thus, we report all published observations of the genus from Victoria Land as Geomonhystera antarcticola.
Biogeographic distribution. Geomonhystera antarcticola are generally rare, and along with Panagrolaimus davidi are the least abundant and most patchily distributed of all nematodes in Victoria Land. Other species of Geomonhystera occur in the islands of the maritime Antarctic (Signy, Coronation, Elephant, Intercurrence and Galindez) where Geomonhystera antarcticola is one of the most common nematode species (Maslen 1981; Newsham et al. 2004; Spaull 1973a, b, c). They were originally recorded as Monhysterid genus A. and renamed as Monhystera villosa by Maslen (1979). Newsham et al. (2004) identified specimens from Signy Island as Geomonhystera villosa.
Sohlenius et al. recorded Monhystera from the Nunataks of Dronning Maud Land, East Antarctica (Sohlenius et al. 1995, 1996), and they have also been recovered from Macquarie Island of the Sub-Antarctic (Bunt 1954) and Signy Island of the maritime Antarctic (Caldwell 1981; Maslen 1981; Spaull 1973a, b, c; Wharton and Block 1993) but only identified as Monhystera spp., so it is unknown whether these nematodes could also be Geomonhystera. Some previously recorded Monhystera of the subantarctic (Monhystera vulgaris, and Monhystera filiformis) (Bunt 1954) are not Geomonhystera but more likely Eumonhystera (Andrássy 1981) or Halomonhystera (Andrássy 2006).
Habitat. The habitat of Geomonhystera in Victoria Land differs from that of Geomonhystera as described by Andrássy (1981), and for Geomonhystera of the maritime Antarctic, and Monhystera spp. of the maritime Antarctic and Dronning Maud Land. In Victoria Land, Geomonhystera are similarly found in soil, but have also been associated with algal mats (e.g. Timm 1971; Wharton and Brown 1989) and moss carpets (Andrássy 1998, this paper). Monhystera spp. described from the Nunataks of Dronning Maud Land (Sohlenius et al. 1995; 1996) have only been found under lichens but there is no apparent link between Geomonhystera of Victoria Land and lichens.
Discussion
Nematode diversity in Victoria Land is low compared to the Antarctic Peninsula, but the presence of a few cryptic species is likely (Barrett et al. 2006c; Raymond et al. 2013b). Extensive sampling across broader geographic scales, combined with molecular techniques will likely recover additional species from both locations. With the exception of Panagrolaimus davidii and Geomonhystera spp., all species are widely distributed throughout Victoria Land, from the south coast and the most southern McMurdo Dry Valleys to the northern coastal region. This distribution suggests that their dispersal is ubiquitous and primarily by wind while in anhydrobiois (Nkem et al. 2006b), and it is the suitability of the soil habitat that determines the likelihood of population and community establishment and functioning (Virginia and Wall 1999).
Our knowledge of nematode biodiversity, distribution, and function in Victoria Land is based on clusters of studies from a few distinct regions, such as the McMurdo Dry Valleys, and far northern coastal Victoria Land, which are accessible from established research stations. The rest of Victoria Land (including other inland ice-free areas) has been largely inaccessible. Studies throughout the McMurdo Dry Valleys are also patchy with some valleys being studied heavily (e.g. Taylor Valley) whilst others (e.g. Barwick Valley) have barely been investigated. More undescribed nematodes may occur in these less studied regions.
Conclusions
Habitat suitability for each nematode species is determined primarily by variations in soil factors such as quantities and types of organic material, moisture and salinity (Nkem et al. 2006a; Virginia and Wall 1999). Scottnema lindsayae is the most abundant and widespread nematode and has a unique tolerance for a wide range of extreme soil habitats, and it is also the most tolerant to low soil moisture and high salinity of all the nematode species studied. These conditions define the most common soil habitats throughout the cold desert ecosystems of Victoria Land and explain the high abundance and broad distribution of Scottnema lindsayae throughout the region. There are less extensive suitable habitats available in Victoria Land for Plectus spp. and Eudorylaimus antarcticus as their distributions are limited to habitats with higher moisture, greater organic material and lower salinity. Panagrolaimus davidii has a very limited biogeographic distribution, almost entirely restricted to coastal Victoria Land. This species is found in habitats with high primary productivity, of which there are few. Factors defining suitable habitats and the biogeographic distribution of Geomonhystera spp. in Victoria Land are the least understood, largely due to very low abundance and limited occurrence, although they have been recovered from sites across Victoria Land. There appears to be an association with algae but little else is known of their habitat requirements.
We have made considerable progress in understanding the basic relationships between soil properties and the distribution of the key nematode taxa throughout Victoria Land. Suitable habitats can be defined by moisture, salinity, organic matter and nutrient content, and the interactions between these factors. Manipulations of soil moisture and field observations of environmental change during pulse warming events show that nematode community composition can respond on time scales of seasons to decades (Ayres et al. 2010; Doran et al. 2002). The climate of Victoria Land is expected to change with warmer conditions (Adams et al. 2009; Jones et al. 1998; Salby et al. 2011; Solomon et al. 2007; Steig et al. 2009; Thompson and Solomon 2002) leading to increasing soil moisture, redistribution of salts, and potentially higher productivity (Gooseff et al. 2011; Nielsen et al. 2012). These changes may alter the spatial distributions of suitable habitats for individual nematode species and/or alter population size and community diversity (Nielsen et al. 2011b). Studies have shown the important role of nematodes in carbon cycling, suggesting that changes in nematode biogeography will be linked with changes in ecosystem functioning in Antarctic soils (Barrett et al. 2008).
The nematofauna of Victoria Land are capable of long distance dispersal by wind (Nkem et al. 2006b) but the Antarctic continent is effectively isolated from source populations elsewhere in the southern hemisphere (Convey et al. 2008; Convey and Stevens 2007). This leaves anthropogenic dispersal by way of tourists and scientists as the primary mechanism for the movement of alien species to Antarctica (Chown et al. 2012a). From a field sample collected in Wright Valley in the 2011-2012 field season, we recovered an individual living female Cuticularia fermata, a nematode heretofore known only from South Orkney Island (subantarctic island). Whether this specimen was transported to the site on clothing or equipment used by scientists or if there are established, low-density, isolated populations in the area is unknown. It is highly likely that the frequency of nematode introductions to Victoria Land will increase as tourism and scientific research increases (Chown et al. 2012a). There is a growing international consensus that action is needed to reduce the potential introductions of invasive soil species to continental Antarctica and the Peninsula and maritime regions (Chown et al. 2012b). A greater knowledge of nematode biogeography will be essential in understanding how to protect special soil habitats to preserve existing biodiversity and to prevent the introduction of non-native species and the potential harm they cause to the unique soil ecosystems of Antarctica.
Acknowledgements
We thank Rich Alward, Jackie Aislabie, Megan Balks, Jeb Barrett, Yvonne Baskin, Steve Blecker, Pella Brinkman, Dan Bumbarger, Melody Burkins, Iain Campbell, Katie Catapano, C. Page Chamberlain, Tom Cioppa, Ericha Courtright, Nicole DeCrappeo, Joel Feldman, John Freckman, Jerry Garcia, Ian Hawes, Mengchi Ho, David Hopkins, Mary Kratz, Ed Kuhn, Kevin Levine, Elizabeth Marlies, Jen Mercer, Johnson Nkem, Phil Novis, Andy Parsons, Mike Poage, Dorota Porazinska, Laura Powers, Rusty Rodriguez, Jim Schulz, Rebekka Stucker, Amy Treonis, Lewis White, Roger Worland, and David Wynn-Williams for help collecting and processing soil samples. Ethan Adams, Eric Sokol and Ian Hogg helped process the Cuticularia fermata sample, which was collected as part of the NZ TABS project (http://nztabs.ictar.aq). This work could not have been completed without the dedicated, expert helicopter support provided by personnel of the US Coast Guard, US Navy VXE-6, Petroleum Helicopters Inc., and logistic and science support by ITT, Antarctic Support Associates, and Raytheon Polar Services. Brad Herried and Paul Morin of the Polar Geospatial Center (http://www.pgc.umn.edu) helped generate Figure 1. We very much appreciate the thoughtful, constructive criticisms of three anonymous reviewers. This research was supported by National Science Foundation Grants DPP 88-18049 and DPP 89-14655, OPP 9120123, OPP 9421025, and the McMurdo Long Term Ecological Research program (OPP 9211773, OPP 9810219).
Citation
Adams BJ, Wall DH, Virginia RA, Broos E, Knox MA (2014) Ecological Biogeography of the Terrestrial Nematodes of Victoria Land, Antarctica. ZooKeys 419: 29–71. doi: 10.3897/zookeys.419.7180
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