Terrestrial nematodes from the Maritime Antarctic

Milka Elshishka; Aleksandar Mladenov; Stela Lazarova; Vlada Peneva

doi:10.3897/BDJ.11.e102057

Biodiversity Data Journal : Taxonomy & Inventories

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Taxonomy & Inventories

Terrestrial nematodes from the Maritime Antarctic

Milka Elshishka^‡, Aleksandar Mladenov^‡, Stela Lazarova^‡, Vlada Peneva^‡

‡ Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences, 2 Gagarin Street, 1113, Sofia, Bulgaria

Corresponding author: Milka Elshishka (melshishka@gmail.com)

Academic editor: Oleksandr Holovachov

Received: 16 Feb 2023 | Accepted: 29 Aug 2023 | Published: 14 Sep 2023

This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Citation: Elshishka M, Mladenov A, Lazarova S, Peneva V (2023) Terrestrial nematodes from the Maritime Antarctic. Biodiversity Data Journal 11: e102057. https://doi.org/10.3897/BDJ.11.e102057

Abstract

Background

Soil nematodes are one of the most important terrestrial faunal groups in Antarctica, as they are a major component of soil micro-food webs. Despite their crucial role in soil processes, knowledge of their species diversity and distribution is still incomplete. Taxonomic studies of Antarctic nematodes are fragmented, which prevents assessment of the degree of endemicity and distribution of the species, as well as other aspects of biogeography.

New information

The present study is focused on the nematode fauna of one of the three Antarctic sub-regions, the Maritime Antarctic and summarises all findings published up to April 2023. A species list that includes 44 species, belonging to 21 genera, 16 families and eight orders is provided. A review of the literature on terrestrial nematodes inhabiting the Maritime Antarctic showed that the sites are unevenly studied. Three islands (Signy, King George and Livingston Islands) revealed highest species richness, probably due to the highest rates of research effort. Most species and four genera (Antarctenchus, Pararhyssocolpus, Amblydorylaimus and Enchodeloides) are endemic, proving that nematode fauna of the Maritime Antarctic is autochthonous and unique. Several groups of islands/sites have been revealed, based on their nematode fauna. The study showed that species with a limited distribution prevailed, while only two species (Plectus antarcticus and Coomansus gerlachei) have been found in more than 50% of the sites. Based on the literature data, details on species localities, microhabitat distribution, plant associations and availability of DNA sequences are provided.

Keywords

endemics, distribution, DNA sequences, species

Introduction

Soil nematodes are one of the most important groups of the terrestrial fauna in Antarctica (Maslen and Convey 2006) as they are abundant, taxonomically and functionally diverse and occupy a central position in the soil micro-food webs (Adams et al. 2014) and may have an impact on nutrient cycling and carbon dioxide emission, when soils thaw for a longer period of the year under climate change (van den Hoogen et al. 2019). In the challenging environmental conditions of the Antarctic, their distribution is limited to ice-free areas, where they have evolved throughout millions of years of climatic fluctuations in refugia (Ebach et al. 2008, Convey et al. 2020, Stevens and Mackintosh 2023). The glaciations, long-term isolation, harsh climate and the patchy distribution of ice-free areas (present today where at least partially ice-free throughout repeated glacial maxima (Newman et al. 2009)) are the main factors affecting the Antarctic nematode fauna origin/genesis (i.e. the formation of fauna under the influence of multiple factors - historical, geographic and ecological) (Andrássy 1998, Convey and Peck 2019). In order to survive in the extreme environments, nematodes have developed exceptional cryptobiotic adaptations to manage freezing and desiccation stress (e.g. Pickup (1988), Wharton (1995), Treonis and Wall (2005), Kagoshima et al. (2019)).

Knowledge of the impact of climate change on nematode communities from extreme habitats and how they respond to these changes is insufficient (Freckman and Virginia 1997, Nielsen et al. 2011a). One of the main problems in predicting the effects of climate change in Antarctica is the limited knowledge on the diversity of terrestrial fauna, especially nematodes and the lack of comprehensive long-term studies (Gantait 2014). Data on species distribution and biogeography are not enough and the taxonomic information still remains confused or scarce (Andrássy 1998, Maslen and Convey 2006, Adams et al. 2014, Kagoshima et al. 2019). Nematodes possess high indicator potential for assessing various environmental changes in the soil environment because they are abundant, ubiquitous, utilise diverse trophic and live strategies and, thus, occupy key positions in soil micro-food webs (Neher 2001, Ferris et al. 2001, Neher 2010, Chauvin et al. 2020, Taylor et al. 2020, Ara Khanum et al. 2022, Du Preez et al. 2022). This highlights the need for research on the fauna of nematodes and their communities in extreme environments in view of the already occurring global change.

Antarctica represents three distinct climatic regions: the Sub-Antarctic, Maritime and Continental Antarctic (Holdgate 1977), with the Sub-Antarctic being the most favourable (mean air temperatures of most islands are low, but positive during the whole year), with the Continental Antarctic having the harshest conditions (the average monthly temperatures remain below freezing) (Convey 2017). The Continental Antarctic covers the territories of the continent, the Balleny Islands and the eastern side of the Antarctic Peninsula (Convey 2017). The Sub-Antarctic is the boundary zone that lies north of 56°S (Chown and Brooks 2019). The flora and fauna in this region are rather typical of temperate latitudes. In this paper, we focused on terrestrial nematodes from the Maritime Antarctic. This is a region with a strong influence of the Southern Ocean; it includes the western coast of the Antarctic Peninsula to ca. 72°S, the South Shetland, South Orkney and South Sandwich Islands and the isolated Bouvetøya and Peter I Øya (Convey 2006, Convey 2017). The Maritime Antarctic is characterised by more favourable conditions compared with the Continental Antarctic: mean air temperatures are positive for 1–4 months of the year (Convey 2017), the vegetation is predominantly cryptogamic (algae, mosses, liverworts, lichens); higher plants are represented by two species, Deschampsia antarctica Desv. (Poaceae) and Colobanthus quitensis Bartl. (Caryophyllaceae) (Greene 1970, Longton 1979, Smith 1984).

Studies on nematodes in the Maritime Antarctic started at the beginning of the 20^th century, with the contribution of the Romanian biologist Emil Racoviţă during the first scientific Antarctic expedition in winter (Andrássy 1998). This resulted in a description of the first Antarctic nematode species, Mononchus gerlachei (= Coomansus gerlachei (de Man 1904) Jairajpuri and Khan 1977), followed by three other species, Plectus antarcticus de Man 1904, P. belgicae de Man 1904 and Dorylaimus sp. Following these first data, targeted investigations on the terrestrial nematode fauna from this part of Antarctica started from the early 70s of the 20^th century (Spaull 1972, Spaull 1973a, Spaull 1973b, Spaull 1973c, Loof 1975, Maslen 1979a, Maslen 1979b, Caldwell 1981, Maslen 1981, Spaull 1981, Pickup 1988, Shishida and Ohyama 1989, Tsalolikhin 1989, Pickup 1990, Janiec 1996, Peneva et al. 1996, Andrássy 1998, Peneva and Chipev 1999, Convey et al. 2000, Nedelchev and Peneva 2000, Peneva et al. 2002, Convey and Wynn-Williams 2002, Holovachov and Bostrom 2006, Maslen and Convey 2006, Nedelchev and Peneva 2007, Kito 2009, Peneva et al. 2009, Nielsen et al. 2011b, Velasco-Castrillón and Stevens 2014, Velasco-Castrillón et al. 2014a, Russell et al. 2014, Elshishka et al. 2015a, Elshishka et al. 2015b, Elshishka et al. 2017, Kagoshima et al. 2019, Newsham et al. 2020). Antarctic nematodes have been studied mainly in easy to access areas near to the research bases/stations; therefore, there are still many remote locations never sampled for nematodes which raise questions on how widespread the species are (Adams et al. 2014, Convey et al. 2020).

According to Andrássy (1998), numerous studies have reported species as new records with no morphological description making it impossible to confirm identifications, especially when the collected material is no longer available for subsequent examination. Further, this has an impact on the potential to assess fauna endemicity, which is critical for examining Antarctic biogeography within a global context (Andrássy 1998). There are numerous cases of misclassification and underestimation of the diversity for most microfaunal groups in Antarctica, likely due to poor taxonomic resolution caused by insufficient sampling and their difficult identification (Adams et al. 2006, Iakovenko et al. 2015, Carapelli et al. 2017, Short et al. 2022, Collins et al. 2023), as well as the low degree of the development and application of molecular taxonomy.

In recent years, molecular studies have become more important in these marginal habitats, as a powerful toolkit to complement the traditional taxonomy, species identification and descriptions and to assess biodiversity and biogeography (Courtright et al. 2000, Velasco-Castrillón et al. 2014b, Elshishka et al. 2015b, Elshishka et al. 2017, Czechowski et al. 2017, Velasco-Castrillón et al. 2018, Kagoshima et al. 2019).

The integrative approach (combining morphological and molecular data) is an effective way to understand the scale of endemism, evolution and distribution of the Antarctic nematode fauna. However, the main problem of not linking molecular data with morphology still remains for the vast majority of Antarctic nematode species.

The present paper aims to summarise all records of nematode species occurrence in the Maritime Antarctic between the years of 1904 and April 2023 as a basis for further studies and to present a snapshot of nematode species diversity in this part of the Antarctic.

Materials and methods

The nematode species list has been composed, based on literature data and refers to the Maritime Antarctic. This list includes all species recovered in the Maritime Antarctic, as well as the islands and sites from where each species was reported, along with data on microhabitats and plant associations, accession numbers of published sequences in GenBank also included, if available. The type of microhabitat is reported as in the original paper, the scientific names of the plants being adapted according to the current systematics (Ochyra 1998). Geographical coordinates are presented additionally for each site if missing in the original paper. For the literature search, online bibliography search engine Google Scholar and the academic databases Scopus, Web of Science and CABI were used with search keywords “terrestrial nematode species*” and “Maritime Antarctic*”. We focused on studies reporting nematode species (see Holovachov (2014a)) from the Maritime Antarctic and omitted those that provide data only at the generic or family level.

Several papers recording multiple unidentified taxa at generic level (Maslen and Convey 2006, Nielsen et al. 2011b) probably contain many undescribed nematode species from those regions suggesting that the nematode diversity there might be underestimated to a great extent. Overall, nematodes from 37 sites (34 islands and three localities on the Antarctic Peninsula) are included in the review. The taxonomic position of the Antarctic species was presented according to the current nematode nomenclature. Classification follows Andrássy (2005), Andrássy (2007) and Andrássy (2009); only for order Plectida classification follows Holovachov (2014b). The analyses are based on species presence/absence data and Wizard > Matrix display function in PRIMER v.7.0 software (Clarke and Gorley 2015). The Matrix display wizard performs a sequence of sample and species resemblance calculations and clustering and seriation steps resulting in a shade plot which visualises the species presence/absence data and sites similarity.

Checklist of terrestrial nematodes from the Maritime Antarctic

Order Dorylaimida

Family Nordiidae

Enchodeloides signyensis (Loof, 1975) Elshishka, Lazarova, Radoslavov, Hristov, Peneva, 2017

Nomenclature:

Enchodelus signyensis Loof, 1975

Family Qudsianematidae

Eudorylaimus coniceps Loof, 1975

Eudorylaimus pseudocarteri Loof, 1975

Eudorylaimus spaulli Loof, 1975

Eudorylaimus verrucosus Loof, 1975

Eudorylaimus cf. carteri Andrassy, 1959 (Bastian, 1865)

Family Pararhyssocolpidae

Pararhyssocolpus paradoxus (Loof, 1975) Elshishka, Lazarova, Radoslavov, Hristov, Peneva, 2015

Nomenclature:

Eudorylaimus paradoxus Loof, 1975|Rhyssocolpus paradoxus (Loof, 1975) Andrássy, 1986

Family Dorylaimidae

Calcaridorylaimus signatus (Loof, 1975) Andrássy, 1981

Nomenclature:

Mesodorylaimus signatus Loof, 1975

Mesodorylaimus antarcticus Nedelchev and Peneva, 2000

Mesodorylaimus chipevi Nedelchev and Peneva, 2000

Mesodorylaimus imperator Loof, 1975

Mesodorylaimus masleni Nedelchev and Peneva, 2000

Family Aporcelaimidae

Amblydorylaimus isokaryon (Loof, 1975) Andrássy, 1998

Nomenclature:

Eudorylaimus isokaryon Loof, 1975

Order Aphelenchida

Family Aphelenchoididae

Aphelenchoides haguei Maslen, 1979

Aphelenchoides vaughani Maslen, 1979

Laimaphelenchus helicosoma (Maslen, 1979) Peneva and Chipev, 1999

Nomenclature:

Aphelenchoides helicosoma Maslen, 1979

Order Alaimida

Family Amphidelidae

Paramphidelus antarcticus Tsalolikhin, 1989

Order Monhysterida

Family Monhysteridae

Eumonhystera filiformis (Bastian, 1865) Andrássy, 1981

Eumonhystera vulgaris (de Man, 1880) Andrássy, 1981

Geomonhystera villosa (Bütschli, 1873) Andrássy, 1981

Order Plectida

Family Plectidae

Plectus antarcticus de Man, 1904

Plectus cf. antarcticus de Man, 1904

Plectus belgicae de Man, 1904

Plectus cf. belgicae de Man, 1904

Plectus insolens Andrássy, 1998

Plectus tolerans Andrássy, 1998

Plectus cf. tolerans Andrássy, 1998

Plectus meridianus Andrássy, 1998

Plectus cf. meridianus Andrássy, 1998

Plectus armatus Bütschli, 1873

Nomenclature:

Ceratoplectus armatus (Bütschli, 1873) Andrássy, 1984

Order Tylenchida

Family Psilenchidae

Antarctenchus hooperi Spaull, 1972

Family Anguinidae

Ditylenchus parcevivens Andrássy, 1998

Order Rhabditida

Family Teratocephalidae

Teratocephalus tilbrooki Maslen, 1979

Teratocephalus pseudolirellus Maslen, 1979

Teratocephalus rugosus Maslen, 1979

Family Cephalobidae

Acrobeloides arctowskii Holovachov and Boström, 2006

Cervidellus cf. vexilliger (de Man, 1880) Thorne, 1937

Family Rhabditidae

Cuticularia firmata Andrássy, 1998

Rhabditis krylovi Tsalolikhin, 1989

Rhabditis marina-group

Family Peloderidae

Pelodera teres-group

Pelodera strongyloides-group

Pelodera parateres-group

Order Mononchida

Family Mononchidae

Coomansus gerlachei (de Man, 1904) Jairajpuri and Khan, 1977

Nomenclature:

Mononchus gerlachei de Man, 1904|Clarkus gerlachei (de Man, 1904) Jairajpuri, 1970

Analysis

Results

To date, 44 species of terrestrial nematodes, belonging to 21 genera, 16 families and eight orders have been recorded in the Maritime Antarctic (Table 1, Fig. 1). Nematodes have been reported from 34 islands and three sites on the Antarctic Peninsula (Fig. 2). Several groups of islands/sites have been revealed, based on their nematode fauna. Those groups form a gradient from north (the group of Livingston, King George and Signy Islands) to south (the group of Adelaide, Charcot, Alexander, Leonie and Alamode Islands).

Table 1.

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Distribution of terrestrial nematodes in the Maritime Antarctic.

* Taxonomic paper; ** Paper with molecular data; ***Paper with molecular and morphologica data

Terrestrial reference sites (SIRS) at Signy Island for long-term monitoring of the various biotic and abiotic components of Antarctic moss-peat communities (for full descriptions, see Tilbrook (1973)). These sites no longer exist and no studies have been done since the late 1980s.

SIRS 1 (Polytrichastrum alpinum (Hedwig), Chorisodontium aciphyllum (Hook. f. & Wilson) Broth. (60°43.5'S, 45°35.6'W))

SIRS 2 (Sanionia uncinata (Hedw.), Warnstorfia sarmentosa (Wahlenb.), Warnstorfia laculosa (Müll. Hal.), Cephaloziella varians (Gottsche) Steph. (60°43.7'S, 45°36'W))

¹ Geographical coordinates according to original paper. ² Geographical coordinates additionally added.

Nematode species	Locality / Coordinates	Microhabitat and plant species	DNA / Accesion number in GenBank	Reference
Enchodeloides signyensis	Signy Island (type locality) ^1,2 60°43’S, 45°38’W	Syntrichia filaris (Müll. Hal.) (type habitat); D. antarctica; C. quitensis		Loof (1975) *
				Maslen (1979b)
		SIRS 1; SIRS 2		Caldwell (1981)
		SIRS 1; SIRS 2		Maslen (1981)
	Alamode Island ^1,2 68°43'S, 67°32'W	S. uncinata		Loof (1975)*
				Maslen (1979b)
		Moss		Maslen and Convey (2006)
	Alexander Island ² 71°0′0″S, 70°0′0″W	Moss, lichen, soil, microbial mat		Maslen and Convey (2006)
	Alexander Island¹71°52’40’’S, 68°15’57’’W			Convey and Wynn-Williams (2002)
	Blaiklock Island ^1,2 67°33’S, 67°00’W	P. alpinum, Pohlia nutans (Hedw.)		Loof (1975) *
	Blaiklock Island ^1,2 67°33’S, 67°00’W			Maslen (1979b)
	Coronation Island ^1,2 60°38’S, 45°35’W	D. antarctica		Loof (1975)*
	Coronation Island ^1,2 60°38’S, 45°35’W			Maslen (1979b)
	Charcot Island ^1,2 69°45'S, 75°15'W	Soil, moss clumps, algae, various lichens		Convey et al. (2000)
	Charcot Island ^1,2 69°45'S, 75°15'W	Moss, lichen, soil		Maslen and Convey (2006)
	Dream Island ² 64°44′0″S, 64°14′0″W	Moss mats with green algae		Shishida and Ohyama (1989)*
	Elephant Island ^1,2 61°10’S, 55°14’W	D. antarctica; Polytrichum sp.		Loof (1975)*
	Elephant Island ^1,2 61°10’S, 55°14’W			Maslen (1979b)
	Galindez Island ^1,2 65°15'S, 64°15'W	D. antarctica		Loof (1975)*
	Galindez Island ^1,2 65°15'S, 64°15'W			Maslen (1979b)
	King George Island ¹ 62°09‘32“S, 58°27‘58“W	D. antarctica, C. quitensis, Sanionia sp., S. filaris, Syntrichia magellanica (Mont.)		Russell et al. (2014)
	King George Island ² 62°2′S, 58°21′W	Moist brown soil without vegetation, surrounded by moss	18S rDNA KY881720.1 28S rDNA KY881719.1	Elshishka et al. (2017)***
	Livingston Island ² 62°36′S, 60°30′W	D. antarctica; D. antarctica+S. uncinata; D. antarctica+S. uncinata+C. quitensis; P. alpinum; S. uncinata; Bryum sp.; Usnea sp.+P. alpinum; Cladonia sp.+S. uncinata+P. alpinum; Polytrichum juniperinum Hedw.+S. uncinata; S. uncinata+Bartramia patens Brid.		Peneva et al. (2002)*
				Elshishka et al. (2015a)
		Moss; Soil under moss crust; Soil		Elshishka et al. (2017)*
Eudorylaimus coniceps	Signy Island (type locality) ^1,2 60°43’S, 45°38’W	S. filaris (type habitat); Andreaea gainii Card.; C. quitensis; W. laculosa and W. sarmentosa		Loof (1975)*
		SIRS 1		Maslen (1979b)
		SIRS 2		Maslen (1981)
		Andreaea sp.		Pickup (1988)
				Wharton and Block (1993)
	Alexander Island ² 71°0′0″S, 70°0′0″W	Moss, lichen, soil, microbial mat		Maslen and Convey (2006)
	Ardley Island ¹ 62°12‘38“S, 58°56‘40“W			Russell et al. (2014)
	Charcot Island ^1,2 69°45'S, 75°15'W	Soil, moss clumps, algae, various lichens		Convey et al. (2000)
	Charcot Island ^1,2 69°45'S, 75°15'W	Moss, lichen, soil		Maslen and Convey (2006)
	Coronation Island ^1,2 60°38’S, 45°35’W	D. antarctica		Loof (1975)*
	Coronation Island ^1,2 60°38’S, 45°35’W			Maslen (1979b)
	Elephant Island ^1,2 61°10’S, 55°14’W	D. antarctica		Loof (1975)*
	Elephant Island ^1,2 61°10’S, 55°14’W			Maslen (1979b)
	Emperor Island ^1,2 67°52'S, 68°43'W	S. uncinata and Bryum pseudotriquetrum (Hedw.)		Loof (1975)*
	Emperor Island ^1,2 67°52'S, 68°43'W			Maslen (1979b)
	Guebriant Island ² 67°48′S, 68°25′W			Maslen (1979b)
	Halfmoon Island ¹ 62°35‘45“S, 59°54‘06“W			Russell et al. (2014)
	King George Island ² 62°2′S, 58°21′W	Mosses		Kito (2009)
	King George Island ¹62°11‘48“S, 58°59‘28“W; 62°11‘50“S, 58°56‘33“W; 62°11‘53“S, 58°56‘47“W			Russell et al. (2014)
	Leonie Island ² 67°36′S, 68°21′W	Mixture of soil, moss, lichen, liverworts, algae and cyanobacteria	18S rDNA LC457670.1 LC457669.1 LC457668.1 LC457667.1 LC457666.1 LC457665.1 LC457664.1 LC457663.1 LC457662.1 LC457647.1 LC457646.1 LC457645.1	Kagoshima et al. (2019)**
	Livingston Island ² 62°36′S, 60°30′W			Elshishka et al. (2015a)
E. pseudocarteri	Signy Island (type locality) ¹ 60°43’S, 45°38’W	A. gainii (type habitat); W. laculosa and W. sarmentosa; D. antarctica		Loof (1975)*
				Maslen (1979b)
		SIRS 1; SIRS 2		Maslen (1981)
		Andreaea sp.		Pickup (1988)
				Wharton and Block (1993)
	Adelaide Island ² 67°15′S, 68°30′W	Moss, lichen		Maslen and Convey (2006)
	Alexander Island ² 71°0′0″S, 70°0′0″W	Moss, lichen, soil, microbial mat, freshwater		Maslen and Convey (2006)
	Ardley Island ¹ 62°12‘38“S, 58°56‘40“W			Russell et al. (2014)
	Charcot Island ^1,2 69°45'S, 75°15'W	Moss, lichen, soil		Maslen and Convey (2006)
	Coronation Island ^1,2 60°38’S, 45°35’W	D. antarctica		Loof (1975)*
	Coronation Island ^1,2 60°38’S, 45°35’W			Maslen (1979b)
	Elephant Island ^1,2 61°10’S, 55°14’W	Polytrichum sp.		Loof (1975)*
	Elephant Island ^1,2 61°10’S, 55°14’W			Maslen (1979b)
	King George Island ² 62°2′S, 58°21′W	Puddle		Tsalolikhin (1989)*
	King George Island ¹62°09‘32“S, 58°27‘58“W; 62°11‘48“S, 58°59‘28“W; 62°11‘50“S, 58°56‘33“W			Russell et al. (2014)
	Livingston Island ¹ 62°39‘14“S, 60°36‘39“W			Russell et al. (2014)
E. spaulli	Alamode Island (type locality) ^1,2 68°43'S, 67°32'W	Soil around S. uncinata (type habitat)		Loof (1975)*
		Moss, lichen, soil, microbial mat		Maslen and Convey (2006)
				Maslen (1979b)
	Adelaide Island ² 67°15′S, 68°30′W	Moss, lichen		Maslen and Convey (2006)
	Alexander Island ² 71°0′0″S, 70°0′0″W	Moss, lichen, soil, microbial mat
	Anchorage Island ² 67°36′14.01″S, 68°12′32.78″W	Moss, grass, lichen, soil, microbial mat, freshwater
	Blaiklock Island ^1,2 67°33’S, 67°00’W	P. alpinum, Pohlia nutans		Loof (1975)*
	Blaiklock Island ^1,2 67°33’S, 67°00’W			Maslen (1979b)
	Charcot Island ^1,2 69°45'S, 075°15'W	Soil, moss clumps, algae, various lichens		Convey et al. (2000)
	Charcot Island ^1,2 69°45'S, 075°15'W	Moss, lichen, soil		Maslen and Convey (2006)
	Coronation Island ^1,2 60°38'S, 45°35'W	D. antarctica		Loof (1975)*
	Coronation Island ^1,2 60°38'S, 45°35'W			Maslen (1979b)
	Deception Island ² 62°58′37″S, 60°39′0″W			Maslen (1979b)
	Elephant Island ^1,2 61°10’S, 55°14’W	D. antarctica; Polytrichum sp.		Loof (1975)*
	Elephant Island ^1,2 61°10’S, 55°14’W			Maslen (1979b)
	Leonie Island ² 67°36′S, 68°21′W	Moss, grass, lichen, soil, microbial mat, freshwater		Maslen and Convey (2006)
	Limpet Island ^1,2 67°38'S, 68°19'W	S. uncinata		Loof (1975)*
	Limpet Island ^1,2 67°38'S, 68°19'W			Maslen (1979b)
	Pourquoi pas Island ² 67°41S, 67°28′W			Maslen (1979b)
	Signy Island ^1,2 60°43’S, 45°38’W	S. filaris B . pseudotriquetrum; D. antarctica; W. laculosa and W. sarmentosa		Loof (1975)*
				Wharton and Block (1993)
		Andreaea sp.		Pickup (1988)
				Maslen (1979b)
		SIRS 2		Maslen (1981)
E. verrucosus	Elephant Island (type locality) ^1,2 61°10’S, 55°14’W	D. antarctica (type habitat)		Loof (1975)*
	Elephant Island (type locality) ^1,2 61°10’S, 55°14’W			Maslen (1979b)
	Adelaide Island ² 67°15′S, 68°30′W	Moss, lichen, soil, microbial mat		Maslen and Convey (2006)
	Signy Island ¹ 60°43’S, 45°38’W			Maslen (1979b)
		SIRS 1; SIRS 2		Maslen (1981)
				Wharton and Block (1993)
Eudorylaimus cf. carteri	Livingston Island ² 62°36′S, 60°30′W			Elshishka et al. (2015a)
Pararhyssocolpus paradoxus	Signy Island (type locality) ¹ 60°43’S, 45°38’W	A. gainii (type habitat); S. filaris		Loof (1975)*
				Maslen (1979b)
		SIRS 1; SIRS 2		Maslen (1981)
	Adelaide Island ² 67°15′S, 68°30′W	Moss, lichen, soil, microbial mat		Maslen and Convey (2006)
	Adelaide Island ¹ 67°34.429'S, 68°07.284'W	C. varians and S. uncinata		Newsham et al. (2020)
	Anchorage Island ² 67°36′14.01″S, 68°12′32.78″W	Moss, grass, lichen, soil, microbial mat, freshwater		Maslen and Convey (2006)
	Blaiklock Island ^1,2 67°33’S, 67°00’W			Maslen (1979b)
	Coronation Island ^1,2 60°38'S, 45°35'W	D. antarctica		Loof (1975)*
	Coronation Island ^1,2 60°38'S, 45°35'W			Maslen (1979b)
	Elephant Island ^1,2 61°10’S, 55°14’W	S. uncinata		Loof (1975)*
	Elephant Island ^1,2 61°10’S, 55°14’W			Maslen (1979b)
	Galindez Island ^{1, 2} 65°15'S, 64°15'W	D. antarctica		Loof (1975)*
	Galindez Island ^{1, 2} 65°15'S, 64°15'W			Maslen (1979b)
	Guebriant Island ² 67°48′S, 68°25′W			Maslen (1979b)
	Intercurrence Island ^1,2 63°55'S, 61°24'W	Brachythecium sp.		Loof (1975)*
	Intercurrence Island ^1,2 63°55'S, 61°24'W			Maslen (1979b)
	King George Island ² 62°2′S, 58°21′W			Kito (2009)
	King George Island ² 62°2′S, 58°21′W	Soil	18S rDNA KM092521.1 28S rDNA KM092522.1	Elshishka et al. (2015b)***
	King George Island ¹62°09‘32“S, 58°27‘58“W; 62°11‘48“S, 58°59‘28“W; 62°11‘50“S, 58°56‘33“W; 62°11‘53“S, 58°56‘47“W			Russell et al. (2014)
	Leonie Island ² 67°36′S, 68°21′W	Moss, grass, lichen, soil, microbial mat, freshwater		Maslen and Convey (2006)
	Limpet Island ^1,2 67°38'S, 68°19'W	S. uncinata		Loof (1975)*
	Limpet Island ^1,2 67°38'S, 68°19'W			Maslen (1979b)
	Livingston Island ² 62°36′S, 60°30′W			Elshishka et al. (2015a)
	Livingston Island ² 62°36′S, 60°30′W	Sanionia sp.; C. quitensis, D. antarctica, moss; D. antarctica, C. quitensis; D. antarctica, moss		Elshishka et al. (2015b)*
	Nelson Island ² 62°18′S, 59°3'W	Moss		Elshishka et al. (2015b)*
Calcaridorylaimus signatus	Signy Island (type locality) ¹ 60°43’S, 45°38’W	S. filaris (type habitat); B. pseudotriquetrum; C. quitensis; D. antarctica; Prasiola crispa (Lightfoot)		Loof (1975)*
				Maslen (1979b)
		SIRS1		Caldwell (1981)
		SIRS 1; SIRS 2		Maslen (1981)
		Soil, moss, lichen, liverworts, algae and cyanobacteria	18S rDNA LC457654.1 LC457653.1 LC457652.1 LC457651.1 LC457650.1 LC457649.1 LC457648.1	Kagoshima et al. (2019)**
	Alamode Island ² 68°43'S, 67°32'W	Moss, lichen, soil		Maslen and Convey (2006)
	Alexander Island ² 71°0′0″S, 70°0′0″W	Moss, lichen, soil, microbial mat
	Anchorage Island ² 67°36′14.01″S, 68°12′32.78″W	Moss, grass, lichen, soil, microbial mat, freshwater
	Anvers Island, Biscoe Point ² 64°49′6.85″S, 63°46′32.29″W	Soil around roots of D. antarctica		Shishida and Ohyama (1989)*
	Coronation Island ^1,2 60°38'S, 45°35'W	D. antarctica		Loof (1975)*
	Coronation Island ^1,2 60°38'S, 45°35'W			Maslen (1979b)
	Dream Island ² 64°44′0″S, 64°14′0″W	Moss mats with green algae		Shishida and Ohyama (1989)*
	Galindez Island ^1,2 65°15'S, 64°15'W	D. antarctica		Loof (1975)*
	Galindez Island ^1,2 65°15'S, 64°15'W			Maslen (1979b)
	Leonie Island ² 67°36′S, 68°21′W	Moss, grass, lichen, soil, microbial mat, freshwater		Maslen and Convey (2006)
Mesodorylaimus antarcticus	Livingston Island (type locality) ¹ 62°39'22’’S, 60°21'13’’W	Sanionia sp. (type habitat); D. antarctica; D. antarctica-Polytrichum sp.; A small moss tuft Sanionia sp.; A mix grass-moss spot D. antarctica+Sanionia sp.		Nedelchev and Peneva (2000)*
	King George Island ¹62°09‘32“S, 58°27‘58“W; 62°11‘48“S, 58°59‘28“W; 62°11‘50“S, 58°56‘33“W			Russell et al. (2014)
	Neko Harbour, Antarctic Peninsula ¹ 64°50‘41“S, 62°31‘53“W			Russell et al. (2014)
M. chipevi	Livingston Island (type locality) ¹ 62°34'48’’S, 60°20'42’’W	D. antarctica on the top of flat rock near sea (type habitat); Shallow soil with cover of green algae amongst grass on a rock; Small tuft of D. antarctica; Polytrichum sp.+S. uncinata+D. antarctica; A mix grass-moss spot D. antarctica+Sanionia sp.; A large pure grass spot D. antarctica		Nedelchev and Peneva (2000)*
	Livingston Island ¹ 62°38'52’’S, 60°22'24’’W	S. georgico-uncinata Müll. Hal. + D. antarctica		Nedelchev and Peneva (2007)*
	King George Island ¹ 62°09‘32“S, 58°27‘58“W			Russell et al. (2014)
M. imperator	Emperor Island (type locality) ^1,2 67°52'S, 68°43'W	S. uncinata and B. pseudotriquetrum (type habitat)		Loof (1975)*
	Emperor Island (type locality) ^1,2 67°52'S, 68°43'W			Maslen (1979b)
	Adelaide Island ² 67°15′S, 68°30′W	Moss, lichen, soil		Maslen and Convey (2006)
	Alamode Island ² 68°43'S, 67°32'W	Moss
	Alexander Island ² 71°0′0″S, 70°0′0″W	Moss, grass, lichen, soil, microbial mat, freshwater
	Anchorage Island ² 67°36′14.01″S, 68°12′32.78″W	Moss, grass, lichen, soil, microbial mat, freshwater		Maslen and Convey (2006)
	Charcot Island ^1,2 69°45'S, 075°15'W	Soil, moss clumps, algae, various lichens		Convey et al. (2000)
	Cone Island ^1,2 67°41'S, 69°10'W	S. uncinata		Loof (1975)*
	Cone Island ^1,2 67°41'S, 69°10'W			Maslen (1979b)
	Killinbeck Island ² 67°34′S, 68°5′W	Moss, lichen, soil		Maslen and Convey (2006)
	Leonie Island ² 67°36′S, 68°21′W	Moss, grass, lichen, soil, microbial mat, freshwater		Maslen and Convey (2006)
M. masleni	Livingston Island (type locality) ¹ 62°39'46’’S, 60°23'29’’W	A large area of D. antarctica (type habitat); A mix grass-moss spot D. antarctica + Sanionia sp.		Nedelchev and Peneva (2000)*
Amblydorylaimus isokaryon	Elephant Island (type locality) ^1,2 61°10’S, 55°14’W	D. antarctica (type habitat); Polytrichum sp.		Loof (1975)*
	Elephant Island (type locality) ^1,2 61°10’S, 55°14’W			Maslen (1979b)
	Galindez Island ^1,2 65°15'S, 64°15'W	D. antarctica		Loof (1975)*
	Galindez Island ^1,2 65°15'S, 64°15'W			Maslen (1979b)
	Intercurrence Island ^1,2 63°55'S, 61°24'W	Brachythecium sp.		Loof (1975)*
	Intercurrence Island ^1,2 63°55'S, 61°24'W			Maslen (1979b)
	King George Island ² 62°2′S, 58°21′W			Kito (2009)
	King George Island ² 62°2′S, 58°21′W	Soil		Elshishka et al. (2015b)*
	Livingston Island ² 62°36′S, 60°30′W			Elshishka et al. (2015a)
	Livingston Island ² 62°36′S, 60°30′W	Grass spot (D. antarctica); a moss- grass (D. antarctica- Polytrichum sp.) community; S. georgico-uncinata and D. antarctica; C. quitensis and D. antarctica, moss; D. antarctica and C. quitensis		Elshishka et al. (2015b)*
	Nelson Island ² 62°18′S, 59°3′W	Moss	18S rDNA KM092519.1 28S rDNA KM092520.1	Elshishka et al. (2015b)***
Aphelenchoides haguei	Signy Island (type locality) ¹ 60°43’S, 45°38’W	SIRS 1 (type habitat); SIRS 2		Maslen (1979a)*
	Signy Island (type locality) ¹ 60°43’S, 45°38’W	SIRS 1; SIRS 2		Maslen (1981)
	Adelaide Island ² 67°15′S, 68°30′W	Moss, lichen		Maslen and Convey (2006)
	Adelaide Island ¹ 67°34.429'S, 68°07.284'W	C. varians and S. uncinata		Newsham et al. (2020)
	Alamode Island ²68°43'S, 67°32'W	Moss		Maslen and Convey (2006)
	Alexander Island ² 71°0′0″S, 70°0′0″W	Moss, lichen, soil, microbial mat
	Anchorage Island ² 67°36′14.01″S, 68°12′32.78″W	Moss, grass, lichen, soil, microbial mat, freshwater
	Ardley Island ¹ 62°12‘38“S, 58°56‘40“W			Russell et al. (2014)
	Deception Island ¹ 62°58‘42“S, 60°33‘29“W			Russell et al. (2014)
	King George Island ¹62°09‘32“S, 58°27‘58“W; 62°11‘48“S, 58°59‘28“W; 62°11‘50“S, 58°56‘33“W; 62°11‘53“S, 58°56‘47“W			Russell et al. (2014)
	Leonie Island ² 67°36′S, 68°21′W	Moss, grass, lichen, soil, microbial mat, freshwater		Maslen and Convey (2006)
	Livingston Island ¹ 62°39‘14“S, 60°36‘39“W	Soil		Russell et al. (2014)
	Livingston Island ² 62°36′S, 60°30′W			Elshishka et al. (2015a)
A. vaughani	Signy Island (type locality) ¹ 60°43’S, 45°38’W	SIRS 1; SIRS 2		Maslen (1979a)*
	Signy Island (type locality) ¹ 60°43’S, 45°38’W	SIRS 1; SIRS 2		Maslen (1981)
	Alexander Island ² 71°0′0″S, 70°0′0″W	Moss, lichen, soil, microbial mat, freshwater		Maslen and Convey (2006)
	Livingston Island ² 62°36′S, 60°30′W			Elshishka et al. (2015a)
Laimaphelenchus helicosoma	Signy Island (type locality) ¹ 60°43’S, 45°38’W	SIRS 1 (type habitat); SIRS 2		Maslen (1979a)*
	Signy Island (type locality) ¹ 60°43’S, 45°38’W	SIRS 1		Maslen (1981)
	Adelaide Island ² 67°15′S, 68°30′W	Moss, lichen		Maslen and Convey (2006)
	Adelaide Island ¹ 67°34.429'S, 68°07.284'W	C. varians and S. uncinata		Newsham et al. (2020)
	Ardley Island ¹ 62°12‘38“S, 58°56‘40“W			Russell et al. (2014)
	King George Island ¹ 62°09‘32“S, 58°27‘58“W 62°11‘48“S, 58°59‘28“W 62°11‘50“S, 58°56‘33“W			Russell et al. (2014)
				Russell et al. (2014)
	Livingston Island, ¹ 62°38'S, 60°20'W	Primitive soil around roots of D. antarctica		Peneva and Chipev (1999)*
Paramphidelus antarcticus	King George Island (type locality) ² 62°2′S, 58°21′W	Lichen (type habitat)		Tsalolikhin (1989)*
Eumonhystera filiformis	King George Island ¹ 62°09’S, 58°29'W	Thaw ponds, with the bottom inhabited by W. sarmentosa		Janiec (1996)
Eumonhystera filiformis	Livingston Island ² 62°36′S, 60°30′W			Elshishka et al. (2015a)
E. vulgaris	King George Island ¹ 62°09’S, 58°29'W	Puddle		Tsalolikhin (1989)*
	King George Island ¹ 62°09’S, 58°29'W	Moraine ponds, their shores are inhabited mainly by S. uncinata, W. sarmentosa and B. pseudotriquetrum; Moss banks of W. sarmentosa and W. laculosa; Thaw ponds, with the bottom inhabited by W. sarmentosa; Nearshore ponds, colonised by W. laculosa and W. sarmentosa		Janiec (1996)
	King George Island ¹62°09‘32“S, 58°27‘58“W; 62°11‘48“S, 58°59‘28“W; 62°11‘50“S, 58°56‘33“W; 62°11‘53“S, 58°56‘47“W			Russell et al. (2014)
	Livingston Island ² 62°36′S, 60°30′W			Elshishka et al. (2015a)
Geomonhystera villosa	Coronation Island ^1,2 60°38'S, 45°35'W			Maslen (1979b)
	Ardley Island ¹ 62°12‘38“S, 58°56‘40“W			Russell et al. (2014)
	Elephant Islan ^1,2 61°10’S, 55°14’W			Maslen (1979b)
	Galindez Island ^1,2 65°15'S, 64°15'W
	Intercurrence Island ^1,2 63°55'S, 61°24'W
	King George Island ¹ 62°09’S, 58°29'W	W. sarmentosa and W. laculosa		Janiec (1996)
	King George Island ¹ 62°11‘48“S, 58°59‘28“W 62°11‘50“S, 58°56‘33“W 62°11‘53“S, 58°56‘47“W			Russell et al. (2014)
	Livingston Island ¹ 62°39‘14“S, 60°36‘39“W			Russell et al. (2014)
	Neko Harbour, Antarctic Peninsula ¹ 64°50‘41“S, 62°31‘53“W
	Signy Island ¹ 60°43’S, 45°38’W			Maslen (1979b)
		SIRS 1		Caldwell (1981)
		SIRS 1; SIRS 2		Maslen (1981)
		Mixture of soil, moss, lichen, liverworts, algae and cyanobacteria	18S rDNA LC457677.1 LC457676.1 LC457675.1 LC457674.1 LC457673.1 LC457672.1 LC457671.1	Kagoshima et al. (2019)
Plectus antarcticus	Danco Land coast, Beneden Head, Antarctic Peninsula (type locality) ² 64°46'S, 62°42'W	Freshwater algae (type habitat)		de Man (1904)*
				Maslen (1979b)
		Moss from rock		Andrássy (1998)*
	Adelaide Island ¹ 67°34′S, 68°07′W	Moss, lichen, soil, microbial mat		Maslen and Convey (2006)
	Adelaide Island ¹ 67°34′S, 68°07′W	Cephaloziella varians (Gottsche)	18S rDNA LC457559.1 LC457558.1 LC457557.1 LC457556.1 LC457555.1 LC457554.1	Kagoshima et al. (2019)**
	Adelaide Island ¹ 67°34.429'S, 68°07.284'W	C. varians and S. uncinata		Newsham et al. (2020)
	Alamode Island ² 68°43'S, 67°32'W			Spaull (1973a)
				Maslen (1979b)
		Moss		Maslen and Convey (2006)
	Alexander Island, ¹ 71°52’40’’S, 68°15’57’’W			Convey and Wynn-Williams (2002)
	Alexander Island ² 71°0′0″S, 70°0′0″W	Moss, lichen, soil, microbial mat		Maslen and Convey (2006)
	Anchorage Island ² 67°36′14.01″S, 68°12′32.78″W	Moss, grass, lichen, soil, microbial mat, freshwater		Maslen and Convey (2006)
	Avian Island ² 67°46"S, 68°54"W			Spaull (1973a)
	Avian Island ² 67°46"S, 68°54"W			Maslen (1979b)
	Blaiklock Island ^1,2 67°33’S, 67°00’W			Maslen (1979b)
	Charcot Island ^1,2 69°45'S, 075°15'W	Soil, moss clumps, algae, various lichens		Convey et al. (2000)
	Charcot Island ^1,2 69°45'S, 075°15'W	Moss, lichen, soil		Maslen and Convey (2006)
	Cone Island ^1,2 67°41'S, 69°10'W			Maslen (1979b)
	Coronation Island ^1,2 60°38'S, 45°35'W			Maslen (1979b)
	Deception Island ² 62°58′37″S, 60°39′0″W	Moss from basalt debris		Andrássy (1998)*
	Deception Island ² 62°58′37″S, 60°39′0″W			Maslen (1979b)
	Deception Island ¹ 62°58‘43“S, 60°33‘24“W	Only erratic patches of mosses, lichens and algae		Russell et al. (2014)
	Devil Island ¹ 63°47‘54“S, 57°17‘24“W	Soil substrates of the very sandy with embedded gravel		Russell et al. (2014)
	Elephant Island ^1,2 61°10’S, 55°14’W			Spaull (1973a)
				Maslen (1979b)
		S. uncinata		Andrássy (1998)*
	Emperor Island ² 67°52'S, 68°43'W			Spaull (1973a)
	Emperor Island ² 67°52'S, 68°43'W			Maslen (1979b)
	Galindez Island ^1,2 65°15'S, 64°15'W
	Guebriant Island ² 67°48′S, 68°25′W
	Intercurrence Island ^1,2 63°55'S, 61°24'W			Spaull (1973a)
	Intercurrence Island ^1,2 63°55'S, 61°24'W			Maslen (1979b)
	Killingbeck Island ² 67°34′S, 68°5′W	Moss, lichen, soil		Maslen and Convey (2006)
	King George Island ² 62°2′S, 58°21′W	Soil around rhizosphere of grasses and under lichen		Tsalolikhin (1989)*
	King George Island ¹ 62°09’S, 58°29'W	Moraine ponds, their shores are inhabited mainly by S. uncinata, W. sarmentosa and B. pseudotriquetrum; Moss banks of W. sarmentosa and W. laculosa		Janiec (1996)
	King George Island ¹62°09‘32“S, 58°27‘58“W; 62°11‘48“S, 58°59‘28“W	Mosses, lichens, D. antarctica		Russell et al. (2014)
	Leonie Island ² 67°36′S, 68°21′W	Moss, grass, lichen, soil, microbial mat, freshwater		Maslen and Convey (2006)
	Limpet Island ^1,2 67°38'S, 68°19'W			Maslen (1979b)
	Livingston Island ² 62°36′S, 60°30′W			Elshishka et al. (2015a)
	Pourqoui pas Island ² 67°41'S, 67°28′W			Maslen (1979b)
	Signy Island ¹ 60°43’S, 45°38’W			Spaull (1973a)
				Spaull (1973b)
				Spaull (1973c)
				Maslen (1979b)
		SIRS 1; SIRS 2		Maslen (1981)
		SIRS1; SIRS2		Caldwell (1981)
		Andreaea sp.		Pickup (1988)
				Wharton and Block (1993)
		Acrocladium sp.; D. antarctica		Andrássy (1998)*
Plectus cf. antarcticus	Livingston Island ² 62°36′S, 60°30′W			Elshishka et al. (2015a)
Plectus cf. antarcticus	Signy Island ² 60°43’S, 45°36’W	Mixture of soil, moss, lichen, liverworts, algae and cyanobacteria	18S rDNA LC457687.1 LC457686.1	Kagoshima et al. (2019)
P. belgicae	Cap Beneden, Danco Land, Antarctic Peninsula (type locality) ² 64°46''S, 62°42"W	Algae fresh water (type habitat)		de Man (1904)*
	Adelaide Island ¹ 67°34′S, 68°07′W	Moss, lichen, soil, microbial mat		Maslen and Convey (2006)
	Adelaide Island ¹ 67°34′S, 68°07′W	C. varians	18S rDNA LC457565.1 LC457564.1 LC457563.1 LC457562.1 LC457561.1 LC457560.1	Kagoshima et al. (2019)
	Adelaide Island ¹ 67°34.429'S, 68°07.284'W	C. varians and S. uncinata		Newsham et al. (2020)
	Anchorage Island ² 67°36′14.01″S, 68°12′32.78″W	Moss, grass, lichen, soil, microbial mat, freshwater		Maslen and Convey (2006)
	Charcot Island ^{1, 2} 69°45'S, 075°15'W	Moss, lichen, soil		Maslen and Convey (2006)
	Elephant Island ^{1, 2} 61°10’S, 55°14’W	P. juniperinum; S. uncinata		Andrássy (1998)*
	King George Island ² 62°2′S, 58°21′W	B. pseudotriquetrum and Bartramia patens	18S rDNA LC457638.1 LC457637.1 LC457636.1	Kagoshima et al. (2019)
	Livingston Island ² 62°36′S, 60°30′W			Elshishka et al. (2015a)
	Rhyolite Island, ² 69°40′S, 68°35′W	Moss, grass		Maslen and Convey (2006)
	Signy Island ² 60°43’S, 45°36’W	Acrocladium sp.; Usnea sp.; SIRS 2		Andrássy (1998)*
Plectus cf. belgicae	Ardley Island ¹ 62°12‘38“S, 58°56‘40“W			Russell et al. (2014)
	Deception Island ¹62°58‘43“S, 60°33‘24“W; 62°58‘42“S, 60°33‘29“W
	King George Island ¹62°09‘32“S, 58°27‘58“W; 62°11‘48“S, 58°59‘28“W; 62°11‘50“S, 58°56‘33“W; 62°11‘53“S, 58°56‘47“W
	Livingston Island ¹ 62°39‘14“S, 60°36‘39“W
	Livingston Island ² 62°36′S, 60°30′W			Elshishka et al. (2015a)
	Petermann Island ¹ 65°10‘29“S, 64°08‘10“W			Russell et al. (2014)
P. insolens	Signy Island (type locality) ² 60°43’S, 45°36’W	Thin soil on rock covered with Acrocladium sp. (type habitat); roots of D. antarctica		Andrássy (1998)*
	Ardley Island ¹ 62°12‘38“S, 58°56‘40“W	Soils, Sanionia sp., W. sarmentosa and Andreaea regularis Müll. Hal.		Russell et al. (2014)
	Livingston Island ² 62°36′S, 60°30′W			Elshishka et al. (2015a)
P. tolerans	Emperor Island (type locality) ² 67°52’S, 68°43’W	S. uncinata (type habitat)		Andrássy (1998)*
	Alexander Island ² 71°0′0″S, 70°0′0″W	Moss, lichen, soil, microbial mat, freshwater		Maslen and Convey (2006)
	Anchorage Island ² 67°36′14.01″S, 68°12′32.78″W	Moss, grass, lichen, soil, microbial mat, freshwater
	Charcot Island ^1,2 69°45'S, 075°15'W	Moss, lichen, soil
	King George Island ² 62°2′S, 58°21′W			Kito (2009)
	Leonie Island ² 67°36′S, 68°21′W	Moss, grass, lichen, soil, microbial mat, freshwater		Maslen and Convey (2006)
	Livingston Island ² 62°36′S, 60°30′W			Elshishka et al. (2015a)
	Rhyolite Island ² 69°40′S, 68°35′W	Moss, grass		Maslen and Convey (2006)
Plectus cf. tolerans	Ardley Island ¹ 62°12‘38“S, 58°56‘40“W			Russell et al. (2014)
	King George Island ¹62°09‘32“S, 58°27‘58“W; 62°11‘48“S, 58°59‘28“W; 62°11‘50“S, 58°56‘33“W; 62°11‘53“S, 58°56‘47“W
	Livingston Island ¹ 62°39‘14“S, 60°36‘39“W
P. meridianus	Terra Firma Island (type locality) ² 68°42′S, 67°32′W	Lichen (type habitat)		Andrássy (1998)*
	Emperor Island ² 67°52’S, 68°43’W	A carpet of S. uncinata		Andrássy (1998)*
	Livingston Island ² 62°36′S, 60°30′W			Elshishka et al. (2015a)
	Signy Island ² 60°43’S, 45°36’W	Roots of D. antarctica		Andrássy (1998)*
Plectus cf. meridianus	Signy Island ² 60°43’S, 45°36’W	Soil, moss, lichen, liverworts, algae and cyanobacteria	18S rDNA LC457691.1 LC457690.1 LC457689.1 LC457688.1	Kagoshima et al. (2019)
P. armatus	Ardley Island ¹ 62°12‘38“S, 58°56‘40“W			Russell et al. (2014)
	Coronation Island ² 60°38'S, 45°35'W			Maslen (1979b)
	Elephant Island ² 61°10’S, 55°14’W
	Galindez Island ² 65°15'S, 64°15'W
	King George Island ¹ 62°11‘48“S, 58°59‘28“W			Russell et al. (2014)
	Livingston Island ² 62°36′S, 60°30′W			Elshishka et al. (2015a)
	Signy Island ¹ 60°43’S, 45°38’W	D. antarctica; C. quitensis; mosses		Spaull (1973b)
				Spaull (1973c)
				Maslen (1979b)
Antarctenchus hooperi	Signy Island (type locality) ^1,2 60°43'S, 45°38'W	A. gainii (type habitat); Brachythecium sp., Calliergon sp., S. filaris, Grimmia antarctici Card., Ch. aciphyllum, P. juniperinum and D. antarctica		Spaull (1972)*
		Sanionia sp.+ Calliergon sp.+ Calliergidium sp.; Polytrichum sp.; Bryum sp. + Syntrichia sp. + Andreaea sp.; D. antarctica		Spaull (1973a)
		A. gainii, S. filaris, Calliergon-Calliergidium		Spaull (1973b)
				Spaull (1973c)
				Maslen (1979b)
		SIRS 1; SIRS 2		Maslen (1981)
		S. uncinata		Caldwell (1981)
				Wharton and Block (1993)
	Coronation Island ^1,2 60°38'S, 45°35'W	D. antarctica		Spaull (1972)*
		D. antarctica		Spaull (1973a)
				Maslen (1979b)
Ditylenchus parcevivens	Signy Island (type locality) ² 60°43’S, 45°38’W	Fine silt (type habitat)		Andrássy (1998)*
	King George Island ¹62°09‘32“S, 58°27‘58“W; 62°11‘48“S, 58°59‘28“W; 62°11‘50“S, 58°56‘33“W; 62°11‘53“S, 58°56‘47“W			Russell et al. (2014)
	Livingston Island ² 62°36′S, 60°30′W			Elshishka et al. (2015a)
Teratocephalus tilbrooki	Signy Island (type locality) ^1,2 60°43’S, 45°38’W	SIRS 1 (type habitat); SIRS2		Maslen (1979a)*
		‘Swamp’ moss carpets		Maslen (1979b)
		SIRS 1; SIRS 2		Maslen (1981)
		Andreaea sp.		Pickup (1988)
				Wharton and Block (1993)
		Usnea sp.		Andrássy (1998)*
	Adelaide Island ² 67°15′S, 68°30′W	Moss, lichen		Maslen and Convey (2006)
	Ardley Island ¹ 62°12‘38“S, 58°56‘40“W			Russell et al. (2014)
	Charcot Island ^{1, 2} 69°45'S, 075°15'W	Moss, lichen, soil		Maslen and Convey (2006)
	Halfmoon Island ¹ 62°35‘45“S, 59°54‘06“W	Soil		Russell et al. (2014)
	King George Island ¹62°09‘32“S, 58°27‘58“W; 62°11‘48“S, 58°59‘28“W; 62°11‘50“S, 58°56‘33“W; 62°11‘53“S, 58°56‘47“W	Soil		Russell et al. (2014)
	Leonie Island ² 67°36′S, 68°21′W	Moss, grass, lichen, soil, microbial mat, freshwater		Maslen and Convey (2006)
T. pseudolirellus	Signy Island (type locality) ¹ 60°43’S, 45°38’W	S. filaris (type habitat)		Maslen (1979a)*
	Alexander Island ² 71°0′0″S, 70°0′0″W	Moss, lichen, soil, microbial mat, freshwater		Maslen and Convey (2006)
	Charcot Island ²69°45'S, 075°15'W	Moss, lichen, soil		Maslen and Convey (2006)
	King George Island ² 62°2′S, 58°21′W			Kito (2009)
	Livingston Island ² 62°36′S, 60°30′W			Elshishka et al. (2015a)
T. rugosus	Signy Island (type locality) ² 60°43’S, 45°38’W	SIRS 1; SIRS 2		Maslen (1979a)*
				Maslen (1979b)
		SIRS 1; SIRS 2		Maslen (1981)
	Ardley Island ¹ 62°12‘38“S, 58°56‘40“W			Russell et al. (2014)
	Deception Island ¹ 62°58‘42“S, 60°33‘29“W
	Devil Island ¹ 63°47‘54“S, 57°17‘24“W
	Halfmoon Island ¹ 62°35‘45“S, 59°54‘06“W
	King George Island ¹62°09‘32“S, 58°27‘58“W; 62°11‘48“S, 58°59‘28“W; 62°11‘53“S, 58°56‘47“W
	Livingston Island ² 62°36′S, 60°30′W			Elshishka et al. (2015a)
Acrobeloides arctowskii	King George Island (type locality) ¹ 58°29'30''W, 61°05'S	Soil around roots of D. antarctica (type habitat)		Holovachov and Bostrom (2006)*
	King George Island ¹ 62°09‘32“S, 58°27‘58“W			Russell et al. (2014)
	Deception Island ¹62°58‘43“S, 60°33‘24“W; 62°58‘42“S, 60°33‘29“W	Soil devoid of vegetation or with P. crispa		Russell et al. (2014)
Cervidellus cf. vexilliger	King George Island ¹ 62°09‘32“S, 58°27‘58“W			Russell et al. (2014)
Cuticularia firmata	Signy Island (type locality) ² 60°43’S, 45°36’W	Fine mud (type habitat); SIRS 2		Andrássy (1998)*
Rhabditis krylovi	King George Island (type locality) ² 62°2′S, 58°21′W	Flowing lake (type habitat)		Tsalolikhin (1989)*
Rhabditis marina-group	Deception Island ¹ 62°55‘43“S, 60°40‘48“W			Russell et al. (2014)
Pelodera teres group	Deception Island ¹62°58‘43“S, 60°33‘24“W; 62°58‘42“S, 60°33‘29“W			Russell et al. (2014)
	Livingston Island ¹ 62°39‘14“S, 60°36‘39“W			Russell et al. (2014)
	Livingston Island ² 62°36′S, 60°30′W			Elshishka et al. (2015a)
	Neko Harbour, Antarctic Peninsula ¹ 64°50‘41“S, 62°31‘53“W			Russell et al. (2014)
	Paulet Island ¹ 63°34‘30“S, 55°46‘59“W	Ornithogenic soils		Russell et al. (2014)
Pelodera strongyloides group	Devil Island ¹ 63°47‘54“S, 57°17‘24“W			Russell et al. (2014)
	Livingston Island ² 62°36′S, 60°30′W			Elshishka et al. (2015a)
	Livingston Island ¹ 62°39‘14“S, 60°36‘39“W			Russell et al. (2014)
	Neko Harbour, Antarctic Peninsula ¹64°51‘45“S, 62°26‘47“W; 64°50‘41“S, 62°31‘53“W			Russell et al. (2014)
Pelodera parateres group	Deception Island ¹ 62°58‘42“S, 60°33‘29“W			Russell et al. (2014)
Pelodera parateres group	King George Island ¹ 62°09‘32“S, 58°27‘58“W			Russell et al. (2014)
Coomansus gerlachei	Danco Land coast, Beneden Head Antarctic Peninsula (type locality) ² 64°46''S, 62°42"W	Algae fresh water (type habitat)		de Man (1904)*
				Maslen (1979b)
				Andrássy (1998)*
	Caleta Cierva, Antarctic Peninsula ¹ 64°10’S, 60°57’W	Soil around roots of D. antarctica		Chaves (1990)*
	Antarctic Peninsula			Jiménez Guirado et al. (1998)*
	Adelaide Island ¹ 67°34.429'S, 68°07.284'W	C. varians and S. uncinata		Newsham et al. (2020)
	Anchorage Island ² 67°36′14.01″S, 68°12′32.78″W	Moss, grass, lichen, soil, microbial mat, freshwater		Maslen and Convey (2006)
	Anvers Island, Biscoe Point ² 64°49′6.85″S, 63°46′32.29″W	Soil around roots of D. antarctica		Shishida and Ohyama (1989)*
	Anvers Island, Old Palmer ² 64°45′48″S, 64°5′12″W	Moss mats		Shishida and Ohyama (1989)*
	Avian Island ² 67°46''S, 68°54"W	Sanionia sp., Bryum sp.		Spaull (1973a)
				Maslen (1979b)
		S. uncinata, B. pseudotriquetrum		Spaull (1981)
	Coronation Island ^1,2 60°38'S, 45°35'W	D. antarctica		Spaull (1973a)
	Coronation Island ^1,2 60°38'S, 45°35'W			Maslen (1979b)
	Charcot Island ^1,2 69°45'S, 75°15'W	Soil, moss clumps, algae, various lichens		Convey et al. (2000)
	Deception Island ² 62°58′37″S, 60°39′0″W	Sanionia sp.; Polytrichum sp.		Spaull (1973a)
				Maslen (1979b)
		Melting snow moisten mosses in a shingle field		Andrássy (1998)*
	Dream Island ² 64°44′0″S, 64°14′0″W	Moss mats with green algae		Shishida and Ohyama (1989)*
	Elephant Island ^1,2 61°10’S, 55°14’W	Brachythecium sp.; D. antarctica; Sanionia sp.		Spaull (1973a)
				Maslen (1979b)
		Soil bellow D. antarctica		Spaull (1981)
	Galindez Island ^1,2 65°15'S, 64°15'W	Brachythecium sp.; D. antarctica; Bryum sp.; Sanionia sp. + Pohlia sp.		Spaull (1973a)
				Maslen (1979b)
		Brachythecium austrosalebrosum (C. Muell.) Par.		Spaull (1981)
	Guebriant Island ² 67°48′S, 68°25′W	Brachythecium sp., Bryum sp., Sanionia sp.		Spaull (1973a)
	Guebriant Island ² 67°48′S, 68°25′W			Maslen (1979b)
	Intercurrence Island ^1,2 63°55'S, 61°24'W	Brachythecium sp., Bryum sp., Sanionia sp.		Spaull (1973a)
	Intercurrence Island ^1,2 63°55'S, 61°24'W			Maslen (1979b)
	Halfmoon Island ¹ 62°35‘45“S, 59°54‘06“W			Russell et al. (2014)
	King George Island ¹ 62°09’S, 58°29'W	Moraine ponds, their shores are inhabited mainly by S. uncinata, W. sarmentosa and B. pseudotriquetrum		Janiec (1996)
	Leonie Island ² 67°36′S, 68°21′W	Moss, grass, lichen, soil, microbial mat, freshwater		Maslen and Convey (2006)
	Leonie Island ² 67°36′S, 68°21′W	Mixture of soil, moss, lichen, liverworts, algae and cyanobacteria	18S rDNA LC457644.1 LC457643.1 LC457642.1 LC457641.1 LC457640.1 LC457639.1	Kagoshima et al. (2019)**
	Limpet Island ^1,2 67°38'S, 68°19'W	Brachythecium sp., Bryum sp., Sanionia sp.		Spaull (1973a)
	Limpet Island ^1,2 67°38'S, 68°19'W			Maslen (1979b)
	King George Island ² 62°2′S, 58°21′W			Kito (2009)
	King George Island ¹62°09‘32“S, 58°27‘58“W; 62°11‘48“S, 58°59‘28“W; 62°11‘50“S, 58°56‘33“W; 62°11‘53“S, 58°56‘47“W			Russell et al. (2014)
	Litchfield Island ² 64°46′S, 64°6′W	Decaying moss mats with blue-green algae		Shishida and Ohyama (1989)*
	Livingston Island ² 62°36′S, 60°30′W	Soil under crisp of green algae; D. antarctica-S. uncinata; D. antarctica, P. alpinum		Peneva et al. (1996)*
	Livingston Island ¹ 62°39‘14“S, 60°36‘39“W			Russell et al. (2014)
	Livingston Island ² 62°36′S, 60°30′W			Elshishka et al. (2015a)
	Nelson Island ² 62°18′S, 59°3W	Moss	18S rDNA KM092523.1 28S rDNA KM092524.1	Elshishka et al. (2015b)**
	Signy Island ^1,2 60°43’S, 45°38’W	Sanionia sp.+ Calliergon sp.+ Calliergidium sp.; Polytrichum sp.; Bryum sp. + Syntrichia sp. +Andreaea sp.; D. antarctica		Spaull (1973a)
				Spaull (1973b)
				Spaull (1973c)
				Maslen (1979b)
		S. uncinata and W. sarmentosa		Caldwell (1981)
		SIRS 1; SIRS 2		Maslen (1981)
		P. crispa from melt stream		Spaull (1981)
		Sanionia sp.		Pickup (1988)
		P. crispa; S. uncinata		Pickup (1990)
		Calliergon sp.		Wharton and Block (1993)
		Mixture of soil, lichen, liverworts, algae and cyanobacteria	18S rDNA LC457661.1 LC457660.1 LC457659.1 LC457658.1 LC457657.1 LC457656.1 LC457655.1	Kagoshima et al. (2019)**

Figure 1.

Terrestrial nematodes from the Maritime Antarctic - visual representation of the data matrix (shade plot): in the columns are the 37 sites and in the rows – 44 species. White and black spaces denote absence or presence of a particular species at a given site; sites and species are arranged according to the groups derived by the clustering analyses. Significant clusters were identified with SIMPROF test and visualised in red dashed lines and a range of coloured dots. Each colour represents a group of sites/islands with similar nematode fauna.

Figure 2.

Distribution of terrestrial nematodes in the Maritime Antarctic. In green are presented the sites with records of terrestrial nematodes.

The order Dorylaimida is the best represented order in this Antarctic Region with five families, six genera and 13 species. The order Mononchida is represented by only one family (one genus and species).

The families Aphelenchoididae, Cephalobidae, Monhysteridae, Plectidae, Qudsianematidae, Peloderidae and Rhabditidae have a cosmopolitan distribution and, in the Maritime Antarctic, they are represented by one to two genera and two to ten species. The family Plectidae is the most diverse (10 species). Seven families (Amphidelidae, Anguinidae, Aporcelaimidae, Mononchidae, Nordiidae, Pararhyssocolpidae and Psilenchidae) are represented by only one species each.

Almost all species and four genera (Antarctenchus, Pararhyssocolpus, Amblydorylaimus and Enchodeloides) are endemic. Four species generally known as cosmopolitan are reported in some ecological studies in the Maritime Antarctic: Eumonhystera vulgaris (de Man 1880) Andrássy (1981), E. filiformis (Bastian 1865) Andrássy (1981), Geomonhystera villosa (Bütschli 1873) Andrássy (1981) and Plectus armatus Bütschli 1873. Of these, a description and illustrations were provided only for E. vulgaris (Tsalolikhin 1989).

Most species (27) have limited distribution registered in up to five islands of the Maritime Antarctic. Cuticularia firmata Andrássy 1998, Cervidellus cf. vexilliger, Rhabditis krylovi Tsalolikhin 1989, a species of the Rhabditis marina-group, Mesodorylaimus masleni Nedelchev and Peneva 2000, Eudorylaimus cf. carteri and Plectus cf. meridianus are recorded from one island only. Six species occurred in more than 30% of the sites (C. gerlachei, P. antarcticus, Pararhyssocolpus paradoxus (Loof 1975), Eudorylaimus spaulli Loof 1975, E. coniceps Loof 1975, Enchodeloides signyensis (Loof 1975)) with C. gerlachei and P. antarcticus being the most widespread (reported from more than half of the sites) (Figs 3, 4, 5). There are no particular trends in the distribution of most common species (occurring in more than 22% of the sites, 1/4 of the species) related to longitude or latitude, only P. paradoxus and Mesodorylaimus imperator Loof 1975 have not been reported from the most southern sites, whereas G. villosa – from the most northern localities.

Figure 3.

Described species and their occurrences presented as percentages.

Figure 4.

Distribution of P. antarcticus, C. gerlachei and Pararhyssocolpus paradoxus in the Maritime Antarctic. In red are presented the sites with records of these species, in green are presented the sites with records of the other Antarctic terrestrial nematodes.

Figure 5.

Distribution of Eudorylaimus spaulli, E. coniceps and Enchodeloides signyensis in the Maritime Antarctic. In red are presented the sites with records of these species, in green are presented the sites with records of the other Antarctic terrestrial nematodes.

In most of the literature sources, there are data on the microhabitats in which nematode species occurred. The nematodes have been recorded from various microhabitats: bare soil, microbial mats, moss, lichens and algae and soil around the two species of higher plants occurring in the Maritime Antarctic (Fig. 6).

Figure 6.

Some microhabitats in the Maritime Antarctic. A Colobanthus quitensis B Deschampsia antarctica C Bare soil D Syntrichia sp. E Bryum sp. F D. antarctica, C. quitensis, mosses G Sanionia sp. H Polytrichum sp. J Usnea sp. Photographs by M. Elshishka (Livingston Island).

DNA data have been generated for 11 species, but sequences for only three of them (Amblydorylaimus isokaryon (Loof 1975), P. paradoxus and E. signyensis) are supported by full morphological descriptions as per the modern taxonomic standards (Elshishka et al. 2015b, Elshishka et al. 2017, Kagoshima et al. 2019).

The review of the literature related to terrestrial nematodes from the Maritime Antarctic showed that the different parts are unevenly studied and three islands, Livingston (31 species), King George (28 species) and Signy (25 species) exhibited the richest nematode fauna (Fig. 7). Signy Island is the best studied Antarctic island with 12 new species described. This is due to the intensive studies on the nematode fauna in the 1970s and 1980s undertaken by the British Antarctic Survey (Spaull 1973a, Spaull 1973b, Spaull 1973c, Loof 1975, Maslen 1979a, Maslen 1979b, Caldwell 1981, Maslen 1981, Pickup 1988, Pickup 1990 etc.).

Figure 7.

Bar chart visualising the described species (left axis) and literature sources (right axis) per each island/site.

Discussion

Our knowledge of the nematode species diversity in the Maritime Antarctic is still insufficient and fragmented. The different study efforts at the various sites do not allow gaining a clear picture of trends in the diversity and distribution of nematode species in the target Antarctic Region. Yet, the analysis provided on the basis of species presence/absence data revealed several groups of sites with similar nematode fauna forming a latitudinal gradient (Fig. 1). The high level of endemism at both the species and genus level is a characteristic feature of the nematode fauna of the region as was mentioned above. This high degree of endemism can be explained by the long-term isolation and the harsh conditions of the region (Convey et al. 2008, Nielsen et al. 2011a). It has been suggested that the Antarctic terrestrial fauna might have survived glaciation in ice-free areas and some species might be remnants of the fauna of the Gondwana super-continent (Andrássy 1998, Maslen and Convey 2006, Chown and Convey 2016, Convey et al. 2020).

The physical isolation and harsh environment of Antarctic terrestrial ecosystems is the major reason for the difficult colonisation by non-native biota (Convey and Peck 2019). In recent decades, human visits and activities in the Antarctic have provided ways (e.g. cargo, vehicles, scientific equipment, fresh food, clothing, people) to overcome these barriers (Lee and Chown 2009, Hughes et al. 2010, Chwedorzewska et al. 2013, Adams et al. 2014). So far, the probability that introduced invertebrates will become established and spread is considered to be quite low; most of them are not able to complete the life cycle and establish a stable population outside the station (Chwedorzewska et al. 2013). Although these organisms cannot survive outside at present, they are potential colonisers, which could be established in the future following the climate warming (Convey and Peck 2019). Тhe four cosmopolitan nematode taxa (E. vulgaris, E. filiformis, G. villosa and P. armatus) also reported from the Maritime Antarctic are considered to be of non-native origin by Andrássy (1998). Due to the absence or scarcity of data on the morphology of these species, at present, their origin cannot be confirmed. Future studies using an integrated taxonomic approach (i.e. simultaneous molecular and morphological characterisation) of materials obtained from pristine areas may help clarify their status. The gap in knowledge of nematode diversity, both in terms of taxonomy and distribution, is essential when assessing the introduction of non-native species. Nematode species richness in the Maritime Antarctic, which is underestimated (Nielsen et al. 2011b) may be compromised with increasing human impact in Antarctica.

The risk to Antarctic biodiversity is not limited to the transfer of alien species originating from other regions of Earth, but also concerns the transfer of native or endemic species from one part of Antarctica to another where they are not part of the indigenous biota (Convey 2008, Hughes et al. 2019, Hughes et al. 2020). This risk is greater because such species are likely to adapt well to the new location, unlike most non-native species that have been transferred to Antarctica from elsewhere (Convey 2015). The transfer of species across natural biogeographic boundaries can affect endemism in these areas. Antarctica is one of the few regions on the Planet where such boundaries still exist (Convey 2008). The nematode faunas of the Maritime and the Continental Antarctic are characterised by their uniqueness, as no overlap at the species level of the two local faunas exists (Andrássy 1998, Maslen and Convey 2006, Convey et al. 2020). This is indicative of an ancient geographical divide between these areas (Andrássy and Gibson 2007) and led Chown and Convey (2006) to define the Gressitt Line, which is located across the base of the Antarctic Peninsula.

So far, there is no evidence for the transfer and establishment of nematode species from the Continental to the Maritime Antarctic. Some nematological reports have included data on the presence of species that are emblematic of the Continental Antarctic (Plectus murrayi Yeates 1970 and P. frigophilus Kirjanova 1958) in the Maritime part, without morphological data (see Velasco-Castrillón et al. (2014a)). In our study, these records are not included as they are most likely due to misidentification.

Regarding the biotope/microhabitat distribution of the species, the incomplete and insufficient data do not allow a definite conclusion, taking into account also the lack of research in the more inaccessible areas of the Antarctic Peninsula and the islands. Most likely the micro biotope distribution pattern is similar to that shown in the study of the nematode fauna of Cape Chelyuskin in the Arctic (Chernov et al. 1979), where species show very low biotopic associations and most of them inhabit all possible microhabitats (i.e. the majority of species are polytopic); this is also a characteristic feature of other groups of organisms in the polar regions (Chernov et al. 1979).

The major life strategy of organisms living in extreme environments is the development of tolerance and plasticity and not lack of competition and specialisation, which is typical of other biomes (Convey 1996, Chernov et al. 2011).

Comparing the two parts of the Antarctic shows that the nematode studies in the Maritime Antarctic are less represented, whereas investigations in the Continental Antarctic have been more intensive. However, the latter are primarily related to ecology (Adams et al. 2014, Velasco-Castrillón et al. 2014a, Velasco-Castrillón et al. 2018) and have identified to date 34 species of soil nematodes (Velasco-Castrillón et al. 2014a). The smaller number of species in the Continental Antarctic is associated with the harsher and more unfavourable environmental conditions. This zone includes ecosystems with the simplest terrestrial fauna on the Planet, where even nematodes are absent (Convey and McInnes 2005, Convey 2017).

The two opposite polar regions of the Earth are unevenly studied with respect to soil nematodes (Peneva et al. 2009, Holovachov 2014a). Despite the fewer taxonomic studies of terrestrial nematodes in the Arctic, 391 species have been recorded there (Holovachov 2014a). Key geographical and ecological features of both regions, such as geological history, climate, landscape, dispersal barriers and vegetation are responsible for the lower nematode diversity in the Antarctic than in the Arctic (Nielsen and Wall 2013).

Studies that include molecular data for the nematodes in the Maritime Antarctic are too rare to provide valuable information regarding nematode diversity, phylogenetics and endemism (Elshishka et al. 2015b, Elshishka et al. 2017, Kagoshima et al. 2019). The taxonomic position of only three Antarctic dorylaimid species, A. isokaryon, P. paradoxus and E. signyensis, was reconsidered on the basis of morphological and molecular characteristics of 18S rDNA (SSU rDNA) and the D2-D3 expansion fragments of 28S rDNA (LSU rDNA) (Elshishka et al. 2015b, Elshishka et al. 2017) and two new endemic genera were proposed (Pararhyssocolpus and Enchodeloides).

To advance the understanding of phylogeny and phylogeography of Antarctic nematodes, studies are required of other genes with higher evolutionary rates than 18S rDNA, such as 28S rDNA, the internal transcribed spacer (ITS in the ribosomal RNA locus) or the mitochondrial cytochrome c oxidase subunit I (COI). These genes should be included in future taxonomic analyses of Antarctic nematodes (Kagoshima et al. 2019).

The application of integrated taxonomy and DNA barcoding will substantially assist in nematode diversity studies, phylogenetics and especially the recognition of cryptic species. Further, comprehensive molecular studies will provide valuable information on the patterns of species distribution and for gaining additional knowledge on evolutionary processes and biogeography of Antarctic nematodes.

The scant studies of polar regions, in particular of the Maritime Antarctic, demand more intensive sampling and research, especially in the territories that have so far remained unexplored, in order to give a clearer and more adequate view of species diversity and trends in their microhabitat and geographical distribution. Therefore, further efforts aiming at targeted and systematic integrative studies are needed.

Acknowledgements

This study was funded by the Programme for career development of young scientists, Bulgarian Academy of Sciences, the project №80-10-214, National Centre for Polar Studies, Sofia University "St. Kliment Ohridski” and ANIDIV4, Bulgarian Academy of Sciences. The authors are thankful to Prof. Aneta Kostadinova from the Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences, for the critical reading of the manuscript and helpful suggestions.

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Supplementary material

Endnotes