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Refuges of Antarctic diversity
Abstract
Antarctic terrestrial ecosystems contribute a tiny proportion of the area of the continent and host an impoverished and often cryptic biota. In recent years it has been realized that much of this biota is unique to the continent, carrying signals of its evolutionary radiation on multi-million-year timescales, some even pre-dating the final breakup of Gondwana and the geographic isolation of Antarctica. However, for terrestrial life to have existed continuously on the continent over these timescales, appropriate ice-free land must have existed through the multiple glacial cycles that took place throughout the Miocene, Pliocene and Pleistocene eras. This challenges current glaciological reconstructions, which present a model of complete obliteration of most currently ice-free areas of ground at successive glacial maxima, with those remaining not providing viable refugia for the majority of the contemporary terrestrial biota. In this chapter, we consider the requirement for refugia across all regions of Antarctica, and the likely form that such refugia may have taken.
... Antarctic terrestrial arthropods have persisted for millions of years in microhabitats that are ice-free yet have some liquid water available [1][2][3]. The extent of these microhabitats, and how they are distributed across the landscape, is largely determined by the underlying geography and millennia-scale ice sheet dynamics [4], although across much of Antarctica the precise locations of refugia have not been identified. Even during periods of extensive ice cover, such as during the Last Glacial Maximum (LGM), in some regions, species likely survived either on protruding nunataks [1] or in association with geothermal features [5], although such features do not appear to explain the persistence of most terrestrial arthropod diversity, which is limited to lower-altitude coastal areas [1]. ...
... The extent of these microhabitats, and how they are distributed across the landscape, is largely determined by the underlying geography and millennia-scale ice sheet dynamics [4], although across much of Antarctica the precise locations of refugia have not been identified. Even during periods of extensive ice cover, such as during the Last Glacial Maximum (LGM), in some regions, species likely survived either on protruding nunataks [1] or in association with geothermal features [5], although such features do not appear to explain the persistence of most terrestrial arthropod diversity, which is limited to lower-altitude coastal areas [1]. Long-term isolation of arthropod populations across the landscape, with resulting genetic bottlenecks, can ultimately lead to speciation through divergence via genetic drift or mutation [6]. ...
... The extent of these microhabitats, and how they are distributed across the landscape, is largely determined by the underlying geography and millennia-scale ice sheet dynamics [4], although across much of Antarctica the precise locations of refugia have not been identified. Even during periods of extensive ice cover, such as during the Last Glacial Maximum (LGM), in some regions, species likely survived either on protruding nunataks [1] or in association with geothermal features [5], although such features do not appear to explain the persistence of most terrestrial arthropod diversity, which is limited to lower-altitude coastal areas [1]. Long-term isolation of arthropod populations across the landscape, with resulting genetic bottlenecks, can ultimately lead to speciation through divergence via genetic drift or mutation [6]. ...
Free-living terrestrial mites (Acari) have persisted through numerous glacial cycles in Antarctica. Very little is known, however, of their genetic diversity and distribution, particularly within the Ross Sea region. To redress this gap, we sampled mites throughout the Ross Sea region, East Antarctica, including Victoria Land and the Queen Maud Mountains (QMM), covering a latitudinal range of 72–85 °S, as well as Lauft Island near Mt. Siple (73 °S) in West Antarctica and Macquarie Island (54oS) in the sub-Antarctic. We assessed genetic diversity using mitochondrial cytochrome c oxidase subunit I gene sequences (COI-5P DNA barcode region), and also morphologically identified voucher specimens. We obtained 130 sequences representing four genera: Nanorchestes (n = 30 sequences), Stereotydeus (n = 46), Coccorhagidia (n = 18) and Eupodes (n = 36). Tree-based analyses (maximum likelihood) revealed 13 genetic clusters, representing as many as 23 putative species indicated by barcode index numbers (BINs) from the Barcode of Life Datasystems (BOLD) database. We found evidence for geographically-isolated cryptic species, e.g., within Stereotydeus belli and S. punctatus, as well as unique genetic groups occurring in sympatry (e.g., Nanorchestes spp. in QMM). Collectively, these data confirm high genetic divergence as a consequence of geographic isolation over evolutionary timescales. From a conservation perspective, additional targeted sampling of understudied areas in the Ross Sea region should be prioritised, as further diversity is likely to be found in these short-range endemic mites.
... Antarctic terrestrial arthropods have persisted for millions of years in microhabitats that are ice-free yet have some liquid water available [1][2][3]. The extent of these microhabitats, and how they are distributed across the landscape, is largely determined by the underlying geography and millennia-scale ice sheet dynamics [4], although across much of Antarctica the precise locations of refugia have not been identified. Even during periods of extensive ice cover, such as during the Last Glacial Maximum (LGM), in some regions, species likely survived either on protruding nunataks [1] or in association with geothermal features [5], although such features do not appear to explain the persistence of most terrestrial arthropod diversity, which is limited to lower-altitude coastal areas [1]. ...
... The extent of these microhabitats, and how they are distributed across the landscape, is largely determined by the underlying geography and millennia-scale ice sheet dynamics [4], although across much of Antarctica the precise locations of refugia have not been identified. Even during periods of extensive ice cover, such as during the Last Glacial Maximum (LGM), in some regions, species likely survived either on protruding nunataks [1] or in association with geothermal features [5], although such features do not appear to explain the persistence of most terrestrial arthropod diversity, which is limited to lower-altitude coastal areas [1]. Long-term isolation of arthropod populations across the landscape, with resulting genetic bottlenecks, can ultimately lead to speciation through divergence via genetic drift or mutation [6]. ...
... The extent of these microhabitats, and how they are distributed across the landscape, is largely determined by the underlying geography and millennia-scale ice sheet dynamics [4], although across much of Antarctica the precise locations of refugia have not been identified. Even during periods of extensive ice cover, such as during the Last Glacial Maximum (LGM), in some regions, species likely survived either on protruding nunataks [1] or in association with geothermal features [5], although such features do not appear to explain the persistence of most terrestrial arthropod diversity, which is limited to lower-altitude coastal areas [1]. Long-term isolation of arthropod populations across the landscape, with resulting genetic bottlenecks, can ultimately lead to speciation through divergence via genetic drift or mutation [6]. ...
Free-living terrestrial mites (Acari) have persisted through numerous glacial cycles in Antarctica. Very little is known, however, of their genetic diversity and distribution, particularly within the Ross Sea region. To redress this gap, we sampled for mites throughout the Ross Sea region, East Antarctica, including Victoria Land and the Queen Maud Mountains (QMM), covering a latitudinal range of 72-85oS, as well as from Lauft Island near Mt Siple (73oS) in West Antarctica and Macquarie Island (54oS) in the sub-Antarctic. We assessed genetic diversity using mitochondrial cytochrome c oxidase subunit I gene sequences (COI-5P DNA barcode region), and also morphologically identified voucher specimens. We obtained 130 sequences representing four genera: Nanorchestes (n = 30 sequences), Stereotydeus (n = 46), Coccorhagidia (n = 18) and Eupodes (n = 36). Tree-based analyses (maximum likelihood) revealed 13 genetic clusters, representing as many as 23 putative species indicated by Barcode Index Numbers (BINs) from the Barcode of Life Datasystems (BOLD) database. We found evidence for geographically-isolated cryptic species, e.g. within Stereotydeus belli and S. punctatus, as well as unique genetic groups occurring in sympatry (e.g. Nanorchestes spp. in QMM). Collectively, these data confirm high genetic divergence as a consequence of geographic isolation over evolutionary timescales. From a conservation perspective, additional targeted sampling of understudied areas in the Ross Sea region should be prioritised, as further diversity is likely to be found for these short-range endemic mites.
... The prokaryotic diversity in these remote valleys is largely endemic as there is no evidence of biological movement from other continents or sub-Antarctic Islands currently [11] and through the Cenozoic era [12][13][14][15]. Through cycles of glacial expansion, refugia sites within the MDV that remained undisturbed and habitable, were necessary for endemic organisms' survival and eventual repopulation of glacially inundated or flooded valleys. ...
... For most Antarctic regions, including the MDV, refugia sites have been an object of study to determine climax communities, phylogeographic patterns and repopulation rates. The consensus is that biota has persisted in these environments throughout the Pleistocene and earlier cycles of glacial activity [13,[43][44][45][46][47][48][49]. Identifying those refugia in the MDV with consistent habitation throughout the LGM requires several considerations. ...
... However, no precise consensus about which candidate sites represent actual refugia in the MDV exists in the current literature due to an incomplete exposure dating record and limited biological census identifying high elevation habitats. It is likely that refugia existed throughout the MDV as temporarily overlapping habitable soils throughout recurrent glacial cycles of the Pleistocene [13]. Two sample sites were chosen per valley system to incorporate varying geological histories, although not every valley system could be represented by both a putative refugia and disturbed site. ...
In the cold deserts of the McMurdo Dry Valleys (MDV) the suitability of soil for microbial life is determined by both contemporary processes and legacy effects. Climatic changes and accompanying glacial activity have caused local extinctions and lasting geochemical changes to parts of these soil ecosystems over several million years, while areas of refugia may have escaped these disturbances and existed under relatively stable conditions. This study describes the impact of historical glacial and lacustrine disturbance events on microbial communities across the MDV to investigate how this divergent disturbance history influenced the structuring of microbial communities across this otherwise very stable ecosystem. Soil bacterial communities from 17 sites representing either putative refugia or sites disturbed during the Last Glacial Maximum (LGM) (22–17 kya) were characterized using 16 S metabarcoding. Regardless of geographic distance, several putative refugia sites at elevations above 600 m displayed highly similar microbial communities. At a regional scale, community composition was found to be influenced by elevation and geographic proximity more so than soil geochemical properties. These results suggest that despite the extreme conditions, diverse microbial communities exist in these putative refugia that have presumably remained undisturbed at least through the LGM. We suggest that similarities in microbial communities can be interpreted as evidence for historical climate legacies on an ecosystem-wide scale.
... The prokaryotic diversity in these remove valleys is largely endemic as there is no evidence of biological movement from other continents or sub-Antarctic Islands currently (Archer et al. 2019) and through the Cenozoic era (Convey et al., 2009(Convey et al., , 2020McGaughran et al., 2011McGaughran et al., , 2019. Through cycles of glacial expansion, refugia sites within the MDV that remained undisturbed and habitable, were necessary for endemic organisms' survival and eventual repopulation of glacially inundated or flooded valleys. ...
... For most Antarctic regions, including the MDV, refugia sites have been an object of study to determine climax communities, phylogeographic patterns and repopulation rates (Marshall and Coetzee, 2000;De Wever et al., 2009;Bennett et al., 2016;Soler-Membrives et al., 2017;Biersma et al., 2018;Convey et al., 2020). Identifying MDV refugia requires several considerations. ...
... The MDV provide a unique ecosystem to study phylogeographic patterns left by geological cycles and millions of years of evolution in an environment that has undergone remarkably little change (Sugden, Bentley and Cofaigh, 2006). At the same time, it is well documented that populations of Antarctic biota have been strongly influenced by events in their geological and climate history and carry evolutionary traces of extinction during glacial advance or persistence in non-glaciated refugia (Rogers, 2007;Convey et al., 2009Convey et al., , 2020. In this study the microbial composition of several high elevation putative refugia and more recently disturbed low elevation sites were characterized to determine signatures of divergent glacial legacies on microbial communities. ...
In the cold deserts of the McMurdo Dry Valleys (MDV) the suitability of soil for microbial life is determined by both contemporary processes and legacy effects. Climatic changes and accompanying glacial activity have caused local extinctions and geochemical changes to soil ecosystems over several million years, while high elevation refugia may have escaped these disturbances and existed under relatively stable conditions. This study describes the impact of historical glacial and lacustrine disturbance events on microbial communities across the MDV. Soil bacterial communities from 17 sites representing either putative refugia or sites disturbed during the Last Glacial Maximum (LGM) (22-17kya) were characterized using 16S metabarcoding. Regardless of geographic distance, several putative refugia sites at elevations above 600 meter displayed highly similar microbial communities. At a regional scale, community composition was found to be influenced by elevation and geographic proximity more so than soil geochemical properties. These results suggest that despite the extreme conditions, diverse microbial communities exist in these putative refugia that have presumably remained undisturbed at least through the last glacial maximum. We suggest that similarities in microbial communities can be interpreted as evidence for historical climate legacies on an ecosystem-wide scale.
... In contrast, Antarctica's paleoclimatic legacy for terrestrial communities has long been considered one of widespread extinction due to glaciation. Evidence of terrestrial species surviving in Antarctic glacial refugia (6) and discoveries of substantial endemic diversity and biogeographic structuring in some groups (7,8) is changing this narrative, indicating extended evolutionary histories on land. Yet, such evolutionary histories remain obscured by a lack of large-scale molecular phylogenetic work, with most Antarctic terrestrial research focused on small subsets of species or populations (9,10). ...
... The hypothesis that diversification has proceeded similarly in Antarctic marine and terrestrial groups has not been tested. While the extinction of a diverse continental Antarctic biota is well established (13), mounting evidence of significant and biogeographically structured Antarctic terrestrial diversity (8,14,15) with a long evolutionary history (6,16) suggests the possibility of broadly similar diversification processes across marine and terrestrial Antarctic systems. If valid for some taxa, further tests should then be sought across a wider variety of organisms. ...
... While in some respects quite different to the continental Antarctic, the islands are in other ways quite similar, providing a window into diversification processes that might be sought for continental groups, especially given their age and biogeographic structuring. Both regions share many higher taxa (e.g., ref. 25), a dynamic geo-climatic history (6,26), a profound degree of isolation, and indications that climatic events likely structured their biota (6,8,27). The terrestrial habitat on the continent and its surrounding islands is fragmented by large expanses of ice or ocean, respectively, and has been further isolated by the Antarctic Circumpolar Current for at least 34 Ma (28,29). ...
Significance
The Antarctic environment is famously inhospitable to most terrestrial biodiversity, traditionally viewed as a driver of species extinction. Combining population- and species-level molecular data, we show that beetles on islands along the Antarctic Polar Front diversified in response to major climatic events over the last 50 Ma in surprising synchrony with the region’s marine organisms. Unique algae- and moss-feeding habits enabled beetles to capitalize on cooling conditions, which resulted in a decline in flowering plants—the typical hosts for beetles elsewhere. Antarctica’s cooling paleoclimate thus fostered the diversification of both terrestrial and marine life. Climatically driven evolutionary processes since the Miocene may underpin much of the region’s diversity, are still ongoing, and should be further investigated among Antarctic biota.
... The evolutionary history of Antarctic springtails has been studied in increasing detail using molecular tools over the last two decades [30][31][32][33] and a growing consensus has been obtained for their long-term persistence in Antarctica and survival in local refugia during glacial maxima [34,35]. Present-day populations are the descendants of lineages that colonized suitable environments up to many millions of years ago, subsequently persisting through multiple and intense periods of glaciation [36,37]. ...
... It is also not long before the very extensive glaciations in the Miocene, around 12-14 Mya, which are associated with the final extinction of remaining "tundra" communities in the Transantarctic Mountains [37,45]. ...
... An alternative, systematic source of uncertainty may lay in the use of calibration points that are very distant, both in terms of time and taxonomy, from the group of interest. This cannot be discounted in the current analysis, as available calibration points within Collembola are limited to two Palaeozoic nodes [37,[46][47][48] for a compilation of fossil Collembola that may be deployed provided adequate taxon sampling is available). Future dating analyses specifically focused on Antarctic divergences are clearly required, although the associated difficulties (e.g., the availability of appropriate calibration points that do not themselves derive from phylogeographic interpretations, considering that the resulting dates are to be used to test phylogeographic hypotheses) at present preclude this possibility. ...
Springtails and mites are the dominant groups of terrestrial arthropods in Antarctic terrestrial ecosystems. Their Antarctic diversity includes a limited number of species, which are frequently endemic to specific regions within the continent. Advances in molecular techniques, combined with the re-evaluation of morphological characters and the availability of new samples, have recently led to the identification of a number of new springtail species within previously named, but ill-defined, species entities described in the last century. One such species, the neanurid Friesea grisea, originally described from sub-Antarctic South Georgia, was for many years considered to be the only known springtail with a pan-Antarctic distribution. With the recent availability of new morphological and molecular data, it has now been firmly established that the different representatives previously referred to this taxon from the Antarctic Peninsula and Victoria Land (continental Antarctica) should no longer be considered as representing one and the same species, and three clearly distinct taxa have been recognized: F. antarctica, F. gretae and F. propria. In this study, the relationships among these three species are further explored through the sequencing of the complete mtDNA for F. gretae and the use of complete mitogenomic as well as cytochrome c oxidase I data. The data obtained provide further support that distinct species were originally hidden within the same taxon and that, despite the difficulties in obtaining reliable diagnostic morphological characters, F. gretae is genetically differentiated from F. propria (known to be present in different locations in Northern Victoria Land), as well as from F. antarctica (distributed in the Antarctic Peninsula).
... The complex history of Antarctic colonization here recorded in B. argenteum and its persistence through glacial periods within the continent complements recent observations in multiple groups of terrestrial biota (Biersma et al., 2017;Convey et al., 2008Convey et al., , 2018Convey et al., , 2020McGaughran, Tearuds, Convey, & Fraser, 2019), including many invertebrate groups, lichens, and other mosses that currently occur in habitats and areas that are also commonly characterized by B. argenteum. These important components of the Antarctic biota must therefore have had environmentally suitable refugia available to them (Convey et al., , 2020. ...
... The complex history of Antarctic colonization here recorded in B. argenteum and its persistence through glacial periods within the continent complements recent observations in multiple groups of terrestrial biota (Biersma et al., 2017;Convey et al., 2008Convey et al., , 2018Convey et al., , 2020McGaughran, Tearuds, Convey, & Fraser, 2019), including many invertebrate groups, lichens, and other mosses that currently occur in habitats and areas that are also commonly characterized by B. argenteum. These important components of the Antarctic biota must therefore have had environmentally suitable refugia available to them (Convey et al., , 2020. However, the precise locations of such refugia remain unknown , as does the degree of connectivity or isolation between individual locations. ...
... within bank-forming mosses over a period of up to two millennia preserved in permafrost. In Victoria Land, cold-based glaciers were widespread between c. 5-7 Ma and 2.5 Ma (Di Nicola et al., 2012;Smellie et al., 2014), providing the possibility of survival during glaciations through cryptobiosis, although it has to be accepted that the duration of glacial periods (tens to hundreds of thousands of years) is considerably longer than any currently available demonstration of cryptobiotic survival other than in microorganisms (Convey et al., 2020). ...
The dispersal routes of taxa with transoceanic disjunctions remain poorly understood, with the potential roles of Antarctica not yet demonstrated. Mosses are suitable organisms to test direct intra‐Antarctic dispersal, as major component of the extant Antarctic flora, with the cosmopolitan moss Bryum argenteum as ideal target species. We analyzed the genetic structure of B. argenteum to provide an evolutionary time frame for its radiation and shed light into its historical biogeography in the Antarctic region. We tested two alternative scenarios: (a) intra‐Antarctic panmixia and (b) intra‐Antarctic genetic differentiation. Furthermore, we tested for evidence of the existence of specific intra‐Antarctic dispersal routes. Sixty‐seven new samples (40 collected in Antarctica) were sequenced for ITS nrDNA and rps4 cpDNA regions, and phylogenetic trees of B. argenteum were constructed, with a focus on its Southern Hemisphere. Combining our new nrDNA dataset with previously published datasets, we estimated time‐calibrated phylogenies based on two different substitution rates (derived from angiosperms and bryophytes) along with ancestral area estimations. Minimum spanning network and pairwise genetic distances were also calculated. B. argenteum was potentially distributed across Africa and Antarctica soon after its origin. Its earliest intra‐Antarctic dispersal and diversification occurred during a warming period in the Pliocene. On the same timescale, a radiation took place involving a dispersal event from Antarctica to the sub‐Antarctic islands. A more recent event of dispersal and diversification within Antarctica occurred during a warm period in the Pleistocene, creating favorable conditions also for its colonization outside the Antarctic continent worldwide. We provide evidence supporting the hypothesis that contemporary populations of B. argenteum in Antarctica integrate a history of both multiple long‐range dispersal events and local persistence combined with in situ diversification. Our data support the hypothesis that B. argenteum has been characterized by strong connectivity within Antarctica, suggesting the existence of intra‐Antarctic dispersal routes.
... Terrestrial life in the Antarctic is concentrated in the few ice-free areas; is well adapted to extremely low temperatures, strong winds, freeze-thaw cycling and nutrient deficiency (Convey 1996;Rogers et al. 2012); is highly endemic Convey et al. 2020) and has a long evolutionary history (Convey & Stevens 2007;Convey et al. 2008;Fraser et al. 2012;Convey et al. 2020). Microscopic metazoans, which include rotifers, nematodes and tardigrades, are important components of terrestrial species assemblages and inhabit both soils, the so-called 'chalikosystems' proposed by Janetschek (1963Janetschek ( , 1967, and microbiotopes, forming in moss cushions, lichen and algal thalli (the so-called 'bryosystems'). ...
... Terrestrial life in the Antarctic is concentrated in the few ice-free areas; is well adapted to extremely low temperatures, strong winds, freeze-thaw cycling and nutrient deficiency (Convey 1996;Rogers et al. 2012); is highly endemic Convey et al. 2020) and has a long evolutionary history (Convey & Stevens 2007;Convey et al. 2008;Fraser et al. 2012;Convey et al. 2020). Microscopic metazoans, which include rotifers, nematodes and tardigrades, are important components of terrestrial species assemblages and inhabit both soils, the so-called 'chalikosystems' proposed by Janetschek (1963Janetschek ( , 1967, and microbiotopes, forming in moss cushions, lichen and algal thalli (the so-called 'bryosystems'). ...
To elucidate poorly known aspects of the microscopic metazoan distribution in ice-free parts of the Antarctic, we examined samples of the multicellular terrestrial alga Prasiola crispa, collected over the last decade in different parts of continental East Antarctica and Haswell Island. We found that the micrometazoans inhabiting the algae consist of remarkably abundant bdelloid rotifers (subclass Bdelloidea), followed by tardigrades. We did not find nematodes. The rotifer assemblages were characterized by low diversity (only six species). Nevertheless, rotifer densities were extremely high: mean densities ranged from 75 to 3030 individuals per 100 mg of the dry sample weight and the maximum value numbered in excess of 8000 per 100 mg of the dry sample weight. These data show that terrestrial algae, along with mosses, are a very attractive habitat for rotifers and tardigrades in the Antarctic. The statistical analysis showed a lack of correlations between rotifer and tardigrade densities and nutrients (N, C, P, K and Na). Our findings are consistent with the patchy distribution of terrestrial micrometazoans in the Antarctic that has previously been found.
... The Antarctic terrestrial vegetation is assembled in extensive tufts over 0.3% of the permanent ice-free surface (Convey et al., 2020). The main components are lichens, which comprise 65% of the total species identified (Casanovas et al., 2015). ...
... The successful survival of this group is facilitated by their poikilohydric nature because their hydration status tends to be in equilibrium with the environment, where they are metabolically active when hydrated and dormant when dry. Dormancy constitutes an abiotic stress avoidance strategy that ensures the survival of these species . This response trait (any trait that varies in response to changes in environmental conditions according to Violle et al. (2007)) is widespread in various organisms, such as mosses, nematodes, tardigrades, rotifers, and collembolans (Convey et al., 2020). ...
Poikilohydric autotrophs are the main colonizers of the permanent ice-free areas in the Antarctic tundra biome. Global climate warming and the small human footprint in this ecosystem make it especially vulnerable to abrupt changes. Elucidating the effects of climate change on the Antarctic ecosystem is challenging because it mainly comprises poikilohydric species, which are greatly influenced by microtopographic factors. In the present study, we investigated the potential effects of climate change on the metabolic activity and net primary productivity (NPP) in the widespread lichen species Usnea aurantiaco-atra. Long-term monitoring of chlorophyll a fluorescence in the field was combined with photosynthetic performance measurements in laboratory experiments in order to establish the daily response patterns under biotic and abiotic factors at micro- and macro-scales. Our findings suggest that macroclimate is a poor predictor of NPP, thereby indicating that microclimate is the main driver due to the strong effects of microtopographic factors on cryptogams. Metabolic activity is also crucial for estimating the NPP, which is highly dependent on the type, distribution, and duration of the hydration sources available throughout the year. Under RCP 4.5 and RCP 8.5, metabolic activity will increase slightly compared with that at present due to the increased precipitation events predicted in MIROC5. Temperature is highlighted as the main driver for NPP projections, and thus climate warming will lead to an average increase in NPP of 167–171% at the end of the century. However, small changes in other drivers such as light and relative humidity may strongly modify the metabolic activity patterns of poikilohydric autotrophs, and thus their NPP. Species with similar physiological response ranges to the species investigated in the present study are expected to behave in a similar manner provided that liquid water is available.
... The Thala Hills terrestrial biota includes a high proportion of endemic species (Fig. 5), a feature that is being increasingly strongly recognized across Antarctica , Convey et al. 2020. Most of the lichens present in Thala Hills are widely represented in polar vegetation and are either Antarctic endemics or have bipolar distributions. ...
... Where such studies have been applied (e.g. Iakovenko et al. 2015), the general conclusion is that Antarctic representatives are clearly distinct from other relatives globally, as is the case in other groups of terrestrial fauna (reviewed by Convey et al. 2020). There is a similar lack of up-to-date taxonomic reconsideration of tardigrades across much of Antarctica. ...
Knowledge of the biodiversity of the Thala Hills oasis (Enderby Land, East Antarctica) is very limited. Here, we integrate all information available since 1962, when the Russian ‘Molodyozhnaya’ station was established in the western part of the oasis. The published data on local eukaryote diversity (lichens, embryophytes, metazoans) include records of 90 species. Since 2008, Belarusian Antarctic Expedition researchers have worked in the eastern part of the oasis, accessible from the Belarusian station ‘Vechernyaya Mount'. This research revealed 95 species, including 44 species not recorded in the earlier published literature. The level of available information is uneven across major taxa. Lichens are the better-known group, with 51 species recorded in total, including 13 species recently recorded for the first time in the oasis. New records were also obtained for rotifers. Thala Hills biodiversity is consistent with wider patterns of Antarctic biogeography, with a high proportion of regionally endemic species (especially metazoans), the occurrence of both endemic and bipolar species of lichens and generally low numbers of cosmopolitan species (largely limited to aquatic rotifers, with the caveat that up-to-date taxonomic studies are required). The lack of data on marine macrobenthos, soil nematodes and terrestrial rotifers emphasizes the need for studies focusing on these groups.
... Habitats as diverse as paratropical to warm temperate forests, with frost-free polar winters during the Eocene, cold temperate southern beech and conifer forests during the Oligocene, and localized tundra-like shrubland during the early to mid-Miocene were present in Antarctica in the past. Oribatid mites and collembolans inhabiting Antarctic ice-free refugia today are remnants of the endemic faunas that inhabited these pre-glaciation forests (Convey et al., 2020;Mortimer et al., 2011). Rivers fed by glacial meltwater, habitats suitable for many aquatic insects, persisted in Antarctica at least until the mid-Miocene (Denton & Sugden, 2005). ...
Aim
Although Antarctica hosted a diverse fauna and flora in the past, its modern climate is too extreme for many lineages: their recent extinction makes it difficult to include the continent in historical biogeographical analyses. We use southern temperate stream‐inhabiting beetles as a model to explore whether Antarctica may be included in historical biogeographic reconstructions in a group absent from Antarctica today, and to test its role in shaping the current distribution of stream‐inhabiting insects.
Taxon
Coleoptera, Elmidae.
Location
Southern Hemisphere temperate regions and Antarctica.
Methods
We included Antarctica in historical biogeographic analyses indirectly, as a component of distance matrices specifying the relative positions of continents, or by specifying Antarctica as a stepping‐stone between remaining continents (in LEMAD). We used a newly constructed dated phylogeny of Elmidae to test the performance of these constrained analyses under different parameter settings and geographical scenarios.
Results
Antarctica can be implemented into historical biogeographic analyses via indirect constraints to produce biologically relevant reconstructions when long‐distance dispersal events are highly penalized, the maximum number of areas per species is low, and expected extinction rates are high (in LEMAD). Unconstrained models, including those without Antarctica, result in simpler scenarios with fewer biogeographic events and better fit to data. The origin of austral clades of Elmidae post‐date the separation of Gondwanan landmasses.
Main Conclusions
Antarctica can be included in historical biogeographic reconstructions under a priori assumptions that (1) it was part of the ancient biogeography of the clade, (2) the taxon has limited dispersal ability, making long‐distance dispersal highly unlikely and (3) maximum range size is limited. These assumptions may be biologically justified for many animal groups. Over‐water dispersal has been crucial in shaping the modern distribution of austral stream‐inhabiting beetles, likely facilitated by ocean currents and dispersal through Antarctica until the Oligocene.
... Antarctic species exhibit a high frequency of endemism (Greve et al., 2004;Pugh and Convey, 2008;Griffiths et al., 2009) and ancient species origins (Convey and Stevens, 2007;Convey et al., 2008;Vyverman et al., 2010). At a larger, regional scale there is very limited sharing of mite, springtail or nematode species between the Antarctic Peninsula and the continent across the Gressitt Line at the base of the Peninsula (Maslen and Convey, 2006;Chown and Convey, 2007;Convey et al., 2020). Barriers to migration and gene flow result from conspicuous impediments such as glaciers and the sea, along with others that may be less conspicuous such as the prevailing wind direction or related to extreme environmental events (Chown and Convey, 2007). ...
... In the South Shetland Islands (SSI), located in the north-west AP, glaciers currently extend over 86-95% of the land surface of the major islands (RGI Consortium, 2017). The shrinking of ice caps during the Holocene has exposed coastal lowlands along the margins of the islands, which constitute some of the greatest hotspots of biodiversity of the entire continent (Convey et al., 2020). Spatio-temporal patterns of glacial retreat in these islands are of major importance for understanding the factors and processes controlling present-day geoecological dynamics in ice-free environments. ...
The timing and magnitude of Holocene glacial oscillations in most currently ice‐free areas of Antarctica remain unknown. This work focuses on the recent deglaciation in the northern sector of the Fildes Peninsula, King George Island, northern Antarctic Peninsula. The ice cap covering ca. 90% of the island has receded since the Last Glacial Maximum and exposed ca. 29 km ² of ice‐free land. We reconstruct its glacial history based on a dataset of 12 ³⁶ Cl exposure ages obtained through cosmic‐ray exposure (CRE) dating of moraine boulders, polished surfaces and erratic boulders surrounding the peninsula's northern plateau. Results reveal that the deglaciation of the northern Fildes Peninsula took place during the Holocene Thermal Maximum at 7–6 ka, when warm conditions promoted a massive glacial retreat. The present arrangement of ice‐free areas was in place by 6 ka. Small cirque moraines suggest the subsequent occurrence of favourable climate conditions for glacial expansion fed by intense snow deflation at 4.6 and 1 ka at the foot of the northern plateau. The deglaciation pattern of the Fildes Peninsula resulted from the combined shrinkage of different ice masses, rather than of the long‐term retreat of the King George Ice Cap. No evidence of glacier expansion during more recent cold periods (i.e. the Little Ice Age) was found. These results fit well with regional deglacial histories inferred from lacustrine sediments and raised beaches and complement the existing chronological framework to help better understand the peninsula's Holocene geoecological dynamics.
... Assuming that the nunataks of Edward VII Peninsula were similarly ice-covered during the LGM, then mosses and lichens must either have survived below the ice cover or have recolonized through dispersal from elsewhere as rock surfaces gradually emerged. The survival of Antarctic terrestrial biota through the LGM, either in ice-free refugia or by cryptobiosis in ice or permafrost, has been discussed by Convey et al. (2020). They provided an overview of the evidence that mosses survive ice burial for periods of centuries to millennia but concluded that it is unknown whether their survival would be possible through entire glacial cycles. ...
This is the first detailed study of the distribution of mosses and lichens at Alexandra Mountains and Rockefeller Mountains, Edward VII Peninsula, Antarctica. A total of 418 samples was collected on 21 nunataks in the summer of 1987–1988. Lichens included 44 taxa, bringing the total known from Edward VII Peninsula to 50. Ten lichen species were new records for the Continental Antarctic zone, whilst only six were endemic to that zone. There were six species and one variety of moss, bringing the total known from Edward VII Peninsula to seven species and one variety. These included the first record of a species of Orthotrichum in Continental Antarctica. Two other species and a variety were new records for Edward VII Peninsula. Overall, the flora was species rich for a Continental Antarctic region and was comparable with the species-rich sites of Botany Bay and Kar Plateau, which are at approximately the same latitude (77°S) in southern Victoria Land. This rich flora was probably supported by a reliable summer water supply from melting snowfall and snowdrift and by the range of microenvironments at nunataks with different degrees of nutrient enrichment from nesting birds.
... With global environmental change accelerating at an unprecedented rate, we urgently need to understand the larger scale evolutionary patterns that have shaped biodiversity patterns, in order to forecast future changes and manage at-risk ecosystems. The Antarctic region, where endemic biodiversity has evolved in relative isolation (Convey et al. , 2014(Convey et al. , 2020, encompasses many of these ecosystems and is facing the concomitant threats of rapid environmental change and increasing connectivity, both between Antarctic and non-Antarctic regions and among sites within the region, as the climate rapidly warms and human activity increases (Convey 2011, Convey andPeck 2019). ...
Much of Antarctica's highly endemic terrestrial biodiversity is found in small ice‐free patches. Substantial genetic differentiation has been detected among populations across spatial scales. Sampling is, however, often restricted to commonly‐accessed sites and we therefore lack a comprehensive understanding of broad‐scale biogeographic patterns, which could impede forecasts of the nature and impacts of future change. Here, we present a synthesis of published genetic studies across terrestrial Antarctica and the broader Antarctic region, aiming to identify current biogeographic patterns, environmental drivers of diversity and future research priorities. A database of all published genetic research from terrestrial fauna and flora (excl. microbes) across the Antarctic region was constructed. This database was then filtered to focus on the most well‐represented taxa and markers (mitochondrial COI for fauna, and nuclear ITS for flora). The final dataset comprised 7222 records, spanning 153 studies of 335 different species. There was strong taxonomic bias towards flowering plants (52% of all floral data sets) and springtails (54% of all faunal data sets), and geographic bias towards the Antarctic Peninsula and Victoria Land. Recent connectivity between the Antarctic continent and neighbouring landmasses, such as South America and the Southern Ocean Islands (SOIs), was inferred for some groups, but patterns observed for most taxa were strongly influenced by sampling biases. Above‐ground wind speed and habitat heterogeneity were positively correlated with genetic diversity indices overall though environment was a generally poor predictor of genetic diversity. The low resolution and variable coverage of data may also have reduced the power of our comparative inferences. In the future, higher‐resolution data, such as genomic SNPs and environmental modelling, alongside targeting sampling of remote sites and under sampled taxa, will address current knowledge gaps and greatly advance our understanding of evolutionary processes across the Antarctic region.
... Only 0.3% of the land surface is currently ice-free and suitable for terrestrial life, with most ice-free areas small, fragmented and isolated from each other (Bergstrom and Chown, 1999;Convey et al., 2008;Convey and Stevens, 2007). This long-term isolation has led to evolutionary divergence and speciation, creating the high levels of endemism characterising multiple terrestrial invertebrate groups currently present in Antarctica, including mites, springtails, rotifers and nematodes (Cakil et al., 2021;Convey et al., 2020Convey et al., , 2008Pugh and Convey, 2008;Stevens et al., 2021;Velasco-Castrillón et al., 2014). ...
Antarctica has been isolated and progressively glaciated for over 30 million years, with only approximately 0.3 % of its area currently ice-free and capable of supporting terrestrial ecosystems. As a result, invertebrate populations have become isolated and fragmented, in some cases leading to speciation. Terrestrial invertebrate species currently found in Antarctica often show multi-million year, and even Gondwanan, heritage, with little evidence of recent colonisation. Mesobiotus is a globally distributed tardigrade genus. It has commonly been divided into two “groups”, referred to as harmsworthi and furciger, with both groups currently considered cosmopolitan, with global reports including from both the Arctic and the Antarctic. However, some authors considered that Meb. furciger, as originally described, may represent an Antarctic-specific lineage. Using collections of tardigrades from across the Antarctic continent and publicly available sequences obtained from online databases, we use mitochondrial and nuclear ribosomal sequence data to clarify the relationships of Antarctic Mesobiotus species. Our analyses show that all Antarctic members belong to a single lineage, evolving separately from non-Antarctic representatives. Within this Antarctic lineage there are further deep divisions among geographic regions of the continent, consistent with the presence of a species complex. Based on our data confirming the deep divisions between this Antarctic lineage, which includes representatives of both groups, we recommend that the use of furciger and harmsworthi group terminology is now abandoned, as it leads to systematic and biogeographical confusion.
(Bertolani et al., 2014, Itang et al., 2020, Kaczmarek et al., 2018, Kayastha et al., 2021, Mapalo et al., 2017, Mapalo et al., 2016, Roszkowska et al., 2018, Stec, 2019, Stec et al., 2018, Stec and Kristensen, 2017; Tumanov, 2020)
... Green algae (Viridiplantae) are noted in all studies of Antarctic lake algal communities, represented mainly by the Phylum Chlorophyta [12], with zygnematophycean green algae and other taxa phylogenetically close to higher plants (Streptophyta) being less common. De Wever et al. [8] highlighted the wide phylogenetic diversity of apparently endemic Antarctic lineages of microscopic green algae, consistent with hypotheses of strong regionalization and long-term evolutionary isolation within Antarctica, even of microbial diversity [13][14][15]. According to De Wever et al. [8], their findings, supported by molecular analyses, contrasted with most previous morphological studies, which generally concluded that Antarctic green algae were mostly represented by cosmopolitan species. ...
Background
Vega Island is located off the eastern tip of the Antarctic Peninsula (Maritime Antarctica), in the Weddell Sea. In this study, we used metabarcoding to investigate green algal DNA sequence diversity present in sediments from three lakes on Vega Island (Esmeralda, Copépodo, and Pan Negro Lakes).
Methods and results
Total DNA was extracted and the internal transcribed spacer 2 region of the nuclear ribosomal DNA was used as a DNA barcode for molecular identification. Green algae were represented by sequences representing 78 taxa belonging to Phylum Chlorophyta, of which 32% have not previously been recorded from Antarctica. Sediment from Pan Negro Lake generated the highest number of DNA reads (11,205), followed by Esmeralda (9085) and Copépodo (1595) Lakes. Esmeralda Lake was the richest in terms of number of taxa (59), with Copépodo and Pan Negro Lakes having 30 taxa each. Bray–Curtis dissimilarity among lakes was high (~ 0.80). The Order Chlamydomonadales (Chlorophyceae) gave the highest contribution in terms of numbers of taxa and DNA reads in all lakes. The most abundant taxon was Chlorococcum microstigmatum.
Conclusions
The study confirms the utility of DNA metabarcoding in assessing potential green algal diversity in Antarctic lakes, generating new Antarctic records.
... En Isla Decepción, de origen volcánico, los estudios de la diversidad y desarrollo de la vegetación se han centrado en zonas de actividad geotérmica, donde la combinación de calor, vapor, inestabilidad del sustrato y concentraciones de nutrientes a menudo insignificantes o con niveles tóxicos de gases sulfurosos y depósitos minerales, imponen severas restricciones a la biota vegetal y liquénica (Smith 2005). A su vez, estos sectores ligados a un activo vulcanismo y elevada actividad geotérmica pueden haber jugado un papel determinante en la colonización vegetal del continente antártico (Convey et al. 2020), por lo que una caracterización precisa y detallada de la distribución de especies vegetales puede ayudar en una mejor comprensión de los patrones espacio-temporales de expansión de la vegetación de la Antártica. Desde el punto de vista botánico, Isla Decepción es particularmente importante, pues alberga un gran número de especies poco comunes de la Antártica, entre ellas musgos, hepáticas, y líquenes (Smith 2005). ...
Con el objetivo de determinar la influencia de las pingüineras sobre la diversidad de la vegetación en la Isla Decepción, se estudió la composición de briófitas de un transecto de aproximadamente 2 km entre el Lago Irízar y la pingüinera (Pygoscelis antarcticus) de Punta La Descubierta. Fueron detectados un total de 39 carpetas de vegetación formadas principalmente por briófitos, distribuidas en tres sectores principales, aledaño al Lago Irízar, en Collado Vapor y en Punta La Descubierta. Los briófitos registrados corresponden a 15 especies de musgos y sólo 2 hepáticas, con 11 familias representadas. Se detectó que dos musgos, Sanionia uncinata y Politrychastrum alpinum, con 31 y 9 registros, dominaban las carpetas, con mayor abundancia y frecuencia. Además, se encontró un nuevo registro para la isla del musgo Bryum orbiculatifolium, el cual crece directamente asociado a la pingüinera. Además, se encontró que hay 5 especies de musgos comunes a los tres sectores, aunque otras 5 especies crecen solo en el sector de la pingüinera, diferenciándose esta comunidad de las otras dos. No se detectaron plantas vasculares en todo el sitio de estudio, por lo que se discute la posibilidad de que estos sitios se encuentran en estados de colonización temprana y donde su biota está marcada por la presencia de musgos pioneros que crecen alrededor de las pingüineras, influenciadas probablemente por el aporte de nutrientes del guano depositado.
... But nunataks also have important implications for post-glacial geomorphic and environmental dynamics during the paraglacial phase, such as for vegetation colonization (Ruiz-Fern andez et al., 2019). They have been suggested to provide refugia to biodiversity during past glaciations, thus being pioneering sites for vegetation re-colonization following glacial retreat (Jørgensen et al., 2012) and key spots for species dispersal across migration routes from ice-free areas in the Maritime Antarctica to the interior of the continent (Convey et al., 2020). Therefore, a more accurate picture of the age of deglaciation and nunatak development in the Antarctic Peninsula region can be useful to better understand the pattern of colonization. ...
The small ice caps distributed across the Antarctic Peninsula region have undergone large ice volume changes since the Last Glacial Cycle, in line with most of the Antarctic continent. While the surface extent of glacial shrinking is relatively well known, the timing of glacial oscillations and the magnitude of ice thinning remain little investigated. Cosmic-Ray Exposure (CRE) dating applied on ice-free vertical sequences can provide insights about the temporal framework of glacial oscillations. However, the potential occurrence of nuclide inheritance may overestimate the real timing of the last glacial retreat. This problem has been observed in many areas in Continental Antarctica, but similar studies have not yet been conducted in environments of the Maritime Antarctica, such as the South Shetland Islands (SSI). This research focuses on the Hurd Peninsula ice cap (HPIC, ca. 60°22′ W, 62°40’ S), located in the SW of Livingston Island, SSI. Past climate oscillations since the Last Glacial Cycle have determined the amount of ice stored in the ice cap. Today, this polythermal ice cap is surrounded by several nunataks standing out above the ice. Three of them have been selected to explore their deglaciation history and to test the potential occurrence of nuclide inheritance in deglaciated bedrocks associated with polythermal glaciers. We present a new dataset with 10 10Be exposure dates. Some of them were found to be anomalously old, evidencing that nuclide inheritance is present in bedrocks associated with polythermal ice caps and suggesting complex glacial exposure histories. We attribute this to limited erosion, given the gentle slope of the nunatak margins and the cold-based character of the surrounding ice. The remaining samples allowed to approach local surface-elevation changes of the HPIC. Our results suggest that ice thinning started during the Last Glacial Maximum (LGM) at ∼22 ka but intense glacial shrinking occurred from ∼18 to ∼13 ka, when the nunataks became exposed, being particularly intense at the end of this period (∼14–13 ka) coinciding with the time of the meltwater pulse 1a (MWP-1a) and the end of the Antarctic Cold Reversal (ACR).
... These regions experience very different environmental conditions that strongly impact on the composition and functioning of their terrestrial ecosystems. Moreover, their microbiota and invertebrate fauna have long evolutionary histories in isolation 20,34,35 . The reduced diversity and richness of Antarctic springtail microbiomes, as well as the limited similarities observed between the four microbiomes analysed here, could be the result of strong environmental control, as well as of millions of years of evolutionary separation. ...
Collembola are a key component of the soil biota globally, playing an important role in community and ecosystem dynamics. Equally significant are their associated microbiomes, that can contribute to key metabolic functions. In the present study, we investigated the bacterial community composition of four Antarctic springtail species to assess if and how the extreme Antarctic environment has shaped the collembolans’ microbiomes. Springtails were collected from two biogeographical regions, the maritime and the continental Antarctic. From each region, two endemic species, belonging to the genera Cryptopygus (Isotomidae, Entomobryomorpha) and Friesea (Neanuridae, Poduromorpha), were included. This experimental design allowed us to quantify the relative importance of ecological factors (different regions of occurrence) and/or phylogenetic divergence in the host (different Orders) in shaping the Collembola microbiome. The diversity and richness of springtail microbiomes was lower in the Antarctic taxa compared to published information from species from temperate regions. The microbiome composition was predominantly species-specific, with a limited core microbiome shared across the four species examined. While both geographic origin and host species influenced the associated microbiomes, the former was the prevalent driver, with closer similarity between springtails from the same bioregion than between those belonging to the same genus.
... nematodes, tardigrades, mites and mosses) was proposed to feed into conservation planning and management (Terauds et al. 2012, Terauds andLee 2016). Proper conservation planning and management of the Antarctic is urgent for protecting its often endemic biota (Convey et al. 2014(Convey et al. , 2020 as most of them have narrow distributional ranges due to the long-term survival of taxa in isolated glacial refugia during ice ages , Fraser et al. 2014, Biersma et al. 2018). In the sub-Antarctic, isolation has long been thought to underpin patterns in its terrestrial biodiversity leading to three distinct provinces (Smith 1984), namely the South Atlantic, South Indian and South Pacific Provinces. ...
Terrestrial biota in the Antarctic are more globally distinct and highly structured biogeographically than previously believed, but information on biogeographic patterns and endemism in freshwater communities is largely lacking. We studied biogeographic patterns of Antarctic freshwater diatoms based on the analysis of species occurrences in a dataset of 439 lakes spread across the Antarctic realm. Highly distinct diatom floras, both in terms of composition and richness, characterize Continental Antarctica, Maritime Antarctica and the sub‐Antarctic islands, with marked biogeographic provincialism in each region. A total of 44% of all species is estimated to be endemic to the Antarctic, and most of them are confined to a single biogeographic region. The level of endemism significantly increases with increasing latitude and geographic isolation. Our results have implications for conservation planning, and suggest that successful dispersal of freshwater diatoms to and within the Antarctic is limited, fostering the evolution of highly endemic diatom floras.
... Recent climate and glaciological modeling studies have highlighted greater dynamism in glacial extent than previously considered possible throughout the early Pliocene and Pleistocene (Scherer et al., 2008;Naish et al., 2009;Pollard and DeConto, 2009;De Schepper et al., 2014;DeConto and Pollard, 2016), suggesting the possibility of ice-free local refugial areas persisting throughout these periods (e.g. as suggested by Fraser et al., 2014). Molecular, phylogenetic and biogeographic studies also suggest in situ survival for many groups of terrestrial fauna in Antarctica throughout the Quaternary, Neogene and even Paleogene (see Convey et al., 2008Convey et al., , 2009Convey et al., , 2020. Recently, increased evidence has also been found of million-year persistence of the Antarctic flora, e.g. ...
Biogeographic patterns of globally widespread species are expected to reflect regional structure, as well as connectivity caused by occasional long-distance dispersal. We assessed the level and drivers of population structure, connectivity, and timescales of population isolation in one of the most widespread and ruderal plants in the world — the common moss Ceratodon purpureus. We applied phylogenetic, population genetic, and molecular dating analyses to a global (n = 147) sampling data set, using three chloroplast loci and one nuclear locus. The plastid data revealed several distinct and geographically structured lineages, with connectivity patterns associated with worldwide, latitudinal “bands.” These imply that connectivity is strongly influenced by global atmospheric circulation patterns, with dispersal and establishment beyond these latitudinal bands less common. Biogeographic patterns were less clear within the nuclear marker, with gene duplication likely hindering the detection of these. Divergence time analyses indicated that the current matrilineal population structure in C. purpureus has developed over the past six million years, with lineages diverging during the late Miocene, Pliocene, and Quaternary. Several colonization events in the Antarctic were apparent, as well as one old and distinct Antarctic clade, possibly isolated on the continent since the Pliocene. As C. purpureus is considered a model organism, the matrilineal biogeographic structure identified here provides a useful framework for future genetic and developmental studies on bryophytes. Our general findings may also be relevant to understanding global environmental influences on the biogeography of other organisms with microscopic propagules (e.g., spores) dispersed by wind.
... Over the last two decades, rapid advances in classical biogeographic and molecular phylogeographic research have led to a paradigm change in our understanding of the origin and antiquity of the Antarctic terrestrial biota . Studies carried out across all ice-free regions of the continent, and all the major terrestrial taxonomic groups, have confirmed that long-term presence in these regions is the norm, requiring persistence of both the organisms and terrestrial habitats through the multiple cycles of glaciation Antarctica has experienced (see Convey et al., 2020, for comprehensive review). Some phylogeographic studies have identified signals of persistence since the final breakup of Gondwana and separation of Antarctica. ...
Antarctica's contemporary terrestrial biota have adapted to the continent's environmental challenges over many millions of years. It now faces the twin challenges of the multiple aspects of global and regional environmental change and the direct impacts of human presence and activity. Most native terrestrial biota possess wide physiological and ecological flexibility, well beyond the expected scale of environmental change over the next century and, when considered in isolation, are likely to show positive responses to environmental ameliorations, particularly the combination of increased thermal energy and liquid water availability, through increased production, populations, local distribution extent, and community complexity. However, over this timescale other, direct, human impacts on Antarctic terrestrial ecosystems and biodiversity are likely to have greater and negative consequences. Major sources of such impacts are likely to come through physical damage to the limited available area of terrestrial habitats, and the anthropogenic introduction of non-native species, a proportion of which are likely to become invasive and act as ecosystem engineers.
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.
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.
This study provides new species records (NRs) of macroalgal assemblages present in rocky habitats from the South Shetland Islands (SSI) and north-eastern Antarctic Peninsula (EAP), Weddell Sea. Surveys were conducted during the summers of 2013/2014 to 2017/2018 at Elephant, Deception, Half Moon and Vega islands. Data from the present study and those available in the literature from the western Antarctic Peninsula (WAP) were combined to provide an updated checklist, giving insights into macroecology and potential changes in thermohaline circulation patterns. A total of 48 macroalgal taxa were identified from our sampling, with eight representing NRs to the EAP sector of the Weddell Sea and five representing NRs to the SSI. Statistical differences among the assemblages from the SSI, WAP and EAP were identified. NRs, including opportunistic species and new information about the biogeographical distributions of species reported here, give insights into ecoregional connectivity and environmental changes. This study updates macroalgal diversity records in regions that are currently experiencing the impacts of climate change. Future and ongoing monitoring for conservation purposes is required to detect non-native species, new dispersal pathways and patterns related to thermohaline anomalies in Antarctic waters.
Protection of Antarctica's biodiversity and ecosystem values is enshrined in the Protocol on Environmental Protection to the Antarctic Treaty, which provides for the designation of Antarctic Specially Protected Areas (ASPAs) to areas with outstanding values. Concern has been raised that existing ASPAs fail to prioritize areas to maximize the likelihood of ensuring the long-term conservation of Antarctic ecosystems and biodiversity. The absence of systematic and representative protection is particularly acute for inland aquatic ecosystems, which support a disproportionate amount of inland biodiversity. This paper promotes the case for overt inclusion of inland waters as a critical component of a representative protected area framework for Antarctica, thereby addressing their current underrepresentation. We set out a structured approach to enable the selection of representative freshwater systems for inclusion in the ASPA framework that, with modification, could also be applied across other Antarctic habitats. We acknowledge an overall lack of information on the biogeography of inland aquatic diversity and recommend increased use of remote data collection along with classification tools to mitigate this, as well as the need for the consideration of catchment-scale processes. Changes that accompany contemporary and anticipated climate change make the need for the conservation of representative biodiversity increasingly urgent.
Anthropogenic activity in Antarctica has increased due to the various scientific expeditions and tourism. Lake water sampling was carried out during the 34th Indian Scientific Expedition to Antarctica (ISEA) in the austral summer of 2014–2015. A total of 60 samples were collected from Grovnes & Broknes peninsula, Larsemann Hill, East Antarctica. The aim of this study was to investigate the physico-chemical parameters such as pH, total dissolved solids (TDS), electrical conductivity (EC), chloride (Cl−), total hardness (TH), nitrate (NO3−), nitrite (NO2−), phosphorus (P), sulphate (SO4−−), cyanide (CN−), chlorine (Cl), sulphide (S−−), and heavy metals like Al, Fe, Mn, Zn, Cu, Ni, and Cr in the collected samples. We also analysed indices like the potential ecological risk factor (Er) and potential ecological risk index (RI). We found pH (6.33–7.10), TDS (26.33–1128.0 mg/l), EC (0.06–2.25 μS/cm), Cl− (5.09–117.07 mg/l), TH (10.18–122.16 mg/l), NO3− (0.02–0.61 mg/l), NO2− (0.02–1.32 mg/l), P (0.29–3.27 mg/l), SO4−− (1.08–10.15 mg/l), CN− (0.01–0.26 mg/l), Cl (0.06–2.17 mg/l), S−− (0.01–0.84 mg/l), Al (0.01–0.79 µg/l), Fe (0.01–3.27 µg/l), Mn (0.14–12.83 µg/l), Zn (0.07–2.44 µg/l), Cu (0.01–5.37 µg/l), Ni (0.02–0.60 µg/l), and Cr (0.01–0.82 µg/l) in different ranges. We conclude that most of the parameters were found within the limits set by IS:10500 except some parameters like TDS was found higher in L6 NG, L7A NG, L7B NG, L1 SG, & L4 SG; Cl was found higher in L1E NG, P2 B, P3 B, P4 B, & Reid B; CN− was found higher in P2 B, & P4 B; S— was found higher in P2 B, P3 B, P4 B, & Reid B. In the future, the presence of new emerging pollutants like microplastics, and phthalate must be analysed in order to comprehensively assess the scale of environmental pollution in Antarctica.
The origin of terrestrial biota in Antarctica has been debated since the discovery of springtails on the first historic voyages to the southern continent more than 120 years ago. A plausible explanation for the long-term persistence of life requiring ice-free land on continental Antarctica has, however, remained elusive. The default glacial eradication scenario has dominated because hypotheses to date have failed to provide a mechanism for their widespread survival on the continent, particularly through the Last Glacial Maximum when geological evidence demonstrates that the ice sheet was more extensive than present. Here, we provide support for the alternative nunatak refuge hypothesis-that ice-free terrain with sufficient relief above the ice sheet provided refuges and was a source for terrestrial biota found today. This hypothesis is supported here by an increased understanding from the combination of biological and geological evidence, and we outline a mechanism for these refuges during successive glacial maxima that also provides a source for coastal species. Our cross-disciplinary approach provides future directions to further test this hypothesis that will lead to new insights into the evolution of Antarctic landscapes and how they have shaped the biota through a changing climate.
Antarctic soils provide an excellent setting to test biogeographical patterns across spatial and environmental scales given their relatively simple communities and the dominance of physical factors that create strong environmental gradients. Additional urgency is given by the fact that their unique terrestrial communities are the subject of conservation efforts in a rapidly changing environment. We investigated relationships of soil community assembly and alpha and beta diversity with climatic and environmental parameters across regional and local scales in Maritime Antarctica. We sampled from a regional gradient of sites that differ in habitat severity, ranging from relatively favourable to harsher physicochemical conditions. At the regional scale, bacterial community characteristics and microarthropod abundance varied along this severity gradient, but most measures of fungal communities did not. Microarthropod and microbial communities differed in which soil and climate parameters were most influential, and the specific parameters that influenced each taxon differed across broad and fine spatial scales. This suggests that conservation efforts will need to focus on a large variety of habitat characteristics to successfully encompass diversity across taxa. Because beta diversity was the result of species turnover, conservation efforts also cannot focus on only the most biodiverse sites to effectively preserve all aspects of biodiversity.
Persistencia en refugio y re-colonización desde Sudamérica. Ambas hipótesis contrastantes habrían sido parte de la historia evolutiva de Boeckella poppei, la especie más dominante de los ecosistemas dulceacuícolas de Antártica. Nueva contribución a nuestro entendimiento de la biodiversidad Antártica y sub-Antártica.
Persistence in refuge and re-colonization from South America. Both contrasting hypotheses would have been part of the evolutionary history of Boeckella poppei, the most dominant species in Antarctica's freshwater ecosystems. New contribution to our understanding of Antarctic and sub-Antarctic biodiversity.
Terrestrial environments of Antarctica include some of the most extreme on Earth, challenging the very existence of life itself. This article outlines briefly the geological and biological history of the continent, leading on to the conditions currently experienced, before describing its terrestrial biogeography and biota. Major determinants of terrestrial biodiversity and ecosystem function are discussed and consideration given to natural and human-induced processes of ecosystem development and change.
Intensive human exploitation of the Antarctic fur seal ( Arctocephalus gazella ) in its primary population centre on sub-Antarctic South Georgia, as well as on other sub-Antarctic islands and parts of the South Shetland Islands, in the eighteenth and nineteenth centuries rapidly brought populations to the brink of extinction. The species has now recovered throughout its original distribution. Non-breeding and yearling seals, almost entirely males, from the South Georgia population now disperse in the summer months far more widely and in higher numbers than there is evidence for taking place in the pre-exploitation era. Large numbers now haul out in coastal terrestrial habitats in the South Orkney Islands and also along the north-east and west coast of the Antarctic Peninsula to at least Marguerite Bay. In these previously less- or non-visited areas, the seals cause levels of damage likely never to have been experienced previously to fragile terrestrial habitats through trampling and over-fertilisation, as well as eutrophication of sensitive freshwater ecosystems. This increased area of summer impact is likely to have further synergies with aspects of regional climate change, including reduction in extent and duration of sea ice permitting seals access farther south, and changes in krill abundance and distribution. The extent and conservation value of terrestrial habitats and biodiversity now threatened by fur seal distribution expansion, and the multiple anthropogenic factors acting in synergy both historically and to the present day, present a new and as yet unaddressed challenge to the agencies charged with ensuring the protection and conservation of Antarctica’s unique ecosystems.
Anthropogenic climate change is causing observable changes in Antarctica and the Southern Ocean including increased air and ocean temperatures, glacial melt leading to sea‐level rise and a reduction in salinity, and changes to freshwater water availability on land. These changes impact local Antarctic ecosystems and the Earth’s climate system. The Antarctic has experienced significant past environmental change, including cycles of glaciation over the Quaternary Period (the past ~2.6 million years). Understanding Antarctica’s paleoecosystems, and the corresponding paleoenvironments and climates that have shaped them, provides insight into present day ecosystem change, and importantly, helps constrain model projections of future change. Biological archives such as extant moss beds and peat profiles, biological proxies in lake and marine sediments, vertebrate animal colonies, and extant terrestrial and benthic marine invertebrates, complement other Antarctic paleoclimate archives by recording the nature and rate of past ecological change, the paleoenvironmental drivers of that change, and constrain current ecosystem and climate models. These archives provide invaluable information about terrestrial ice‐free areas, a key location for Antarctic biodiversity, and the continental margin which is important for understanding ice sheet dynamics. Recent significant advances in analytical techniques (e.g., genomics, biogeochemical analyses) have led to new applications and greater power in elucidating the environmental records contained within biological archives. Paleoecological and paleoclimate discoveries derived from biological archives, and integration with existing data from other paleoclimate data sources, will significantly expand our understanding of past, present and future ecological change, alongside climate change, in a unique, globally significant region.
Arctic, Antarctic and alpine regions are the major elements of the cryosphere, with the polar regions comprising about 14% of the Earth’s surface. These environments differ in various respects. Antarctica experiences much more severe climatic conditions overall in comparison to Arctic and alpine regions. Alpine areas display considerable climatic gradients at more local scale, for instance from cooler areas at higher altitude to much warmer valleys. In the polar regions, lakes are present in both coastal and interior areas, varying widely in both trophic (ultra-oligotrophic to eutrophic) and osmotic (almost pure meltwater to hypersaline brines) status. In alpine regions, lakes are present in the Rocky Mountains of North America, the European Alps, the Himalayas, the Tibetan plateau in central and western Asia and the South American Andes. Among the microorganisms present in polar and alpine aquatic ecosystems, fungi are important decomposing organisms playing key roles in recycling nutrients. Fungal phyla commonly present in these lakes include Rozellomycota, Chytridiomycota, Ascomycota, Mortierellomycota, Blastocladiomycota, Basidiomycota and Mucoromycota. Polar and alpine regions include fragile and sensitive ecosystems, potentially vulnerable to rapid and considerable damage through the impacts of contemporary anthropogenic climate changes and other direct human impacts. However, despite the urgency of these large direct and indirect anthropogenic impacts, the diversity and ecological functions of fungi in polar and alpine aquatic environments have been little studied.
The temperature experienced by micro-invertebrates in extreme environments (such as those of Antarctica) is a pivotal parameter regarding these animals' ecology and physiology. However, at present, detailed knowledge of microhabitat physical conditions in Antarctica is limited, as well as being biased towards sub-Antarctic and Maritime Antarctic regions. To better understand the temperature conditions experienced in the microhabitats of Continental Antarctica by the native microfauna, we recorded temperatures year round in ponds and soils in an area of the Victoria Land coast and compared these measurements with air temperature data from the closest automatic weather station. We identified an important difference in temperature dynamics between the air, soil and pond datasets. Ponds were the warmest sites overall, differing by up to 7.5°C in comparison with the air temperature due to their greater thermal capacity, which also drove their patterns of freeze-thaw cycles and mean daily thermal excursion.
In the harsh Antarctic terrestrial ecosystems, invertebrates are currently confined to sparse and restricted ice free areas, where they have survived on multi-million-year timescales in refugia. The limited dispersal abilities of these invertebrate species, their specific habitat requirements, and the presence of geographical barriers can drastically reduce gene flow between populations, resulting in high genetic differentiation. On continental Antarctica, mites are one of the most diverse invertebrate groups. Recently, two new species of the free living prostigmatid mite genus Stereotydeus Berlese, 1901 were discovered, bringing the number of Antarctic and sub-Antarctic species of this genus up to 15, of which 7 occur along the coast of Victoria Land and in the Transantarctic Mountains. To examine the biodiversity of Stereotydeus spp., the present study combines phylogenetic, morphological and population genetic data of specimens collected from nine localities in Victoria Land. Genetically distinct intraspecific groups are spatially isolated in northern Victoria Land, while, for other species, the genetic haplogroups more often occur sympatrically in southern Victoria Land. We provide a new distribution map for the Stereotydeus species of Victoria Land, which will assist future decisions in matters of the protection and conservation of the unique Antarctic terrestrial fauna.
Aim
We investigated evolutionary relationships and biogeographical patterns within the genus Boeckella to evaluate (1) whether its current widespread distribution in the Southern Hemisphere is due to recent long-distance dispersal or long-term diversification; and (2) the age and origin of sub-Antarctic and Antarctic Boeckella species, with particular focus on the most widely distributed species: Boeckella poppei.
Location
South America, sub-Antarctic islands, maritime Antarctica, continental Antarctica and Australasia.
Methods
To reconstruct phylogenetic patterns of Boeckella, we used molecular sequence data collected from 12 regions and applied Bayesian and Maximum Likelihood analyses using multiple loci. We also estimated divergence times and reconstructed ancestral ranges using two different models of species evolution.
Results
Phylogenetic analyses and divergence time estimates suggested that Boeckella originated on the Gondwanan supercontinent and initially split into two main clades during the late Cretaceous (ca. 80 Ma). The first clade diversified in Australasia, and the second clade is currently distributed in South America, various sub-Antarctic islands and Antarctica. Dispersal from South America to the Kerguelen and Crozet archipelagos occurred during the Eocene/Oligocene (B. vallentini) and in the late Pliocene (B. brevicaudata), while South Georgia and the maritime Antarctic were likely colonized during the late Pleistocene (B. poppei).
Main conclusions
Boeckella has a Gondwanan origin, with further diversifications after the physical separation of the continental landmasses. Extant populations of Boeckella from the Scotia Arc islands and Antarctic Peninsula originated from South America during the Pleistocene, suggesting that original Antarctic Gondwanan lineages did not survive repeated glacial cycles during the Quaternary ice ages. A continuous decline in the species accumulation rate is apparent within the genus as the early Eocene, suggesting that Boeckella diversification may have decreased due to progressive cooling throughout the Cenozoic era.
The invertebrate terrestrial fauna of Antarctica is being investigated with increasing interest to discover how life interacts with the extreme polar environment and how millions of years of evolution have shaped their biodiversity. Classical taxonomic approaches, complemented by molecular tools, are improving our understanding of the systematic relationships of some species, changing the nomenclature of taxa and challenging the taxonomic status of others. The springtail Friesea grisea has previously been described as the only species with a “pan-Antarctic” distribution. However, recent genetic comparisons have pointed to another scenario. The latest morphological study has confined F. grisea to the sub-Antarctic island of South Georgia, from which it was originally described, and resurrected F. antarctica as a congeneric species occurring on the continental mainland. Molecular data demonstrate that populations of this taxon, ostensibly occurring across Maritime and Continental Antarctica, as well as on some offshore islands, are evolutionarily isolated and divergent and cannot be included within a single species. The present study, combining morphological with molecular data, attempts to validate this hypothesis and challenges the taxonomic status of F. antarctica, suggesting that two additional new species, described here as Friesea gretae sp. nov. and Friesea propria sp. nov., are present in Continental Antarctica.
The dispersal routes of taxa with transoceanic disjunctions remain poorly understood, with the potential roles of Antarctica not yet demonstrated. Mosses are suitable organisms to test direct intra‐Antarctic dispersal, as major component of the extant Antarctic flora, with the cosmopolitan moss Bryum argenteum as ideal target species. We analyzed the genetic structure of B. argenteum to provide an evolutionary time frame for its radiation and shed light into its historical biogeography in the Antarctic region. We tested two alternative scenarios: (a) intra‐Antarctic panmixia and (b) intra‐Antarctic genetic differentiation. Furthermore, we tested for evidence of the existence of specific intra‐Antarctic dispersal routes. Sixty‐seven new samples (40 collected in Antarctica) were sequenced for ITS nrDNA and rps4 cpDNA regions, and phylogenetic trees of B. argenteum were constructed, with a focus on its Southern Hemisphere. Combining our new nrDNA dataset with previously published datasets, we estimated time‐calibrated phylogenies based on two different substitution rates (derived from angiosperms and bryophytes) along with ancestral area estimations. Minimum spanning network and pairwise genetic distances were also calculated. B. argenteum was potentially distributed across Africa and Antarctica soon after its origin. Its earliest intra‐Antarctic dispersal and diversification occurred during a warming period in the Pliocene. On the same timescale, a radiation took place involving a dispersal event from Antarctica to the sub‐Antarctic islands. A more recent event of dispersal and diversification within Antarctica occurred during a warm period in the Pleistocene, creating favorable conditions also for its colonization outside the Antarctic continent worldwide. We provide evidence supporting the hypothesis that contemporary populations of B. argenteum in Antarctica integrate a history of both multiple long‐range dispersal events and local persistence combined with in situ diversification. Our data support the hypothesis that B. argenteum has been characterized by strong connectivity within Antarctica, suggesting the existence of intra‐Antarctic dispersal routes.
Aim
Antarctica's remote and extreme terrestrial environments are inhabited by only two species of native vascular plants. We assessed genetic connectivity amongst Antarctic and South American populations of one of these species, Colobanthus quitensis, to determine its origin and age in Antarctica.
Location
Maritime Antarctic, sub‐Antarctic islands, South America.
Taxon
Antarctic pearlwort Colobanthus quitensis (Caryophyllaceae).
Methods
Four chloroplast markers and one nuclear marker were sequenced from 270 samples from a latitudinal transect spanning 21–68° S. Phylogeographic, population genetic and molecular dating analyses were used to assess the demographic history of C. quitensis and the age of the species in Antarctica.
Results
Maritime Antarctic populations consisted of two different haplotype clusters, occupying the northern and southern Maritime Antarctic. Molecular dating analyses suggested C. quitensis to be a young (<1 Ma) species, with contemporary population structure derived since the late‐Pleistocene.
Main conclusions
The Maritime Antarctic populations likely derived from two independent, late‐Pleistocene dispersal events. Both clusters shared haplotypes with sub‐Antarctic South Georgia, suggesting higher connectivity across the Southern Ocean than previously thought. The overall findings of multiple colonization events by a vascular plant species to Antarctica, and the recent timing of these events, are of significance with respect to future colonizations of the Antarctic Peninsula by vascular plants, particularly with predicted increases in ice‐free land in this area. This study fills a significant gap in our knowledge of the age of the contemporary Antarctic terrestrial biota. Adding to previous inferences on the other Antarctic vascular plant species (the grass Deschampsia antarctica), we suggest that both angiosperm species are likely to have arrived on a recent (late‐Pleistocene) time‐scale. While most major groups of Antarctic terrestrial biota include examples of much longer‐term Antarctic persistence, the vascular flora stands out as the first identified terrestrial group that appears to be of recent origin.
Antarctic and Subantarctic lakes are unique ecosystems with relatively simple food webs, which are likely to be strongly affected by climate warming. While Antarctic freshwater invertebrates are adapted to extreme environmental conditions, little is known about the factors determining their current distribution and to what extent this is explained by biogeography or climate. We explored the distribution of freshwater crustaceans (one of the most abundant and diverse group of organisms in Antarctic and Subantarctic lakes) across four biogeographic provinces (Continental Antarctic, CA; Maritime Antarctic, MA; Subantarctic islands, SA; and Southern Cool Temperate, SCT) based on the literature, predicting that species distribution would be determined by biogeography, spatial autocorrelation among regions (in relation to dispersal) and climate. We found that variation in species composition was largely explained by the joint effect of spatial autocorrelation and climate, with little effect of biogeography – only regions within the SA province had a clearly distinct species composition. This highlights a plausible main influence of crustacean dispersal – mainly through migratory seabirds – and suggests that some regions will be more affected by climate warming than others, possibly in relation to the existence of nearby sources of colonists.
A decrease in biodiversity and density of terrestrial organisms with increasing altitude and latitude is a well-known ecogeographical pattern. However, studies of these trends are often taxonomically-biased toward well-known organisms and especially those with relatively large bodies, and environmental variability at the local scale may perturb these general effects. Here, we focus on understudied organisms—soil invertebrates—in Antarctic deserts, which are among the driest and coldest places on Earth. We sampled two remote Antarctic sites in the Darwin Glacier area and established an altitudinal gradient running from 210 to 836 m a.s.l. We measured soil geochemistry and organic matter content and linked these parameters with the presence of soil invertebrates. We found three general outcomes, two of which are consistent with general assumptions: (a) the hostile climatic condition of the Darwin Glacier region supports an extremely low diversity of soil metazoans represented by a
single nematode species—Scottnema lindsayae; (b) soil geochemistry is the main factor influencing distribution of nematodes at the local scale. Contrary to our expectations, a positive correlation was found between nematode density and altitude. This last observation could be explained by an additional effect of soil moisture as we found this increased with altitude and may be caused by orographic clouds, which are present in this region. To the best of our knowledge
such effects have been described in tropical and temperate regions. Potential effect of orographic clouds on soil properties in polar deserts may be a fruitful area of ecological research on soil fauna.
Seven species of springtail (Collembola) are present in Victoria Land, Antarctica and all have now been sequenced at the DNA barcoding region of the mitochondrial cytochrome c oxidase subunit I gene (COI). Here, we review these sequence data (n = 930) from the GenBank and Barcode of Life Datasystems (BOLD) online databases and provide additional, previously unpublished sequences (n = 392) to assess the geographic distribution of COI variants across all species. Four species (Kaylathalia klovstadi, Cryptopygus cisantarcticus, Friesea grisea, and Cryptopygus terranovus) are restricted to northern Victoria Land and three (Antarcticinella monoculata, Cryptopygus nivicolus, and Gomphiocephalus hodgsoni) are found only in southern Victoria Land, the two biogeographic zones which are separated by the vicinity of the Drygalski Ice Tongue. We found highly divergent lineages within all seven species (range 1.7–14.7%) corresponding to different geographic locations. Levels of genetic divergence for the southern Victoria Land species G. hodgsoni, the most widespread species (~27,000 km2), ranged from 5.9 to 7.3% divergence at sites located within 30 km, but separated by glaciers. We also found that the spatial patterns of genetic divergence differed between species. For example, levels of divergence were much higher for C. terranovus (>10%) than for F. grisea (<0.2%) that had been collected from the same sites in northern Victoria Land. Glaciers have been suggested to be major barriers to dispersal and two species (C. cisantarcticus and F. grisea) showed highly divergent (>5%) populations and over 87% of the total genetic variation (based on AMOVA) on either side of a single, 16 km width glacier. Collectively, these data provide evidence for limited dispersal opportunities among populations of springtails due to geological and glaciological barriers (e.g., glaciers and ice tongues). Some locations harbored highly genetically divergent populations and these areas are highlighted from a conservation perspective such as avoidance of human-mediated transport between sites. We conclude that species-specific spatial and temporal scales need to be considered when addressing ecological and physiological questions as well as conservation strategies for Antarctic Collembola.
Construction and operation of research stations present the most pronounced human impacts on the Antarctic continent across a wide range of environmental values. Despite Antarctic Treaty Parties committing themselves to comprehensive protection of the environment, data on the spatial extent of impacts from their activities have been limited. To quantify this, we examined the area of building and ground disturbance across the entire continent using geographic information system mapping of satellite imagery. Here, we report the footprint of all buildings to be >390,000 m ² , with an additional disturbance footprint of >5,200,000 m ² just on ice-free land. These create a visual footprint similar in size to the total ice-free area of Antarctica, and impact over half of all large coastal ice-free areas. Our data demonstrate that human impacts are disproportionately concentrated in some of the most sensitive environments, with consequential implications for conservation management. This high-resolution measurement of the extent of infrastructure across the continent can be used to inform management decisions to balance sustainable scientific use and environmental protection of the Antarctic environment. © 2019, The Author(s), under exclusive licence to Springer Nature Limited.
Snow algae are found in snowfields across cold regions of the planet, forming highly visible red and green patches below and on the snow surface. In Antarctica, they contribute significantly to terrestrial net primary productivity due to the paucity of land plants, but our knowledge of these communities is limited. Here we provide the first description of the metabolic and species diversity of green and red snow algae communities from four locations in Ryder Bay (Adelaide Island, 68°S), Antarctic Peninsula.
During the 2015 austral summer season, we collected samples to measure the metabolic composition of snow algae communities and determined the species composition of these communities using metabarcoding.
Green communities were protein‐rich, had a high chlorophyll content and contained many metabolites associated with nitrogen and amino acid metabolism. Red communities had a higher carotenoid content and contained more metabolites associated with carbohydrate and fatty acid metabolism. Chloromonas, Chlamydomonas and Chlorella were found in green blooms but only Chloromonas was detected in red blooms. Both communities also contained bacteria, protists and fungi.
These data show the complexity and variation within snow algae communities in Antarctica and provide initial insights into the contribution they make to ecosystem functioning.
About 400 subglacial lakes are known from Antarctica. The question of whether life unique of subglacial lakes exists has been paramount since their discovery. Despite frequent evidence of microbial life mostly from accretion ice, subglacial lakes are characterized by physiologically hostile conditions to metazoan life, as we know it. Pure water (salinity ≤0.4–1.2%), extreme cold (−3°C), high hydrostatic pressure, areas of limited or no oxygen availability and permanent darkness altogether require physiological adaptations to these harsh conditions. The record of gene sequences including some associated with hydrothermal vents does foster the idea of metazoan life in Lake Vostok. Here, we synthesize the physico-chemical environment surrounding sub-glacial lakes and potential sites of hydrothermal activity and advocate that the physico-chemical stability found at these sites may be the most likely sites for metazoan life to exist. The unique conditions presented by Lake Vostok may also offer an outlook on life to be expected in extra-terrestrial subglacial environments, such as on Jupiter's moon Europa or Saturn's moon Enceladus.
We have obtained the first data demonstrating the capability of multicellular organisms for longterm cryobiosis in permafrost deposits of the Arctic. The viable soil nematodes Panagrolaimus aff. detritophagus (Rhabditida) and Plectus aff. parvus (Plectida) were isolated from the samples of Pleistocene permafrost deposits of the Kolyma River Lowland. The duration of natural cryopreservation of the nematodes corresponds to the age of the deposits, 30 000-40 000 years.
From glacial reconstructions it is clear that Antarctic terrestrial life must have been extremely limited throughout Quaternary glacial periods. In contrast, recent biological studies provide clear evidence for long-term in situ persistence throughout glacial times within most extant Antarctic faunal and several microbial groups. However, even now, the evolutionary history of the Antarctic flora—despite playing major role in Antarctic ecosystems—remains poorly studied. We assessed the diversity, richness and relative age divergences within Schistidium (Grimmiaceae, Bryophyta), the most species-rich plant genus in the Antarctic, as well as the plant genus containing most Antarctic endemic species. We applied phylogenetic and molecular dating methods based on nuclear ribosomal Internal Transcribed Spacer sequences, including all known Antarctic Schistidium species with available sample material. We additionally investigated the continent-wide genetic diversity within the most common Antarctic representative of the genus—the endemic species Schistidium antarctici—and performed preliminary phylogeographic analyses of the bipolar species Schistidium rivulare. Most previously described Antarctic Schistidium species were genetically distinct, confirming their specific status. Interspecific divergences of all species took place at least ~1 Mya, suggesting a likely in situ persistence in Antarctica for (at least) all endemic Schistidium species. The widespread endemic species, Schistidium antarctici, diverged from other Antarctic congeners in the late Miocene, thereby revealing the oldest extant plant species currently known in Antarctica, and providing increasing support for the hypothesis of vegetation survival through multiple glacial periods. Within S. antarctici we identified several distinct clades dividing the eastern Antarctic Peninsula and Scotia Arc islands from the western Antarctic Peninsula and all continental locations. This suggests that the mountainous spine on the Antarctic Peninsula forms a strong barrier to gene flow in this species, while increased genetic diversity in the northern Maritime Antarctic indicates likely glacial refugia in this area. This study provides an important first step toward assessing the diversity and evolutionary history of the most speciose moss genus in the Antarctic. The multi-million year presence of several endemic species contributes to studies on their adaptive potential to survive climate change over both historical and contemporary timescales.
Deschampsia antarctica is the only grass naturally occurring in Antarctica, and it is also indigenous to southern South America. We aimed to evaluate patterns of within-population genetic diversity and between the focal areas Patagonia and Antarctica by using 144 sequences of nuclear internal transcribed spacer and non-coding plastid regions. We analysed phylogenetic relationships between these two main areas and performed demographic and landscape analysis. To test the divergence time between Antarctic and Patagonian populations we used approximate Bayesian computation. We found 17 nuclear and eight plastid haplotypes. For both molecular markers, Patagonia was the most genetically variable area in the range of D. antarctica. The divergence time between populations from Antarctica and Patagonia was dated to the mid to late Pleistocene. The large number of private haplotypes found in Patagonia and the great genetic variability support the hypothesis of a South American origin of the Antarctic populations of D. antarctica. Finally, we suggest that D. antarctica probably survived the Last Glacial Maximum and possibly earlier glaciations in ice-free refugia in Patagonia and Antarctica. Dispersal to Antarctica possibly occurred in the mid to late Pleistocene through bird-aided long-distance transport from South America.
In the present paper, we compare how the kelp gull, Larus dominicanus, utilizes various nest building materials, particularly vascular plants, bryophytes, lichens and other components, in the Fildes Peninsula area (King George Island) and on the Argentine Islands area. In both areas, nest material primarily consisted of the Antarctic hairgrass (Deschampsia antarctica), bryophytes, lichens, feathers, limpets, and algae. Our study reveals area-specific differences in the utilization of plants for nest building related to local conditions during the nesting season. In the Fildes area, vegetation emerges from under the winter snow cover earlier in the spring, giving the gulls greater choice locally, meaning that the gulls need not resort to long distance material transfer. Here, mosses and lichens dominate in the nest material, likely collected from the nearby vegetation formations. The Antarctic hairgrass in these conditions is mostly found in nests located directly within hairgrass formations. However, on the more southern Argentine Islands, kelp gulls routinely use D. antarctica and some mosses, transferring them from coastal hill tops where snow generally disappears earlier. Here, the gulls appear to be selective still, as they rarely use some mosses, such as Polytrichum strictum, that are abundant near the nesting locations. In the Argentine Islands area, we documented long-range transfer of the Antarctic hairgrass and some other vegetation materials from places of abundance to bare rocks of low islands lacking developed vegetation. This demonstrates the potential of the gulls to serve as dispersal and gene pool exchange agents for the local terrestrial biota in the maritime Antarctic, especially between highly isolated populations from small islands and ice-free areas.
The Antarctic–South American bank-forming moss Chorisodontium aciphyllum is known for having the oldest sub-fossils of any extant plant in Antarctica as well as extreme survival abilities, making it a candidate species for possible long-term survival in Antarctica. Applying phylogeographic and population genetic methods using the plastid markers trnL-F and rps4 and the nuclear internal transcribed spacer, we investigated the genetic diversity within C. aciphyllum throughout its range. Low genetic variation was found in all loci, both between and within Antarctic and southern South American populations, suggesting a relatively recent (likely within the last million years) colonization of this moss to the Antarctic, as well as a likely severe bottleneck during Pleistocene glaciations in southern South America. We also performed a simple atmospheric transfer modeling approach to study potential colonization rates of small (microscopic/microbial) or spore-dispersed organisms (such as many mosses and lichens). These suggested that the northern Antarctic Peninsula shows potentially regular connectivity from southern South America, with air masses transferring, particularly southbound, between the two regions. We found elevated genetic variation of C. aciphyllum in Elephant Island, also the location of the oldest known moss banks (> 5500 years), suggesting this location to be a genetic hotspot for this species in the Antarctic.
A bipolar disjunction is an extreme, yet common,
biogeographic pattern in non-vascular plants, yet its
underlyingmechanisms (vicariance or long-distance dispersal),
origin and timing remain poorly understood. Here, combining
a large-scale population dataset and multiple dating analyses,
we examine the biogeography of four bipolar Polytrichales
mosses, common to the Holarctic (temperate and polar
Northern Hemisphere regions) and the Antarctic region
(Antarctic, sub-Antarctic, southern South America) and
other Southern Hemisphere (SH) regions. Our data reveal
contrasting patterns, for three species were of Holarctic origin,
with subsequent dispersal to the SH, while one, currently
a particularly common species in the Holarctic (Polytrichum
juniperinum), diversified in the Antarctic region and from
here colonized both the Holarctic and other SH regions. Our
findings suggest long-distance dispersal as the driver of bipolar
disjunctions. We find such inter-hemispheric dispersals are
rare, occurring on multi-million-year timescales. High-altitude
tropical populations did not act as trans-equatorial ‘steppingstones’,
but rather were derived from later dispersal events. All
arrivals to the Antarctic region occurred well before the Last
Glacial Maximum and previous glaciations, suggesting that,
despite the harsh climate during these past glacial maxima,
plants have had a much longer presence in this southern region
than previously thought.
Cryptobiosis is a reversible ametabolic state of life characterized by the ceasing of all metabolic processes, allowing survival of periods of intense adverse conditions. Here we show that 1) entire moss individuals, dated by ¹⁴C, survived through cryptobiosis during six centuries of cold-based glacier burial in Antarctica, 2) after re-exposure due to glacier retreat, instead of dying (due to high rates of respiration supporting repair processes), at least some of these mosses were able to return to a metabolically active state and remain alive. Moss survival was assessed through growth experiments and, for the first time, through vitality measurements. Future investigations on the genetic pathways involved in cryptobiosis and the subsequent recovery mechanisms will provide key information on their applicability to other systematic groups, with implications for fields as divergent as medicine, biodiversity conservation, agriculture and space exploration.
Subglacial environments are known to harbour
metabolically diverse microbial communities. These microbial communities
drive chemical weathering of underlying bedrock and influence the
geochemistry of glacial meltwater. Despite its importance in weathering
reactions, the microbial cycling of iron in subglacial environments, in
particular the role of microbial iron reduction, is poorly understood. In
this study we address the prevalence of viable iron-reducing microorganisms
in subglacial sediments from five geographically isolated glaciers.
Iron-reducing enrichment cultures were established with sediment from
beneath Engabreen (Norway), Finsterwalderbreen (Svalbard), Leverett and
Russell glaciers (Greenland), and Lower Wright Glacier (Antarctica). Rates of
iron reduction were higher at 4 °C compared with 15 °C
in all but one duplicated second-generation enrichment culture, indicative
of cold-tolerant and perhaps cold-adapted iron reducers. Analysis of
bacterial 16S rRNA genes indicates Desulfosporosinus were the
dominant iron-reducing microorganisms in low-temperature Engabreen,
Finsterwalderbreen and Lower Wright Glacier enrichments, and
Geobacter dominated in Russell and Leverett enrichments. Results
from this study suggest microbial iron reduction is widespread in subglacial
environments and may have important implications for global biogeochemical
iron cycling and export to marine ecosystems.
Historical views have characterized Antarctica as a frozen desert with low diversity, although recent studies suggest that this may not be true for microscopic organisms. For microbes, assessing endemism in the Antarctic region has been particularly important, especially against a backdrop of debate regarding their presumed cosmopolitan nature. To contribute to this conversation, we highlight the observed endemism of the freshwater diatom genus Luticola in Antarctica by synthesizing the results of a modern high-resolution taxonomy from the Continental, Maritime, and sub-Antarctic regions. We report that Luticola has one of the highest endemic rates of any diatom genus in Antarctica, in terms of total number of species (taxon endemism) and percentage of the entire genus (phylogenetic endemism). Of the over 200 species of Luticola globally, nearly 20% (43) occur in the Antarctic, with 42 of these being endemic. Within regions, Maritime Antarctica has the largest number of Luticola species and endemics (28 and 23, respectively), followed by Continental Antarctica (14, 9) and sub-Antarctic islands (8, 6). Thus, 38 of the 42 endemics are found in a single region only. While the timing of Luticola diversification has not been established, fossil evidence suggests recent invasions and/or diversification over a relatively short geologic timescale. Understanding the origin and evolution of endemic diatom species in Antarctica will help us better understand microbial biogeography, as well as assess and interpret impacts of large-scale environmental change taking place at southern latitudes.
Previous work focused on allozymes and mitochondrial haplotypes has detected high levels of genetic variability between Cryptopygus terranovus populations, a springtail species endemic to Antarctica, until recently named Gressittacantha terranova . This study expands these biogeographical surveys using additional analytical techniques, providing a denser haplotype dataset and a wider sampling of localities. Specimens were collected from 11 sites across Victoria Land and sequenced for the cytochrome c oxidase subunit I mitochondrial gene ( cox1 ). Haplotypes were used for population genetics, demographic, molecular clock and Bayesian phylogenetic analyses. Landscape distribution and clustering of haplotypes were also examined for the first time in this species. Only three (out of 67) haplotypes are shared among populations, suggesting high genetic structure and limited gene flow between sites. As in previous studies, the population of Apostrophe Island has a closer genetic similarity with those of the central sites, rather than with its neighbours. Molecular clock estimates point to early differentiation of haplotypes in the late/mid-Miocene, also supporting the view that C. terranovus is a relict species that survived on the Antarctic continent during the Last Glacial Maximum. The present genetic composition of populations represents a mixture of ancient and more recent haplotypes, sometimes occurring in the same localities.
We present Bedmap2, a new suite of gridded products describing surface elevation, ice-thickness and the seafloor and subglacial bed elevation of the Antarctic south of 60° S. We derived these products using data from a variety of sources, including many substantial surveys completed since the original Bedmap compilation (Bedmap1) in 2001. In particular, the Bedmap2 ice thickness grid is made from 25 million measurements, over two orders of magnitude more than were used in Bedmap1. In most parts of Antarctica the subglacial landscape is visible in much greater detail than was previously available and the improved data-coverage has in many areas revealed the full scale of mountain ranges, valleys, basins and troughs, only fragments of which were previously indicated in local surveys. The derived statistics for Bedmap2 show that the volume of ice contained in the Antarctic ice sheet (27 million km<sup>3</sup>) and its potential contribution to sea-level rise (58 m) are similar to those of Bedmap1, but the mean thickness of the ice sheet is 4.6% greater, the mean depth of the bed beneath the grounded ice sheet is 72 m lower and the area of ice sheet grounded on bed below sea level is increased by 10%. The Bedmap2 compilation highlights several areas beneath the ice sheet where the bed elevation is substantially lower than the deepest bed indicated by Bedmap1. These products, along with grids of data coverage and uncertainty, provide new opportunities for detailed modelling of the past and future evolution of the Antarctic ice sheets.
As the accuracy and sensitivity of remote-sensing satellites improve, there is an increasing demand for more accurate and updated base datasets for surveying and monitoring. However, differentiating rock outcrop from snow and ice is a particular problem in Antarctica, where extensive cloud cover and widespread shaded regions lead to classification errors. The existing rock outcrop dataset has significant georeferencing issues as well as overestimation and generalisation of rock exposure areas. The most commonly used method for automated rock and snow differentiation, the normalised difference snow index (NDSI), has difficulty differentiating rock and snow in Antarctica due to misclassification of shaded pixels and is not able to differentiate illuminated rock from clouds. This study presents a new method for identifying rock exposures using Landsat 8 data. This is the first automated methodology for snow and rock differentiation that excludes areas of snow (both illuminated and shaded), clouds and liquid water whilst identifying both sunlit and shaded rock, achieving higher and more consistent accuracies than alternative data and methods such as the NDSI. The new methodology has been applied to the whole Antarctic continent (north of 82°40′ S) using Landsat 8 data to produce a new rock outcrop dataset for Antarctica. The new data (merged with existing data where Landsat 8 tiles are unavailable; most extensively south of 82°40′ S) reveal that exposed rock forms 0.18 % (21 745 km2) of the total land area of Antarctica: half of previous estimates.
Although most models suggest continental Antarctica was covered by ice during the Last Glacial Maximum (LGM) it has been speculated that endemic species of soil invertebrates could have survived the Pleistocene at high elevation habitats protruding above the ice sheets. We analyzed a series of soil samples from different elevations at three locations along the Beardmore Glacier in the Transantarctic Mountains (in order of increasing elevation): Ebony Ridge (ER), Cloudmaker (CM), and Meyer Desert (MD). Geochemical analyses show the MD soils, which were exposed during the LGM, were the least weathered compared to lower elevations, and also had the highest total dissolved solids (TDS). MD soils are dominated by nitrate salts (NO3/Cl ratios >10) that can be observed in SEM images. High δ17O and δ18O values of the nitrate indicate that its source is solely of atmospheric origin. It is suggested that nitrate concentrations in the soil may be utilized to determine a relative “wetting age” to better assess invertebrate habitat suitability. The highest elevation sites at MD have been exposed and accumulating salts for the longest times, and because of the salt accumulations, they were not suitable as invertebrate refugia during the LGM.
Climate changes are likely to have major influences on the distribution and abundance of Antarctic terrestrial biota. To assess arthropod distribution and diversity within the Ross Sea region, we examined mitochondrial DNA (COI) sequences for three currently recognized species of springtail (Collembola) collected from sites in the vicinity, and to the north of, the Mackay Glacier (77°S). This area acts as a transition between two biogeographic regions (northern and southern Victoria Land). We found populations of highly divergent individuals (5%-11.3% intraspecific sequence divergence) for each of the three putative springtail species, suggesting the possibility of cryptic diversity. Based on molecular clock estimates, these divergent lineages are likely to have been isolated for 3-5 million years. It was during this time that the Western Antarctic Ice Sheet (WAIS) was likely to have completely collapsed, potentially facilitating springtail dispersal via rafting on running waters and open seaways. The reformation of the WAIS would have isolated newly established populations, with subsequent dispersal restricted by glaciers and ice-covered areas. Given the currently limited distributions for these genetically divergent populations, any future changes in species' distributions can be easily tracked through the DNA barcoding of springtails from within the Mackay Glacier ecotone.
We examined levels of genetic variability within and among populations of three Antarctic springtail species (Arthropoda: Collembola) and tested the hypothesis that genetic divergences occur among glacially-isolated habitats. The study was conducted in southern Victoria Land, Ross Dependency, Antarctica, and samples were collected from locations in the vicinity of the Mackay Glacier. We analyzed mtDNA (cytochrome c oxidase subunit I; COI) sequence variability for 97 individuals representing three species (Gomphiocephalus hodgsoni, N = 67; Cryptopygus nivicolus, N = 20; and Antarcticinella monoculata, N = 8). Haplotype diversity and genetic divergences were calculated and used to indicate population variability and also to infer divergence times of isolated populations using molecular clock estimates. Two of the three species showed high levels of genetic divergence. Gomphiocephalus hodgsoni, a widespread and common species, showed 7.6% sequence divergence on opposite sides of the Mackay Glacier. The more range restricted C. nivicolus showed 4.0% divergence among populations. The third species, A. monoculata, was found in only one location. Molecular clock estimates based on sequence divergences suggest that populations separated within the last 4 Mya. We conclude that habitat fragmentation resulting from Pliocene (5 Mya) and Pleistocene (2 Mya to 10 Kya) glaciations has promoted and maintained high levels of diversity among isolated springtail populations on relatively small spatial scales. The region surrounding the Mackay Glacier is likely to have provided refugia for springtail populations during glacial maxima and remains an area of high genetic and species diversity for Collembola within the Ross Sea region.
Glaciers are rather unusual habitat for mosses, but sometimes they can be suitable for some species due to presence of sufficient moisture and cryoconite substrate in the ablation zone. To date, moss populations were found only on a few glaciers in Alaska, Iceland and Svalbard. An origin and development of moss cushions on ice (so called "glacier mice") are still unclear. In this study, some aspects of the moss population development were explored on ice of the Svalbard glaciers - Bertilbreen (Billefjorden) and Austre Grønfjordbreen (Grønfjorden) in 2012 and 2013. On Bertilbreen, populations of Hygrohypnella polaris (Lindb.) Ignatov & Ignatova and Schistidium abrupticostatum (Bryhn) Ignatova & H.H. Blom were found for the first time. Due to putative morphological features, identification of S. abrupticostatum was confirmed by comparing ITS1-2 nrDNA sequence data to BLAST searches (megablast). The results indicated a genetic heterogeneity of the population. Although visually moss-free, examination of cryoconite sediments revealed development of new individuals of S. abrupticostatum from filamentous structures consisting of caulonema and rhizoids. The developmental stages of young plants were revealed. Therefore, besides fragmentation of existing cushions, cryoconite sediments provided a source of new moss cushions in glacier populations. Additionally a few plants of Pohlia cf. wahlenbergii (F. Weber & D. Mohr) Andrews and a gametophyte fragment of Philonotis sp. were found in aggregation of cryoconite. Presence of Paludella squarrosa (Hedw.) Brid. reported for Bertilbreen has not been confirmed. On Austre Grønfjordbreen Bryum cryophilum Mårtensson, Sanionia uncinata (Hedw.) Loeske were found invading into some Hygrohypnella polaris cushions. Each moss polster on ice represents a separate miniecosystem that includes successive colonization events.
The genus Maudheimia Dalenius, 1958 occurs on the Antarctic continent and contains four known species (M. wilsoni Dalenius, 1958; M. petronia Wallwork, 1962; M. marshalli Coetzee, 1997 and M. tanngardenensis Coetzee, 1997). Maudheimia marshalli has 15 pairs of notogastral setae in the adults for which Subías (2004) proposed the genus Multimaudheimia. The other three species have 10 pairs of notogastral setae in the adult stage. The value of "number of notogastral setae" as a single generic character has previously been shown as insufficient to distinguish a genus. The authors conclude that the genus Multimaudheimia Subías, 2004 is a synonym of Maudheimia. The relationship of Maudheimia is confirmed as a member of Ceratozetoidea in the family Maudheimiidae.
Antarctica is an isolated continent whose conditions challenge the survival of living organisms. High levels of endemism are now known in many Antarctic organisms, including algae, tardigrades, nematodes and microarthropods. Bdelloid rotifers are a key, widespread and abundant group of Antarctic microscopic invertebrates. However, their diversity, regional distribution and endemism have received little attention until recently. We provide the first authoritative review on Antarctic Bdelloidea, based on published data and new collections. Our analysis reveals the extreme levels of bdelloid endemism in Antarctica. Sixty-six bdelloid morphospecies are now confirmed from the continent, and 83–91 putative species are identified using molecular approaches (depending on the delimitation method used). Twelve previously unknown species are described based on both morphology and molecular analyses. Molecular analyses indicate that only two putative species found in Antarctica proved to be truly cosmopolitan. The level of endemism based on the available data set (95%) is higher than that in any other continent, with many bdelloid species occurring only in maritime or continental Antarctica. These findings are consistent with the long-term presence of Bdelloidea in Antarctica, with their considerable isolation facilitating intraregional radiation, providing further evidence
that does not support the microbial global ubiquity hypothesis that ‘‘everything is everywhere.’’
Recent advances in knowledge of patterns of biogeography in terrestrial eukaryotic organisms have led to a fundamental paradigm shift in understanding of the controls and history of life on land in Antarctica, and its interactions over the long term with the glaciological and geological processes that have shaped the continent. However, while it has long been recognized that the terrestrial ecosystems of Antarctica are dominated by microbes and their processes, knowledge of microbial diversity and distributions has lagged far behind that of the macroscopic eukaryote organisms. Increasing human contact with and activity in the continent is leading to risks of biological contamination and change in a region whose isolation has protected it for millions of years at least; these risks may be particularly acute for microbial communities which have, as yet, received scant recognition and attention. Even a matter apparently as straightforward as Protected Area designation in Antarctica requires robust biodiversity data which, in most parts of the continent, remain almost completely unavailable. A range of important contributing factors mean that it is now timely to reconsider the state of knowledge of Antarctic terrestrial prokaryotes. Rapid advances in molecular biological approaches are increasingly demonstrating that bacterial diversity in Antarctica may be far greater than previously thought, and that there is overlap in the environmental controls affecting both Antarctic prokaryotic and eukaryotic communities. Bacterial dispersal mechanisms and colonization patterns remain largely unaddressed, although evidence for regional evolutionary differentiation is rapidly accruing and, with this, there is increasing appreciation of patterns in regional bacterial biogeography in this large part of the globe. In this review, we set out to describe the state of knowledge of Antarctic prokaryote diversity patterns, drawing analogy with those of eukaryote groups where appropriate.
Until recently the Antarctic continent and Peninsula have been little impacted
by non-native species, compared to other regions of the Earth. However, reports of species
introductions are increasing as awareness of biological invasions as a major conservation
threat, within the context of increased human activities and climate change scenarios, has
grown within the Antarctic community. Given the recent increase in documented reports,
here we provide an up-to-date inventory of known terrestrial non-native species introductions,
including those subsequently removed since the 1990s, within the Antarctic
Treaty area. This builds on earlier syntheses of records published in the mid-2000s, which
focused largely on the sub-Antarctic islands, given the dearth of literature available at that
time from the continental and maritime Antarctic regions. Reports of non-native species
established in the natural environment (i.e. non-synanthropic) are mainly located within the
Antarctic Peninsula region and Scotia Arc, with Deception Island, South Shetland Islands,
the most impacted area. Non-native plants have generally been removed from sites of
introduction, but no established invertebrates have yet been subject to any eradication
attempt, despite a recent increase in reports. Legislation within the Protocol on Environmental Protection to the Antarctic Treaty has not kept pace with environmental
best practice, potentially presenting difficulties for the practical aspects of non-native
species control and eradication. The success of any eradication attempt may be affected by
management practices and the biology of the target species under polar conditions.
Practical management action is only likely to succeed with greater co-operation and improved
communication and engagement by nations and industries operating in the region.
Since the first descriptions of Antarctic subglacial lakes, there has been a growing interest and awareness of the possibility that life will exist and potentially thrive in these unique and little known environments. The unusual combination of selection pressures, and isolation from the rest of the biosphere, might have led to novel adaptations and physiology not seen before, or indeed to the potential discovery of relic populations that may have become extinct elsewhere. Here we report the first microbiological analysis of a sample taken from a former subglacial lake sediment in Antarctica (Lake Hodgson, on the Antarctic Peninsula). This is one of a number of subglacial lakes just emerging at the margins of the Antarctic ice sheet due to the renewed onset of deglaciation. Microbial diversity was divided into 23.8% Actinobacteria, 21.6% Proteobacteria, 20.2% Planctomycetes and 11.6% Chloroflexi, characteristic of a range of habitat types ( Overall, common sequences were neither distinctly polar, low temperature, freshwater nor marine). Twenty three percent of this diversity could only be identified to "unidentified bacterium". Clearly these are diverse ecosystems with enormous potential.
Analyses of a core from the deepest known moss peat bank in Antarctica, on Elephant Island, South Shetlands, show that this Chorisodontium aciphyllum-dominated bank began to grow ca. 5500 14C yr BP. Combined with other studies in the region the present study indicates more extensive glaciation before 5000 to 6000 BP than today on some of the South Shetland Islands. The main hypothesis is that these frozen moss banks contain important paleoclimatic information. The stratigraphic parameters analyzed included degree of humification, organic and mineral matter content, bulk density, chronology, volumetric growth and organic accumulation rates, carbon and nitrogen concentrations, C/N ratios, nitrogen accumulation rates, and finally magnetic analyses to detect tephra horizons. A discussion of the interrelationships between these parameters is followed by theoretical calculations of annual net primary productivity combined with multivariate analysis of the data set. Results of the analysis show that three calculated productivity peaks coincide with three periods of milder and more humid summers, at 4150-3900, 3180-3030, and 2030-1840 BP. However, the period with possibly the warmest summers, 3180-3030 BP, is interpreted also to have been characterized by cold winters. The data suggest that the periods with the coldest summers (and possibly also winters) prevailed at the earliest stage of the moss bank development, at ca. 3500 BP, and 2500 BP.
Antarctica is isolated, surrounded by the Southern Ocean, and has experienced extreme environmental conditions for millions of years, including during recent Pleistocene glacial maxima. How Antarctic terrestrial species might have survived these glaciations has been a topic of intense interest, yet many questions remain unanswered, particularly for Antarctica’s invertebrate fauna. We examine whether genetic data from a widespread group of terrestrial invertebrates, springtails (Collembola, Isotomidae) of the genus Cryptopygus, show evidence for long‐term survival in glacial refugia along the Antarctic Peninsula. We use genome‐wide SNP analyses (via genotyping‐by‐sequencing, GBS) and mitochondrial data to examine population diversity and differentiation across more than 20 sites spanning >950 km on the Peninsula, and from islands both close to the Peninsula and up to ~1,900 km away. Population structure analysis indicates the presence of strong local clusters of diversity, and we infer that patterns represent a complex interplay of isolation in local refugia coupled with occasional successful long‐distance dispersal events. We identified wind and degree days as significant environmental drivers of genetic diversity, with windier and warmer sites hosting higher diversity. Thus, we infer that refugial areas along the Antarctic Peninsula have allowed populations of indigenous springtails to survive in situ throughout glacial periods. Despite the difficulties of dispersal in cold, desiccating conditions, Cryptopygus springtails on the Peninsula appear to have achieved multiple long‐distance colonisation events, most likely through wind‐related dispersal events.
The surprise discovery of ancient crustaceans and a tardigrade emerged from a rare mission to drill into a lake sealed off by a kilometre of ice.
The metazoan fauna of Antarctic and sub-Antarctic freshwaters is reviewed. Almost 400 species, notably rotifers, tardigrades and crustaceans have been identified. Sponges, molluscs, amphibians, reptiles and fishes are absent though salmonid fishes have been successfully introduced on some of the sub-Antarctic islands. Other alien introductions include insects (Chironomidae) and annelid worms (Oligochaeta). The fauna is predominately benthic in habitat and becomes increasingly depauperate at higher latitudes. Endemic species are known but only a few are widely distributed. Planktonic species are rare and only one parasitic species has been noted.
Mitochondrial and nuclear sequence data from two Antarctic ameronothroid mites, Halozetes belgicae and Alaskozetes antarcticus , were used to address three key questions important for understanding both the evolution of biodiversity and its future conservation in the Antarctic Peninsula Region: i) Do populations of mites across the Antarctic Peninsula and Scotia Arc constitute distinct genetic lineages? ii) What implications does the spatial genetic structure in these species have for current understanding of the region’s glacial history? iii) What are the conservation implications of these findings? Our results indicate that both mite species have been present in the Antarctic since at least the Pliocene. At the regional scale, both species are comprised of a number of divergent, but sympatric, lineages that are genetically as distinct as some species within the genera Halozetes and Alaskozetes . At the local scale, complex structure suggests limited and stochastic post-Holocene dispersal. For both species, considerable spatial genetic structure exists across the region, similar to that found in other terrestrial invertebrates. These results support the implementation of stringent biosecurity measures for moving between the Scotia Arc islands and the Antarctic Peninsula, and throughout the latter, to conserve both evolutionary history and future evolutionary trajectories.
PREMISE OF THE STUDY: American bipolar plant distributions characterize taxa at various taxonomic ranks but are most common in the bryophytes at infraspecific and infrageneric levels. A previous study on the bipolar disjunction in the dung moss genus Tetraplodon found that direct long-distance dispersal from North to South in the Miocene–Pleistocene accounted for the origin of the Southern American endemic Tetraplodon fuegianus, congruent with other molecular studies on bipolar bryophytes. The previous study, however, remained inconclusive regarding a specifi c northern hemisphere source region for the transequatorial dispersal event that gave rise to T. fuegianus.
METHODS: To estimate spatial genetic structure and phylogeographic relationships within the bipolar lineage of Tetraplodon, which includes T. fuegianus, we analyzed thousands of restriction-site-associated DNA (RADseq) loci and single nucleotide polymorphisms using Bayesian individual assignment and maximum likelihood and coalescent model based phylogenetic approaches.
KEY RESULTS: Northwestern North America is the most likely source of the recent ancestor to T. fuegianus.
CONCLUSIONS: Tetraplodon fuegianus, which marks the southernmost populations in the bipolar lineage of Tetraplodon, arose following a single longdistance dispersal event involving a T. mnioides lineage that is now rare in the northern hemisphere and potentially restricted to the Pacifi c Northwest of North America. Furthermore, gene flow between sympatric lineages of Tetraplodon mnioides in the northern hemisphere is limited, possibly due to high rates of selfing or reproductive isolation.