Chapter

Refuges of Antarctic diversity

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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.

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... 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]. ...
Article
Full-text available
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]. ...
Preprint
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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. ...
Article
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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. ...
Preprint
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). ...
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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. ...
Article
Full-text available
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). ...
Article
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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.
... Conversely, widespread endemism and molecular clock estimates indicate long-term associations of various taxa with the region, including terrestrial (e.g., mosses, mites, springtails, midges; Pisa et al., 2014;Biersma et al., 2018;Mortimer et al., 2011;van Vuuren et al., 2018;Stevens et al., 2006;McGaughran et al., 2010;McGaughran et al., 2019;Torricelli et al., 2010;Carapelli et al., 2017;Allegrucci et al., 2006;Allegrucci et al., 2012), limno-terrestrial (e.g., rotifers, tardigrades; Iakovenko et al., 2015;Short et al., 2022) and limnetic (e.g., green algae, diatoms, midges, copepods; De Wever et al., 2009;Verleyen et al., 2021;Allegrucci et al., 2006;Maturana et al., 2022). Nevertheless, despite this evidence and several proposed putative refugial areas, it remains very difficult to infer the exact locations of glacial refugia in this part of Antarctica as they may have consisted of many temporary localities connected via dispersal (Convey et al., 2020). It has been suggested that these areas could have been associated with geothermal activity (Fraser et al., 2014), or 'non-traditional' habitats such as cryoconite holes or supraglacial ponds for microorganisms such as diatoms or green algae (De Wever et al., 2009;Verleyen et al., 2021). ...
... If B. gaini inhabited the central parts of the NWAP even during the coldest phase of the last glacial period, it is possible that Antarctica harbored populations of this crustacean throughout the earlier cold phases of Pleistocene climatic oscillations, as the last glacial period was among the coldest, especially in Antarctica (Jouzel et al., 2007;Masson-Delmotte et al., 2010). As refugial areas, especially in Maritime Antarctica, were most likely temporary (Convey et al., 2020), dispersal ability was a key factor for survival. In this regard, B. gaini proved that when the conditions are met, it can colonize newly deglaciated site within centuries after its formation (e.g., Björck et al., 1996;Jones et al., 2000). ...
Article
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Branchinecta gaini Daday, 1910 is the southernmost extant Anostracan species occurring in various localities across Maritime Antarctica. Since this region was almost completely glaciated during the Last Glacial Maximum, the identification of potential glacial refugia and the colonization sequence of freshwater habitats within Maritime Antarctica remains primary biogeographic objective for understanding the evolution of the Antarctic environment. To evaluate the history of B. gaini in Maritime Antarctica, we performed phylogeographic analyses of B. gaini and its closest Patagonian congener Branchinecta granulosa Daday, 1902. We sampled 47 populations from all three Antarctic bioregions where B. gaini occurs – South Orkney Islands, North-west and North-east Antarctic Peninsula. B. granulosa was represented by 8 populations from Patagonia. Molecular analyses of two mitochondrial (16S, COI) and one nuclear (ITS2) marker showed low overall mitochondrial variability and the ambiguous nature of ITS2 variability. The species assessment revealed insufficient genetic differentiation between B. gaini and B. granulosa to consider them two separate species. Therefore, the widely accepted idea that there is a species of Branchinecta endemic to Antarctica and sub-Antarctic islands should be omitted, and B. gaini should be synonymized with B. granulosa . Molecular clock analysis of COI for two substitution rates dated the separation of B. gaini from B. granulosa to the Pleistocene (170 – 502 ka BP and 17 – 50 ka BP, respectively). Therefore, Antarctic populations of B. gaini separated from Patagonian B. granulosa before or during the Last Glacial Maximum, indicating an older association with the southern continent than previously anticipated. The geographic distribution of haplotypes further suggests that B. gaini most likely survived at least the last glacial period in an as-yet unknown refugium in Antarctica.
... It is now well known that despite these extreme conditions, the arid and hyper-arid Antarctic soils host a much higher microbial diversity than previously thought (Cowan et al., 2014;Lukashanets et al., 2021;Ortiz et al., 2021). In addition, there is cumulative evidence that similarly to macroscopic organisms, a relatively high number of microbial taxa is endemic to the Antarctic as a result of evolution in isolation on multi-million-year timescales (Convey et al., 2020;Pinseel et al., 2020;Ortiz et al., 2021;Verleyen et al., 2021;Tytgat et al., 2023). This implies that some regions must have been ice free during the multiple glacial (re-)advances that took place since the formation of the Antarctic Ice Sheets c. 35 Mya, and could act as refugia for terrestrial and lacustrine biota Pugh and Convey, 2008;Stevens and D'Haese, 2014;Convey et al., 2020;Pinseel et al., 2021). ...
... In addition, there is cumulative evidence that similarly to macroscopic organisms, a relatively high number of microbial taxa is endemic to the Antarctic as a result of evolution in isolation on multi-million-year timescales (Convey et al., 2020;Pinseel et al., 2020;Ortiz et al., 2021;Verleyen et al., 2021;Tytgat et al., 2023). This implies that some regions must have been ice free during the multiple glacial (re-)advances that took place since the formation of the Antarctic Ice Sheets c. 35 Mya, and could act as refugia for terrestrial and lacustrine biota Pugh and Convey, 2008;Stevens and D'Haese, 2014;Convey et al., 2020;Pinseel et al., 2021). ...
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Understanding the relation between terrestrial microorganisms and edaphic factors in the Antarctic can provide insights into their potential response to environmental changes. Here we examined the composition of bacterial and micro-eukaryotic communities using amplicon sequencing of rRNA genes in 105 soil samples from the Sør Rondane Mountains (East Antarctica), differing in bedrock or substrate type and associated physicochemical conditions. Although the two most widespread taxa (Acidobacteriota and Chlorophyta) were relatively abundant in each sample, multivariate analysis and co-occurrence networks revealed pronounced differences in community structure depending on substrate type. In moraine substrates, Actinomycetota and Cercozoa were the most abundant bacterial and eukaryotic phyla, whereas on gneiss, granite and marble substrates, Cyanobacteriota and Metazoa were the dominant bacterial and eukaryotic taxa. However, at lower taxonomic level, a distinct differentiation was observed within the Cyanobacteriota phylum depending on substrate type, with granite being dominated by the Nostocaceae family and marble by the Chroococcidiopsaceae family. Surprisingly, metazoans were relatively abundant according to the 18S rRNA dataset, even in samples from the most arid sites, such as moraines in Austkampane and Widerøefjellet (“Dry Valley”). Overall, our study shows that different substrate types support distinct microbial communities, and that mineral soil diversity is a major determinant of terrestrial microbial diversity in inland Antarctic nunataks and valleys.
... 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'). ...
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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). ...
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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. ...
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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.
... Over the course of millions of years, this distinct group of organisms has developed and diversified in response to a wide range of environmental stresses. Recent phylogeographic studies strongly suggests that many species within Antarctica's terrestrial biota have persisted for long periods, with estimated persistence ranging from hundreds of thousands to multi-million year timescales (Convey et al., 2008(Convey et al., , 2020Verleyen et al., 2021;Maturana et al., 2022). Conversely, a smaller number of studies have reported evidence supporting more recent mid-to post-Pleistocene colonization from lower latitudes (van de Wouw et al., 2008;Biersma et al., 2020). ...
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The terrestrial fauna of Antarctica consists of a limited number of species, notably insects, small crustaceans and other micro-invertebrates. Over long periods of evolutionary isolation, these organisms have developed varying degrees of tolerance to multifaceted environmental stresses. Recent molecular biogeographical research highlights the enduring persistence of much of Antarctica’s current terrestrial fauna, with estimates spanning from hundreds of thousands to millions of years. Parochlus steinenii, commonly known as the Antarctic winged midge, stands out as one of the only two insect species native to Antarctica. Distributed across three biogeographic regions, southern South America and the Falkland/Malvinas Islands, sub-Antarctic South Georgia and the Maritime Antarctic South Shetland Islands, this midge raises questions about the temporal isolation of its populations and their divergence. Employing mitochondrial and nuclear genetic markers, we conducted phylogeographic and demographic analyses on 151 individuals of P. steinenii obtained across the three main biogeographic regions including the Magellanic sub-Antarctic Ecoregion (MSE) of southern South America, the sub-Antarctic Island of South Georgia (SG) and the South Shetland Islands (SSI) within the Maritime Antarctic (MA). Our data support the diversification of P. steinenii during the mid-Pleistocene around 1.46 Mya. This period included a branching event between a clade containing only specimens from the MSE and a clade containing individuals from a broader range of locations including the SSI and SG. Based on intraspecific phylogeographic and demographic inferences, we detected strong evolutionary divergence between the three main biogeographic regions. We also detected a signal of population growth during the deglaciation process in SSI and SG, contrary to the pattern seen in the MSE. The different demographic and phylogeographic histories between the sampled biogeographic regions could result from the MA and SG experiencing a strong genetic bottleneck due to a reduction in population size during the Last Glacial Maximum, while the MSE maintained a significant effective population size. The high level of divergence detected between individuals from the MSE and the remaining biogeographic regions supports the hypothesis of a speciation process taking place in P. steinenii.
... Antarctica is one of the few pristine environments remaining on the planet, due to its physical isolation and extreme climatic conditions (low temperatures, lack freshwater, strong winds, short growing season and limited ice-free areas), which act as barriers to the natural colonization and establishment of organisms (Convey et al., 2014;Duffy et al., 2017;Hughes & Convey, 2010). The terrestrial biodiversity of the Antarctic continent is characterized by a high degree of endemism (Chown et al., 2015;Chown & Convey, 2007;Convey et al., 2020;Pugh & Convey, 2008) and low overall species diversity (Convey & Stevens, 2007). Mosses and lichens dominate ice-free terrestrial areas, while the invertebrate fauna is limited to small arthropods and microinvertebrates (Convey & Biersma, 2024;Hughes & Pertierra, 2016). ...
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We report the first record of the microlepidopteran Plodia interpunctella beyond the South Shetland Islands at the Chilean Yelcho scientific station (64°52′33.1428″ S; 63°35′1.9572″ W), Doumer Island, close to the west coast of the Antarctic Peninsula. It is notable that P. interpunctella , a globally distributed stored product pest species, exhibits a remarkable capacity for prolonged viability within food storage facilities. The dual challenges of food transportation and storage in the context of Antarctica's challenging operational conditions may have facilitated P. interpunctella' s initial arrival to the Antarctic region. Non‐perishable food items, such as grains, flour and rice, provide practical options for the bulk food transportation and storage required in the long‐term operation of Antarctic research stations. The presence of P. interpunctella in Antarctica, even if restricted to synanthropic environments within buildings, is a clear threat to Antarctic biodiversity, not only through being an invasive species itself but also as a potential vector for other non‐native species (bacteria, acari, between others.), which could carry diseases to the native species.
... The austral biogeographical group (13.7%) includes some species that may have originated on the old continent of Gondwana, as did many vascular plants [23,24] and bryophytes [25]. Finally, the Antarctic-subantarctic endemic group (16.9%) should be considered to be composed of pre-Pleistocene survivors of the ice ages that somehow found refuge in ice-free areas, mainly on rocky substrates in coastal regions or nunataks [23,26,27]. Interestingly, some cosmopolitan species, such as Collema tenax (Sw.) ...
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This paper analyses the lichen flora of Navarino Island (Tierra del Fuego, Cape Horn Region, Chile), identifying species shared with the South Shetland Islands (Antarctic Peninsula). In this common flora, species are grouped by their biogeographic origin (Antarctic–subantarctic endemic, austral, bipolar, and cosmopolitan), their habitat on Navarino Island (coastal, forest, and alpine), their morphotype (crustaceous, foliaceous, fruticulose, and cladonioid), and the substrate from which they were collected (epiphytic, terricolous and humicolous, and saxicolous). A total of 124 species have been recognised as common on both sides of the Drake Passage, predominantly bipolar, crustaceous, and saxicolous species, and with an alpine distribution on Navarino Island. The most interesting fact is that more than 30% of the flora is shared between the southern tip of South America and the western Antarctic Peninsula, which is an indication of the existence of a meridian flow of propagules capable of crossing the Antarctic polar front.
... 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). ...
Article
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. ...
Article
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. ...
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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). ...
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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). ...
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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. ...
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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). ...
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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. ...
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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. ...
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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. ...
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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. ...
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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. ...
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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.
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During the 2022/2023 austral winter, large swarms of Trichocera (Saltrichocera) maculipennis Meigen, 1818 (Diptera: Trichoceridae), were observed around house roofs in Puerto Williams (Navarino Island, southern Chile, 54° S). In January 2023, the presence of this species was also confirmed in Punta Arenas (53° S), with specimens collected within the Chilean Antarctic Institute warehouse facilities. Trichocera maculipennis is native to the Holarctic region and became established on King George Island (South Shetland Islands, Maritime Antarctic) over 15 years ago. However, the species has not previously been reported from South America. Taxonomic and molecular identification techniques were used to confirm the identity of the new specimens obtained from Navarino Island and Punta Arenas. Preliminary observations of the fly's habitat preferences and swarming behaviour in Puerto Williams are provided, as well as comparisons in wing morphometrics between flies from Puerto Williams and King George Island. The fly's extensive distribution and high abundance in Puerto Williams are consistent with human‐facilitated introduction and several years' establishment. These findings emphasise the importance of implementing robust management strategies and biosecurity measures, particularly during transportation between logistical hubs in southern South America and the remote areas of the Cape Horn Biosphere Reserve and Antarctica.
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The possible role of geothermal areas, such as volcanoes, in fostering biodiversity in Antarctica has received considerable recent attention. Under a geothermal refugia hypothesis, diverse life could be supported near or at geothermal sites, and we should see decreasing diversity and/or patterns of nestedness moving away from ‘hotspots’. Although there is evidence that geothermal areas have played a role in the persistence of some terrestrial species through glacial periods in Antarctica, the spatial scales at which such refugia operate is not clear. We sampled sediment from a range of locations across volcanic Deception Island in the Maritime Antarctic and used eDNA metabarcoding approaches (targeting a region of the 28S marker) to assess patterns of diversity in relation to thermal gradients. We found that although colder sites harboured significantly greater taxonomic richness than warmer sites, phylogenetic diversity was lower at colder sites (i.e. taxa at colder sites tend to be more evolutionary close to each other). We infer that increased selective processes in low-temperature environments have reduced phylogenetic diversity, supporting a hypothesis of geothermal locations acting as refugia for diverse taxa, even on fine spatial scales, in cold-climate regions such as Antarctica.
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Background Incomplete species inventories for Antarctica represent a key challenge for comprehensive ecological research and conservation in the region. Additionally, data required to understand population dynamics, rates of evolution, spatial ranges, functional traits, physiological tolerances and species interactions, all of which are fundamental to disentangle the different functional elements of Antarctic biodiversity, are mostly missing. However, much of the fauna, flora and microbiota in the emerged ice-free land of the continent have an uncertain presence and/or unresolved status, with entire biodiversity compendia of prokaryotic groups (e.g. bacteria) being missing. All the available biodiversity information requires consolidation, cross-validation, re-assessment and steady systematic inclusion in order to create a robust catalogue of biodiversity for the continent. New information We compiled, completed and revised eukaryotic species inventories present in terrestrial and freshwater ecosystems in Antarctica in a new living database: terrANTALife (version 1.0). The database includes the first integration in a compendium for many groups of eukaryotic microorganisms. We also introduce a first catalogue of amplicon sequence variants (ASVs) of prokaryotic biodiversity. Available compendia and literature to date were searched for Antarctic terrestrial and freshwater species, integrated, taxonomically harmonised and curated by experts to create comprehensive checklists of Antarctic organisms. The final inventories comprises 470 animal species (including vertebrates, free-living invertebrates and parasites), 306 plants (including all Viridiplantae: embryophytes and green algae), 997 fungal species and 434 protists (sensu lato). We also provide a first account for many groups of microorganisms, including non-lichenised fungi and multiple groups of eukaryotic unicellular species (Stramenophila, Alveolata and Rhizaria (SAR), Chromists and Amoeba), jointly referred to as "protists". In addition, we identify 1753 bacterial (obtained from 348117 ASVs) and 34 archaeal genera (from 1848 ASVs), as well as, at least, 14 virus families. We formulate a basic tree of life in Antarctica with the main lineages listed in the region and their “known-accepted-species” numbers.
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Background Antarctica and its unique biodiversity are increasingly at risk from the effects of global climate change and other human influences. A significant recent element underpinning strategies for Antarctic conservation has been the development of a system of Antarctic Conservation Biogeographic Regions (ACBRs). The datasets supporting this classification are, however, dominated by eukaryotic taxa, with contributions from the bacterial domain restricted to Actinomycetota and Cyanobacteriota. Nevertheless, the ice-free areas of the Antarctic continent and the sub-Antarctic islands are dominated in terms of diversity by bacteria. Our study aims to generate a comprehensive phylogenetic dataset of Antarctic bacteria with wide geographical coverage on the continent and sub-Antarctic islands, to investigate whether bacterial diversity and distribution is reflected in the current ACBRs. Results Soil bacterial diversity and community composition did not fully conform with the ACBR classification. Although 19% of the variability was explained by this classification, the largest differences in bacterial community composition were between the broader continental and maritime Antarctic regions, where a degree of structural overlapping within continental and maritime bacterial communities was apparent, not fully reflecting the division into separate ACBRs. Strong divergence in soil bacterial community composition was also apparent between the Antarctic/sub-Antarctic islands and the Antarctic mainland. Bacterial communities were partially shaped by bioclimatic conditions, with 28% of dominant genera showing habitat preferences connected to at least one of the bioclimatic variables included in our analyses. These genera were also reported as indicator taxa for the ACBRs. Conclusions Overall, our data indicate that the current ACBR subdivision of the Antarctic continent does not fully reflect bacterial distribution and diversity in Antarctica. We observed considerable overlap in the structure of soil bacterial communities within the maritime Antarctic region and within the continental Antarctic region. Our results also suggest that bacterial communities might be impacted by regional climatic and other environmental changes. The dataset developed in this study provides a comprehensive baseline that will provide a valuable tool for biodiversity conservation efforts on the continent. Further studies are clearly required, and we emphasize the need for more extensive campaigns to systematically sample and characterize Antarctic and sub-Antarctic soil microbial communities. APsmQ8MphSAgg4BzZyqdNTVideo Abstract
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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.
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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.
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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.
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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.
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Two main hypotheses have been proposed to explain the contemporary distribution of Antarctic terrestrial biota. We assess whether the current distribution of maritime Antarctic populations of the freshwater copepod Boeckella poppei is the result of (1) a post-Last Glacial Maximum (LGM) colonization, or whether (2) the species survived in regional glacial refugia throughout the LGM and earlier glaciations. Using 438 specimens from 34 different sampling sites across Southern South America, South Georgia, South Orkney Islands, South Shetland Islands, and the Antarctic Peninsula, we analyzed mitochondrial and nuclear sequences to uncover patterns of genetic diversity and population structure. We also performed median-joining haplotype network, phylogenetic reconstruction, and divergence time analyses. Finally, we evaluated past demographic changes and historical scenarios using the Approximate Bayesian Computation (ABC) method. Our data support the existence of two clades with different and contrasting biogeographic histories. The first clade has been present in maritime Antarctica since at least the mid-Pleistocene, with the South Orkney Islands the most likely refugial area. The second clade has a broader distribution including southern South America, South Georgia, South Shetland Islands, and the Antarctic Peninsula. The ABC method identified long-distance dispersal (LDD) colonization event(s) from southern South America to South Georgia and the maritime Antarctic after the LGM deglaciation, supporting more recent colonization of Antarctic locations. The current Antarctic and sub-Antarctic distribution of B. poppei is likely derived from two independent biogeographic events. The combination of both (1) post-LGM colonization from southern South America and (2) longer-term persistence in in situ regional refugia throughout glacial periods challenges current understanding of the biogeographic history of Antarctic freshwater biota. Re-colonization of ice-impacted Antarctic areas would have occurred following a LDD and Establishment model, pointing to the existence of possible post-dispersal barriers, despite widely assumed high passive dispersal capacity in freshwater invertebrates.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.