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Rafting has been proposed as an effective mechanism for species without freeliving pelagic larvae to achieve long-distance dispersal, theoretically preventing population differentiation over wide distributional ranges. Moreover, rafting has been advocated as a main dispersal mechanism for marine invertebrates with sub-Antarctic distributions, because of abundant buoyant kelps, driven by the Antarctic Circumpolar Current. Nonetheless, little attention has been given to the role of rafting to establish regular gene flow across the sub-Antarctic, and the geographic and temporal scales at which it occurs. Aiming to unravel these major questions about the extent of genetic connectivity across the Southern Ocean (SO), we studied the pulmonate limpet Siphonaria lateralis, a benthic species with encapsulated larvae, found on the rocky intertidal of sub-Antarctic islands and southern South America. Since S. lateralis is closely associated with D. antarctica, dispersal by rafting is plausible, as revealed by the absence of phylogeographic structure across the sub-Antarctic. We sampled 116 individuals from eight localities across the SO, and used 5,515 SNPs obtained through Genotyping-by-Sequencing, to determine contemporary genetic diversity, structure, and gene flow at two spatial scales; global, across the SO, and regional, within Kerguelen. Results identified substantial genetic structure, differentiating Patagonia, Falklands/Malvinas Islands, South Georgia and the Kerguelen archipelago, and low levels of contemporary gene flow. The most notable genetic differentiation was found between Patagonia/Falklands and South Georgia/Kerguelen. Structure was also significant between Patagonia and the Falkland/Malvinas Islands. Conversely, South Georgia and Kerguelen exhibited closer genetic affinity, and indications of recent but limited gene flow. Moreover, historical gene flow estimates between the four populations were low. At regional scale, noteworthy genetic structure persisted, and gene flow was insufficient to prevent genetic differentiation within Kerguelen. Consequently, rafting's potential may be overestimated as a contemporary mechanism promoting gene flow across the SO, as these events may be sporadic, irregular, and unpredictable for marine invertebrates lacking a larval dispersal stage, since contemporary dispersal events don't seem to facilitate high gene flow at both scales. Accordingly, other oceanographic factors or processes may hinder the establishment of species associated with macroalgae, and as consequence, contemporary genetic connectivity in the sub-Antarctic. [ABSTRACT FROM AUTHOR]

The origin and evolution in the Southern Hemisphere of the Austral teals, consisting of the grey-teal and brown-teal species complexes, remains poorly understood owing to limited molecular data. With the group containing multiple independent examples of flight loss, understanding the evolutionary history of the group is of significant interest for functional genomic studies into the evolution of flightlessness. Here, we present the first whole-mitogenome-based phylogeny of the Austral teals. We show that the group diverged from a common ancestor with mallards in the late Miocene and soon after radiated into the brown-teal and grey-teal lineages, in addition to the widely distributed pintails and green-winged teals. The brown-teal species complex, which includes the volant brown teal, the flight-impaired, sub-Antarctic Auckland Island teal, and the flightless, Chatham Island and sub-Antarctic Campbell Island teals, radiated within the past 0.9–1.8 Myr. The divergence of the extinct Chatham Island teal and the colonization of the Auckland and Campbell Islands occurred from mainland New Zealand. Morphological changes towards flightlessness are also present in the volant brown teal on mainland New Zealand, suggesting that this group was on the pathway to flightlessness, a trend that accelerated in some insular island lineages. [ABSTRACT FROM AUTHOR]

• Flightless steamer ducks preferred nesting on islets and along rocky coasts. • Upland geese preferred nesting in medium-dense shrubland. • Nest detection decreased with denser vegetation. • Invasive mink was present on 100 % of ten islets studied. • Interactive map for designing mink control actions. The introduction of carnivores to islands affects the conservation status of native prey. For two decades, American mink (Neogale vison) has expanded its distribution in the sub-Antarctic archipelago of Austral Patagonia, while preying on nests of solitary ground-nesting birds. Here, upland geese (Chloephaga picta) and flightless steamer ducks (Tachyeres pteneres) are naïve to such predation risk because of the lack of native terrestrial predators. We used nest occupancy models to reveal preferred breeding habitats of those two ground-nesting waterbirds to prioritize areas for future mink control programs. We searched for nests along 80 transects on Navarino Island, southernmost Chile, and 11 transects on 10 nearby islets (3 ± 2.9 ha). Our results showed that islets were essential for breeding in comparison to the main island (5.3 nests/km versus 0.8 nests/km, respectively). The occupancy models revealed that islets were particularly important for flightless steamer ducks, endemic to western Patagonia. As breeding habitat, upland geese preferred medium-dense shrubland, and flightless steamer ducks preferred rocky coastlines. Nest detection was negatively affected by dense vegetation and, in the case of the upland geese, towards the end of the survey. Ten camera traps (n = 385 trap nights) revealed mink presence on all islets, highlighting their capacity to swim in cold water, up to 340 m distance from the main island. We conclude that islets represent breeding refuges for ground-nesting waterbirds and therefore advocate allocating resources for mink control during the warm season on islets. We also provide predictive maps of nesting habitat preference of upland geese and flightless steamer ducks for conservation managers to focus their often scarce human and financial resources on areas critical for breeding. Finally, we argue that detection probability should be an integral part of bird breeding studies, which can be methodologically achieved through targeting transects, not nests, as sample units. [Display omitted] [ABSTRACT FROM AUTHOR]

Biodiversity patterns are shaped by the interplay between geodiversity and organismal characteristics. Superimposing genetic structure onto landscape heterogeneity (i.e., landscape genetics) can help to disentangle their interactions and better understand population dynamics. Previous studies on the sub‐Antarctic Prince Edward Islands (located midway between Antarctica and Africa) have highlighted the importance of landscape and climatic barriers in shaping spatial genetic patterns and have drawn attention to the value of these islands as natural laboratories for studying fundamental concepts in biology. Here, we assessed the fine‐scale spatial genetic structure of the springtail, Cryptopygus antarcticus travei, which is endemic to Marion Island, in tandem with high‐resolution geological data. Using a species‐specific suite of microsatellite markers, a fine‐scale sampling design incorporating landscape complexity and generalised linear models (GLMs), we examined genetic patterns overlaid onto high‐resolution digital surface models and surface geology data across two 1‐km sampling transects. The GLMs revealed that genetic patterns across the landscape closely track landscape resistance data in concert with landscape discontinuities and barriers to gene flow identified at a scale of a few metres. These results show that the island's geodiversity plays an important role in shaping biodiversity patterns and intraspecific genetic diversity. This study illustrates that fine‐scale genetic patterns in soil arthropods are markedly more structured than anticipated, given that previous studies have reported high levels of genetic diversity and evidence of genetic structing linked to landscape changes for springtail species and considering the homogeneity of the vegetation complexes characteristic of the island at the scale of tens to hundreds of metres. By incorporating fine‐scale and high‐resolution landscape features into our study, we were able to explain much of the observed spatial genetic patterns. Our study highlights geodiversity as a driver of spatial complexity. More widely, it holds important implications for the conservation and management of the sub‐Antarctic islands. [ABSTRACT FROM AUTHOR]

Rafting has been proposed as an effective mechanism for species without free-living pelagic larvae to achieve long-distance dispersal, theoretically preventing population differentiation over wide distributional ranges. Moreover, rafting has been advocated as a main dispersal mechanism for marine invertebrates with sub-Antarctic distributions, because of abundant buoyant kelps, driven by the Antarctic Circumpolar Current. Nonetheless, little attention has been given to the role of rafting to establish regular gene flow across the sub-Antarctic, and the geographic and temporal scales at which it occurs. Aiming to unravel these major questions about the extent of genetic connectivity across the Southern Ocean (SO), we studied the pulmonate limpet Siphonaria lateralis, a benthic species with encapsulated larvae, found on the rocky intertidal of sub-Antarctic islands and southern South America. Since S. lateralis is closely associated with D. antarctica, dispersal by rafting is plausible, as revealed by the absence of phylogeographic structure across the sub-Antarctic. We sampled 116 individuals from eight localities across the SO, and used 5,515 SNPs obtained through Genotyping-by-Sequencing, to determine contemporary genetic diversity, structure, and gene flow at two spatial scales; global, across the SO, and regional, within Kerguelen. Results identified substantial genetic structure, differentiating Patagonia, Falklands/Malvinas Islands, South Georgia and the Kerguelen archipelago, and low levels of contemporary gene flow. The most notable genetic differentiation was found between Patagonia/Falklands and South Georgia/Kerguelen. Structure was also significant between Patagonia and the Falkland/Malvinas Islands. Conversely, South Georgia and Kerguelen exhibited closer genetic affinity, and indications of recent but limited gene flow. Moreover, historical gene flow estimates between the four populations were low. At regional scale, noteworthy genetic structure persisted, and gene flow was insufficient to prevent genetic differentiation within Kerguelen. Consequently, rafting’s potential may be overestimated as a contemporary mechanism promoting gene flow across the SO, as these events may be sporadic, irregular, and unpredictable for marine invertebrates lacking a larval dispersal stage, since contemporary dispersal events don’t seem to facilitate high gene flow at both scales. Accordingly, other oceanographic factors or processes may hinder the establishment of species associated with macroalgae, and as consequence, contemporary genetic connectivity in the sub-Antarctic.

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. [ABSTRACT FROM AUTHOR]

Organic N (oN, e.g., amino acids) is an important N-resource for plants in soils replete with oN but not inorganic N (iN; i.e., NH4+ and NO3−), such as cold ecosystems with temperature-limited soil decomposition rates. However, sub-Antarctic literature assumes that plants only acquire iN, potentially underestimating plant-available N. We hypothesised that Marion Island (− 46.90°, 37.75°) grasses (Polypogon magellanicus, Poa cookii, Agrostis stolonifera and Poa annua) acquire oN and that oN relative to iN provision affects plant growth. We investigated oN and iN uptake and growth responses in two hydroponics experiments. In situ N (15N-glycine, 15NO3− and 15NH4+) acquisition was investigated at three field sites with decreasing faunal influence, thus iN input and microbial activity. When plants grown in mire water were supplied with 15N-glycine or 15NO3−, root δ15N enrichment was highest for glycine-supplied plants. In the second hydroponics experiment, plant N-uptake rates (nmol g biomass−1 s−1) were significantly higher for glycine than NO3−, but relative growth rates (g g−1 d−1) lower on glycine. There were species-specific biomass allocation responses to N concentration (4 mM and 0.4 mM) and N-form (glycine and NO3−). Glycine-supplied grasses at the low iN concentration field sites had significantly higher δ15N enrichment relative to those at sites with high iN, suggesting higher oN uptake when iN is limiting. We demonstrate the importance of accounting for oN acquisition in the sub-Antarctic. As a system with high soil oN relative to iN, plants may predominantly meet N-demands through oN rather than iN acquisition. [ABSTRACT FROM AUTHOR]

Abstract Biodiversity patterns are shaped by the interplay between geodiversity and organismal characteristics. Superimposing genetic structure onto landscape heterogeneity (i.e., landscape genetics) can help to disentangle their interactions and better understand population dynamics. Previous studies on the sub‐Antarctic Prince Edward Islands (located midway between Antarctica and Africa) have highlighted the importance of landscape and climatic barriers in shaping spatial genetic patterns and have drawn attention to the value of these islands as natural laboratories for studying fundamental concepts in biology. Here, we assessed the fine‐scale spatial genetic structure of the springtail, Cryptopygus antarcticus travei, which is endemic to Marion Island, in tandem with high‐resolution geological data. Using a species‐specific suite of microsatellite markers, a fine‐scale sampling design incorporating landscape complexity and generalised linear models (GLMs), we examined genetic patterns overlaid onto high‐resolution digital surface models and surface geology data across two 1‐km sampling transects. The GLMs revealed that genetic patterns across the landscape closely track landscape resistance data in concert with landscape discontinuities and barriers to gene flow identified at a scale of a few metres. These results show that the island's geodiversity plays an important role in shaping biodiversity patterns and intraspecific genetic diversity. This study illustrates that fine‐scale genetic patterns in soil arthropods are markedly more structured than anticipated, given that previous studies have reported high levels of genetic diversity and evidence of genetic structing linked to landscape changes for springtail species and considering the homogeneity of the vegetation complexes characteristic of the island at the scale of tens to hundreds of metres. By incorporating fine‐scale and high‐resolution landscape features into our study, we were able to explain much of the observed spatial genetic patterns. Our study highlights geodiversity as a driver of spatial complexity. More widely, it holds important implications for the conservation and management of the sub‐Antarctic islands.

How the near-shore marine benthic communities survived Quaternary glaciations in Antarctica is a major question for Southern Ocean biogeographers. Several hypotheses that consider life-history traits, such as bathymetric ranges and developmental modes, have been proposed. Nearshore species with high dispersive potential are expected to show star-like genealogies, with broadly distributed haplotypes surrounded by closely related variants at low frequencies, a consequence of rapid population post-glacial expansion mediated by larvae. By contrast, shallow-water taxa with low dispersal potential are expected to evidence marked genetic structure or even consist of separate cryptic species, due to their survival in small refugial populations subject to repeated bottlenecks. In this study we performed phylogeographic analyses on the high-latitude littorinid Laevilacunaria antarctica across its distribution from maritime Antarctica to South Georgia. This species is a highly abundant near-shore gastropod, commonly found on macroalgae, with low autonomous vagility and exhibits benthic protected development with no free-living dispersive stages. Such characteristics make this species a suitable model to test the above hypotheses. Contrary to low dispersal potential predictions, L. antarctica comprises a single unstructured unit across its distribution in maritime Antarctica, exhibiting a typical high-dispersal star-like, short-branched genealogy centered on a dominant broadly distributed haplotype. The South Georgia population, however, consists of a separate genetic unit, strongly differentiated from those of the maritime Antarctic. We estimate that these two genetic groups separated ~1.2 My, long before the Last Glacial Maximum and evolved independently in these areas. Our results thus provide partial support for the expected pattern for a near-shore marine benthic species with low innate dispersive potential. On a wider geographic scale (maritime Antarctica vs South Georgia), our results in L. antarctica provide support for the expected pattern for a near-shore marine benthic species with low innate dispersive potential. However, on a narrower scale (maritime Antarctica) life-history characters including the close association of the species with macroalgae, would allow dispersal and a species with low dispersal potential exhibits paradoxically an absence of genetic structure across hundreds of kilometers probably mediated by rafting. [ABSTRACT FROM AUTHOR]

South Georgia is a heavily glaciated sub‐Antarctic island in the Southern Ocean. Cumberland Bay is the largest fjord on the island, split into two arms, each with a large marine‐terminating glacier at the head. Although these glaciers have shown markedly different retreat rates over the past century, the underlying drivers of such differential retreat are not yet understood. This study uses observations and a new high‐resolution oceanographic model to characterize oceanographic variability in Cumberland Bay and to explore its influence on glacier retreat. While observations indicate a strong seasonal cycle in temperature and salinity, they reveal no clear hydrographic differences that could explain the differential glacier retreat. Model simulations suggest the subglacial outflow plume dynamics and fjord circulation are sensitive to the bathymetry adjacent to the glacier, though this does not provide persuasive reasoning for the asymmetric glacier retreat. The addition of a postulated shallow inner sill in one fjord arm, however, significantly changes the water properties in the resultant inner basin by blocking the intrusion of colder, higher salinity waters at depth. This increase in temperature could significantly increase submarine melting, which is proposed as a possible contribution to the different rates of glacier retreat observed in the two fjord arms. This study represents the first detailed description of the oceanographic variability of a sub‐Antarctic island fjord, highlighting the sensitivity of fjord oceanography to bathymetry. Notably, in fjords systems where temperature decreases with depth, the presence of a shallow sill has the potential to accelerate glacier retreat. Plain Language Summary: Cumberland Bay, a fjord on the sub‐Antarctic island of South Georgia, is split into two arms, each with a large marine‐terminating glacier. One of these glaciers is retreating much faster than the other, possibly due to differences in oceanography between the arms. Here, we investigate how the oceanography in Cumberland Bay varies seasonally and with the seabed depth by using oceanographic data and numerical ocean simulations. We find that the properties of buoyant plumes, which arise from meltwater entering the ocean from beneath the glacier, are sensitive to the seabed depth near the glaciers, resulting in strong differences in ocean flow between the fjord arms. Assuming higher ocean temperatures increase glacier melting, we find that the presence of a near‐glacier shallow sill likely increases melting by blocking deeper, colder waters and trapping warmer surface waters close to the glacier. As a shallow sill is likely to be present near the rapidly retreating glacier only, this result offers a persuasive explanation for the observed glacier retreat. Understanding the variability in oceanography and glacier retreat is important as they directly impact the marine ecosystem at South Georgia by influencing the availability of nutrients for primary production and food availability for higher predators. Key Points: Observational data and a new high‐resolution model are combined to describe oceanographic variability in Cumberland Bay, South GeorgiaWe show that the properties of buoyancy‐driven outflow plumes are sensitive to bathymetry and drive spatial differences between fjord armsWe highlight that the presence of a postulated inner sill may be a key factor in the observed rapid glacier retreat [ABSTRACT FROM AUTHOR]

For the first time, standing stocks and community structure have been reported in San Julián Bay, located in the Santa Cruz province, toward the southern tip of South America, within the sub-Antarctic region. The mean density of the meiofauna found was 6724 individuals/10 cm², with a high dominance of nematodes (97.69%). Multivariate studies (PERMANOVA) revealed two distinct meiofauna assemblages: one, in an upper littoral salt marsh habitat and other, in a medium to low soft bare sediment. In the middle of the bay --in front of San Julián city-- salt marsh habitats had the highest meiofaunal density, while bare sediments (medium-low levels) were the lowest. The mean average in the salt marsh area was 12246 individuals/10 cm², with nematodes being dominant followed by oligochaetes as the subdominant taxa. The mean average in bare sediments (medium to low levels) was 3962 individuals/10 cm², with nematodes as dominant and turbellarians, mastigophorans and maxillopodos (harpacticoid copepods) as subdominant taxa. Bare sediments related to Patagonian mussel's populations presented the lowest meiofauna densities. Diversity showed an opposite trend, with a maximum in medium-low levels and a minimum in salt-marshes habitat. Richness in number of taxa ranged from 8 to 12, with a total number of 18 taxa. Despite dominance of nematodes in meiofauna assemblages is known, maximum density found in San Julián bay is much higher than previously found for estuaries from north and mid-latitudes littoral sandy beaches and in the nearby region of the Straits of Magellan and Beagle Channel and other sub-Antarctic and Antarctic sites. On the other hand, the number of meiofauna taxa (no nematodes) is low, and its community structure differs from what has been reported in previous studies. The meiofauna taxa assemblages provide evidence that, in salt-marsh habitats, they have the highest densities, but the lowest diversity when compared with lower levels. This is likely due to adaptation problems of meiofauna communities to a semi-terrestrial habitat. [ABSTRACT FROM AUTHOR]

This article, published in Antarctic Science, discusses the risk of highly pathogenic avian influenza (HPAI) in the Southern Ocean and provides recommendations for prevention and control. HPAI outbreaks have resulted in the deaths of seabirds and marine mammals in various regions. The article emphasizes the importance of monitoring and early detection of HPAI, as well as taking precautions to prevent its spread. It provides guidelines for visitors to wildlife colonies, including maintaining distance from wildlife, practicing personal hygiene, and disinfecting equipment. The document also includes contact information for national competent authorities and organizations involved in Antarctic research. The recommendations aim to protect wildlife populations and prevent the spread of HPAI in the region. The article "Global dissemination of influenza A virus is driven by wild bird migration through arctic and subarctic zones" discusses the role of wild bird migration in the global spread of influenza A virus. It highlights the importance of arctic and subarctic zones as key areas for the transmission of the virus. The article also references other studies that examine the spread of avian influenza in different regions, including Azerbaijan, Antarctica, Chile, and Africa. It emphasizes the need for continued research and surveillance to better understand and manage the risk of avian influenza. [Extracted from the article]

How the near-shore marine benthic communities survived Quaternary glaciations in Antarctica is a major question for Southern Ocean biogeographers. Several hypotheses that consider life-history traits, such as bathymetric ranges and developmental modes, have been proposed. Near-shore species with high dispersive potential are expected to show star-like genealogies, with broadly distributed haplotypes surrounded by closely related variants at low frequencies, a consequence of rapid population post-glacial expansion mediated by larvae. By contrast, shallow-water taxa with low dispersal potential are expected to evidence marked genetic structure or even consist of separate cryptic species, due to their survival in small refugial populations subject to repeated bottlenecks. In this study we performed phylogeographic analyses on the high-latitude littorinid Laevilacunaria antarctica across its distribution from maritime Antarctica to South Georgia. This species is a highly abundant near-shore gastropod, commonly found on macroalgae, with low autonomous vagility and exhibits benthic protected development with no free-living dispersive stages. Such characteristics make this species a suitable model to test the above hypotheses. Contrary to low dispersal potential predictions, L. antarctica comprises a single unstructured unit across its distribution in maritime Antarctica, exhibiting a typical high-dispersal star-like, short-branched genealogy centered on a dominant broadly distributed haplotype. The South Georgia population, however, consists of a separate genetic unit, strongly differentiated from those of the maritime Antarctic. We estimate that these two genetic groups separated ~1.2 My, long before the Last Glacial Maximum and evolved independently in these areas. Our results thus provide partial support for the expected pattern for a near-shore marine benthic species with low innate dispersive potential. On a wider geographic scale (maritime Antarctica vs South Georgia), our results in L. antarctica provide support for the expected pattern for a near-shore marine benthic species with low innate dispersive potential. However, on a narrower scale (maritime Antarctica) life-history characters including the close association of the species with macroalgae, would allow dispersal and a species with low dispersal potential exhibits paradoxically an absence of genetic structure across hundreds of kilometers probably mediated by rafting.

The climate in the South Atlantic sector of the sub-Antarctic, and therefore on and around the island of South Georgia, is dependent on the Southern Hemisphere Westerlies (SHW) and the Antarctic Circumpolar Current (ACC). The SHW and the ACC, in turn, are strongly controlled by climate variability in the Southern Hemisphere. Accordingly, thick sediment sequences in the troughs across South Georgia's continental shelf serve as valuable archives for past climate variations in the Southern Ocean. Since Holocene climate fluctuations led to only minimal oscillations in glacier margin positions within the fjords, the entire shelf was exposed to dynamic ocean currents since at least 10 ka BP. Its depositional systems are therefore a suitable target for the reconstruction of Holocene dynamics of both the SHW and the ACC. Sub-bottom profiler data and radiocarbon ages from four gravity cores from the south-western South Georgia continental shelf provide evidence for a complex interplay between island run-off and ocean currents intruding into a unique cross-shelf trough system during the last ∼10 ka. The data reveal several prominent changes in sediment and Holocene climate dynamics, the most significant occurring between 8 and 7.7 cal ka BP and between 2.6 and 2.2 cal ka BP. Both of these time periods represent transitions from warmer to cooler and windier conditions in South Georgia and the Southern Hemisphere. Our record from the King Haakon Trough System is the first highly resolved Holocene archive from the marine realm on the south-western South Georgia continental shelf and suggests several large-scale Southern Hemisphere climate changes during the mid-to late Holocene.

Sub-Antarctic coastal marine ecosystems harbor rich and diverse benthic communities. Despite their ecological uniqueness and vulnerability to global changes, studies on benthic communities remain limited. Using underwater video-imagery, we investigated the taxonomic and functional diversity of benthic communities associated with hard substrates at Baie du Marin (Ile de la Possession, Crozet archipelago). The Baie du Marin species richness and diversity were additively partitioned to evaluate spatial patterns of species through the following spatial scales: within images, among images within transects, and among transects. We analyzed imagery data from seven transects located at different sites inside Baie du Marin and covering contrasting natural rocky habitats and underwater artificial cable substrates. A total of 50 faunal (mainly represented by Echinodermata and Porifera phyla) and 14 algae (mainly represented by Rhodophyta phylum) taxa were identified. Rocky substrates were dominated by high densities of the polychaetes Parasabella sp. and Lanice marionensis, whereas submarine cables were dominated by high densities of the bivalve Kidderia sp. attached to macroalgae. Our results show contrasted distribution patterns in the faunal and algal assemblages within the Baie du Marin, with significant ecological differences between submarine cables and natural rocky substrates. Larger spatial scale (i.e., among transects) accounted for most of the bay richness and diversity, highlighting a high-level of habitat heterogeneity within the bay. Through a trait-based approach, our findings revealed that Crozet benthic communities are characterized by low functional richness, evenness, and redundancy, highlighting a potential vulnerability to current and future natural and anthropogenic changes. This study provides a novel bentho-ecological baseline for future assessments of natural and anthropogenic impacts on the marine environment of the Crozet archipelago; and for the conservation management of these remote habitats that make part of the French Southern Territories Marine Protected Area, recently inscribed on the UNESCO World Heritage list.

Sea lions as a group, display strong site fidelity, and varying degrees of vulnerability to environmental change, disease and fisheries interactions. One of the rarest pinnipeds, the New Zealand sea lion (NZSL, Phocarctos hookeri) has a very restricted breeding range. At Campbell Island/Motu Ihupuku, one of the two primary breeding sites, at‐sea foraging behaviour is unknown. We hypothesised that NZSL of various sex and age classes would utilise the water column differently due to differing physiological constraints and therefore have different accessibility to prey resources. We tested whether sea lion diving behaviour varied in relation to (i) age and sex class, (ii) time of day and (iii) water depth. We also hypothesised that the proportion of benthic/pelagic diving, and consequently risk of fisheries interaction, would vary in relation to age and sex. Satellite telemetry tags were deployed on 25 NZSL from a range of age/sex classes recording dive depth, duration and location. Adult females and juveniles used inshore, benthic habitats, while sub‐adult males also utilised benthic habitats, they predominantly used pelagic habitat at greater distances from the island. Adult females and juveniles exhibited shorter dives than the same age/sex classes at the Auckland Islands, suggesting a lower dive effort for these age/sex classes at Campbell Island/Motu Ihupuku. Adult females dived more frequently than other age/sex classes, likely operating closer to their physiological limits; however, further data for this age class is needed. Sub‐adult male use of pelagic prey may increase their exposure to mid‐water trawls; however, further research detailing the degree of spatial overlap with fisheries is required. This study highlights the utility of spatially explicit dive data to predict vertical habitat use, niche separation of various age and sex classes of marine predators and attribute potential fisheries interaction risk in relation to predator habitat use. [ABSTRACT FROM AUTHOR]

Sea stars are a diverse and important component of the Southern Ocean benthos. However, scarce information is available regarding their diversity, distribution, evolution, and taxonomic uncertainties persist for multiple taxa. The Magellanic Region (south of Chile) remains under-sampled despite its pivotal location for species distribution and diversity, being located at the crossroad of three ocean basins. In this study, we assessed the biodiversity of coastal Magellanic sea stars and their affinities with other oceanic bioregions. An integrative approach combining morphological identification with DNA barcoding was implemented to highlight taxonomic discrepancies such as suspected synonymy and unrecognised diversity. Firstly, we identified a total of 15 species from the coastal Magellanic Region and reported the occurrence of Cycethra frigida Koehler, 1917 for the first time in this region. The distribution of these 15 species ranged from only in South America to circumpolar, bipolar, or possibly cosmopolitan. Secondly, we highlighted possible synonymy in two species pairs within the genera Anasterias and Odontaster. This preliminary biodiversity assessment forms an important baseline for monitoring and conservation purposes, especially in the face of distribution shifts as a response to climate change and the increased presence of invasive species. Developmental mode has previously been suggested to be important in shaping biogeographical patterns. However, developmental mode was insufficient to explain the observed patterns, and other factors (e.g., physiological constraints, competition, bathymetrical range, and the possibility of passively rafting on kelp) are suggested to be at least equally important. Finally, an increase in barcoding effort is needed to better capture phylogeographic patterns for each species, both by increasing the number of specimens investigated and by covering a broader geographical range. [ABSTRACT FROM AUTHOR]

Research on the limno-terrestrial Tardigrada fauna of the Sub-Antarctic zone began almost 120 years ago. Here we present an overview of the literature data on the presence of tardigrades on sub-Antarctic islands, including the substrates on which they have been found. From 32 published sources, we found original data on the occurrence of 49 currently valid species on six sub-Antarctic islands/island groups. Of these, 9 species (18%) were originally described from this zone, another 13 species (26%) were described from Continental or Maritime Antarctica, almost half of these species (22 species—45%) were originally described from European localities, and the remaining 5 species (10%) were originally described from South America, Africa, or Australia. The validity of the records of individual species is discussed. We consider the presence of 29 species in the Sub-Antarctic to be doubtful. We ascertained a total of 90 combinations of species and islands or island groups. More than half (64%) of these will require confirmation in the future because we currently consider them doubtful. We can conclude that the tardigrade fauna of the sub-Antarctic islands is only very superficially known, and the occurrence of most species in this zone must be verified. [ABSTRACT FROM AUTHOR]

There is no literature on outlier‐robust parametric mixed‐effects quantile regression models for continuous proportion data as an alternative to systematically identifying and eliminating outliers. To fill this gap, we formulate a robust method by extending the recently proposed fixed‐effects quantile regression model based on the heavy‐tailed Johnson‐t$$ t $$ distribution for continuous proportion data to the mixed‐effects modeling context, using a Bayesian approach. Our proposed method is motivated by and used to model the extreme quantiles of the vitality of cushion plants to provide insights into the ecology of the system in which the plants are dominant. We conducted a simulation study to assess the new method's performance and robustness to outliers. We show that the new model has good accuracy and confidence interval coverage properties and is remarkably robust to outliers. In contrast, our study demonstrates that the current approach in the literature for modeling hierarchically structured bounded data's quantiles is susceptible to outliers, especially when modeling the extreme quantiles. We conclude that the proposed model is an appropriate robust alternative to the current approach for modeling the quantiles of correlated continuous proportions when outliers are present in the data. [ABSTRACT FROM AUTHOR]

Background The present dataset is a compilation of georeferenced occurrences of the littorinid genus Laevilacunaria Powell, 1951 (Mollusca, Gastropoda) in the Southern Ocean. Occurrence data were obtained from field expeditions (Antarctic and sub-Antarctic sampling) between 2015 and 2022, together with a review of published literature including records from 1887 to 2022. Three Laevilacunaria species have been recorded from the Southern Ocean: Laevilacunaria bennetti, L. antarctica and L. pumilio. New information The present dataset includes 75 occurrences, representing the most exhaustive database of this Antarctic and sub-Antarctic littorinid genus. The publication of this data paper was funded by the Belgian Science Policy Office (BELSPO, contract n°FR/36/AN1/AntaBIS) in the Framework of EU-Lifewatch as a contribution to the SCAR Antarctic biodiversity portal (biodiversity.aq). [ABSTRACT FROM AUTHOR]

For the first time, standing stocks and community structure have been reported in San Julián Bay, located in the Santa Cruz province, toward the southern tip of South America, within the sub-Antarctic region. The mean density of the meiofauna found was 6724 individuals/10 cm2, with a high dominance of nematodes (97.69%). Multivariate studies (PERMANOVA) revealed two distinct meiofauna assemblages: one, in an upper littoral salt marsh habitat and other, in a medium to low soft bare sediment. In the middle of the bay —in front of San Julián city— salt marsh habitats had the highest meiofaunal density, while bare sediments (medium-low levels) were the lowest. The mean average in the salt marsh area was 12246 individuals/10 cm2, with nematodes being dominant followed by oligochaetes as the subdominant taxa. The mean average in bare sediments (medium to low levels) was 3962 individuals/10 cm2, with nematodes as dominant and turbellarians, mastigophorans and maxillopodos (harpacticoid copepods) as subdominant taxa. Bare sediments related to Patagonian mussel’s populations presented the lowest meiofauna densities. Diversity showed an opposite trend, with a maximum in medium-low levels and a minimum in salt-marshes habitat. Richness in number of taxa ranged from 8 to 12, with a total number of 18 taxa. Despite dominance of nematodes in meiofauna assemblages is known, maximum density found in San Julián bay is much higher than previously found for estuaries from north and mid-latitudes littoral sandy beaches and in the nearby region of the Straits of Magellan and Beagle Channel and other sub-Antarctic and Antarctic sites. On the other hand, the number of meiofauna taxa (no nematodes) is low, and its community structure differs from what has been reported in previous studies. The meiofauna taxa assemblages provide evidence that, in salt-marsh habitats, they have the highest densities, but the lowest diversity when compared with lower levels. This is likely due to adaptation problems of meiofauna communities to a semi-terrestrial habitat.

Question: Plant–plant interactions can strongly influence community structure and composition. The outcome of these interactions can vary considerably across space and is often linked to environmental conditions, with, for example, a higher prevalence of facilitative interactions typically being observed under greater environmental severity. To date, most studies have documented shifts from competitive to facilitative (or neutral) plant–plant and plant–lichen interactions along gradients of increasing environmental severity from pairwise interspecific interactions. However, few studies have examined if the outcome of these interactions for different taxonomic groups is dependent on environmental conditions across multiple environmental stress gradients. Location: Sub‐Antarctic Marion Island. Methods: We examine community‐level variation in the response of four taxa (i.e., vascular plants, hepatics, mosses, and lichens) to an interaction with a long‐lived cushion plant species (Azorella selago) that ameliorates microenvironmental conditions, testing how the effect of the cushion plant on the taxa varies along multiple stress gradients at the scale of a landform. Results: Contrary to expectations, even when considering multiple proximate predictor variables, fine‐scale spatial variation in the effect of A. selago on the taxa could not be explained. However, the outcome of the interaction with A. selago differed between taxonomic groups, with vascular plants benefitting and the non‐vascular taxa experiencing neutral or negative impacts. Conclusions: This study highlights that the impacts of biotic interactions cannot always be generalized across plant groups, and that it is necessary to consider taxon‐specific responses when predicting community‐level impacts of biotic interactions. More generally, we demonstrate how complex spatial variation in environmental stressors can be explicitly considered when modelling variation in the outcome of plant–plant interactions. [ABSTRACT FROM AUTHOR]

Detecting non-native species can be challenging, particularly in the case of taxa such as seaweeds, which can be difficult to distinguish based on morphology and often require molecular-assisted taxonomy for reliable identification. The sub-Antarctic island of South Georgia supports unique and important marine biodiversity, including a rich seaweed flora, but despite its isolation, its inshore ecosystems are susceptible to the introduction of potentially invasive non-native species. Here, we provide the first report of a non-native seaweed in South Georgia, Ulva fenestrata Postels & Ruprecht (Ulvophyceae, Chlorophyta), and confirm its widespread presence in the Falkland Islands via molecular-assisted taxonomy. Phylogenetic analyses of tufA and rbcL-3P genetic markers enabled the identification of a specimen collected from Grytviken, South Georgia in November 2021 as U. fenestrata. In terms of tufA sequence, this sample was identical to specimens collected from four sites spanning West and East Falkland in 2013 and 2018. This study represents the second Southern Hemisphere record of U. fenestrata, which is generally regarded as a Northern Hemisphere species. Our findings provide a foundation for monitoring this potentially invasive species in South Georgia, and for determining its likely source and mode of arrival, while emphasising the importance of robust biosecurity measures. [ABSTRACT FROM AUTHOR]

Facilitation is an interaction where one species (the benefactor) positively impacts another (the beneficiary). However, the reciprocal effects of beneficiaries on their benefactors are typically only documented using short‐term datasets. We use Azorella selago, a cushion plant species and benefactor, and a co‐occurring grass species, Agrostis magellanica, on sub‐Antarctic Marion Island, comparing cushion plants and the grasses growing on them over a 13‐year period using a correlative approach. We additionally compare the feedback effect of A. magellanica on A. selago identified using our long‐term dataset with data collected from a single time period. We hypothesized that A. selago size and vitality would be negatively affected by A. magellanica cover and that the effect of A. magellanica on A. selago would become more negative with increasing beneficiary cover and abiotic‐severity, due to, e.g. more intense competition for resources. We additionally hypothesized that A. magellanica cover would increase more on cushion plants with greater dead stem cover, since dead stems do not inhibit grass colonization or growth. The relationship between A. magellanica cover and A. selago size and vitality was not significant in the long‐term dataset, and the feedback effect of A. magellanica on A. selago did not vary significantly with altitude or aspect; however, data from a single time period did not consistently identify this same lack of correlation. Moreover, A. selago dead stem cover was not significantly related to an increase in A. magellanica cover over the long term; however, we observed contrasting results from short‐term datasets. Long‐term datasets may, therefore, be more robust (and practical) for assessing beneficiary feedback effects than conventional approaches, particularly when benefactors are slow‐growing. For the first time using a long‐term dataset, we show a lack of physical cost to a benefactor species in a facilitative interaction, in contrast to the majority of short‐term studies. [ABSTRACT FROM AUTHOR]

Here we present a case study for using visual stratigraphy to date a shallow firn core from coastal West Antarctica. The Mount Siple ice core has the potential to reconstruct climate in this data-sparse region over recent decades. Line scanned images of the 24 m firn core were used to generate a grey-scale, which displays variability consistent with annual cycles. The resulting Mount Siple age scale spans from 1998 ± 1 to 2017 CE. This study demonstrates that the seasonal changes in the grey-scale record provide an independent method of dating firn cores. However, the presence of melt layers at this site has introduced an error of ±1 year. Visual line stratigraphy has the unique advantage over traditional annual layer counting, based on chemical or isotopic species, of being non-destructive and relatively inexpensive. Visual line stratigraphy has proved to be an effective dating method for this site. [ABSTRACT FROM AUTHOR]

The implementation of molecular data for the analysis of nemertean diversity has unraveled the taxonomic status of several species and many higher taxa within the group. Nowadays, a large proportion of novel putative species are being discovered and it is necessary to add molecular data to the morphological description to obtain a correct identification. In this study, we used mitochondrial cytochrome oxidase I gene (COI) as molecular marker to investigate the diversity of nemerteans from a marine Sub-Antarctic environment. We used Automatic Barcode Gap Discovery (ABGD), Poisson Tree Processes (PTP) and Bayesian implementation of the PTP model (bPTP) as well as reciprocal monophyly on neighbor-joining (NJ) and maximum likelihood (ML) trees for species delimitation. ABGD showed a clear barcoding gap (6 to 10%) and the presence of 15 different putative nemertean species in the dataset of 54 COI sequences from the marine protected area "Namuncurá–Burdwood Bank" (MPA-BB), expanding the known biodiversity for the Sub-Antarctic region. Ten monostiliferan and five heteronemertean species were found. Our results also confirm the presence of two Parborlasia corrugatus cryptic species in the Antarctic and Sub-Antarctic region. This work highlights the importance of the MPA-BB as a biodiversity hotspot and provide molecular data for the Phylum Nemertea in the Southwestern Atlantic Ocean. [ABSTRACT FROM AUTHOR]

IntroductionEcogeographical patterns in body size have been described across a wide range of vertebrate species. However, insects have shown inconsistent patterns in studies to date. Aquatic insects, particularly those from remote regions, have barely been explored.MethodsThe Magellanic sub-Antarctic ecoregion offers an ideal natural laboratory with near pristine environments, limiting the potential influence of confounding variables. In this study, we evaluated the influence of elevation on body and wing size and aspect ratio patterns for 10 species of mayfly (Ephemeroptera) and stonefly (Plecoptera) along a steep coastal elevation gradient (~0–600 m a.s.l.).ResultsWe detected significant relationships between altitude and morphological features for the studied species. Additionally, we found that in females, morphological changes were slightly more pronounced than in males, probably due to their role as dispersers. While body size showed an increase along the elevation gradient, there was a notable decrease in some species' wing length over a relatively short geographic distance.DiscussionOur data suggest that morphological plasticity might be promoted in response to the harsh environmental conditions that typify the steep coastal Magellanic sub-Antarctic mountain ranges.

Biological invasions in remote areas that experience low human activity provide unique opportunities to elucidate processes responsible for invasion success. Here we study the most widespread invasive plant species across the isolated islands of the Southern Ocean, the annual bluegrass, Poa annua. To analyse geographical variation in genome size, genetic diversity and reproductive strategies, we sampled all major sub‐Antarctic archipelagos in this region and generated microsatellite data for 470 individual plants representing 31 populations. We also estimated genome sizes for a subset of individuals using flow cytometry. Occasional events of island colonization are expected to result in high genetic structure among islands, overall low genetic diversity and increased self‐fertilization, but we show that this is not the case for P. annua. Microsatellite data indicated low population genetic structure and lack of isolation by distance among the sub‐Antarctic archipelagos we sampled, but high population structure within each archipelago. We identified high levels of genetic diversity, low clonality and low selfing rates in sub‐Antarctic P. annua populations (contrary to rates typical of continental populations). In turn, estimates of selfing declined in populations as genetic diversity increased. Additionally, we found that most P. annua individuals are probably tetraploid and that only slight variation exists in genome size across the Southern Ocean. Our findings suggest multiple independent introductions of P. annua into the sub‐Antarctic, which promoted the establishment of genetically diverse populations. Despite multiple introductions, the adoption of convergent reproductive strategies (outcrossing) happened independently in each major archipelago. The combination of polyploidy and a mixed reproductive strategy probably benefited P. annua in the Southern Ocean by increasing genetic diversity and its ability to cope with the novel environmental conditions. [ABSTRACT FROM AUTHOR]

Simple Summary: Sub-Antarctic islands, such as the Kerguelen Archipelago, are home to a unique collection of species because of their isolation. However, their isolation and low number of species make them more susceptible to invasion. This is particularly important as warming temperatures due to climate change are also making conditions worse for local species, and potentially better for recently introduced species, most of which are from warmer areas. The threats from non-native species in such a sensitive and unique ecosystem makes it important to understand the specific effects of climate change on non-native species to be able to predict their likely local population trajectory. In this study, we explored whether warming temperatures helped a non-native blowfly, Calliphora vicina, establish and spread throughout Kerguelen. We found that warming temperatures have made this species better able to survive and reproduce annually, and that it should continue to benefit from warming temperatures. We also discuss the potential impacts of this invasive blowfly on the local ecosystem and recommend further studies to assess its impacts and to identify management options for the species, which is likely to persist locally for the long term. The isolated sub-Antarctic islands are of major ecological interest because of their unique species diversity and long history of limited human disturbance. However, since the presence of Europeans, these islands and their sensitive biota have been under increasing pressure due to human activity and associated biological invasions. In such delicate ecosystems, biological invasions are an exceptional threat that may be further amplified by climate change. We examined the invasion trajectory of the blowfly Calliphora vicina (Robineau-Desvoidy 1830). First introduced in the sub-Antarctic Kerguelen Islands in the 1970s, it is thought to have persisted only in sheltered microclimates for several decades. Here, we show that, in recent decades, C. vicina has been able to establish itself more widely. We combine experimental thermal developmental data with long-term ecological and meteorological monitoring to address whether warming conditions help explain its current success and dynamics in the eastern Kerguelen Islands. We found that warming temperatures and accumulated degree days could explain the species' phenological and long-term invasion dynamics, indicating that climate change has likely assisted its establishment. This study represents a unique long-term view of a polar invader and stresses the rapidly increasing susceptibility of cold regions to invasion under climate change. [ABSTRACT FROM AUTHOR]

Sea stars are a diverse and important component of the Southern Ocean benthos. However, scarce information is available regarding their diversity, distribution, evolution, and taxonomic uncertainties persist for multiple taxa. The Magellanic Region (south of Chile) remains under-sampled despite its pivotal location for species distribution and diversity, being located at the crossroad of three ocean basins. In this study, we assessed the biodiversity of coastal Magellanic sea stars and their affinities with other oceanic bioregions. An integrative approach combining morphological identification with DNA barcoding was implemented to highlight taxonomic discrepancies such as suspected synonymy and unrecognised diversity. Firstly, we identified a total of 15 species from the coastal Magellanic Region and reported the occurrence of Cycethra frigida Koehler, 1917 for the first time in this region. The distribution of these 15 species ranged from only in South America to circumpolar, bipolar, or possibly cosmopolitan. Secondly, we highlighted possible synonymy in two species pairs within the genera Anasterias and Odontaster. This preliminary biodiversity assessment forms an important baseline for monitoring and conservation purposes, especially in the face of distribution shifts as a response to climate change and the increased presence of invasive species. Developmental mode has previously been suggested to be important in shaping biogeographical patterns. However, developmental mode was insufficient to explain the observed patterns, and other factors (e.g., physiological constraints, competition, bathymetrical range, and the possibility of passively rafting on kelp) are suggested to be at least equally important. Finally, an increase in barcoding effort is needed to better capture phylogeographic patterns for each species, both by increasing the number of specimens investigated and by covering a broader geographical range.

Research on the limno-terrestrial Tardigrada fauna of the Sub-Antarctic zone began almost 120 years ago. Here we present an overview of the literature data on the presence of tardigrades on sub-Antarctic islands, including the substrates on which they have been found. From 32 published sources, we found original data on the occurrence of 49 currently valid species on six sub-Antarctic islands/island groups. Of these, 9 species (18%) were originally described from this zone, another 13 species (26%) were described from Continental or Maritime Antarctica, almost half of these species (22 species—45%) were originally described from European localities, and the remaining 5 species (10%) were originally described from South America, Africa, or Australia. The validity of the records of individual species is discussed. We consider the presence of 29 species in the Sub-Antarctic to be doubtful. We ascertained a total of 90 combinations of species and islands or island groups. More than half (64%) of these will require confirmation in the future because we currently consider them doubtful. We can conclude that the tardigrade fauna of the sub-Antarctic islands is only very superficially known, and the occurrence of most species in this zone must be verified.

Since the discovery of glacial features on sub-Antarctic Marion Island, the character and extent of a historic glacial period have remained an important research focus for earth science investigations. Previous glacial reconstructions were limited to mostly pre-GPS field observations and pre-digital mapping through a Geographic Information System. With the aid of GPS field mapping, high-resolution satellite imagery and a digital surface model with a 1 × 1 m cell resolution, this paper provides a comprehensive, geo-rectified spatial geodatabase and map of Marion Island’s glacial geomorphology. The geodatabase includes an inventory of glacial erosional (e.g. striations) and depositional (e.g. moraines) features compiled from existing records as well as new features mapped from recent field observations. The final map and the geodatabase, which is downloadable as ESRI layer-package files, will aid future field investigations and modelling applications to understand Marion Island’s Quaternary landscape evolution and post-glacial ecological succession.

Littorinid snails are present in most coastal areas globally, playing a significant role in the ecology of intertidal communities. Laevilitorina is a marine gastropod genus distributed exclusively in the Southern Hemisphere, with 21 species reported from South America, the sub-Antarctic islands, Antarctica, New Zealand, Australia and Tasmania. Here, an updated database of 21 species generated from a combination of sources is presented: 1) new field sampling data; 2) published records; 3) the Global Biodiversity Information Facility (GBIF) and The Atlas of Living Australia (ALA), to provide a comprehensive description of the known geographic distribution of the genus and detailed occurrences for each of the 21 species. The database includes 813 records (occurrences), 53 from field sampling, 174 from the literature, 128 from GBIF, and 458 from ALA. West Antarctica had the highest species richness (8 species), followed by sub-Antarctic islands of New Zealand (4 species) and the south-east shelf of Australia (4 species). The provinces of Magellan, New Zealand South Island, and sub-Antarctic Islands of the Indian Ocean include two species each. This study specifically highlights reports of L. pygmaea and L. venusta, species that have been almost unrecorded since their description. Recent advances in molecular studies of L. caliginosa showed that this species does not correspond to a widely distributed taxon, but to multiple divergent lineages distributed throughout the Southern Ocean. Ongoing molecular and taxonomic studies are necessary for a better understanding of the diversity and biogeography of this genus. [ABSTRACT FROM AUTHOR]

Sub-Antarctic Marion Island's glacial history has acted as a control on abiotic terrestrial processes and the colonization and distribution of biotic species found on the island today. Recent chronological studies have shown an early deglaciation of the island and identified new geomorphological features associated with past ice dynamics. These permit a reassessment of ice extent during and after the island's last local glacial maximum. In this paper, we provide a revised reconstruction of the island's palaeo-ice extent by using a geomorphology-based approach to delineate palaeo-ice margins and demarcate possible glacial basins. The model presented here provides the needed spatial context for future studies on the variations in the distribution of species (e.g. microorganisms and plant species) and abiotic processes and forms (e.g. soil development and periglacial landforms). In addition, it highlights areas that require improved geophysical assessment in order to produce a more complete island-scale reconstruction of former ice extents (e.g. the west coast). [ABSTRACT FROM AUTHOR]

Polar regions are characterized by rocky terrains with sparse vegetation and oligotrophic soils, i.e. "fellfields". In such ecosystems, microbial communities should be essential for soil-plant functioning but their diversity is poorly explored. The sub-Antarctic Kerguelen Islands fellfields are characterized by an endemic long-lived cushion plant, Lyallia kerguelensis which rhizosphere may be a shelter for microbes in this harsh environment. Cushions are affected by necrosis and we expect the rhizomicrobiome composition to be related to plant necrosis. We analysed bacterial and fungal communities in bulk- and rhizospheric soils from L. kerguelensis in five different fellfields across the Kerguelen Islands using 16S rRNA and ITS1 metabarcoding. We found that soil microbial communities were composed of both restricted and cosmopolitan taxa. While all sites were dominated by the same bacterial taxa (Chloroflexi, Actinobacteria, a-Proteobacteria and Acidobacteria), the relative abundance of the main fungal phyla (Ascomycota, Basidiomycota, Mortierellomycota and Rozellomycota) highly differed between sites. L. kerguelensis rhizomicrobiome was at least as diverse as the bulk soil, making the rhizosphere a possible reservoir of microbial diversity. It was composed of the same main bacterial phyla than detected in the bulk soil while the composition of the rhizosphere fungal communities was specific to each plant. No common microorganisms were identified regarding cushion necrosis extent across plants and sites, but several microbial putative functions were shared, suggesting a possible shift in soil functioning with cushion necrosis increase. Our study brings new information on the diversity and composition of the microbial communities of fellfield soils in a sub-Antarctic Island and the rhizomicrobiome of a characteristic endemic cushion plant. [ABSTRACT FROM AUTHOR]

Polar regions are characterized by rocky terrains with sparse vegetation and oligotrophic soils, i.e. “fellfields”. In such ecosystems, microbial communities should be essential for soil-plant functioning but their diversity is poorly explored. The sub-Antarctic Kerguelen Islands fellfields are characterized by an endemic long-lived cushion plant, Lyallia kerguelensis which rhizosphere may be a shelter for microbes in this harsh environment. Cushions are affected by necrosis and we expect the rhizomicrobiome composition to be related to plant necrosis. We analysed bacterial and fungal communities in bulk- and rhizospheric soils from L. kerguelensis in five different fellfields across the Kerguelen Islands using 16S rRNA and ITS1 metabarcoding. We found that soil microbial communities were composed of both restricted and cosmopolitan taxa. While all sites were dominated by the same bacterial taxa (Chloroflexi, Actinobacteria, α-Proteobacteria and Acidobacteria), the relative abundance of the main fungal phyla (Ascomycota, Basidiomycota, Mortierellomycota and Rozellomycota) highly differed between sites. L. kerguelensis rhizomicrobiome was at least as diverse as the bulk soil, making the rhizosphere a possible reservoir of microbial diversity. It was composed of the same main bacterial phyla than detected in the bulk soil while the composition of the rhizosphere fungal communities was specific to each plant. No common microorganisms were identified regarding cushion necrosis extent across plants and sites, but several microbial putative functions were shared, suggesting a possible shift in soil functioning with cushion necrosis increase. Our study brings new information on the diversity and composition of the microbial communities of fellfield soils in a sub-Antarctic Island and the rhizomicrobiome of a characteristic endemic cushion plant.

Aim: The Antarctic Circumpolar Current imparts significant structure to the Southern Ocean biota. The Antarctic Polar Front is a major barrier to dispersal, with separate species (or sometimes intraspecific clades) normally occurring either side of this feature. We examined the biogeographic structure of an apparent exception to this rule in a widespread genus of the Southern Ocean, the periwinkle snail, Laevilitorina. Location: Southern Ocean. Taxon: Littorinidae, Laevilitorininae, Laevilitorina. Methods: Using 750 specimens from 16 Southern Ocean Laevilitorina populations across >8000 km, we analysed mitochondrial COI and nuclear 28S sequences to uncover the evolutionary history of these marine near‐shore snails. We utilized multi‐locus phylogenetic reconstructions, species‐delimitation analyses, divergence‐time estimations and geometric morphometrics. Results: Molecular data revealed that the widespread nominal species L. caliginosa comprises seven species‐level clades, all supported by morphological data, whereas the Antarctic nominal species L. antarctica, L. claviformis and L. umbilicata are conspecific. Six "caliginosa" clades are restricted to southern South America, but one lineage extends from Antarctica to distant sub‐Antarctic islands on both sides of the APF. Geometric morphometrics also identified significant differences among these clades, but uncoupled from genetic differentiation. Main conclusions: The apparent trans‐APF distribution of the poorly dispersing Laevilitorina caliginosa is largely illusory: this taxon consists of at least seven discrete species, only one of which has a trans‐APF distribution. Similar to most Laevilitorina species, the remaining six "caliginosa" clades are narrow endemics. Biogeographical patterns in Laevilitorina reflect the role of vicariance associated with geological processes together with recent long‐distance dispersal events. Laevilitorina originated near the Eocene/Oligocene boundary and diversified during the Miocene and the Pliocene. Laevilitorina is not a cryptic‐species complex: speciation was accompanied by hitherto unrecognized morphological differentiation. This study represents the most detailed molecular work on Southern‐Ocean littorinids and reveals unforeseen diversity across this globally important region. [ABSTRACT FROM AUTHOR]

Age and growth of blue antimora Antimora rostrata were examined in the waters off New Zealand and Macquarie Island (southwestern Pacific). Samples off Macquarie Island were collected from bycatch in the Patagonian toothfish longline fishery. Individuals between 20 and 44 years in age measured between 37.6–71.1 cm in total length. Bottom trawl catches from New Zealand waters consisted of smaller and younger fish (11 to 38 years), measuring 22.5–52.5 cm long. The age classes with the greatest numbers in the former area were represented by fish aged 33–34 years (25.7%). In the latter area, the most numerous age classes were 21–23 years (12.1%), 28–29 years (17.6%), and 32 years (6.6%). The blue antimora from off the Macquarie Island show similar growth rates to those of individual fish from the Ross, Lazarev and Weddell Seas, waters off the Kerguelen and Crozet Islands, and southeastern Greenland. Individuals from New Zealand waters demonstrate the slowest growth rates compared to other parts of the species' range but are quite similar to individuals from the Flemish Cap area. Further research to identify the stock structure of this broadly distributed species is warranted to provide context to differences in growth rates observed between populations. [ABSTRACT FROM AUTHOR]

Invasive alien species may cause substantial changes and damaging impacts. Here, we document the current distribution and ecological interactions with native biota of relatively recently introduced wasps, Vespula vulgaris and V. germanica, in the southern part of the Cape Horn Biosphere Reserve (CHBR) in southern Chile. We conducted field studies in four different habitats on Navarino Island: evergreen, deciduous and mixed forests, and shrublands. The spread of V. vulgaris throughout the island has led to it occupying suitable habitats in both urban and rural settings, while V. germanica has not been observed in the last 2 years. The presence of V. vulgaris in remote areas of the CHBR is likely the result of human-mediated movement through the channels within the reserve. The composition of foraged items was different in each of the four studied habitats, yet strongly linked to the resources of each, indicating the inherent ability of V. vulgaris to exploit available resources efficiently. V. vulgaris mainly forages berries from shrubs, and preys on a variety of arthropods, particularly hoverflies, craneflies and lepidoptera larvae. The lack of natural competitors and availability of multiple resources has allowed V. vulgaris to rapidly become a common pest in urban and rural settings in the southern extremity of South America. While we consider that eradication would now be impossible, population control at local scales may still be possible with proper planning and long-term management. Our data provide a baseline for management planning, and we strongly recommend social engagement and dialog with relevant governmental institutions to achieve this challenging task. [ABSTRACT FROM AUTHOR]

Abstract Birds are known to act as potential vectors for the exogenous dispersal of bryophyte diaspores. Given the totipotency of vegetative tissue of many bryophytes, birds could also contribute to endozoochorous bryophyte dispersal. Research has shown that fecal samples of the upland goose (Chloephaga picta) and white‐bellied seedsnipe (Attagis malouinus) contain bryophyte fragments. Although few fragments from bird feces have been known to regenerate, the evidence for the viability of diaspores following passage through the bird intestinal tract remains ambiguous. We evaluated the role of endozoochory in these same herbivorous and sympatric bird species in sub‐Antarctic Chile. We hypothesized that fragments of bryophyte gametophytes retrieved from their feces are viable and capable of regenerating new plant tissue. Eleven feces disk samples containing undetermined moss fragments from C. picta (N = 6) and A. malouinus (N = 5) and six moss fragment samples from wild‐collected mosses (Conostomum tetragonum, Syntrichia robusta, and Polytrichum strictum) were grown ex situ in peat soil and in vitro using a agar Gamborg medium. After 91 days, 20% of fragments from A. malouinus feces, 50% of fragments from C. picta feces, and 67% of propagules from wild mosses produced new growth. The fact that moss diaspores remained viable and can regenerate under experimental conditions following the passage through the intestinal tracts of these robust fliers and altitudinal and latitudinal migrants suggests that sub‐Antarctic birds might play a role in bryophyte dispersal. This relationship may have important implications in the way bryophytes disperse and colonize habitats facing climate change.

Pearson's correlation coefficients (R 2) for mean annual temperature trends between stations and b. summary of linear regression statistics and rates of change of mean annual air temperature for sub-Antarctic stations. Keywords: air temperature; climate change; ecosystem change; global warming; sub-Antarctic; tipping point EN air temperature climate change ecosystem change global warming sub-Antarctic tipping point 124 126 3 05/16/23 20230401 NES 230401 This paper presents the rate of warming in the sub-Antarctic region in the 21st century and summarizes the landscape and ecosystem responses to the increased warming. Air temperature, climate change, ecosystem change, global warming, sub-Antarctic, tipping point. [Extracted from the article]

Sub-Antarctic glacier chronologies can provide valuable information about the past variability of climate dynamics in the Southern Ocean region. The Kerguelen Archipelago (49°S) is advantageously located under the influence of the Southern Hemisphere's westerly wind belt, thus fluctuations of climate-sensitive glaciers on Kerguelen can provide a baseline for understanding the behavior of this atmospheric regime in response to climatic forcings. We present 17 36Cl exposure ages of moraine and erratic boulders to provide chronological constraints to paleoglacier extents of the Guynemer cirque glacier, located just north of the Cook Ice Cap. Erratic boulders show ice thinning in the Guynemer region started to occur in the Late Glacial by 13.5 ka and continued past 12.4 ka. Ice retreat was punctuated by the formation of two moraine stages, the outermost at 11.5 ± 0.4 ka followed by another at 10.4 ± 1.2 ka, which are indicative of Early Holocene glacier advances/standstills. A glacial advance occurred at 1.4 ± 0.3 ka, which corroborates other Late Holocene re-advances elsewhere on the archipelago. Finally, three undated moraine stages are found between 1.4 ka and the 1960s. The lack of moraines after 10.4 ka and through the Mid-Holocene suggests that the Guynemer glacier was significantly smaller during this extended period of the Holocene compared to its Early Holocene as well as its Late Holocene limits. The Guynemer glacier history provides unique evidence of Early Holocene moraines on Kerguelen, which have not been discovered thus far on the archipelago. Similar to glaciers in Patagonia, New Zealand and South Georgia, the Guynemer glacier was at its largest Holocene extent in the Early Holocene. However, while other southern mid-latitude glacier chronologies show progressively smaller glacial extents throughout the Mid- to Late Holocene, the Late Holocene re-advance of the Guynemer glacier, like other Kerguelen glaciers, likely exceeded its Mid-Holocene extent. • We present 17 new 36Cl surface exposure ages from the Kerguelen Archipelago. • 36Cl ages range from 13.5 ± 0.3 ka to 1.2 ± 0.2 ka. • First early Holocene-dated moraines on Kerguelen. • Glacial readvance occurred in late Holocene. • Holocene glacial evolution on Kerguelen differs from other sub-Antarctic glaciers. [ABSTRACT FROM AUTHOR]

Here we present a case study for using visual stratigraphy to date a shallow firn core from coastal West Antarctica. The Mount Siple ice core has the potential to reconstruct climate in this data-sparse region over recent decades. Line scanned images of the 24 m firn core were used to generate a grey-scale, which displays variability consistent with annual cycles. The resulting Mount Siple age scale spans from 1998 ± 1 to 2017 CE. This study demonstrates that the seasonal changes in the grey-scale record provide an independent method of dating firn cores. However, the presence of melt layers at this site has introduced an error of ±1 year. Visual line stratigraphy has the unique advantage over traditional annual layer counting, based on chemical or isotopic species, of being non-destructive and relatively inexpensive. Visual line stratigraphy has proved to be an effective dating method for this site.

Aim: Understanding how natural populations respond to climatic shifts is a fundamental goal of biological research in a fast‐changing world. The Southern Ocean represents a fascinating system for assessing large‐scale climate‐driven biological change, as it contains extremely isolated island groups within a predominantly westerly, circumpolar wind and current system. Blue‐eyed shags represent a paradoxical seabird radiation—a circumpolar distribution implies strong dispersal capacity yet their species‐rich nature suggests local adaptation and isolation. Here we attempt to resolve this paradox in light of the history of repeated cycles of climate change in the Southern Ocean. Location: Southern Ocean. Taxa: 16 species and subspecies of blue‐eyed shags (Phalacrocoracidae; Leucocarbo spp.). Methods: We use mitochondrial and nuclear sequence data from individuals across the geographical range of the genus to conduct the first comprehensive, time‐calibrated phylogenetic analyses and ancestral‐range biogeographical reconstructions of the blue‐eyed shags. Results: The origins of many island‐endemic lineages are remarkably recent, consistent with a recent high‐latitude circumpolar radiation in the Pliocene or Early Pleistocene. This recent sub‐Antarctic expansion contrasts with significantly deeper lineages detected in South America and, to a lesser extent, New Zealand. These regions, particularly South America, acted as glacial refugia and sources for multiple waves of post‐glacial dispersal. Main conclusions: The blue‐eyed shag paradox is resolved, with at least two waves of dispersal, linked to interglacial cycles, explaining the current distribution and diversity. Descendants of a Pliocene or Early Pleistocene wave of dispersal out of South America survive in the New Zealand region. In contrast, taxa distributed on sub‐Antarctic islands originated much later, possibly since the Last Glacial Maximum. Blue‐eyed shags therefore represent a powerful model system—comprising several natural replicates—for studying the early stages of founder‐event speciation and adaptation in a Southern‐Ocean bird group. [ABSTRACT FROM AUTHOR]

Testate protists in the genus Gromia ('gromiids', supergroup Rhizaria) are common and diverse in marine settings. However, their ecological significance is not well understood, partly because they remain largely undescribed with most records being of the type species, G. oviformis. To enhance our knowledge of gromiid biodiversity, we use morphological and genetic data to describe four new species with tests of different shapes from sublittoral depths (21–136 m) in South Georgia fjords: G. pashukae (ovate), G. landrethi (spherical), G. amygdaliformis (almond-shaped), and G. saoirsei (elongate), maximum lengths 3.4, 2.5, 1.4 and 4.5 mm, respectively. We also describe two smaller (~1 mm) gromiid species from intertidal sites on the Falkland Islands: G. cedhageni (ovate test with finely granular, orange-coloured contents), and Gromia psammophila (subrectangular test with numerous small mineral grains embedded in pale, finely granular material). Gromia landrethi is also represented by DNA sequences from specimens collected in Ushuaia (Argentina) and G. psammophila by sequenced specimens from southern Chilean fjords, but the other species are known only from localities in South Georgia or the Falkland Islands. Analysis of partial SSU rRNA genes confirms the presence of these six new species, as well as an undescribed species represented by a clade of three sequences branching separately. Our results increase the number of described gromiid species from 10 to 16, and underline the importance of these poorly known relatives of the foraminifera in higher-latitude intertidal and fjord settings. [ABSTRACT FROM AUTHOR]

Hexacorals are important components of macrobenthic communities in the Southern Ocean, dominating Antarctic continental shelves. Most of the 119 sea anemones recorded for the Southern Ocean are endemic (81% and 25% endemic species and genera, respectively, one endemic family) with only two species extending beyond the limits of the Southern Ocean. Over 70% of the 83 genera in the Southern Ocean are monotypic, including half of the generic diversity in superfamily Actinostoloidea, which suggests that Antarctica has been isolated long enough for the evolution of new genera but not for many families to evolve. Here, we describe Chitinactis marmara gen. & sp. nov. , a new monotypic actinostoloidean genus from Antarctica diagnosed by its unique bi-layered cuticle on column, hexamerous symmetry, unequal development of younger mesenteries and mesogleal tentacle musculature. We also re-describe and extend the geographic distribution of Scytophorus striatus , another endemic Antarctic species. Based on morphological and molecular data, we establish the phylogenetic position of C. marmara and discuss the implications of the phylogenetic position of S. striatus for the resurrection and circumscription of the family Halcampoididae and the evolution of burrowing sea anemones. Finally, we discuss evidence for an actinostoloidean deep-sea, polar lineage of burrowing sea anemones. [ABSTRACT FROM AUTHOR]

The isolated sub-Antarctic islands are of major ecological interest because of their unique species diversity and long history of limited human disturbance. However, since the presence of Europeans, these islands and their sensitive biota have been under increasing pressure due to human activity and associated biological invasions. In such delicate ecosystems, biological invasions are an exceptional threat that may be further amplified by climate change. We examined the invasion trajectory of the blowfly Calliphora vicina (Robineau-Desvoidy 1830). First introduced in the sub-Antarctic Kerguelen Islands in the 1970s, it is thought to have persisted only in sheltered microclimates for several decades. Here, we show that, in recent decades, C. vicina has been able to establish itself more widely. We combine experimental thermal developmental data with long-term ecological and meteorological monitoring to address whether warming conditions help explain its current success and dynamics in the eastern Kerguelen Islands. We found that warming temperatures and accumulated degree days could explain the species’ phenological and long-term invasion dynamics, indicating that climate change has likely assisted its establishment. This study represents a unique long-term view of a polar invader and stresses the rapidly increasing susceptibility of cold regions to invasion under climate change.