Ceridwen I. Fraser

Intriguing observations of birds occupying geothermal environments raise the question of whether such areas offer health benefits. Sulfur, a common chemical in geothermal areas, is widely known for its insecticidal and fungicidal properties. We hypothesize that birds may use geothermal environments as a form of environmental parasite management, with such behavior reflected in their activity patterns. We observed and compared the behaviors of 6 bird species at geothermal and non-geothermal sites in Aotearoa (New Zealand). Our observations revealed behavioral differences between the two habitat types. Notably, species such as Cygnus atratus (kakianau or Black Swan) and gulls displayed increased preening behaviors in geothermal areas. These findings offer preliminary, intriguing support for the hypothesis that some birds may select geothermal habitats to aid in parasite control.

The macroalga Macrocystis pyrifera (“giant” or “bladder” kelp) plays a vital role in cold‐temperate marine ecosystems but faces increasing threats from ongoing environmental change. Understanding its population diversity and connectivity is essential for predicting future range shifts and assessing the ecological consequences of such shifts in both present and novel ranges. Here, we used high‐resolution genotyping‐by‐sequencing (GBS) to investigate the population structure of M. pyrifera within and among populations in Aotearoa (New Zealand), Lutruwita (Tasmania), and Falkland Islands/Malvinas. Our results showed New Zealand and Tasmanian populations are more closely related to each other than to those from the Falklands, consistent with isolation by distance. Fine‐scale population structure was detected within each of the three regions, especially New Zealand, where we could pinpoint genetically unique populations down to tens of kilometers. Our research provides insights on fine‐scaled giant kelp diversity and connectivity patterns across three regions in the Southern Hemisphere, which contrast with previous studies that used traditional genetic markers, and will aid future conservation of this ecologically and economically important taxon.

To better understand the ecological consequences of ocean warming on marine ecosystems, experimental manipulation of ecologically relevant parameters is essential. Here, we employed short-term (3 months) in situ heated settlement panel experiments over four seasons to assess the effects of warming on shallow-water (3–5 m depth) encrusting invertebrate communities in a temperate marine ecosystem in New Zealand. Moderate warming (+ 1 °C above ambient) was generally associated with increases in growth, while the effects of greater warming (+ 2 °C above ambient) were more variable and seasonally dependent. Growth rates under a heatwave treatment were often reduced relative to the other heated treatments, with little difference from ambient. Notably, a non-native colonial ascidian, Lissoclinum perforatum emerged as the dominant species in warmed treatments, suggesting its potential to dominate future encrusting communities in this region, even after short-term warming events. For many taxa, increased growth rates did not equate with higher survival probabilities, with some species exhibiting decreased survival even under + 1 °C of warming, despite enhanced growth. Spatial competition within these encrusting communities also shifted in response to warming, with reduced density and complexity observed under + 2 °C of warming. Our experiment shows that even moderate warming, at temperatures already being experienced in marine ecosystems, can substantially alter growth and survival within these assemblages over short time periods and, by extension, benthic community processes and composition. Our findings highlight shifts in spatial competition dynamics that are anticipated to intensify with further ocean warming.

Problem: Rafting is now recognised as a key process influencing the distribution and connectivity of several marine and coastal species. Rafting scenarios are, however, often invoked in ways that do not account for clear differences in biogeographic outcomes. Here, we illustrate the value of utilising multiple lines of evidence (e.g. different life histories, ecologies, and dispersal frequencies) in elucidating the historical, modern, and future significance of ocean rafting. We discuss these issues using a range of exemplar studies from the Southern Ocean, where rafting clearly underlies many different distributional patterns, although our conclusions hold generally.Explanations: Such differences appear to be underpinned by variations in several life‐history characters, with, for instance, direct‐developing taxa more suited to long‐distance rafting events that might span multiple generations. Rafting success is also shaped by a diverse suite of factors including the durability of the raft, the presence/absence of resources and competitors (intra‐ or inter‐specific) at the destination, species' environmental tolerances, latitudinal movements in the position of oceanographic fronts, and the frequency and intensity of extreme events such as storms. Several of these factors are influenced by climate change, so a detailed understanding of their roles is increasingly important—particularly as many species' distributions are shifting.Future Prospects: The Southern Hemisphere—which has considerably more ocean than the Northern Hemisphere (81% vs. 61%)—provides biogeographers with a wealth of information on such processes, as well as intriguing examples of the puzzles we still face. Powerful new tools, including high‐resolution genomic analyses, ancient DNA, and environmental, ecological and oceanographic modelling, are providing a more granular picture of biogeographical patterns. These novel methods, together with a broader consideration of the factors affecting rafting success, can pave the way for an improved and properly integrated understanding of the eco‐evolutionary outcomes of long‐distance dispersal via rafting.

Antarctica harbors many distinctive features of life, yet much about the diversity and functioning of Antarctica’s life remains unknown. Evolutionary histories and functional ecology are well understood only for vertebrates, whereas research on invertebrates is largely limited to species descriptions and some studies on environmental tolerances. Knowledge on Antarctic vegetation cover showcases the challenges of characterizing population trends for most groups. Recent community-level microbial studies have provided insights into the functioning of life at its limits. Overall, biotic interactions remain largely unknown across all groups, restricted to basic information on trophic level placement. Insufficient knowledge of many groups limits the understanding of ecological processes on the continent. Remedies for the current situation rely on identifying the caveats of each ecological discipline and finding targeted solutions. Such precise delimitation of knowledge gaps will enable a more aware, representative, and strategic systematic conservation planning of Antarctica.

What little we know about how microbiomes change over the course of host dispersal has been gleaned from simulations or snapshot sampling of microbiomes of hosts undertaking regular, cyclical migrations. These studies suggest that major changes in both microbiome richness and turnover occur in response to long-distance movements, but we do not yet know how rare or sporadic dispersal events for non-migratory organisms might affect the microbiomes of their hosts. Here we directly examine the microbiomes of rafting seaweed, leveraging host genomic analyses, amplicon sequencing, and oceanographic modelling to study the impacts of ecological dispersal of hosts on their microbiomes. We find that once dislodged from coastal shores and adrift, kelp-associated microbial communities change profoundly—the core microbes found on attached kelp give way to a few abundant taxa and many rare taxa. Changes in microbial species richness and composition are strongly linked to variability in sea surface temperature rather than length of time spent rafting. These changes are associated with increased contributions of neutral processes shaping community assembly. These findings highlight the role of environmental predictability in triggering major community successional changes and challenge the importance of host selection in determining the microbiome.

Large‐scale disturbance events provide ideal opportunities to directly study recolonisation processes in natural environments, via the removal of competitors and the formation of newly vacant habitat. A high magnitude earthquake in central New Zealand in 2016 created major ecological disturbance, with coastal tectonic uplift of up to ~ 6 m extirpating vast swathes of intertidal organisms. One of the affected species was Durvillaea antarctica (rimurapa or southern bull kelp), which is an important habitat‐forming intertidal macroalga capable of long‐distance dispersal. Across the complex fault system with varying amounts of uplift, the species was either locally extirpated or heavily reduced in abundance. We hypothesised that neutral priority effects and chance dispersal from other populations would influence which lineages would establish. We sampled individuals of D. antarctica across the uplift zone immediately after the earthquake in 2016 and then repeatedly sampled new recruits in the same areas between 2017 and 2020, using genotyping‐by‐sequencing to provide ‘before' and ‘after' genomic comparisons. Our results revealed strong geographic clustering but little evidence of new lineages establishing at disturbed sites, although populations at uplifted sites remain at remarkably low densities. We infer that recolonisation has thus far primarily originated from refugial, remnant patches within the uplift zone. To complement the phylogeographic analysis, we estimated oceanographic connectivity among the uplift zone sample locations. The connectivity modelling estimated that northbound dispersal of D. antarctica was more likely, but we have not yet detected southern genotypes in the recolonised populations. As the ongoing recolonisation process transitions from an ecological to an evolutionary timescale, change remains possible. This study provides the first genomic ‘snapshots' of a natural recolonisation process following a large‐scale ecological disturbance event, and ongoing research has the potential to reveal important insight into both micro‐ and macroevolutionary processes.

Polynyas, areas of open water embedded within sea ice, are a key component of ocean–atmosphere interactions that act as hotspots of sea-ice production, bottom-water formation, and primary productivity. The specific drivers of polynya dynamics remain, however, elusive and coupled climate models struggle to replicate Antarctic polynya activity. Here, we leverage a 44-y time series of Antarctic sea ice to elucidate long-term trends. We identify Antarctic-wide linear increases and a hitherto undescribed cyclical pattern of polynya activity across the Ross Sea region that potentially arises from interactions between the Amundsen Sea Low and Southern Annular Mode. While their specific drivers remain unknown, identifying these emerging patterns augments our capacity to understand the processes that influence sea ice. As we enter a potentially new age of Antarctic sea ice, this advance in understanding will, in turn, lead to more accurate predictions of environmental change, and its implications for Antarctic ecosystems.

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. 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.