Antarctic biodiversity is much more extensive, ecologically diverse and biogeographically structured than previously thought. Understanding of how this diversity is distributed in marine and terrestrial systems, the mechanisms underlying its spatial variation, and the significance of the microbiota is growing rapidly. Broadly recognizable drivers of diversity variation include energy availability and historical refugia. The impacts of local human activities and global environmental change nonetheless pose challenges to current and future understanding of Antarctic biodiversity. Life in the Antarctic and the Southern Ocean is surprisingly rich, and as much at risk from environmental change as it is elsewhere.The past two decades have witnessed a revolution in the approaches used to document patterns in and the functional significance of the diversity of life. Knowledge of the global distributions of organisms now extends to many groups. These include terrestrial plants and animals 1 , marine taxa 2 , components of the soil biota 3 , and, increasingly, microorganisms 4 .2 Empirical and theoretical research is verifying the range of mechanisms, including energy and nutrient availability, and historical contingency, that are responsible for these patterns 1,2 , and the role of diversity in maintaining ecosystem services. New approaches are also revealing rapid changes in diversity across most ecosystems, their often negative implications for the future of the planet, and our struggle to address the problem 5 .In tandem, biodiversity research has surged across the Antarctic and Southern Ocean.In part the increasing interest has been driven by the realization that any fundamental quest to understand life's diversity requires exploration of the polar regions 6,7 . But it has also been underpinned by a growing appreciation of the particular challenges faced by Antarctic species and ecosystems. Climate change 8 , and economic activity in the form of fishing, tourism, and scientific research itself 9,10 are all having impacts on Antarctic diversity. The intricacy of Southern Ocean food webs, best known for the region's iconic seals, penguins, whales and albatrosses, has been further unveiled, so highlighting the complexity of the simultaneous impacts of changing climates, sea ice distribution and fisheries on this system 11,12 . New marine research has also exposed unexpectedly high benthic diversity, including in the deep sea 13,14 . In terrestrial areas, the diversity of higher plants and animals is relatively low (e.g., just two flowering plant species), but the diversity of lichens, bryophytes, invertebrates, and the microbiota is substantial 15 . Local and regional spatial patterning in these groups is extensive 16 , with the mechanisms underlying these patterns both recognizable from broader ecological theory and unusual in several respects.Here we explore recent advances in our understanding of the biodiversity of the Antarctic. Given the many conservation challenges it faces, we also consider how well the region i...

Extreme and remote environments provide useful settings to test ideas about the ecological and evolutionary drivers of biological diversity. In the sub-Antarctic, isolation by geographic, geological and glaciological processes has long been thought to underpin patterns in the region's terrestrial and marine diversity. Molecular studies using increasingly high-resolution data are, however, challenging this perspective, demonstrating that many taxa disperse among distant sub-Antarctic landmasses. Here, we reconsider connectivity in the sub-Antarctic region, identifying which taxa are relatively isolated, which are well connected, and the scales across which this connectivity occurs in both terrestrial and marine systems. Although many organisms show evidence of occasional long-distance, trans-oceanic dispersal, these events are often insufficient to maintain gene flow across the region. Species that do show evidence of connectivity across large distances include both active dispersers and more sedentary species. Overall, connectivity patterns in the sub-Antarctic at intra- and inter-island scales are highly complex, influenced by life-history traits and local dynamics such as relative dispersal capacity and propagule pressure, natal philopatry, feeding associations, the extent of human exploitation, past climate cycles, contemporary climate, and physical barriers to movement. An increasing use of molecular data - particularly genomic data sets that can reveal fine-scale patterns - and more effective international collaboration and communication that facilitates integration of data from across the sub-Antarctic, are providing fresh insights into the processes driving patterns of diversity in the region. These insights offer a platform for assessing the ways in which changing dispersal mechanisms, such as through increasing human activity and changes to wind and ocean circulation, may alter sub-Antarctic biodiversity patterns in the future.

Highlights d We recovered genomic data from ancient bears directly from cave sediments d Ancient Mexican black bears are ancestrally related to Eastern American black bears d The Mexican and Yukon populations of extinct giant shortfaced bears were distinct d Our results bring ancient eDNA into the era of population genomics