Meta-analysis of Antarctic phylogeography reveals strong sampling bias and critical knowledge gaps

Much of Antarctica’s highly endemic terrestrial biodiversity is found in
small ice-free patches. Substantial genetic differentiation has been
detected among populations across spatial scales. Sampling is, however,
often restricted to commonly-accessed sites, and we therefore lack a
comprehensive understanding of broad-scale biogeographic patterns, which
could impede forecasts of the nature and impacts of future change. Here,
we present a synthesis of published genetic studies across terrestrial
Antarctica and the broader Antarctic region, aiming to identify current
biogeographic patterns, environmental drivers of diversity, and future
research priorities. A database of all published genetic research from
terrestrial fauna and flora (excl. microbes) across the Antarctic region
was constructed. This database was then filtered to focus on the most
well-represented taxa and markers (mitochondrial COI for fauna, and
nuclear ITS for flora). The final dataset comprised 7222 records, spanning
153 studies of 335 different species. There was strong taxonomic bias
towards flowering plants (52% of all floral data sets) and springtails
(54% of all faunal data sets), and geographic bias towards the Antarctic
Peninsula and Victoria Land. Recent connectivity between the Antarctic
continent and neighbouring landmasses, such as South America and the
Southern Ocean Islands (SOIs), was inferred for some groups, but patterns
observed for most taxa were strongly influenced by sampling biases.
Above-ground wind speed and habitat heterogeneity were positively
correlated with genetic diversity indices overall, though environment was
a generally poor predictor of genetic diversity. The low resolution and
variable coverage of data may also have reduced the power of our
comparative inferences. In the future, higher-resolution data, such as
genomic SNPs and environmental modelling, alongside targeting sampling of
remote sites and under-sampled taxa, will address current knowledge gaps
and greatly advance our understanding of evolutionary processes across the
Antarctic region.