Antarctica as an evolutionary arena during the Cenozoic global cooling

International audienceIt is striking to observe that species richness is not evenly distributed across the surface of the planet. Current species diversity indeed decreases toward the poles, with Antarctica for instance being depauperate compared to tropical regions. This ubiquitous pattern has long attracted the attention of naturalists and more recently of evolutionary biologists and paleontologists to understand why species diversity peaks at the equator. However, it remains poorly understood how polar biodiversity originated and diversified. Antarctica is currently defined as three large biogeographic regions: the Maritime Antarctic, the sub-Antarctic, and the Continental Antarctic. The Maritime Antarctic region is largely separated from the rest of the world’s oceans due to the Antarctic Circumpolar Current (ACC), differences in temperature along the Antarctic Polar Front (APF), and the presence of a deep sea surrounding the Antarctic shelf (1). The sub-Antarctic region consists of dozens of islands contained within the APF, generally characterized by the presence of tundra (absent from the Continental Antarctic) and fellfield habitats. As for the Continental Antarctic region, it is mostly uninhabitable, with less than 0.5% of its surface being ice-free. A long-standing idea is that biodiversity in Antarctica is low, and only constituted of old and poorly diversified lineages. In PNAS, a study (2)—relying on both microevolutionary and macroevolutionary approaches—challenges this idea and shows that terrestrial life can thrive there