Climate Change and Mass Extinction Risk in an Endemic-Rich Late Devonian Fauna

The fossil record can illuminate factors that contribute to extinction risk during times of global environmental disturbance; for example, inferred thermal tolerance is an important predictor of extinction during several mass extinctions that corresponded with climate change1,2. Additionally, members of geographically isolated biotas may face higher risk because they have less opportunity to migrate to suitable climate refugia during environmental disturbances. Here, we investigate how these two types of risk intersect in the well-preserved brachiopod fauna of the Appalachian Foreland Basin during the two pulses of the Frasnian-Famennian mass extinction (Late Devonian, ~372 Ma3,4). The selectivity of extinction supports climate change (cooling) as the primary kill mechanism in this fauna, with warm-adapted taxa going extinct preferentially. Overall, the extinction was mild relative to other regions, despite the many endemic species. However, taxa that were vulnerable to climate change went extinct more rapidly, during the first extinction pulse, such that the second pulse was insignificant. These results suggest that vulnerable taxa in geographically isolated biotas face heightened extinction risk at the initiation of environmental stress, but that other regions may “catch up” if environmental stress repeats or intensifies.