MARINE VICTIMS OF ANCIENT HYPERTHERMALS: CLADES, TRAITS AND A REVOLUTION

Modern global warming is expected to negatively and progressively impact particular traits and clades of marine ectotherms, intensifying their risk of extinction. In light of the changing state of the Earth and its ecosystems, we asked whether ancient hyperthermal events of the past 300 million years give consistent patterns of marine victims by their ecological traits and clade membership.

We used the Paleobiology Database to standardize the hyperthermal extinction risk of each trait and clade against its non-hyperthermal average risk of extinction, giving each group a relative hyperthermal vulnerability. Our models account for other strong determinants of extinction risk, including geographical range size and taxonomic grouping (when analyzing traits). We also test for changes to group vulnerability after the mid-Jurassic plankton revolution, which introduced a deep-sea buffer to rapid changes in ocean chemistry.

We found that some traits and clades clearly perform worse than usual in terms of extinction resistance under hyperthermal conditions, including animals with photosymbionts, a higher activity rate, larger body size, habitat preference for reefs, or a deposit feeding diet. Animals with skeletons of aragonite showed a greater relative extinction vulnerability than those with low-Mg calcite or silica skeletons, and bony fishes showed a greater relative extinction vulnerability than cartilaginous fishes. While extinction magnitudes generally decreased after the plankton revolution, this was not universal, with bony fishes remaining vulnerable to hyperthermal conditions.

These fossil extinction responses mirror modern responses of these groups to warming, including range shift magnitudes, population losses, and experimental performance under climate-related stressors. Fossil responses averaged over events with similar hypothesized triggers of extinction may give insight into the mechanisms acting, and a preview of future responses to the same trigger.