Abstract
Organismic groups vary non-randomly in their vulnerability to extinction. However, it is unclear whether the same groups are consistently vulnerable, regardless of the dominant extinction drivers, or whether certain drivers have their own distinctive and predictable victims. Given the challenges presented by anthropogenic global warming, we focus on changes in extinction selectivity trends during ancient hyperthermal events: geologically rapid episodes of global warming. Focusing on the fossil record of the last 300 million years, we identify clades and traits of marine ectotherms that were more prone to extinction under the onset of six hyperthermal events than during other times. Hyperthermals enhanced the vulnerability of marine fauna that host photosymbionts, particularly zooxanthellate corals, the reef environments they provide, and genera with actively burrowing or swimming adult life-stages. The extinction risk of larger sized fauna also increased relative to non-hyperthermal times, while genera with a poorly buffered internal physiology did not become more vulnerable on average during hyperthermals. Hyperthermal-vulnerable clades include rhynchonelliform brachiopods and bony fish, whereas resistant clades include cartilaginous fish, and ostreid and venerid bivalves. These extinction responses in the geological past mirror modern responses of these groups to warming, including range-shift magnitudes, population losses, and experimental performance under climate-related stressors. Accordingly, extinction mechanisms distinctive to rapid global warming may be indicated, including sensitivity to warming-induced seawater deoxygenation. In anticipation of modern warming-driven marine extinctions, the trends illustrated in the fossil record offer an expedient preview.
Highlights
Climate change is expected to push some groups of species closer to extinction while others may abide the change (Dunhill et al, 2018; Knoll et al, 2007; Reddin et al, 2020)
Given the challenges presented by anthropogenic global warming, we focus on changes in extinction selectivity trends during ancient hyperthermal events: geologically rapid episodes of global warming
Focusing on the fossil record of the last 300 million years, we identify clades and traits of marine ectotherms that were more prone to extinction under the onset of six hyperthermal events than during other times
Summary
Climate change is expected to push some groups of species closer to extinction while others may abide the change (Dunhill et al, 2018; Knoll et al, 2007; Reddin et al, 2020). More work is needed to establish which groups are uniquely at risk of extinction under global warming, which is essential information for prediction and setting modern conservation priorities To test these hypotheses, we quantify hyperthermal vulnerability of marine metazoan ectotherm clades and traits over the past 300 million years using fossil occurrences from the Paleobiology Database (PaleoDB, https://paleobiodb.org). The difference of this average hyperthermal selectivity and the respective baseline selectivity quantifies how much more likely a taxon is to go extinct during a hyperthermal, based on its clade membership or trait, than it is under non-hyperthermal conditions This difference, which we term relative hyperthermal vulnerability (RHV), places groups with high and low typical rates of turnover, for example, ammonites versus scleractinian corals, on an equal footing, and emphasizes patterns that are exclusive to hyperthermal events. We explicitly control for geographic range size and clade membership, which are among the strongest predictors of extinction risk through geological time (Finnegan et al, 2015)
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