Extinction cascades, community collapse, and recovery across a Mesozoic hyperthermal event

Mass extinctions are considered classic Court Jester drivers of macroevolution in which abiotic pressures trigger suites of extinctions and large ecosystem changes. Most work has ignored species interactions and community structure, limiting inference about which and why species go extinct and how Red Queen processes linking speciation to extinction rates affect recovery of biodiversity, structure and function. Here, using network reconstruction, secondary extinction modelling and community structure analysis, we investigate the Early Toarcian (Lower Jurassic; 183 Ma) Extinction Event and recovery. Primary extinctions targeting infaunal guilds that propagate secondary extinction cascades to higher trophic levels best reproduce the empirical post-extinction community. The event caused a shift from a diverse community with high functional redundancy to a less diverse, more densely connected community of generalists. Recovery saw some elements of community structure and function return to pre-extinction levels before biodiversity recovered. Full ecosystem recovery took about 7 million years, after which we detect markedly increased vertical structure associated with the Mesozoic Marine Revolution and features of modern marine ecosystems.

Alexander M. Dunhill, Karolina Zarzyczny, Jack O. Shaw, Jed W. Atkinson, Crispin T. S. Little, Andrew P. Beckerman