MODELING TERRESTRIAL FOOD WEB COLLAPSE IN THE END-PERMIAN EXTINCTION

The end-Permian extinction was the most severe mass extinction of the Phanerozoic, yet its causes remain mysterious. Here we use probabilistic food web models to explore how disruption of primary production could have caused the collapse of end-Permian terrestrial ecosystems. First, we simulate food webs (trophic networks) reconstructed for the Late Permian Dicynodon Assemblage Zone community of the Karoo Basin. Next, we perturb combinations of guilds in these food webs using simulated extinctions of taxa at varying levels of intensity. This probabilistic forward model allows us to estimate the effects of such perturbations on terrestrial communities.

We then use Bayesian modeling and Markov Chain Monte Carlo (MCMC) techniques to solve the inverse problem: namely, inferring the level of perturbation responsible for the Permian extinction, as well as the pattern of extinction among guilds. Preliminary results suggest that the extinction was bottom-up, implying that disruption of primary production was responsible for the collapse of late Permian terrestrial communities. Furthermore, relatively high levels of primary production loss are needed to account for observed levels of extinction among Karoo Basin consumers.