Modeling the Role of Primary Productivity Disruption in End- Permian Extinctions, Karoo Basin, South Africa

The end-Permian mass extinction is well-known as the most severe mass extinction of the Phanerozoic. Terrestrial communities appear to have been strongly affected by the event, but the cause of the extinction remains enigmatic. Here we explore whether primary producer disruption (e.g., extinction of terrestrial plants) could have led to a collapse of end-Permian terrestrial ecosystems, using models of probabilistic trophic networks. Based on a trophic network reconstructed for the Dicynodon Assemblage Zone community of the Karoo Basin, we show that late Permian terrestrial communities were vulnerable to collapse brought about by the disruption of primary producers. However, relatively high levels of primary producer loss are needed to account for observed levels of extinction among consumers in the Dicynodon zone fauna. Depending on network parameters, we predict that a shutdown of 69% to 87% of primary producers would be needed to generate observed extinction levels. A disruption of this magnitude is not unreasonable, given that terrestrial floras underwent a major turnover at the end of the Permian, and our predictions can be tested by further scrutiny of floras from this time.