Trophic network models explain instability of Early Triassic terrestrial communities

Abstract

Studies of the end-Permian mass extinction have emphasized potential abiotic causes and their direct biotic effects. Less attention has been devoted to secondary extinctions resulting from ecological crises and the effect of community structure on such extinctions. Here we use a trophic network model that combines topological and dynamic approaches to simulate disruptions of primary productivity in palaeocommunities. We apply the model to Permian and Triassic communities of the Karoo Basin, South Africa, and show that while Permian communities bear no evidence of being especially susceptible to extinction, Early Triassic communities appear to have been inherently less stable. Much of the instability results from the faster post-extinction diversification of amphibian guilds relative to amniotes. The resulting communities differed fundamentally in structure from their Permian predecessors. Additionally, our results imply that changing community structures over time may explain long-term trends like declining rates of Phanerozoic background extinction.

Extinction as the loss of evolutionary history

“…The results imply that the trophic structure of extinction may influence the tempo and pattern of recovery. More detailed computer simulations of the effects of both productivity loss and resulting secondary extinctions through a food web further emphasizes the importance of the network structure in the pattern of extinction (65,66). Although the significance of these results is limited because of the lack of empirical input into the food web structure, it suggests something of the insights that may eventually result.…”

Provincialization of terrestrial faunas following the end-Permian mass extinction

“…The end-Permian event had a devastating effect on global biodiversity, with estimates of over 90% species extinction among marine invertebrates and over 70% in terrestrial animals (but significantly less among plants) (3)(4)(5)(6)(7)(26)(27)(28). Recent work has suggested that recovery was delayed because of prolonged environmental disturbance, manifested by wide fluctuations in the global carbon cycle that persisted for most of the Early Triassic (13,29), and that substantial ecosystem diversity was not regained until about 8-million-years later in the Middle Triassic (12,13,30,31). On land, the recovery of terrestrial vertebrates has been studied extensively in the Karoo Basin of South Africa.…”

“…Data for the Lower Triassic "disaster interval" are more limited, but suggest a relatively cosmopolitan tetrapod fauna with Lystrosaurus as its hallmark. Thus, the transition from widespread to endemic tetrapod assemblages did not directly stem from the extinction event, but instead coincided with the restoration of ecological stability during the recovery process (30,35) …”

Palaeobiology: The Cambrian smorgasbord

“…"There could alternatively be fundamental pathways of web assembly that are favoured over others, either by selection at the species level, or selection at the food-web level itself. " Roopnarine says that his reconstructions hint at long-term community-level selection based on species' dietary ranges 4 .…”