Mass extinctions drove increased global faunal cosmopolitanism on the supercontinent Pangaea

David J Button,Richard J Butler,Martín D Ezcurra,Graeme T Lloyd

doi:10.1038/s41467-017-00827-7

Abstract

Mass extinctions have profoundly impacted the evolution of life through not only reducing taxonomic diversity but also reshaping ecosystems and biogeographic patterns. In particular, they are considered to have driven increased biogeographic cosmopolitanism, but quantitative tests of this hypothesis are rare and have not explicitly incorporated information on evolutionary relationships. Here we quantify faunal cosmopolitanism using a phylogenetic network approach for 891 terrestrial vertebrate species spanning the late Permian through Early Jurassic. This key interval witnessed the Permian–Triassic and Triassic–Jurassic mass extinctions, the onset of fragmentation of the supercontinent Pangaea, and the origins of dinosaurs and many modern vertebrate groups. Our results recover significant increases in global faunal cosmopolitanism following both mass extinctions, driven mainly by new, widespread taxa, leading to homogenous ‘disaster faunas’. Cosmopolitanism subsequently declines in post-recovery communities. These shared patterns in both biotic crises suggest that mass extinctions have predictable influences on animal distribution and may shed light on biodiversity loss in extant ecosystems.

Highlights

Mass extinctions have profoundly impacted the evolution of life through reducing taxonomic diversity and reshaping ecosystems and biogeographic patterns
It may be difficult or impossible to apply to a global fossil record dominated by singletons, as is common for tetrapods
The results demonstrate the evolution of relatively cosmopolitan ‘disaster faunas’ following both the Permian–Triassic and Triassic–Jurassic mass extinctions, suggesting that mass extinctions may have common biogeographical consequences

Summary

Introduction

Mass extinctions have profoundly impacted the evolution of life through reducing taxonomic diversity and reshaping ecosystems and biogeographic patterns. We quantify faunal cosmopolitanism using a phylogenetic network approach for 891 terrestrial vertebrate species spanning the late Permian through Early Jurassic This key interval witnessed the Permian–Triassic and Triassic–Jurassic mass extinctions, the onset of fragmentation of the supercontinent Pangaea, and the origins of dinosaurs and many modern vertebrate groups. This study did not include the critical immediate post-extinction faunas (earliest Triassic), and it is unclear whether this regional signal is representative of global biogeographic trends This network method uses only the binary presence–absence data—i.e., information on whether a given species was present (and sampled) within a given locality or not. Lower values of pBC indicate greater endemism, and increased phylogenetic disparity between sets of species from pairs of localities This method was applied using an informal supertree (Fig. 2a; Supplementary Note 1) and species-level occurrence data set of terrestrial amniotes ranging from the late Permian to late Early Jurassic Barriers to dispersal might be perceived as sparse on a supercontinent, numerous studies have suggested faunal provinciality and endemism on Pangaea, perhaps driven by climatic variation[3, 9, 11,12,13]

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Results

Conclusion