Meeting Abstract

P2-30   -   Decoupling speciation and extinction reveals abiotic and biotic drivers shaped 250 million years of diversity on crocodile-line archosaurs Payne, ARD*; Lloyd, GT; Mannion, PD; Davis, KE; Department of Biology, University of York; School of Earth and Environment, University of Leeds; Department of Earth Sciences, University College London; Department of Biology, University of York alexanderrdpayne@gmail.com

Pseudosuchia is a diverse group of archosaurian reptiles that first emerged approximately 250 Ma and occupied a variety of niches and habitats. More than 700 species are known from the fossil record, but the only representatives of the clade alive today are the <30 species of extant crocodylians, which are more morphologically and ecologically constrained than their extinct counterparts. Here we evaluate the roles of both abiotic and biotic factors in pseudosuchian diversification dynamics. With a new time-calibrated tree of >500 taxa, we use a phylogenetic framework to examine the effects of environmental change and clade competition throughout their evolutionary history. These data were partitioned into broad habitat types (marine, freshwater, exclusively terrestrial) to determine whether responses to diversification drivers were ecologically constrained. We model both speciation and extinction rates via our phylogeny and test for correlations between these and three proxies of abiotic factors (palaeotemperature, global eustatic sea level, continental fragmentation), and also within lineage diversity to test for diversity-dependent effects of biotic competition. Our findings suggest that pseudosuchian evolutionary history was shaped by the interplay of biotic and abiotic processes over hundreds of millions of years, though the exact drivers differ between habitat types. Decoupling speciation and extinction reveals a more complex picture of pseudosuchian evolution than previously understood, emphasising the importance of considering more than net diversification or speciation alone. As the number of species threatened with extinction by anthropogenic climate change continues to rise, the fossil record provides a unique window into the likely drivers that led to clade success and those that may ultimately lead to extinction.