Tethyan closure drove tropical marine biodiversity: Vicariant diversification of intertidal crustaceans

Abstract Aim: The mid-Miocene closure of the Tethys (Terminal Tethyan Event, TTE) induced by the collision of the African–Arabian plate with the Eurasian plate is considered to be a major driver of tropical marine biodiversity. We used intertidal talitrids of Talorchestia sensu lato to test the hypothesis that the TTE can best explain the current disjunct distribution of this genus along Mediterranean-East Atlantic and Indo- West Pacific coastlines. Location: Mediterranean-East Atlantic and Indo-West Pacific. Methods: We sequenced four nuclear and two mitochondrial loci for 87 samples across the Mediterranean-East Atlantic to Indo-Pacific areas. We examined phylogenetic relationships, estimated divergence times and reconstructed ancestral geographical distributions of Talorchestia sensu lato within a wide geographical context. Results: The phylogenetic analyses revealed that Talorchestia sensu lato is monophyletic. Divergence time estimation and ancestral range reconstruction show that the genus originated from the Tethys during the Miocene and split into Mediterranean- East Atlantic and Indo-West Pacific lineages c. 15 Ma. The Mediterranean- East Atlantic lineage further diverged into west and east Mediterranean clades, and the Indo-West Pacific lineage contains Indian Ocean and west Pacific clades. Main conclusions: The evolutionary history of Talorchestia sensu lato corresponds well with the geological history of Tethyan closure, suggesting that the Tethyan closure drove the vicariant diversification of Talorchestia sensu lato into Mediterranean- East Atlantic and Indo-West Pacific lineages. This indicates that the intertidal environment may be the last to be separated by the TTE, and the diversification pattern of intertidal crustaceans can best reflect the vicariance effect of Tethyan closure. Deep divergences within clades were related to geological isolation in the Mediterranean- East Atlantic region and across the Indo-Pacific boundary.