Evolutionary history of Old World cellar spiders acted as witness of the Neo-Tethyan sea-land changes

One of the most profound ancient sea-land changes on an immense geographic framework took place in a series of crucial tectonic events of the ancient Neo-Tethyan region: from the orogenesis of the Tibetan Plateau to the westward retreat of the Neo-Tethyan Ocean culminating in the eventual closure of the ocean. These changes induced the diversification of aquatic animals and shaped their distribution patterns. However, little is known about how such large-scale sea-land dynamics has shaped the long-range evolutionary history of terrestrial fauna. In this study, we demonstrate how cellar spiders of the genus Pholcus sensu lato from the Old World have evolved and dispersed as a result of geological transformations in Neo-Tethyan history. With the aid of molecular dating, ancestral area reconstructions, and diversity assessments based on sequences of seven genes for 234 samples of 209 species, we found evidence that the spiders had originated from the eastern Neo-Tethyan region in the Early Eocene, and their subsequent diversification was driven by a series of concomitant geological events. More specifically, the Eurasian (ER) Group dispersed to Europe following the westward retreat of the Neo-Tethyan Ocean at the Early Miocene, and the African (AF) Group migrated to Africa via Arabian Plate land bridge following the closure of the Neo-Tethyan Ocean at the Oligocene. Furthermore, the East Asian (EA) Group that made their way along the southeastern margin of the Himalayas experienced explosive diversification in the wake of continuous orogenesis during boundary timeline between the Eocene and Oligocene. This study provides an excellent case study in understanding how large-scale evolutionary history of terrestrial fauna is shaped by the multitude of events unfolded during the sea-land changes in the Neo-Tethyan region.