Evolutionary history of Old World cellar spiders in the context of Neo-Tethyan sea-land transformations

The ancient Neo-Tethyan region underwent profound tectonic transformations, including the orogenesis of the Xizang Plateau and the westward retreat and ultimate closure of the Neo-Tethyan Ocean. These events significantly influenced the diversification and biogeography of aquatic animals. However, the impact of these large-scale sea-land shifts on the long-range evolutionary history of terrestrial fauna remains unclear. This study investigated how geological changes in the Neo-Tethyan region shaped the evolutionary trajectories and dispersal patterns of Pholcus sensu lato cellar spiders across the Old World. Molecular dating, ancestral area reconstructions, and diversity analyses were conducted using sequences from seven genes across 234 samples representing 209 species. Results indicated that these spiders originated in the eastern Neo-Tethyan region during the Early Eocene, with their subsequent diversification driven by a series of concomitant geological events. The Eurasian (ER) Group dispersed into Europe following the westward retreat of the Neo-Tethyan Ocean in the Early Miocene, while the African (AF) Group migrated into Africa via the Arabian Plate land bridge following the closure of the Neo-Tethyan Ocean in the Oligocene. The East Asian (EA) Group, which expanded along the southeastern margin of the Himalayas, experienced explosive diversification in response to sustained orogenesis at the Eocene-Oligocene boundary. These findings illustrate how large-scale geological processes and sea-land changes shaped the evolutionary history of terrestrial fauna in the Neo-Tethyan region.