Increase in sea-level and shelf area positively influenced the development of Cenozoic biodiversity hotspots by modulating turnover rate in marine benthos
Marine biodiversity is unevenly distributed across the oceans, with exceptional concentrations of species richness confined to a few hotspots. Fossil and molecular evidence indicate that marine hotspots have shifted among ocean basins throughout the Cenozoic, but the mechanisms underlying their emergence and persistence have rarely been tested across multiple marine groups. Using standardized fossil occurrence data for molluscs, cnidarians, and foraminifera, we identified marine biodiversity hotspots through the past 66 million years. We then apply a multistep framework linking environmental drivers (sea surface temperature (SST), shelf area, and sea level) to clade-specific macroevolutionary processes (origination, extinction, and immigration) to evaluate the dynamics of these hotspots. Our results reveal contrasting evolutionary dynamics across marine biodiversity hotspots of different marine groups. Benthic groups: Mollusca and Cnidaria exhibit higher evolutionary turnover in hotspots than in non-hotspot regions, whereas planktic foraminifera maintain high diversity through reduced extinction and immigration rates. Increase in the sea level and shelf area positively contribute to the development of hotspot by increasing the origination rate in mollusca and cnidaria. Our study offers an integrative framework for understanding how marine biodiversity hotspots arise through a network of interacting processes: environmental drivers shape macroevolutionary dynamics, which in turn generate clade-specific diversity trajectories; together, these processes determine whether a particular region develops into a biodiversity hotspot.