Impact of glacial cycles and ocean currents on radiation events in the Japanese turban snail <i>Lunella coreensis</i>

Abstract The Japanese turban snail Lunella coreensis is sensitive to ocean currents due to its short pelagic larval stage and moderate dispersal ability, making it an ideal model for studying genetic diversity shaped by paleoclimatic shifts. In this study, we analyzed the mitochondrial genes COI and 12S of museum samples collected from various coasts across Japan and identified 10 haplogroups divided into Pacific Ocean and Japan Sea clades, influenced by Kuroshio and Tsushima currents. Divergence time estimates indicate radiation between 3000 and 77,000 yr ago, coinciding with the last ice age, supported by fossil evidence in Japan. Glaciation cycles likely caused genetic isolation and exchange. Rapid radiation between 18,000 and 1000 yr ago aligns with climatic changes during the last glacial maximum. Effective population size estimates indicate past bottlenecks. These findings reveal how historical environmental events shaped L. coreensis genetic diversity, laying the groundwork for future sclerochronological research on marine biodiversity.