The population structure and demography of an intertidal gastropod Lunella correensis around the Japanese Archipelago affected by past environmental change

Understanding how population structure and demography are determined is a central theme in marine biogeography. While historical events, such as past climate change, are important determinants, the mechanisms by which they act are not well understood in many marine species. In this study, the population structure of the Japanese, marine intertidal gastropod Lunella correensis was investigated to determine whether it has been affected by past environmental changes. A genome-wide SNP analysis, L. correensis showed a genetic gradient along the coast and a weak genetic differentiation between sites in the Sea of Japan and the Pacific Ocean. Demographic inference suggests that the effective population size expanded and shrunk in response to periods of rapid warming and cooling due to past climate change. Further, ecological niche modelling suggests that the population size of L. correensis increased by advancing into the Sea of Japan during rapid warming after the Last Glacial Maximum. Notably, our analyses suggest that recent human activities may have influenced the effective population size of this species. Specifically, the period of reduction in the population size coincides with environmental changes and habitat loss associated with development along the Japanese coastal area. Thus, these results emphasize that the genetic structure and demography of marine species have been influenced by past environmental change around the Japanese Archipelago.