Comparative seascape genetics of co-distributed intertidal snails Monodonta spp. In the Japanese and Ryukyu archipelagoes

Recent molecular ecological studies have focused on how the relationships between physical and ecological factors influence marine biogeography. Comparative phylogeography using closely related species is a powerful approach to evaluate the role of ecological traits in the genetic variation of marine organisms. In the present study, we compared ecological traits and genetic variation in 3 species of the intertidal snail genus Monodonta that co-occur in the Japanese and Ryukyu archipelagoes. We found that M. labio was dominant in sheltered habitats and M. perplexa was dominant in wave-exposed habitats, while M. confusa showed no habitat specificity. This indicates that M. labio and M. perplexa are habitat specialists regarding wave exposure, while M. confusa is a generalist. M. labio and M. perplexa showed lower genetic diversity and greater genetic differentiation among populations than M. confusa. Our findings support the specialist-generalist variation hypothesis in a well-connected marine environment.