【Oral Presentation】How Geotopology and Ecology Affect Genetic Structure: Insights from Seascape Genetics of Marine Snails

In general, marine ecosystems are characterized by a higher level of gene flow among local populations compared to terrestrial systems.However, accumulated molecular studies have demonstrated that various marine species can be genetically differentiated.Naturally, coastlines are not just straight stretches, but also consist of complex structures such as bays, capes, and various shores.For instance, exposed shores are constantly subjected to the effects of strong waves, while sheltered areas, such as inner bays, are not.These differences in geotopology (the structure of the coastline) provide various types of coastal habitats for marine species.In this context, the principal goal of seascape genetics is to understand how coastlines, fringed by various environments, affect genetic population connectivity.Here, I focus on the relationships between geotopology and the genetic structure of marine species.Firstly, I demonstrate a comparative phylogeography of co-distributed intertidal snails with different habitat usage patterns concerning complex coastlines such as sheltered bays and exposed shores.Based on the results, I discuss whether the specialist-generalist variation hypothesis is valid in the marine environment.Specifically, habitat specialists that prefer certain coastal environments tend to be genetically differentiated and have low genetic diversity.Next, I introduce our recent work in seascape genetics along the Sanriku coast in the Tohoku District of Japan.The Sanriku coast presents an interesting seascape transition between a relatively smooth coastline and a complex rias coast.To examine the influence of coastline complexity on genetic structure, a high-resolution genome-wide SNPs dataset was obtained by ddRAD-seq from two direct-developing snail species.The results demonstrate that a common genetic boundary of the two species coincides with the seascape transition.Finally, I emphasize the importance of comparing various taxonomic groups within the same seascape to better understand the relationships between coastal geotopology and speciesspecific ecological traits on genetic structure.