Genetic structure of J apanese C hattonella marina ( R aphidophyceae) populations revealed using microsatellite markers

Summary C hattonella marina var. antiqua and C . marina var. marina ( R aphidophyceae) are red tide‐forming, harmful phytoplankton species. We investigated the genetic diversity and genetic relationship among the populations using microsatellite markers to identify putative sources of C . marina var. antiqua and C . marina var. marina in J apanese coastal populations. A positive correlation between genetic divergence and geographical distance (isolation by distance) was recognized for C . marina var. antiqua . The C . marina var. antiqua populations were established throughout a geological time scale, and genetic divergence had progressed in each population with gene flow depending on geographic distances. In contrast, isolation by distance was not observed for C . marina var. marina populations, and the genetic divergence among populations was extremely high. The T okyo B ay population of C . marina var. marina , which was first recognized in 2008, had many private alleles but was related to the K agoshima B ay population. The T okyo B ay population may have been established by several invasions from the K agoshima B ay population and other regions.