The genetic structure of the marine flatwormStylochoplana pusilla(Rhabditophora: Polycladida) and its use of intertidal snails

Abstract

AbstractAlthough marine phylogeographers have accumulated knowledge of the evolutionary history of various invertebrates, there is a large bias among the taxa regarding genetic data. The order Polycladida is a typical example for which little genetic information at population level is available. Here, we focused on the polyclad flatwormStylochoplana pusilla, distributed in the Japanese Pacific coastal area.Stylochoplana pusillais known to have commensal relationships with certain intertidal snails, using snails (mainlyMonodonta confusa) as a refugee house. During low tide,S. pusillahides in the mantle cavity of snails to protect themselves from desiccation and predation. Here, we investigated the genetic structure ofS. pusillausing a mitochondrial Cytochrome Oxidase I marker and the species diversity of snails used by it. We found thatS. pusillahas high genetic diversity of its populations. WhileS. pusillashowed a significant genetic differentiation among populations, it was relatively low. In addition, we also showed thatS. pusillaused several intertidal snail species which inhabit various coastal environments. The present study suggestsS. pusillahas sufficient dispersal ability to connect among its local populations. Also, the range of available snails forS. pusillamay help the connectivity among local populations. We provide important knowledge about this invertebrate taxon with a unique ecology, which has been insufficiently studied.