Genome scan of the mitten crab Eriocheir sensu stricto in East Asia: Population differentiation, hybridization and adaptive speciation

Abstract

We examine the genetic structure and evolutionary history of the mitten crab Eriocheir sensu stricto in East Asia by employing a genome scan – amplified fragment length polymorphism. Population analysis reveals three divergent clades in Eriocheir s. s., which dominate the East China Sea–Yellow Sea, the Sea of Japan (plus Okinawa) and the South China Sea, respectively, mostly in agreement with our previous mtDNA analysis. With the tropical South China Sea inferred as the origin, the East China Sea–Yellow Sea and the Sea of Japan clades in the north diverged successively from the ancestral clade during the mid-Pleistocene. The divergence of the three clades likely resulted from isolation of the three marginal seas caused by sea level change in the Pleistocene. Two sympatric zones, one of the East China Sea–Yellow Sea and the South China Sea clades in southeast China and the other of the East China Sea–Yellow Sea and the Sea of Japan clades in Vladivostok, are demonstrated to be hybrid zones, with hybridization occurring currently in the former but historically in the latter. Adaptive speciation is observed in the divergence process of the three clades, possibly because of selection from accumulated temperature. Our study indicates that the genetic structure and evolutionary history of Eriocheir s. s. have been primarily affected by Pleistocene glacial cycles, secondarily by divergent selection and drainage isolation, but only minimally by human activities.