Genetic population structure of the rare brackish-water crab Ptychognathus ishii Sakai, 1939 (Varunidae) on the Japanese coast

Abstract

Genetic population structure of the rare brackish-water crab Ptychognathus ishii Sakai, 1939 (Varunidae), was investigated based on specimens from ten localities in southwestern Japan from Shizuoka Prefecture to Okinawa Prefecture. Significant genetic differentiation was detected among many local populations, with the most remarkable difference between populations on the Japanese mainland and those on smaller islands, such as Tsushima Island, Kakeroma Island, and Okinawa Island. Additionally, genetic differentiation was found between some local populations on the mainland. Results of a neutrality test, divergence time estimation, and mismatch distribution results suggest that mainland populations diverged from the population in Okinawa after divergence of the Kakeroma and Tsushima populations.