Subdividing the Common Intertidal Hermit Crab Pagurus minutus Hess, 1865 (Decapoda: Anomura: Paguridae) Based on Molecular, Morphological and Coloration Analyses.

Jibom Jung, Jongwoo Jung, and Won Kim (2018) A phylogenetic study was conducted to investigate whether distinct genetic groups are present within the East Asian Pagurus minutus. In this study, 167 individuals of P. minutus were collected along the coasts of South Korea, east coast of Honshu, west coast of Kyushu, Okinawa Islands of Japan, and Taiwan. The collection of P. minutus was divided into three groups based on the differences in cytochrome c oxidase subunit I (COI) sequences and morphological and color characters: Major Group (MAG), Minor Group (MIG), and Taiwan-Okinawa Group (TOG). MAG commonly inhabits the entire coast of South Korea (except for the northeast coast), east coast of Honshu, and west coast of Kyushu in Japan. MIG predominantly inhabits the northeast coast of South Korea, while a small proportion inhabits the west coast of South Korea and west coast of Kyushu in Japan. TOG is restricted to Taiwan and the Okinawa Islands of Japan. The COI divergence among MAG, MIG, and TOG was larger than the minimum interspecific divergence of the other Pagurus species. Little ingroup COI divergences exist in the MAG and MIG, but distinct ingroup COI divergence is present between the two subgroups of TOG inhabiting Taiwan and Okinawa Islands. MAG, MIG, and TOG show minor differences among morphological characters. Each specimen of these three groups has distinguishing color patterns. These differences in molecular, morphological and color characters suggest that P. minutus are separated into three groups at the species level, and this subdivision of P. minutus shows that additional phylogenetic studies of other hermit crabs and common marine decapod species in East Asia are needed.