Multigene Phylogenies of the Estuarine Sesarmid Species Complex (Decapoda: Brachyura: Sesarmidae), with Description of Three New Species

S (De Haan, 1835) is a common intertidal sesarmid crab that inhabits the estuarine and mangrove regions of East Asia, as well as Vietnam and the Philippines. Previous studies have suggested that is a species complex composed of several species. Our findings indicated that the species complex is monophyletic with six clades, as shown by reconstructed phylogenies based on mitochondrial 16S rDNA and cytochrome oxidase subunit I, as well as nuclear 28S rDNA. Specimens of each clade exhibited different characters, including the morphology of the cheliped, anterior carapace, male gonopod 1, and female vulvae, as well as the coloration. Three species in this complex have been previously described: (De Haan, 1835), (Rahayu & Davie, 2002), and Li, Shih & Ng, 2019. Here, we describe three additional species: n. sp., n. sp., and n. sp. Biogeographically, the range of includes the southern margin of Korea, the main islands of Japan, and the Ryukyus, with a comparatively northern distribution. is widely distributed from the continental coasts of southeastern and southern China (including northern Hainan Island) to southern Vietnam and is occasionally found in Penghu, Taiwan. is an insular species distributed from Taiwan main island, the central Philippines, to northern Borneo. Finally, is mainly limited to the Penghu Islands (Pescadores) but is also sometimes found in Taiwan main island and the offshore Gueishan Island.