The morphological traits and mitochondrial genes of sympatric sea slaters from the genus Ligia were analysed from samples collected along northeastern coastal China and adjacent coastal East Asia to assign the species and to obtain interpretations of their distributions. Using 338 sequences and 199 diagnoses of 16S polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) from 331 specimens sampled from 26 localities, and homological sequences from counterparts from South Korea and the west coast of the USA, we assigned these taxa into two distinct species, Ligia exotica and Ligia cinerascens. Both species are recovered as two monophyletic clades in the robust phylogenetic hypothesis presented here. The northern boundaries of these species in China and the Korean peninsula are more southern than those of counterparts in Japan. Ligia exotica in northeastern coastal China is further split into two geographical subclades (B1 and B2), coexisting near 35°N. The distribution range of L. cinerascens covers the whole range of L. exotica subclade B1. Counterparts in Japan show a similar pattern. Oceanic rafting, shipping, damming and planting of seaweed are proposed as the media for the contemporary connectivity among populations of Ligia species inhabiting coastal China.
Aims:The biodiversity of tropical islands is a popular topic in global biodiversity conservation research. Hainan Island is the largest tropical island in China. Freshwater crabs are a keystone species for freshwater ecosystems in Hainan Island. The aims of this study were thus to identify the distribution pattern and assess the threat status of freshwater crabs in Hainan Island. Methods: In this study, we used field surveys and conducted a literature review to investigate the species diversity and conservation status for freshwater crabs in Hainan. Results: Our results indicate that the diversity hotspots for freshwater crab species on Hainan Island are located in the south-central mountainous area (especially Bawangling, Yinggeling, Mihouling, Wuzhi Mountain, Diaoluo Mountain and Jianfengling). Freshwater crab diversity is higher in the central and southern mountains and lower in the plains. According to the IUCN Red List Categories and Criteria, 16.7% of freshwater crab species on Hainan Island are
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