Phylogeography And Conservation Of The Potamid Freshwater Crabs Of Hainan Island,China

Of the 1300 known freshwater crab species,nearly 30 percent inhabit islands or archipelagos.Islands are therefore typical regions to study the evolutionary processes underlying diversification and modern patterns of freshwater crab biodiversity.Here,we focus on potamid freshwater crabs of Hainan Island.Field investigation and collection were conducted across the entire distribution of the Potamidae,in which three ecologically and morphologically diverged genera are recognized(Apotamonautes,Neotiwaripotamon and Hainanpotamon).Species diversity and weighted richness per 0.2� cell indicate that the highest levels are concentrated around central and southern mountain systems and relatively low in peripheral low hills and plains.Based on mitochondrial and nuclear DNA,phylogenetic analyses recovered a monophyletic relationship for the three genus of all potamids on Hainan Island,suggesting a single colonization event for the potamid freshwater crabs to the island.The phylogenetic tree split into two main clades.One clade comprised all four subspecies in the genus Apotamonautes with flat carapaces and large body plan,they inhabited in rivers or streams,and also hided in crevices along riverside or under stones.The second clade is further separated into two subclades corresponding to two different burrowing behaviors,Neotiwaripotamon and Hainanpotamon.Two species were recorded in the former which characterized a little swollen carapaces and long legs.Their larva stages occurred in streams while adults usually in tree holes.Three were described in the latter one which hided in mud holes because of their swollen and convex carapaces.Genetic divergence between species/subspecies within a genus was discordant with morphological affiliation.Ancestral range reconstruction revealed that early diversification of each genus in Hainan Island is heterogeneity in space.These results provide a better understanding of potamid diversification and phylogeography on Hainan Island.Species diversity,genetic diversity and evaluation of conservation status highlight the need for protecting endemic freshwater crab biodiversity.