Biogeography of land snail genus Acusta (Gastropoda: Camaenidae): Diversification on East Asian islands

  • 2022-11-07
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In this study, we inferred the evolutionary history of the land snail genus Acusta (Gastropoda: Camaenidae) by a molecular phylogeny and investigated how the palaeogeographic events shaped species diversity and the distribution of the Acusta genus in the continents and islands in East Asia. Our results suggested that currently recognized species in Acusta are polyphyletic. The traditionally accepted concept of the affinity of Acusta and Bradybaena is not supported. The hypothesis of colonization via land bridges during the Pleistocene glaciations for the biota of East Asian islands is not supported. Instead, the origin and diversification of the genus Acusta was dated to the late Miocene–Pliocene from an area around North and Northeast China to South China and East Asian islands. We identified three major evolutionary lineages. Two of the major lineages demonstrate distinct evolutionary histories. As sympatric speciation is the major speciation process for the continental clade, the insular clade originated from founder events. Taiwan functioned as an important source of diversification for species on the East Asian islands possibly through passive dispersal of different mechanisms. The sea level fluctuations caused by the Pleistocene glacial cycles play a role in the subsequent dispersion and diversification of species of the continental clade.