Molecular phylogeny and historical biogeography of the cave fish genus Sinocyclocheilus(Cypriniformes:Cyprinidae)in southwest China

Modern accumulations of genetic data offer unprecedented opportunities for understanding the systematic classification and origins of specific groups of organisms.The genus Sinocyclocheilus is among the most cave abundant genera in Cyprinidae,with 76 recognized species,belonging to 4 species groups.Recent phylogenetic studies have shown that the classification of species groups within the genus Sinocyclocheilus remains controversial.In this study,we constructed a sequence supermatrix of 26 species from 4 species groups of the genus Sinocyclocheilus using the mitochondrial genome to reveal phylogenetic relationships,historical biogeography and patterns of species diversification in the genus Sinocyclocheilus.Phylogenetic analysis strongly supports the monophyletic groups of the 3 species groups(S.jii,S.cyphotergous,and S.tingi groups)except the S.angularis group.Phylogenetic analysis showed that S.anshuiensis and S.microphthalmus,which were recognized as numbers of S.angularis group,formed a strongly supported independent clade.Therefore,we propose a new species group,the S.microphthalmus group,which contains S.anshuiensis and S.microphthalmus.Biogeographic reconstruction suggests that the living Sinocyclocheilus may have originated in north-central Guangxi at the late Eocene and dispersed outward after a vicariance at 32.31 Million years ago(Ma).Early diversification is focused on the late Oligocene(ca.25 Ma),which is related to the second uplift of the Qinghai−Tibetan Plateau and the lateral extrusion of the Indochina at the Oligocene/Miocene boundary.Our results suggest that 2 uplifts of the Qinghai−Tibetan Plateau and climate change in the Miocene may have influenced the diversification of the Sinocyclocheilus lineage.