Phylogenetic Relationships of the Genus Homatula (Cypriniformes: Nemacheilidae), with Special Reference to the Biogeographic History around the Yunnan-Guizhou Plateau

Species of the nemacheilid genus Homatula are endemic to the Yunnan-Guizhou Plateau of China. Herein we provide phylogenetic inferences of species relationships based on complete sequences of the mitochondrial cytochrome b gene (cyt b) and partial sequences of the nuclear recombination activation gene (RAG 1). Both gene trees (and the concatenated data set) support the recognition of five clades in the genus. These analyses also support the hypothesis that two of the lineages resolved represent undescribed species awaiting formal description, and, further, that two previously recognized species are junior synonyms; both are genetically indistinguishable from other previously recognized species. Divergence times of the major clades in Homatula are inferred to be Late Pliocene and the Early Pleistocene, and are correlated with the massive geological events associated with the uplift of the Qinghai-Tibetan Plateau occurring at these times. The reconstruction of drainage histories suggests that the fish faunas of the Nu and Lancang rivers are basal relative to other riverine faunas in the region, and that the Nanpan and the Jinsha rivers share a more recent history than with any other river systems included in our study.