Molecular Phylogeny Of Three Subspecies Of Schizopygopsis Malacanthus, Based On Sequence Analysis Of Cytochrome B And Mitochondrial DNA Control Region

Schizopygopsis malacanthus belongs to the genus Schizopygopsis, subfamily Schizothoracinae. There are three subspecies of this species, S. malacanthus malacanthus Herzenstein, 1891, S. m. chengi (Fang), 1936, and S. m. baoxingensis Fu, Ding et Ye, 1994. They are distributed in cool and cold water in high mountain rivers, streams and lakes in upper reaches of the Yangtze River, and feed on insects and algae. These three subspecies have many common and overlapping morphological characters. However, they still have some obvious differences in morphology. A phylogenetic analysis of these three subspecies is necessary to test whether classification based on morphological characters is corroborated. It can also help determine the origin of S. m. baoxingensis, which has a very limited distribution range.In 2003-2005, Schizopygopsis malacanthus malacanthus were collected from the Litang River, a tributary of the Yalong River, in Litang County, and from the upper reaches of the Shuiluo River, a tributary of the Jinsha River, in Litang and Daocheng Counties; S. m. chengi were collected from Rangtang region of the Dadu River; S. m. baoxingensis were collected from the East River, a tributary of the Baoxing River located in upper reaches of the Qingyi River. Phylogenetic relationships of the three subspecies were investigated based on the mitochondrial DNA control region and the cytochrome b gene. Phylogenetic analysis indicated that the three subspecies did not cluster as one monophyletic group; S. m. malacanthus clustered into one clade, while S. m. chengi and S. m. baoxingensis clustered into another. Genetic distances between S. m. malacanthus and the other two subspecies were either very close to or larger than those between S. m. malacanthus and some other species of Schizopygopsis. There was very small genetic distance between S. m. chengi and S. m. baoxingensis. The results suggest S. m. chengi should be split from S. malacanthus into a separate species, Schizopygopsis chengi (Fang); S. m. baoxingensis should be regarded as a subspecies, S. c. baoxingensis (Fu, Ding et Ye), of Schizopygopsis chengi.