title: The youngest split in sympatric schizothoracine fish (Cyprinidae) is shaped by ecological adaptations in a Tibetan Plateau glacier lake.
abstract: Although new empirical evidence shows that sympatric speciation has occurred in some species, there are few indisputable model organisms for this process of speciation. The two subspecies (Gymnocypris eckloni eckloni and G. e. scoliostomus) of the schizothoracine Gymnocypris fish species complex from a small glacier lake in the Tibetan Plateau, Lake Sunmcuo, fit several of the key characteristics of the sympatric speciation model. We used combined mitochondrial control region sequences and the cytochrome b gene (1894 bp) to address the phylogenetics and population genetics of 232 specimens of G. e. eckloni and G. e. scoliostomus, as well as all of its closely related sister species. We found that: (i) a total of four old lineages were uncovered in the widespread G. e. eckloni, of which only one was shown to be shared with all G. e. scoliostomus individuals and (ii) the new subspecies (G. e. scoliostomus) evolved in Lake Sunmcuo from the ancestral G. e. eckloni population within approximately 0.057 Ma. These two taxa of the species complex are morphologically distinct, and reproductive isolation is further suggested. Ecological disruptive selection based on morphological traits (e.g. mouth cleft characters) and food utilization may be a mechanism of incipient speciation of two sympatric populations within Lake Sunmcuo. This study provides the first genetic evidence for sympatric speciation in the schizothoracine fish.
authors.affiliation: Key Laboratory of Adaptation and Evolution of Plateau Biota (AEPB), Northwest Plateau Institute of Biology, Chinese Academy of Sciences, 810001 Xining, Qinghai, China.
authors.forename: Kai
authors.initials: K
authors.lastname: Zhao
authors.forename: Zi Yuan
authors.initials: ZY
authors.lastname: Duan
authors.forename: Zuo Gang
authors.initials: ZG
authors.lastname: Peng
authors.forename: Song Chang
authors.initials: SC
authors.lastname: Guo
authors.forename: Jun Bing
authors.initials: JB
authors.lastname: Li
authors.forename: Shun Ping
authors.initials: SP
authors.lastname: He
authors.forename: Xin Quan
authors.initials: XQ
authors.lastname: Zhao
mesh_terms: D000818:Animals; D003530:Cyprinidae / Q000145:classification / Q000235:genetics*; D045303:Cytochromes b / Q000235:genetics; D004272:DNA, Mitochondrial / Q000235:genetics; D017753:Ecosystem; D019143:Evolution, Molecular; D049810:Genetic Speciation; D005828:Genetics, Population; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D018609:Tibet
chemical_list: D004272:DNA, Mitochondrial; D045303:Cytochromes b