青藏高原裸裂尻属鱼类两个疑难种的分子系统学

Molecular systematics of two enigmatic fishes in the genus Schizopygopsis in the Qinghai-Tibetan Plateau

裸裂尻鱼属[Schizopygopsis(Steindachner)]鱼类广泛分布于青藏高原各河流上游干支流及其湖泊之中,由于其广泛的分布域和特殊的生态环境而被生物学家视为青藏高原隆升过程中淡水鱼类物种起源、进化的模式物种。然而,该属鱼类种间具有非常相似的形态特征,致使大渡软刺裸裂尻鱼(Sp·malacanthuschengi)和前腹裸裂尻鱼(Sp·anteroventris)的分类学地位一直存在争议。本文采用聚合酶链式反应(PCR)和直接测序的方法,获得了裸裂尻鱼属两个分类疑难种和5个指名种(n=17)以及5个近缘种(n=5)共23个个体的细胞色素b(Cytb)基因的全序列(1140bp),并以同亚科的齐口裂腹鱼(Schizothoraxprenanti)作为外群构建了ML、MP和Bayesian进化树。序列差异和分子系统学分析表明,Sp·malacanthuschengi和软刺裸裂尻鱼(Sp·malacanthus)间存在较大的差异(2·06%),两者并不聚在同一枝上;Sp·anteroventris独立成一枝,与其它指名裸裂尻鱼间显示出较大差异(4·38%-5·53%),综合其它形态差异共同提示,Sp·malacanthuschengi应提升为独立种,沿用Sp·chengi的种名,而Sp·anteroventris应该是裸裂尻鱼属的一个独立种。

The genus Schizopygopsis （Steindachner） is widely distributed in the upper reaches of almost all the main rivers and lakes in the Qinghai-Tibetan Plateau. The wide distribution range and the peculiar ecological specializations of these fishes are of biological interest. The Schizopygopsis, therefore, is an ideal model with which to investigate the speciation, diversification and evolution of freshwater fish endemic to the Qinghai-Tibetan Plateau. Although special attention was given to the biology of the genus Schizopygopsis in the past, the taxonomy of Sp. malacanthus chengi （Fang） and Sp. anteroventris （Wu, Tsao, Zhu and Chen） remain controversial owing to their morphological similarity （for example, arrangement of pharyngeal teeth, sheath morphology of the lower jaw, character state of the pharyngeal bone, and gill rakers）. In the present study, the complete sequences of the mitochondrial Cyt b gene from seventeen individuals represented Sp. malacanthus chengi, Sp. anteroventris and other five species of Schizopygopsis as well as five closed species in the same subfamily Schizothoracinae were sequenced. The sequences were subjected to maximum parsimony （MP）, maximum likelihood （ML） and Bayesian analyses. The molecular phylogenetic analyses showed that Sp. malacanthus chengi and Sp. malacanthus didn＇t cluster together and there was a relatively high （2.06%） divergence between them. Sp. anteroventris was placed in a clade genetically distant from the other species of Schizopygopsis. Results from the molecular data, coupled with other morphological characters suggest that Sp. malacanthus chengi should be elevated to specific status, keeping the species name of Sp. chengi, while Sp. anteroventris should be retained as a distinct species in the genus Schizopygopsis .