School of Life Sciences, Fudan University, Shanghai, 200433, China.
Gene. 2013 Apr 1;517(2):169-78. doi: 10.1016/j.gene.2012.12.096. Epub 2013 Jan 14.
The schizothoracine fishes, also known as "mountain carps" are widely distributed in the Qinghai-Tibetan Plateau and its peripheral regions. Although they provide a prime example of high altitude adaptation, the phylogenetic relationships and the divergence times among these carp lineages are still controversial. Moreover, the genetic basis for high altitude adaptation is also poorly understood. In this study, we determined the mitochondrial genomes from two species of the schizothoracine fishes, representing a "morphologically primitive" clade and "morphologically specialized" clade, respectively. The phylogenetic tree and the divergence times were estimated within the evolutionary framework of the entire order Cypriniformes. Our results indicate a polyphylyetic relationship of the schizothoracine fishes and suggest two independent migration events into the Qinghai-Tibetan Plateau: one by the "morphologically primitive" clade in the Late Miocene and another by the "morphologically specialized" clade in the Eocene. Rapid speciation events of each clade from the Late Miocene to the Pliocene correspond to the timing of the geologic acceleration of the Qinghai-Tibetan Plateau. Interestingly, we found evidence for positive selection acting on the protein coding genes in the mitochondrial genomes of the "morphologically specialized" clade, implying a possible genetic basis for high altitude adaptation in this derived lineage of cypriniform fishes.
高原鳅鱼类，又称“山鱼”，广泛分布于青藏高原及其周边地区。尽管它们提供了一个适应高海拔环境的典型例子，但这些鲤鱼谱系之间的系统发育关系和分化时间仍然存在争议。此外，高海拔适应的遗传基础也知之甚少。在这项研究中，我们测定了两种高原鳅鱼类的线粒体基因组，它们分别代表了一个“形态原始”的分支和一个“形态特化”的分支。在整个鲤形目进化框架内，我们对系统发育树和分化时间进行了估计。我们的结果表明高原鳅鱼类是一个多系群，并提示了两次独立的迁移事件进入青藏高原：一次是由“形态原始”分支在中新世晚期，另一次是由“形态特化”分支在始新世。每个分支从中新世到晚新世的快速物种形成事件与青藏高原地质加速的时间相对应。有趣的是，我们在“形态特化”分支的线粒体基因组中发现了蛋白质编码基因受到正选择作用的证据，这暗示了这个鲤形目鱼类的衍生谱系中可能存在高海拔适应的遗传基础。
