Due to their integral roles in oxidative phosphorylation, mitochondrially encoded proteins represent common targets of selection in response to altitudinal hypoxia across high-altitude taxa. While previous studies revealed evidence of positive selection on mitochondrial genomes of high-altitude Phrynocephalus lizards, their conclusions were restricted by out-of-date phylogenies and limited taxonomic sampling. Using topologies derived from both nuclear and mitochondrial DNA phylogenies, we re-assessed the evidence of positive selection on the mitochondrial genomes of high-altitude Phrynocephalus. We sampled representative species from all four main lineages and sequenced the mitochondrial genome of P. maculatus, a putative sister taxon to the high-altitude group. Positive selection was assessed through two widely used branch-site tests: the branch-site model in PAML and BUSTED in HyPhy. No evidence of positive selection on mitochondrial genes was detected on branches leading to two most recent common ancestors of high-altitude species; however, we recovered evidence of positive selection on COX1 on the P. forsythii branch, which represents a reversal from high- to low-elevation environments. A positively selected site therein marked a threonine to valine substitution at position 419. We suggest this bout of selection occurred as the ancestors of P. forsythii re-colonized lower altitude environments north of the Tibetan Plateau. Despite their role in oxidative phosphorylation, we posit that mitochondrial genes are unlikely to have represented historical targets of selection for high-altitude adaptation in Phrynocephalus. Consequently, future studies should address the roles of nuclear genes and differential gene expression.

由于它们在氧化磷酸化中的不可或缺的作用，线粒体编码的蛋白质代表了响应高海拔分类群海拔缺氧的常见选择目标。虽然之前的研究揭示了对高海拔Phrynocephalus蜥蜴线粒体基因组进行正选择的证据，但他们的结论受到过时的系统发育和有限的分类抽样的限制。使用源自核和线粒体 DNA 系统发育的拓扑结构，我们重新评估了高海拔Phrynocephalus线粒体基因组正选择的证据。我们从所有四个主要谱系中采样了代表性物种并对P. maculatus的线粒体基因组进行了测序，一个推定的高海拔群姐妹分类单元。通过两个广泛使用的分支站点测试评估阳性选择：PAML 中的分支站点模型和 HyPhy 中的 BUSTED。在导致两个最近的高海拔物种共同祖先的分支上没有检测到线粒体基因正选择的证据；然而，我们恢复了对P. forsythii分支上 COX1 的正选择的证据，这代表了从高海拔环境到低海拔环境的逆转。其中一个积极选择的位点标记了第 419 位苏氨酸到缬氨酸的替代。我们认为这轮选择发生在P. forsythii的祖先青藏高原以北的低海拔环境重新被殖民。尽管它们在氧化磷酸化中起作用，但我们认为线粒体基因不太可能代表Phrynocephalus高海拔适应的历史选择目标。因此，未来的研究应该解决核基因和差异基因表达的作用。