摘要：动物的适应性进化（adaptive evolution）是进化生物学中的核心问题之一。鲸类其祖先从陆地重返海洋，必须形成完善的渗透调节机制进行排盐保水方可在海洋中得以生存。本论文选择渗透调节的关键功能基因Na+，K+-ATP酶，测定齿鲸亚目与须鲸亚目代表性物种该基因α1亚单位的第12外元。与数据库中部分哺乳动物同源基因相结合,共有18个物种的序列用于分析。在氨基酸变异位点检测中，在192个核苷酸位点中，共有60个变异位点（31.25%），序列两两比较发现，种间最大差异和最小差异分别为13.02%（25个核苷酸差异，小须鲸vs.人）和0（江豚vs.白鲸）。在64个氨基酸位点中，共有4个变异位点（6.25%），序列两两比较，种间最大差异和最小差异分别为9.38%（6个氨基酸差异，小鼠vs.小须鲸）和0（猪vs.白暨豚）。其中第10位氨基酸位点鲸类发生了特异性改变，非常有趣的是，选择压力检测表明这一位点是潜在的正选择位点，推测鲸类从陆地重返海洋并稳定适应海洋环境的过程中，渗透调节的关键基因Na+，K+-ATP酶已经产生了适应性功能变异。

关键词：  鲸类  适应性进化 渗透调节  Na+，K+-ATP酶α1亚基  正选择

Abstract：Adaptive evolution in animals is one of fundamental issues in biology. The ancestors of whales return to sea from the land, it is necessary to form a complete osmoregulation mechanism which discharges salt and keeps water for survive in the ocean. Therefore, the key gene of osmoregulation, Na+, K+-ATPase was investigated in Cetacean species to explore the molecular mechanism. In this thesis, we identified the 12th exon of Na+, K+-ATPase α1 subunit in 8 representative species (6 species from suborder Odontoceti, 2 from suborder Balaenoptera). Combined with part of mammals homologous genes in the database, a total of 18 sequences were analyzed in the study. A total of 60 variable sites were identified in 192 (31.25%) nucleotide sites. Accordingly, four amino acid differences were found in 64 (6.25%) sites. In addition, specific amino acid site was examined in cetacean species at 10th amino acid site. Interestingly, positive selection was detected at the site, suggesting that adaptive evolution may occur in cetacean species, which may play important roles in its ecological adaptation to the ocean environment.

Key words: Cetacea; adaptive evolution; Osmoregulation; Na+,K+-ATPase α1 subunit; positive selection