豉甲科及水生肉食亚目的分子系统发育学分析(昆虫纲：鞘翅目)

Phylogeny of Gyrinidae and Hydradephaga (Insecta:Coleoptera) based on COⅠ gene:a case study using codon-partitioning schemes in phylogenetic tree reconstruction

利用PAUP和MrBayes软件,对线粒体COⅠ基因序列3个密码子位置的数据模块分别进行了豉甲科（Gyrinidae）和水生肉食亚目（Hydradephaga）在亚科或科水平上的系统发育学分析,结果表明第二密码子数据模块获得了理想的分析结果。由PAUP生成的豉甲科最优树来自第二密码子数据模块的分析,而由MrBayes生成的最优树来自全部密码子数据模块的分析。此外,用对应的氨基酸序列生成的ME和MP树与第二密码子数据模块分析的结果也一致。亚科Orectochilinae和Gyrininae以高的支持率形成了单系。然而,来自亚科Enhydrinae的种Porrorhynchus landaisi landaisi呈现了异常的位置。SH-test检验也支持该异常位置,表明这个种可能代表了一个科。在来自第二密码子数据模块的水生肉食亚目最优ML树中,整个Hydradephaga树呈现单系,豉甲科位于树的基部,表明了该科在水生肉食亚目中是一个早期的分支。在树中还产生了一个单系的Dytiscoidea总科,由Dytiscidae、Hygrobiidae、Noteridae和Amphizoidae 4个科组成,单系的Haliplidae与之成为姐妹群。此外线粒体分子钟的结果表明豉甲科的5对相近种间的分化是一个短时期内发生的（0.01~1.81百万年前）,这点可能与它们的特殊地理分布有关。

Codon partition schemes were compared in phylogenetic analyses at subfamily level for Gyrinidae and at family level for Hydradephaga based on partial mitochondrial COⅠ gene sequences. The results consistently demonstrated superiority for second codon partition data in analyses using ME, MP, or ML algorithms implemented in PAUP and Bayesian algorithm implemented in MrBayes. Optimal trees were inferred using PAUP based on second codon partition data and using MrBayes based on combined codon data, which showed good consistency and were consistent with the trees inferred from corresponding translated amino acid data. All analysis placed the Enhydrinae species Porrorhynchus landaisi landaisi in the unexpected most basal position of the Hydradephaga phylogenetic tree, which was supported by SH tests, justifying this species a monotypic family within Hydradephaga. In the ML tree based on the second codon partition data of the Hydradephaga dataset, monophyly of the whole Hydradephaga was well supported and Haliplidae and Dytiscoidea （ = Dytiscidae, Hygrobiidae, Noteridae, and Amphizoidae） appeared as sister monophyletic groups. Topology of the trees was in accordance with the polyphyly hypothesis postulating three independent transitions to the aquatic environment. Mitochondrial DNA clock analysis suggested the radiation within a relatively short period of time （0.01 - 1.81 mya） of five pairs of closely related species that are currently distributed indifferent geographic regions.