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The interactive effects of speciation and introgression on the mitochondrial DNA evolution in Drosophila

果蝇线粒体DNA进化中物种形成和基因渗入的相互作用

基本信息

批准号：
15570082
负责人：
TAMURA Koichiro
金额：
$ 2.37万
依托单位：
Tokyo Metropolitan University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2005
项目状态：
已结题

项目摘要

The nucleotide substitution rate for mitochondrial DNA (mtDNA) is generally much faster than that for nuclear DNA in higher animals, which makes mtDNA useful to detect a difference between closely related species. However, phylogenetic relationships of mtDNA often show conflicts with the species relationships due to ancestral polymorphisms and geographic population subdivisions. For instance, the mitochondrial introgression, which totally disrupts the correspondence between mtDNA and species phylogenies, has been reported repeatedly between closely related species in a sympatric condition.To clarify the interactive effects of speciation and introgression on the mtDNA evolution, the sequence divergences of mtDNA (cytochrome c oxidase subunit 1 gene) and nuclear DNA (xanthine dehydrogenase and white genes) were investigated for species and subspecies of the Drosophila nasuta subgroup, which includes several closely related species and subspecies on the way of speciation and distributes in various condition from complete allopatry to sympatry depending on the geographic locations. The results show a strong correlation between geographic distances of habitats and sequence divergences of mtDNA, whereas it was not the case of nuclear DNA. Furthermore, evidence of frequent mitochondrial introgressions in the course of the D.nasuta subgroup evolution was indicated. In conclusion, the importance of taking geographic distribution pattern and the potential of introgression into consideration in the phylogenetic studies of mtDNA was suggested.Furthermore, for better performance of molecular phylogenetic analyses, theoretical studies were conducted to develop the statistical methods for estimating a neutral nucleotide substitution rate from protein coding sequences under a codon selection and a distance matrix for the reconstruction of large phylogenetic trees with the neighbor-joining method.

在高等动物中，线粒体 DNA (mtDNA) 的核苷酸取代率通常比核 DNA 快得多，这使得 mtDNA 可用于检测密切相关物种之间的差异。然而，由于祖先多态性和地理种群细分，线粒体DNA的系统发育关系常常与物种关系发生冲突。例如，在同域条件下密切相关的物种之间，线粒体基因渗入完全破坏了mtDNA与物种系统发育之间的对应关系。为了阐明物种形成和基因渗入对mtDNA进化的相互作用影响，mtDNA（细胞色素c氧化酶亚基1基因）和核DNA（黄嘌呤脱氢酶基因）的序列差异对果蝇亚群的物种和亚种进行了研究，该亚群包括几个在物种形成方式上密切相关的物种和亚种，并根据地理位置以从完全异域到同域的各种条件分布。结果表明，栖息地的地理距离与线粒体DNA的序列差异之间存在很强的相关性，而核DNA的情况则不然。此外，有证据表明 D.nasuta 亚群进化过程中频繁发生线粒体渗入。总之，提出了在线粒体DNA系统发育研究中考虑地理分布模式和基因渗入潜力的重要性。此外，为了更好地进行分子系统发育分析，进行了理论研究，开发了在密码子选择和距离矩阵下估计蛋白质编码序列中性核苷酸替换率的统计方法，以重建大型系统发育树采用邻接法。