摘要
正确的系统发生重建对于理解进化事件至关重要。尽管分子系统学对于解决此类问题取得了极大的成功,由于一些诸如密码子使用偏性等的内在约束,来源于 DNA 的信息可能仍然存在着局限。因为发生在祖先的替代性转换,果蝇Drosophila saltans 5个种亚组由不同基因构建的分子系统树之间存在着冲突(在以往发表的分子系统学研究中,这些种组的每一个种亚组至少有一个代表)。本文用40个形态学特征重新分析了这些种组。不同于以前发表的大多数假说,本研究支序分类学的结果表明,果蝇sturtevanti种亚组是一个较早的分支, 而剩下的4个亚组形成一个支持度较高的类群;后者又可以再分为两个姐妹群:一个包含cordata和elliptica 亚组,另一个包含parasaltans和saltans 亚组。本研究结果修正了果蝇saltans种组的分子进化(密码子使用偏性),并强调形态学对于系统发生重建和理解分子进化现象的重要作用。
Proper phylogenetic reconstruction is crucial for understanding many evolutionary phenomena. In spite of the great success of molecular phylogenetics, DNA signal still may be limited by some intrinsic constraints such as codon usage bias. The phylogenetic relationships between the five species subgroups of the Drosophila saltans group are a good example of conflicting molecular phylogenies drawn from different genes due to an ancestral substitutional shift. Here, forty morphological characters were analyzed using the same set of species used in previous molecular studies, with at least a single representative of each subgroup. The cladistic analysis was in disagreement with most of the previous hypotheses in placing the sturtevanti subgroup as an early branch, whereas the four remaining subgroups form a well supported clade that can be further subdivided into two sister clades： one containing the cordata and the elliptica subgroups, whereas the second includes the parasaltans and the saltans subgroups. The molecular evolution （codon usage bias） of the saltans group were revised in light of the present finding. The analysis highlights the important role of morphology in phylogeny reconstruction and in understanding molecular evolutionary phenomena.
基金
funded by the Prix Jeune Chercheur of the Fondation Bettencourt-Schueller
