从c-mos和12S rRNA基因序列探讨现生鸟类早期历史和三趾鹑类的系统地位

通常认为古腭型鸟类处在现生鸟类系统进化树的基部,最近的分子水平研究则认为今腭型鸟类中雀形目种类构成了现生鸟类中一个最古老的支系.本研究通过对现生鸟类中21目39种核c-mos基因和线粒体12S rRNA基因部分序列的分析,从分子角度对现生鸟类的早期进化及三趾鹑鸟类的系统发生进行了探讨.研究结果表明,鸡雁类是现生鸟类最古老的一个支系,现生鸟类的祖先并不是经白垩纪到第三纪大灭绝后残留下来的一些过渡性水鸟(transitional shorebirds).在现生鸟类中,今腭型鸟类为并系发生,古腭型鸟类为单系发生.三趾鹑类在系统发生中晚于鸡雁类和古腭型鸟类,早于今腭型鸟类中非鸡雁类鸟类与鹤形目鸟类的亲缘关系较远.建议将现生鸟类分为初鸟下纲和新鸟下纲2个下纲,三趾鹑类属新鸟下纲的三趾鹑目(Turniciformes).

THE EARLY HISTORY OF MODERN BIRDS AND THE PHYLOGENETIC STUDY OF BUTTONQUAILS INFERRED FROM DNA SEQUENCES OF c-mos AND 12S rRNA GENES

The traditional view of avian evolution places palaeognath birds at the base of the phylogenetic tree of modern birds (Neornithes). The molecular studies suggest that neognathous perching birds (Passeriformes) compose the oldest lineage of modern birds. Here the partial sequences of the c-mos and 12S rRNA genes of 39 species of 21 orders were used to study the early history of modern birds and to discuss the phylogenetic position of the buttonquails. The results indicate that the galloanserine birds occupy the most basal position among all modern birds, and the modern birds were not evolved from the `transitional shorebirds', one of the few avian survivors of the mass extinction at the Cretaceous-Tertiary (K-T) boundary 65 Myr ago. The results also show that the neognath was paraphyly, and the palaeognath was monophyly. Phylogenetic analyses further show that the buttonquails were a basal clade of the neognathous birds (excluding galloanserine birds), and have no sister relationship with cranes. The results suggest that the subclass Neornithes could be divided into two infraclass Eoaves and Neoaves, and the buttonquails belong to order Turniciformes, infraclass Neoaves.