Generic Relationships Among Dasyurid Marsupials Based on Mitrochondrial Cytochrome-b Sequences

Dasyurids是澳大利亚主要的陆生食肉动物，占据着各种各样的栖息地，如干旱地区、森林和高山荒原。它们是小型到中型哺乳动物，从微小的Pilbara ningaui（209克）到狗大小的塔斯马尼亚魔鬼（6-8公斤）。有袋动物科17属约51种，是澳大利亚有袋动物的三大谱系之一。从20世纪初开始，人们就试图了解dasyurids之间的进化关系，但这些努力只能揭示系统发育的最广泛的轮廓。近年来，对菊科植物分子遗传变异的比较研究使我们对菊科植物之间的关系有了一定的了解，但尚未建立起一个详细而明确的属分支顺序。由于缺乏系统发育方面的解决办法，对了解dasyurids的历史生物地理学，特别是新几内亚特有物种的起源的努力造成了阻碍。在这项研究中，线粒体细胞色素-b基因的DNA序列变异将测定所有dasyurd属的代表。细胞色素b是细胞能量产生的关键成分，是一个相对较小（约400个残基）和简单的分子。细胞色素-b的DNA变异模式跨越由dasyurids所代表的分化时间范围，将允许构建一个基因如何进化的简单模型。这种模型对估计系统发育的价值是现代分子系统学的一个关键问题。数据和模型一起将提供一种有趣的方法来比较几种当前的和概念上不同的系统发育推断方法。最终结果将提供一个更清晰的dasyurid关系图，以及更好地理解细胞色素b的进化和分子系统发育。

Dasyurids are the dominant terrestrial carnivores of Australia, occupying a diverse array of habitats such as aridlands, forest, and alpine heath. They are small to medium sized mammals, ranging from the tiny Pilbara ningaui (209 g) to the dog-sized Tasmanian devil (6-8 kg). With approximately 51 species in 17 genera, the family Dasyuridae constitutes one of three major lineages of Australasian marsupials. Attempts to understand the evolutionary relationships among dasyurids date from the early 20th century, but these efforts could only reveal the broadest outlines of phylogeny. In recent years, comparative study of molecular genetic variation among dasyurids has shed much light on relationships within the family, but a detailed and well-resolved branching order for genera has not been established. This lack of phylogenetic resolution has hampered efforts to understand the historical biogeography of dasyurids, particularly the origins of New Guinean endemics. In this study, DNA sequence variation in the mitochondrial cytochrome-b gene will be assayed for representatives of all dasyurid genera. Cytochrome-b, a key component in cellular energy production, is a relatively small (ca. 400 residues) and simple molecule. Patterns of DNA variation in cytochrome-b across the range of divergence times represented by dasyurids will allow construction of a simple model of how the gene evolves. The value of such a model for estimating phylogeny is a key issue in modern molecular systematics. The data and model together will provide an interesting means of comparing several current and conceptually distinct methods of phylogenetic inference. Final results should provide a clearer picture of dasyurid relationships, as well as a better understanding of cytochrome-b evolution and molecular phylogenetics.