Molecules, Morphology, and the Evolutionary Radiation of Placental Mammals

活的胎盘哺乳动物由大约4,000个物种组成，分为18个不同的目(例如，啮齿动物、灵长类动物、兔子和鼠兔、大象、海牛)。事实证明，解决这些目之间的进化关系很困难。关于哺乳动物进化史的基本问题仍然悬而未决。古代超级大陆的解体如何影响哺乳动物的进化史？6500万年前恐龙和其他大型爬行动物的灭绝是如何影响主要哺乳动物群体的进化的？哺乳动物之间进化不同种类的适应(例如，飞行中导航的回声定位系统)的频率是多少？重建进化谱系的一种方法是使用DNA序列。在我们的研究中，我们将获得97个胎盘哺乳动物的7个不同基因的DNA序列。被选为这项研究的哺乳动物代表了所有主要群体。除了重建进化谱系外，我们还将使用分子时钟估计哺乳动物目之间的分歧时间。我们用分子重建的进化史将为评估大陆分裂和大规模灭绝如何影响哺乳动物进化提供一个框架。我们还将根据我们通过DNA序列获得的进化树来检查哺乳动物适应的起源。

Springer9903810Living placental mammals comprise a group of approximately 4,000 species that are classified into 18 different orders (e.g., rodents, primates, rabbits and pikas, elephants, sea cows). Resolving evolutionary relationships among these orders has proved difficult. Fundamental questions concerning the evolutionary history of mammals remain unsettled. How did the breakup of ancient supercontinents affect the evolutionaryhistory of mammals? How did the extinction of dinosaurs and other large reptiles 65 million years ago influence the evolution of the major groups of mammals? How frequently have different kinds of adaptations (e.g., echolocation systems for navigation during flight) evolved among mammals? One approach to reconstruct evolutionary genealogy is to use DNA sequences. In our study, we will obtain DNA sequences for seven different genes from 97 placental mammals. The mammals that were chosen for this study are representative of all major groups. In addition to reconstructing anevolutionary genealogy, we will estimate divergence times among mammalianorders using a molecular clock. The evolutionary history that we reconstruct using molecules will provide a framework for evaluating how continental breakup and mass extinction have influenced mammalian evolution. We will also examine the origins of mammalian adaptations in light of the evolutionary tree that we obtain with DNA sequences.