Molecules, Morphology, and the Evolutionary Radiation of Placental Mammals

Springer9903810活的胎盘哺乳动物包括一组大约4,000种，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）。 解决这些订单之间的进化关系已被证明是困难的。 关于哺乳动物进化史的基本问题仍然没有解决。 古代超级大陆的分裂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？不同类型的适应性有多频繁（例如，在飞行中导航的回声定位系统）在哺乳动物中进化？ 重建进化谱系的一种方法是使用DNA序列。在我们的研究中，我们将从97个胎盘哺乳动物中获得7个不同基因的DNA序列。本研究选择的哺乳动物代表了所有主要群体。除了重建进化谱系，我们还将使用分子钟估计古生物目之间的分歧时间。我们利用分子重建的进化历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。我们还将根据我们用DNA序列获得的进化树来研究哺乳动物适应性的起源。

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.