DISSERTATION RESEARCH: Molecular and Morphological Perspectives on the Dynamics of a Post-glacial Contact Zone

杂交带为研究进化过程提供了极好的机会。通过阐明形成杂交区的机制，我们可以开始理解进化因素的作用，如选择、基因交换障碍和新的适应。晚更新世（13万- 1万年前）的动态冰川事件被认为改变了许多高纬度生物的地理分布并创造了接触带。虽然许多记录在案的冰期后接触带都是在欧亚大陆，但北美的系统地理学研究表明，冰期后接触是在冰盖退缩之后发生的。对阿拉斯加东南部北部红背田鼠（Clethrionomys rutilus）和南部红背田鼠（Clethrionomys gapperi）冰川后接触带的初步研究表明，C. rutilus线粒体基因组单向渗透到C. gapperi种群中。提出的工作将使用额外的分子标记和形态计量学工具来探索这个杂交区域的基本进化过程。红背田鼠接触带是一个很好的模型系统，因为这些分类群的系统地理历史是众所周知的。这些物种相互接触超过2000公里，为研究多个地点的种间动态提供了机会，以测试可能形成该接触区的过程的一致性。该研究将利用来自接触带三个样带的种群个体，结合形态学数据、细胞色素b、Sry、MHY2基因序列和12个微卫星位点来解决以下问题：渗入的方向是什么？渗透是当代的吗？混血儿的命运如何？种间相互作用的结果在接触带的多个横断面上是否相同？

Hybrid zones provide excellent opportunities to study evolutionary processes. By elucidating mechanisms that shape hybrid zones, we can begin to understand the role of evolutionary factors such as selection, barriers to genetic exchange, and new adaptations. The dynamic glacial events of the late Pleistocene (130,000 - 10,000 years ago) are believed to have modified geographic distributions of many high latitude organisms and created contact zones. While many of the documented post-glacial contact zones are Eurasian, phylogeographic studies in North America are demonstrating post-glacial contact following the retreat of the ice sheets. Preliminary research on a post-glacial contact zone between the northern red-backed vole (Clethrionomys rutilus) and southern red-backed vole (Clethrionomys gapperi) in southeast Alaska documented unidirectional introgression of the mitochondrial genome of C. rutilus into populations of C. gapperi. The proposed work will use additional molecular markers and morphometric tools to explore fundamental evolutionary processes in this hybrid zone. The red-backed vole contact zone is an excellent model system because the phylogeographic histories of these taxa are well known. These species contact each other over 2000 km, providing an opportunity to study interspecific dynamics at multiple localities to test for the consistency of processes that may be shaping this contact zone. Using individuals from populations across three transects of the contact zone, the study will combine morphological data, sequences of the cytochrome b, Sry, MHY2 genes, and 12 microsatellite loci to address the following questions: What is the direction of introgression? Is introgression contemporary? What are the fates of the hybrids? Are the consequences of interspecific interactions the same across multiple transects of the contact zone?