Dissertation Research: The Speciation Process in Orconectes, subgenus Procericambarus (Decapoda:Cambaridae)

允许或至少与之相关的因素 当一个创始成员进入一个新的物种时， 对新的栖息地知之甚少。 然而，适应性的现象 辐射被认为是重要的，许多病例已经被 多年来提出的。 一开始的一个基本问题是， 这是一个建立牢固的系统发育关系， 辐射状组合的种类。 一个测试案例， 这件事正在调查中， 属Orconectes。 该亚属约24种 Procericambarus栖息在各种溪流，池塘和河流中 在北美洲中部的高海拔和低海拔的边缘， 为研究适应性物种形成模式提供了机会 新的生态栖息地。 学院赞助人艾伦·邓普顿和研究生基思 克兰德尔强调来自线粒体的分子数据， 核DNA来建立这群动物的遗传学。 目前正在特别注意评估 这些基于分子系统发育 重建，这样的统计测试可能会有 适用于其他研究人员的研究。 与 有了强大的系统发育估计，研究人员就可以 探索这样的问题：栖息地差异和地理 物种之间的隔离， 还是与物种形成事件相互作用？ 并 向一个非常不同的栖息地类型的过渡导致了 随后的物种形成（著名的适应区假说， 已故古生物学家G. G.辛普森）？ 物种形成会发生吗 只有在与栖息地有关的情况下， 分歧？ 此外，研究人员还将研究 形态学变化，包括总体尺寸减小， 小龙虾的分子结构 我是马根尼

The factors that permit or, at the least, are correlated with rapid speciation of a lineage when a founding member moves into a new habitat are little understood. Yet the phenomenon of adaptive radiation is considered significant, and numerous cases have been proposed over the years. One basic issue at the start needs to be established solidly, that is the phylogenetic relationships among the species of the radiating assemblage. A test case of precisely this matter is under investigation with North American crayfish of the genus Orconectes. Approximately 24 species of the subgenus Procericambarus inhabit a variety of streams, pools, and river margins at high and low elevations in middle North America, and provide opportunities to study the pattern of adaptive speciation into new ecological habitats. Faculty sponsor Alan Templeton and graduate student Keith Crandall are emphasizing molecular data from mitochondrial and nuclear DNA to establish a phylogeny of this group of animals. Special attention is being given to issues of assessing the statistical significance of these molecule-based phylogenetic reconstructions, and such statistical tests are likely to have general applicability to studies by other researchers. With a robust phylogenetic estimate in hand, the investigators can then explore such questions as: are habitat divergence and geographic isolation among species independently associated through evolutionary time or do they interact with speciation events? Does a transition into a very different habitat type lead to much subsequent speciation (the well-known adaptive zone hypothesis of the late paleontologist G. G. Simpson)? Can speciation occur within an isolated drainage only if it is associated with habitat divergence? As well, the investigators will study aspects of morphological change including overall size reduction in these crayfish against the background of their molecularly based phylogeny.