REU: Exploiting Conserved and Variable Regions of the Mitochondrial Genome for Evolutionary Studies

目前的进化研究集中在伴随新物种形成的遗传变化以及在与密切相关物种杂交时保持物种完整性的问题。为了理解遗传分化所涉及的过程，必须构建进化关系的模式，并且必须参照该模式来看待正在研究的性状。过去证明，很难为新形成的(非常接近的)物种建立进化关系，但现在有了新的技术，可以从最可变的DNA基因区收集数据。这些技术被用在了本研究中。被称为周期性蝉的昆虫物种已被证明是解决进化树构建和物种分化问题的理想研究有机体；它们很容易使用，这六个物种有一套独特的分布模式，其中有不同程度的空间隔离、时间隔离和遗传变异。前人的工作结果建立了更高水平的进化关系，确定了物种间遗传变异性的差异，发现了可能进行杂交的区域，并为生命周期可塑性提供了遗传证据，这对进化理论具有重要意义。拟议的研究将检查其他孤立的种群之间的杂交可疑区域，并将系统发育分析扩展到密切相关的、未被研究的年份纲，我们认为这些纲代表了初始物种。所了解的特定基因区域对构建进化关系的有用性将直接适用于其他动植物之间关系的研究，并将导致在DNA水平上更好地理解进化的速度和机制。

Current evolutionary research focuses on problems associated with genetic changes that accompany the formation of new species and the maintenance of the integrity of species in the face of hybridization with closely related species. In order to understand processes involved in genetic differentiation, a pattern of evolutionary relationships must be constructed and the traits under study must be viewed with reference to this pattern. Evolutionary relationships have in the past proven difficult to construct for newly formed (very closely related) species but new techniques are available which allow the collection of data from the most variable DNA gene regions. These techniques are used in this research. The insect species known as the periodical cicadas have proved to be ideal study organisms to address problems of evolutionary tree construction and species divergence; they are easy to work with and the six species have a unique set of distributional patterns within which are various degrees of spatial isolation, temporal isolation, and genetic variability. Results from previous work established higher level evolutionary relationships, identified differences in genetic variability among species, discovered areas where hybridization is likely, and provided genetic evidence for life cycle plasticity which has important implications for evolutionary theory. The proposed research will examine suspected areas of hybridization among otherwise isolated groups and will extend phylogenetic analyses to the closely related, unstudied year classes which we suggest represent incipient species. What is learned about the usefulness of particular gene regions for constructing evolutionary relationships will be directly applicable to the study of relationships among other animals and plants and will lead to a better understanding of rates and mechanisms of evolution at the DNA level.