Dissertation Research: Evolution in a Recently Arisen Species Complex: Phylogeography and Genetic Diversity in Manihot esculenta Crantz (Euphorbiaceae)

沙尔9801213 一个物种内的种群随着时间的推移而分化的过程， 新物种的形成知之甚少。 沙尔和奥尔森提议 用植物中的两个物种来研究遗传分化的过程， 属木薯作为一个研究系统。 他们将研究基因的模式 M.食用植物 M之间。esculenta和近缘种M. pruinosa。 利用DNA序列数据和其他分子遗传学数据的组合， 他们将研究当今的种群遗传结构 反映了研究系统中人群之间的历史关系。 他们的分析是专门设计来区分 种群之间的基因流动（迁移）和 遗传变异（谱系分类）。 理解在两个物种之间的边界上遗传分化的过程 种群和物种对于理解物种形成至关重要， 进化多样化 因此，这个问题具有根本的重要性 对进化过程的理解。 Schaal提出的研究， 奥尔森提供了几个优势，研究这一物种形成过程。 因为他们的研究系统也包括了一个物种内的种群 在物种之间，他们的分析明确包括 种群-物种界面。 此外，由于种间 有人提出，这两个物种之间可能发生杂交。 在野生木薯中，基因流的潜在影响与 在物种边界之上和之下。 此外，三个 亚种M. esculenta是栽培作物木薯，这是 世界上第四大淀粉作物， 五亿人。 拟议的研究将有助于阐明 木薯的进化和地理起源，因此， 对保护遗传多样性的方法有着重要的意义 在这个作物。

Schaal 9801213 The process by which populations within a species diverge over time to form new species is poorly understood. Schaal and Olsen propose to study this process of genetic divergence, using two species in the plant genus Manihot as a study system. They will examine patterns of genetic differentiation within and among the three subspecies of M. esculenta, as well as between M. esculenta and the closely related species M. pruinosa. Using a combination of DNA sequence data and other molecular genetic markers, they will study how present-day population genetic structure reflects historical relationships among populations in the study system. Their analysis is specifically designed to discriminate between the effects of gene flow (migration) between populations and the random sorting of genetic variation (lineage sorting). Understanding the process of genetic divergence at the boundary between populations and species is crucial to understanding speciation and evolutionary diversification. This issue is thus of fundamental importance in understanding the process of evolution. The study proposed by Schaal and Olsen offers several advantages for studying this speciation process. Because their study system involves populations within a species as well as between species, their analysis explicitly encompasses the population-species interface. Moreover, because interspecific hybridization has been proposed to occur between the two species of Manihot in the wild, the potential influence of gene flow is relevant at both above and below the species boundary. In addition, one of the three subspecies of M. esculenta is the cultivated crop cassava, which is the fourth most important starch crop in the world and a staple food for over 500 million people. The proposed study will help to shed light on the evolutionary and geographical origins of cassava, and will therefore have important implications for approaches to conserv ing genetic diversity in this crop.