Dissertation Research: Using Genealogical Portraits of Speciation to Understand Diversity Patterns

未来9801284这项拟议的研究使用分子分析来洞察相对较近的地质历史中物种的起源，以及气候重大变化的生物学后果。北美西部的山脉构成了一个不同寻常的天空岛屿群岛，适合高海拔物种。密切相关的物种，包括Melanoplus蝗虫以及其他动植物，占据了不同的山脉和山峰，这种模式表明了最近的进化多样化。正如经常被认为的那样，这种物种起源于大约1万年前结束的更新世冰川时期的孤立和殖民。然而，它不确定哪些地区仍然没有冰，或者草原等栖息地在冰川和间冰期交替期间是如何分布的。因此，生物体占据不同山脉并分化为不同物种的确切历史是非常不确定的。例如，随着冰川的消退，物种可能从南部的避难所逐渐殖民到更北部的地区。或者，祖先物种可能一直生活在低海拔地区，并产生了新物种，因为当气候变暖时，它们的栖息地变得仅限于孤立的山顶。这项拟议的研究使用Melanoplus蝗虫来更全面地确定生物多样性起源于西部山区的历史。不同山脉的种群和物种之间的DNA序列比较可以提供分化的日期，从而检验许多物种形成于更新世冰期或更新世以来的假设。从DNA序列重建的物种之间的进化关系将被用来确定物种是由碎片化形成的，还是由逐渐向北殖民形成的。这项研究将提供关于进化辐射的为数不多的全面观点之一。利用现代系统发育技术和种群遗传模型，它将检验关于物种形成的假说，从而为物种多样性的起源提供见解。它还将揭示过去的气候变化如何影响生物的分布和多样性--这些信息可能有助于预测未来全球气候变化的影响。

Futuyma 9801284 The proposed research uses molecular analyses to gain insight into the origin of species in the relatively recent geological past, and into the biological consequences of major changes in climate. The mountains of western North America constitute an unusual archipelago of sky islands for high-altitude species. Closely related species, including Melanoplus grasshoppers as well as other animals and plants, occupy different mountain ranges and peaks, in a pattern that suggests recent evolutionary diversification. It as often been suggested that such species originated by isolation and colonization during the Pleistocene glaciations that ended about 10,000 years ago. However, it is not certain which regions remained free of ice, or how habitats such as grasslands were distributed during the alternating glacial and interglacial periods. Thus the exact history by which organisms came to occupy different mountain ranges and differentiated into distinct species is very uncertain. For instance, species may have colonized progressively more northern areas from southern refuges as the glaciers retreated. Alternatively, ancestral species may have persisted at low altitudes, and have given rise to new species, as their habitats became restricted to isolated mountaintops when the climate became warmer. The proposed research uses Melanoplus grasshoppers to determine more fully the history by which biodiversity has originated in the western mountains. Comparisons of DNA sequences among populations and species from different mountain ranges can provide dates for divergence, and thus test the hypothesis that many species formed during or since the Pleistocene glaciations. Evolutionary relationships among species as reconstructed from DNA sequences, will be used to determine whether species formed by fragmentation or by progressive northward colonization. This research will provide one of the few comprehensive views of an evolutionary radiation. Using modern phylogenetic techniques and population genetic models, it will test hypotheses about species formation, and thus provide insights into the origin of diversity. And it will cast light on how past changes in climate have affected the distribution and diversity of organisms - information that may help to predict effects of future global changes in climate.