Dissertation Research: The Impact of Geographic and Environmental Heterogeneity on the Generation and Maintenance of Species Diversity in Hispaniolan Ground-dwelling Lizards

传统上认为，岛屿上调节生物多样性（特定地方存在的物种数量）的过程是来自其他地区的殖民化和岛屿内的灭绝。然而，大型岛屿可能包含许多物种，其最近的亲属只出现在同一个岛屿上，这表明岛屿内物种形成。岛内物种形成可能是地理环境破碎化事件和生境类型空间异质性的结果。本文考察了这两个因素在伊斯帕尼奥拉岛地栖蜥蜴进化多样化中的作用。本文利用分子遗传学数据研究了五种头科植物和三种无尾科植物之间的亲缘关系。利用地理信息系统技术在环境数据的背景下研究物种和种群水平的系统发育，以检验环境变化在地栖蜥蜴物种形成中起重要作用的假设。地质信息被用来测试历史环境破碎化在蜥蜴多样化中的作用。局部环境变化是用来检验地理变异的形态特征被认为具有适应意义。本研究明确确定了促进和维持岛屿动物进化多样性的环境和种群遗传条件。这项研究整合了来自不同来源的数据，以检验关于一个未被充分研究的动物群多样化的假设。这项研究还促进了多米尼加共和国的国际合作，提高了对进化和保护生物学的理解，从而使当地学生受益。

The processes regulating biodiversity (numbers of species that exist at a particular place) on islands are conventionally thought to be colonization from other areas and extinction within an island. Large islands, however, may contain many species whose closest relatives occur only on the same island, indicating within-island speciation. Within-island speciation may result from geographic environmental fragmentation events and spatial heterogeneity of habitat types. This dissertation examines the roles of these two factors in the evolutionary diversification of ground-dwelling lizards on Hispaniola. Molecular-genetic data are used to examine the genetic relationships within and among five species of Leiocephalus and three species of Ameiva. Species- and population-level phylogenies are examined in the context of environmental data using Geographical Information Systems technology to test the hypothesis that environmental variation plays a significant role in species formation among ground-dwelling lizards. Geological information is used to test the role of historical environmental fragmentation in lizard diversification. Local environmental variation is used to examine geographic variation in morphological characteristics thought to have adaptive significance.This study explicitly identifies environmental and population-genetic conditions that promote and maintain an evolutionarily diverse island fauna. The study integrates data from diverse sources to test hypotheses about the diversification of an understudied fauna. This study also benefits local students by fostering international collaborations in the Dominican Republic and enhancing understanding of evolutionary and conservation biology.