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

管理岛屿上的生物多样性(某一特定地方存在的物种数量)的过程通常被认为是从其他地区殖民并在一个岛屿内灭绝。然而，大型岛屿可能包含许多物种，这些物种的近亲只出现在同一个岛屿上，这表明岛内物种的存在。岛内物种形成可能是地理环境碎片化事件和生境类型的空间异质性造成的。本论文探讨了这两个因素在西斯帕尼奥拉地栖蜥蜴进化多样性中的作用。利用分子遗传学数据分析了五种细头目属和三个种间的亲缘关系。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面蜥蜴物种形成中的重要作用这一假说。地质信息被用来测试历史环境碎片化在蜥蜴多样性中的作用。局部环境变异被用来检验被认为具有适应意义的形态特征的地理变异。这项研究明确地确定了促进和维持进化多样性的岛屿动物的环境和种群遗传条件。这项研究综合了来自不同来源的数据，以检验关于一个未被研究的动物群多样化的假设。这项研究还通过促进多米尼加共和国的国际合作和加强对进化和保护生物学的理解，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.