Phylogeography and diversification of Hispaniolan ground-dwelling lizards, Ameiva and Leiocephalus

This dissertation examines the prevalence of within-island forces driving the accumulation of lineage diversity and influencing historical demography in a guild of lizards on an individual Caribbean island, Hispaniola. Ameiva chrysolaema is broadly distributed across nearly all xeric to semi-mesic lowland regions of Hispaniola. Analyses of single and multilocus DNA sequence data indicate two separate episodes of genetic fragmentation, the first creating North, South and Central geographic lineages, and the second subdividing the Central lineage into East-Central and West-Central sub-lineages. All geographic fragmentation events are temporally and spatially congruent with the geographic locations of Pliocene (5.5--3 million years ago, mya) and Pleistocene (ca. 1.1 mya) sea inundations. East-Central and West-Central lineages have made secondary contact along a steep environmental gradient and have resumed gene flow, although the genetic interactions between lineages have been asymmetric.;Pleistocene climatic oscillations appear to have had the predominant influence on populations of Leiocephalus lunatus and L. personatus. Species distribution models of present and past environmental suitability suggest that climatic variation throughout the Pleistocene caused fragmentation and movement of suitable habitat for both species. All divergence events in both species occurred within the Pleistocene and completely predated the last glacial maximum. However, the broad agreement between genetic structure and paleodistribution model predictions suggests that similar geographic refugia were used repeatedly during cooler Pleistocene climatic conditions. Further, some lineages within each species are characterized by significant population expansion.;Five species of Ameiva and Leiocephalus are broadly co-distributed throughout the xeric lowlands of Hispaniola. A test of simultaneous divergence indicates that geographic lineages of Ameiva (A. chrysolaema and A. lineolata ) diverged in concert, while co-distributed lineages of Leiocephalus diverged both before and subsequent to Ameiva. Multilocus estimates of divergence times among lineages suggest sea inundation as a major contributor, although divergence between North and Central lineages of L. schreibersii is not compatible with this event. Within the Cul de Sac-Valle de Neiba (CSVN) and on the Barahona Peninsula, lineage divergence and demography were largely driven by Pleistocene climatic oscillations. Combination of paleodistribution modeling and divergence population genetic analysis indicates that the current co-distribution of species in the CSVN is a consequence of both concerted and unique responses to Pleistocene climate change.