Spatial and Temporal Patterns of Diversification in Leaf-toed Geckos (Phyllodactylidae: Phyllodactylus) throughout the Mexican Dry Forest.

摘要

Understanding the ecological and evolutionary processes responsible for shaping patterns of genetic variation in natural populations is a long-standing goal in molecular ecology. Although an extensive number of recent studies focus on patterns and processes throughout tropical rain forest ecosystems, substantially less effort has been placed on tropical dry forests (TDFs); a habitat known to harbour a large percentage of Earth's diversity. In this thesis I use leaf-toed geckos of the genus Phyllodactylus to understand both the historical and contemporary processes influencing diversification throughout Mexico's TDFs. In Chapter 2 I isolate and characterize microsatellite markers for the gecko P. tuberculosus. Chapter 3 uses these loci to conduct a landscape genetic analysis of the species near Alamos, Sonora. I find that the inclusion of landscape variables explains more genetic variance versus Euclidean distance alone. Chapter 4 examines the evolutionary history of the P. tuberculosus group throughout western Mexico. Results suggest that habitat and climate shifts during the Miocene and Pleistocene were important divers of diversification. Chapter 5 uses microsatellite and mtDNA markers to compare historical and contemporary demographic parameters in P. tuberculosus. I find evidence for low historical gene flow and high female philopatry, recent reductions in population sizes, and higher correlations between landscape and contemporary gene flow versus historical gene flow and mtDNA divergence. In Chapter 6 I examine the biogeographic and taxonomic consequences of the dynamic history of Baja California. My phylogenetic results provide evidence for a trans-peninsular seaway in the Isthmus of La Paz region and suggests that P. xanti nocticolus warrants species status. My results also suggest the possibility of a seaway near the Loreto area that needs to be evaluated further. By combining multiple molecular marker-types and analytical methods, this thesis adds to our understanding of diversification processes throughout the threatened Mexican TDF.