Award Date

Spring 2010

Degree Type

Dissertation

Degree Name

Doctor of Philosophy in Biological Sciences

Department

Life Sciences

Advisor 1

Brett R. Riddle, Committee Chair

First Committee Member

John Klicka

Second Committee Member

Javier A. Rodríguez

Third Committee Member

Gary Voelker

Graduate Faculty Representative

Andrew Kirk

Number of Pages

247

Abstract

Genetic differentiation within and between species often coincides with significant geological or climatic changes that have shaped the sizes and locations of their geographic ranges and altered the connectivity between populations over time. Across western North America, many endemic taxa experienced high levels of initial divergence associated with geological transformations of the Neogene, with subsequent diversification and geographic structuring of populations associated with climatic changes during the Quaternary. As such, we can use a combination of molecular markers and genetic analyses to effectively examine the evolutionary and biogeographic histories of populations, species, and regional biotas whose signatures of differentiation are driven by the older geological events as well as more recent episodes of climatic change. Much of western North America is composed of a mosaic of regional deserts and associated aridlands separated from one another by a number of isolated mountain ranges. I employ a suite of phylogenetic, phylogoegraphic, and population genetic analyses, in combination with ecological niche modeling, to examine the biogeographic history of antelope squirrels (Ammospermophilus), western pipistrelle bats (Pipistrellus hesperus), and Uinta chipmunks (Neotamias umbrinus) in western North America. Antelope squirrels (Ammospermophilus) include five species collectively widespread throughout the North American deserts. Data presented herein support the hypothesis that early divergences of the three major extant lineages within this genus were driven by the initial formation of the deserts and the uplift of mountain ranges (e.g., the Sierra Nevada Occidental and Central Mexican Plateau) in the mid to late Neogene, and recent divergences were driven by ongoing geologic events in the late Pliocene (e.g., uplift of the Transverse Range). Genetic patterns reveal that populations were affected by habitat shifts associated with repeated glacial cycles throughout the Pleistocene, including the late glacial maximum (LGM). The western pipistrelle (Pipistrellus hesperus) is the smallest bat in North America and is distributed across many of the same habitats as Ammospermophilus. Within this species, there are three major geographically defined lineages with divergences dated to the early Pleistocene. These divergences were likely driven by the earliest glacial cycles in this region and genetic patterns indicate that populations of this species were confined to multiple glacial refugia during the LGM, reinforcing the already existing genetic patterns. The Uinta chipmunk (Neotamias umbrinus) is confined to montane habitats on mountain ranges throughout the intermountain west. Genetic analyses of populations within the Great Basin indicate that lineages in this region coalesce within the earliest Pleistocene, suggesting that most populations were restricted to the isolated mountain ranges at this time with little to no gene subsequent gene flow between them. While many mammals distributed across western North America have experienced a common set of abiotic factors, they have responded in unique ways leading to specific evolutionary and biogeographic patterns that are detectable in contemporary species and populations.

Keywords

Ammospermophilus; Antelope squirrels; Biogeography; Genetic diversity; Isolated populations; Neotamias umbrinus; North American deserts; Pipistrellus hesperus; Population genetics; Uinta chipmunks; Western pipistrelle bats

Disciplines

Biology | Molecular Biology | Zoology

Language

English


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