Award Date

1-1-2008

Degree Type

Thesis

Degree Name

Master of Science (MS)

First Committee Member

Javier A. Rodriguez

Second Committee Member

John Klicka

Number of Pages

51

Abstract

Exploring the factors that influence the distribution and diversification of organisms is essential to the field of evolutionary biology. Molecular examination across a species' distribution may result in the discovery of differentiated populations that, when interpreted in the context of past events (e.g. climate change), may elucidate the causal mechanisms. Comparative phylogeographic studies have revealed both similar and disparate genetic patterns among co-distributed organisms, although similar geographic patterns may differ greatly in temporal scale and thus in the magnitude of genetic differentiation. Studies of diverse taxa occurring across the southeastern United States have revealed several common patterns of intraspecific divergence - defined mainly by river and mountain boundaries; The Eastern Towhee (Pipilo erythrophthalmus) is a sparrow found in scrub, thicket, and forest edge habitat across the eastern United States. Eastern towhee consists of three main phenotypic groups: red-eyed continental forms, "white-eyed" Florida peninsular forms (referred to in the text as yellow-eyed), and a putative hybrid form with variable eye-color. I sequenced the complete ND2 mitochondrial DNA gene to determine whether these morphologically separable groups are also genetically distinct. Reciprocal monophyly is lacking between red and yellow-eyed birds. However, several statistically significant analyses support genetic differentiation of yellow-eyed populations. This divergence between red-eyed and yellow-eyed populations is estimated to have originated late in the Pleistocene epoch. Very low estimates of migration are consistent with a scenario of incomplete lineage sorting rather than ongoing gene flow. Overall, these results reveal a common finding of intraspecific genetic divergence in a southeastern U.S. taxon. Such differentiation is rare however within avian taxa. In addition, this study supports an uncommon geographic pattern of divergence, that is, divergence between peninsular Florida and mainland populations.

Keywords

Alleni; Assessment; Eastern; Erythrophthalmus; Eyed Molecular; Pipilo; Towhee; Validity; White

Controlled Subject

Genetics; Zoology

File Format

pdf

File Size

0.97 MB

Degree Grantor

University of Nevada, Las Vegas

Language

English

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