Date of Award

12-2004

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Ecology and Evolutionary Biology

Major Professor

Susan E. Riechert

Committee Members

Christine R. Boake, Gary F. McCracken, Randall L. Small

Abstract

Identifying the influence of history on the diversity of life is an important goal of evolutionary biology, whether it is an historical event that is extrinsic to the organism such as past climate change or an intrinsic event such as a single switch in behavior. Phylogenetic trees offer an indirect record of the history of diversification in a group of organisms and can be used in conjunction with other information to deduce the multiple roles of history affecting a particular group. Intra- and inter-specific phylogenetic relationships in the spider genus Agelenopsis Geibel (Araneae: Agelenidae) were analyzed using sequence data from two mitochondrial genes, cytochrome oxidase I (COI) and 16S ribosomal RNA for 12 out of 13 described species as well as a potential new species. These data were used to address a number of questions regarding biogeography, speciation, and evolution of habitat-use. Concerning biogeography, patterns and levels of sequence variation were consistent with the hypothesis that Pleistocene climate change affected geographic distribution and evolutionary diversification patterns within A. aperta. Speciation patterns were uncovered regarding species monophyly, geography of speciation, and the rejection of a putative hybrid species. Finally, a potential interaction of history and natural selection was identified when looking at the evolution of habitat use within and among Agelenopsis species. It was found that riparian living arose once in the genus with a single switch to arid living. Subsequently, three species of Agelenopsis displayed multiple switches back to riparian living. The findings of this dissertation point to a multitude of evolutionary questions that should be addressed and suitability of Agelenopsis as a model system in evolutionary biology.

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