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Date Permissions Signed

11-14-2008

Date of Award

2008

Document Type

Masters Thesis

Degree Name

Master of Science (MS)

Department

Biology

First Advisor

Peterson, Merrill A., 1965-

Second Advisor

Hooper, David U., 1961-

Third Advisor

Vyvyan, James R.

Abstract

The reinforcement of pre-mating barriers in a hybrid zone often leads to reproductive character displacement. However, it can be difficult to link evidence for reproductive character displacement with specific traits important to mate choice. I analyzed the cuticular hydrocarbon (CHC) profiles of Chrysochus cobaltinus and C. auratus to assess whether these pheromones are responsible for the previously observed pattern of reproductive character displacement in the Chrysochus hybrid zone. I found significant CHC divergence between the species, but overall CHC divergence was not higher among hybrid zone populations. However, CHC profiles of sympatric C. cobaltinus were more homogenous and were significantly different from CHC profiles of conspecific allopatric populations near the hybrid zone. Allozyme based analyses of population structure indicated that genetic relatedness is not a likely explanation for C. cobaltinus CHC variation. When controlling for genetic distance, there was greater CHC divergence between sympatric populations and allopatric populations near the hybrid zone, compared to divergence between sympatric populations and allopatric populations far from the hybrid zone. This result indicates that populations in the vicinity of the hybrid zone may be responding to unique selection pressures. In addition, species-specific differences in CHC variation support the hypothesis that reinforcing selection on females is species-specific. Overall results provide partial support for the hypothesis that previously observed reproductive character displacement is due to changes in Chrysochus CHC profiles. Further research on the compounds governing mate choice will provide more information on the evolution of reproductive barriers in this system.

Type

Text

DOI

https://doi.org/10.25710/445f-7d89

Publisher

Western Washington University

OCLC Number

312181562

Subject – LCSH

Chrysomelidae; Chrysomelidae--Sexual behavior; Hybridization; Evolution (Biology)

Format

application/pdf

Genre/Form

masters theses

Language

English

Rights

Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this thesis for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.

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