Date of Award

5-2012

Type

Thesis

Major

Earth and Space Science - Environmental Science Track

Department

Earth & Space Science

First Advisor

Kevin S. Burgess

Second Advisor

William Birkhead

Abstract

Interspecific hybridization can lead to the evolution of a new hybrid species or extinction of parental species due to competition or excessive backcrossing, When parental populations differ in abundance, hybrids tend to backcross more frequently with the more abundant parent, resulting in asymmetrical introgression. The objective of this study was to determine the extent and apparent direction of hybridization between shoal bass {Micropterus cataractae), a rare endemic species to the Apalachicola drainage, and spotted bass (M. punctulatus), an introduced and more abundant species. Pelvic fin tissue (N = 130) was taken from bass species in the Chattahoochee River between Columbus, Georgia and Phenix City, Alabama and analyzed for hybridization using a combination of four microsatellite markers, morphometries, and mtDNA. While morphometries proved to be inadequate at confirming hybridization, microsatellite analyses identified 15.4% (N = 20) of bass samples as hybrids. Analysis also showed significantly more hybrids backcrossed to the more abundant M. punctulatus, suggesting asymmetrical introgression. Mitochondrial DNA were utilized to confirm asymmetrical introgression; instead, barcoding revealed the potential for three additional interspecific interactions involving M. floridanus (Florida bass), M. coosae (redeye bass), and Af. salmoides (largemouth bass). Although mtDNA analysis did not confirm hybridization between M. cataractae and M. punctulatus, interspecific hybridization does pose a threat to populations of M. cataractae and warrants additional research. To protect populations of M. cataractae, priorities should focus on restoring shoal habitat and if necessary augmenting existing populations with genetically, pure shoal bass from within their range.

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