Term of Award

Fall 2006

Degree Name

Master of Science in Biology (M.S.)

Document Type and Release Option

Thesis (open access)

Department

Department of Biology

Committee Chair

Quentin Fang

Committee Member 1

Denson K. McLain

Committee Member 2

none

Abstract

Author's abstract: The Atlantic sand fiddler crab, Uca pugilator, is an extremely abundant fiddler crab found along the eastern and Gulf coast of the United States. Fiddler crabs have a life cycle with an obligatory planktonic larval phase of 30-90 days, which might be expected to lead to widespread larval dispersal and consequent genetic homogeneity over considerable distances. However a large amount of morphological and behavioral variation is found between northern and southern populations along the eastern coast. This study was undertaken to determine the population genetic structure of U. pugilator and to determine whether these differences may have a genetic basis. The population structure of the fiddler crab was analyzed using 576 individuals collected from 12 sites along the eastern coast. PCR-base single stand conformation polymorphism (SSCP) was used to analyze segments of the mitochondrial 16S rRNA and the nuclear internal transcribed spacer 1 (ITS1) genes of these individuals. The ITS1 marker did not prove to be informative when screened by SSCP for this study. The 16S marker revealed a moderate amount of population structure (FST = 0.292) between populations. The results of this study reveal frequent gene flow between nearby localities, but reduced levels between populations separated by large distances. Despite the potential for high dispersal by planktonic larvae, population differentiation and isolation by distance was found between populations U. pugilator. Northern and southern regions are separated by a genetic distance of 0.3866 suggesting the potential for morphological and behavioral differentiation across the species range. INDEX WORDS: Uca pugilator, Fiddler crab, Population structure, Gene flow, Larval dispersal, Single-stand conformational polymorphism, 16S rDNA, ITS-1

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