Publication Date



Barry Chernoff


Biology (BIOL)


English (United States)


The effects of habitat fragmentation can have important impacts on the genetic structure and morphological variation within a species. I studied the divergence of body shape among populations of the Hardhead Silverside, Atherinomorus stipes, living in the Florida Keys and Belize Cays. The morphometric analyses included a total of 389 specimens from seven populations in Belize (n = 175) and eight populations in Florida (n = 214). Principal component analyses of 31 interlandmark distances and relative warp analyses of 15 landmarks around the body indicated that there were highly significant differences in body shape: i) between the populations living in Florida and Belize; and ii) among populations living within Florida and within Belize. A most surprising and potentially important result was discovered about the relationship between body shape and haplotype of the mitochondrial nd2 gene. Analyses of variance on individuals from Belize rejected the null hypotheses that there would be no difference in body shape among groups of individuals with a particular haplotype. It is not obvious why variation in body shape should be explained by nd2 haplotype. Linear regression analyses of pairwise morphological distances on geographic distance indicated that the Isolation by Distance model did not explain morphological divergence in Belize populations; however, the model explained some of the morphological divergence in Florida populations. These results suggest that A. stipes maintains a relatively discrete population structure associated with a patchy landscape that has a strong influence on the phenotypic expression of body shape.

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