Genetic Variation and Population Structure in the Damselfish, Stegastes fasciolatus, Throughout the Hawaiian Archipelago

Abstract

Samples of the Pacific damselfish, Stegastes fasciolatus, were collected from localities throughout the Hawaiian Archipelago (Midway, Maro Reef, French Frigate Shoals, Oahu and Hawaii) and subjected to starch gel electrophoretic analysis of 44 enzyme-coding loci. Eight loci (adenosine deaminase, glucosephosphate isomerase-A and -B, glycerol-3-phosphate dehydrogenase-A, hexosediphosphatase, peptidase-A, phosphogluconate dehydrogenase and phosphoglucomutase) were polymorphic. With one exception, all loci at all localities were in Hardy-Weinberg equilibrium. The average heterozygosity across all loci was 0.046 for the species. Allele frequencies at all eight loci were stable over a 12month period at Hawaii where two samples were taken. Allele frequencies at all eight loci were remarkably constant throughout the Archipelago-a linear distance of approximately 2,500 km. Furthermore, with the exception of a few very rare alleles, all populations exhibited the same spectrum of alleles at each locus. Whether the localities are analyzed pairwise or as two major groups-main Hawaiian Islands (Oahu and Hawaii) vs Northwestern Hawaiian Islands (Midway, Maro Reef and French Frigate Shoals)the data provide no evidence of subpopulation differentiation. Indeed, the homogeneity of allele frequencies at the eight polymorphic loci argues strongly for the existence of a single large panmictic population of Stegastes fasciolatus throughout the Hawaiian Archipelago.