Lack of association between allozymic variation and social dominance in free-living White-throated Sparrows

Abstract

This study examined possible associations between allozymic variation in metabolic enzymes and social dominance or survival in a large free-living population of wintering White-throated Sparrows (Zonotrichia albicollis). Electrophoresis of 15 enzymes resolved from muscle biopsies from 173 sparrows revealed nine enzymes with some variation. Two of these (PGM and 6-PGD) showed substantial variation, with the frequency of the common allele below 0.9. During two seasons dominance interactions among the biopsied birds were observed at three feeding stations. There was no association between social dominance (percentage of opponents dominated) and genotype at the two most variable loci or overall proportion of heterozygotes at either the two most variable loci or the seven most consistently scored loci. Older birds were more likely than expected to be heterozygous at both the PGM and 6-PGD loci, but heterozygotes did not return more frequently than homozygotes in subsequent years. Although we cannot exclude a weak association of dominance and isozyme variability, we can conclude that social dominance during winter lacks any strong relationship with variation at loci for metabolic enzymes.