Dominance, survival, and enzyme polymorphism in dark-eyed juncos, Junco hyemalis
Baker, MC.; Fox, SF.
Evolutio 32(4): 697-711
The genetic structure of wintering populations of dark-eyed juncos was examined by starch gel electrophoresis. Among different flocks and different years, we found only mild heterogeneity Of 18 loci examined, these populations of the junco are polymorphic at 16.6%. The average number of variants per polymorphic locus is 3.33, and the average proportion of loci heterozygous for an individual is 0.053 Using color marked birds, we established that in the dominance hierarchy of a flock, high ranking birds were usually heterozygous for the enzyme L-leucylgly-cylglycine peptidase. Employing four experimental flocks captive in aviaries, we found that under conditions of food restriction dominant birds were likely to show higher survival than low ranking birds. In order of decreasing importance, 'survival' in the aviaries (defined as the maintenance of body weight above a criterion threshold) could be predicted from dominance rank, genotype, body weight, sex, bill width, bill length, hood coloration, and tarsal length. The single best predictor of high dominance rank was long wing length.