Relationships between genetic variation and body size in wintering Mallards

Abstract

Mallards (Anas platyrhynchos: n = 282) wintering in the Southern High Plains (SHP) of Texas were collected from 15 October 1988 to 7 February 1989. Lipid and fat-free body masses were determined for all Mallards. Birds were surveyed electrophoretically for genetic variation at 30 biochemical loci. Our objective was to determine if structural size, fat mass, or fat-free mass of Mallards were related to multilocus genetic variation. Wing-chord length, our estimator of structural size in Mallards, was shortest in female Mallards with the highest levels of genetic variation. Fat mass and fat-free mass of Mallards (corrected for size) were not related to multilocus heterozygosity. Mixtures of morphologically and genetically differentiated breeding populations of Mallards on the SHP wintering area may explain the relationships between multilocus heterozygosity and size we detected in these birds.