Field experiments on the distributions of eggs of different phosphoglucomutase (PGM) genotypes in the yellow dung fly Scathophaga stercoraria (L.).

Female yellow dung flies can, in the laboratory, influence the probability that stored sperm from different males are used to fertilize eggs. This matches offspring phosphoglucomutase genotypes to the environmental conditions in which the larvae will grow, increasing larval growth success. We conducted field experiments in which dung topology or shading conditions were controlled. The proportions of the five common phosphoglucomutase alleles in eggs laid in north-facing slopes or in shaded conditions was related to their electrophoretic mobility. We suggest that females lay eggs of different genotypes, by appropriately choosing their fathers, in different places.