SEXUAL SELECTION, VIABILITY SELECTION, AND DEVELOPMENTAL STABILITY IN THE DOMESTIC FLY MUSCA DOMESTICA

Associations between developmental stability, sexual selection, and viability selection were studied in the domestic fly Musca domestica (Diptera, Muscidae). Developmental stability of the wings and tibia of flies of both sexes, measured in terms of their level of fluctuating asymmetry, was positively associated with mating success in free ranging populations and in sexual selection experiments. Mated individuals may have obtained indirect fitness benefits from sexual selection of two different kinds. First, the entomopathogenic fungus Enthomophthora muscae (Zygomycetes, Entomophthorales) infects and kills adult domestic flies, and flies dead from fungus infections had more asymmetric wings than flies dead for other reasons. Experimental deposition of fungus spores on uninfected flies demonstrated that flies with asymmetric wings were more susceptible to fungus infections than flies with symmetric wings. Second, domestic flies were frequently eaten by insectivorous barn swallows Hirundo rustica, and flies depredated by birds had more asymmetric wings and tibia than surviving flies.