The effects of a chromosomal inversion on adult size and male mating success in the seaweed fly, coelopa frigida

Abstract

An association is reported between the α/β inversion polymorphism on chromosome I and adult size as assessed by the length of wings, αα flies are larger than ββ flies, with heterokaryotypes intermediate, and the differences are more marked in males than in females. Laboratory mating experiments were performed in which a single female was given a choice of two males. By examining the genotypes of the progeny larvae, it is shown that the larger male is successful in a significantly greater proportion of trials than the smaller one. This mating success is dependent on the size difference between the males and on the female size. Together these observations suggest an indirect influence of the inversion on male mating success. The possible relevance of this effect to the maintenance of the inversion polymorphism in natural populations is discussed. © 1982 The Genetical Society of Great Britain.