Demographic and Genetic Characteristics of Multiply Inseminated Female Mosquitofish (Gambusia affinis)

Abstract

While the occurrence of multiple insemination has been documented for a variety of species in the fish family Poeciliidae, few studies have been designed to characterize potential demographic and genetic differences among females inseminated by one male type or more than one male genotype. Electrophoretic analysis of 200 female mosquitofish (Gambusia affinis) and their embryos indicated that females which were inseminated by more than one male genotype were significantly longer than females inseminated by only a single male type. A positive regression between female SL and fecundity is typical of mosquitofish. As a consequence, males may preferentially select and compete for larger females, thus increasing the probability of multiple insemination among longer females. Multiply-inseminated females were also more heterozygous than females which mated with single male types and their offspring exhibited greater genetic diversity than expected compared to offspring derived from random single matings among adults in the population. Because female mosquitofish, especially larger individuals, have been shown to be common among dispersers, the widespread success of this species as a colonizer of diverse habitat types may be explained, in part, as a function of female reproductive strategy which includes multiple insemination and sperm retention.