Dispersal, Reproductive Strategies, and the Maintenance of Genetic Variability in Mosquitofish (Gambusia affinis)

Sperm storage and multiple insemination were documented in Gambusia affinis from a natural population and by experimental matings using genetic markers. There was unequal paternal contribution from new and recent matings although sperm stored from previous matings continued to be represented in subsequent broods. Analysis of demographic characteristics of mosquitofish residing in and dispersing from an area of high density showed that 76% of the dispersing individuals were adult females, and 46% of these were in the later stages of reproduction. The high levels of genetic variation found in this species would not be predicted from the population characteristics but can be explained by dispersal, sperm retention, and multiple insemination.