Effects of Inbreeding and Salinity Stress on Population Dynamics of Eastern Mosquitofish

Abstract

This study examines the effects of inbreeding, environmental (salinity) stress, and their interaction on the population dynamics of the eastern mosquitofish Gambusia holbrooki. I reared mosquitofish having one of three levels of inbreeding (f = 0, 0.125, and 0.25) in artificial ponds containing either 0‰ or 6.5‰ salinity. Populations in the 6.5‰ treatments were characterized by significantly lower growth rates, smaller population sizes, smaller juveniles, larger females, and fewer juveniles relative to adults than populations in the 0‰ treatments. The level of inbreeding did not affect population size or growth rate in either salinity treatment. In the 0‰ treatments, there were significantly fewer females and significantly more males and juveniles in the most inbred group (f = 0.25) compared with the group of unrelated individuals. These results suggest that inbreeding effects at the population level may be a relatively minor concern for some organisms. Small, isolated populations or those with low fecundity and survival rates may be more susceptible to inbreeding.