| It is now known that females of many taxa, including turtles, often mate multiple times within a breeding season and produce clutches with mixed paternity. The reproductive biology of turtles, which includes nest site fidelity and the ability to store viable sperm for long periods of time, makes them particularly interesting subjects for research on mating patterns and paternity outcomes. Unlike the more extensively studied birds, mammals, or insects, female turtles also do not gain any direct benefits from mating, nor do males provide parental care. Thus, the mating preferences of females presumably reflect genetic differences among mates rather than the influence of any social or resource-based factors. We used microsatellite markers to determine the paternity of over 200 painted turtle clutches from a population on the Mississippi River. Our sample includes clutches from some individual females who returned to the nesting area multiple times over several consecutive years, allowing us to examine patterns of sperm storage and use by females both within and across seasons. Results from this analysis show that female turtles regularly use stored sperm to fertilize eggs over several consecutive breeding seasons. Because we were able to reconstruct multi-locus paternal genotypes from many of the clutches, and these genotypes identify individuals uniquely, we were also able to use mark-recapture methods to estimate the number of mates in the breeding population. The large population size indicated at our study site supports our conclusion that females often store sperm (as opposed to the alternative hypothesis that they might remate with the same male). Finally, we used data on clutch sizes and hatching success to test the effects of a female's mating behavior on her overall reproductive fitness. These data indicate that multiply sired clutches are significantly larger than multiply sired clutches are significantly larger than those sired by a single male, suggesting male preference for large females as mates. |
