The role of cross-generational fitness tradeoffs in the evolution of mating behavior

In many species, females with unlimited access to males have shorter lives and produce fewer offspring than females with limited exposure to males. Based on this finding, one would expect that natural selection would reduce the frequency of female multiple mating. Yet, multiple mating is widespread among nearly all species in the animal kingdom. A possible explanation is that females that mate more might offset the costs of mating if they produce higher quality offspring. The following dissertation was designed to test the validity of this hypothesis using the fruit fly, Drosophila melanogaster .; In Chapters 1 and 2, I found that increasing maternal mating frequency lowers maternal survival and fecundity but increases the early-life fecundity and lifetime reproductive success (LRS) of daughters. I evaluated these results using cost/benefit models based on inclusive fitness, and on the economic principle of compounded growth, to determine whether frequent mating increases offspring fecundity enough to compensate for the reduced survival and fecundity of mothers. The results of these models indicate that the costs of frequent mating are offset by benefits to daughters. Unlike previous work in Drosophila, that has argued that increased mating frequency evolves because it benefits males to the detriment of females, this study indicates that increased mating frequency evolves because there are indirect benefits for females.; I discovered two novel mechanisms for how maternal mating frequency increases daughter fecundity. Accessory gland proteins (Acps) in male seminal fluid are thought to be the primary factors driving costs of mating to females. In Chapter 3, I found that both the act of mating and maternal exposure to Acps increased early-age fecundity of daughters through parental effects. This finding indicates that molecules that drive costs of mating to females also increase daughter-fitness. Maternal mating also influences the genetic quality of offspring. In Chapter 4, I found that multiple mating increases the rate of genetic recombination, which increases the genetic variability of offspring. A single bout of mating triples the recombination rate of females. These studies indicate that cross-generational studies are necessary to understand the evolution of mating behavior.