Male quality influences intersexual dynamics, but not female intrasexual competition, in a monogamous, biparental fish

Female preference for higher quality males can influence both intrasexual and intersexual dynamics. In species with biparental care, male quality can influence not only the female's initial gametic investment but also the amount of care each parent provides to the offspring. Here, I describe studies of female reproductive investment in response to male size, an indicator of quality, and the effect of female intrasexual selection on parental behavior in the convict cichlid (Amatitlania siquia), a monogamous, biparental fish.;In Chapter 1, I observed breeding patterns in a natural population in Costa Rica and found that females increased their parental care when paired with larger males. Male size was positively correlated with offspring number, indicating a benefit to females from pairing with larger males. In Chapter 2, using a controlled breeding experiment, I investigated trade-offs in female fecundity and parental care within and between breeding events in response to male size. I found that females initially paired with small males had a greater probability of failing to successfully breed. Females did not increase their fecundity when paired with large males, but did increase their parental care and defensive behaviors. However, females did not benefit from pairing with larger males because they had fewer offspring. Male size did not significantly affect female parental care behavior during the second breeding, and fecundity again did not differ between females paired with small and large males. In Chapter 3, I presented breeding pairs with non-reproductive and reproductive female conspecific intruders. I found that parental females behaved more aggressively towards reproductive intruders, which were a threat to their mating status, compared to non-reproductive intruders, which were only a threat to their offspring. Female size, rather than male size, predicted parental female response to intruders, with small females behaving more aggressively. Males preferred to associate with the reproductive intruder, as it represented a potential new mate.;The results of this dissertation demonstrate that females increase their parental care, but not their fecundity, for larger males. Moreover, females appear to use their prior breeding experience when allocating resources to the current reproductive event, as females did not increase their parental care when paired with large males during their second mating because large males failed to provide any benefits during the initial breeding. Male quality influences intersexual dynamics, but not intrasexual interactions, suggesting that females may be altering their response to the threat of male desertion. Overall, these results suggest that increased female investment may stabilize the pair-bond between the parents, which ultimately increases female reproductive success.