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The evolution of matrotrophy introduces the potential for genomic conflicts between mothers and embryos. These conflicts are hypothesized to accelerate the evolution of reproductive isolation and to influence the evolution of life history traits, reproductive structures, and genomic imprinting. In this dissertation, I describe a series of studies examining the expression and impact of parent-offspring conflict in natural populations of a highly matrotrophic poeciliid fish, Heterandria formosa In Chapter 2, I used data from a long-term field study of two H. formosa populations to examine whether population differences in offspring size are mainly due to differences in pre- or post-fertilization offspring provisioning. I found differences between populations in pre-fertilization offspring provisioning and larger differences in post-fertilization provisioning. These results establish population variation in H. formosa as a potential model for studying the costs and benefits that could modulate the evolution of matrotrophy. In addition, these results illuminate some of the costs and benefits associated with matrotrophy and offer insight into how matrotrophy influences the expression of other life history relationships. In Chapter 3, I used field data and laboratory crosses to test whether two important assumptions of parent-offspring conflict theory are met in H. formosa. Specifically, I tested whether offspring can influence the amount of maternal investment they receive and whether there is a trade-off between maternal investment into individual offspring and maternal survival or fecundity. Comparisons of life histories between two populations (Moore Lake and Wakulla Springs) demonstrated a trade-off between the level of maternal investment into individual embryos and maternal fecundity. Laboratory crosses between individuals from these populations revealed that offspring genotype exerts an influence on the level of maternal investment and affects maternal fecundity. These results show that the prerequisites for parent-offspring conflict to be a potent evolutionary force in poeciliid fishes are present in H. formosa. In Chapter 4, I tested the hypothesis that parent-offspring conflict can drive the evolution of asymmetrical reproductive isolation between populations with divergent mating systems using crosses between populations of H. formosa that differ in their level of polyandry (Trout Pond and Wacissa River). The results of this study support the prediction of an asymmetry in the rate of spontaneous abortion in reciprocal crosses with the highest rate occurring in crosses between females from a relatively monandrous population and males from a relatively polyandrous population. In Chapter 5, I used three microsatellite loci to characterize the mating systems of Moore Lake and Wakulla Springs to determine whether the crosses conducted between them in Chapter 3 represent a replicate test of the viviparity-driven conflict hypothesis. In Moore Lake there was low power to detect multiple paternity with these loci. However, 58 % of the females sampled carried multiply sired broods. In Wakulla Springs there was much higher power to detect multiple paternity and 65 % of females carried multiply sired broods. These results indicate that previously conducted crosses between Moore Lake and Wakulla Springs do not represent a replicate test of the viviparity-driven conflict hypothesis. In addition, they suggest that life-history divergence may be a better predictor of reproductive isolation between H. formosa populations than mating system divergence.

The Expression and Impact of Parent-Offspring Conflict in Natural Populations of the Least Killifish, Heterandria formosa. Available from: https://www.researchgate.net/publication/241826022_The_Expression_and_Im... [accessed Sep 26, 2017].