Award: OCE-0929057

Families are a unique arena where conflicts of interest often arise between males and females, between parents and offspring, and among siblings. The theory of kin selection, which underlies much of our understanding of the evolution of coopertation and conflict in non-human biological systems, predicts that the magnitude of these conflicts fundamentally depends on a species' mating system, specifically how many times a female mates, and with how many different males. When females mate with a single male, offspring will be full siblings and levels of conflict relatively low. At the other extreme, when females mate with multiple males, offspring are more likely to be half-sibs, and more likely to harm each other, either directly or indirectly. In addition, conflcts between parents and offspring over allocation of parental resources are also greatest when offspring are half-, rather than full-, sibs. These core predictions have rarely been rigorosuly tested, despite their importance for understanding ecologically and economically important traits, including seed size in crop plants, offspring size in many animals, and levels of parental investment in offspring. Using experiments and comparisons of natural populations that have different mating systems, this project demonstrated for the first time how variation in the mating system, through its effects on family conflict, accounts for variation in offspring size of an ecologically important, predatory marine snail (Nucella ostrina). As predicted, we found a strong positive relationship between the number of males a female mated with and levels of variation in the size of her offspring: the more fathers, the greater the variation. In addition, when we experimentally crossed snails from populations with different mating systems, few hybrid offspring were produced. Therefore, differences in mating systems may be an important engine driving biodiveristy in the sea. Overall, this project generated novel insights into the complex forces, notably family conflict, that drive the evolution of ecologically critical traits, in this case ofspring size. The project also provided training and professional development for 9 high-school biotechnology interns; >20 undergraduate researchers, including 2 female African American research fellows from Howard University and 3 Hispanic women; 2 Ph.D. students; and 2 postdoctoral fellows, both of whom are now faculty members at major research universities. Beyond the research community, the project's findings have been disseminated to the public through press releases, public forums, and coverage by national media. Last Modified: 12/05/2014 Submitted by: Richard K Grosberg