Dissertation Research: Cooperation and the Covariance between Genetic Monogamy and Limited Dispersal

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Many animals, including humans, live in extended family groups where both parents and mature offspring share the responsibility of caring for young. This type of social system, called cooperative breeding, is frequently associated with monogamy across a diversity of animal groups. This association is thought to result from the fact that helpers in monogamous groups share on average 50% of their genes with their full siblings - the same proportion they share with their own offspring. Therefore, from a gene's eye view, helping can be as good a strategy as reproducing independently when helpers can assist in rearing full siblings. Although staying near home to help can be beneficial in some circumstances, the benefits of cooperating could be reduced or even cancelled out if helpers find themselves competing with close relatives for resources when they do not disperse from the area where they were born. This project investigates the contexts in which cooperation and competition occur to determine if animals can balance these costs and benefits through dispersal behavior. This proposal also tests a novel alternative explanation for the observed association between monogamy and cooperation, asking whether this relationship could be due to environmental factors that similarly influence both mate fidelity and helping behavior. The role of sibling relatedness in the evolution of cooperation is of major interest in the field of behavioral evolution, and the studies proposed here could have profound influences on our understanding of family-based cooperative societies, such as our own. The project will also provide multiple training opportunities for graduate and undergraduate students in a range of modern scientific skills, including the use of the most cutting edge DNA sequencing techniques. The work will be shared with the public through a community science festival and scientific illustration classes.This research investigates the relationship between mating systems and social systems using cooperative bess beetles as a model organism. First, fine-scale population structure will be assessed to test the hypothesis that beetles cooperate locally within their highly related family group before dispersing to compete globally with unrelated individuals, allowing them to avoid the costs of competing with kin while maximizing the benefits of cooperating with relatives. The second objective in this study will test the novel hypothesis that certain environments may favor both monogamy and cooperation simultaneously, leading to a correlation between mating and social system that is consequential rather than causal. Conceptually, this hypothesis suggests that the terms in Hamilton's Rule (rB-C0) may covary in certain environments. Specifically, this study will test whether a single ecological factor, low resource density, reduces the costs (C) of helping (by increasing the costs of dispersal) while simultaneously increasing the relatedness between helpers and their siblings (r) by reducing extra-pair paternity. To assess this possibility, paternity and dispersal will be investigated in response to resource density in both natural and experimental populations of bess beetles. The results of this study could suggest that the terms in Hamilton?s Rule are not modular, but rather covary under certain conditions, changing the way we understand both the correlated evolution of social and mating systems as well as the association between relatedness and cooperation.