The Genetics of Parental Care Behavior

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The Genetics of Parental Care BehaviorEdmund D. Brodie IIIIThe genetic control of behaviors involved in social interactions is difficult to understand because traits of one individual can be influenced by traits of individuals with which it interacts. Such influences have traditionally been considered sources of environmental variation in phenotypes, but this view ignores the possibility that the 'environmental' influences can themselves be genetically determined. The result is a complex web of genetic effects that reach from traits in one individual to traits in another and allows environmental sources of variation to contribute to evolutionary change. Indirect genetic effect (IGE) theory provides a framework for understanding such complex inheritance in terms of the quantitative genetic parameters and equations traditionally used to understand evolutionary processes. The presence of IGEs can substantially alter evolutionary dynamics and outcomes, but virtually no empirical studies of IGEs are available with which to evaluate the general importance of IGEs in behavioral evolution. Parental care behavior is one of the most common examples of social interactions that can generate IGEs. The behavior of both parents and offspring determines how much care parents provide, and parental care in turn influences many traits in offspring. If parent and offspring components of parental care are genetically variable, IGEs exist and can affect the evolution of parental care. The proposed research will investigate the genetics of maternal provisioning in the burrower bug, Sehirus cinctus. Parental care in burrowers is limited to females, which provision their offspring with fruits from mint plants as the sole source of nutrition. Previous research has shown that burrowers are an ideal system for studying the genetics of parental care because they can be readily cross-fostered, reared, and bred in captivity. The proposed work is divided into two parts designed to determine how genes in mothers and offspring interact to determine the inheritance of parental care behavior. Project 1 is an experimental investigation of how maternal care influences offspring traits that will reveal how traits in one generation influence traits in the next. Project 2 combines a quantitative genetic breeding design with manipulative cross-fostering experiments to measure the relative importance of genes in parents and offspring in determining provisioning. This project will also determine patterns of genetic variation and covariation among parent and offspring components of provisioning behavior. Genetic variation is a requisite for the evolution of any trait. IGE theory recognizes that genetic (co)variation for interacting phenotypes (e.g., parental care) need not be direct, but rather may exist through indirect pathways from social partners. Specific results from each project will be used to test assumptions and predictions of phenotypic models of parental care evolution. Moreover, this work will represent the first quantitative genetic study of parental care behavior to consider the importance of social context.