Evolutionary consequences of indirect genetic effects

The evolutionary genetics of social interactions are, for the most part, poorly understood. Recent theoretical work that includes indirect genetics effects in analyses of social evolution has allowed for a more complete model for the genetics of social interactions. Indirect genetics effects (IGEs) occur when the expression of traits in one individual is affected by genes in another individual. The inclusion of IGEs in models of the evolution of social interactions has facilitated an understanding; of the interactive nature of social characters.; Using models of IGEs I look at three fundamental questions in social evolution: (1) how do the phenotypic effects of variation in the quality of resources provided by parents (i.e., maternal and/or paternal effects) affect the sexual selection process, (2) what are the evolutionary consequences of interactions between parental and offspring genomes and (3) how can the fitness effects of social interactions be understood as a separate entity from natural selection. I precede these three sections with an introductory chapter, followed by a conceptual review of indirect genetic effects.; Together the chapters presented here illustrate the value of using an indirect genetic effects perspective in studying the evolution of social interactions. By incorporating IGEs into sexual selection I have identified an additional source of honest signals of mate quality and I provided a framework for understanding how sexual selection can drive the evolution of parental investment. Using a quantitative genetic model for the maternal-offspring interaction I identify a potential mechanism that may explain the ubiquity of large genetic corrections between maternal and offspring genetic effects. Using this same model I also provide a means of analyzing what these genetic correlations may tell us about how parental and offspring traits function together to affect offspring fitness. In a similar model that uses a quantitative trait locus approach I show that the maternal-offspring interaction can produce epistasis between QTLs in traits expressed early in. The QTL model also identifies maternal effects as a potentially important source of rugged adaptive topographies. Finally I show how characters mediating social interactions can act as both the agent and target of selection. This model of social selection allows for the separation of genetic and fitness parameters in the analysis of social evolution, and unifies existing theoretical analysis of social selection.