Abstract
Organisms express phenotypic plasticity during social interactions. Interacting phenotype theory has explored the consequences of social plasticity for evolution, but it is unclear how this theory applies to complex social structures. We adapt interacting phenotype models to general social structures to explore how the number of social connections between individuals and preference for phenotypically similar social partners affect phenotypic variation and evolution. We derive an analytical model that ignores phenotypic feedback and use simulations to test the predictions of this model. We find that adapting previous models to more general social structures does not alter their general conclusions but generates insights into the effect of social plasticity and social structure on the maintenance of phenotypic variation and evolution. Contribution of indirect genetic effects to phenotypic variance is highest when interactions occur at intermediate densities and decrease at higher densities, when individuals approach interacting with all group members, homogenizing the social environment across individuals. However, evolutionary response to selection tends to increase at greater network densities as the effects of an individual's genes are amplified through increasing effects on other group members. Preferential associations among similar individuals (homophily) increase both phenotypic variance within groups and evolutionary response to selection. Our results represent a first step in relating social network structure to the expression of social plasticity and evolutionary responses to selection.
Highlights
Interactions among organisms are ubiquitous in nature
We focus on the number of connections observed among group members, and the degree to which individuals can bias the strength of their interactions with others that have a similar phenotype
We present both an analytic model and simulations extending previous work on social phenotypic plasticity to more general social structures
Summary
Interactions among organisms are ubiquitous in nature. For example, individuals interact with conspecifics when acquiring or defending food, refuges, or mates (Clutton-Brock, 1989; Giraldeau & Caraco, 2000; Huntingford & Turner, 1987; Krause & Ruxton, 2002), and with heterospecifics in mutualism, antagonism, and competition (e.g., Crowley & Cox, 2011; Miller, Ament, & Schmitz, 2014; Shuster, Lonsdorf, Wimp, Bailey, & Whitham, 2006; Thompson, 1982). In contrast to simpler models of social structure, social networks can capture variation in both the immediate social environment that individuals experience (i.e., who each individual interacts with directly) and the individuals’ positions within the overall social structure of the group (i.e., how central an individual is in stabilizing or favoring a particular social structure) Combining this greater realism when quantifying social structure, that is, the patterns of connections in a social network, with the ability to make formal predictions about phenotypic evolution has the potential to significantly expand our understanding of the evolution of social traits (Fisher & McAdam, 2017). When individuals express heterophily (disassortative association by phenotype), we expect indirect genetic effects to decrease the ability of the trait to exhibit change in response to selection
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