Saltz, Julia B.2021-09-022021-09-022021-082021-08-11August 202Wice, Eric Wesley. "Quantitative Genetics and Evolutionary Consequences of Variation in Social Group Structure." (2021) Diss., Rice University. <a href="https://hdl.handle.net/1911/111349">https://hdl.handle.net/1911/111349</a>.https://hdl.handle.net/1911/111349The structure of social groups -i.e., the patterning of interactions amongst individuals- is highly variable in nature, and can be important for nearly every aspect of an individual’s behavior and evolutionary fitness. How individuals are nested within their social groups can be modeled using social network analysis, which quantifies how direct and indirect social interactions shape the structure of social groups. While an individual’s position within a social network -i.e., social network position- is a frequent target of selection, we understand little about when social structure can respond to selection and evolve. For social structure to respond to selection and evolve, it has to have a genetic basis. Yet estimating the genetic basis of social network structure is not straightforward, because an individual’s position within a social network is inherently dependent on interactions between multiple individuals. To more fully understand the genetic basis of social network structure, we need to know how individuals’ own genotypes (direct genetic effects) and the genotypes of interacting partners (indirect genetic effects) shape social structure and each individual’s position within that structure. Testing these genetic components of variation is empirically challenging, as it requires controlling and replicating the genotypes of all social group members. Despite these challenges, studying the genetic basis of social group structure is necessary for furthering our understanding of the quantitative genetic causes and evolutionary consequences of variation in social group structure. Drosophila melanogaster flies provide a powerful system to address questions about the quantitative genetics and evolutionary consequences of social group structure, as we can control and replicate the genotypes of individuals in social groups and measure fitness effects across the lifespans of individuals. Using a combination of automated motion tracking software to quantify social interactions, and social network analysis to model the direct and indirect social interactions shaping social group structure, I address how direct and indirect genetic effects shape variation in social structure. I also address how selection acts on genetic variation in social network positions, across variable social and environmental contexts, to shape the evolution of social structure. My research program has found that both direct and indirect genetic effects shape the structure of social networks of flies, and selection on social structure varies depending on both the social- and physical-environmental contexts social groups experience. More specifically, individuals’ social network positions are heritable, and also shaped by the genotypes of social groupmates. The strength and direction of selection on individuals’ network positions depends on both the nutritional environment, as well as the genotypic composition of social groupmates. These findings suggest that genetic variation in social structure is pervasive, and can be adaptively maintained due to context-dependent selection operating on social group structure.application/pdfengCopyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.social group structurequantitative geneticssocial networksnutritionindirect genetic effectssocial selectionsocial evolutionDrosophila melanogasterThesis2021-09-02