Browsing by Author "Saltz, Julia B."
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Item Anticipated effects of abiotic environmental change on intraspecific social interactions(Wiley, 2021) Fisher, David N.; Kilgour, R. Julia; Siracusa, Erin R.; Foote, Jennifer R.; Hobson, Elizabeth A.; Montiglio, Pierre-Olivier; Saltz, Julia B.; Wey, Tina W.; Wice, Eric W.Social interactions are ubiquitous across the animal kingdom. A variety of ecological and evolutionary processes are dependent on social interactions, such as movement, disease spread, information transmission, and density-dependent reproduction and survival. Social interactions, like any behaviour, are context dependent, varying with environmental conditions. Currently, environments are changing rapidly across multiple dimensions, becoming warmer and more variable, while habitats are increasingly fragmented and contaminated with pollutants. Social interactions are expected to change in response to these stressors and to continue to change into the future. However, a comprehensive understanding of the form and magnitude of the effects of these environmental changes on social interactions is currently lacking. Focusing on four major forms of rapid environmental change currently occurring, we review how these changing environmental gradients are expected to have immediate effects on social interactions such as communication, agonistic behaviours, and group formation, which will thereby induce changes in social organisation including mating systems, dominance hierarchies, and collective behaviour. Our review covers intraspecific variation in social interactions across environments, including studies in both the wild and in laboratory settings, and across a range of taxa. The expected responses of social behaviour to environmental change are diverse, but we identify several general themes. First, very dry, variable, fragmented, or polluted environments are likely to destabilise existing social systems. This occurs as these conditions limit the energy available for complex social interactions and affect dissimilar phenotypes differently. Second, a given environmental change can lead to opposite responses in social behaviour, and the direction of the response often hinges on the natural history of the organism in question. Third, our review highlights the fact that changes in environmental factors are not occurring in isolation: multiple factors are changing simultaneously, which may have antagonistic or synergistic effects, and more work should be done to understand these combined effects. We close by identifying methodological and analytical techniques that might help to study the response of social interactions to changing environments, highlight consistent patterns among taxa, and predict subsequent evolutionary change. We expect that the changes in social interactions that we document here will have consequences for individuals, groups, and for the ecology and evolution of populations, and therefore warrant a central place in the study of animal populations, particularly in an era of rapid environmental change.Item Quantitative Genetics and Evolutionary Consequences of Variation in Social Group Structure(2021-08-11) Wice, Eric Wesley; Saltz, Julia B.The 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.Item Understanding How Divergence in Diet Breadth and the Degree of Environmental Variability Contribute to Individual Differences in Decision-Making and Learning(2021-12-03) Burns, Madeline; Saltz, Julia B.The broad focus of my dissertation has been investigating the various selection pressures contributing to the variation we observe in animal cognition, and how that variation evolves. Thus far, my work has primarily investigated how divergence in habitat breadth contributes to variation in decision-making and learning; more specifically, how environmental variability influences the evolution of these cognitive abilities. Highly variable environments are predicted to favor higher decision-making and learning abilities (because those are the environments where they are hypothesized to be the most adaptive), while uniform environments are predicted to favor more “hardwired” or “rules of thumb” based approaches. To investigate this, we are comparing two closely-related species of fruit flies that recently diverged in diet breadth (and thus have been under divergent selection for the degree of environmental variability experienced in nature), Drosophila simulans and Drosophila sechellia. Divergence in habitat breadth and the degree of environmental variability experienced in nature are predicted to influence the evolution of general cognitive abilities (i.e., whether you have the general ability to make decisions and learn). However, due to divergent evolutionary histories, not all stimuli in the environment have equal consequences for everyone. So, when animals begin to diverge in cognition, does this divergence generalize across a broad range of cognitive abilities, stimuli, and contexts? Or is divergence in cognition limited to certain cognitive abilities, stimuli, or contexts? The central focus of my work has been understanding how selection pressures influence the evolution of cognition to produce variation on cognitive outcomes, and whether that divergence generalizes across cognitive abilities and stimuli, or is limited to certain cognitive abilities and contexts.