Evolution of neuroendocrine mechanisms regulating adaptive behavior
O'Connell, Ashley Lauren
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All animals must integrate internal and environmental information into an appropriate behavior that ultimately aims to increases fitness. In order to investigate the proximate and ultimate mechanisms underlying adaptive behavior, I examined the role of neuroendocrine molecules at three distinct levels of biological organization. At the level of the individual, I demonstrate that steroid hormone receptors play distinct roles in modulating adaptive behavior, physiology and brain gene expression in dominant and subordinate African cichlid fish. At the level of the social community, I investigate how the behavior and physiology of one individual can affect the behavior, physiology, and brain gene expression of other community members. I found striking covariance patterns that implicate identifiable neuroendocrine pathways as mediators of specific social signals, establishing an important model to investigate the molecular basis of how behavioral phenotypes spread through communities. Finally, I investigate how the neurochemistry of the five major vertebrate classes has changed in a way that covaries with sensory integration, life history, and mating strategy. To address this question, I have laid an important theoretical framework to study the evolution of behavior as well as establishing neuroanatomical brain homologies across vertebrate lineages. I show that variation in where neurochemicals (dopamine, steroids, neuropeptides) are produced in the brain varies across vertebrates while where signals are received (ie receptors) are conserved, providing a novel theory of social brain evolution. In summary, I use a multidisciplinary approach to study hormonal contributions to the proximate and ultimate mechanisms of social behavior on many levels of biological organization and have contributed important novel insights that have significantly increased our understanding of the evolution of behavior and its neural and molecular underpinnings.