The behavioural ecology of the brain: integrating evolution, behaviour and neuroscience.

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The brain differs greatly in size and shape across vertebrate species, but how and why this anatomical diversity exists is largely unknown. My research program addresses this fundamental issue in neuroscience through understanding how brain and behaviour evolve in concert. More specifically, I test the validity of evolutionary theories as applied to the brain through studies within and across species and using a range of neuroscience, animal behaviour and evolutionary biology techniques. In this grant cycle, I will focus on two aspects of reproductive behaviour that are related to how the brain evolves: courtship display and mating system. Courtship is an essential part of reproduction and, in birds, the evolution of different courtship displays is associated with anatomical changes in the brain. However, the majority of studies on the neural basis of avian courtship displays focus on vocalizations and very little is known about how the brain produces and modulates non-vocal courtship displays. I will address this knowledge gap by examining the ruffed grouse (Bonasa umbellus), a species that does not vocalize in its courtship. Instead, male grouse produce a low frequency drumming display. Through a series of field experiments, my lab will determine how grouse generate the low frequency sound characteristic of this display and identify the neural circuitry required to produce the display. Mating systems also play a significant role in how the brain evolves. Our understanding of how mating system is related to brain anatomy and evolution is, however, based on two-species comparisons in which one species is asocial and polygamous whereas the other is social and monogamous. These comparisons are inherently confounded because it is unclear whether the differences are attributable to sociality or mating system. Determining whether brain region size or neurochemistry reflects mating systems or not therefore requires the analysis of species that vary in both sociality and mating system. My previous research showed that the social, polygamous Richardson’s ground squirrel (Urocitellus richardsonii) has markedly different seasonal and sex differences in hippocampal anatomy than other polygamous rodents. This suggests that sociality and other behaviours might play a significant role in how the hippocampus evolves. Here, I propose to build upon this initial work and quantify the sex and seasonal differences in greater anatomical detail and test for differences in spatial abilities in both wild and lab-reared ground squirrels. Mating system is, however, also related to neurochemistry, especially the distribution of neuropeptide receptors. I will also test if there are significant sex differences in the distribution of oxytocin and vasopressin receptors in Richardson’s ground squirrels. Finally, I will test whether sexual dimorphism in the hippocampus varies across mating systems by performing comparative tests across ground squirrels and grouse. Because sexual dimorphism in hippocampal anatomy is thought to reflect home range sizes and movement, I predict that asocial ground squirrels will have greater sexual dimorphism in the hippocampus than social species. Similarly, I expect that the polygamous ruffed grouse will have greater sexual dimorphism in the hippocampus than the monogamous ptarmigan (Lagopus spp.). Through this unique combination lab and fieldwork and studies within and across species, my research will greatly improve our understanding of brain-behaviour relationships and general principles of evolutionary neurobiology that will help to refine hypotheses about how the brain evolves.