The evolution of social behavior can affect brain size: social species of animals tend to have larger brains than their solitary relatives. The goal of this project is to further our understanding of how changes in species' social structure can affect the architecture of their brains. The research will use social insects - paper wasps - as subjects. All species of paper wasps are social, but they show a wide range of colony sizes, they are diverse in social complexity, and they differ in nest architecture. Different anatomical regions of the wasp brain serve distinct cognitive functions - some regions are dedicated to vision, others to smell and touch. The researchers will measure the sizes (volumes) of these brain regions as a way of estimating how much tissue is invested in each region, and they will test whether the details of a species' social behavior (for example, large versus small colonies) predict the relative size of each brain region. The researchers will use information on how wasp species are related to each other to trace the evolution of associations between brain structure and behavior. By comparing selected species of paper wasps with different behavioral characteristics, the researchers will determine which elements of social behavior have impacted the investment in each brain region. The project will also explore how evolutionary changes in the immature development of the wasp brain have led to the observed patterns of adult brain region investment. The research will further our understanding of how changes in social complexity can influence brain architecture, and the findings will indicate which social cognitive challenges can affect the amount of investment in different brain regions. It will also contribute to our understanding of how adult brain architecture is generated by the developmental processes that occur during immature stages. The project includes employment and training opportunities for graduate and undergraduate students at two universities, and it will foster collaboration across universities. It also involves both local elementary school and international outreach and education efforts.
This award funded research investigating how social behavior affects the structure and development of the nervous system. We used social wasps as a model system, as it is easy to collect large numbers of individuals for detailed analyses of brain structure throughout development. Wasps also exhibit a number of different types of social organization, in addition to different colony sizes, nest architectures and caste determination mechanisms. The social behaviors of different species can thus be associated with differences in brains structure and development. The manner in which differences in the nervous system support differences in behavior has been a long-standing question in the biological sciences, and is important for understanding how brains and behaviors have evolved together in animals, including humans. Obtaining a variety of wasps with different social behaviors is order to identify brain structural differences associated with behavior was a key component of the funded research. We (myself and co-PI Sean O'Donnell) organized field research in Costa Rica, where wasp species diversity is very high. These field expeditions provided valuable training for undergraduate and graduate students in a number of research areas. For example, students learned about the local ecosystem and insect behavior while tracking and collecting different wasp species. In my laboratory, students were trained in microdissection, tissue processing and staining of tissue for developmental studies. We have employed a number of labels for developing tissue, including antibodies that mark dividing stem cells in the brain. These markers allow stem cell numbers to be counted and compared across species at different stages in development. We also developed a method for improving the preservation of field-collected tissue sample, allowing them to be gathered at remote field sites such as in Costa Rica, and transferred to my laboratory in the US with minimal damage. This method will be helpful for future studies in which species of interest must be collected at distant field sites, but tissue processing and staining must be performed at the home institution. Results of the funded research have yet to be published, but over the course of the grant period, I have been able to publish a number of review articles meant for a more general scientific readership on the topic of brain and behavioral evolution. In particular, I have sought to develop and disseminate the idea that mechanisms of brain development and evolution are very similar in all animals. Thus, basic features of brain structure and function are likely to apply to all animals with central nervous systems, from insects to humans. This topic is of importance as it encourages more global thinking about the relationship between structure and function in the nervous system, and in particular the incorporation of studies from non-model system species into the increasingly model system dominated field of neuroscience.
