A major area of investigation in evolutionary biology is the evolution of complex traits. The number of states, the order in which they arise, and the number of times a trait has evolved interest evolutionary biologists. Such studies are only made possible by reconstructing phylogenies in the context of the taxa. Biological investigations rely on accurate species designations and delimitations, and lack of well-defined taxonomic groups impedes scientific progress. Pompilidae (Insecta: Hymenoptera), popularly known as spider wasps, are predatory insects that provision their offspring with spiders as the sole food source. Adult female wasps attack spiders and paralyze them with venom, then place them in simple nests that are usually dug in the soil. Spider wasps form a large and cosmopolitan family with nearly 5,000 described species. Although all Pompilidae have similar biology, there is considerable variation in the nest construction and provisioning behavior; thus, this family could be useful for understanding the evolution of complex behavior. My study aims to evaluate and solve several taxonomic conflicts in spider wasps by reconstructing the complex evolution of behavioral patterns using a molecular phylogenetic framework. Early stages of sociality are found in spider wasps, such as communalism (females of same generation nesting together). My ultimate goal was to study the evolution of communalism in these wasps. I reconstructed relationships at the subfamily and tribal levels for the family, as well as generic and specific levels for pre-defined lineages using five nuclear markers (28S, EF, Pol2, LWRh, Wg), one mitochondrial marker (COI), and morphological characters. These studies comprise the first attempt to revise generic, tribal, and species delimitations for spider wasps, based on robust molecular evolutionary trees. Finally, by studying early stages of social evolution, my results will provide for a better understanding the evolution of social behavior in Hymenoptera as a whole.

Increasingly, individual variation is being recognized as an important influence on behavioral evolution. Sources of variation are therefore an important target for research into the development, evolution, and function of behavior. By providing information about the timescale on which individuals are responsive to their environment, patterns of within-individual variation can shed light on function of behavioral variation. Here, I wanted to understand the function of behavioral variation and the genetic and environmental sources of variation in behavior. First, I test the hypotheses that variation in begging signals nestling hunger, need, or quality. Hunger is a short-term response to food deprivation, while need and quality give long-term information about fitness benefits of gaining more food and fitness potential, respectively. Second, I test the hypotheses that variation in begging is due to genetic, permanent environment, common environmental, and maternal effects. I test these hypotheses in the begging behavior of western bluebirds (Sialia mexicana), making repeated measurements across the nestling period. I show that begging behavior is consistent across the nestling period, and that nestling begging intensity increases with food deprivation. Nestlings fed during a given parental visit beg at higher intensity than nestmates, and on average wait longer since their last meal compared to individuals who were not fed in the same visit. These results support the hypothesis that variation in nestling begging signals hunger. I also show that responsiveness to food deprivation is negatively related to condition, but this effect is not consistent across the nestling period. Finally, variation in begging is produced by a common environmental effect that is correlated through time, suggesting that begging is strongly influenced by the nest environment. Together, these results indicate that variation in begging signals short-term changes in hunger and that environmental effects dominate the production of variation in begging.