THE EVOLUTION OF BROOD PARASITISM IN BEES AND OTHER ANIMALS

138 pagesSupplemental file(s) description: Chapter 2 Supplementary Figures, Chapter 2 Supplementary Tables, Chapter 1 Supplementary Tables.Parasitism is one of the most widespread strategies among animals, with up to half of all species and hundreds of independent groups exploiting host species in some way. Brood parasitism in particular is unique among other forms of parasitism for its exploitation of the parental care behaviors of host species, though it has been poorly studied in many respects. In my first chapter, I used literature searches to conduct a review of taxa exhibiting brood parasitism across the animal tree of life and investigated the macroevolutionary patterns shared among these diverse organisms. This research ultimately resulted in the identification of nearly 60 independent origins of brood parasitism, as well as some evidence for reduced diversification in such species compared to their non-parasitic sister groups, though differing evolutionary backgrounds also impact this pattern. My second chapter investigated the evolutionary relationships and history of the largest and oldest clade of brood parasitic bees, the subfamily Nomadinae. Ancestral reconstructions of host-parasite associations and parasitic strategies indicate that the early ancestors of this group were used closely related bees as hosts, but that later behavioral innovations likely facilitated the expansion of their host range by allowing the exploitation of a wider variety of distantly related species. Finally, the third chapter of my dissertation focused on the evolutionary signatures of brood parasitism detectable within the genome of a single bee species, Holcopasites calliopsidis. In agreement with previous findings on the genomic evolution of other parasitic organisms, this species shows reduced genome size compared to non-parasitic relatives, but no net loss of either repetitive or genic content. The genome assembly also shows signatures of dynamic evolution in comparison with other bee species, including the inferred presence of novel and rapidly evolving transposable elements