 Abstract | This thesis investigates the evolution and biogeographical history of the bee tribe Allodapini. Examinations of life history traits, nesting patterns, and morphology were the primary methods used to explore allodapine biology, whilst a molecular-based phylogenetic approach was used to explore patterns of speciation and diversification within the tribe. A primary feature of this research is the expansion and revision of the allodapine phylogeny, using DNA sequence techniques. The phylogenetic components of this thesis focus primarily on the earliest divergences and generic-level bifurcations within continentally and environmentally defined allodapine clades. These relationships were used to examine the nature of broader changes in sociality, nesting biology, morphology, and geographic distribution across the tribe as a whole.
Results indicate that the strong benefits social nesting affords in repelling enemies-at-the-nest is implicit in the universal retention of social behaviour within the Allodapini, and that this characteristic may also apply to other taxa that show a lack of reversions from social to solitary living. Results also suggest that some of the tribe's farthest-reaching radiations occurred rapidly and relatively early, with some of the foremost involving dispersal events that do not appear to fit with current palaeogeographical reconstructions. The infrequency of major transitions between different environmental biomes within the tribe is indicative of ecological constraints and niche conservatism that appears to have resulted in low adaptive radiation and diversification. These constraints appear ameliorated during periods of climatic and environmental instability; possibly by way of allopatric speciation promoted by habitat fragmentation. Allodapines play a fundamentally important role as pollinators within their ecosystems. As such, these findings highlight the impact that climatic and environmental change, as well as rare and poorly understood mechanisms of dispersal, can have on key components of a biome's constituent taxa and hence the course of an ecosystems future evolution.
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