Halictine bees of the south west Pacific: implications of a recent and rapid radiation

The halictine (Hymenoptera: Halictinae) bees of the south western Pacific islands represent a model system for understanding a recent and rapid radiation. The region consists of biodiverse island groups of varying geological age and elements, with an eastward progression of increasing isolation. The sub-genus Homalictus, of presumed Australian origin, exhibits a large proportion of the known bee diversity with a high degree of endemism and a number of putative cleptoparasitic species. These small, metallic, ground-nesting bees have a demonstrated ability to disperse, colonise and speciate over relatively large oceanic barriers. However, large intra-species morphological variation and small inter-species characteristics limit their identification based on morphology alone. The true bee diversity of the region may, therefore, differ dramatically from current understanding. The SWP relies on pollination economically through export of fruit and vegetable products, but also for the diet for a large proportion of subsistent communities. As these critical pollinators face increasing pressure from agricultural intensification and impacts of invasive species, effective population conservation and management relies on understanding the true species diversity. DNA barcoding has provided an ideal tool to not only resolve taxonomic uncertainty, but to reveal potential cryptic species too. Here we discuss the capabilities of this technology in understanding the true diversity and evolution of a recent bee fauna, and how this might impact future agricultural practices.