A project undertaken at Western Sydney University, and supervised by Dr Simon Tierney.
The hyperactivity of foraging bees is often associated with spring blossoms on bright sunny days. However, a diverse variety of bees exclusively forage between dusk and dawn under ‘dim-light’ conditions. These successful colonisations of a novel light environment and shifts in the timing of activity patterns provide intriguing examples of adaptive evolution and species radiation.
Nocturnal halictid bee visiting a Balsa flower in pre-dawn dim-light. Credit: Christian Ziegler
The availability of an empty niche in combination with key adaptations has likely triggered the repeated independent evolution of dim-light bees within at least 20 lineages (four of seven bee families), which this project sets out to explore from a comparative perspective. It is hypothesised that entry into very low-light environments enables bees to elude competitors, predators and parasites. Convergent traits relating to vision and flight are generally present among obligate dim-light species but are absent from facultative species – which suggests that the diurnal to nocturnal transition is behaviourally driven and may represent an example of niche construction as an evolutionary process.
Species from the family Halictidae (Apoidea: Anthophila) exhibit the most notable and prevalent radiations of dim-light foraging among all bees. Two independently evolved lineages have arisen in parallel (different subfamilies in discrete biogeographic regions) and display a suite of convergent morphologies. Indeed, they are so similar in physical appearance that the type specimen for one genus was taxonomically misdiagnosed as belonging to the alternate subfamily. This is impressive considering these two lineages are estimated to have diverged from each other in the early Palaeogene ~ 40-65 million years ago.
The biology of the Australasian nocturnal lineage is effectively unknown – evolutionary origins and relationships to their closest day-flying relatives are unresolved and knowledge of their natural history and pollination ecology is very limited. This project will provide the first integrative assessment of nocturnal bee diversity in the South West Pacific region by assimilating diverse data sets (phylogenomic systematics, morphology, behaviour, plant visitation) to provide a comparative assessment of the factors driving adaptive evolution in novel dim-light sensory environments.