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Dryad

The evolution of broadly polylectic behaviour in Lasioglossum (Chilalictus) (Halictidae, Apoidea)

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Dec 09, 2019 version files 75.25 KB

Abstract

Based on the number of pollen hosts utilised, bees have been categorised as generalists (polylectic) or specialists (oligolectic). Faced with a changing habitat, polylectic bees can diversify their pollen ‘portfolio’, while oligolectic bees cannot and therefore may go locally extinct. Research into the evolution and maintenance of broad polylecty is scant. Instead, research has mainly focussed on the factors that constrain oligolectic species to a narrow diet. Here, we developed a molecular phylogeny of a native Australian subgenus Lasioglossum (Chilalictus), (Halictidae), to study the evolution of pollen host breadth within the group. We find that broad polylecty has evolved independently at least four times in L. (Chilalictus) and did not result in subsequent speciation. Oligolecty has evolved once and is found in at least three related species. In addition, broadly polylectic species have significantly larger areas of occurrence than oligolectic and polylectic species. Taken together, these results suggest that there is less opportunity for speciation in broadly polylectic than in polylectic and oligolectic species. As broad polylecty is uncommon in bees, we hypothesise the existence of genetic constraints to its evolution. Future studies on the evolution of broad polylecty should examine both the existence of constraints and selective advantages for host broadening in polylectic species.