Floral traits mediate the pollination role of bees

Pollen-collecting bees are the most important pollinators globally, but are also the most common pollen thieves and can significantly reduce plant reproduction. Hargreaves et al. investigate whether floral characteristics mediate the roles played by bees – ranging from avid pollen thieves to the plant’s only pollinators – for ten species of Aloe. Pollen theft is promoted by nectar inaccessibility and strong dichogamy, which discourages visits to female-phase flowers. Furthermore, displays of many flowers facilitate deposition of mostly incompatible self-pollen. Thus species-specific floral and inflorescence characteristics govern the efficiency of pollen-collecting bees as pollinators of aloes.