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The effects of flower, floral display, and reward sizes on bumblebee foraging behavior when pollen is the reward and plants are dichogamous
- Johanne Brunet, Magaret W. Thairu, Jillian M. Henss, Rosabeth I. Link, Joshua A. Kluever
- International journal of plant sciences 2015 v.176 no.9 pp. 811-819
- Aquilegia coerulea, Bombus, dichogamy, flowers, foraging, inbreeding depression, pollen, pollinators, population
- Insect-pollinated plants have developed showy flowers and floral displays that attract pollinators. Pollinators, in turn, show preferences for specific floral traits and their foraging behavior is influenced by floral traits. In this study, we examined the preference of bumble bees for flower size, spur length, pollen reward and floral display size in the Rocky Mountain columbine, Aquilegia coerulea. Dual choice assays were used to examine the preference of bumble bees for flower size, spur length and pollen reward while experimental arrays helped determine the preference of bees for floral display size and the proportion of flowers visited per inflorescence. Bumble bees preferred larger floral displays and visited a smaller proportion of the flowers on larger inflorescences. Variation in pollen reward among flowers did not explain the smaller proportion of flowers visited on larger inflorescences. Bumble bees did not show a preference for larger flowers, greater pollen reward or shorter or longer spurs. In A. coerulea, floral display size played a major role in attracting bumble bees. We therefore expect bumble bees to select for larger floral displays which will increase geitonogamy levels. Since A. coerulea suffers from strong inbreeding depression, there will be a balance between the increase in floral display resulting from pollinator attraction and the decrease resulting from increased geitonogamy levels. In addition, the lack of potential selection by bumble bees on flower size and spur length could help maintain the variation in these floral traits in A. coerulea populations.