Concealed floral rewards and the role of experience in floral sonication by bees

• Published in: Animal behaviour 2016-10, Vol.120, p.83-91
• Main Authors: Russell, Avery L., Leonard, Anne S., Gillette, Heather D., Papaj, Daniel R.
• Format: Article
• Language: English
• Subjects: Animal behavior; Animal cognition; Animal memory; Bees; Bombus impatiens; bumblebee; buzz pollination; concealed reward; experience; floral reward; floral sonication; Foraging behavior; learning; mutualism; Plant reproduction; Pollen; pollen collection
• ISSN: 0003-3472; 1095-8282
• DOI: 10.1016/j.anbehav.2016.07.024

Pollinators frequently use complex motor routines to find and extract floral rewards. Studies of pollinators foraging for nectar rewards indicate these routines are typically learned, and that constraints associated with learning and memory give pollinators incentive to continue foraging on these flowers. However, plants offer rewards besides nectar, including pollen, lipids and essential oils. In particular, bees use a complex motor routine termed floral sonication to extract pollen, their primary source of protein, from the more than 6% of flowering plant species (>22 000 species) that conceal pollen rewards within tube-like poricidal anthers. If floral sonication requires learning, this pollen extraction behaviour could contribute to floral fidelity. However, no studies have quantified the effect of experience on flower handling for bees extracting pollen from poricidal species. We therefore examined the degree to which floral sonication behaviour was modified by experience. We found that the key elements of the sonication motor routine appeared in full-blown form in a flower-naïve bee's first visit to a flower. We additionally found consistent, albeit modest, effects of experience on certain aspects of sonication behaviour. The latency to sonicate slightly decreased with experience. Bees also adjusted the length and amplitude of their sonication buzzes in response to pollen receipt. We conclude that the role of experience in foraging for concealed pollen rewards is different from that reported for nectar rewards. We offer an alternative explanation for its function in sonication. Finally, we discuss alternative hypotheses for the function of poricidal anthers and for how pollen-bearing plants may ensure floral fidelity even in the absence of a significant impact of experience on pollen extraction behaviour. •Bees successfully extracted concealed pollen on their first floral visit.•Bees showed a small but rapid decrease in latency to sonicate after landing.•Change in flower handling time did not persist or depend on pollen receipt.•Bees modified features of sonication buzzes in response to pollen receipt.•Pollen concealment likely does not drive floral fidelity via cognitive constraints.