How a generalist bee achieves high efficiency of pollen collection on diverse floral resources

Avery L. Russell, Stephen L. Buchmann, Daniel R. Papaj

Research output: Contribution to journalArticlepeer-review

Abstract

Bees foraging for floral rewards are one of our most thoroughly studied examples of generalist foraging ecology. Generalist bees rely considerably on instrumental (associative) learning to acquire routines that allow them to collect nectar efficiently from diverse plant species. Although such bees must also collect pollen from diverse species, few studies have examined if and how high efficiency is achieved. We characterized how generalist bumble bees (Bombus impatiens) foraged effectively for pollen from diverse floral resources, by manipulating the presence of pollen and anther cues, in a series of experiments using pollen-bearing live flowers, flowers of a sterile pollenless horticultural hybrid, and artificial flowers. We show that generalist bumble bees exhibit flexible and effective pollen collection by switching between 2 routines: "scrabbling"when pollen is abundant and "sonicating"when pollen is scarce. Efficient switching between these behaviors is regulated by the interplay of 2 ubiquitous floral cues: chemical anther cues stimulating pollen collection behavior and mechanical pollen cues suppressing sonication (and eliciting scrabbling). Flexible pollen collection behavior is functional: When pollen on anthers was scarce, bees collected it at a greater rate by sonicating than scrabbling. This mechanism of behavioral flexibility likely allows generalist bees to handle diverse anther morphologies efficiently and may have facilitated the recurrent evolution of plant species that conceal pollen rewards via pored floral morphology. Whereas effective nectar foraging relies heavily on associative learning of unique routines for each flower type, a weighing of 2 types of cues regulates the flexible pollen collection mechanism we describe.

Original languageEnglish (US)
Pages (from-to)991-1003
Number of pages13
JournalBehavioral Ecology
Volume28
Issue number4
DOIs
StatePublished - Jul 1 2017

Keywords

  • behavioral flexibility
  • floral evolution
  • floral sonication
  • learning
  • pollen foraging
  • specialization

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Animal Science and Zoology

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