Flowers help bees cope with uncertainty: Signal detection and the function of floral complexity

Anne S. Leonard, Anna Dornhaus, Daniel R. Papaj

Research output: Contribution to journalArticlepeer-review

123 Scopus citations


Plants often attract pollinators with floral displays composed of visual, olfactory, tactile and gustatory stimuli. Since pollinators' responses to each of these stimuli are usually studied independently, the question of why plants produce multi-component floral displays remains relatively unexplored. Here we used signal detection theory to test the hypothesis that complex displays reduce a pollinator's uncertainty about the floral signal. Specifically, we asked whether one component of the floral display, scent, improved a bee's certainty about the value of another component, color hue. We first trained two groups of bumble bees (Bombus impatiens Cresson) to discriminate between rewarding and unrewarding artificial flowers of slightly different hues in the presence vsabsence of scent. In a test phase, we presented these bees with a gradient of floral hues and assessed their ability to identify the hue rewarded during training. We interpreted the extent to which bees' preferences were biased away from the unrewarding hue ('peak shift') as an indicator of uncertainty in color discrimination. Our data show that the presence of an olfactory signal reduces uncertainty regarding color: not only was color learning facilitated on scented flowers but also bees showed a lower amount of peak shift in the presence of scent. We explore potential mechanisms by which scent might reduce uncertainty about color, and discuss the broader significance of our results for our understanding of signal evolution.

Original languageEnglish (US)
Pages (from-to)113-121
Number of pages9
JournalJournal of Experimental Biology
Issue number1
StatePublished - Jan 2011


  • Bombus impatiens
  • Color learning
  • Complex signals
  • Foraging
  • Mimicry
  • Multimodal
  • Peak shift
  • Plant-pollinator interactions
  • Signal detection theory
  • Signal evolution

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Physiology
  • Aquatic Science
  • Animal Science and Zoology
  • Molecular Biology
  • Insect Science


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