Honesty of Signaling and Pollinator Attraction: The Case of Flag-Like Bracts
AbstractBracts are nonfloral showy structures associated with inflorescences. They are generally hypothesized to enhance plant reproductive success by attracting pollinating insects. We investigated whether flag-like bracts at the top of inflorescences reliably signal of floral food reward for pollinators in Salvia viridis L. Field and greenhouse data indicate incomplete synchrony between the development of flowers and bracts. Various measures of bract size, however, positively correlate with the number of open flowers on the inflorescence, and with their nectar rewards. Experimental removal of bracts from inflorescences significantly reduced honeybee visitation in the field. We compared these findings with field data on Lavandula stoechas L., another labiate species with flag-like displays. The number of open flowers in L. stoechas cannot be reliably predicted from the presence or size of the bracts. Bract clipping does not significantly reduce honeybee visits in this species. We conjecture that bees learn to orient to those bracts that reliably signal food rewards, and disregard bracts if they provide unreliable signals. Asynchronous development of bracts and floral rewards can reduce the reliability of the signals, and may explain the rarity of flag-like displays in pollination systems. We discuss additional selective forces that may favor bract displays.
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Bibliographic InfoPaper provided by The Center for the Study of Rationality, Hebrew University, Jerusalem in its series Discussion Paper Series with number dp438.
Length: 32 pages
Date of creation: Dec 2006
Date of revision:
Flag-Like Bract; Extra-Floral Display; Pollination Ecology; Signaling; Honeybee; Phenology; Lavandula; Salvia;
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- Tamar Keasar & Adi Sadeh & Avi Shmida, 2007. "The Signaling Function of an Extra-floral Display: What Selects for Signal Development?," Discussion Paper Series dp468, The Center for the Study of Rationality, Hebrew University, Jerusalem.
- Rachel Arnon & Tamar Keasar & Dan Cohen & Avi Shmida, 2006. "Vertical Orientation and Color Contrast and Choices by Bumblebees (Bombus terrestris L.)," Levine's Bibliography 321307000000000608, UCLA Department of Economics.
- Rachel Arnon & Tamar Keasar & Dan Cohen & Avi Shmida, 2006. "Vertical Orientation and Color Contrast and Choices by Bumblebees (Bombus terrestris L.)," Discussion Paper Series dp439, The Center for the Study of Rationality, Hebrew University, Jerusalem.
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