Evolutionary Ecology

, Volume 29, Issue 3, pp 405–417

Nectar palatability can selectively filter bird and insect visitors to coral tree flowers

  • Susan W. Nicolson
  • Sara Lerch-Henning
  • Megan Welsford
  • Steven D. Johnson
Original Paper

Abstract

Secondary compounds in nectar may play a decisive role in determining the spectrum of floral visitors on plants. Flowers of the African coral tree Erythrina caffra are visited mainly by generalist passerine nectarivores, such as weavers and bulbuls. As the nectar of this species tastes very bitter to humans, it was hypothesized that secondary compounds may repel sunbirds and honeybees which are common in the same habitats yet seldom consume the nectar. We conducted choice tests using fresh nectar and both sucrose and hexose (glucose/fructose) solutions of the same concentration as the nectar. White-bellied Sunbirds (Cinnyris talatala) were repelled by nectar of both E. caffra and a related species Erythrina lysistemon, but Dark-capped Bulbuls (Pycnonotus tricolor) did not discriminate between the Erythrina nectar and control sugar solution in terms of amounts consumed. Honeybees (Apis mellifera scutellata) probed exposed droplets of E. caffra nectar and a control sugar solution at the same rate, suggesting that there is no volatile deterrent, but they immediately withdrew their proboscis far more often from the droplets of Erythrina nectar than they did from the sugar solution, suggesting that they find Erythrina nectar distasteful. These results contribute to a growing awareness that non-sugar components of nectar can play important functional roles in plant pollination systems.

Keywords

Bird pollination Bitter nectar Dilute nectar Erythrina Generalist nectarivores 

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Copyright information

© Springer International Publishing Switzerland 2014

Authors and Affiliations

  • Susan W. Nicolson
    • 1
  • Sara Lerch-Henning
    • 1
  • Megan Welsford
    • 2
  • Steven D. Johnson
    • 2
  1. 1.Department of Zoology and EntomologyUniversity of PretoriaHatfieldSouth Africa
  2. 2.School of Life SciencesUniversity of KwaZulu NatalScottsville, PietermaritzburgSouth Africa

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