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Plant secondary metabolites in nectar: impacts on pollinators and ecological functions

Lookup NU author(s): Professor Geraldine Wright

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Abstract

© 2016 The Authors. Functional Ecology © 2016 British Ecological SocietyThe ecological function of secondary metabolites in plant defence against herbivores is well established, but their role in plant–pollinator interactions is less obvious. Nectar is the major reward for pollinators, so the occurrence of defence chemicals in the nectar of many species is unexpected. However, increasing evidence supports a variety of potential benefits for both plant and pollinator from these compounds. Beneficial effects may include: (i) mediating specialization in plant–pollinator interactions, (ii) protecting nectar from robbery or larceny and (iii) microbial activity including preservation of nutrients in nectar from degradation and reduction in disease levels in pollinators. Secondary metabolites in nectar can be toxic or repellent to flower visitors, but equally they can go undetected or even make nectar more apparent or attractive. These biological effects are concentration dependent, so must be considered at a range of ecologically relevant doses. For example, caffeine occurs in nectar and improves honeybee memory for odours associated with food rewards, which enhances pollen transfer at naturally occurring concentrations but is repellent to honeybees at higher concentrations. This review synthesizes evidence from recent literature that supports selection for secondary metabolites in floral nectar as an adaptation that drives the co-evolution between plants and their pollinators. However, their presence in nectar could still simply be a consequence of their defensive role elsewhere in the plant (pleiotropy). We highlight the need for more studies demonstrating measurable benefits to the plant, the importance of exposure levels and effects on target species beyond the current emphasis on alkaloids and bees. A Lay Summary is available for this article.


Publication metadata

Author(s): Stevenson PC, Nicolson SW, Wright GA

Publication type: Article

Publication status: Published

Journal: Functional Ecology

Year: 2017

Volume: 31

Issue: 1

Pages: 65-75

Print publication date: 01/01/2017

Online publication date: 07/09/2016

Acceptance date: 28/07/2016

Date deposited: 16/08/2017

ISSN (print): 0269-8463

ISSN (electronic): 1365-2435

Publisher: Wiley-Blackwell

URL: https://doi.org/10.1111/1365-2435.12761

DOI: 10.1111/1365-2435.12761


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