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Flowers selectively deter insects: acacia


Sweet acacia / Mike / LicenseGFDL - Gnu Free Document License

Flowers of some acacia plants attract pollinators while deterring protective symbiotic ants through the use of volatile organic compounds.


Acacia and ant mutualism. On left, flowers produce chemicals that deter ants. On right, as pollen gets brushed off by pollinators, flowers become less repellant and ants come onto the flowers and protect the seeds (for more information, see Gill 2009). Artist: Emily Harrington. Copyright: All rights reserved. See gallery for details.

"1. Ants show complex interactions with plants, both facultative and mutualistic, ranging from grazers through seed predators and dispersers to herders of some herbivores and guards against others. But ants are rarely pollinators, and their visits to flowers may be detrimental to plant fitness.

"2. Plants therefore have various strategies to control ant distributions, and restrict them to foliage rather than flowers. These 'filters' may involve physical barriers on or around flowers, or 'decoys and bribes' sited on the foliage (usually extrafloral nectaries - EFNs). Alternatively, volatile organic compounds (VOCs) are used as signals to control ant behaviour, attracting ants to leaves and ⁄ or deterring them from functional flowers. Some of the past evidence that flowers repel ants by VOCs has been equivocal and we describe the shortcomings of some experimental approaches, which involve behavioural tests in artificial conditions.

"3. We review our previous study of myrmecophytic acacias, which used in situ experiments to show that volatiles derived from pollen can specifically and transiently deter ants during dehiscence, the effects being stronger in ant-guarded species and more effective on resident ants, both in African and Neotropical species. In these plants, repellence involves at least some volatiles that are known components of ant alarm pheromones, but are not repellent to beneficial bee visitors.

"4. We also present new evidence of ant repellence by VOCs in temperate flowers, which is usually pollen-based and active on common European ants. We use these data to indicate that across a wide range of plants there is an apparent trade-off in ant-controlling filter strategies between the use of defensive floral volatiles and the alternatives of decoying EFNs or physical barriers." (Willmer et al. 2009:888)
About the inspiring organism
Med_800pxacacia_farnesiana_az Vachellia

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Organism/taxonomy data provided by:
Species 2000 & ITIS Catalogue of Life: 2008 Annual Checklist

Bioinspired products and application ideas

Application Ideas: Attracting pollinators to crops while deterring other unwanted insects. Non-lethal ant or other insect pest control strategies.

Industrial Sector(s) interested in this strategy: Agriculture, pest control

School of Biological Sciences
Dr. Graham Stone
The University of Edinburgh
Willmer PG; Nuttman CV; Raine NE; Stone GN; Pattrick JG; Henson K; Stillman P; McIlroy L; Potts SG; Knudsen JT. 2009. Floral volatiles controlling ant behaviour. Functional Ecology. 23: 888–900.
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Gill V. 2009. Acacia plant controls ants with chemical. BBC News [Internet],
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