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Do extrafloral nectaries distract ants from visiting flowers? An experimental test of an overlooked hypothesis

TitleDo extrafloral nectaries distract ants from visiting flowers? An experimental test of an overlooked hypothesis
Publication TypeJournal Article
Year of Publication2002
AuthorsWagner, D, Kay, A
JournalEvolutionary Ecology Research,
Pagination293–305
Abstract

When ants visit .owers, they can interfere with plant reproduction. Some plant species possess adaptations, such as specialized .oral morphologies, that reduce visitation by unproductive or injurious insects. Kerner (1878) hypothesized that extra.oral nectaries, by distracting ants from foraging at .oral nectaries, might also serve as an adaptation to reduce ant visitation to .owers. The viability of this hypothesis rests, in part, on ant foraging behaviour. When presented with extra nectar sources, do fewer ants visit each nectary or does recruitment keep visitation constant? Using arti.cial plants placed near free-living colonies of two ant species, we varied the presence, absence and quality of extra nectar sources and monitored visitation to primary, invariable nectar sources, representing .oral nectaries. Signi.cantly fewer ants of both species visited primary nectaries when extra nectar sources were present. Variation in the quality of the extra nectar sources had no signi.cant e.ect on the number of ants visiting primary nectaries, but did a.ect visitation to extra nectar sources by one of the two species. Workers of Forelius sp. 1 strongly preferred sugar solutions with amino acids over sugar solutions alone and signi .cantly greater numbers of Forelius workers visited arti.cial plants that provided amino acids than plants in other treatments. In contrast, workers of Formica perpilosa showed no signi.cant preference among nectar types and neither the presence nor the quality of extra.oral nectar signi.cantly a.ected numbers of ants on arti.cial plants. The results suggest that extra.oral nectaries could bene.t plants by reducing the number of ants visiting .owers.

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