Spatial structuring and floral avoidance behavior prevent ant-pollinator conflict in a Mexican ant-acacia

N E Raine, P Willmer, G N Stone

Research output: Contribution to journalArticlepeer-review


Ant-acacias represent a classic insect-plant mutualism: the ants defend the plant from attack by herbivores, and in return are provided with trophic rewards and living space within swollen thorns. A potential drawback of this and other ant-plant mutualisms is that ant-guards may drive away useful insects, particularly pollinators. We assess the potential for ant-pollinator conflict in a Mexican ant-acacia, Acacia hindsii. This Acacia is guarded by a highly aggressive ant (Pseudomyrmex veneficus), which resides entirely within the host plant canopy and is provided with extrafloral nectar and protein-rich Beltian bodies. Acacia hindsii flowers released their pollen from 0700 to 0830 hours, and were visited by pollinators from 0730 to 1300 hours. Over the same time period ants maintained high activity levels at extrafloral nectaries on young leaves. Although daily activity of ants and pollinators overlapped substantially in time, it was largely separated in space: resources exploited by the ants are predominantly concentrated within new growth, while inflorescences are present only on shoots from the previous year. Ants nevertheless visit extrafloral nectaries on older, leaves near inflorescences, and there is thus potential for ant-pollinator conflict. Bioassays of ant behavior showed young A. hindsii inflorescences induce an avoidance response in its ant-guards, which reinforces spatial segregation between ants and pollinators. This effect,is absent from buds or postreproductive flowers. Young flowers of two non-myrmecophilous Acacia species also induced significant (though less potent) repellent effects, suggesting a general role for ant-repellents in Acacia, with selective enhancement in myrmecophilous species.

Original languageEnglish
Pages (from-to)3086-3096
Number of pages11
JournalLandscape ecology
Issue number11
Publication statusPublished - Nov 2002


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