Abstract
Plant associations with protective ants are widespread among angiosperms, but carry the risk that ants will deter pollinators as well as herbivores. Such conflict, and adaptations to ameliorate or prevent the conflict, have been documented in African and neotropical acacias. Ant–acacia associations occur in Australia, but little is known of their ecology. Moreover, recent phylogenetic evidence indicates that Australian acacias are only distantly related to African and American acacias, providing an intercontinental natural experiment in the management of ant–pollinator conflict. We examined four populations of Acacia myrtifolia over a 400-km environmental gradient in southeastern Australia using ant and pollinator exclusion as well as direct observation of ants and pollinators to assess the potential for ant–pollinator conflict to affect seed set. Native bees were the only group of floral visitors whose visitation rates were a significant predictor of fruiting success, although beetles and wasps may play an important role as “insurance” pollinators. We found no increase in pollinator visitation or fruiting success following ant exclusion, even with large sample sizes and effective exclusion. Because ants are facultative visitors to A. myrtifolia plants, their presence may be insufficient to interfere greatly with floral visitors. It is also likely that the morphological location of extrafloral nectaries tends to draw ants away from reproductive parts, although we commonly observed ants on inflorescences, so the spatial separation is not strict. A. myrtifolia appears to maintain a generalized mutualism over a wide geographic range without the need for elaborate adaptations to resolve ant–pollinator conflict.
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Acknowledgments
We thank the Department of Sustainability and Environment of Victoria for permission to conduct the research (permit#10005111), and Parks Victoria, especially the rangers, for their kind support at the individual parks. We also thank Ken Walker for the identification of flower visitors, Simon Hinkley for ant identification corroboration, Alejandra Morán Ordóñez for the sites map, and the anonymous reviewers and the handling editor, Martin Heil, for their valuable comments and suggestions. AMB was supported by a Postgraduate Scholarship from CONACyT (Consejo Nacional de Ciencia y Tecnología, México), SEP (Secretaría de Educación Pública, México) and a Dean’s Scholarship from the Monash University Faculty of Science. MB was supported by the National Evolutionary Synthesis Center, Durham, North Carolina, during the preparation of the manuscript.
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Martínez-Bauer, A.E., Martínez, G.C., Murphy, D.J. et al. Multitasking in a plant–ant interaction: how does Acacia myrtifolia manage both ants and pollinators?. Oecologia 178, 461–471 (2015). https://doi.org/10.1007/s00442-014-3215-0
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DOI: https://doi.org/10.1007/s00442-014-3215-0