Indirect effects of mutualism: ant-treehopper associations deter pollinators and reduce reproduction in a tropical shrub

Author(s)

Ibarra-Isassi, Javier ^{[1, 2]} ; Oliveira, Paulo S. ^[1]

Affiliation

^[1] Univ Estadual Campinas, Dept Biol Anim, BR-13083862 Campinas, SP - Brazil

^[2] Concordia Univ, Dept Biol, Montreal, PQ H4B 1R6 - Canada

• Document type: Journal article
• Source: Oecologia; v. 186, n. 3, p. 691-701, MAR 2018.
• Web of Science Citations: 3

Abstract

Animal-pollinated plants can be susceptible to changes in pollinator availability. Honeydew-producing treehoppers frequently occur on inflorescences, potentially enhancing ant-mediated negative effects on pollination services. However, the effect of ant-attended, honeydew-producing insects on plant reproduction remains uncertain. We recorded the abundance of treehoppers and ants on Byrsonima intermedia (Malpighiaceae), and monitored floral visitors in a Brazilian cerrado savanna. We manipulated the presence of ants and ant-treehopper associations on inflorescences to assess their effect on pollination and fruit formation. We used dried ants pinned to inflorescences to evaluate the effect of ant presence and ant identity on potential pollinators. Results show that the presence of treehoppers increases ant abundance on flowers and disrupts pollination by oil-collecting bees, decreasing the frequency and duration of floral visits and reducing fruit and seed set. Treehopper herbivory has no direct effect on fruit or seed production, which are independent of treehopper density. Pinned ants promote avoidance by floral visitors, reducing the number of visits. Ant identity mediates visitation decisions, with Ectatomma brunneum causing greater avoidance by floral visitors than Camponotus rufipes. Field videos show that pollinating bees are harassed by ants near flowers, prompting avoidance behavior by the bees. This is the first demonstration of indirect effects by honeydew-gathering ants, via disrupted pollination, on plant reproduction in tropical cerrado savanna. Our results highlight the importance of studying other interactions near flowers, in addition to just observing pollinators, for a proper understanding of plant reproduction. (AU)

• FAPESP's process: 14/12486-8 - Interactions between ants, flowers and flower visitors in cerrado vegetation: case study with Byrsonima intermedia A. Juss. (Malpighiaceae)
• Grantee: Javier Eduardo Ibarra Isassi
• Support Opportunities: Scholarships in Brazil - Master
• FAPESP's process: 14/23141-1 - Ecology of interactions, behavioral ecology, and genetics of neotropical ant populations
• Grantee: Paulo Sergio Moreira Carvalho de Oliveira
• Support Opportunities: BIOTA-FAPESP Program - Regular Research Grants