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Density-mediated, context-dependent consumer-resource interactions between ants and extrafloral nectar plants.
Scott A Chamberlain1, J Nathaniel Holland
1Department of Ecology and Evolutionary Biology, Rice University, 6100 South Main Street, Houston, Texas 77005, USA. schamber@rice.edu
Ecology
|June 12, 2008
Summary
Extrafloral nectar (EFN) resources influence ant density on plants. EFN supply affects ant use of floral resources, mediating interactions that are primarily commensalistic, not always mutualistic or antagonistic.
Area of Science:
- Ecology
- Behavioral Ecology
- Plant-Animal Interactions
Background:
- Interspecific interactions are shaped by resource availability and consumer density.
- Ant-plant interactions, particularly involving extrafloral nectar (EFN), can be mutualistic (plant protection) or antagonistic (pollination disruption).
- EFN may influence ant foraging on floral resources, potentially altering interaction outcomes.
Purpose of the Study:
- To investigate how EFN resources mediate ant density and their subsequent use of floral resources on senita cacti.
- To determine if EFN influences the balance between mutualistic and antagonistic ant-plant interactions.
- To understand the context-dependency of consumer-resource interactions in this system.
Main Methods:
- Experimental removal of EFN resources from senita cacti.
- Quantification of ant density on plants over hourly and daily timescales.
- Assessing ant interactions with floral resources through direct observation and behavioral assays.
- Controlling for potential floral deterrents.
Main Results:
- EFN removal significantly reduced aggregative ant density on plants.
- Increased ant density on EFN-rich plants correlated with decreased ant use of floral resources.
- Behavioral assays confirmed EFN, not floral deterrents, mediated ant-flower interactions.
- Plant reproduction benefits (herbivore protection) and negative impacts (pollination disruption) varied across years and populations.
Conclusions:
- EFN resources are key mediators of ant aggregation and influence their use of floral resources.
- Ant use of floral resources is context-dependent, influenced by EFN availability, which can distract ants from flowers.
- Despite strong mediation effects, overall consumer-resource interactions between ants and senita cacti were largely commensalistic.
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