Host sanctions and pollinator cheating in the fig tree-fig wasp mutualism

Area of Science:

• Ecology
• Evolutionary Biology
• Behavioral Ecology

Background:

• Mutualistic interactions are ancient and diverse, yet theory predicts vulnerability to exploitation by 'cheaters'.
• Understanding mechanisms that maintain cooperation is crucial in ecological and evolutionary contexts.

Purpose of the Study:

• To investigate factors maintaining mutualism stability in fig tree-fig wasp interactions.
• To experimentally assess the role of host sanctions in preventing pollinator cheating.

Main Methods:

• Field experiments comparing the fitness of pollinating versus non-pollinating wasps.
• Observations of natural pollinator populations to identify and quantify 'cheaters' (pollen-free wasps).
• Analysis of six fig tree-fig wasp species pairs with varying pollination strategies.

Main Results:

• Host sanctions, which reduce the fitness of non-pollinating wasps, were found in actively pollinated fig species but not passively pollinated ones.
• Pollen-free wasps ('cheaters') were present only in actively pollinating species.
• The prevalence of cheaters was negatively correlated with the strength of host sanctions.

Conclusions:

• Mutualisms can exhibit coevolutionary 'arms races' between partners.
• Sanctions are critical for maintaining long-term mutualism stability when cooperation is costly.
• General principles governing cooperation apply within and among species.