On mutualists and exploiters: plant-insect coevolution in pollinating seed-parasite systems.

Area of Science:

• Ecology
• Evolutionary Biology
• Behavioral Ecology

Background:

• Obligate plant-insect associations involve complex interactions where insects act as both pollinators and seed parasites.
• The timing of ecological events, such as flowering and pollinator emergence, is crucial for species survival and reproductive success.

Purpose of the Study:

• To investigate the coevolutionary dynamics between plant flowering time and insect pollinator emergence time.
• To understand the evolutionary stability and potential for coexistence in systems with pollinating seed-parasites.

Main Methods:

• Numerical analysis of coevolutionary models.
• Examination of evolutionary stable strategies (ESS) for flowering and emergence times.
• Analysis of selection pressures and fitness landscapes.

Main Results:

• The system often evolves towards flowering times that differ from environmentally optimal periods.
• Plant flowering time can reach a local fitness maximum (ESS), while insect emergence time may evolve to a local fitness minimum.
• Disruptive selection on insect emergence time can lead to the coexistence of early and late emerging pollinators.

Conclusions:

• Coevolution in these systems can result in plant phenologies detached from abiotic conditions.
• The evolution of a fitness minimum for insect emergence facilitates the coexistence of different pollinator phenologies.
• Pollinating seed-parasite systems are likely to exhibit stable coexistence between mutualistic pollinators and exploitative 'cheater' insects over evolutionary timescales.