Coevolution can explain defensive secondary metabolite diversity in plants

Area of Science:

• Evolutionary Biology
• Plant Science
• Chemical Ecology

Background:

• Plant secondary metabolites exhibit significant diversity within and between populations.
• Mechanisms of metabolite production are understood, but evolutionary drivers of diversification are less clear.

Purpose of the Study:

• To investigate the role of plant-herbivore coevolution in maintaining plant secondary metabolite diversity.
• To model the evolutionary dynamics of plant toxins and herbivore resistance.

Main Methods:

• Developed a simple evolutionary model with single-species and reciprocal coevolution scenarios.
• Simulated plant toxin evolution and herbivore resistance evolution.

Main Results:

• Coevolution was shown to maintain toxin diversity within plant populations.
• A coevolutionary asymmetry exists: herbivores must resist all toxins, while plants target one resistance trait.
• Increased toxin numbers benefit plant fitness and decrease herbivore fitness.
• Model demonstrated arms race escalation and fluctuations in toxin concentrations when costs were included.

Conclusions:

• Plant-herbivore coevolution is a key factor in the diversification of plant secondary metabolites.
• Coevolutionary dynamics can lead to escalating chemical defenses and fluctuating toxin levels over time.