A Framework for Predicting Intraspecific Variation in Plant Defense

One of the most well-supported theories regarding the evolution of plant defenses is the resource availability hypothesis (RAH). RAH posits that species from high-resource environments grow fast and allocate little to herbivore-resistance traits, whereas those species in low-resource environments grow slow and are highly resistant to herbivores. However, within species, how resources influence defense is unclear and existing theories make opposing predictions. Here, we review studies documenting intraspecific variation in plant defense across resource gradients and find little support for RAH. We outline why RAH does not apply intraspecifically and present a predictive framework for understanding how resources influence intraspecific variation in plant defense. Our framework provides an important step towards reconciling inter- versus intraspecific strategies of defense.