The Evolutionary Ecology of Plant Chemical Defenses: From Molecules to Communities

Classic theory relates herbivore pressure to the ecology and evolution of plant defenses. Here, we summarize current trends in the study of plant–herbivore interactions and how they shape the evolution of plant chemical defenses, host choice, and community composition and diversity. Inter- and intraspecific variation in defense investment is driven by resource availability. The evolution of defenses at deeper nodes of plant phylogeny is conserved, yet defenses are highly labile at the tips. On an ecological timescale, while greater specialization of tropical herbivores enhances local diversity by reducing the performance of plants with similar defenses, in temperate ecosystems with more generalist herbivores, rare defense profiles are at a disadvantage. On an evolutionary timescale, host choice by herbivores is largely determined by plant defenses rather than host phylogeny, leading to evolutionary tracking by herbivores rather than cocladogenesis. The interplay between plants and herbivores shapes both the origin and maintenance of diversity. Expected final online publication date for the Annual Review of Ecology, Evolution, and Systematics, Volume 54 is November 2023. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.