Structural innovation in the evolution of plant chemical defense

species examined here, and species producing N,S-cardenolides exhibit greater cardenolide abundance, richness, metabolomic space, and toxicity against adapted organisms. More generally, structural innovation defines a distinct evolutionary axis in plant chemistry, enabling defense diversification and adaptive recovery of toxicity. Such innovations are predicted to build on existing molecular scaffolds in response to ecological challenges, here driven by coevolving specialist herbivores.