Insect adaptations toward plant toxins in milkweed–herbivores systems – a review

Abstract

Studies of plant defenses and insect herbivores have been important in the development of our understanding of coevolution and specialization. Milkweed–herbivore systems have been a model for studying plant secondary chemistry defense evolution, insect adaptations to that chemistry, and coevolution between toxic plants and their herbivores for over a century. Yet, we are only beginning to unravel the multitude of adaptations required for insect specialization on milkweed plants. We review the empirical evidence for specialist insect adaptations toward milkweed toxins, coevolution between insects and milkweed plants, and canonical paradigms for sequestration and highlight the areas for further research. By comparing research performed with diverse milkweed insects, we discuss the need to comprehensively study adaptations and specialization in divergent insect taxa.