Beyond preference and performance: host plant selection by monarch butterflies, Danaus plexippus

The connection between adult preferences and offspring performance is long-standing issue in understanding the evolutionary and ecological forces that dictate host associations and specialization in herbivorous insects. Indeed, decisions made by females about where to lay their eggs have direct consequences for fitness and are influenced by interacting factors including offspring performance, defence, and competition. Nonetheless, in addition to these attributes of the offspring, a female’s choices may be affected by her own prior experience. Here we examined oviposition preference, larval performance, and the role of learning in the monarch butterfly, Danaus plexippus, which encounters diverse milkweed host species across its broad range and over the course of migration. Monarch females consistently preferred to oviposit on Asclepias incarnata subspecies pulchra. This plant, however, was associated with poor caterpillar growth, low sequestration of toxins, and the highest plant defence...