Constraints on the evolution of host choice by phytophagous insects

An important question for the evolution of host specialization in insect herbivores concerns why evolutionary changes in host choice mainly affect specificity in some species and the rank order of preference in others. A qualitative model is developed in which evolutionary change in specificity (and conservatism of the rank order of preference) results from functional and genetic integration between life history and behavioral traits. Conversely, another model proposes that a lack of such functional and genetic integration allows the expression of a potential tradeoff between the number of host used and the ability to detect or recognize them, which ultimately favors evolutionarily labile rank order of preference. Quantitative and population genetic approaches are appropriate to test both models.