Adaptive radiation, i.e. the evolution of ecological and phenotypic diversity within a rapidly multiplying lineage, involves the differentiation of a single ancestor into an array of species that inhabit a variety of environments and that differ in the morphological and physiological traits used to exploit those environments. Recently a suite of mechanisms has been proposed to explain the evolutionary radiation of stenophagous clades within the genus Ceratitis. One hypothesis suggests that toxic components present in host plant may restrain or preclude the larval development of intolerant (polyphagous) species, which would explain why many hosts infested by stenophagous Ceratitis species are toxic. If correct, ancestors of the current stenophagous clades may have developed a tolerance against these toxic elements, resulting in the infestation of new toxic environments and subsequent cladogenesis.

The main aim of this study is to test to which degree plant toxicity affects the development and fitness of selected species of stenophagous and polyphagous Ceratitis species, and how this links with the observed pattern of cladogenesis. These questions are addressed through a combination of controlled laboratory experiments and molecular analysis.