Plant–insect interactions: double-dating associated insect and plant lineages reveals asynchronous radiations

An increasing number of plant-insect studies using phylogenetic analysis suggest that cospeciation events are rare in plant–insect systems. Instead, nonrandom patterns of phylogenetic congruence are produced by phylogenetically conserved host switching (to related plants) or tracking of particular resources or traits (e.g., chemical). The dominance of host switching in many phytophagous insect groups may make the detection of genuine cospeciation events difficult. One important test of putative cospeciation events is to verify whether reciprocal speciation is temporally plausible. We explored techniques for double-dating of both plant and insect phylogenies. We use dated molecular phylogenies of a psyllid (Hemiptera)–Genisteae (Fabaceae) system, a predominantly monophagous insect–plant association widespread on the Atlantic Macaronesian islands. Phylogenetic reconciliation analysis suggests high levels of parallel cladogenesis between legumes and psyllids. However, dating using molecula...