Résumé
Aim Scenarios of aphid evolution suggest that adaptation to host plants plays a major role in aphid diversification. It is therefore commonly assumed that host association has also shaped the biogeographical patterns of aphids; particularly, it has been hypothesized that the intercontinental disjunctions observed in the Holarctic for many aphid groups resulted from the disappearance or migration of their hosts. We explored this hypothesis for the conifer-feeding genus Cinara, one of the most diverse and widely distributed aphid genera in the Holarctic. Location Holarctic. Methods Six DNA fragments from 361 specimens representing 92 species were used to reconstruct the phylogeny of Cinara species. We used species-delimitation methods to identify putative species, and estimated times of divergence using Bayesian relaxed clocks and fossil calibrations. We investigated rates of diversification, biogeographical and host-association history using maximum likelihood and Bayesian approaches. Results Cinara originated in Asia c. 50Ma following a host switch to conifers from an angiosperm-feeding ancestor. The steady diversification observed since then suggests that this host switch did not cause adaptive radiation in Cinara, as previously assumed. Switches between conifer host genera could have facilitated the expansion of Cinara in the Holarctic, but the intercontinental disjunctions observed today are most likely the result of vicariance mediated by climatic or geological barriers Main conclusions This study shows that biogeographical and diversification patterns in Cinara have not only been shaped by host-plant adaptation processes, but also by the climatic and geological changes that occurred through the Cenozoic.