Corolla morphology and diversification rates in toadflaxes

The role of flower specialization in plant speciation and evolution remains controversial. Fernández-Mazuecos et al. use a time-calibrated phylogeny in conjunction with morphometric analysis to study bifid toadflaxes (Linaria sect. Versicolores), which have highly specialized corollas. They determine that a restrictive character state (narrow corolla tube) is reconstructed in the most-recent common ancestor. After its early loss in the most species-rich clade, this character state has been convergently reacquired in multiple lineages of this clade in recent times, yet it seems to have exerted a negative influence on diversification rates. The results suggest that opposing individual-level and species-level selection pressures may have driven the evolution of pollinator-restrictive traits in the bifid toadflaxes.