Pollinator shifts, contingent evolution, and evolutionary constraint drive floral disparity inSalvia(Lamiaceae): Evidence from morphometrics and phylogenetic comparative methods

Abstract

Switches in pollinators have been argued to be key drivers of floral evolution in angiosperms. However, few studies have tested the relationship between floral shape evolution and switches in pollination in large clades. In concert with a dated phylogeny, we present a morphometric analysis of corolla, anther connective, and style shape across 44% of nearly 1000 species ofSalvia(Lamiaceae) and test four hypotheses of floral evolution. We demonstrate that floral morphospace of New World (NW)Salviais largely distinct from that of Old World (OW)Salviaand that these differences are pollinator driven; shifts in floral morphology sometimes mirror shifts in pollinators; anther connectives (key constituents of theSalviastaminal lever) and styles co-evolved from curved to linear shapes following shifts from bee to bird pollination; and morphological differences between NW and OW bee flowers are partly the legacy of constraints imposed by an earlier shift to bird pollination in the NW. The distinctive staminal lever inSalviais a morphologically diverse structure that has evolved in concert with both the corolla and style, under different pollinator pressures, and in contingent fashion.