Pollinator shifts and the evolution of floral advertising traits in the genus Ferraria (Iridaceae)

Abstract

One of the most compelling explanations for floral trait diversification and speciation in angiosperms is the process of pollinator shifts. The African genus, Ferraria, is a relatively small and understudied group of irises which interacts with many distinct pollinator groups and exhibits large variation in floral scent and colour. We built a phylogeny for the genus using three chloroplast gene regions and reconstructed the joint evolutionary history of pollination systems and floral traits. We found evidence for several historical shifts amongst pollinator functional groups and associations between pollinators and certain floral visual cues and mechanical fit traits. We also found evidence that colour divergence in Ferraria flowers evolved through non-random evolution. This indicates that pollinators may have played an important role in the diversification of visual floral traits within the genus. On the other hand, we found no association between pollinators and the overall scent chemistry of the flowers that they visited. This indicates that various olfactory cue combinations may attract similar pollinator assemblages, or that chemical compounds involved in pollinator attraction comprise only a small subset of all emitted compounds. Overall, these results suggest that adaptations to pollinators have influenced floral trait evolution within Ferraria.