The effect of polyploidy and hybridization on the evolution of floral colour in Nicotiana (Solanaceae)

Abstract

Background and Aims: We investigate whether changes in floral colour accompany polyploid and homoploid hybridisation, important processes in angiosperm evolution. Potentially, changes in floral colour can facilitate speciation through pollinator shifts. Methods: We examined spectral reflectance of corolla tissue from 60 Nicotiana (Solanaceae) accessions (41 taxa) based on spectral shape (corresponding to pigmentation) as well as bee and hummingbird colour perception to assess patterns of floral colour evolution. We compared polyploid and homoploid hybrid spectra to those of their progenitors to evaluate whether hybridisation has resulted in floral colour shifts. Key Results: Floral colour categories in Nicotiana seem to have arisen multiple times independently during the evolution of the genus. Polyploid and homoploid hybrids can display a floral colour: 1) intermediate between progenitors, 2) like one or other progenitor, or 3) a transgressive or divergent colour not present in either progenitor. Conclusions: Floral colour evolution in Nicotiana is weakly constrained by phylogeny, but colour shifts occur and are sometimes associated with allopolyploid or homoploid speciation. Transgressive floral colour in N. tabacum has arisen by inheritance of anthocyanin pigmentation from its paternal progenitor while having a plastid phenotype like its maternal progenitor. Potentially, floral colour evolution has been driven by, or resulted in, pollinator shifts