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

Elizabeth W Mccarthy,Steven C Le Comber,Ian T Baldwin,Lin Taylor,Andrew R Leitch,Sandra Knapp,Steven Dodsworth,Mark W Chase,Laura J Kelly,Corinne Mhiri,Lars Chittka,Aleš Kovařík,Robert Verity,Sarah E J Arnold

doi:10.1093/aob/mcv048

Abstract

Background and Aims Speciation in angiosperms can be accompanied by changes in floral colour that may influence pollinator preference and reproductive isolation. This study investigates whether changes in floral colour can accompany polyploid and homoploid hybridization, important processes in angiosperm evolution.Methods Spectral reflectance of corolla tissue was examined for 60 Nicotiana (Solanaceae) accessions (41 taxa) based on spectral shape (corresponding to pigmentation) as well as bee and hummingbird colour perception in order to assess patterns of floral colour evolution. Polyploid and homoploid hybrid spectra were compared with those of their progenitors to evaluate whether hybridization 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. Most younger polyploids displayed an unexpected floral colour, considering those of their progenitors, in the colour perception of at least one pollinator type, whereas older polyploids tended to resemble one or both of their progenitors.Conclusions Floral colour evolution in Nicotiana is weakly constrained by phylogeny, and colour shifts do occur in association with both polyploid and homoploid hybrid divergence. 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. However, those polyploids that are not sympatric (on a regional scale) with their progenitor lineages are typically not divergent in floral colour from them, perhaps because of a lack of competition for pollinators.

Highlights

Polyploidy, or whole-genome multiplication, has played an important role in the evolution of flowering plants (Soltis et al, 2009, 2014)
We will take into account these differences in pollinator perception as we examine floral colour in the genus Nicotiana (Solanaceae)
We investigate the evolution of floral colour across Nicotiana (Solanaceae) in the context of polyploidy and hybridization

Summary

Introduction

Polyploidy, or whole-genome multiplication, has played an important role in the evolution of flowering plants (Soltis et al, 2009, 2014). Allopolyploidy, arising from interspecific hybridization and polyploidy, can cause ‘genomic shock’ (McClintock, 1984), which may trigger a suite of genetic changes, including (retro)transposition, differential gene expression, chromosome rearrangements and epigenetic changes (Leitch and Leitch, 2008) These events and novel cis–trans interactions between progenitor genomes may generate variation, including transgressive phenotypes, and facilitate rapid divergence of both homoploid and allopolyploid hybrids (Wittkopp et al, 2004; Chen, 2007; Gaeta et al, 2007; Anssour et al, 2009; Tirosh et al, 2009; Clare et al, 2013). Speciation in angiosperms can be accompanied by, or perhaps driven by, changes in floral colour that may influence pollinator preference and reproductive isolation Many pollinators, such as bumblebees and hummingbirds, visit a range of flower colours (Waser et al, 1996). This study investigates whether changes in floral colour can accompany polyploid and homoploid hybridization, important processes in angiosperm evolution

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