Convergent changes in gene expression associated with repeated transitions between hummingbird and bee pollinated flowers

Abstract

The repeated evolution of convergent floral shapes and colors in angiosperms has been largely interpreted as the response to pollinator-mediated selection to maximize attraction and efficiency of specific groups of pollinators. The genetic mechanisms contributing to certain flower traits have been studied in detail for model system species, but the extent by which flowers are free to vary and how predictable are the genetic changes underlying flower adaptation to pollinator shifts still remain largely unknown.\n\nHere, we aimed at detecting the genetic basis of the repeated evolution of flower phenotypes associated with pollinator shifts. We assembled and compared de novo transcriptomes of three phylogenetic independent pairs of Gesneriaceae species, each with contrasting flower phenotype adapted to either bee or hummingbird pollination. We assembled and analyzed a total of 14,059 genes and we showed that changes in expression in 550 of them was associated with the pollination syndromes. Among those, we observed genes with function linked to floral color, scent, shape and symmetry, as well as nectar composition. These genes represent candidates genes involved in the build-up of the convergent floral phenotypes.\n\nThis study provides the first insights into the molecular mechanisms underlying the repeated evolution of pollination syndromes. Although the presence of additional lineage-specific responses cannot be excluded, these results suggest that the convergent evolution of genes expression is involved in the convergent build-up of the pollination syndromes. Future studies aiming to directly manipulate certain genes will integrate our knowledge on the key genes for floral transitions and the pace of floral evolution.\n\nData availabilityRaw Illumina reads will be available in the Sequence Read Archive (SRA) in NCBI database. The assembled transcriptomes and their annotation will by available in DRYAD repository. Details and accession ID will be provided at the time of the manuscript acceptance.