CORRELATES AND GENETIC BASIS OF PLANT DIVERSIFICATION IN THE NEOTROPICS: THE GESNERIACEAE AS A CASE STUDY

The temporal building of plant biodiversity is a fascinating and extensive research area in evolutionary biology. The striking patterns of species richness in the Neotropical area, and the variety of floral forms, have long challenged our understanding of how plant speciation proceeds, what is required for acquiring reproductive isolation, and which are the factors that may promote it. In this thesis, I combine macro-evolutionary and genetic approaches at an integrative taxonomic and temporal scale to investigate the diversification processes shaping the captivating Gesneriaceae plant family. In the first section, I identify the dynamics of evolution of floral morphologies and climatic preferences within an epiphytic and endemic lineage of the gesneriads. I show a strong decoupling in the evolution of floral shape and size that reflects the contrasting influence of plant-pollinator interactions: while floral shapes converge towards optimal morphologies that are highly bounded to specific bee and hummingbird interactions, floral sizes rapidly diverge once hummingbird pollination is established in a lineage. Building on these findings, I reconstruct a large species-level phylogeny, and evaluate the evolution of plant-pollinator interactions at the scale of the whole subfamily. I demonstrate that transitions between pollinator types are very frequent and symmetrical, suggesting a pattern of evolutionarily labile interactions. Moreover, I identify a positive effect of hummingbird-pollination in the rates of speciation. This pattern contrast with the traditional view on pollination-driven plant speciation, which regards shifts between pollinators as the driver of diversity. In the final section, in order to grasp these patterns at fine genetic scale, I generate the transcriptomic data for six closely related species that underwent pollination shifts. I investigate whether parallel genetic changes have produced the alike floral morphologies associated to the same plant-pollinator interactions. This exploration sheds light on the mechanisms associated with flower transformations in the Gesneriaceae, emphasizing the stronger impact of molecular evolution over gene expression differences, and pinpointing to several candidate genes and functional pathways for future research on the evolution of floral morphology. Overall, this work shows how such a multidisciplinary approach at variable evolutionary scales can contribute to disentangle processes that have generated the enormous Neotropical biodiversity that we witness today