Format: ORAL

Lucas VANDENABEELE1, Joris BERTRAND1, Herv PHILIPPE2

1 Laboratoire Génome et Développement des Plantes (LGDP), Université de Perpignan Via Domitia, Perpignan, France 2 Station d’Ecologie Théorique et Expérimentale, Centre National de la Recherche Scientifique (CNRS), Moulis, France

The orchid genus Ophrys is an outstanding example of an important and recent plant adaptive radiation. However, both this rapid diversification and the large size of its genome make its systematics and evolution difficult to study, and most of the phylogenetic hypotheses published so far are either poorly resolved and prone to display gene trees incongruences. In this context, we decided to use phylotranscriptomics as a genome complexity reduction technique to work at the genomic scale and be able to simultaneously obtain and compare thousands of gene trees to improve resolution and tease apart the relative contribution of introgression and Incomplete Lineage Sorting in Ophrys diversification. We de novo assembled more than 150 Ophrys floral transcriptomes to obtain an important pool of orthologous genes that we used to reconstruct a phylogeny of the Ophrys genus with an unprecedented resolution. This phylogeny largely confirms the relationships between the main Ophrys lineages obtained by other methods but also provides new insights within each of these lineages. We show that the incongruence between gene trees is not only due to Incomplete Lineage Sorting. Although introgression has been hypothesised to play an important role in Ophrys evolution we provide for the first time quantitative characterisation of this reticulate evolution at the genus scale. We implemented several introgression tests with different levels of complexity, from D-statistics to phylogenetic network inference, and were able to highlight several complex introgression events between the Ophrys lineages. This introgression analysis provides us a set of introgressed genes which will be further analysed to find their impact on phenotypic variation, in order to explore a putative adaptive role of introgression in Ophrys diversification.