From whole-genome scans for divergence to the discovery of speciation genes in oaks

Understanding the nature, the number and the strength of barriers to gene flow is a major goal in speciation genomics. Yet, few speciation genes have been reported to date in plants. Considering the costs of NGS are still coming down, it becomes possible to identify such speciation genes at the pan-genomic level even for non-model species. This presentation will review our latest advances regarding this research topic within the European white oak complex. We first established a reference genome for oak (1.5Gb/2C) organized into pseudo-chromosomes and used a deep pool sequencing approach to characterize 4 sympatric and interfertile species (Quercus petraea, Q. robur, Q. pyrenaica, Q. pubescens). Even if these species exhibit different ecological requirements (e.g. soil pH or moisture), they are still connected by substantial levels of 'interspecific' gene flow (FST < 0.2). As a consequence, loci related to intrinsic selection against hybrids are expected to be revealed together with the gene driving ecological divergence. A whole-genome scan for divergence was performed using up to 250x genome coverage per species. Here, we report evidences for genomic islands of differentiation and identified some candidate speciation genes for both endogenous and exogenous barriers including some genes involved in flowering or drought tolerance