Inferring phylogenetic structure, hybridization and divergence times within Salmoninae (Teleostei: Salmonidae) using RAD-sequencing

Phylogenetic studies focusing on Salmonidae have revealed significant obstacles in trying to clarify some interspecific relationships within the Salmoninae subfamily, due to a limited number of markers typed, conflicting phylogenetic signals and ancient hybridization events. To infer reliable phylogenetic relationships, evaluate several putative scenarios of ancient hybridization, and estimate divergence times within Salmoninae, we applied restriction-site associated DNA sequencing (RAD-seq) to 43 samples, including 26 genetic lineages across 21 species, largely representing the subfamily, with an emphasis on the genus Salvelinus. We identified 28,402 loci and 28,363 putatively unlinked SNPs, which were used in downstream analyses. Using an iterative k-means partitioned dataset and a Maximum Likelihood approach; we generated a well-supported phylogeny, providing clear answers to several previous phylogenetic uncertainties. We detected several significant introgression signals, presumably ancient, in the genus Salvelinus. The most recent common ancestor of Salmonidae dates back to approximately 58.9 MY ago (50.8-64 MY) and the crown age of Salmoninae was estimated to be 37.7 MY (35.2-40.8 MY) using a Bayesian molecular dating analysis with a relaxed molecular clock. The divergence among genera of the subfamily occurred between the late Eocene and middle of the Miocene (approximate to 38-11 MY) such as the divergence between the genus Oncorhynchus and Salvelinus, which we estimated to 21.2 MY ago (95% HPD: 19.8-23.0 MY), while species diversification took place mainly during the Neogene (approximate to 22-1.5 MY), with more than half of these events occurring in the last 10 MY.