show Abstracthide AbstractSalix L. is the biggest genus of Salicaceae sensu lato (s.l.). The genus has been proposed to be subdivided into two main clades: clade Salix, comprising species with XY sex determination systems (SDSs) on chromosome 7, and clade Vetrix including species with ZW SDSs on chromosome 15. In this study we aimed to test whether the different SDSs of the two main clades serves as reproductive barriers between the respective species. Here we used whole genome re-sequencing (WGR) data of representatives of Salix to generate SNPs of autosomes, sex-linked regions (SLRs), and the chloroplast genome to reconstruct the backbone phylogeny of Salix.We used part of these data and other sequenced individuals of Salix polyclona complex, to identify the type of tetraploid (allo vs auto) in the complex, to clarify the origin and evolution of the complex.