Fig. 1

The phylogeny of S. chaenomeloides and S. arbutifolia and identification of the sex determination regions. A Phylogenetic relationship of S. chaenomeloides and S. arbutifolia and other Salicaceae species, using Arabidopsis thaliana as an outgroup. The numbers at the nodes indicate support values based on 100 bootstrap replications. The tree is marked with the type of sex-determining system (orange circles: XY, blue diamonds: ZW), sex chromosomes (numbers within the shapes), and the approximate positions of SDRs on the sex chromosomes. Manhattan plots of S. chaenomeloides (B, C) and S. arbutifolia (E, F) based on the results of genome-wide association study when the female (B, E) and male (C, F) genome was used as reference. The y-axis represents the strength of association (−log₁₀(P-value)) for each SNP sorted by chromosomes and scaffolds (SC; x-axis). The red line indicates the significance after Bonferroni multiple testing correction (α < 0.05). The yellow shadow represents the SDRs, where the genotypes of all SNPs in female and male individuals are colored according to their homozygosity or heterozygosity states. Collinearity relationships between X- and Y-SDR of S. chaenomeloides (D) and S. arbutifolia (G). The reads mapping depth of the female and male corresponding to these areas were displayed above and below the collinearity. The orange and blue lines represent female and male respectively. Solid lines represent the mapping depth across these regions and dotted lines represent the genome-wide average depth