Similarity and divergence between the genomes of Salix suchowensis and Populus trichocarpa. (A) Gene collinearity between S. suchowensis and P. trichocarpa. The x-axis corresponds to the Populus chromosomes; and the y-axis corresponds to the Salix scaffolds. (B) Nucleotide alignments between S. suchowensis scaffolds and 19 P. trichocarpa chromosomes. The 19 poplar chromosomes were scaled in their physical length and displayed in a numeric order. For each chromosome, the black bar on the top represents the Populus chromosome, and the black bar under it represents the Salix scaffolds. (C) 4DTv values were separately calculated with paralogs of S. suchowensis and P. trichocarpa, and with orthologs between S. suchowensis and the other four species, including P. trichocarpa, A. thaliana, V. vinifera and O. sativa. (D) The mean substitution rates were estimated using single-copy genes for S. suchowensis, P. trichocarpa, A. thaliana, V. vinifera and O. sativa.