Fig. 2
Cushion willow evolution. a Circos plot showing the genomic features of Salix brachista. The features highlighted from innermost to outermost circle are (i) intra-genome collinear blocks connected by curved lines, (ii) GC content (30%–50%), (iii) SNP density, (iv) gene density (0–50 per window), (v) distribution of Class II TE (scale: 0%–5%), (vi) distribution of Class I TE (scale: 0%–5%). All statistics are computed for windows of 200 kb. b Gene family evolution of Cushion willow. The phylogenetic tree was constructed from sequences of 3040 single-copy genes shared by ingroup Sal-SP species. The number of gene families that expanded (turquoise), contracted (magenta) and were rapidly evolving (blue) in each lineage after speciation are indicated above the corresponding branch. c Gene collinearity between S. brachista and P. trichocarpa. The x-axis and y-axis correspond to the P. trichocarpa and S. brachista chromosomes, respectively. d Collinearity between chromosome 1 and 16 of S. brachista and P. trichocarpa
