Fig. 4

Phylogenetic tree of 9 Salix and one Populus species. a NJ tree. Phylogram derived using pairwise synonymous substitution rates of orthologous transcripts as a distance metric (not from multiple sequence alignments) and the neighbour-joining method. b ML tree. Phylogram derived using 238 single copy genes and the maximum-likelihood method. Original trees were shown in Additional file 4: Figure S2