Maximum-likelihood tree (-Lnlikelihood = 8827.1373, base frequencies A: 0.2432, C: 0.1830, G: 0.2152, T: 0.3586, shape = 0.8022, pinvar = 0.1926) inferred form the exon + intron sequences of the Acc1 gene of Leymus and its affinitive species, under GTR + G + I model. Numbers with bold above nodes are Bayesian posterior probability values ≥ 90% numbers below nodes are bootstrap values ≥ 50%. The numbers after species names refer to the distinct homoeologous of Acc1 gene. The capital letters in bracket indicate the genome type of the species. Different color labeled the geographic information of Leymus species and its putative donor. Boxed subset provides mismatch distribution and Fs statistic for the Acc1 sequence of taxa at the node marked with black dot. The letter a and b represent two different accessions of Agropyron cristatum. This figure shows the upper quartile, for the full image please see Additional file 4.