Performance of maximum parsimony (MP) and maximum likelihood (ML) phylogenetic methods for varying levels of heterotachy (τ) while going from the Felsenstein zone to the Farris zone. Nine combinations of p and q (a-i) were explored by realising a morphing from one zone to the other by transferring a part of the length of the branch leading to A to the branch leading to D. The accuracy was calculated as in ref.  with BL50, i.e. the estimated internal branch length that allows recovering the true tree 50% of the time in 100 simulations using PAUP* . As in the classical case , ML is more accurate than MP in the Felsenstein zone and the situation reverts when entering the Farris zone were MP is less affected than ML by increasing the level of heterotachy. However, the accuracy of ML always decreases with increasing value of τ, whereas the effect of heterotachy on MP is more complex, sometimes it increases but generally it also decreases its accuracy.