Figure 2
From: EM for phylogenetic topology reconstruction on nonhomogeneous data
Tree with two parameters as branch lengths. Four-taxon tree used to simulate data in the Huelsenbeck tree space. Parameter a denotes the length of the inner and two outer branches and parameter b is the length of the other peripheral branches. Branch length is measured as the expected number of substitutions per site and varies between 0.01 and 0.75 in our simulations.