Independent phylogenetic contrasts for pathogens and their closest non-pathogenic relatives. Recent phylogenomics studies support relationships presented here [48, 49]. The distribution of gene family sizes in each genome is assumed to follow a power law, and the data fit to this distribution by maximum likelihood. Family size versus frequency data shown here are plotted on log-log-scales. Likelihood ratio tests were used to determine if pathogens (blue text) had larger gene families (blue shading), smaller gene families (red shading) or no significant difference in the distribution of gene family sizes distribution (grey shading), as compared to their closest non-pathogenic (red text) relative. P-values indicate the significance of these tests (with the null hypothesis that the power law coefficient, a, is the same for the pathogenic and the non-pathogenic species in each paired comparison). Values for the differences in the log likelihoods (i.e., 2ΔlnL) used to infer P-values are also given.