Histograms of Ka/Ks values calculated from alignment sites of the filovirus-like elements in eleven species of mammals. Values are calculated using Bayesian methods and a model that accommodates neutral, positive and negative selection (M8 below), and a model that accommodates largely negative or purifying selection (M7 above). Note the better fit of the purifying selection model. Red dashed lines indicate the expected values under neutral evolution for non-functional pseudogenes, while values <<1 are consistent with purifying selection.
Taylor et al. BMC Evolutionary Biology 2010 10:193 doi:10.1186/1471-2148-10-193