Selectively neutral and negatively selected recurrent mutations mapped on gene genealogy. Panels A and B schematically illustrate recurrent mutations that are selectively neutral and negatively selected, respectively, mapped on genealogies of n (=14) sequences. M=3 mutation events of the same nature are assumed to have occurred along each genealogy. When the mutations are neutral (A), at least one of them is likely to result in substantially more than one mutant in the sample. When the mutations are negatively selected (B), in contrast, it is likely that every mutation event leaves very few (often one) sampled mutant(s), and the mutant lineages are usually short-lived. NOTATION. In both panels, open and shaded circles represent selectively neutral and negatively selected sampled sequences, respectively. A lightening bolt denotes a mutation event.