Analysis of positive selection using McDonald-Kreitman test.^a

aOutlier sequences were not removed prior to these analyses. bThe neutrality index (NI) was calculated from the ratio of the number of polymorphisms to the number of substitutions as follows: NI = (Pn/Ps)/(Dn/Ds), where P is polymorphic within the population, D is divergence or fixed difference between populations, n is nonsynonymous, and s is synonymous. cThe proportion of adaptive substitutions that ranges from - ∞ to 1 and is estimated as 1 - NI. dNot applicable. HomB is absent from strain 26695. *Asterisks indicate genes showing signatures of diversifying selection.