Figure 3.

Three possible models of the evolution of Msp-1 group I and group II alleles. (A) After an ancient bottleneck, only two alleles survive; these two alleles each give rise to new alleles over time. We expect the two allele groups to be very heterogeneous within groups, and more so between groups, with respect to both synonymous and nonsynonymous substitutions. (B) After a recent bottleneck, only two alleles survive, each of which give rise to new alleles. Alleles within a group are fairly similar to each other but alleles from different groups are very heterogeneous throughout the length of the gene, with respect to synonymous and nonsynonymous substitutions. (C) After a recent bottleneck, only one allele survives that gives rise to new alleles over time. Alleles within and between groups are similar, except for occasional (mostly synonymous) substitutions and for differences generated by intragenic recombination, evidenced by the presence of repeats. A and B are inconsistent with the data in Table 6.