Figure 1.

Neighbor-joining tree derived from an analysis of intron 4 sequences. The distances were computed by using Kimura’s (26) two-parameter method. The number at each node denotes the proportion of 500 bootstrap replicates that supported the subset of sequences. The number in brackets below each branch denotes the number of indels supporting the monophyly of the three alleles in each species. A dashed arrow with a number in brackets denotes the number of indels shared by two alleles. The seven numbers listed vertically at the upper right of the tree refer to the positions of the seven critical amino acid sites. The sequence alignment and the positions and sizes of indels are available on request from W.-H.L.