FIG. 2.

Maximum-likelihood tree inferred from the primary structure alignment shown in Fig. 1. The analysis was limited to the 145 positions marked by the plus symbols in Fig. 1. The quartet puzzling method was used with a gamma-distributed model of site-to-site variation using eight rate categories. The gamma distribution parameter α estimated from the data set was 2.03, and the log-likelihood of the tree was −1,973.18. The scale bar represents 1.0 amino acid substitution per site. Numbers above nodes are quartet puzzling reliability values. Bootstrap confidence levels were comparable to quartet puzzling reliability values.