Figure 2.

Fifty percent majority-rule NJ bootstrap tree (500 replications) (24) and groupings compatible with it, based on Shh exon 1 (A) and Shh exon 2 (B). Nodes with bootstrap values below 50% were forced to collapse. Shh exon 1 was found to have less phylogenetic resolution than Shh exon 2, reflecting its extremely low rate of evolution. Hence, it is likely that both exon 1 and exon 2 domains are functionally important. Goldfish (Carassius auratus) was used as an outgroup for all trees.