Fig. 2. This proposed phylogenetic tree for the voltage-gated Na+ channel 
subunits was generated using sequences of the channels listed in Tables 1 and 2. The mammalian channels are in blue, the non-mammalian vertebrate channels are in green and the invertebrate channels are in red. This unrooted tree represents the optimal tree based on parsimony analysis of nucleotide sequences. To perform the analysis, the amino acid sequences for all the isoforms were aligned using Clustal W (Thompson et al., 1994). The amino acid sequences in the alignments were then replaced with the published nucleotide sequences, and the nucleotide sequence alignments were subjected to analysis using the program PAUP* (Swofford, 1998). Divergent portions, including most of the terminal regions and the cytoplasmic loops between domains I and II and domains II and III, were excluded from the PAUP* analysis. The numbers at the nodes indicate the bootstrap values for 100 replications. When a number is not indicated, the bootstrap value was less than 50. The scale bar represents 500 substitutions. Channels and species are identified in Tables 1 and 2.
