Ortholog-specific phylogenetic trees of the α₂-AR subtypes including the nonmammalian fragments retrieved from GenBank (AL606538 to AL606586), produced using the maximum-parsimony method. The nomenclature of these gene fragments is that present in their GenBank entries. The nucleotide sequences were translated into protein sequences and the alignment was constructed as described in Materials and Methods. Replicate trees, 1,000, were used for the bootstrap analysis. Bootstrap support: values shown next to nodes when less than 80%; closed circles indicate values greater than 80%. The trees are rooted with the zebrafish α₂-AR paralogs. Lengths of the horizontal branches are proportional to the amino acid sequence differences; the length of the scale bar is equal to a 20% difference. For every branch A, B, C, and D, the duplicates hypothetically common to ancestors of different species of fish are boxed. When two duplicates are present, the receptor and species name are underlined, with the exception of the eel receptor sequences, which show partially different branching pattern and lower bootstrap support compared with the other species with duplicates