Evolution of the mitochondrial DNA cytochrome b gene in Tetraonidae birds

Mitochondrial fragments containing the cytochrome b gene (1020 bp in size) of four bird species belonging to four genera of the family Tetraonidae (Tetrao parvirostris, Bonasa umbellus, Lagopus lagopus scoticus, and Falcipennis falcipennis) were directly sequenced. Of the 1020 nucleotide positions, 186 were variable and uniformly distributed over the gene and only 46 were parsimony informative. Most substitutions were synonymous. Replacement substitutions were detected for 15 out of 340 amino acid sites; only four replacements were parsimony informative. The greatest codon bias was found for leucine and serine. The C-T transitions and the G-C transversions were, respectively, the most common (60.7%) and the most rare (5.9%). The mutation frequencies were high at the third codon position (85.2%) and relatively low at the first and the second position. At the third codon position of the species examined, the guanine content was the lowest (3.3%) and the cytosine content was the highest (44.5%). Based on the cytochrome b gene sequences, phylogenetic relationships in the order Galliformes are inferred.