Figure 1.

Relationships between Ts (%) and Tv (%) per site in the cytb (●) and cr (○) full-length nucleotide sequences of the Darwin’s finches and the dull-colored grassquit. Ts and Tv were obtained by the Tamura-Nei (11) method in mean pairwise comparison of all 14 tested species. The low degree of sequence divergence (<2% at either segment within Darwin’s finches) results in little or no substitutional saturation. A 10:1 ratio of Ts to Tv is found in comparisons within Darwin’s finches; transitional saturation is indicated only in comparisons involving the dull-colored grassquit, for which the ratio falls to 5:1. All per site Tv levels above 0.5% are those between Darwin’s finches and the grassquit.