FIG. 2.

Congruence (r² = 0.88) of the time scale and the p-distance of the tlc gene. The time scale was derived from independent estimates obtained from the literature (13, 26) and on the basis of 16S rRNA gene sequence divergence (20). The p-distance between each node and the midpoint of the neighbor-joining tree inferred from the amino acid sequences of the ADP/ATP translocase represent the proportion (p) of amino acid sites at which the sequence is different from that of the ancestral sequence, at the time of duplication of the Chlamydiales ADP/ATP-translocase-encoding gene (tlc). Symbols: •, divergence of H. obtusa and Rickettsia spp.; ▪, divergence of Parachlamydia spp. and Chlamydiaceae; □, divergence of red algae and green plants; ▴, divergence of C. pneumoniae and Chlamydia spp.; ○, divergence of monocotyledons and dicotyledons; ▾, divergence of C. trachomatis and C. muridarum; ⧫, Rickettsia spp. Lines: solid line, regression line (t = −4.11p + 1.28); dotted lines, confidence intervals (t = −4.11p + 1.13 and t = −4.11p + 1.43).