Figure 2.

(A) Phylogenetic relationships (ln likelihood = −7370.71124) of 30 species of Omphalina and related genera. The number below each internode is the percentage of 350 bootstrap replicates supporting the same binary partition as shown in this figure. Boostrap values ≤50% are not shown. In green are lichen-forming fungal lineages associated with the green alga Coccomyxa. In blue are fungal lineages mutualistically associated with thallose liverworts. (B, D, and F) Each column represents all pairwise comparisons between one species (species “a,” black box) and the remaining 29 species (species “x,” nonblack boxes). A white box indicates that the evolutionary rate of species x does not differ from the rate of species a. A colored box indicates that species x is significantly (P < 0.05) slower than species a. Significant differences in rates of nucleotide substitution were subdivided into four types: (i) Blue boxes represent cases in which rate differences are due to a significant difference in rates of transitions only; (ii) yellow boxes indicate that rate differences are due to significant differences in rates of transitions and rates of transversions; (iii) red boxes represent cases in which the rate differences are due to significant differences in rates of transversions only; and (iv) green boxes represent cases in which the rate difference is not due to a significant difference in rates of transitions nor rates of transversions when tested separately. For example, in the first column (B), the evolutionary rate of Gerronema subclavatum (Peck) Redhead was not significantly faster than G. strombodes (Berk. & Mont.) Sing. The evolutionary rate of G. subclavatum was significantly faster than Hygrocybe citrinopallida (Smith & Hesler) Kobay, and this significant rate difference is due to a significant difference in rates of transversions only. The presence of red and yellow boxes for the 25S and ITS1+ITS2 (B and D) emphasizes their fast evolutionary rates, compared with the slowly evolving 5.8S, which is entirely blue (F). For space considerations, columns were not created for species that were not significantly faster than any other taxon, i.e., taxa with no black box in their respective row (e.g., Hygrocybe citrinopallida). (C, E, and G) Evolutionary rate categories (f = fast, s = slow) and symbiotic states (m = obligatory mutualist, nm = nonmutualist) represent the two characters tested for correlated evolution by one of the two analyses used in this study (see Table 1 for the results of this test).