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. 1997 Apr 29;94(9):4510–4515. doi: 10.1073/pnas.94.9.4510

Figure 1.

Figure 1

Phylogenetic placement of orchid fungi. (a) Each orchid targets a distinct clade of ectomycorrhizal fungi. ML5–6 sequences from symbionts of both orchids were aligned with those from fruit bodies of 112 (mostly ECM) Basidiomycete species. This database has been used previously (19, 34); details will be presented elsewhere. Analysis by the distance method of neighbor-joining under a Jukes–Cantor one-parameter model using paup 4.0 (39) produced a tree in which all symbionts of C. austinae were grouped several nodes interior to the boundaries of the Thelephorales, and all unknown symbionts of C. maculata were similarly grouped well within the Russulales. These placements were strongly supported by a 1000 replicate neighbor-joining boot strap analysis (numbers near branches). Most taxa were then pruned from the tree, leaving a taxon from each major clade in the representation above. Cantharellus was used as the outgroup. (b) ITS sequences provide strong, independent evidence for the placement of the symbionts of C. austinae in a clade within the Thelephoraceae. ITS sequences were generated for each fungal ITS RFLP type associated with C. austinae and from fruit bodies of the Thelephoraceae. ITS sequences were obtained for Sarcodon imbricatum, Hydnum umbilicatum, Hydnellum peckii, and Pseudotomentella trisitis in addition to the taxa shown above. However, none of these could be aligned with the ITS sequences obtained from Cephalanthera associates or Thelephora and Tomentella fruit bodies. Parsimony analysis using 100 random addition replicates of the remaining taxa by paup produced the single tree, shown above. Midpoint rooting was used because of lack of an a priori choice for outgroup. The neighbor-joining tree also agreed with all well supported branches from the parsimony analysis. Parsimony boot strap values from 1000 replicates are shown above branches, and decay indices are shown below branches. Although taxa sampling was limited, this analysis provides evidence that all Cephalanthera associates are more closely related to Thelephora and Tomentella than to other sampled genera of the Thelephoraceae.