Phylogenetic study of Trichaptum inferred from nuclear ribosomal DNA sequences

For the phylogenetic study of the genus Trichaptum, nuclear ribosomal DNA sequences from eight strains of four Trichaptum species were examined. Phylogenetic trees were constructed using molecular data on 18S rDNA and 5.8S rDNA and their ITSs. Parsimony analyses of the Trichaptum species showed that T. biforme and T. laricinum made a monophyletic group respectively, suggesting that each species is phylogenetically independent. However, T. abietinum represented a polyphyletic group and T. fusco-violaceum formed a polytomous group, suggesting that these species could be in the process of evolutionary differentiation. Examination of base substitutions of the 18S rRNA gene reveals that the C-T transition is most predominant and that there is a stronger transition bias between closely related organisms rather than between distantly related ones.