Progress toward a phylogenetic classification of the Polyporaceae through parsimony analysis of mitochondrial ribosomal DNA sequences

Abstract

We used sequence data from mitochondrial small-subunit ribosomal DNA to infer phylogenetic relationships of the Polyporaceae. We examined 62 species representing 14 families of Aphyllophorales and Agaricales. Parsimony analyses of these sequences suggest that the Polyporaceae are polyphyletic. Higher order relationships are poorly resolved, but seven groups of species are generally well supported (as measured by bootstrapping) or are congruent with previous taxonomic hypotheses. Group 1 includes Polyporus s.str., seven other genera of Polyporaceae, Lentinus, and Ganoderma. Because this clade contains the type species of Polyporus, it may serve as the core for a future recircumscription of the Polyporaceae. Group 2 is morphologically and ecologically diverse, but all members have amyloid, ornamented spores (with the possible exception of Heterobasidion). This group includes Bondarzewia, Heterobasidion, Hericium, Echinodontium, Lentinellus, Auriscalpium, and Russula. Group 3 includes five exemplars of the Hymenochaetaceae, as well as Oxyporus and Trichaptum. Trichaptum and members of the Hymenochaetaceae are unusual among the holobasidiomycetes in their possession of imperforate parenthosomes. Group 4 represents the Boletaceae and includes Boletus and Suillus. Group 5 includes Bjerkandera, which is a polypore, and Pulcherricium and Phanerochaete, which are corticioid. In Group 5 the corticioid habit may have been derived by reduction. Group 6 includes Fomitopsis, Piptoporus, and Daedalea, all of which are brown rot polypores with bipolar mating systems. Group 7 includes Laetiporus and Phaeolus. Laetiporus is classified in Polyporaceae, but Phaeolus has been placed in both the Polyporaceae and Hymenochaetaceae. In general, our results suggest that macromorphology is evolutionarily flexible, but that certain anatomical and physiological characters, while not free from homoplasy, contain clues to higher order relationships of polypores. Key words: Aphyllophorales, basidiomycetes, classification, phylogeny, Polyporaceae, ribosomal DNA.