Molecular phylogeny of tropical Hymenochaetales (Basidiomycota)

The present work encompasses the investigation of phylogenetic relationships of 11 species of tropical Hymenochaetales through cladistic methodology using unweighted and weighted maximum-parsimony, outgroup polarization of characters, and branch-and-bound algorithm for the search of equally most parsimonious trees. The data set comprises the complete sequencing of the D3 divergent domain of the nuclear gene that codes for the 25S large subunit of ribosomal RNA. The parsimony analyses corroborates the ingroup monophyly (Hymenochaetales), the sister group relationship between Hymenochaetales and Trichaptum, and the polyphyletism of Phellinus and the Phellinus rimosus species complex. These findings suggest that incrusted hymenial cystidia (Trichaptum) and hymenial setae (Hymenochaetales) are homologous structures. The presence of many short branches in the phylogeny is presumed to be related to cladogenetic events separated by short periods of time. Thus the large number of current tropical species of Phellinus sensu lato may be of recent origin.