Systematics of Lyophyllum Section Difformia Based on Evidence from Culture Studies and Ribosomal DNA Sequences

ABSTRACT

Molecular sequence data were employed to determine phylogenetic relationships among species of agaric fungi in Lyophyllum. Pure cultures were obtained from taxa chosen to represent several sections within Lyophyllum including several species within the L. decastes complex. Cultures were also obtained from several species which might be related to Lyophyllum, including L. ulmarium (= Hypsizygus ulmarius) and Tricholoma giganteum. Analysis of culture characters for species which could be grown on malt-asparagine media revealed differences in growth and morphology between species. For phylogenetic analyses, the polymerase chain reaction was employed to amplify a portion of the large subunit ribosomal RNA gene from genomic DNA samples for sequencing. Results of parsimony analyses based on 250 nucleotide positions from 18 strains support species groupings within the L. decastes complex which are consistent with differences in fruit body morphology and culture characters. Results from these analyses also indicate that L. connatum is not monophyletic with other taxa from the L. decastes group, thus indicating that section Difformia is not monophyletic. A narrower circumscription is proposed for section Difformia, restricted to L. decastes and its closely related species.

Key Words:

• rDNA
• species concept