K. Odonnell et al., PHYLOGENETIC-RELATIONSHIPS AMONG ASCOMYCETOUS TRUFFLES AND THE TRUE AND FALSE MORELS INFERRED FROM 18S AND 28S RIBOSOMAL DNA-SEQUENCE ANALYSIS, Mycologia, 89(1), 1997, pp. 48-65
Phylogenetic relationships among ascomycetous truffles and the true an
d false morels were examined by using sequences from two nuclear encod
ed ribosomal DNA genes. The data consist of 18S rDNA and partial 28S r
DNA sequences for 29 taxa. Individual and combined data sets were anal
yzed by maximum parsimony (MP), neighbor-joining (NJ) and maximum like
lihood (ML) methods. Parsimony analysis of the combined data set, whic
h contained 3 published 18S sequences and consisted of 2358 nucleotide
characters, yielded a single most parsimonious tree of 1728 steps. Th
e results indicate that the hypogeous ascomycetous truffle and truffle
like taxa studied represent at least 5 independent lineages within the
Pezizales. Results also suggest that several epigeous and most hypoge
ous taxa have been misplaced taxonomically. Bootstrap analyses show st
rong support for a Tuberaceae-Helvellaceae clade which is a monophylet
ic sister group of a Morchellaceae-Discinaceae clade. Rhizina is a sis
ter group to both of these clades in the MP and ML trees while in the
NJ tree it is a sister of the Morchellaceae-Discinaceae clade. MP, ML,
and NJ tree topologies indicate that Rhizina should be removed from t
he Helvellaceae and classified in a monotypic family, the Rhizinaceae.
A phylogenetically-based classification for these fungi is proposed t
ogether with emendations of 4 families.