Browsing by Author "Aime, Mary Catherine"

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    Biosystematic Studies in Crepidotus and the Crepidotaceae (Basidiomycetes, Agaricales)
    Aime, Mary Catherine (Virginia Tech, 2001-05-01)
    Fungi of the Crepidotaceae are characterized by saprotrophic habit, filamentous cuticle, and brown-pigmented basidiospores that lack either a germ pore or plage. The majority of species belong to Crepidotus, distinguished by their pleurotoid basidiomata. Because of their diverse morphology, the presence of several conflicting classifications, and lack of data regarding the biology, phenotypic plasticity, or phylogeny of these fungi, the present study sought first to determine phylogenetic relationships among the different taxonomic groups as a basis for addressing other aspects of Crepidotus biology and evolution. Sequencing analyses show the Crepidotaceae is not monophyletic, and the family concept is revised. Crepidotus and its sister genus Simocybe are found to be monophyletic. At least nine phylogenetic lineages within Crepidotus were uncovered, although relationships between them could not be resolved. However, none of the previously proposed infrageneric classifications are reflective of phylogeny. Morphological, biological, and phylogenetic species concepts were compared within a single phylogenetic unit, termed the Sphaerula group, showing an unusual amount of phenotypic plasticity exists within species, and a taxonomic revision of these species proposed. Also reported are several unique or unusual aspects of Crepidotus biology, including presence of a prolonged latent period prior to basidiospore germination; spontaneous reversion of differentiated hymenial cells to vegetative growth; and the revelation that structures previously termed pleurocystidia are actually the expression of secondary growth from basidia. Results from mating system, culture, and type studies, reassessment of morphological characters traditionally applied to agaric taxonomy, and a revised life cycle for the Crepidoti are presented.
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    Generic concepts in the Crepidotaceae as inferred from nuclear large subunit ribosomal DNA sequences, morphology, and basidiospore dormancy patterns
    Aime, Mary Catherine (Virginia Tech, 1998-11-19)
    The Crepidotaceae (Imai) Singer (Basidiomycetes: Agaricales) represents a proposed family of saprophytic fungi containing five agaricoid (Crepidotus, Tubaria, Melanomphalia, Simocybe, Pleurotellus) and four cyphelloid (Episphaeria, Phaeosolenia, Pellidiscus, Chromocyphella) genera. Several contemporary classification systems exist that delegate some or all of these genera to other agaric families. Phylogenetic relationships for the most prevalent genera in the Crepidotaceae were investigated using nuclear large subunit ribosomal DNA (LSU rDNA) sequences. Parsimony analysis of the molecular data supports the Singer classification of Crepidotus, Melanomphalia, and Simocybe as a single monophyletic unit within the Agaricales. The affinities of the genus Tubaria remain uncertain. Crepidotus (Fr.) Staude is the largest and most phenotypically variable genus in the Crepidotaceae. Sequencing of the LSU rDNA region for a cross-section of morphologically diverse species suggests that Crepidotus is not a monophyletic genus. Analysis of morphological characters for 23 Crepidotus taxa shows that characters traditionally applied for infrageneric classification of Crepidotus are homoplasic in origin, but that less commonly emphasized characters such as spore shape and ultrastructure of spore wall ornamentation may be indicative of monophyletic clades for this complex. A unique pattern of basidiospore dormancy and germination, unknown in any other species of agaric, is reported for 11 species of Crepidotus. Similar patterns were also encountered in species of Simocybe and Melanomphalia. In these species an endogenous period of spore dormancy of four to six months is followed by an activation period where the factors necessary for subsequent germination appear to involve a minimal nutritional component, water, and exposure to light.