The biology and taxonomy of Pacific Northwest species of Phaeocollybia Heim (Agaricales, Cortinariaceae)

Abstract

Investigation of the agaric genus Phaeocollybia (Cortinariaceae) in British Columbia, Washington, Oregon and California has led to a better understanding of the biology of the genus and resulted in a taxonomic revision of Pacific Northwest species. Discovery of mycelial and pseudorhizal connections to mantle-sheathed rootlet tips with Hartig nets offers the first good evidence in support of Phaeocollybia as an ectomycorrhizal genus. Basidiome development is traced from subterranean initiation to fully mature emergent basidiomes, and hypotheses on the monovelangiocarpic development of Phaeocollybia basidiomes are developed based on extensive observations of primordia and numerous field excavations. New generically significant characters--pellicular veil, tibiiform diverticula, and sarcodimitic tissues--are examined in depth. Four different pseudorhizal morphologies (vertical-monopodial, lateral-monopodial, sequential-racemose, fasciculate-racemose) are fully explored together with evidence of pseudorhizal meristemoidal activity and rhizomorphic function. Developmentally dependent character variations (e.g., apical extensions from senescent thin-walled cheilocystidia) are identified and discussed.Diagnostic morphological, developmental and ecological characters subjected to computer-assisted multivariate and phenetic cluster analyses are evaluated. Problems caused by length variations of PCR-amplified ITS1+5.8S+ITS2 ribosomal DNA (obtained from 160 specimens representing twenty-six Pacific Northwest and extralimital Phaeocollybias and seven out-taxa) are outlined. Restriction fragment length polymorphisms and restriction site data produced by single digests with nine enzymes are discussed in detail. Phylogenies inferred from computer-assisted cladistic analyses of restriction site data show a high degree of support for previously formed morphologically-based species hypotheses and suggest that sections proposed by previous workers are probably polyphyletic.Nine new species (P. ammiratii, P. benzokauffmanii, P. luteosquamulosa, P. phaeogaleroides, P. pleurocystidiata, P. redheadii, P. rifflipes, P. rufotubulina, and P. tibiikauffmanii) are proposed, P. carmanahensis is synonymized with P. oregonensis, and P. deceptiva (thought to represent Subgenus Telamonia, Cortinarius) is excluded from the genus. Fully revised technical descriptions integrating morphological, ecological, developmental, macrochemical and molecular information for twenty-five currently recognized Pacific Northwest species are accompanied by dichotomous and synoptic keys, line drawings, and full color photographs. Placement of Phaeocollybia within the Cortinariaceae is discussed and an emended generic description presented. Supporting materials include a fully-annotated conspectus to eighty world species.