Research

Our lab group does research in the area of fungal biology in which we study taxonomy, life histories, and systematics – particularly of fungi in the Pezizomycetes, the Orbiliomycetes and recently in the Laboulbeniomycetes.  We are interested in the relationships among the members of these groups, their geographic distribution, and the associations of these fungi with other organisms.  Prof. Pfister has conducted research on topics related to documentation of collections and collectors of natural history specimens; particularly in relationship to the rich and varied collections at Harvard.  Our fieldwork ranges from collecting locally to southern South America.

    Donald H. Pfister

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Curriculum Vitae (CV) 

Recent Publications

Elias Magnus Fries's fungus exsiccati Scleromyceti Sueciae: New light on the obscure “fascicle nine”

Karakehian, J.M., Pfister, D.H. & Miller, A.N., 2024. Elias Magnus Fries's fungus exsiccati Scleromyceti Sueciae: New light on the obscure “fascicle nine” . Taxon , pp. 1-8. Publisher's VersionAbstract
Elias Magnus Fries's fungus exsiccati Scleromyceti Sueciae documents specimens cited in several of Fries's publications that are now considered sanctioning works in the nomenclature and taxonomy of several groups of fungi. The first eight fascicles of the first edition of the Scleromyceti Sueciae were issued periodically during the years 1819–1822. Each fascicle was issued as a bound booklet that included, among other information, a printed title page with a date, and an index followed by 30–40 specimens. A ninth fascicle that concluded the first edition was issued without a date. Scholars of the Scleromyceti Sueciae inferred an approximate date of issuance of mid-1825 based on Fries's correspondence, but they were uncertain whether fascicle nine was issued as a booklet or on loose sheets. In addition, the location of the printed index to fascicle nine that they studied was unclear. We obtained images of a complete, original copy of fascicle nine from the collections of the Natural History Museum of Denmark of the University of Copenhagen. This copy proves that fascicle nine was issued as a bound booklet like the previous eight fascicles and contained a printed index and printed specimen labels. Because of the apparent rarity of a complete, original copy of fascicle nine, we describe the copy at the Natural History Museum of Denmark and provide images of the index. We discuss potential problems in typifying names from material issued in the Scleromyceti Sueciae second edition. Using an example from fascicle nine, we discuss Fries's omissions, errors, and lapses in citing specimens.
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Phylogeny and taxonomy of the genera of Erysiphaceae, part 5: Erysiphe (the “Microsphaera lineage” part 1)

Bradshaw, M., et al., 2024. Phylogeny and taxonomy of the genera of Erysiphaceae, part 5: Erysiphe (the “Microsphaera lineage” part 1). Mycologia , 116 (1) , pp. 106-147. Publisher's VersionAbstract
In this contribution, we offer the fifth installment of a series focusing on the phylogeny and taxonomy of powdery mildews. This paper is the second segment evaluating the genus Erysiphe. The first treatment of Erysiphe focused on phylogenetically basal species in the “Uncinula lineage.” This research presents a phylogenetic-taxonomic assessment of species that form the group previously referred to as the “Microsphaera lineage.” Given the size of the group, we split the treatment of this lineage of Erysiphe species into two parts based on their phylogenetic placement. Phylogenetic trees based on ITS+28S data are supplemented by sequences of additional markers (CAM, GADPH, GS, RPB2, and TUB). Included in the analysis of the Microsphaera lineage is the “Erysiphe aquilegiae complex” (group, clade, cluster), which encompasses sequences obtained from an assemblage of Erysiphe species with insufficient resolution in rDNA analyses. Attempts have been made to resolve this group at the species level by applying a multilocus approach. A detailed discussion of the “Erysiphe aquilegiae complex” is provided. Sequences are provided for the first time for several species, particularly North American species, such as Erysiphe aggregata, E. erineophila, E. parnassiae, and E. semitosta. Ex-type sequences for Microsphaera benzoin and M. magnusii have been retrieved. Alphitomorpha penicillata, Microsphaera vanbruntiana, and M. symphoricarpi are epitypified with ex-epitype sequences. The new species Erysiphe alnicola, E. deutziana, E. cornigena, E. lentaginis, and E. sambucina are described, the new combinations E. lauracearum, E. passiflorae, and E. sambucicola are introduced, and the new name E. santali is proposed.
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Cytological studies reveal high variation in ascospore number and shape and conidia produced directly from ascospores in Morchella galilaea.

Du, X.H., et al., 2023. Cytological studies reveal high variation in ascospore number and shape and conidia produced directly from ascospores in Morchella galilaea. Frontiers in Microbiology. Publisher's VersionAbstract
Spores are important as dispersal and survival propagules in fungi. In this study we investigated the variation in number, shape, size and germination mode of ascospores in Morchella galilaea, the only species of the genus Morchella known to fruit in the autumn. Based on the observation of five samples, we first discovered significant variation in the shape and size of ascospores in Morchella. One to sixteen ascospores were found in the asci. Ascospore size correlated negatively with ascospore number, but positively with ascus size, and ascus size was positively correlated with ascospore number. We noted that ascospores, both from fresh collections and dried specimens, germinated terminally or laterally either by extended germ tubes, or via the production of conidia that were formed directly from ascospores at one, two or multiple sites. The direct formation of conidia from ascospores takes place within asci or after ascospores are discharged. Using laser confocal microscopy, we recorded the number of nuclei in ascospores and in conidia produced from ascospores. In most ascospores of M. galilaea, several nuclei were observed, as is typical of species of Morchella. However, nuclear number varied from zero to around 20 in this species, and larger ascospores harbored more nuclei. One to six nuclei were present in the conidia. Nuclear migration from ascospores to conidia was observed. Conidia forming directly from ascospores has been observed in few species of Pezizomycetes; this is the first report of the phenomenon in Morchella species. Morphological and molecular data show that conidial formation from ascospores is not found in all the specimens of this species and, hence, is not an informative taxonomic character in M. galilaea. Our data suggest that conidia produced from ascospores and successive mitosis within the ascus may contribute to asci with more than eight spores. The absence of mitosis and/or nuclear degeneration, as well as cytokinesis defect, likely results in asci with fewer than eight ascospores. This study provides new insights into the poorly understood life cycle of Morchella species and more broadly improves knowledge of conidia formation and reproductive strategies in Pezizomycetes.
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The Erysiphe alphitoides complex (powdery mildews) – unravelling the phylogeny and taxonomy of an intricate assemblage of species

Bradshaw, M., et al., 2023. The Erysiphe alphitoides complex (powdery mildews) – unravelling the phylogeny and taxonomy of an intricate assemblage of species. New Zealand Journal of Botany . Publisher's VersionAbstract

Powdery mildews on oaks, caused by Erysiphe species, have serious ecological consequences on a range of Quercus hosts. In addition to Erysiphe quercicolaE. alphitoides is one of the most common and widespread species of Erysiphe having a wide host range among oak species, and a clear economic significance in applied ecology, forestry, and forest pathology. There are many publications addressing these important tree pathogens. Previous phylogenetic examinations have shown that E. alphitoides refers to a complicated species assemblage with insufficient taxonomic resolution in ITS + 28S analyses; the associated sequences form an insufficiently resolved species complex. The majority of species within the E. alphitoides complex cannot be unequivocally identified based solely on ITS + 28S analyses. Most of the additional species of the E. alphitoides complex are distributed in Asia, with a concentration in Japan. The question posed is whether there is a single widespread powdery mildew species, E. alphitoides, or an assemblage of closely allied species. To answer this question, specimens of related recognized species, particularly those from Japan, have been subjected to phylogenetic multilocus examinations, including CAMGAPDHGS, ITS + 28S, RPB2, and TUB sequences. An analysis of the concatenated sequences resulted in the confirmation of several distinct species. These species form highly supported clades that include E. alphitoidesE. aucubaeE. euonymicolaE. ipomoeaeE. menispermi var. dahuricaE. orixaeE. pseudoloniceraeE. sinomenii and E. wallrothiiErysiphe akebiae as well as the relationship between Japanese and North American collections requires further examinations.

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