The fungi of California's xeric oak habitats and nearby areas of the Pacific states of American West have long been understudied due to their irregular fruiting patterns, low expected yields, and the challenges these pose for planning field work. This study is based on the authors' extensive research into this natural environment. This article is the first in a series of installments that will describe more than 24 new members of Cortinariaceae from this habitat. Here we describe nine new species in the genus Calonarius-Ca. ambrosius, Ca. ostentatus, Ca. laudabilis, Ca. pretiosus, Ca. praestabilis, Ca. eminens, Ca. involutus, Ca. inopinatus, and Ca. polychromus, all associated with Quercus, and in some cases with Notholithocarpus densiflorus species. Some species presented here appear to be limited to the xeric zone, whereas others are widespread but more common within it. A brief history of the study of Cortinarius s.l. in California is also presented.

ABSTRACT Several species of the genus Gyromitra—commonly known as “false morels”—are traditionally consumed in different parts of the world, despite their potential toxicity due to the presence of monomethylhydrazine, a volatile compound. In some taxa, monomethylhydrazine content has been linked to environmental factors such as elevation, potentially influencing toxicity levels. In southern South America, ethnomycological records indicate that Gyromitra species are collected and consumed by indigenous communities. However, their taxonomy and toxicological profile remain poorly understood. In this study, we examined the phylogenetic identity and hydrazine content of Gyromitra specimens collected across a Patagonian elevation gradient. Molecular analyses based on nuclear internal transcribed spacer, large subunit, and elongation factor-1 alpha sequences confirmed the identity of all specimens as G. antarctica. Hydrazine content was quantified in 82 fresh samples collected between 300 and 800 m above sea level, revealing a significant negative correlation between elevation and toxin concentration (ρ = −0.79, P < 0.001). Two boiling treatments —10 min without water exchange, and 2 × 5 min with water exchange—reduced hydrazine levels by 97% and 94%, respectively. However, residual toxins were detected in the boiling water of both treatments. These findings provide new insights into the taxonomy and elevation-dependent toxicity of Gyromitra in the Southern Hemisphere. They also underscore the risks associated with the consumption of wild false morels and highlight the importance of informed and adequate culinary practices to reduce toxicity.

ABSTRACT Four new species of the genus Phaeocollybia (Hymenogastraceae, Agaricales) from Yunnan Province, southwestern China, namely, P. ochrilata, P. conicogregaria, P. profundirhizoidea, and P. purpureorosea, are described and illustrated based on morphological data and multilocus phylogenetic analyses from DNA sequences of the internal transcribed spacer (ITS) and the second largest subunit of RNA polymerase II (RPB2). Our phylogenetic analyses revealed that the four new species belong to P. subgen. Phaeocollybia. Color photos of fresh basidiomata, line drawings of microscopic features, and their comparisons with allied taxa are presented.

ABSTRACT Sorochytrium milnesiophthora is a necrotrophic pathogen of tardigrades and a member of the poorly sampled zoosporic phylum Blastocladiomycota. First described in 1985, it was previously known only from the type locality, the Appalachian Mountains of North Carolina, USA, and had not been documented in over 35 years. We rediscovered S. milnesiophthora in a lichen sample from Finland, cultured the fungus, and sequenced its genome. Ribosomal DNA and phylogenomic analyses placed S. milnesiophthora in the Blastocladiales as sister to the rest of the order. The Sorochytriaceae clade also included environmental sequences from Brazil, Italy, Poland, and Sweden, indicating a wide distribution and substantial unexplored biodiversity of Sorochytrium-like fungi. To our surprise, S. milnesiophthora was found to have an exceptionally large nuclear rDNA ITS1-5.8S-ITS2 (internal transcribed spacer [ITS]) region of approximately 5500 bp, the largest known in Fungi. This extraordinary ITS length may represent an adaptation to desiccation by slowing ribosome biogenesis. Further studies should examine how S. milnesiophthora infection intersects with tardigrade cryptobiosis and whether the fungus can also survive the extreme conditions for which its host is famous. Deposition of S. milnesiophthora in the Collection of Zoosporic Eufungi at University of Michigan ensures its long-term availability for future investigations.

ABSTRACT Mexican dry ecosystems, mainly tropical dry forests, harbor a vast and largely undiscovered fungal diversity. The stalked puffballs of Tulostoma (Basidiomycota: Agaricales) are highly cryptic, necessitating detailed and expert examination to accurately distinguish the species. A revision of the MEXU national fungarium and recent sampled specimens revealed fruiting bodies that did not match any known species. This led us to propose T. parvirufula and T. chamelensis as new species. Six collections were morphologically characterized using two microscopy techniques: light and scanning electron microscopy. DNA was extracted, the nuc rDNA internal transcribed spacer region ITS15.8S-ITS2 (ITS barcode) and D1–D2 domains of the nuc 28S rDNA were amplified and sequenced. Phylogenetic analyses were conducted using maximum likelihood and Bayesian inference methods, incorporating sequences from previous studies. Tulostoma chamelensis is distinguished by its medium-sized spore sac, a hyphal exoperidium that persists at the base, a tubular ostiole, and verrucose to subreticulate basidiospores. Tulostoma parvirufula is characterized by minute spore sacs, a tubular ostiole, a hyphal exoperidium, a reddish-brown endoperidium, and spiny basidiospores. Phylogenetic analyses place both species in a sister clade to clade 11, alongside other taxa with tubular ostioles and coarsely ornamented basidiospores, further expanding our understanding of the Tulostoma genus and its diversity in dry ecosystems.

ABSTRACT The genus Nucleophaga comprises poorly studied intranuclear parasites that infect amoebae. Currently classified within the phylum Rozellomycota, this genus belongs among numerous lineages with unresolved taxonomic positions, primarily identified through metagenomic studies. Three species of Nucleophaga were described at the morphological and molecular levels—N. amoebae, N. terricolae, and N. striatae, all isolated in Europe. Here, we report the discovery of a fourth species of the genus, isolated from the Far East of Russia, infecting nuclei of Thecamoeba sp. A detailed light microscopic study revealed several remarkable morphological features of this organism. For the first time, the division of Nucleophaga plasmodium was illustrated. Experimental infections demonstrated that Thecamoeba quadrilineata and T. foliovenanda can support the development of the parasite, whereas Nucleophaga showed abnormal development in T. onigiri and was unable to survive in T. vumurta. Phylogenetic analysis, based on the nuc 18S rRNA gene sequences, placed the new isolate as a distinct lineage within the genus Nucleophaga. Based on its molecular characteristics, the studied isolate was described as a new species, Nucleophaga amutiana.

ABSTRACT During a survey of fungi associated with Cyperaceae plants in northern and northwestern Iran, three previously undescribed species belonging to Alternaria section Nimbya were identified and characterized. These new species, namely, Alternaria azarbaijanica, A. caspica, and A. eleocharidis, spp. nov. were examined using a combination of morphological traits, cultural features, and molecular data. Remarkably, all three species produced both sexual and asexual morphs under laboratory conditions, providing rare insights into reproductive modes within Alternaria, where sexual morphs are rarely observed. Phylogenetic analyses based on five gene regions (ITS-rDNA, GAPDH, TEF1, RPB2, and Alt a 1) clarified their evolutionary relationships and supported species delimitation. Phylogenetic trees constructed using maximum likelihood, maximum parsimony, and Bayesian inference consistently resolved each species as a distinct monophyletic lineage within Alternaria section Nimbya. These findings reveal previously unrecognized Alternaria diversity on Cyperaceae hosts and underscore the value of combining morphological observations with multilocus phylogenetic approaches to resolve taxonomic complexities in Alternaria.

ABSTRACT The new species Stereophlebia arizonica from southern Arizona is described and illustrated. Although similar to S. pendula, a widely distributed taxon in North America, molecular phylogenetic analyses and morphological evidence show that they are distinct, sister species. Phylogenetic analyses place Stereophlebia in a clade with Gelatinofungus within the Phanerochaetaceae (Polyporales). Critical morphological features of Gelatinofungus not reported earlier are presented, and G. betulinus is determined to be a later synonym of S. pendula.

ABSTRACT This study presents a comprehensive phylogenetic analysis of the genus Meripilus and its allied genera Henningsia and Physisporinus within the Meripilaceae family, in the broader context of the residual polyporoid clade. The three genera are morphologically similar and characterized by resupinate to pileate basidiomes that harden and often darken upon drying, a monomitic hyphal structure, simple-septate generative hyphae, and globose to ovoid basidiospores, with variable presence of cystidia. Species in Henningsia and Meripilus, in turn, present gloeopleurous hyphae in the context and large, multipileate basidiomes. Recent studies have indicated that Physisporinus, as currently defined, is not monophyletic, with Meripilus nested within it. Phylogenetic analysis based on four molecular markers confirmed the paraphyletic nature of Physisporinus, with Meripilus and Henningsia both nested within it. Morphological examinations of specimens collected in South America, along with revisions of type specimens, show that this segregation is not natural and causes nomenclatural problems. We propose to transfer all species currently placed in Physisporinus into Meripilus, thereby preventing the division of the genus into morphologically indistinguishable groups. As a result of this reclassification, we propose 35 new combinations in Meripilus and describe three new species from South America.

ABSTRACT Despite being present in many North American forest understories, the ectomycorrhizal (ECM) fungal communities associated with Corylus shrubs have received no prior study. To address this knowledge gap, we characterized the ECM fungal communities on roots of Corylus shrubs as well as co-occurring Quercus and Pinus trees in Minnesota, USA. ECM-colonized root tips from pairs of Corylus shrubs and four ECM tree species, Quercus macrocarpa, Quercus ellipsoidalis, Pinus strobus, and Pinus resinosa, growing in close proximity (<1 m), were sampled at the Cedar Creek Ecosystem Science Reserve. ECM fungal communities were assessed using high-throughput sequencing of the ITS2 region. ECM fungal operational taxonomic unit (OTU) richness was equivalent among the two Quercus species and their associated Corylus shrubs, but significantly higher on P. strobus–associated Corylus shrubs compared with P. strobus, P. resinosa, and P. resinosa–associated Corylus shrubs. ECM fungal community composition on Corylus shrubs largely mirrored that on each of the Quercus and Pinus species, although the two Pinus communities were significantly different from each other. Further, the same ECM fungal OTUs were commonly encountered on paired Corylus–tree host samples, suggesting a high potential for co-colonization by the same fungal individuals. Collectively, these results support the growing consensus that woody understory plants often associate with similar ECM fungal communities as co-occurring tree hosts regardless of phylogenetic relatedness.