Revision of pyrophilous taxa of Pholiota described from North America reveals four species—P. brunnescens, P. castanea, P. highlandensis, and P. molesta

Fire as a driver of fungal diversity - A synthesis of current knowledge

Fires occur in most terrestrial ecosystems where they drive changes in the traits, composition, and diversity of fungal communities. Fires range from rare, stand-replacing wildfires to frequent, prescribed fires used to mimic natural fire regimes. Fire regime factors, including burn severity, fire intensity, and timing, vary widely and likely determine how fungi respond to fires. Despite the importance of fungi to post-fire plant communities and ecosystem functioning, attempts to identify common fungal responses and their major drivers are lacking. This synthesis addresses this knowledge gap and ranges from fire adaptations of specific fungi to succession and assembly fungal communities as they respond to spatially heterogenous burning within the landscape. Fires impact fungi directly and indirectly through their effects on fungal survival, substrate and habitat modifications, changes in environmental conditions, and/or physiological responses of the hosts with which fungi interact. Some specific pyrophilous, or "fire-loving," fungi often appear after fire. Our synthesis explores whether such taxa can be considered cosmopolitan, and whether they are truly fire-adapted or simply opportunists adapted to rapidly occupy substrates and habitats made available by fires. We also discuss the possible inoculum sources of post-fire fungi and explore existing conceptual models and ecological frameworks that may be useful in generalizing fungal fire responses. We conclude with identifying research gaps and areas that may best transform the current knowledge and understanding of fungal responses to fire.

Revisiting Hebeloma (Hymenogastraceae, Agaricales) in Japan: four species recombined into other genera but three new species discovered

Here, we present the results of studies of Japanese Hebeloma collections. The four species described by Imai as Hebeloma (H. fimicola, H. helvolescens, H. humosum, and H. tomoeae) are not from the genus Hebeloma, but are members of Agrocybe, Homophron, or Pholiota. Recombinations are made. Hebelomacrustuliniforme f. microspermum, described by Hongo, is a synonym of H. nanum. Three species of Hebeloma are described as new to science, all currently known only from Japan. Two of these species, H. asperosporum and H. cinnamomeum, are members of H. sect. Denudata while the third species H. citrisporum belongs to H. sect. Velutipes. Japanese records of H. cavipes, H. eburneum, H. hygrophilum, H. subtortum, and H. velutipes are validated. In total, fifteen species of Hebeloma are confirmed from Japan; this is compared with previous checklists.

96 North American taxa sorted - Peck's Hebeloma revisited

Charles Horton Peck described some 2700 species of North American fungi in the 19th and early 20th centuries. Among these were 31 species that he described as Hebeloma or that later authors recombined into Hebeloma. These 31 taxa have been analyzed morphologically and molecularly, as far as possible. For six of these species, lectotypes are designated. For twelve species, ITS sequences (some partial) were generated. Thirteen of the species analyzed are Hebeloma, as the genus is delimited today. Of these 13, nine are regarded as 'current', i.e. are names that should be accepted and used. Of the remaining four, three are synonymized with earlier Peck species and one with the generic type H. mesophaeum. Numerous Hebeloma species described from America are synonymized with some of Peck's species, such as H. albidulum, H. album, H. colvinii, H. excedens, H. palustre, H. sordidulum, and H. velatum; Peck's H. album, H. palustre, and H. velatum are earlier names for H. fragilipes, H. clavulipes, and H. dunense, respectively. All three names were in current use and described from Europe. The 18 species that are not Hebeloma belong to a range of genera: Agrocybe, Hemistropharia, Inocybe, Inosperma, Naucoria, and Pholiota; three species that were not previously recombined into their respective genera are here recombined and one species, Hebeloma commune is synonymized with Pholiota lenta. Two taxa, that are not Hebeloma, remain unresolved. Sixty later Hebeloma taxa described from North America are revised and synonymized with Peck species and seven with H. mesophaeum, 36 of these supported by ITS (some partial) sequence data. Updates on two species, H. petrakii and H. remyi, from Europe, are also given, and a lectotype and epitype selected for the latter.

Lifecycle of Pyrenopeziza protrusa (Helotiales, Dermateaceae sensu lato) in Magnolia obovata revealed by field observation and molecular quantification

Fungi exhibit saprophytic, parasitic, and symbiotic lifestyles, and flexibly switching between them by the environmental changes and host conditions. However, only a few studies have elucidated the detailed changes in fungal DNA or morphology, including the formation of reproductive structures along with lifestyle switching. We hypothesized that Pyrenopeziza protrusa, which occurs abundantly and specifically on Magnolia obovata as a saprophyte, is also associated with living hosts and switches its lifestyles as part of its lifecycle. To elucidate this hypothesis, we periodically sampled the fresh/fallen leaves of M. obovata to observe the seasonal occurrence of reproductive structures for the isolation and detection/quantification of P. protrusa DNA with newly developed species-specific primers. The isolation frequency and amount of P. protrusa DNA drastically increased in the fresh leaves just before defoliation in autumn, but remained high in fallen leaves from autumn to spring. Abundant production of conidiomata and apothecia was also observed in the fallen leaves with increasing DNA content. These results clarified a large part of the lifecycle of P. protrusa, suggesting that the lifestyle is switched from symbiotic to saprophytic stage by significantly increasing the amount of DNA in response to host conditions according to the seasonal variations.

In Vitro Observations of the Interactions between Pholiota carbonaria and Polytrichum commune and Its Potential Environmental Relevance

Wildfires play a critical role in maintaining biodiversity and shaping ecosystem structure in fire-prone regions, and successional patterns involving numerous plant and fungal species in post-fire events have been elucidated. Evidence is growing to support the idea that some post-fire fungi can form endophytic/endolichenic relationships with plants and lichens. However, no direct observations of fire-associated fungal-moss interactions have been visualized to date. Therefore, physical interactions between a post-fire fungus, Pholiota carbonaria, and a moss, Polytrichum commune, were visually examined under laboratory conditions. Fungal appressoria were visualized on germinating spores and living protonemata within two weeks of inoculation in most growth chambers. Appressoria were pigmented, reddish gold to braun, and with a penetration peg. Pigmented, reddish gold to braun fungal hyphae were associated with living tissue, and numerous mature rhizoids contained fungal hyphae at six months. Inter-rhizoidal hyphae were pigmented and reddish gold to braun, but no structures were visualized on mature gametophyte leaf or stem tissues. Based on our visual evidence and previous work, we provide additional support for P. carbonaria having multiple strategies in how it obtains nutrients from the environment, and provide the first visual documentation of these structures in vitro.

Using aggregated field collection data and the novel r package fungarium to investigate fungal fire association

Understanding which fungi exhibit certain ecological traits, such as habitat, host, or substrate associations, and knowing how these traits change across space and time can provide invaluable insight into the roles fungi play in their respective ecosystems. Archived sporocarp data, such as the collection and observation records accessible through the Mycology Collections Portal (MyCoPortal), are well suited for trait investigations, since these records circumvent the need for field work, are geographically and temporally diverse, and often have detailed and trait-relevant environmental metadata. However, there are inefficiencies and inadequacies in the MyCoPortal online interface that affect data set generation and trait searching, and many of the available records have outdated or misspelled taxon names as well as misspelled location names. Thus, we created the r package fungarium, which enables the efficient download of complete MyCoPortal data sets from within the R environment, enhances the identification of trait-relevant records, confirms or updates taxon names while also accounting for spelling errors, and fixes misspelled location names. Utilizing this package and MyCoPortal data, we demonstrated methods for analyzing taxonomic, geographic, and temporal patterns in ecological traits, using fire association as an example. We found that fire association, which was quantified via fire-associated enrichment factors (fire-associated records/total records), differed substantially between taxa, and these differences were qualitatively supported by existing literature, as hypothesized. Sampling bias within the MyCoPortal data and limitations of the burned acreage data set used (i.e., Monitoring Trends in Burn Severity) were identified as confounding factors in our geographic and temporal analyses, as evidenced by the unexpected lack of correlation between fire association and burned acreage on county and year bases. However, both confounding factors likely depend on the trait analyzed and external data set used. Overall, the fungarium package and associated methods presented here effectively enable the use of archived sporocarp data for future ecological trait studies.

Taxonomic Study of the Genus Pholiota (Strophariaceae, Basidiomycota) in Korea

The genus Pholiota (Strophariaceae, Basidiomycota) is made up of wood-rotting saprotrophic mushrooms characterized by a yellow or brown pileus with scales and/or slimy, and by a brownish smooth spore with a germ pore. However, these features are not enough to distinguish its species, or separate the genus Pholiota from other brown-spored wood-rotting genera such as Hypholoma and Stropharia. Although internal transcribed spacer (ITS) sequence-based identification has improved identification accuracy for species of Pholiota, most Pholiota species in Korea are reported based on morphological features. To evaluate the taxonomy of Pholiota species, we investigated 62 specimens collected from 1999 to 2019 in Korea using ITS sequence analysis and morphological observation. Twelve of the 16 recorded Pholiota species in Korea were identified. While eight species were clearly separated, the ITS analysis did not distinguish three in the Pholiota adiposa complex. Therefore, further investigation is required to distinguish these three species. ITS sequences deposited in GenBank confirm that P. highlandensis exists in Korea. The presence of the other four Pholiota species could not be confirmed through specimens or sequence information in GenBank. A taxonomic key and the ITS sequence data for Korean Pholiota species are included and can be good baselines for further research on Pholiota taxonomy and diversity.

Pyrophilous fungi detected after wildfires in the Great Smoky Mountains National Park expand known species ranges and biodiversity estimates

Following a late fall wildfire in 2016 in the Great Smoky Mountains National Park, pyrophilous fungi in burn zones were documented over a 2-y period with respect to burn severity and phenology. Nuc rDNA internal transcribed spacer (ITS1-5.8S-ITS2 = ITS) barcodes were obtained to confirm morphological evaluations. Forty-one taxa of Ascomycota and Basidiomycota were identified from burn sites and categorized as fruiting only in response to fire or fruiting enhanced by fire. Twenty-two species of Pezizales (Ascomycota) were among the earliest to form ascomata in severe burn zones, only one of which had previously been documented in the Great Smoky Mountains National Park. Nineteen species of Basidiomycota, primarily Agaricales, were also documented. Among these, only five species (Coprinellus angulatus, Gymnopilus decipiens, Lyophyllum anthracophilum, Pholiota carbonicola, and Psathyrella pennata) were considered to be obligate pyrophilous taxa, but fruiting of two additional taxa (Hygrocybe conica and Mycena galericulata) was clearly enhanced by fire. Laccaria trichodermophora was an early colonizer of severe burn sites and persisted through the winter of 2017 and into spring and summer of 2018, often appearing in close association with Pinus pungens seedlings. Fruiting of pyrophilous fungi peaked 4-6 mo post fire then diminished, but some continued to fruit up to 2.5 y after the fire. In all, a total of 27 previously unrecorded taxa were added to the All Taxa Biodiversity Inventory (ATBI) database (~0.9%). Most pyrophilous fungi identified in this study are either cosmopolitan or have a Northern Hemisphere distribution, but cryptic endemic lineages were detected in Anthracobia and Sphaerosporella. One new combination, Hygrocybe spadicea var. spadicea f. odora, is proposed.

Secret lifestyles of pyrophilous fungi in the genus Sphaerosporella

PREMISE

Pyrophilous fungi form aboveground fruiting structures (ascocarps) following wildfires, but their ecology, natural history, and life cycles in the absence of wildfires are largely unknown. Sphaerosporella is considered to be pyrophilous. This study explores Sphaerosporella ascocarp appearance following a rare 2016 wildfire in the Great Smoky Mountains National Park (GSMNP), compares the timing of ascocarp formation with recovery of Sphaerosporella DNA sequences in soils, and explores the association of Sphaerosporella with post-fire Table Mountain pine (Pinus pungens) seedlings.

METHODS

Burned sites in the GSMNP were surveyed for pyrophilous fungal ascocarps over 2 years. Ascocarps, mycorrhizae, and endophyte cultures were evaluated morphologically and by Sanger sequencing of the nuclear ribosomal ITS gene region (fungal barcode; Schoch et al., 2012). DNA from soil cores was subjected to Illumina sequencing.

RESULTS

The timing and location of post-fire Sphaerosporella ascocarp formation was correlated with recovery of Sphaerosporella DNA sequences in soils. Genetic markers (fungal barcode) of Sphaerosporella were also recovered from mycorrhizal root tips and endophyte cultures from seedlings of Pinus pungens.

CONCLUSIONS

This study demonstrates that Sphaerosporella species, in the absence of fire, are biotrophic, forming both mycorrhizal and endophytic associations with developing Pinus pungens seedlings and may persist in nature in the absence of wildfire as a conifer symbiont. We speculate that Sphaerosporella may fruit only after the host plant is damaged or destroyed and that after wildfires, deep roots, needle endophytes, or heat-resistant spores could serve as a source of soil mycelium.