Entomophthoralean fungi overwinter with the bird cherry-oat aphid on bird cherry trees.

In Scandinavia, the bird cherry-oat aphid Rhopalosiphum padi overwinter as eggs on the bird cherry tree Prunus padus. Branches of P. padus were collected at the late February / early March from 17 locations in Norway over a three-year period. We found 3599 overwintering aphid eggs, 59.5% of which were dead. Further, a total of 879 overwintering fungus-killed cadavers were observed. These cadavers were found close to bud axils, where overwintering eggs were also usually attached. Cadavers were infected with either Zoophthora cf. aphidis or Entomophthora planchoniana. All the fungal-killed cadavers were filled with overwintering structures of Z. cf. aphidis (as resting spores) or E. planchoniana (as modified hyphal bodies). We found a significant negative correlation between eggs and cadavers per branch. However, both numbers of eggs and cadavers varied greatly between years and among tree locations. This is the first report of E. planchoniana overwintering in R. padi cadavers as modified hyphal bodies. We discuss whether P. padus may act as an inoculum reservoir for fungi infecting aphids in cereals in spring.

Parasite Spillover from Domestic Sheep to Wild Reindeer-The Role of Salt Licks.

Attraction sites are important for environmental pathogen transmission and spillover. Yet, their role in wildlife disease dynamics is often poorly substantiated. Herein, we study the role of salt licks as potential attraction sites for the spillover of gastrointestinal parasites from domestic sheep to wild reindeer. Eggs from the introduced sheep nematode Nematodirus battus were found in faecal samples of both species, suggestive of spillover. DNA metabarcoding of soil, collected at salt licks, revealed that N. battus, in addition to Teladorsagia circumcincta, were the most frequently occurring parasitic nematodes, with a significantly higher prevalence of nematodal DNA in salt lick soil compared to soil from control sites nearby. The finding of similar DNA haplotypes of N. battus in sheep, reindeer, and salt lick soil supports the hypothesis of spillover to reindeer via salt licks. More detailed investigation of the genetic diversity of N. battus across these hosts is needed to draw firm conclusions. Infection with these sheep nematodes could potentially explain a recently observed decline in the calf recruitment rate of the Knutshø reindeer herd. This study also supports the hypothesized role of artificial salt licks as hot spots for the transmission of environmentally persistent pathogens and illustrates the importance of knowledge about such attraction points in the study of disease in free-roaming animals.

Faecal metabarcoding provides improved detection and taxonomic resolution for non-invasive monitoring of gastrointestinal nematode parasites in wild moose populations.

BACKGROUND: Although wild ungulate populations are heavily monitored throughout Europe, we understand little of how parasites affect population dynamics, and there is no systematic, long-term monitoring of parasite diversity and parasite loads. Such monitoring is in part hampered by a lack of time- and cost-effective assay methodologies with high sensitivity and good taxonomic resolution. DNA metabarcoding has been successfully used to characterize the parasitic nemabiome with high taxonomic resolution in a variety of wild and domestic hosts. However, in order to implement this technique in large-scale, potentially non-invasive monitoring of gastrointestinal parasitic nematodes (GIN), protocol optimization is required to maximize biodiversity detection, whilst maintaining time- and cost-effectiveness. METHODS: Faecal samples were collected from a wild moose population and GIN communities were characterized and quantified using both parasitological techniques (egg and larva counting) and DNA metabarcoding of the ITS2 region of rDNA. Three different isolation methods were compared that differed in the volume of starting material and cell lysis method. RESULTS: Similar nematode faunas were recovered from all samples using both parasitological and metabarcoding methods, and the approaches were largely congruent. However, metabarcoding assays showed better taxonomic resolution and slightly higher sensitivity than egg and larvae counts. The metabarcoding was not strictly quantitative, but the proportion of target nematode sequences recovered was correlated with the parasitologically determined parasite load. Species detection rates in the metabarcoding assays were maximized using a DNA isolation method that included mechanical cell disruption and maximized the starting material volume. CONCLUSIONS: DNA metabarcoding is a promising technique for the non-invasive, large-scale monitoring of parasitic GINs in wild ungulate populations, owing to its high taxonomic resolution, increased assay sensitivity, and time- and cost-effectiveness. Although metabarcoding is not a strictly quantitative method, it may nonetheless be possible to create a management- and conservation-relevant index for the host parasite load from this data. To optimize the detection rates and time- and cost-effectiveness of metabarcoding assays, we recommend choosing a DNA isolation method that involves mechanical cell disruption and maximizes the starting material volume.

Experimental warming increases fungal alpha diversity in an oligotrophic maritime Antarctic soil.

The climate of maritime Antarctica has altered since the 1950s. However, the effects of increased temperature, precipitation and organic carbon and nitrogen availability on the fungal communities inhabiting the barren and oligotrophic fellfield soils that are widespread across the region are poorly understood. Here, we test how warming with open top chambers (OTCs), irrigation and the organic substrates glucose, glycine and tryptone soy broth (TSB) influence a fungal community inhabiting an oligotrophic maritime Antarctic fellfield soil. In contrast with studies in vegetated soils at lower latitudes, OTCs increased fungal community alpha diversity (Simpson's index and evenness) by 102-142% in unamended soil after 5 years. Conversely, OTCs had few effects on diversity in substrate-amended soils, with their only main effects, in glycine-amended soils, being attributable to an abundance of Pseudogymnoascus. The substrates reduced alpha and beta diversity metrics by 18-63%, altered community composition and elevated soil fungal DNA concentrations by 1-2 orders of magnitude after 5 years. In glycine-amended soil, OTCs decreased DNA concentrations by 57% and increased the relative abundance of the yeast Vishniacozyma by 45-fold. The relative abundance of the yeast Gelidatrema declined by 78% in chambered soil and increased by 1.9-fold in irrigated soil. Fungal DNA concentrations were also halved by irrigation in TSB-amended soils. In support of regional- and continental-scale studies across climatic gradients, the observations indicate that soil fungal alpha diversity in maritime Antarctica will increase as the region warms, but suggest that the accumulation of organic carbon and nitrogen compounds in fellfield soils arising from expanding plant populations are likely, in time, to attenuate the positive effects of warming on diversity.

Habitat Protection Approaches Facilitate Conservation of Overlooked Fungal Diversity - A Case Study From the Norwegian Coastal Heathland System.

European coastal heathlands are distinct ecosystems shaped by land use tradition and they have experienced an 80% area reduction from their historical maximum. These mosaics of mires and wind exposed patches have ericaceous shrub dominated vegetation, and soils within coastal heathlands are characterized by low pH and high levels of recalcitrant debris. Using a culture-based approach with molecular identification of isolates, we characterized root-associated fungal communities of six ericaceous species in eight heathland localities along Norway's western coast. Site-level alpha diversity ranged from 21-38 OTUs, while the total estimated gamma diversity for culturable heathland root fungi was 190-231 OTUs. Most species recovered are previously reported at low abundance in Norway, suggesting the biodiversity in this community is underreported, rather than novel for science. The fungi recovered were primarily Ascomycota, specifically endophytic Phialocephala, and Pezicula, and no host specificity was observed in the communities. The fungal communities exhibited high turnover and low nestedness, both between ericaceous hosts and across heathland sites. We observed no spatial patterns in fungal betadiversity, and this heterogeneity may be a product of the unique historic land use practices at each locality creating a distinct mycofloral "fingerprint". Robust diversity estimates will be key for managing fungal biodiversity in coastal heathlands. Our results indicate that sampling schemes that maximize the number of host plants sampled per site, rather than the number of cultures per plant yield improved alpha diversity estimates. Similarly, gamma diversity estimates are improved by maximizing the total number of localities sampled, rather than increasing the number of plants sampled per locality. We argue that while the current protected status of coastal heathland habitats and restoration efforts have knock-on effects for the conservation of fungal biodiversity, fungi have a vital functional role in the ecosystem and holistic conservation plans that consider fungal biodiversity would be beneficial.

Multiple thresholds and trajectories of microbial biodiversity predicted across browning gradients by neural networks and decision tree learning.

Ecological association studies often assume monotonicity such as between biodiversity and environmental properties although there is growing evidence that nonmonotonic relations dominate in nature. Here, we apply machine-learning algorithms to reveal the nonmonotonic association between microbial diversity and an anthropogenic-induced large-scale change, the browning of freshwaters, along a longitudinal gradient covering 70 boreal lakes in Scandinavia. Measures of bacterial richness and evenness (alpha-diversity) showed nonmonotonic trends in relation to environmental gradients, peaking at intermediate levels of browning. Depending on the statistical methods, variables indicative for browning could explain 5% of the variance in bacterial community composition (beta-diversity) when applying standard methods assuming monotonic relations and up to 45% with machine-learning methods taking non-monotonicity into account. This non-monotonicity observed at the community level was explained by the complex interchangeable nature of individual taxa responses as shown by a high degree of nonmonotonic responses of individual bacterial sequence variants to browning. Furthermore, the nonmonotonic models provide the position of thresholds and predict alternative bacterial diversity trajectories in boreal freshwater as a result of ongoing climate and land-use changes, which in turn will affect entire ecosystem metabolism and likely greenhouse gas production.

Regional Diversity of Maritime Antarctic Soil Fungi and Predicted Responses of Guilds and Growth Forms to Climate Change.

We report a metabarcoding study documenting the fungal taxa in 29 barren fellfield soils sampled from along a 1,650 km transect encompassing almost the entire maritime Antarctic (60-72°S) and the environmental factors structuring the richness, relative abundance, and taxonomic composition of three guilds and growth forms. The richness of the lichenised fungal guild, which accounted for 19% of the total fungal community, was positively associated with mean annual surface air temperature (MASAT), with an increase of 1.7 operational taxonomic units (OTUs) of lichenised fungi per degree Celsius rise in air temperature. Soil Mn concentration, MASAT, C:N ratio, and pH value determined the taxonomic composition of the lichenised guild, and the relative abundance of the guild was best predicted by soil Mn concentration. There was a 3% decrease in the relative abundance of the saprotrophic fungal guild in the total community for each degree Celsius rise in air temperature, and the OTU richness of the guild, which accounted for 39% of the community, was negatively associated with Mn concentration. The taxonomic composition of the saprotrophic guild varied with MASAT, pH value, and Mn, NH4 +-N, and SO4 2- concentrations. The richness of the yeast community, which comprised 3% of the total fungal community, was positively associated with soil K concentration, with its composition being determined by C:N ratio. In contrast with a similar study in the Arctic, the relative abundance and richness of lichenised fungi declined between 60°S and 69°S, with those of saprotrophic Agaricales also declining sharply in soils beyond 63°S. Basidiomycota, which accounted for 4% of reads, were much less frequent than in vegetated soils at lower latitudes, with the Ascomycota (70% of reads) being the dominant phylum. We conclude that the richness, relative abundance, and taxonomic composition of guilds and growth forms of maritime Antarctic soil fungi are influenced by air temperature and edaphic factors, with implications for the soils of the region as its climate changes during the 21st century.

Fine-scale diversity patterns in belowground microbial communities are consistent across kingdoms.

The belowground environment is heterogeneous and complex at fine spatial scales. Physical structures, biotic components and abiotic conditions create a patchwork mosaic of potential niches for microbes. Questions remain about mechanisms and patterns of community assembly belowground, including: Do fungal and bacterial communities assemble differently? How do microbes reach the roots of host plants? Within a 4 m2 plot in alpine vegetation, high throughput sequencing of the 16S (bacteria) and ITS1 (fungal) ribosomal RNA genes was used to characterise microbial community composition in roots and adjacent soil of a viviparous host plant (Bistorta vivipara). At fine spatial scales, beta-diversity patterns in belowground bacterial and fungal communities were consistent, although compositional change was greater in bacteria than fungi. Spatial structure and distance-decay relationships were also similar for bacteria and fungi, with significant spatial structure detected at <50 cm among root- but not soil-associated microbes. Recruitment of root microbes from the soil community appeared limited at this sampling and sequencing depth. Possible explanations for this include recruitment from low-abundance populations of soil microbes, active recruitment from neighbouring plants and/or vertical transmission of symbionts to new clones, suggesting varied methods of microbial community assembly for viviparous plants. Our results suggest that even at relatively small spatial scales, deterministic processes play a significant role in belowground microbial community structure and assembly.

Host and tissue variations overshadow the response of boreal moss-associated fungal communities to increased nitrogen load.

Human activity has more than doubled the amount of nitrogen entering the global nitrogen cycle, and the boreal forest biome is a nitrogen-limited ecosystem sensitive to nitrogen load perturbation. Although bryophyte-associated microbes contribute significantly to boreal forest ecosystem function, particularly in carbon and nitrogen cycling, little is known about their responses to anthropogenic global change. Amplicon pyrosequencing of the ITS2 region of rDNA was used to investigate how fungal communities associated with three bryophyte species responded to increased nitrogen loads in a long-term fertilization experiment in a boreal Picea abies forest in southern Norway. Overall, OTU richness, community composition and the relative abundance of specific ecological guilds were primarily influenced by host species identity and tissue type. Although not the primary factor affecting fungal communities, nitrogen addition did impact the abundance of specific guilds of fungi and the resulting overall community composition. Increased nitrogen loads decreased ectomycorrhizal abundance, with Amphinema, Cortinarius, Russula and Tylospora OTUs responding negatively to fertilization. Pathogen abundance increased with fertilization, particularly in the moss pathogen Eocronartium. Saprophytic fungi were both positively and negatively impacted by the nitrogen addition, indicating a complex community level response. The overshadowing of the effects of increased nitrogen loads by variation related to host and tissue type highlights the complexity of bryophyte-associated microbial communities and the intricate nature of their responses to anthropogenic global change.

Fungi Sailing the Arctic Ocean: Speciose Communities in North Atlantic Driftwood as Revealed by High-Throughput Amplicon Sequencing.

High amounts of driftwood sail across the oceans and provide habitat for organisms tolerating the rough and saline environment. Fungi have adapted to the extremely cold and saline conditions which driftwood faces in the high north. For the first time, we applied high-throughput sequencing to fungi residing in driftwood to reveal their taxonomic richness, community composition, and ecology in the North Atlantic. Using pyrosequencing of ITS2 amplicons obtained from 49 marine logs, we found 807 fungal operational taxonomic units (OTUs) based on clustering at 97 % sequence similarity cut-off level. The phylum Ascomycota comprised 74 % of the OTUs and 20 % belonged to Basidiomycota. The richness of basidiomycetes decreased with prolonged submersion in the sea, supporting the general view of ascomycetes being more extremotolerant. However, more than one fourth of the fungal OTUs remained unassigned to any fungal class, emphasising the need for better DNA reference data from the marine habitat. Different fungal communities were detected in coniferous and deciduous logs. Our results highlight that driftwood hosts a considerably higher fungal diversity than currently known. The driftwood fungal community is not a terrestrial relic but a speciose assemblage of fungi adapted to the stressful marine environment and different kinds of wooden substrates found in it.

Forestry impacts on the hidden fungal biodiversity associated with bryophytes.

Recent studies have revealed an unexpectedly high, cryptic diversity of fungi associated with boreal forest bryophytes. Forestry practices heavily influence the boreal forest and fundamentally transform the landscape. However, little is known about how bryophyte-associated fungal communities are affected by these large-scale habitat transformations. This study assesses to what degree bryophyte-associated fungal communities are structured across the forest successional stages created by current forestry practices. Shoots of Hylocomium splendens were collected in Picea abies dominated forests of different ages, and their associated fungal communities were surveyed by pyrosequencing of ITS2 amplicons. Although community richness, diversity and evenness were relatively stable across the forest types and all were consistently dominated by ascomycete taxa, there was a marked shift in fungal community composition between young and old forests. Numerous fungal operational taxonomic units (OTUs) showed distinct affinities for different forest ages. Spatial structure was also detected among the sites, suggesting that environmental gradients resulting from the topography of the study area and dispersal limitations may also significantly affect bryophyte-associated fungal community structure. This study confirms that Hylocomium splendens hosts an immense diversity of fungi and demonstrates that this community is structured in part by forest age, and as such is highly influenced by modern forestry practices.

New resinicolous Chaenothecopsis species from China.

Four new resinicolous species of Chaenothecopsis are described from China: Chaenothecopsis perforata from exudate of Rhus chinensis (Anacardiaceae), C. pallida from exudate of Ailanthus altissima (Simaroubaceae), C. resinophila from exudate of Kalopanax septemlobus (Araliaceae) and C. hunanensis from resin of Pinus massoniana (Pinaceae). All the new species are compared with previously described resinicolous mycocalicioid taxa, and several new features in these species are presented. The newly described species cannot always be distinguished by any single character, but they all possess unique combinations of morphological, chemical and ecological features. Several aspects in the ecology and evolution of boreal and tropical resinicolous species are briefly discussed.

Low host specificity of root-associated fungi at an Arctic site.

In High Arctic ecosystems, plant growth and reproduction are limited by low soil moisture and nutrient availability, low soil and air temperatures, and a short growing season. Mycorrhizal associations facilitate plant nutrient acquisition and water uptake and may therefore be particularly ecologically important in nutrition-poor and dry environments, such as parts of the Arctic. Similarly, endophytic root associates are thought to play a protective role, increasing plants' stress tolerance, and likely have an important ecosystem function. Despite the importance of these root-associated fungi, little is known about their host specificity in the Arctic. We investigated the host specificity of root-associated fungi in the common, widely distributed arctic plant species Bistorta vivipara, Salix polaris and Dryas octopetala in the High Arctic archipelago Svalbard. High-throughput sequencing of the internal transcribed spacer 1 (ITS1) amplified from whole root systems generated no evidence of host specificity and no spatial autocorrelation within two 3 m × 3 m sample plots. The lack of spatial structure at small spatial scales indicates that Common Mycelial Networks (CMNs) are rare in marginal arctic environments. Moreover, no significant differences in fungal OTU richness were observed across the three plant species, although their root system characteristics (size, biomass) differed considerably. Reasons for lack of host specificity could be that association with generalist fungi may allow arctic plants to more rapidly and easily colonize newly available habitats, and it may be favourable to establish symbiotic relationships with fungi possessing different physiological attributes.

Arctic root-associated fungal community composition reflects environmental filtering.

There is growing evidence that root-associated fungi have important roles in Arctic ecosystems. Here, we assess the diversity of fungal communities associated with roots of the ectomycorrhizal perennial herb Bistorta vivipara on the Arctic archipelago of Svalbard and investigate whether spatial separation and bioclimatic variation are important structuring factors of fungal community composition. We sampled 160 plants of B. vivipara from 32 localities across Svalbard. DNA was extracted from entire root systems, and 454 pyrosequencing of ITS1 amplicons was used to profile the fungal communities. The fungal communities were predominantly composed of Basidiomycota (55% of reads) and Ascomycota (35%), with the orders Thelephorales (24%), Agaricales (13.8%), Pezizales (12.6%) and Sebacinales (11.3%) accounting for most of the reads. Plants from the same site or region had more similar fungal communities to one another than plants from other sites or regions, and sites clustered together along a weak latitudinal gradient. Furthermore, a decrease in per-plant OTU richness with increasing latitude was observed. However, no statistically significant spatial autocorrelation between sites was detected, suggesting that environmental filtering, not dispersal limitation, causes the observed patterns. Our analyses suggest that while latitudinal patterns in community composition and richness might reflect bioclimatic influences at global spatial scales, at the smaller spatial scale of the Svalbard archipelago, these changes more likely reflect varied bedrock composition and associated edaphic factors. The need for further studies focusing on identifying those specific bioclimatic and edaphic factors structuring root-associated fungal community composition at both global and local scales is emphasized.

Fungal palaeodiversity revealed using high-throughput metabarcoding of ancient DNA from arctic permafrost.

The taxonomic and ecological diversity of ancient fungal communities was assessed by combining next generation sequencing and metabarcoding of DNA preserved in permafrost. Twenty-six sediment samples dated 16 000-32 000 radiocarbon years old from two localities in Siberia were analysed for fungal ITS. We detected 75 fungal OTUs from 21 orders representing three phyla, although rarefaction analyses suggested that the full diversity was not recovered despite generating an average of 6677 ± 3811 (mean ± SD) sequences per sample and that preservation bias likely has considerable effect on the recovered DNA. Most OTUs (75.4%) represented ascomycetes. Due to insufficient sequencing depth, DNA degradation and putative preservation biases in our samples, the recovered taxa probably do not represent the complete historic fungal community, and it is difficult to determine whether the fungal communities varied geographically or experienced a composition shift within the period of 16 000-32 000 bp. However, annotation of OTUs to functional ecological groups provided a wealth of information on the historic communities. About one-third of the OTUs are presumed plant-associates (pathogens, saprotrophs and endophytes) typical of graminoid- and forb-rich habitats. We also detected putative insect pathogens, coprophiles and keratinophiles likely associated with ancient insect and herbivore faunas. The detection of putative insect pathogens, mycoparasites, aquatic fungi and endophytes broadens our previous knowledge of the diversity of fungi present in Beringian palaeoecosystems. A large group of putatively psychrophilic/psychrotolerant fungi was also detected, most likely representing a modern, metabolically active fungal community.

Amplicon-pyrosequencing-based detection of compositional shifts in bryophyte-associated fungal communities along an elevation gradient.

Although bryophytes are a dominant vegetation component of boreal and alpine ecosystems, little is known about their associated fungal communities. HPLC assays of ergosterol (fungal biomass) and amplicon pyrosequencing of the ITS2 region of rDNA were used to investigate how the fungal communities associated with four bryophyte species changed across an elevational gradient transitioning from conifer forest to the low-alpine. Fungal biomass and OTU richness associated with the four moss hosts did not vary significantly across the gradient (P > 0.05), and both were more strongly affected by host and tissue type. Despite largely constant levels of fungal biomass, distinct shifts in community composition of fungi associated with Hylocomium, Pleurozium and Polytrichum occurred between the elevation zones of the gradient. This likely is a result of influence on fungal communities by major environmental factors such as temperature, directly or indirectly mediated by, or interacting with, the response of other components of the vegetation (i.e. the dominant trees). Fungal communities associated with Dicranum were an exception, exhibiting spatial autocorrelation between plots, and no significant structuring by elevation. Nevertheless, the detection of distinct fungal assemblages associated with a single host growing in different elevation zones along an elevational gradient is of particular relevance in the light of the ongoing changes in vegetation patterns in boreal and alpine systems due to global climate warming.

Seasonal trends in the biomass and structure of bryophyte-associated fungal communities explored by 454 pyrosequencing.

Bryophytes are a dominant vegetation component of the boreal forest, but little is known about their associated fungal communities, including seasonal variation within them. Seasonal variation in the fungal biomass and composition of fungal communities associated with three widespread boreal bryophytes was investigated using HPLC assays of ergosterol and amplicon pyrosequencing of the internal transcribed spacer 2 (ITS2) region of rDNA. The bryophyte phyllosphere community was dominated by Ascomycota. Fungal biomass did not decline appreciably in winter (P=0.272). Significant host-specific patterns in seasonal variation of biomass were detected (P=0.003). Although seasonal effects were not the primary factors structuring community composition, collection date significantly explained (P=0.001) variation not attributed to locality, host, and tissue. Community homogenization and a reduction in turnover occurred with the onset of frost events and subzero air and soil temperatures. Fluctuations in the relative abundance of particular fungal groups seem to reflect the nature of their association with mosses, although conclusions are drawn with caution because of potential methodological bias. The moss-associated fungal community is dynamic, exhibiting seasonal turnover in composition and relative abundance of different fungal groups, and significant fungal biomass is present year-round, suggesting a winter-active fungal community.

Endophoma, a new didymellaceous endoconidial genus from bat-cave soil.

A new endoconidial taxon, Endophoma elongata gen. et sp. nov., isolated from bat-cave soil, is reported from Alberta, Canada. It is morphologically unique in producing two forms of unilocular, endoconidial conidiomata (i.e. a superficially Phoma-like spherical, often ostiolate form and a cylindrical, non-ostiolate, often setose cleistopycnidial form). Locules of both forms are pseudoparenchymatous, filled with hyaline, thin-walled, endoconidial conidiogenous cells. Endoconidia are hyaline and unicellular. One- or two-celled chlamydospores are abundant in culture. Phylogenetic analysis of the LSU, ITS and ß-tubulin regions indicates Endophoma is a member of the Didymellaceae and remote from all other endoconidial genera. Endoconidiogenesis has not been reported previously within the Didymellaceae, and Endophoma represents the first report of a coelomycetous, endoconidial genus in the Pleosporales.

Pathogenesis of bryophyte hosts by the ascomycete Atradidymella muscivora.

Atradidymella muscivora (Pleosporales) is a bryophyte pathogen that infects the mosses Aulacomnium palustre, Hylocomium splendens, and Polytrichum juniperinum. Light and scanning electron microscopy and extracellular enzyme production were used to characterize the interactions between this fungus and its native hosts and the model host Funaria hygrometrica. Penetration was direct via hyphae or appressoria, and hosts responded by forming layered, darkly pigmented deposits at penetration sites, similar to the papillae formed by vascular plants in response to fungal infection. Infected hosts gradually became chlorotic as hyphae grew intracellularly, presumably killing host cells. Pycnidia of the Phoma anamorph (P. muscivora) and uniloculate pseudothecia were initiated as tightly packed masses of stromatic dematiaceous hyphae within a single host cell. Mature pycnidia and pseudothecia were erumpent. A new microniche among bryophilous fungi is described, whereby A. muscivora supplants the gemmae of Aul. palustre and exploits the normal nutrient-flow of the moss gametophyte. Atradidymella muscivora produced both cellulases and soluble polyphenolic oxidases, allowing it to also function as a saprobe and degrade the cell walls of bryophytes. The saprophytic and pathogenic abilities of A. muscivora suggest it may play a role in nutrient cycling, population dynamics, and small-scale disturbances in boreal ecosystems.

Atradidymella muscivora gen. et sp. nov. (Pleosporales) and its anamorph Phoma muscivora sp. nov.: A new pleomorphic pathogen of boreal bryophytes.

During a survey of bryophilous fungi from boreal and montane habitats, 12 isolates of a hitherto unknown plant pathogenic member of the Pleosporales were recovered from Aulacomnium palustre, Hylocomium splendens, and Polytrichum juniperinum, and described as Atradidymella muscivora gen. et sp. nov. Atradidymella is characterized by minute, unilocular, setose pseudothecia having 2-3 wall layers; brown, fusiform, 1-septate ascospores; and a Phoma anamorph. The genus is distinguished from all other pleosporalean genera with brown, fusiform ascospores on the basis of ascospore and pseudothecium morphology and a highly reduced stroma that is localized within a single host cell. Atradidymella muscivora is distinguished by its minute pseudothecia (<115 µm) and ascospores that are slightly allantoid and constricted at the septum with the upper cell often wider than the lower. Its anamorph, Phoma muscivora sp. nov., is morphologically distinguishable from P. herbarum in having smaller conidia. Parsimony analysis of the ITS rDNA region indicates A. muscivora has affinities to the Phoma-Ascochyta-Didymella clade that is sister to the Phaeosphaeriaceae within the Pleosporales.