Biogeography of aquatic hyphomycetes: Current knowledge and future perspectives

Seasonal fluctuations and diversity of Ingoldian mycobiota in two water bodies receiving different effluents at Assiut Governorate (Upper Egypt)

In the current study, fifty-eight Ingoldain fungal species assignable to forty-one genera were recovered from two water bodies receiving the treated sewage and the effluents of oils and soaps factory at Assiut Governorate (Upper Egypt), of which Anguillospora, Amniculicola, Flagellospora, and Mycocentrospora were the most prevalent genera. The most widespread identified species were Anguillospora furtive, Amniculicola longissima and Flagellospora fusarioides. Forty-three species were identified for the first time in Egypt. The most Ingoldain taxa were estimated for El-Zinnar canal, with the highest recorded taxa in winter. Whereas, the highest dominance of Ingoldian fungi was estimated for the El-Ibrahimia canal. The highest Simpson and Shannon diversity indexes were estimated for El-Zinnar canal samples recording 0.9683 and 3.741, respectively. The poorest water sites with Ingoldian fungi were those exposed directly to either treated sewage or industrial effluents, with which relatively higher values of water conductivity, cations and anions. Water temperature was the main abiotic factor driving the seasonal occurrence of Ingoldian fungi. It is interesting to isolate some Ingoldian fungal species from the stressful water sites receiving the effluents which provide valuable insights regarding their adaptation, predictive and putative role as bioindicators and their potentiality in pollutants degradation, organic decomposition, and transformation of xenobiotic compounds.

Eco-physiological Responses of Aquatic Fungi to Three Global Change Stressors Highlight the Importance of Intraspecific Trait Variability

Anthropogenic change at a global scale is affecting life on Earth with impacts on freshwaters. Aquatic hyphomycetes are fungi that drive organic matter decomposition in freshwaters and mediate energy transfer to higher trophic levels. Intraspecific trait variability affects ecological processes and can account for species adaptations to environmental change. To ascertain how aquatic hyphomycetes respond to global change related stressors, we selected 20 strains (7 species), based on their co-occurrence in streams and phylogenetic relatedness. We measured fungal growth rates at different temperatures (7 levels), nutrient concentrations (6 levels) and medium moisture (6 levels). Our results indicate that all stressors affected fungal growth, and responses to nutrient enrichment and moisture were strain specific. Fungal responses to the stressors were not explained by their phylogenetic relatedness. In the absence of stressors, interspecific diversity best explained the variance in fungal traits, while the increase in the stress gradient increased the importance of intraspecific diversity.

Drying Shapes Aquatic Fungal Community Assembly by Reducing Functional Diversity

Aquatic fungi are highly diverse organisms that play a critical role in global biogeochemical cycles. Yet it remains unclear which assembly processes determine their co-occurrence and assembly patterns over gradients of drying intensity, which is a common stressor in fluvial networks. Although aquatic fungi possess drying-specific adaptations, little is known about how functional similarity influences co-occurrence probability and which functional traits are sorted by drying. Using field data from 15 streams, we investigated how co-occurrence patterns and assembly processes responded to drying intensity. To do so, we determined fungal co-occurrence patterns, functional traits that best explain species co-occurrence likelihood, and community assembly mechanisms explaining changes in functional diversity over the drying gradient. Our results identified 24 species pairs with positive co-occurrence probabilities and 16 species pairs with negative associations. The co-occurrence probability was correlated with species differences in conidia shape and fungal endophytic capacity. Functional diversity reduction over the drying gradient is generally associated with non-random abiotic filtering. However, the assembly processes changed over the drying gradient, with random assembly prevailing at low drying intensity and abiotic filtering gaining more importance as drying intensifies. Collectively, our results can help anticipate the impacts of global change on fungal communities and ecosystem functioning.

Drying shapes the ecological niche of aquatic fungi with implications on ecosystem functioning

Fungi are among the most abundant and diverse organisms on Earth and play pivotal roles in global carbon processing, nutrient cycling and food webs. Despite their abundant and functional importance, little is known about the patterns and mechanisms governing their community composition in intermittent rivers and ephemeral streams, which are the most common fluvial ecosystems globally. Thus far, it is known that aquatic fungi have evolved various life-history strategies and functional adaptations to cope with drying. Nevertheless, some of these adaptations have a metabolic cost and trade-offs between growth, reproduction and dispersion that may affect ecosystem functioning. Thus, understanding their ecological strategies along a gradient of drying is crucial to assess how species will respond to global change and to identify meaningful taxa to maintain ecosystem functions. By combining in situ hydrological information with a niche-based approach, we analysed the role of drying in explaining the spatial segregation of fungal species, and we determined their specialization and affinity over a gradient of drying. In addition, we estimated whether species niches are good predictors of two key ecosystem processes: organic matter decomposition and fungal biomass accrual. Overall, we found that annual drying duration and frequency were the most influential variables upon species niche differentiation across the 15 studied streams. Our cluster analysis identified four drying niche-based groups with contrasting distributions and responses over the drying gradient: drying-sensitive, partly tolerant to drying, generalist, and drying-resistant specialist. In addition, we found that species belonging to the drying specialist group showed a weak contribution to both ecosystem processes, suggesting trade-offs between drying resistance strategies and the energy invested in growth. Taken together, our results suggest that increased water scarcity may jeopardise the capacity of aquatic fungi to guarantee ecosystem functioning and to maintain biogeochemical cycles despite their ability to cope with drying.

ITS rDNA Barcodes Clarify Molecular Diversity of Aquatic Hyphomycetes

Aquatic hyphomycetes are key microbial decomposers of allochthonous organic matter in freshwater ecosystems. Although their importance in carbon flow and food webs in streams is widely recognized, there are still gaps in our understanding of their molecular diversity and distribution patterns. Our study utilized the growing database of ITS rDNA barcodes of aquatic hyphomycetes (1252 sequences) and aimed to (i) produce new barcodes for some lesser-known taxa; (ii) clarify the taxonomic placement of some taxa at the class or order level, based on molecular data; and (iii) provide insights into the biogeographical origins of some taxa. This study increased the number of aquatic hyphomycete species with available ITS barcodes from 119 (out of ~300 species described) to 136. Phylogenetically, the 136 species were distributed between 2 phyla, 6 classes, and 10 orders of fungi. Future studies should strive to increase the database of ITS sequences, especially focusing on species with unclear phylogenetic relationships (incertae sedis) and with few sequences available. The geographical distribution of species with available ITS sequences included 50 countries from five continents, but 6 countries had more than 20 species associated, showing a bias toward the northern hemisphere, likely due to sampling bias.

Studies on aquatic fungi in Dikarya: a review of the literature from Southern Cone of South America

A bibliographic analysis was carried out to update the state of knowledge about aquatic fungi belonging to the subkingdom Dikarya in the Southern Cone of South America. The exhaustive search resulted in 38 articles reported. These papers correspond to those on taxonomic, ecological and biogeographic topics and include studies from lotic environments of the temperate ecoregions of Chile and Argentina. A total of 325 aquatic fungal taxa were reported, of which 318 belong to the phylum Ascomycota and 7 to the phylum Basidiomycota. According to the subgroups of these aquatic fungi 17 taxa were aero-aquatic, 199 facultative and 109 Ingoldian fungi. Regarding the methodologies, in these studies the information was obtained mainly by using lignocellulosic substrates such as leaf litter and wood as fungal source and wet chamber traditional working technique. However, more studies are still needed using other few-reported perspectives for the region such as ecological and molecular approaches as well as analyses of water environments belonging to unexplored biomes. This information can contribute to a better understanding of aquatic fungal communities and their role in ecosystems of the Southern Cone of South America.

Fungi in Freshwaters: Prioritising Aquatic Hyphomycetes in Conservation Goals

Deprivation of protection for aquatic hyphomycetes is disturbing because they are key players in freshwater ecosystems across the globe. To attain a more holistic conservation paradigm for biodiversity in freshwaters, it is necessary to broaden our ecological perception of microfungi, mainly in aquatic hyphomycetes. A considerable groundwork still needs to be accomplished in progressing towards conserving aquatic hyphomycetes. Overcoming the paucity of information regarding the rare and endangered species, biogeography and above all, a global biodiversity database, would be a significant contribution in the initiation of an overarching conservation strategy for aquatic hyphomycetes. Being aware that the biodiversity decline in freshwaters is alarming, here we seek to explore why biodiversity data of aquatic hyphomycetes are missing. This article closely examines the threats to the biodiversity of aquatic hyphomycetes and freshwater ecosystems. Moving forward, we advocate a structured approach to gaining a thorough understanding to embrace aquatic hyphomycetes biodiversity into the conservation strategies. Including aquatic hyphomycetes in the conservation objectives may attract more funding opportunities for global surveys to initiate a fungal inclusive conservation era. Fungal conservation ventures can profit from interdisciplinary collaborations and cutting-edge science and technology, leading to informed decision making for biodiversity assessment and management.

Elevated temperature may reduce functional but not taxonomic diversity of fungal assemblages on decomposing leaf litter in streams

Mounting evidence points to a linkage between biodiversity and ecosystem functioning (B-EF). Global drivers, such as warming and nutrient enrichment, can alter species richness and composition of aquatic fungal assemblages associated with leaf-litter decomposition, a key ecosystem process in headwater streams. However, effects of biodiversity changes on ecosystem functions might be countered by the presumed high functional redundancy of fungal species. Here, we examined how environmental variables and leaf-litter traits (based on leaf chemistry) affect taxonomic and functional α- and β-diversity of fungal decomposers. We analysed taxonomic diversity (DNA-fingerprinting profiles) and functional diversity (community-level physiological profiles) of fungal communities in four leaf-litter species from four subregions differing in stream-water characteristics and riparian vegetation. We hypothesized that increasing stream-water temperature and nutrients would alter taxonomic diversity more than functional diversity due to the functional redundancy among aquatic fungi. Contrary to our expectations, fungal taxonomic diversity varied little with stream-water characteristics across subregions, and instead taxon replacement occurred. Overall taxonomic β-diversity was fourfold higher than functional diversity, suggesting a high degree of functional redundancy among aquatic fungi. Elevated temperature appeared to boost assemblage uniqueness by increasing β-diversity while the increase in nutrient concentrations appeared to homogenize fungal assemblages. Functional richness showed a negative relationship with temperature. Nonetheless, a positive relationship between leaf-litter decomposition and functional richness suggests higher carbon use efficiency of fungal communities in cold waters.

Aquatic Hyphomycete Taxonomic Relatedness Translates into Lower Genetic Divergence of the Nitrate Reductase Gene

Aquatic hyphomycetes are key microbial decomposers in freshwater that are capable of producing extracellular enzymes targeting complex molecules of leaf litter, thus, being crucial to nutrient cycling in these ecosystems. These fungi are also able to assimilate nutrients (e.g., nitrogen) from stream water, immobilizing these nutrients in the decomposing leaf litter and increasing its nutritional value for higher trophic levels. Evaluating the aquatic hyphomycete functional genetic diversity is, thus, pivotal to understanding the potential impacts of biodiversity loss on nutrient cycling in freshwater. In this work, the inter- and intraspecific taxonomic (ITS1-5.8S-ITS2 region) and functional (nitrate reductase gene) diversity of 40 aquatic hyphomycete strains, belonging to 23 species, was evaluated. A positive correlation was found between the taxonomic and nitrate reductase gene divergences. Interestingly, some cases challenged this trend: Dactylella cylindrospora (Orbiliomycetes) and Thelonectria rubi (Sordariomycetes), which were phylogenetically identical but highly divergent regarding the nitrate reductase gene; and Collembolispora barbata (incertae sedis) and Tetracladium apiense (Leotiomycetes), which exhibited moderate taxonomic divergence but no divergence in the nitrate reductase gene. Additionally, Tricladium chaetocladium (Leotiomycetes) strains were phylogenetically identical but displayed a degree of nitrate reductase gene divergence above the average for the interspecific level. Overall, both inter- and intraspecific functional diversity were observed among aquatic hyphomycetes.

Priority effects of stream eutrophication and assembly history on beta diversity across aquatic consumers, decomposers and producers

Priority effects are stochastic processes that consider the influence of the order of arrival of species on community dynamics and structure. We evaluated the short-term effects of stream eutrophication and colonization time in freshwater benthic communities (primary producers - periphytic algae, decomposers - fungi, and consumers - macroinvertebrates) to test whether (i) beta diversity is higher in eutrophic streams due to priority effects driven by stochastic community formation processes (ecological drift or random dispersal), and (ii) in the early stages of colonization, priority effects drive the history of the formation and the initial establishment of the community in the stream, resulting in higher beta diversity. The present study was conducted in situ over 28 days in temperate streams along a trophic gradient, with colonization being evaluated every seven days. The study identified 84 species of alga, 43 families of macroinvertebrates, and 44 species of aquatic fungi. Our results demonstrated that deterministic processes were responsible for the formation of aquatic producers, while priority effects (stochasticity) were more important for the aquatic decomposers and consumers. In the case of the producers, beta diversity was highest in the hypertrophic stream, but did not vary significantly over colonization time. The beta diversity of the decomposers was highest in the hypertrophic stream and in the later stages of succession, due primarily to mechanisms of facilitation. The beta diversity of the consumers was lowest in the hypertrophic stream due primarily to the priority and inhibitory effects of the predominant groups, and highest at seven and 21 days of colonization. As these three taxonomic groups differ in their intrinsic biological characteristics, and in their functional role in the ecosystem, our short-term field study demonstrated that both stochastic and deterministic processes combine to influence the configuration of the community, and that the relative importance of the two processes varies systematically along a trophic gradient.

Litter Quality Is a Stronger Driver than Temperature of Early Microbial Decomposition in Oligotrophic Streams: a Microcosm Study

Litter decomposition is an ecological process of key importance for forest headwater stream functioning, with repercussions for the global carbon cycle. The process is directly and indirectly mediated by microbial decomposers, mostly aquatic hyphomycetes, and influenced by environmental and biological factors such as water temperature and litter quality. These two factors are forecasted to change globally within the next few decades, in ways that may have contrasting effects on microbial-induced litter decomposition: while warming is expected to enhance microbial performance, the reduction in litter quality due to increased atmospheric carbon dioxide and community composition alteration may have the opposite outcome. We explored this issue through a microcosm experiment focused on early microbial-mediated litter decomposition under stream oligotrophic conditions, by simultaneously manipulating water temperature (10 °C and 15 °C) and litter quality (12 broadleaf plant species classified into 4 categories based on initial concentrations of nitrogen and tannins). We assessed potential changes in microbial-mediated litter decomposition and the performance of fungal decomposers (i.e., microbial respiration, biomass accrual, and sporulation rate) and species richness. We found stronger effects of litter quality, which enhanced the performance of microbial decomposers and decomposition rates, than temperature, which barely influenced any of the studied variables. Our results suggest that poorer litter quality associated with global change will have a major repercussion on stream ecosystem functioning.

Loan default prediction of Chinese P2P market: a machine learning methodology

Repayment failures of borrowers have greatly affected the sustainable development of the peer-to-peer (P2P) lending industry. The latest literature reveals that existing risk evaluation systems may ignore important signals and risk factors affecting P2P repayment. In our study, we applied four machine learning methods (random forest (RF), extreme gradient boosting tree (XGBT), gradient boosting model (GBM), and neural network (NN)) to predict important factors affecting repayment by utilizing data from Renrendai.com in China from Thursday, January 1, 2015, to Tuesday, June 30, 2015. The results showed that borrowers who have passed video, mobile phone, job, residence or education level verification are more likely to default on loan repayment, whereas those who have passed identity and asset certification are less likely to default on loans. The accuracy and kappa value of the four methods all exceed 90%, and RF is superior to the other classification models. Our findings demonstrate important techniques for borrower screening by P2P companies and risk regulation by regulatory agencies. Our methodology and findings will help regulators, banks and creditors combat current financial disasters caused by the coronavirus disease 2019 (COVID-19) pandemic by addressing various financial risks and translating credit scoring improvements.

The Utility of Macroecological Rules for Microbial Biogeography

Macroecological rules have been developed for plants and animals that describe large-scale distributional patterns and attempt to explain the underlying physiological and ecological processes behind them. Similarly, microorganisms exhibit patterns in relative abundance, distribution, diversity, and traits across space and time, yet it remains unclear the extent to which microorganisms follow macroecological rules initially developed for macroorganisms. Additionally, the usefulness of these rules as a null hypothesis when surveying microorganisms has yet to be fully evaluated. With rapid advancements in sequencing technology, we have seen a recent increase in microbial studies that utilize macroecological frameworks. Here, we review and synthesize these macroecological microbial studies with two main objectives: (1) to determine to what extent macroecological rules explain the distribution of host-associated and free-living microorganisms, and (2) to understand which environmental factors and stochastic processes may explain these patterns among microbial clades (archaea, bacteria, fungi, and protists) and habitats (host-associated and free living; terrestrial and aquatic). Overall, 78% of microbial macroecology studies focused on free living, aquatic organisms. In addition, most studies examined macroecological rules at the community level with only 35% of studies surveying organismal patterns across space. At the community level microorganisms often tracked patterns of macroorganisms for island biogeography (74% confirm) but rarely followed Latitudinal Diversity Gradients (LDGs) of macroorganisms (only 32% confirm). However, when microorganisms and macroorganisms shared the same macroecological patterns, underlying environmental drivers (e.g., temperature) were the same. Because we found a lack of studies for many microbial groups and habitats, we conclude our review by outlining several outstanding questions and creating recommendations for future studies in microbial ecology.

Invasion of Native Riparian Forests by Acacia Species Affects In-Stream Litter Decomposition and Associated Microbial Decomposers

The invasion of native riparian forests by exotic tree species can lead to profound changes in the ecological integrity of freshwater ecosystems. We assessed litter decomposition of native (Alnus glutinosa and Quercus robur) and invasive (Acacia melanoxylon and Acacia dealbata) tree species, and associated microbial activity and community structure, after being immersed for conditioning in 3 reference and 3 "invaded" streams in Serra da Lousã (central Portugal) and used in microcosms simulating stream conditions. Litter decomposition differed among species, in the order: Al. glutinosa > Q. robur > (Ac. melanoxylon ~ Ac. dealbata). Alnus glutinosa litter decomposed faster probably because it was soft and had high nitrogen concentration for decomposers. Quercus robur litter decomposed slower most likely because it was tough and had high polyphenol and low nitrogen concentrations. Acacia melanoxylon litter was the toughest and had a thick cuticle that likely acted as a physical barrier for microbial colonization. In Ac. dealbata, the small-sized leaflets and high lignin concentration may have limited microbial litter decomposition. Litter decomposition was faster in "invaded" streams, probably because they were N-limited and increases in nitrogen concentration in water, promoted by Acacia species invasion, stimulated microbial activity on litter. The aquatic hyphomycete community structure differed among litter species and between stream types, further suggesting that microbes were sensitive to litter characteristics and water nutrient concentrations. Overall, the invasion of native riparian forests by Acacia species may affect microbial decomposer activity, thus altering important stream ecosystem processes, such as litter decomposition and nutrient cycles.

Aquatic Hyphomycetes from streams on Madeira Island (Portugal)

BACKGROUND

Aquatic hyphomycetes are a phylogenetically heterogeneous group of fungi living preferentially in fast flowing, well-aerated forest streams. These fungi have worldwide distribution, but with the exception of Articulospora tetracladia, no aquatic hyphomycete taxon was previously recorded on Madeira Island. Aquatic hyphomycetes were sampled from 40 sites, distributed by 27 permanent streams in 2015, to provide the distribution of aquatic hyphomycetes in Madeira Island streams.

NEW INFORMATION

In this study, a total of 21 species of aquatic hyphomycetes were recorded belonging to three classes of Ascomycota. All taxa are new records for Madeira Archipelago, except Articulospora tetracladia and four are reported for the first time in Macaronesian biogeographic region.

Patellariopsidaceae Fam. Nov. With Sexual-Asexual Connection and a New Host Record for Cheirospora botryospora (Vibrisseaceae, Ascomycota)

Helotiales is a polyphyletic order of Ascomycetes. The paucity of relevant molecular data and unclear connections of sexual and asexual morphs present challenges in resolving taxa within this order. In the present study, Patellariopsidaceae fam. nov., the asexual morph of Patellariopsis atrovinosa, and a new record of Cheirospora botryospora (Vibrisseaceae) on Fagus sylvatica (Fagaceae) from Italy are discussed based on morphology and molecular phylogeny. Phylogenetic analyses based on a combined sequence dataset of LSU and ITS were used to infer the phylogenetic relationships within the Helotiales. The results of this research provide a solid base to the taxonomy and phylogeny of Helotiales.

Fungal diversity notes 1151–1276: taxonomic and phylogenetic contributions on genera and species of fungal taxa

Fungal diversity notes is one of the important journal series of fungal taxonomy that provide detailed descriptions and illustrations of new fungal taxa, as well as providing new information of fungal taxa worldwide. This article is the 11th contribution to the fungal diversity notes series, in which 126 taxa distributed in two phyla, six classes, 24 orders and 55 families are described and illustrated. Taxa in this study were mainly collected from Italy by Erio Camporesi and also collected from China, India and Thailand, as well as in some other European, North American and South American countries. Taxa described in the present study include two new families, 12 new genera, 82 new species, five new combinations and 25 new records on new hosts and new geographical distributions as well as sexual-asexual reports. The two new families are Eriomycetaceae (Dothideomycetes, family incertae sedis) and Fasciatisporaceae (Xylariales, Sordariomycetes). The twelve new genera comprise Bhagirathimyces (Phaeosphaeriaceae), Camporesiomyces (Tubeufiaceae), Eriocamporesia (Cryphonectriaceae), Eriomyces (Eriomycetaceae), Neomonodictys (Pleurotheciaceae), Paraloratospora (Phaeosphaeriaceae), Paramonodictys (Parabambusicolaceae), Pseudoconlarium (Diaporthomycetidae, genus incertae sedis), Pseudomurilentithecium (Lentitheciaceae), Setoapiospora (Muyocopronaceae), Srinivasanomyces (Vibrisseaceae) and Xenoanthostomella (Xylariales, genera incertae sedis). The 82 new species comprise Acremonium chiangraiense, Adustochaete nivea, Angustimassarina camporesii, Bhagirathimyces himalayensis, Brunneoclavispora camporesii, Camarosporidiella camporesii, Camporesiomyces mali, Camposporium appendiculatum, Camposporium multiseptatum, Camposporium septatum, Canalisporium aquaticium, Clonostachys eriocamporesiana, Clonostachys eriocamporesii, Colletotrichum hederiicola, Coniochaeta vineae, Conioscypha verrucosa, Cortinarius ainsworthii, Cortinarius aurae, Cortinarius britannicus, Cortinarius heatherae, Cortinarius scoticus, Cortinarius subsaniosus, Cytospora fusispora, Cytospora rosigena, Diaporthe camporesii, Diaporthe nigra, Diatrypella yunnanensis, Dictyosporium muriformis, Didymella camporesii, Diutina bernali, Diutina sipiczkii, Eriocamporesia aurantia, Eriomyces heveae, Ernakulamia tanakae, Falciformispora uttaraditensis, Fasciatispora cocoes, Foliophoma camporesii, Fuscostagonospora camporesii, Helvella subtinta, Kalmusia erioi, Keissleriella camporesiana, Keissleriella camporesii, Lanspora cylindrospora, Loratospora arezzoensis, Mariannaea atlantica, Melanographium phoenicis, Montagnula camporesii, Neodidymelliopsis camporesii, Neokalmusia kunmingensis, Neoleptosporella camporesiana, Neomonodictys muriformis, Neomyrmecridium guizhouense, Neosetophoma camporesii, Paraloratospora camporesii, Paramonodictys solitarius, Periconia palmicola, Plenodomus triseptatus, Pseudocamarosporium camporesii, Pseudocercospora maetaengensis, Pseudochaetosphaeronema kunmingense, Pseudoconlarium punctiforme, Pseudodactylaria camporesiana, Pseudomurilentithecium camporesii, Pseudotetraploa rajmachiensis, Pseudotruncatella camporesii, Rhexocercosporidium senecionis, Rhytidhysteron camporesii, Rhytidhysteron erioi, Septoriella camporesii, Setoapiospora thailandica, Srinivasanomyces kangrensis, Tetraploa dwibahubeeja, Tetraploa pseudoaristata, Tetraploa thrayabahubeeja, Torula camporesii, Tremateia camporesii, Tremateia lamiacearum, Uzbekistanica pruni, Verruconis mangrovei, Wilcoxina verruculosa, Xenoanthostomella chromolaenae and Xenodidymella camporesii. The five new combinations are Camporesiomyces patagoniensis, Camporesiomyces vaccinia, Camposporium lycopodiellae, Paraloratospora gahniae and Rhexocercosporidium microsporum. The 22 new records on host and geographical distribution comprise Arthrinium marii, Ascochyta medicaginicola, Ascochyta pisi, Astrocystis bambusicola, Camposporium pellucidum, Dendryphiella phitsanulokensis, Diaporthe foeniculina, Didymella macrostoma, Diplodia mutila, Diplodia seriata, Heterosphaeria patella, Hysterobrevium constrictum, Neodidymelliopsis ranunculi, Neovaginatispora fuckelii, Nothophoma quercina, Occultibambusa bambusae, Phaeosphaeria chinensis, Pseudopestalotiopsis theae, Pyxine berteriana, Tetraploa sasicola, Torula gaodangensis and Wojnowiciella dactylidis. In addition, the sexual morphs of Dissoconium eucalypti and Phaeosphaeriopsis pseudoagavacearum are reported from Laurus nobilis and Yucca gloriosa in Italy, respectively. The holomorph of Diaporthe cynaroidis is also reported for the first time.

Inter- and intraspecific functional variability of aquatic fungal decomposers and freshwater ecosystem processes

Although considerable intraspecific trait variation is common, research dedicated to ecosystem functioning has focused mainly on species diversity. Organic matter breakdown, a key ecosystem-level process in woodland streams is mainly driven by aquatic hyphomycetes. These aquatic fungal decomposers constitute a critical link between plant litter and invertebrate detritivores in detritus-based food webs in streams. In this study, we evaluated the functional variability across a set of ten isolates each belonging to five widespread aquatic hyphomycete species, namely Articulospora tetracladia, Anguillospora crassa, Lemonniera terrestris, Neonectria lugdunensis and Tetracladium marchalianum. All the isolates originated from undisturbed streams. We estimated inter- and intraspecific variability on growth rates, litter decomposition and sporulation rates of the isolates. In addition, we also assessed the invertebrate consumption rates on leaves colonized by different isolates. Significant differences were observed within the fungal species in growth rates (A. crassa, L. terrestris, N. lugdunensis and T. marchalianum), leaf litter decomposition (A. tetracladia, L. terrestris and N. lugdunensis) and sporulation rates (A. crassa, A. tetracladia, L. terrestris and N. lugdunensis). The relative consumption rates of the shredder Schizopelex festiva significantly differed when fed with leaves colonized by isolates of L. terrestris and N. lugdunensis, however differences were not seen when fed with leaves conditioned by different species. Overall, results indicate substantial intraspecific functional variability among the isolates of aquatic hyphomycetes. Besides, our study also provides a novel insight that intraspecific functional variability is a natural phenomenon exhibited by isolates not only from polluted but also from undisturbed streams. Here the isolates demonstrated marked inter- and intraspecific functional variability, calling for a greater understanding of the functional role of aquatic hyphomycetes and its ability to influence higher trophic levels.

Fungi in aquatic ecosystems

Fungi are phylogenetically and functionally diverse ubiquitous components of almost all ecosystems on Earth, including aquatic environments stretching from high montane lakes down to the deep ocean. Aquatic ecosystems, however, remain frequently overlooked as fungal habitats, although fungi potentially hold important roles for organic matter cycling and food web dynamics. Recent methodological improvements have facilitated a greater appreciation of the importance of fungi in many aquatic systems, yet a conceptual framework is still missing. In this Review, we conceptualize the spatiotemporal dimensions, diversity, functions and organismic interactions of fungi in structuring aquatic food webs. We focus on currently unexplored fungal diversity, highlighting poorly understood ecosystems, including emerging artificial aquatic habitats.

Insight into chronic exposure effects of nanosized titanium dioxide on Typha angustifolia leaf litter decomposition

Advancement in nanotechnology has increased production of nanoparticles which initiates concerns for freshwater ecosystems. Nanosized TiO₂ is one of the most used materials and its ecotoxicity has been extensively studied. Here, a freshwater microcosm experiment was performed to investigate the effects of nanosized (10, 60, and 100 nm) and bulk TiO₂ at 1 g L^-1 on the alteration in community structure of fungal decomposers and the consequences on litter decomposition of Typha angustifolia leaves. After 209 days of exposure, the decomposition rate was significantly higher in 100 nm TiO₂ treatment compared to the control, which was caused by its promotion on fungal biomass and metabolic activity. Therefore, the study provides the multifaceted evidences for different effects of TiO₂ with varied sizes on T. angustifolia leaf decomposition and highlights the importance of understanding the potential effects of varying sizes and long-term exposure in nanoparticle risk assessments.

Biodiversity of leaf litter fungi in streams along a latitudinal gradient

Global patterns of biodiversity have emerged for soil microorganisms, plants and animals, and the extraordinary significance of microbial functions in ecosystems is also well established. Virtually unknown, however, are large-scale patterns of microbial diversity in freshwaters, although these aquatic ecosystems are hotspots of biodiversity and biogeochemical processes. Here we report on the first large-scale study of biodiversity of leaf-litter fungi in streams along a latitudinal gradient unravelled by Illumina sequencing. The study is based on fungal communities colonizing standardized plant litter in 19 globally distributed stream locations between 69°N and 44°S. Fungal richness suggests a hump-shaped distribution along the latitudinal gradient. Strikingly, community composition of fungi was more clearly related to thermal preferences than to biogeography. Our results suggest that identifying differences in key environmental drivers, such as temperature, among taxa and ecosystem types is critical to unravel the global patterns of aquatic fungal diversity.

Rapid characterization of aquatic hyphomycetes by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Protein fingerprinting using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI--TOF MS) is a rapid, reliable, and economical method to characterize isolates of terrestrial fungi and other microorganisms. The objective of our study was to evaluate the suitability of MALDI-TOF MS for the identification of aquatic hyphomycetes, a polyphyletic group of fungi that play crucial roles in stream ecosystems. To this end, we used 34 isolates of 21 aquatic hyphomycete species whose identity was confirmed by spore morphology and internal transcribed spacer (ITS1-5.8S-ITS2 = ITS) nuc rDNA sequencing. We tested the efficiency of three protein extraction methods, including chemical and mechanical treatments using 13 different protocols, with the objective of producing high-quality MALDI-TOF mass spectra. In addition to extraction protocols, mycelium age was identified as a key parameter affecting protein extraction efficiency. The dendrogram based on mass-spectrum similarity indicated good and relevant taxonomic discrimination; the tree structure was comparable to that of the phylogram based on ITS sequences. Consequently, MALDI-TOF MS could reliably identify the isolates studied and provided greater taxonomic accuracy than classical morphological methods. MALDI-TOF MS seems suited for rapid characterization and identification of aquatic hyphomycete species.

Similar recovery time of microbial functions from fungicide stress across biogeographical regions

Determining whether the structural and functional stress responses of communities are similar across space and time is paramount for forecasting and extrapolating the consequences of anthropogenic pressures on ecosystems and their services. Stream ecosystems are under high anthropogenic pressure; however, studies have only examined the response of stream communities across large scales over multiple generations. We studied the responses of leaf-associated microbial communities in streams within three European biogeographical regions to chemical stress in a microcosm experiment with multiple cycles of fungicide pollution and resource colonisation. Fungal community composition and the ecosystem function leaf decomposition were measured as response variables. Microbial leaf decomposition showed similar recovery times under environmental levels of fungicide exposure across regions. Initially, the decomposition declined (between 19 and 53%) under fungicide stress and recovered to control levels during the third cycle of pollution and colonisation. Although community composition and its stress response varied between regions, this suggests similar functional community adaptation towards fungicide stress over time. Genetic, epigenetic and physiological adaptations, as well as species turnover, may have contributed to community adaptation but further studies are required to determine if and to which extent these mechanisms are operating. Overall, our findings provide the first evidence of a similar functional response of microbial leaf decomposition to chemical stress across space and time.

A High-Resolution Time Series Reveals Distinct Seasonal Patterns of Planktonic Fungi at a Temperate Coastal Ocean Site (Beaufort, North Carolina, USA)

There is a growing awareness of the ecological and biogeochemical importance of fungi in coastal marine systems. While highly diverse fungi have been discovered in these marine systems, still, little is known about their seasonality and associated drivers in coastal waters. Here, we examined fungal communities over 3 years of weekly sampling at a dynamic, temperate coastal site (Pivers Island Coastal Observatory [PICO], Beaufort, NC, USA). Fungal 18S rRNA gene abundance, operational taxonomic unit (OTU) richness, and Shannon's diversity index values exhibited prominent seasonality. Fungal 18S rRNA gene copies peaked in abundance during the summer and fall, with positive correlations with chlorophyll a, SiO₄, and oxygen saturation. Diversity (measured using internal transcribed spacer [ITS] libraries) was highest during winter and lowest during summer; it was linked to temperature, pH, chlorophyll a, insolation, salinity, and dissolved inorganic carbon (DIC). Fungal communities derived from ITS libraries were dominated throughout the year by Ascomycota, with contributions from Basidiomycota, Chytridiomycota, and Mucoromycotina, and their seasonal patterns linked to water temperature, light, and the carbonate system. Network analysis revealed that while cooccurrence and exclusion existed within fungus networks, exclusion dominated the fungus-and-phytoplankton network, in contrast with reported pathogenic and nutritional interactions between marine phytoplankton and fungi. Compared with the seasonality of bacterial communities in the same samples, the timing, extent, and associated environmental variables for fungi community are unique. These results highlight the fungal seasonal dynamics in coastal water and improve our understanding of the ecology of planktonic fungi.IMPORTANCE Coastal fungal dynamics were long assumed to be due to terrestrial inputs; here, a high-resolution time series reveals strong, repeating annual patterns linked to in situ environmental conditions, arguing for a resident coastal fungal community shaped by environmental factors. These seasonal patterns do, however, differ from those observed in the bacterioplankton at the same site; e.g., fungal diversity peaks in winter, whereas bacterial diversity maxima occur in the spring and fall. While the dynamics of these communities are linked to water temperature and insolation, fungi are also influenced by the carbonate system (pH and DIC). As both fungi and heterotrophic bacteria are thought to be key organic-material metabolizers, differences in their environmental drivers may offer clues as to which group dominates secondary production at this dynamic site. Overall, this study suggests the unique ecological roles of mycoplankton and their potentially broad niche complementarities to other microbial groups in the coastal ocean.

Influence of water quality on diversity and composition of fungal communities in a tropical river

Freshwater fungi are key decomposers of organic material and play important roles in nutrient cycling, bio-remediation and ecosystem functioning. Although aquatic fungal communities respond to pollution, few studies have quantitatively assessed the effect of freshwater contamination on fungal diversity and composition; and knowledge is scarcer for tropical systems. Here we help fill this knowledge gap by studying a heavily-contaminated South American river spanning a biodiversity hotspot. We collected 30 water samples scattered across a quality gradient over two seasons and analyzed them using Terminal Restriction Fragment Length Polymorphisms (T-RFLP) coupled with 454 Pyrosequencing. Using T-RFLP we identified 451 and 442 Operational Taxonomy Units (OTUs) in the dry and rainy seasons respectively, whereas Pyrosequencing revealed 48,553 OTUs from which 11% were shared between seasons. Although 68% of all identified OTUs and 51% of all identified phyla remained unidentified, dominant fungal phyla included the Ascomycota, Basidiomycota, Chytridiomycota, Glomeromycota, Zygomycota and Neocallimastigomycota, while Calcarisporiella, Didymosphaeria, Mycosphaerella (Ascomycota) and Rhodotorula (Basidiomycota) were the most abundant genera. Fungal diversity was affected by pH and dissolved iron, while community composition was influenced by dissolved oxygen, pH, nitrate, biological oxygen demand, total aluminum, total organic carbon, total iron and seasonality. The presence of potentially pathogenic species was associated with high pH. Furthermore, geographic distance was positively associated with community dissimilarity, suggesting that local conditions allowed divergence among fungal communities. Overall, our findings raise potential concerns for human health and the functioning of tropical river ecosystems and they call for improved water sanitation systems.

Taxa-area relationship of aquatic fungi on deciduous leaves

One of the fundamental patterns in macroecology is the increase in the number of observed taxa with size of sampled area. For microbes, the shape of this relationship remains less clear. The current study assessed the diversity of aquatic fungi, by the traditional approach based on conidial morphology (captures reproducing aquatic hyphomycetes) and next generation sequencing (NGS; captures other fungi as well), on graded sizes of alder leaves (0.6 to 13.6 cm2). Leaves were submerged in two streams in geographically distant locations: the Oliveira Stream in Portugal and the Boss Brook in Canada. Decay rates of alder leaves and fungal sporulation rates did not differ between streams. Fungal biomass was higher in Boss Brook than in Oliveira Stream, and in both streams almost 100% of the reads belonged to active fungal taxa. In general, larger leaf areas tended to harbour more fungi, but these findings were not consistent between techniques. Morphospecies-based diversity increased with leaf area in Boss Brook, but not in Oliveira Stream; metabarcoding data showed an opposite trend. The higher resolution of metabarcoding resulted in steeper taxa-accumulation curves than morphospecies-based assessments (fungal conidia morphology). Fungal communities assessed by metabarcoding were spatially structured by leaf area in both streams. Metabarcoding promises greater resolution to assess biodiversity patterns in aquatic fungi and may be more accurate for assessing taxa-area relationships and local to global diversity ratios.

Diurnal periodicity of conidia of aquatic hyphomycetes in water and entrapment on latex-coated slides in two South Indian streams

Aquatic hyphomycete conidial trapping efficiency by the banyan (F. benghalensis L.) latex-coated glass slides was tested diurnally (3 h intervals) in the Western Ghats (Sampaje) and west coast (Konaje) streams in relation to abiotic factors (humidity, air temperature and water temperature). The conidial trapping efficiency of latex-coated slides was compared with plain glass slides and drift conidia in water. Three methods of assessment showed higher species richness, conidial richness and diversity in Sampaje than in Konaje stream. In both streams, species richness, conidial richness and diversity in latex-coated slides were the highest followed by conidia in water and plain slides. Three-way ANOVA revealed significant differences in overall species and conidial richness between the streams, sampling methods and time of sampling (p < 0.001). Multiple comparisons by Holm-Sidak test revealed significant differences in overall species and conidial richness between Sampaje and Konaje (p < 0.001); latex-coated slides and plain slides (p < 0.001); latex-coated slides and water filtration (p < 0.001); plain slides and water filtration (p < 0.001). Total species, total conidia and diversity assessed by the three methods peaked during 12 am-3 am in Sampaje stream, while during 3 am-6 am in Konaje stream. Cooler conditions due to relatively low water temperature favoured higher diversity of aquatic hyphomycetes in Sampaje than in Konaje stream. The three methods employed in the present study were not biased towards scolecoid or stauroid conidia. The top five species in both streams was composed of both types of conidia corroborating earlier annual or biannual studies in Konaje and Sampaje streams. Thus, assessment of population of aquatic hyphomycetes using banyan latex-coated slides will be advantageous over plain slides and drift conidia in streams.