Fungal Ecology最新文献

Arbuscular mycorrhizal fungi (AMF) are considered ecosystem engineers, but the interactions of their mycelium with their immediate surroundings are largely unknown. In this study, we used microfluidic chips, simulating artificial soil structures, to study foraging strategies and habitat modification of Rhizophagus irregularis symbiotically associated to carrot roots. AMF hyphae foraged over long distances in nutrient-void spaces, preferred straight over tortuous passages, anastomosed and showed strong inducement of branching when encountering obstacles. We measured bi-directional transport of cellular content inside active hyphae and documented strategic allocation of biomass within the mycelium via cytoplasm retraction from inefficient paths. R. irregularis modified pore-spaces in the chips by clogging pores with irregularly shaped spores. We suggest that studying AMF hyphal behaviour in spatial settings can explain phenomena reported at bulk scale such as AMF modification of water retention in soils. The use of microfluidic soil chips in AMF research opens up novel opportunities to study their ecophysiology and interactions with both biotic and abiotic factors.

The European Alps are experiencing more than twice the increase in air temperature observed in the rest of the world. Thus, the treeline ecotone, and the unique habitats above it, offer a preview of drastic changes in plant and animal communities. However, our knowledge about climate change impacts on microbial diversity belowground is scarce. Here we investigate how upslope shift of the treeline ecotone, associated with changes in soil nutrient content, temperature and precipitation, will influence alpine ectomycorrhizal (EM) communities of Dryas octopetala, Bistorta vivipara and Salix herbacea across different habitat types in the Alps. We also assessed the degree of EM community taxonomic composition turnover in these habitats across three different climatic projections for 2040 and 2070. Our results indicate that the specialized EM fungal communities from snowbed habitats will be mostly negatively influenced under the current trajectory of environmental shifting predicted for the region. In contrast, fungi from the treeline ecotone, having wider niches, will be positively influenced by future climate and extend upwards. In addition, our predictions of EM community turnover for putative future climatic scenarios revealed high rates of turnover across the entire alpine region. This, together with glacier retreats, will aid colonization of alpine snowbed habitats by new EM plants and associated fungi, bringing additional pressures on local mycorrhizas and likely leading to fungal species extinctions.

Nitrogen (N) addition not only promotes the restoration of degraded grasslands, but also threatens ecosystem functioning through the loss of species richness. Thus, a deep understanding of the effect of N addition on the richness of key organisms in restored grasslands is critical to sustainably restoring degraded grasslands. We conducted a 4-year N addition experiment to investigate the response of both plant and arbuscular mycorrhizal (AM) fungal richness to the combined addition of ammonium (Am) and nitrate (Ni) in a revegetated grassland rehabilitated (with a focus on restoration) on the Qinghai–Tibet Plateau. Both nitrogen forms were added at three levels: 0, 10, and 20 g N m⁻² year⁻¹. By itself, Ni addition of 20 g N m⁻² year⁻¹ (Ni20) reduced both plant and AM fungal richness, while Am addition of 20 g N m⁻² year⁻¹ (Am20) had no significant effect on them. However, when Ni and Am were combined, only Ni20 plus Am20 among all combinations reduced both plant and AM fungal richness. Both soil nitrate-N and plant species richness jointly drove changes in AM fungal richness, but plant species richness was the main factor affecting AM fungal richness under N addition. Our results suggest that minimizing the loss of AM fungi caused by plant species loss resulting from N addition is a key means to sustainably restore degraded grasslands.

Complex interactions involving soil physicochemical parameters and plant-associated microbial communities determine crop health. In Vietnam, this process is poorly understood in the context of black pepper production. Specifically, there is a dearth of information for improving the suppression of pathogenic fungi. Understanding the environmental dynamics influencing the distribution of these pathogens would facilitate the development and use of biological agents in black pepper pathogen management. Here, the molecular profiles of fungal communities from the rhizosphere of healthy and unhealthy Vietnamese black pepper orchards and their relationships were determined. Additionally, co-occurrence analyses with a previously constructed bacterial dataset identified taxa indicative of soil suppression. Alpha diversity of total fungi was influenced by only environmental factors, while that of arbuscular mycorrhizal fungi was more responsive to orchard health state. Glomus sp., Rhizophagus sp., Purpureocillium sp. and Plectosphaerella sp. were the most responsive genera to orchard health state. Potential fungal pathogens were more prevalent in the unhealthy orchards. Co-occurrence network analyses revealed that unhealthy orchards were less connected, had longer path distance and were missing putative pathogen-to-biocontrol interactions common in the healthy orchards. Soil electrical conductivity and potassium may be key factors in differentiating fungal communities of unhealthy from healthy orchards. This work highlights important microbial species and environmental considerations critical to improved black pepper management strategies.

Epiphytic lichens are considered sensitive indicators of environmental change. Excess water is known to depress their photosynthesis, but the effect of long-lasting rain on species richness of epiphytic lichens is rarely reported. By annually repeated records of macrolichen species richness on tree trunks over a period of 33 years that included one long rainy season in year 2000, a strong decline in macrolichen richness on tree trunks was detected after the unusually wet autumn. Afterwards, the lichen richness slowly recovered, but had not yet fully recovered 19 years after the dieback. Thereby, long rainy periods can cause lasting depression in epiphytic lichen richness, and continuous rain should be considered a possible threat to lichens in regions like northern Europe where global change predicts enhanced rainfall frequency.

Understanding the effects of windstorm disturbances on soil communities is of pivotal importance. Oomycete communities host some species of plant pathogens, which might affect the forest regeneration after the disturbance. Here, we sampled a large area to compare three habitats (e.g., windfall, old clearings, and undisturbed spruce forest) along a gradient of elevation and slope. We used an eDNA metabarcoding approach targeting the rps10 gene. Our results showed that both wind disturbance and underlying topography can influence the richness of oomycetes. Higher richness of oomycetes was found in disturbed sites and high steepness. We did not find differences in community composition among the different habitat types at the landscape scale. However, we found significant differences among drainage basins at larger spatial scale. Our work contributed to the understanding of the oomycete communities in Norway spruce forests affected by wind disturbance.

Through species-specific effects on plants, pathogens play a key role in structuring plant communities. A change in abiotic context, such as those mediated by climate change, may alter plant communities through changes in the specificity of plant-pathogen interactions. To test how water availability influenced the specificity of plant-pathogen interactions, we grew paired congeners of three native and three nonnative coastal prairie plant species with or without a pathogenic soil fungus, Fusarium incarnatum-equiseti species complex 6 b, under low, average, and high water treatments. Across the plant species tested, the Fusarium treatment had stronger negative and species-specific effects on plant biomass at high water availability than low water availability. If generalizable, our results suggest that stronger and more species-specific pathogen effects could drive changes in plant community composition in wetter conditions, but plant-pathogen interactions may be less important for plant community structure in drier conditions.

Accurately identifying entomopathogenic fungi is crucially important, but the current approach of analysing four genes might not provide sufficient resolution. In this study, we investigated the different resolution provided by multilocus phylogenies and approaches based on whole genome sequence data. Fungi were isolated from soil samples that were collected from five different vegetation types (dry sclerophyll forest, agricultural grassland, rainforest, suburban parkland, and sugar cane fields) and across four different suburban soil habitat types in southeast Queensland. Three different agricultural pests were used as live baits, cotton stainer bug, diamondback moth, and rust-red flour beetle. Whole-genome sequencing was conducted for all 83 isolates recovered, and the ITS2 region was extracted from the genome assemblies to make initial species identifications with the UNITE database. We also extracted tef1a 3′, tef1a 5’, rpb1 and rpb2 genes from the Metarhizium genomes and the bloc, tef1a and rpb1 genes from Beauveria genomes to construct multilocus phylogenies and obtain species identification. To investigate the genetic relationships across 14 isolates of Beauveria bassiana and (independently) across 43 isolates of Metarhizium based on whole-genome data, we genotyped single nucleotide polymorphism (SNP) markers and conducted principal components analysis on the whole-genome SNP data. The multilocus methods identified isolates to species more precisely than ITS2, except in the one unresolved clade in the Metarhizium phylogeny. The whole-genome approach identified more genetic clusters than the multilocus phylogenies identified species among the isolates, and the morphological results correlated with some of the genetic clusters, so they likely represent distinct species not detected by the other methods. The genetic clusters were not associated with vegetation type or bait insect species. This is the first comparison of the resolution of multilocus phylogenetics with that of whole-genome SNP data for these genera. We suggest how the genetic clusters identified here may be investigated further to determine whether they represent unrecognised species within these groups.

The amphibian skin pathogen Batrachochytrium dendrobatidis (Bd) has caused an ongoing biodiversity crisis, including in the locally endangered Colorado boreal toad (Anaxyrus boreas). Although researchers have investigated the bacteria living on amphibian skin and how they interact with Bd, there is less information about fungal community members. This study describes (1) the diversity of culturable fungi from boreal toad skin, (2) which subset of these isolates is Bd-inhibitory, and (3) how Bd affects these isolates' growth and morphology. Most isolates were from the orders Capnodiales, Helotiales, and Pleosporales. Of 16 isolates tested for Bd-inhibition, two from the genus Neobulgaria and three from Pseudeurotium inhibited Bd. Fungal growth in co-culture with Bd varied with weak statistical support for Neobulgaria sp. (isolate BTF_36) and cf Psychrophila (isolate BTF_60) (p-values = 0.076 and 0.092, respectively). Fungal morphology remained unchanged in co-culture with Bd, however, these results could be attributed to low replication per isolate. Nonetheless, two fungal isolates’ growth may have been affected by Bd, implying that fungal growth changes in Bd co-culture could be a variable worth measuring in the future (with higher replication). These findings add to the sparse but growing literature on amphibian-associated fungi and suggest further study may uncover the relevance of fungi to amphibian health and Bd infection.

A frequently ignored but critical aspect of microbial dispersal is survival in the atmosphere. We exposed spores of two closely related, morphologically dissimilar, and economically important fungal pathogens to typical atmospheric environments and modeled their movement in the troposphere. Alternaria solani conidia are nearly 10 times larger than A. alternata conidia, but in our experiments, most died within 24 h, while over half of A. alternata conidia remained viable on day 12. Next, we modeled the movement of spores across North America. We predict 99% of the larger A. solani conidia settle within 24 h, with a maximum dispersal distance of 100 km. By contrast, most A. alternata conidia remain airborne for more than 12 days, and dispersal over long distances(2000 km) is likely. Counterintuitively, the larger A. solani conidia survive poorly, as compared to smaller A. alternata conidia, but also land sooner and move over shorter distances.