Fungal Ecology最新文献

Although the anthropogenic decline in atmospheric carbon stable isotope ratios (δ¹³C) over the last 150 years (termed the Suess effect) is well-studied, how different terrestrial trophic levels and modes reflect this decline remains unresolved. To evaluate the Suess effect as an opportunistic tracer of terrestrial forest carbon cycling, this study analyzed the δ¹³C in herbarium specimens collected in Minnesota, USA from 1877 to 2019. Our results suggest that both broadleaf trees and ectomycorrhizal fungi relied on recent photosynthate to produce leaves and sporocarps, while saprotrophic fungi on average used carbon fixed from the atmosphere 32–55 years ago for sporocarp construction. The δ¹³C values of saprotrophic fungal collections were also sensitive to the age of their plant carbon substrate, with sporocarps of twig specialists tracking changes in atmospheric δ¹³C more closely than saprotrophs growing on logs. Collectively, this study indicates that natural history collections can quantitatively track carbon cycling among plants and fungi over time.

Mycelium-bound composites are normally made of discrete lignocellulosic substrate elements bound together by filamentous fungal hyphae. They can be formed into bespoke components of desired geometries by moulding or extrusion. Mycelium-bound composites with live fungi have been shown to be electrically conductive with memfractive and capacitive attributes. They can be integrated into electrical circuits with nonlinear electrical properties. Advancing fungal electronics, we studied the AC conductive properties of mycelium-bound composites and fungal fruit bodies at higher frequencies across three overlapping bands; 20 Hz to 300 kHz, 10 Hz to 4 MHz and 50 kHz to 3 GHz. Measurements indicate that mycelium-bound composites typically act as low-pass filters with a mean cut-off frequency of ∼500 kHz; with ∼−14 dB/decade roll-off, and mean attenuation across the pass band of $<$1 dB. Fruiting bodies have between one or two orders of magnitude lower mean cut-off frequency (5 kHz–50 kHz depending on species); with −20 dB/decade to −30 dB/decade roll-off, and mean attenuation across the pass band of $<$3 dB. The mechanism for the frequency-dependent attenuation is uncertain; however, the high water content, which is electrically conductive due to dissolved ionisable solids is probably a key factor. The potential for mycelium-bound composites and fruiting bodies in analog computing is explored.

Low temperatures near alpine treelines limit microbial release of soil nitrogen and tree growth. Ectomycorrhizal fungi can increase nitrogen supply for trees, but the importance of this exchange of carbon for nitrogen at the treeline remains unclear. Our bomb radiocarbon measurements indicated that trees transferred carbon fixed <2 years previously to fungi. The allocated carbon likely included sugars involved in starch synthesis, as δ¹³C in fungal caps closely resembled that of fine-root starch. Mass balance of nitrogen isotopes along the plant-fungi-soil continuum revealed that Larix decidua trees relied less on fungal nitrogen (0–35% of N uptake), compared to Pinus mugo trees (up to 41%). We estimated that treeline trees allocate up to 18% of photoassimilates to fungi. Our findings suggest that at alpine treelines, trees allocate to ectomycorrhizal symbionts relatively high amount of carbon compared to the reverse nitrogen flux, but the exact exchange is tree species-specific.

To identify the functional advantages of hyphal connections in fungal mycelial networks, we evaluated the wood decaying abilities of the mycelia of a saprotrophic basidiomycete, Phanerochaete velutina, in soil dishes with wood baits. The dishes were surrounded by water, allowing the mycelia to access water. Dishes with two or three baits were placed adjacent to or distant from each other, representing the ease of creating hyphal bridges between the two dishes. After 8 months of incubation, the weight loss of the wood bait was significantly larger in the adjacent pairs of dishes compared to the distant pairs. Mycelia in the adjacent dishes had higher chances to access the water and thus increase water content of the wood, which was the primary factor related to wood weight loss. These results suggest that hyphal connections increase decay ability of P. velutina possibly due to water transfer across the mycelial network.

The majority of studies exploring the ecology of saprotrophic fungi have worked with individual logs as homogenous sampling units, neglecting the presence of microhabitats and inner complexity. Based on close to 7000 sporocarp records of more than 450 fungal taxa from 134 decaying beech logs we investigated microhabitat preferences in macrofungi and linked these to sporocarp traits. The respective microhabitats were defined by the local wood decay stage, vertical position on the fallen log and special habitat features (hollows, fracture surfaces, woody material fallen from the log). We found microhabitat associations to be non-random in relation to fungal community composition and sporocarp morphology, indicating an evolutionary link between dead wood niche and sporocarp morphology. While log-level fungal species richness peaked at intermediate decay stages, taxa with significant indicator values were skewed towards early and late decay stages, when defined at microhabitat decay level. This suggests that the commonly found peak in fungal species richness on dead logs in intermediate decay stages expresses a peak in niche diversity rather than a peak in taxa decay stage preferences.

Free-living saprotrophic fungi and symbiotic mycorrhizal fungi affect organic matter dynamics differently because of contrasting ecological adaptations. We investigated how mass-loss, C:N-ratio and stable isotope dynamics of leaf litter and humus substrates depended on presence of living tree roots and associated fungal communities in a forest-to-tundra ecotone over three years. Litter mass-loss was stimulated by tree roots, contrary to a Gadgil effect. Increases in the litter nitrogen pool and δ¹⁵N suggested import of nitrogen from deeper soil by the dominating saprotrophic fungi. Over time, humus first lost, then gained, mass, and corresponding shifts in δ¹⁵N and δ¹³C suggested fluctuating pools of fine roots and fungal mycelium. Ectomycorrhizal tree roots consistently reduced longer-term humus mass-gain, counteracting positive effects of ericoid roots and associated fungi. Across all substrates, mass dynamics correlated with the balance between ectomycorrhizal and litter-saprotrophic fungi, both linked to mass-loss, and ericaceous shrubs and associated fungi, linked to mass-gain.

Wood-decay fungi are adapted to growth under different climate conditions and on various host tree species, but little is known about intraspecific variation in growth, substrate specificity and decay rates under different climatic conditions. Such knowledge is relevant to understand how wood-decay fungi will respond to climate change. Here, we investigate whether populations of the widespread brown-rot fungus Fomitopsis pinicola grow at different rates under different temperatures and water availabilities and whether the decay rate of the two wood substrates, Alnus incana and Picea abies, differs across populations. We isolated 72 cultures from fruit bodies collected in nine geographic localities across Norway, representing different climate conditions and substrates. We conducted in vitro growth experiments to assess the level of intraspecific phenotypic variability in temperature-dependent growth. All populations showed a strong but similar response in mycelial growth rates to different temperatures and water potentials. There were no consistent differences between populations in growth rates across temperatures, but larger variation between populations at the higher temperatures. Similarly, we observed no significant differences in wood decay rates across the nine populations and no signs of substrate specific adaptation to P. abies and A. incana. Our results indicate that local adaptation to different climates or substrates, as revealed by in vitro growth experiments, has to a limited extent, taken place during the few thousand years Fomitopsis pinicola has been present in this area.

All vascular plants contain communities of endophyte fungi within their foliar tissues. These fungi can act as plant bodyguards and disrupt the efficacy of weed biological control agents, yet studies of invasive plant biology hardly ever consider the background endophyte communities. Here, we investigated the factors that affect the structure of cultivable endophyte communities in the highly invasive weed Impatiens glandulifera. We found that community composition varies according to location, but that seasonal accumulation patterns of endophytes are similar between sites. Biotic factors influencing endophytes include arbuscular mycorrhizal fungi, insect herbivores and plant pathogens. Endophyte species richness per plant was consistently low compared with other herbaceous plants and communities appear to be a random sub-set of the available species pool, with the plant acting as a strong filter of species. This information should enable community structure to be modelled and manipulated, making biological control of this weed more effective.

Phyllosphere fungi exhibit a wide range of species and play a pivotal role in island ecosystem biodiversity. They bolster plant resilience against diseases and environmental stresses, facilitate the decomposition of organic materials, and enhance nutrient exchange between plants and their surroundings. Despite extensive research on island biogeography pertaining to flora and fauna, the assembly of phyllosphere fungal communities has not been thoroughly explored. This study addresses this gap by employing high-throughput sequencing to examine phyllosphere fungi associated with three island plant species (Messerschmidia argentea, Morinda citrifolia, and Suriana maritima) across 13 islands in the Xisha Islands region. Our findings reveal significant variances in fungal α-diversity and community composition across different islands, plant species, and functional guilds. The variation in fungal α-diversity was notably correlated with the geographical distance from the mainland and a satellite-derived vegetation index, while the Bray-Curtis similarity in fungal communities was primarily influenced by the geographical distance between islands. Stochastic elements, particularly dispersal limitation and drift, were identified as major drivers of fungal community assembly. Furthermore, we observed that island size impacts the distribution of potential keystone species and their co-occurrence patterns within the fungal groups. Intriguingly, host vegetation was found to exert a stronger selective influence on phyllosphere fungi than island characteristics. These results provide valuable insights into the complex ecological interactions and processes governing fungal communities in isolated and unique environmental settings.

This study evaluated the growth-promoting action of 16 isolates of the entomopathogenic fungal genus Metarhizium spp., representing 14 from the native pastures and two commercial isolates, on the forage grass Urochloa brizantha, via drench application to seeds. Multivariate analysis of plant height, length of the longest leaf and root, and dry and fresh weight of leaves and roots indicated the most promising isolates, five from native pastures (CEPAF_ENT25, CEPAF_ENT26, CEPAF_ENT27, CEPAF_ENT42, and CEPAF_ENT59) and one commercial (IBCB 425), all isolates of Metarhizium anisopliae. Except for isolate CEPAF_ENT59, there was a positive correlation between growth parameters of U. brizantha with the contents of chlorophyll a and b and carotenoids and with the contents of N, P, and Zn in the leaves. Endophytic colonization tests indicated the presence of Metarhizium spp. in all plant parts, most frequently in the stems. Furthermore, the selected isolates of Metarhizium spp. were recovered from the cultivation substrate and positively affected the germination and initial growth of U. brizantha. Thus, the most promising isolates have potential for application to seeds of U. brizantha.