Ectomycorrhizal fungi have larger fruit bodies than saprotrophic fungi

Currently we have only a limited understanding of the evolutionary and ecological significance of reproductive traits of fungi. We compared data on fruit body size, spore size and shape between saprotrophic and mutualistic (ectomycorrhizal) fungi in Northern and Central Europe. Lifestyle and reproductive traits showed strong phylogenetic signals. A phylogenetically informed analysis demonstrated that saprotrophs produce on average smaller fruit bodies than mutualistic species. The two guilds, however, do not differ in spore size. Overall this suggests that fruit bodies of ectomycorrhizal fungi produce on average more spores than saprotrophic fungi. We argue that this difference is related to resource availability: ectomycorrhizal fungi receive carbon from their hosts and, therefore, evolution favours large fruit bodies, whereas the fruit body size of saprotrophic fungi might have responded to resource availability and the distribution and size of resource patches.     

Spore wall traits of ectomycorrhizal and saprotrophic agarics may mirror their distinct lifestyles

Although fungal spores are tiny compared to plant seeds, their morphological variability is enormous, which points toward selective forces. We investigated the frequency of ornamentation, thick walls, pigmentation and germ pores of spores of ectomycorrhizal and saprotrophic agarics. We hypothesised that these traits are shaped by the needs of these distinct lifestyles. All traits showed a strong phylogenetic signal; we therefore applied a phylogenetically informed statistical analysis. There was a significantly higher occurrence of spore ornamentation in ectomycorrhizal agarics and a higher occurrence of thick-walled spores in saprotrophic agarics. The interplay between thick-walled and pigmented spores and the occurrence of germ pores was only significant for saprotrophs. We argue that ornamentation is probably important to ectomycorrhizal fungi for dispersal by soil invertebrates, whereas pigmented thick walls and germ pores would be more advantageous for predominantly r-selected saprotrophic agarics exposed to hazardous environments and in need of quick germination success.     

Trait‐dependent distributional shifts in fruiting of common British fungi

Despite the dramatic phenological responses of fungal fruiting to recent climate warming, it is unknown whether spatial distributions of fungi have changed and to what extent such changes are influenced by fungal traits, such as ectomycorrhizal (ECM) or saprotrophic lifestyles, spore characteristics, or fruit body size. Our overall aim was to understand how climate and fungal traits determine whether and how species‐specific fungal fruit body abundances have shifted across latitudes over time, using the UK national database of fruiting records. The data employed were recorded over 45 yr (1970–2014), and include 853 278 records of Agaricales, Boletales and Russulales, though we focus only on the most common species (with more than 3000 records each). The georeferenced observations were analysed by a Bayesian inference as a Gaussian additive model with a specification following a joint species distribution model. We used an offset, random contributions and fixed effects to isolate different potential biases from the trait‐specific interactions with latitude/climate and time. Our main aim was assessed by examination of the three‐way‐interaction of trait, predictor (latitude or climate) and time. The results show a strong trait‐specific shift in latitudinal abundance through time, as ECM species have become more abundant relative to saprotrophic species in the north. Along precipitation gradients, phenology was important, in that species with shorter fruiting seasons have declined markedly in abundance in oceanic regions, whereas species with longer seasons have become relatively more common overall. These changes in fruit body distributions are correlated with temperature and rainfall, which act directly on both saprotrophic and ECM fungi, and also indirectly on ECM fungi, through altered photosynthate allocation from their hosts. If these distributional changes reflect fungal activity, there will be important consequences for the responses of forest ecosystems to changing climate, through effects on primary production and nutrient cycling.     

Assembly processes of trophic guilds in the root mycobiome of temperate forests

Root‐associated mycobiomes (RAMs) link plant and soil ecological processes, thereby supporting ecosystem functions. Understanding the forces that govern the assembly of RAMs is key to sustainable ecosystem management. Here, we dissected RAMs according to functional guilds and combined phylogenetic and multivariate analyses to distinguish and quantify the forces driving RAM assembly processes. Across large biogeographic scales (>1,000 km) in temperate forests (>100 plots), RAMs were taxonomically highly distinct but composed of a stable trophic structure encompassing symbiotrophic, ectomycorrhizal (55%), saprotrophic (7%), endotrophic (3%) and pathotrophic fungi (<1%). Taxonomic community composition of RAMs is explained by abiotic factors, forest management intensity, dominant tree family (Fagaceae, Pinaceae) and root resource traits. Local RAM assemblies are phylogenetically clustered, indicating stronger habitat filtering on roots in dry, acid soils and in conifer stands than in other forest types. The local assembly of ectomycorrhizal communities is driven by forest management intensity. At larger scales, root resource traits and soil pH shift the assembly process of ectomycorrhizal fungi from deterministic to neutral. Neutral or weak deterministic assembly processes are prevalent in saprotrophic and endophytic guilds. The remarkable consistency of the trophic composition of the RAMs suggests that temperate forests attract fungal assemblages that afford functional resilience under the current range of climatic and edaphic conditions. At local scales, the filtering processes that structure symbiotrophic assemblies can be influenced by forest management and tree selection, but at larger scales, environmental cues and host resource traits are the most prevalent forces.     

Fine‐scale spatiotemporal dynamics of fungal fruiting: prevalence,amplitude, range and continuity

Despite the critical importance of fungi as symbionts with plants, resources for animals, and drivers of ecosystem function, the spatiotemporal distributions of fungi remain poorly understood. The belowground life cycle of fungi makes it difficult to assess spatial patterns and dynamic processes even with recent molecular techniques. Here we offer an explicit spatiotemporal Bayesian inference of the drivers behind spatial distributions from investigation of a Swiss inventory of fungal fruit bodies. The unique inventory includes three temperate forest sites in which a total of 73 952 fungal fruit bodies were recorded systematically in a spatially explicit design between 1992 and 2006. Our motivation is to understand how broad‐scale climate factors may influence spatiotemporal dynamics of fungal fruiting within forests, and if any such effects vary between two functional groups, ectomycorrhizal (ECM) and saprotrophic fungi. For both groups we asked: 1) how consistent are the locations of fruiting patches, the sizes of patches, the quantities of fruit bodies, and of prevalence (occupancy)? 2) Do the annual spatial characteristics of fungal fruiting change systematically over time? 3) Are spatial characteristics of fungal fruiting driven by climatic variation? We found high inter‐annual continuity in fruiting for both functional groups. The saprotrophic species were characterised by small patches with variable fruit body counts. In contrast, ECM species were present in larger, but more distinctly delimited patches. The spatial characteristics of the fungal community were only indirectly influenced by climate. However, climate variability influenced overall yields and prevalence, which again links to spatial structure of fruit bodies. Both yield and prevalence were correlated with the amplitudes of occurrence and of fruit body counts, but only prevalence influenced the spatial range. Summarizing, climatic variability affects forest‐stand fungal distributions via its influence on yield (amount) and prevalence (occupancy), whereas fungal life‐history strategies dictate fine‐scale spatial characteristics.     

Colonizing success of saprotrophic and ectomycorrhizal basidiomycetes on islands

The biodiversity of saprotrophic and ectomycorrhizal basidiomycetous macrofungi growing on seven islands in central Japan were compared to examine colonizing success within the context of island biogeography theory. Two hypotheses were tested: that the number of the fungal species depends on island area and that the slope of the species-area curve for saprotrophic and ectomycorrhizal macrofungi differ in response to differences in their nutritional requirements. Data for the number of species that were identified based on sporocarps closely fit the conventional species-area curve. The slopes of the species-area curve for saprotrophic fungi (0.316) and ectomycorrhizal fungi (0.469) were similar to those reported for insects and birds, and plants on other archipelagos, respectively. In addition species-area curve data showed that ectomycorrhizal fungi colonized only islands > 630 m(2). While the species composition of saprotrophic fungi found on any pair of islands was positively correlated to the ratio of the areas of the island pair being compared (smaller/larger), no such relationship was observed for ectomycorrhizal fungi. Conversely similar ectomycorrhizal fungi, mostly those belonging to the genera Amanita, Inocybe, Boletellus and Russula, were found on pairs of islands with similar vegetation in the same geographic region. These results suggested that the colonizing success by ectomycorrhizal fungi is limited by host plant diversity, which is lower on smaller islands, instead of restricted immigration resulting from limited spore dispersal ability.     

Mutualistic interactions on a knife-edge between saprotrophy and pathogenesis

Saprophytic, ectomycorrhizal (ECM) and pathogenic fungi play a key role in carbon and nutrient cycling in forest ecosystems. Whereas more than 50 genomes of saprotrophic and pathogenic fungi have been published, only two genomes of ECM fungi, Laccaria bicolor and Tuber melanosporum, have been released. Comparative analysis of the genomes of biotrophic species highlighted convergent evolution. Mutualistic and pathogenic biotrophic fungi share expansion of genome size through transposon proliferation and common strategies to avoid plant detection. Differences mainly rely on nutritional strategies. Such analyses also pinpointed how blurred the molecular boundaries are between saprotrophism, symbiosis and pathogenesis. Sequencing of additional ECM species, as well as soil saprotrophic fungi, will facilitate the identification of conserved traits for ECM symbiosis and those leading to the transition from white-rotting and brown-rotting to the ECM lifestyle.     

A strong species-area relationship for eukaryotic soil microbes: island size matters for ectomycorrhizal fungi

While the effects of habitat size and isolation have been successfully studied for macro-organisms, there is currently debate about their relative importance in explaining patterns of microbial species richness. In this study, we examine the species richness of a dominant group of eukaryotic soil microbes, ectomycorrhizal fungi, on 'tree islands' of constant age and host composition that range in size from < 10 to > 10 000 m². Our results show that ectomycorrhizal species richness is significantly reduced on smaller and more isolated tree islands, and the species–area slope that we observe (0.20–0.23) is similar to average slopes reported for macro-organisms. Additionally, species' occurrence patterns across tree islands and investment trends in fungal fruit bodies suggest that a trade-off between competition and dispersal could play an important role in structuring ectomycorrhizal assemblages.     

Host plants and edaphic factors influence the distribution and diversity of ectomycorrhizal fungal fruiting bodies within rainforests from Tshopo,Democratic Republic of the Congo

Ectomycorrhizal fungi constitute an important component of forest ecosystems that enhances plant nutrition and resistance against stresses. Diversity of ectomycorrhizal (EcM) fungi is, however, affected by host plant diversity and soil heterogeneity. This study provides information about the influence of host plants and soil resources on the diversity of ectomycorrhizal fungal fruiting bodies from rainforests of the Democratic Republic of the Congo. Based on the presence of fungal fruiting bodies, significant differences in the number of ectomycorrhizal fungi species existed between forest stand types (p < 0.001). The most ectomycorrhizal species‐rich forest was the Gilbertiodendron dewevrei‐dominated forest (61 species). Of all 93 species of ectomycorrhizal fungi, 19 demonstrated a significant indicator value for particular forest stand types. Of all analysed edaphic factors, the percentage of silt particles was the most important parameter influencing EcM fungi host plant tree distribution. Both host trees and edaphic factors strongly affected the distribution and diversity of EcM fungi. EcM fungi may have developed differently their ability to successfully colonise root systems in relation to the availability of nutrients.     

The effect of pH on the growth of saprotrophic and ectomycorrhizal ammonia fungi in vitro

Some saprotrophic and ectomycorrhizal fungi produce reproductive structures, preferably in slightly alkaline to neutral forest soil. This research examines the growth of these "ammonia fungi" in liquid medium at various pH values. In the first experiment, the capacity of six buffers was examined to select appropriate buffers for stabilizing pH in the neutral-to-alkaline range by culture of three species of the ammonia fungi in media initially adjusted to pH 7, 8 or 9. The highest buffering capacity was shown in 2-(N-morpholino) ethanesulfonic acid (MES) at pH 7, and N, N-bis (2-hydroxyethyl) glycine (Bicine) and N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) at pH 8 and 9. In the second experiment, the growth of 15 strains of both saprotrophic and ectomycorrhizal ammonia fungi was tested on the medium initially adjusted to pH 3, 4, 5, 6 or 7 with MES, or to pH 8 or 9 buffered with Bicine. Many of the saprotrophic species grew well at pH 7 or 8; the ectomycorrhizal species showed optimum growth at pH 5 or 6. The pH suitable for the in vitro growth of these fungi was correlated with the pH of forest soil where these fungi occur.     

Geographical variation in reproductive investment across avian assemblages in Europe: effects of environmental drivers differ between altricial and precocial species

Reproductive traits provide information about the ways by which available resources are allocated during breeding. We tested for environmental drivers of large scale geographical patterns in assemblage mean clutch size, number of broods and overall reproductive investment per breeding season in European birds. We combined data about geographical distribution with published information about reproductive traits, and calculated mean trait values for avian assemblages occurring in 50 × 50 km grid cells. In total, we employed data from 499 species and 2059 assemblages. As the time available for breeding and the amount of food limit the reproductive effort, we related the geographical variation in reproductive traits to the length of breeding season, normalized difference vegetation index (NDVI) as a surrogate of resource availability, and its seasonality. Geographical patterns in traits may differ between reproductive modes, thus we performed the analyses separately for altricial Passerines (n = 203) and precocial non‐passerine species (n = 164) and controlled for the effect of taxonomy. Large clutches dominated in areas with high NDVI and, in precocial birds, also in areas with high annual seasonality and a long breeding season. High number of broods and high overall reproductive investment dominated in areas with a long breeding season, and high number of broods was found also in areas with low annual seasonality, but only in precocial species. High overall reproductive investment dominated in highly productive areas and also in areas with low annual seasonality in both groups. The increase in reproductive investment is caused mostly by an increase in the number of broods related to the length of season and partly by increase in clutch size related to NDVI. We found a negative correlation between clutch size and the number of broods in Passerines, which might suggest a trade‐off between these traits. Processes behind trait patterns differ between altricial and precocial species.     

First report of the ectomycorrhizal status of boletes on the Northern Yucatan Peninsula, Mexico determined using isotopic methods

Despite their prominent role for tree growth, few studies have examined the occurrence of ectomycorrhizal fungi in lowland, seasonally dry tropical forests (SDTF). Although fruiting bodies of boletes have been observed in a dry tropical forest on the Northern Yucatan Peninsula, Mexico, their occurrence is rare and their mycorrhizal status is uncertain. To determine the trophic status (mycorrhizal vs. saprotrophic) of these boletes, fruiting bodies were collected and isotopically compared to known saprotrophic fungi, foliage, and soil from the same site. Mean δ¹⁵N and δ¹³C values differed significantly between boletes and saprotrophic fungi, with boletes 8.0‰ enriched and 2.5‰ depleted in ¹⁵N and ¹³C, respectively relative to saprotrophic fungi. Foliage was depleted in ¹³C relative to both boletes and saprotrophic fungi. Foliar δ¹⁵N values, on the other hand, were similar to saprotrophic fungi, yet were considerably lower relative to bolete fruiting bodies. Results from this study provide the first isotopic evidence of ectomycorrhizal fungi in lowland SDTF and emphasize the need for further research to better understand the diversity and ecological importance of ectomycorrhizal fungi in these forested ecosystems.     

Fruit production is influenced by tree size and size‐asymmetric crowding in a wet tropical forest

In tropical forest communities, seedling recruitment can be limited by the number of fruit produced by adults. Fruit production tends to be highly unequal among trees of the same species, which may be due to environmental factors. We observed fruit production for ~2,000 trees of 17 species across 3 years in a wet tropical forest in Costa Rica. Fruit production was modeled as a function of tree size, nutrient availability, and neighborhood crowding. Following model selection, tree size and neighborhood crowding predicted both the probability of reproduction and the number of fruit produced. Nutrient availability only predicted only the probability of reproduction. In all species, larger trees were more likely to be reproductive and produce more fruit. In addition, number of fruit was strongly negatively related to presence of larger neighboring trees in 13 species; presence of all neighboring trees had a weak‐to‐moderate negative influence on reproductive status in 16 species. Among various metrics of soil nutrient availability, only sum of base cations was positively associated with reproductive status, and for only four species. Synthesis Overall, these results suggest that direct influences on fruit production tend to be mediated through tree size and crowding from neighboring trees, rather than soil nutrients. However, we found variation in the effects of neighbors and nutrients among species; mechanistic studies of allocation to fruit production are needed to explain these differences.     

Ecological and trophic differentiation of fungal diversity in Aksu-Zhabagly Nature Reserve (Kazakhstan)

Two fungal-like organisms (class Oomycetes) and 263 species of fungi from 111 genera, 42 families, 23 orders, and 7 classes have been found on the territory of Aksu-Zhabagly Nature Reserve. Twenty-two species are found for the first time. The vast majority of species are parasitic (202 species), 56 species belong to saprotrophs, and 7 to symbiotrophs. Classes Taphrinomycetes, Urediniomycetes, and Ustilaginomycetes are represented exclusively by parasites. There have been found 21 saprotrophic, 27 parasitic, and 4 symbiotrophic species in the class Ascomycetes. The most numerous group in the class Basidiomycetes is the group of humus saprotrophs; it contains 15 species. Groups of litter saprotrophs and parasites contain four species each, symbiotrophic species have three species, coprotrophs and xylotrophs have two species each, and litter and humus saprotrophs have one species each. Anamorphic fungi are represented by 91 parasitic and 11 saprotrophic species. In comparison with closely located Sairam-Ugam National Park and the Karatau Nature Reserve, the mycobiota of Aksu-Zhabagly is characterized by a significant number of species in the classes Basidiomycetes, Urediniomycetes, Hyphomycetes, and Coelomycetes. Thirty-one species are common to these protected areas. The most numerous group is parasites.     

Species traits predict assembly of mayfly and stonefly communities along pH gradients

Much recent ecological research has centred on the interrelations between species diversity and ecological processes. In the present study, I show how species traits may aid in comprehending ecology by studying the link between an environmental variable and functional traits. I examined the composition of species traits with a theoretically underpinned relationship to ecological processes along a pH gradient. I focused on body size, reproductive output, life cycle length and feeding habit of mayflies and stoneflies. In mayfly assemblages, I found smaller body size, greater reproductive output, faster life cycles and a larger proportion of gathering collectors and scrapers with increasing pH. In stonefly assemblages, I found smaller body size, greater reproductive output and faster life cycles at sites with a history of long-term natural acidification, but no clear trends in feeding habits and in most traits where acidification is anthropogenic. The results suggest that mayflies and stoneflies exhibit different ecological functions following different ecological strategies. Mayflies follow an opportunistic strategy relative to stoneflies, likely facilitating high rates of ecological processes with respect to the autotrophic resource base at neutral sites. Relative to mayflies, stoneflies follow an equilibrium strategy contributing to ecological functioning in heterotrophic ecosystems and likely maintaining heterotrophic processes despite the erosion of species diversity in response to acidification. The rules governing an ecological community may be more readily revealed by studying the distribution of species traits instead of species diversity; by studying traits, we are likely to improve our understanding of the workings of ecological communities.     

Ectomycorrhizal and wood-decay macromycete communities along development stages of managed Pinus patula stands in Southwest Mexico

This study used fruit body surveys to evaluate the diversity and distribution of ectomycorrhizal and wood-decay macromycetes along developing stages of stands artificially reforested with Pinus patula in Southern Mexico. Three stand ages were selected: 1, 11, and 60 y old. Macromycetes were collected from June to October 2016 in 0.1 ha plots per stand age. A total of 106 taxa were recorded, 63 ectomycorrhizal and 43 wood-decay fungi. The highest diversity of ectomycorrhizal fungi was in 11-y stands, and 11- and 60-y stands had similar species composition. Wood-decay fungi showed a trend towards higher diversity in the 1- and 11-y stands, and species composition in these sites corresponded. Patterns of diversity and distribution were mainly determined by factors related to substratum availability and vegetation structure. Knowledge about the influence of artificially reforested stands on macrofungal communities is relevant to improve management plans and achieve a more sustainable use of forest timber and non-timber products.     

Ectomycorrhizal fungal diversity and saprotrophic fungal diversity are linked to different tree community attributes in a field‐based tree experiment

Exploring the link between above‐ and belowground biodiversity has been a major theme of recent ecological research, due in large part to the increasingly well‐recognized role that soil microorganisms play in driving plant community processes. In this study, we utilized a field‐based tree experiment in Minnesota, USA, to assess the effect of changes in plant species richness and phylogenetic diversity on the richness and composition of both ectomycorrhizal and saprotrophic fungal communities. We found that ectomycorrhizal fungal species richness was significantly positively influenced by increasing plant phylogenetic diversity, while saprotrophic fungal species richness was significantly affected by plant leaf nitrogen content, specific root length and standing biomass. The increasing ectomycorrhizal fungal richness associated with increasing plant phylogenetic diversity was driven by the combined presence of ectomycorrhizal fungal specialists in plots with both gymnosperm and angiosperm hosts. Although the species composition of both the ectomycorrhizal and saprotrophic fungal communities changed significantly in response to changes in plant species composition, the effect was much greater for ectomycorrhizal fungi. In addition, ectomycorrhizal but not saprotrophic fungal species composition was significantly influenced by both plant phylum (angiosperm, gymnosperm, both) and origin (Europe, America, both). The phylum effect was caused by differences in ectomycorrhizal fungal community composition, while the origin effect was attributable to differences in community heterogeneity. Taken together, this study emphasizes that plant‐associated effects on soil fungal communities are largely guild‐specific and provides a mechanistic basis for the positive link between plant phylogenetic diversity and ectomycorrhizal fungal richness.     

Density-range size relationships in French riverine fishes

We examined the relation between the local density of species and the size of the geographic range for French riverine fishes. As for most other taxonomic groups, a positive interspecific relationship is found for this group. This relationship is robust to the confounding effects of phylogeny and is not a priori a product of other potential mechanistic artefacts. We formally tested two of the principal biological mechanisms already proposed (i.e. the niche breadth hypothesis and the resource availability hypothesis). We found no support for the niche breadth hypothesis. In contrast, we found consistent support for the closely related resource availability hypothesis. Species utilising resources (habitats) that are marginal tend to appear at low density and to have narrow distribution whereas species utilising widespread habitats tend to be more abundant and more widely distributed. Using data on body size and reproductive traits we explored the potential influence of these variables in explaining significant variation around the density-range size relationship. Only body size explains significant variation around the relationship, being negatively correlated with local density and positively correlated with range size.     

氮沉降对外生菌根真菌的影响

综述了国外氮沉降对外生菌根真菌的影响研究现状 ,主要从菌根形成、形态 (菌丝体、菌根 )变化、子实体生产力和外生菌根真菌群落结构等方面对氮沉降的响应进行了综述 ,并初步探讨了氮饱和的临界负荷。研究表明 ,过量氮沉降会给外生菌根真菌在以下几个方面带来负影响 :(1)影响外生菌根真菌与寄主植物之间的养分分配和循环 ;(2 )降低子实体生产力 ;(3)减少菌丝 ;(4 )降低菌根量及其活力 ;(5 )降低外生菌根真菌丰富度 ;(6 )改变外生菌根真菌群落结构组成 ;(7)降低外生菌根真菌群落功能。还指出了未来该方面研究重点和方向