Exotic mammals disperse exotic fungi that promote invasion by exotic trees

Suillus: an emerging model for the study of ectomycorrhizal ecology and evolution

Research on mycorrhizal symbiosis has been slowed by a lack of established study systems. To address this challenge, we have been developing Suillus, a widespread ecologically and economically relevant fungal genus primarily associated with the plant family Pinaceae, into a model system for studying ectomycorrhizal (ECM) associations. Over the last decade, we have compiled extensive genomic resources, culture libraries, a phenotype database, and protocols for manipulating Suillus fungi with and without their tree partners. Our efforts have already resulted in a large number of publicly available genomes, transcriptomes, and respective annotations, as well as advances in our understanding of mycorrhizal partner specificity and host communication, fungal and plant nutrition, environmental adaptation, soil nutrient cycling, interspecific competition, and biological invasions. Here, we highlight the most significant recent findings enabled by Suillus, present a suite of protocols for working with the genus, and discuss how Suillus is emerging as an important model to elucidate the ecology and evolution of ECM interactions.

Effects of root-colonizing fungi on pioneer Pinus thunbergii seedlings in primary successional volcanic mudflow on Kuchinoerabu Island, Japan

Root-colonizing fungi, such as mycorrhizal fungi and dark septate endophyte fungi, are often found on pioneer plant species during early primary succession. However, little is known about which fungal species are responsible for the establishment of pioneer plants when these symbionts colonize simultaneously. We investigated the root-colonizing fungal communities of Pinus thunbergii that established prior to lichens, bryophytes, and short-lived herbaceous plants in a primary successional volcanic mudflow site on Kuchinoerabu Island, Japan. We collected a total of 54 current-year and 1- to 2-year-old seedlings. The colonization of root fungi was evaluated by direct observation of key structures (e.g., mantle, arbuscule, microsclerotia, and hyphae) and molecular analysis. Of the 34 current-year seedlings collected, only 12 individuals were colonized by ectomycorrhizal (ECM) fungi. By contrast, all 1- to 2-year-old seedlings were colonized by ECM fungi. Seedlings colonized by pine-specific ECM fungi, specifically Rhizopogon roseolus and Suillus granulatus, showed higher nitrogen and phosphorus contents in their needles compared to non-ECM seedlings. Arbuscular mycorrhizal fungi and dark septate endophyte fungi were found in only two and three individuals, respectively. The high density of mycophagous deer on Kuchinoerabu-jima may contribute to the favored dispersal of ECM fungi over other root-colonizing fungi. In conclusion, the seedling establishment of P. thunbergii at the volcanic mudflow may be largely supported by ECM fungi, with negligible effects of arbuscular mycorrhizal fungi and dark septate endophytes.

Native diversity buffers against severity of non-native tree invasions

Determining the drivers of non-native plant invasions is critical for managing native ecosystems and limiting the spread of invasive species1,2. Tree invasions in particular have been relatively overlooked, even though they have the potential to transform ecosystems and economies3,4. Here, leveraging global tree databases5-7, we explore how the phylogenetic and functional diversity of native tree communities, human pressure and the environment influence the establishment of non-native tree species and the subsequent invasion severity. We find that anthropogenic factors are key to predicting whether a location is invaded, but that invasion severity is underpinned by native diversity, with higher diversity predicting lower invasion severity. Temperature and precipitation emerge as strong predictors of invasion strategy, with non-native species invading successfully when they are similar to the native community in cold or dry extremes. Yet, despite the influence of these ecological forces in determining invasion strategy, we find evidence that these patterns can be obscured by human activity, with lower ecological signal in areas with higher proximity to shipping ports. Our global perspective of non-native tree invasion highlights that human drivers influence non-native tree presence, and that native phylogenetic and functional diversity have a critical role in the establishment and spread of subsequent invasions.

Wild Boar Effects on Fungal Abundance and Guilds from Sporocarp Sampling in a Boreal Forest Ecosystem

Simple Summary

Native wild boar populations are expanding across Europe, causing concern due to their significant soil disturbances and considerable impact on ecosystems. However, little is known about how wild boar activities affect other organisms. This study investigated the effects of wild boars on the abundance of fungal sporocarps and their respective fungal guilds (i.e., symbiotic, saprophytic and pathogenic) in boreal forests in Sweden. We selected 11 forested sites in central Sweden: six with and five without the presence of wild boar. We determined the presence or absence of wild boar and rooting intensity at each site. Simultaneously, we investigated the abundance of fungal sporocarps and their fungal guilds. We found that the presence of wild boar and rooting intensity were associated with the abundance of fungal sporocarps. Wild boar rooting was positively correlated with saprotrophic fungi and negatively with symbiotic fungi. Pathogenic fungi were more abundant in plots with no rooting but in the presence of wild boar. We conclude that wild boar represents a recurrent disturbance agent and, based on sporocarp abundance, could eventually affect entire fungal populations.

Abstract

Native wild boar (Sus scrofa) populations are expanding across Europe. This is cause for concern in some areas where overabundant populations impact natural ecosystems and adjacent agronomic systems. To better manage the potential for impacts, managers require more information about how the species may affect other organisms. For example, information regarding the effect of wild boar on soil fungi for management application is lacking. Soil fungi play a fundamental role in ecosystems, driving essential ecological functions; acting as mycorrhizal symbionts, sustaining plant nutrition and providing defense; as saprotrophs, regulating the organic matter decomposition; or as plant pathogens, regulating plant fitness and survival. During autumn (Sep–Nov) 2018, we investigated the effects of wild boar (presence/absence and rooting intensity) on the abundance (number of individuals) of fungal sporocarps and their functional guilds (symbiotic, saprotrophic and pathogenic). We selected eleven forested sites (400–500 × 150–200 m) in central Sweden; six with and five without the presence of wild boar. Within each forest, we selected one transect (200 m long), and five plots (2 × 2 m each) for sites without wild boar, and ten plots for sites with boars (five within and five outside wild boar disturbances), to determine the relationship between the intensity of rooting and the abundance of sporocarps for three fungal guilds. We found that the presence of wild boar and rooting intensity were associated with the abundance of sporocarps. Interestingly, this relationship varied depending on the fungal guild analyzed, where wild boar rooting had a positive correlation with saprophytic sporocarps and a negative correlation with symbiotic sporocarps. Pathogenic fungi, in turn, were more abundant in undisturbed plots (no rooting) but located in areas with the presence of wild boar. Our results indicate that wild boar activities can potentially regulate the abundance of fungal sporocarps, with different impacts on fungal guilds. Therefore, wild boar can affect many essential ecosystem functions driven by soil fungi in boreal forests, such as positive effects on energy rotation and in creating mineral availability to plants, which could lead to increased diversity of plants in boreal forests.

The right tree in the right place? A major economic tree species poses major ecological threats

Tree species in the Pinaceae are some of the most widely introduced non-native tree species globally, especially in the southern hemisphere. In New Zealand, plantations of radiata pine (Pinus radiata D. Don) occupy c. 1.6 million ha and form 90% of planted forests. Although radiata pine has naturalized since 1904, there is a general view in New Zealand that this species has not invaded widely. We comprehensively review where radiata pine has invaded throughout New Zealand. We used a combination of observational data and climate niche modelling to reveal that invasion has occurred nationally. Climate niche modelling demonstrates that while current occurrences are patchy, up to 76% of the land area (i.e. 211,388 km2) is climatically capable of supporting populations. Radiata pine has mainly invaded grasslands and shrublands, but also some forests. Notably, it has invaded lower-statured vegetation, including three classes of naturally uncommon ecosystems, primary successions and secondary successions. Overall, our findings demonstrate pervasive and ongoing invasion of radiata pine outside plantations. The relatively high growth rates and per individual effects of radiata pine may result in strong effects on naturally uncommon ecosystems and may alter successional trajectories. Local and central government currently manage radiata pine invasions while propagule pressure from existing and new plantations grows, hence greater emphasis is warranted both on managing current invasions and proactively preventing future radiata pine invasions. We therefore recommend a levy on new non-native conifer plantations to offset costs of managing invasions, and stricter regulations to protect vulnerable ecosystems. A levy on economic uses of invasive species to offset costs of managing invasions alongside stricter regulations to protect vulnerable ecosystems could be a widely adopted measure to avert future negative impacts.

Soil spore bank communities of ectomycorrhizal fungi in Pseudotsuga japonica forests and neighboring plantations

Ectomycorrhizal (EcM) fungal spores play an important role in seedling establishment and forest regeneration, especially in areas where compatible host tree species are absent. However, compared to other Pinaceae trees with a wide distribution, limited information is available for the interaction between the endangered Pseudotsuga trees and EcM fungi, especially the spore bank. The aim of this study was to investigate EcM fungal spore bank communities in soil in remnant patches of Japanese Douglas-fir (Pseudotsuga japonica) forest. We conducted a bioassay of 178 soil samples collected from three P. japonica forests and their neighboring arbuscular mycorrhizal artificial plantations, using the more readily available North American Douglas-fir (Pseudotsuga menziesii) as bait seedlings. EcM fungal species were identified by a combination of morphotyping and DNA sequencing of the ITS region. We found that EcM fungal spore banks were present not only in P. japonica forests but also in neighboring plantations. Among the 13 EcM fungal species detected, Rhizopogon togasawarius had the second highest frequency and was found in all plots, regardless of forest type. Species richness estimators differed significantly among forest types. The community structure of EcM fungal spore banks differed significantly between study sites but not between forest types. These results indicate that EcM fungal spore banks are not restricted to EcM forests and extend to surrounding forest dominated by arbuscular mycorrhizal trees, likely owing to the durability of EcM fungal spores in soils.

Discovering the role of Patagonian birds in the dispersal of truffles and other mycorrhizal fungi

Dispersal is a key process that impacts population dynamics and structures biotic communities. Dispersal limitation influences the assembly of plant and microbial communities, including mycorrhizal fungi and their plant hosts. Mycorrhizal fungi play key ecological roles in forests by feeding nutrients to plants in exchange for sugars, so the dispersal of mycorrhizal fungi spores actively shapes plant communities. Although many fungi rely on wind for spore dispersal, some fungi have lost the ability to shoot their spores into the air and instead produce enclosed belowground fruiting bodies (truffles) that rely on animals for dispersal. The role of mammals in fungal spore dispersal is well documented, but the relevance of birds as dispersal agents of fungi has been understudied, despite the prominence of birds as seed dispersal vectors. Here, we use metagenomics and epifluorescence microscopy to demonstrate that two common, widespread, and endemic Patagonian birds, chucao tapaculos (Scelorchilus rubecula) and black-throated huet-huets (Pteroptochos tarnii), regularly consume mycorrhizal fungi and disperse viable spores via mycophagy. Our metagenomic analysis indicates that these birds routinely consume diverse mycorrhizal fungi, including many truffles, that are symbiotically associated with Nothofagaceae trees that dominate Patagonian forests. Epifluorescence microscopy of fecal samples confirmed that the birds dispersed copious viable spores from truffles and other mycorrhizal fungi. We show that fungi are a common food for both bird species and that this animal-fungi symbiosis is widespread and ecologically important in Patagonia. Our findings indicate that birds may also act as cryptic but critical fungal dispersal agents in other ecosystems.

Invasive wild boar’s distribution overlap with threatened native ungulate in Patagonia

Wild boar (Sus scrofa) is one of the most damaging invasive species in the world and can have a profound impact on the distribution of native species. Nevertheless, there still are limitations on the species’ current fine-scale spatial information, which is needed to develop effective management measures. Here, we used Species Distribution Models (SDMs) and niche overlap analysis to estimate potential conflict areas between the wild boar and the native southern pudu (Pudu puda), which is a bioindicator of the forest conservation status within the Nahuel Huapi National Park (NHNP), Argentina. The two species’ environmental niche overlaps by 40%, which results in a wide geographical overlap between wild boar and pudu distributions. The distribution model predicted that the wild boar potential distribution occupies 22% of the national park and overlaps up to 67% with the pudu distribution, which in turn occupies 20% of the park. Based on our models, we classified 12% of the park as extreme management priority areas, because both species are present. High priority areas, where wild boars have the potential to invade but will not overlap with pudu populations, represent 10% of the park. Medium priority areas, where wild boars do not threaten pudu populations, and low priority areas, with no potential presence of either species, are 8% and 68%, respectively. The results of this study show how SDMs developed at local scales can support the management and monitoring of native and invasive species and help guide the allocation of efforts and resources for management actions focused on protected areas.

Thaxterogaster revisited: A phylogenetic and taxonomic overview of sequestrate Cortinarius from Patagonia

In the Patagonian region, Cortinarius is the most diverse and abundant genus of ectomycorrhizal fungi with at least 250 species. Sequestrate forms were until recently documented within the genus Thaxterogaster, a genus now known to be polyphyletic, and many were consequently transferred to Cortinarius. Original descriptions were mostly available in German and Spanish and interpretations of morphological structures outdated. Despite recent advances in Cortinarius systematics, the current classification, diversity, and ecology of sequestrate "cortinarioid" fungi in Patagonia remain unclear. The objective of this study was to provide an update on sequestrate Cortinarius of southern South America. We documented each species with morphological descriptions, photographs, basidiospore scanning electron microscopy (SEM) images, and molecular characterization using nuc rDNA internal transcribed spacer region ITS1-5.8S-ITS2 (ITS) and nuc 28S rDNA (28S) sequence data. Original descriptions of taxa were also translated to English and revised based on fresh collections. We documented 24 species from Patagonia based on molecular data and conducted morphological and phylogenetic analysis for 18 previously described species based on type and reference specimens. In addition, we formally described two new species. Four additional taxa were provisionally determined as new but require further study. New ITS sequence data were produced from eight type specimens. We also provide a new name, Cortinarius gloiodes, nom. nov., for the taxon previously described as Thaxterogaster gliocyclus. In addition to the species treated in detail, we provided additional reference information and discussion on six described species that remained incompletely known or for which no recent collections were found. Of the 24 taxa documented from Patagonia, 15 species were assigned to 12 current sections in the genus Cortinarius. Analysis of spore ultrastructure showed that sequestrate forms of Patagonian Cortinarius lack a true perisporium.

Alien ectomycorrhizal plants differ in their ability to interact with co-introduced and native ectomycorrhizal fungi in novel sites

Alien plants represent a potential threat to environment and society. Understanding the process of alien plants naturalization is therefore of primary importance. In alien plants, successful establishment can be constrained by the absence of suitable fungal partners. Here, we used 42 independent datasets of ectomycorrhizal fungal (EcMF) communities associated with alien Pinaceae and Eucalyptus spp., as the most commonly introduced tree species worldwide, to explore the strategies these plant groups utilize to establish symbioses with EcMF in the areas of introduction. We have also determined the differences in composition of EcMF communities associated with alien ectomycorrhizal plants in different regions. While alien Pinaceae introduced to new regions rely upon association with co-introduced EcMF, alien Eucalyptus often form novel interactions with EcMF species native to the region where the plant was introduced. The region of origin primarily determines species composition of EcMF communities associated with alien Pinaceae in new areas, which may largely affect invasion potential of the alien plants. Our study shows that alien ectomycorrhizal plants largely differ in their ability to interact with co-introduced and native ectomycorrhizal fungi in sites of introduction, which may potentially affect their invasive potential.

Sheep feeding preference as a tool to control pine invasion in Patagonia: influence of foliar toughness, terpenoids and resin content

Herbivores modulate the structure and composition of plant communities, including plant invasions. This is conditioned by plant palatability which can be reduced by its chemical or physical traits. The effects that ungulates browsing has on pine invasions are variable and the empirical evidence on the causes of this variability is scarce. We experimentally explored how sheep browsing preference varies between seedlings of pine species with different invasiveness; Pinus contorta (high invasiveness), P. ponderosa (medium invasiveness), P. radiata (medium invasiveness) and P. jeffreyi (low invasiveness). Secondly, we quantified anti-herbivory chemical compounds and physical traits of these species and related them with sheep preference observed. The browsing incidence of P. contorta was 68%, P. ponderosa 58%, P. radiata 29%, and P. jeffreyi 84%. Among anti-herbivory traits analyzed, α-pinene concentration had a negative effect on the probability of a terminal bud being browsed and on browsing intensity. Meanwhile, foliar toughness was negatively related to browsing intensity and water concentration was positively related to browsing intensity. Also, the most invasive species, P. contorta, was highly damaged. Thus, sheep herbivory could be slowing pine invasion rate; suggesting that could be considered a tool to control early invasions, especially for this particular species.

The endangered Hastings River mouse (Pseudomys oralis) as a disperser of ectomycorrhizal fungi in eastern Australia

Rodents are the most widespread and diverse order of vertebrate mycophagists and are key to the dispersal of mycorrhizal fungi. Rodents consume and subsequently disperse fungi through their feces on every continent except Antarctica. This study examines the fungal taxa consumed by the Hastings River mouse (Pseudomys oralis), an endangered Australian endemic rodent from the family Muridae. We analyzed 251 fecal samples collected over a 19-year period between 1993 and 2012 at sites throughout the distribution of the animal in New South Wales and Queensland. We show that at least 16 genera of mycorrhizal fungi are eaten by this species and that it is therefore playing an important role as a vector of ectomycorrhizal truffle-like fungi in eastern Australia. Similar to the fungal diets of other mammals in eastern Australia, seasonal fungal consumption was greatest in autumn and winter. The dietary diversity of P. oralis also appeared to follow a geographic trend from south to north; samples collected at sites in the southern part of the species' range had greater diversity than those from sites in the northern part of the range, and overall, diets from southern sites yielded more fungal taxa than did northern sites. This study provides novel insights into the diet of P. oralis and highlights the importance of previously overlooked ecosystem services this species provides through its dispersal of mycorrhizal fungi.

Highly invasive tree species are more dependent on mutualisms

Why some species become invasive while others do not remains an elusive question. It has been proposed that invasive species should depend less on mutualisms, because their spread would then be less constrained by the availability of mutualistic partners. We tested this idea with the genus Pinus, whose degree of invasiveness is known at the species level (being highly and negatively correlated with seed size), and which forms obligate mutualistic associations with ectomycorrhizal fungi (EMF). Mycorrhizal dependence is defined as the degree to which a plant needs the mycorrhizal fungi to show the maximum growth. In this regard, we use plant growth response to mycorrhizal fungi as a proxy for mycorrhizal dependence. We assessed the responsiveness of Pinus species to EMF using 1,206 contrasts published on 34 species, and matched these data with data on Pinus species invasiveness. Surprisingly, we found that species that are more invasive depend more on mutualisms (EMF). Seedling growth of species with smaller seeds benefited more from mutualisms, indicating a higher dependence. A higher reliance on EMF could be part of a strategy in which small-seeded species produce more seeds that can disperse further, and these species are likely to establish only if facilitated by mycorrhizal fungi. On the contrary, big-seeded species showed a lower dependence on EMF, which may be explained by their tolerance to stressful conditions during establishment. However, the limited dispersal of larger seeds may limit the spread of these species. We present strong evidence against a venerable belief in ecology that species that rely more on mutualisms are less prone to invade, and suggest that in certain circumstances greater reliance on mutualists can increase spread capacity.

Notes, outline and divergence times of Basidiomycota

The Basidiomycota constitutes a major phylum of the kingdom Fungi and is second in species numbers to the Ascomycota. The present work provides an overview of all validly published, currently used basidiomycete genera to date in a single document. An outline of all genera of Basidiomycota is provided, which includes 1928 currently used genera names, with 1263 synonyms, which are distributed in 241 families, 68 orders, 18 classes and four subphyla. We provide brief notes for each accepted genus including information on classification, number of accepted species, type species, life mode, habitat, distribution, and sequence information. Furthermore, three phylogenetic analyses with combined LSU, SSU, 5.8s, rpb1, rpb2, and ef1 datasets for the subphyla Agaricomycotina, Pucciniomycotina and Ustilaginomycotina are conducted, respectively. Divergence time estimates are provided to the family level with 632 species from 62 orders, 168 families and 605 genera. Our study indicates that the divergence times of the subphyla in Basidiomycota are 406–430 Mya, classes are 211–383 Mya, and orders are 99–323 Mya, which are largely consistent with previous studies. In this study, all phylogenetically supported families were dated, with the families of Agaricomycotina diverging from 27–178 Mya, Pucciniomycotina from 85–222 Mya, and Ustilaginomycotina from 79–177 Mya. Divergence times as additional criterion in ranking provide additional evidence to resolve taxonomic problems in the Basidiomycota taxonomic system, and also provide a better understanding of their phylogeny and evolution.

Taxi drivers: the role of animals in transporting mycorrhizal fungi

Dispersal of mycorrhizal fungi via animals and the importance for the interacting partners' life history as well as for ecosystems is an understudied topic. In this review, we describe the available evidence and the most important knowledge gaps and finally suggest ways to gain the missing information. So far, 33 articles have been published proving a successful transfer of mycorrhizal propagules by animals. The vast majority of research on invertebrates was focused on arbuscular mycorrhizal (AM) fungi, whereas papers on vertebrates (mainly rodents and artiodactyls) equally addressed ectomycorrhizal (ECM) and AM fungi. Effective dispersal has been mostly shown by the successful inoculation of bait plants and less commonly by spore staining or germination tests. Based on the available data and general knowledge on animal lifestyles, collembolans and oribatid mites may be important in transporting ECM fungal propagules by ectozoochory, whereas earthworms, isopods, and millipedes could mainly transfer AM fungal spores in their gut systems. ECM fungal distribution may be affected by mycophagous dipterans and their hymenopteran parasitoids, while slugs, snails, and beetles could transport both mycorrhizal groups. Vertebrates feeding on fruit bodies were shown to disperse mainly ECM fungi, while AM fungi are transported mostly accidentally by herbivores. The important knowledge gaps include insufficient information on dispersal of fungal propagules other than spores, the role of invertebrates in the dispersal of mycorrhizal fungi, the way in which propagules pass through food webs, and the spatial distances reached by different dispersal mechanisms both horizontally and vertically.

Suilloid fungi as global drivers of pine invasions

Belowground biota can deeply influence plant invasion. The presence of appropriate soil mutualists can act as a driver to enable plants to colonize new ranges. We reviewed the species of ectomycorrhizal fungi (EMF) that facilitate pine establishment in both native and non-native ranges, and that are associated with their invasion into nonforest settings. We found that one particular group of EMF, suilloid fungi, uniquely drive pine invasion in the absence of other EMF. Although the association with other EMF is variable, suilloid EMF are always associated with invasive pines, particularly at early invasion, when invasive trees are most vulnerable. We identified five main ecological traits of suilloid fungi that may explain their key role at pine invasions: their long-distance dispersal capacity, the establishment of positive biotic interactions with mammals, their capacity to generate a resistant spore bank, their rapid colonization of roots and their long-distance exploration type. These results suggest that the identity of mycorrhizal fungi and their ecological interactions, rather than simply the presence of compatible fungi, are key to the understanding of plant invasion processes and their success or failure. Particularly for pines, their specific association with suilloid fungi determines their invasion success in previously uninvaded ecosystems.

Insights on the persistence of pines (Pinus species) in the Late Cretaceous and their increasing dominance in the Anthropocene

Although gymnosperms were nearly swept away by the rise of the angiosperms in the Late Cretaceous, conifers, and pines (Pinus species) in particular, survived and regained their dominance in some habitats. Diversification of pines into fire-avoiding (subgenus Haploxylon) and fire-adapted (subgenus Diploxylon) species occurred in response to abiotic and biotic factors in the Late Cretaceous such as competition with emerging angiosperms and changing fire regimes. Adaptations/traits that evolved in response to angiosperm-fuelled fire regimes and stressful environments in the Late Cretaceous were key to pine success and are also contributing to a new "pine rise" in some areas in the Anthropocene. Human-mediated activities exert both positive and negative impacts of range size and expansion and invasions of pines. Large-scale afforestation with pines, human-mediated changes to fire regimes, and other ecosystem processes are other contributing factors. We discuss traits that evolved in response to angiosperm-mediated fires and stressful environments in the Cretaceous and that continue to contribute to pine persistence and dominance and the numerous ways in which human activities favor pines.

Crested porcupines (Hystrix cristata): mycophagist spore dispersers of the ectomycorrhizal truffle Tuber aestivum

Truffles, as hypogeous, ectomycorrhizal fungi, have no means to actively discharge spores into the environment and thus depend on mycophagists for spore dispersal. After consumption of fruiting bodies by animals and passage through the digestive tract, the spores are released in faecal pellets. Recently, in the Abruzzo region (Italy), Hystrix cristata has been spotted inside private truffières, but its role in spore dispersal has never been investigated. Here, we report our research on the occurrence of Tuber aestivum spores in porcupine's faecal contents in a truffière in L'Aquila, Italy, where a H. cristata specimen was photographed. The spores were isolated from faeces by using a suspension of 0.7 M ZnSO₄. We also verified degradation and disfiguration of the digested spores' reticular ornamentation compared to that of fresh spores from ascomata collected inside the truffière, through measurements performed by scanning electron microscopy. A few truffle spores had germinated within the faeces.

Give me a sample of air and I will tell which species are found from your region: Molecular identification of fungi from airborne spore samples

Fungi are a megadiverse group of organisms, they play major roles in ecosystem functioning and are important for human health, food production and nature conservation. Our knowledge on fungal diversity and fungal ecology is however still very limited, in part because surveying and identifying fungi is time demanding and requires expert knowledge. We present a method that allows anyone to generate a list of fungal species likely to occur in a region of interest, with minimal effort and without requiring taxonomical expertise. The method consists of using a cyclone sampler to acquire fungal spores directly from the air to an Eppendorf tube, and applying DNA barcoding with probabilistic species identification to generate a list of species from the sample. We tested the feasibility of the method by acquiring replicate air samples from different geographical regions within Finland. Our results show that air sampling is adequate for regional-level surveys, with samples collected >100 km apart varying but samples collected <10 km apart not varying in their species composition. The data show marked phenology, and thus obtaining a representative species list requires aerial sampling that covers the entire fruiting season. In sum, aerial sampling combined with probabilistic molecular species identification offers a highly effective method for generating a species list of air-dispersing fungi. The method presented here has the potential to revolutionize fungal surveys, as it provides a highly cost-efficient way to include fungi as a part of large-scale biodiversity assessments and monitoring programs.

Introduction to the Special Issue: Ungulates and invasive species: quantifying impacts and understanding interactions

White-tailed deer are emblematic ungulates that, due to anthropogenic modification of landscapes, currently occur at elevated densities. Elevated deer densities often co-occur with non-native plants, but it is not known if plant invasions are a consequence of deer impacts or occur independent of deer impacts on ecosystems, or whether these two stressors are synergistic. A colloquium on 'Interactions of white-tailed deer and invasive plants in forests of eastern North America' explored these topics at the 2016 annual meeting of the Botanical Society of America. Nine of those presentations are published in this special issue of AoB PLANTS.

Wild boars as spore dispersal agents of ectomycorrhizal fungi: consequences for community composition at different habitat types

The success of dispersal events depend on the organism's ability to reach and establish in a new habitat. In symbiotic organisms, establishment also depends on the presence of their symbiont partner in the new habitat. For instance, the establishment of obligate ectomycorrhizal (EM) trees outside the forest is largely limited by the presence of EM fungi in soil. Wild boars (Sus scrofa) are important dispersal agents of EM fungal spores, particularly in the moderately dry Mediterranean region. The aim of this study was to explore how EM fungal spores dispersed by wild boars influence the EM fungal community associated with the roots of Pinus halepensis seedlings at different habitat types. Using a greenhouse bioassay, we grew pine seedlings in two soil types: old-field and forest soils mixed with either natural or autoclaved wild boar feces. In both soils, we observed a community dominated by a few EM fungal species. Geopora (85 %) and Suillus (68 %) species dominated the forest and old-field soils, respectively. The addition of natural wild boar feces increased the abundance of Tuber species in both EM fungal communities. However, this effect was more pronounced in pots with old-field soil, leading to a more even community, equally dominated by both Tuber and Suillus species. In forest soil, Geopora maintained dominance, but decreased in abundance (67 %), due to the addition of Tuber species. Our findings indicate that wild boar feces can be an important source for EM inoculum, especially in habitats poor in EM fungi such as old-fields.

Loss of functional diversity and network modularity in introduced plant-fungal symbioses

The introduction of alien plants into a new range can result in the loss of co-evolved symbiotic organisms, such as mycorrhizal fungi, that are essential for normal plant physiological functions. Prior studies of mycorrhizal associations in alien plants have tended to focus on individual plant species on a case-by-case basis. This approach limits broad scale understanding of functional shifts and changes in interaction network structure that may occur following introduction. Here we use two extensive datasets of plant-fungal interactions derived from fungal sporocarp observations and recorded plant hosts in two island archipelago nations: New Zealand (NZ) and the United Kingdom (UK). We found that the NZ dataset shows a lower functional diversity of fungal hyphal foraging strategies in mycorrhiza of alien as compared with native trees. Across species this resulted in fungal foraging strategies associated with alien trees being much more variable in functional composition compared with native trees, which had a strikingly similar functional composition. The UK data showed no functional difference in fungal associates of alien and native plant genera. Notwithstanding this, both the NZ and UK data showed a substantial difference in interaction network structure of alien trees compared with native trees. In both cases, fungal associates of native trees showed strong modularity, while fungal associates of alien trees generally integrated into a single large module. The results suggest a lower functional diversity (in one dataset) and a simplification of network structure (in both) as a result of introduction, potentially driven by either limited symbiont co-introductions or disruption of habitat as a driver of specificity due to nursery conditions, planting, or plant edaphic-niche expansion. Recognizing these shifts in function and network structure has important implications for plant invasions and facilitation of secondary invasions via shared mutualist populations.

Twelve years of repeated wild hog activity promotes population maintenance of an invasive clonal plant in a coastal dune ecosystem

Invasive animals can facilitate the success of invasive plant populations through disturbance. We examined the relationship between the repeated foraging disturbance of an invasive animal and the population maintenance of an invasive plant in a coastal dune ecosystem. We hypothesized that feral wild hog (Sus scrofa) populations repeatedly utilized tubers of the clonal perennial, yellow nutsedge (Cyperus esculentus) as a food source and evaluated whether hog activity promoted the long‐term maintenance of yellow nutsedge populations on St. Catherine's Island, Georgia, United States. Using generalized linear mixed models, we tested the effect of wild hog disturbance on permanent sites for yellow nutsedge culm density, tuber density, and percent cover of native plant species over a 12‐year period. We found that disturbance plots had a higher number of culms and tubers and a lower percentage of native live plant cover than undisturbed control plots. Wild hogs redisturbed the disturbed plots approximately every 5 years. Our research provides demographic evidence that repeated foraging disturbances by an invasive animal promote the long‐term population maintenance of an invasive clonal plant. Opportunistic facultative interactions such as we demonstrate in this study are likely to become more commonplace as greater numbers of introduced species are integrated into ecological communities around the world.

Replacement of native by non-native animal communities assisted by human introduction and management on Isla Victoria, Nahuel Huapi National Park

One of the possible consequences of biological invasions is the decrease of native species abundances or their replacement by non-native species. In Andean Patagonia, southern Argentina and Chile, many non-native animals have been introduced and are currently spreading. On Isla Victoria, Nahuel Huapi National Park, many non-native vertebrates were introduced ca. 1937. Records indicate that several native vertebrates were present before these species were introduced. We hypothesize that seven decades after the introduction of non-native species and without appropriate management to maintain native diversity, non-native vertebrates have displaced native species (given the known invasiveness and impacts of some of the introduced species). We conducted direct censuses in linear transects 500 m long (n = 10) in parallel with camera-trapping (1,253 camera-days) surveys in two regions of the island with different levels of disturbance: high (n = 4) and low (n = 6) to study the community of terrestrial mammals and birds and the relative abundances of native and non-native species. Results show that currently non-native species are dominant across all environments; 60.4% of census records and 99.7% of camera trapping records are of non-native animals. We detected no native large mammals; the assemblage of large vertebrates consisted of five non-native mammals and one non-native bird. Native species detected were one small mammal and one small bird. Species with the highest trapping rate were red and fallow deer, wild boar, silver pheasant (all four species are non-native) and chucao (a native bird). These results suggest that native species are being displaced by non-natives and are currently in very low numbers.