Interactions between fire, mycophagous mammals, and dispersal of ectromycorrhizal fungi in Eucalyptus forests

Mammalian Mycophagy: a Global Review of Ecosystem Interactions Between Mammals and Fungi

The consumption of fungi by animals is a significant trophic interaction in most terrestrial ecosystems, yet the role mammals play in these associations has been incompletely studied. In this review, we compile 1 154 references published over the last 146 years and provide the first comprehensive global review of mammal species known to eat fungi (508 species in 15 orders). We review experimental studies that found viable fungal inoculum in the scats of at least 40 mammal species, including spores from at least 58 mycorrhizal fungal species that remained viable after ingestion by mammals. We provide a summary of mammal behaviours relating to the consumption of fungi, the nutritional importance of fungi for mammals, and the role of mammals in fungal spore dispersal. We also provide evidence to suggest that the morphological evolution of sequestrate fungal sporocarps (fruiting bodies) has likely been driven in part by the dispersal advantages provided by mammals. Finally, we demonstrate how these interconnected associations are widespread globally and have far-reaching ecological implications for mammals, fungi and associated plants in most terrestrial ecosystems.

Fire as a driver of fungal diversity - A synthesis of current knowledge

Fires occur in most terrestrial ecosystems where they drive changes in the traits, composition, and diversity of fungal communities. Fires range from rare, stand-replacing wildfires to frequent, prescribed fires used to mimic natural fire regimes. Fire regime factors, including burn severity, fire intensity, and timing, vary widely and likely determine how fungi respond to fires. Despite the importance of fungi to post-fire plant communities and ecosystem functioning, attempts to identify common fungal responses and their major drivers are lacking. This synthesis addresses this knowledge gap and ranges from fire adaptations of specific fungi to succession and assembly fungal communities as they respond to spatially heterogenous burning within the landscape. Fires impact fungi directly and indirectly through their effects on fungal survival, substrate and habitat modifications, changes in environmental conditions, and/or physiological responses of the hosts with which fungi interact. Some specific pyrophilous, or "fire-loving," fungi often appear after fire. Our synthesis explores whether such taxa can be considered cosmopolitan, and whether they are truly fire-adapted or simply opportunists adapted to rapidly occupy substrates and habitats made available by fires. We also discuss the possible inoculum sources of post-fire fungi and explore existing conceptual models and ecological frameworks that may be useful in generalizing fungal fire responses. We conclude with identifying research gaps and areas that may best transform the current knowledge and understanding of fungal responses to fire.

High resilience of the mycorrhizal community to prescribed seasonal burnings in eastern Mediterranean woodlands

Fire effects on ecosystems range from destruction of aboveground vegetation to direct and indirect effects on belowground microorganisms. Although variation in such effects is expected to be related to fire severity, another potentially important and poorly understood factor is the effect of fire seasonality on soil microorganisms. We carried out a large-scale field experiment examining the effects of spring (early-dry season) versus autumn (late-dry- season) burns on the community composition of soil fungi in a typical Mediterranean woodland. Although the intensity and severity of our prescribed burns were largely consistent between the two burning seasons, we detected differential fire season effects on the composition of the soil fungal community, driven by changes in the saprotrophic fungal guild. The community composition of ectomycorrhizal fungi, assayed both in pine seedling bioassays and from soil sequencing, appeared to be resilient to the variation inflicted by seasonal fires. Since changes in the soil saprotrophic fungal community can directly influence carbon emission and decomposition rates, we suggest that regardless of their intensity and severity, seasonal fires may cause changes in ecosystem functioning.

Modeling mycorrhizal fungi dispersal by the mycophagous swamp wallaby (Wallabia bicolor)

Despite the importance of mammal-fungal interactions, tools to estimate the mammal-assisted dispersal distances of fungi are lacking. Many mammals actively consume fungal fruiting bodies, the spores of which remain viable after passage through their digestive tract. Many of these fungi form symbiotic relationships with trees and provide an array of other key ecosystem functions. We present a flexible, general model to predict the distance a mycophagous mammal would disperse fungal spores. We modeled the probability of spore dispersal by combining animal movement data from GPS telemetry with data on spore gut-retention time. We test this model using an exemplar generalist mycophagist, the swamp wallaby (Wallabia bicolor). We show that swamp wallabies disperse fungal spores hundreds of meters-and occasionally up to 1,265 m-from the point of consumption, distances that are ecologically significant for many mycorrhizal fungi. In addition to highlighting the ecological importance of swamp wallabies as dispersers of mycorrhizal fungi in eastern Australia, our simple modeling approach provides a novel and effective way of empirically describing spore dispersal by a mycophagous animal. This approach is applicable to the study of other animal-fungi interactions in other ecosystems.

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.

Ecosystem engineering by digging mammals: effects on soil fertility and condition in Tasmanian temperate woodland

Many small- and medium-sized mammals dig for their food. This activity potentially affects soil condition and fertility. Digging is well developed especially in Australian mammals, many of which have recently become rare or extinct. We measured the effects of digging by mammals on soil in a Tasmanian temperate dry sclerophyll forest with an intact mammal community. The density of diggings was 5812 ha^-1, affecting 11% of the forest floor. Diggings were created at a rate of around 3113 diggings ha^-1 yr^-1, disturbing 6.5% of the forest floor and displacing 7.1 m³ ha^-1 of soil annually. Most diggings were made by eastern bettongs (Bettongia gaimardi) and short-beaked echidnas (Tachyglossus aculeatus). Many (approx. 30%) fresh diggings consisted of re-excavations of old diggings. Novel diggings displaced 5 m³ ha yr^-1 of soil. Diggings acted as traps for organic matter and sites for the formation of new soil, which had higher fertility and moisture content and lower hardness than undisturbed topsoil. These effects on soil fertility and structure were strongest in habitats with dry and poor soil. Creation of fine-scaled heterogeneity by mammals, and amelioration of dry and infertile soil, is a valuable ecosystem service that could be restored by reintroduction of digging mammals to habitats from which they have declined or gone extinct.

Pyrodiversity is the coupling of biodiversity and fire regimes in food webs

Fire positively and negatively affects food webs across all trophic levels and guilds and influences a range of ecological processes that reinforce fire regimes, such as nutrient cycling and soil development, plant regeneration and growth, plant community assembly and dynamics, herbivory and predation. Thus we argue that rather than merely describing spatio-temporal patterns of fire regimes, pyrodiversity must be understood in terms of feedbacks between fire regimes, biodiversity and ecological processes. Humans shape pyrodiversity both directly, by manipulating the intensity, severity, frequency and extent of fires, and indirectly, by influencing the abundance and distribution of various trophic guilds through hunting and husbandry of animals, and introduction and cultivation of plant species. Conceptualizing landscape fire as deeply embedded in food webs suggests that the restoration of degraded ecosystems requires the simultaneous careful management of fire regimes and native and invasive plants and animals, and may include introducing new vertebrates to compensate for extinctions that occurred in the recent and more distant past.

This article is part of the themed issue ‘The interaction of fire and mankind’.

Wildlife in the line of fire: evaluating the stress physiology of a critically endangered Australian marsupial after bushfire

Australian native fauna are thought to be well adapted to fire-prone landscapes, but bushfires may still pose considerable challenges or stressors to wildlife. We investigated the impact of bushfire on the stress physiology of the woylie (brush-tailed bettong, Bettongia penicillata) a critically endangered Australian marsupial, and assessed whether fitness indices (body condition and parasite load) influenced stress physiology before and after the fire. We hypothesised that there would be a significant change in stress physiology indicators (in the form of faecal cortisol metabolites, FCM) following the fire, compared with the months previous. We trapped woylies (n = 19) at Whiteman Park Reserve in Perth, Western Australia, two days after a major bushfire and measured FCM concentration by enzyme immunoassay. Population-level comparisons of FCM were made between these samples and those collected in previous months (n = 58). While mean FCM varied by month of sample collection, it was not higher after the fire. We suggest that woylies may be able to maintain homeostasis through change (allostasis), at least in the period immediately after the fire. This is supported by our finding that FCM did not relate significantly to body condition or parasite load. Our results potentially highlight the physiological and behavioural adaptations of woylies to fire, which could be further explored in future studies.

Characteristics of mammal communities in Tasmanian forests: exploring the influence of forest type and disturbance history

Context With increasing pressure worldwide on forest habitat, it is crucial to understand faunal ecology to effectively manage and minimise impacts of anthropogenic habitat disturbance. Aims This study assessed whether differences in forest type and disturbance history were reflected in small to medium mammal communities found in Tasmania’s production forests. Methods Trapping was conducted in spring and summer, and autumn and winter during 2007–08 at four dry Eucalyptus forest sites (two regenerating after harvest and two in relatively undisturbed forest) in south-east Tasmania, and four wet Eucalyptus forest sites (two regenerating after harvest and two in relatively undisturbed forest) in north-east Tasmania. All sites were embedded within a matrix of mature or older aged regenerating forest. Key results Thirteen mammal species were recorded across all sites. There was no difference in species diversity or richness between forest type or disturbance regime, but species composition differed. Total number of individual animals and captures was influenced strongly by forest type and disturbance history, with most animals captured in the dry disturbed forest sites. Abundance of some species (e.g. bettongs and potoroos) was higher in disturbed sites than undisturbed sites. Brushtail possum numbers (adults and offspring), however, were lower in disturbed sites and populations displayed a male biased adult sex ratio and lower breeding frequency. Habitat structural complexity and vegetation diversity within core sites, and age structure of the forest in the surrounding landscape did not vary significantly, indicating that broad resource (food and refuge) availability was equivalent across sites. Conclusions In general, the small to medium mammals in this study did not appear to be significantly affected by forest harvesting in the medium term. Implications Although past harvesting altered the abundance of some habitat features (e.g. canopy cover, basal area of trees, and tree hollow availability), we suggest that the availability of such features in the surrounding landscape may mitigate the potential effects of disturbance on the species for which such habitat features are important.

Prescribed burning in a Eucalyptus woodland suppresses fruiting of hypogeous fungi, an important food source for mammals

Fruit bodies of hypogeous fungi are an important food source for many small mammals and are consumed by larger mammals as well. A controversial hypothesis that prescribed burning increases fruiting of certain hypogeous fungi based on observations in Tasmania was tested in the Australian Capital Territory to determine if it applied in a quite different habitat. Ten pairs of plots, burnt and nonburnt, were established at each of two sites prescribe-burnt in May 1999. When sampled in early July, after autumn rains had initiated the fungal fruiting season, species richness and numbers of fruit bodies on the burnt plots were extremely low: most plots produced none at all. Both species richness and fruit body numbers were simultaneously high on nonburnt plots. One of the sites was resampled a year after the initial sampling. At that time species richness and fruit body abundance were still significantly less on burnt plots than on nonburnt, but a strong trend towards fungal recovery on the burnt plots was evident. This was particularly so when numbers of fruit bodies of one species, the hypogeous agaric Dermocybe globuliformis, were removed from the analysis. This species strongly dominated the nonburnt plots but was absent from burnt plots in both years. The trend towards recovery of fruit body abundance in the burnt plots one year after the burn was much more pronounced with exclusion of the Dermocybe data. The Tasmanian-based hypothesis was based mostly on the fruiting of two fire-adapted species in the Mesophelliaceae. Neither species occurred on our plots. Accordingly, the results and conclusions of the Tasmanian study cannot be extrapolated to other habitats without extensive additional study. Implications for management of habitat for fungi and the animals that rely on the fungi as a food source are discussed.

Fire-related changes in biomass of hypogeous sporocarps at foraging points used by a tropical mycophagous marsupial

Changes in pre- and post-fire biomass of hypogeous fungal sporocarps remaining at locations where an endangered mycophagous marsupial, the northern bettong (Bettongia tropica), had foraged, were assessed in fire-prone sclerophyll forest in northeastern Australia. Low to medium intensity experimental fires were set during the late dry season in 1995 and 1996 and post-foraging biomass of sporocarps (expressed as biomass of sporocarps remaining at recent B. tropica diggings) was measured at unburnt and burnt sites at approximately six-week intervals for a period of 14 months. Post-foraging biomass was significantly higher at burnt sites immediately following fire compared with control sites, solely due to increased biomass of hypogeous species belonging to the family Mesophelliaceae. Several months after fire, post-foraging biomass was significantly higher on unburnt sites compared with very low biomass on burnt sites. Twelve months after fire, the biomass on burnt and unburnt sites was not significantly different, having returned to biomass observed pre-fire. All evidence points toward mesophellioid fungi being greatly more available to bettongs on recently burnt ground, but fire may make several other sporocarp taxa considerably less available several months following fire.

Ectomycorrhizal fungal communities in young forest stands regenerating after clearcut logging

The effects on the ectomycorrhizal fungal community of clearcut logging, which is used to harvest millions of hectares of ectomycorrhizal forest annually, has been studied for a number of years. Here, we review current knowledge of inoculum sources for ectomycorrhizal fungi in forests and then re-examine earlier studies of ectomycorrhizas on young trees in regenerating stands. We conclude that, taken separately from the effects of site preparation, the major impact of clearcut logging is to change the species composition of the ectomycorrhizal fungal community rather than to reduce the percentage of roots colonized. A thorough examination of site preparation treatments suggests that the changes in fungal species composition are driven by changes in the biology and chemistry of the soil environment after clearcutting as much as they are by loss or change in fungal inoculum. This is an important conclusion because it implies that these new ectomycorrhizal fungal communities are better adapted to the new conditions than the ones in the forest would have been. The shift in fungal species composition and diversity will have implications for seedling establishment and competition. The effects of individual fungi or diverse assemblages of fungi on seedling growth, and effects of changes in the ability of young trees to associate with a common mycelium are discussed. Contents Summary 399 I. Introduction 400 II. Population biology and inoculum potential of ectomycorrhizal fungi 401 III. Ectomycorrhiza development on seedlings regenerating after clearcut logging 402 IV. Which is the most important factor driving changes in the ECM fungal community after clearcut logging: inoculum loss or change in the below-ground environment? 406 V. Possible consequences for regenerating stands of species shifts in ectomycorrhizal fungi 414 VI. Conclusions 416.

Microbial biodiversity: approaches to experimental design and hypothesis testing in primary scientific literature from 1975 to 1999

Research interest in microbial biodiversity over the past 25 years has increased markedly as microbiologists have become interested in the significance of biodiversity for ecological processes and as the industrial, medical, and agricultural applications of this diversity have evolved. One major challenge for studies of microbial habitats is how to account for the diversity of extremely large and heterogeneous populations with samples that represent only a very small fraction of these populations. This review presents an analysis of the way in which the field of microbial biodiversity has exploited sampling, experimental design, and the process of hypothesis testing to meet this challenge. This review is based on a systematic analysis of 753 publications randomly sampled from the primary scientific literature from 1975 to 1999 concerning the microbial biodiversity of eight habitats related to water, soil, plants, and food. These publications illustrate a dominant and growing interest in questions concerning the effect of specific environmental factors on microbial biodiversity, the spatial and temporal heterogeneity of this biodiversity, and quantitative measures of population structure for most of the habitats covered here. Nevertheless, our analysis reveals that descriptions of sampling strategies or other information concerning the representativeness of the sample are often missing from publications, that there is very limited use of statistical tests of hypotheses, and that only a very few publications report the results of multiple independent tests of hypotheses. Examples are cited of different approaches and constraints to experimental design and hypothesis testing in studies of microbial biodiversity. To prompt a more rigorous approach to unambiguous evaluation of the impact of microbial biodiversity on ecological processes, we present guidelines for reporting information about experimental design, sampling strategies, and analyses of results in publications concerning microbial biodiversity.

Polymorphism of simple sequence repeats reveals gene flow within and between ectomycorrhizal Suillus grevillei populations

•  Gene flow within and between two populations of the ectomycorrhizal fungus Suillus grevillei is shown here using co-dominant simple sequence repeat (SSR) markers. •  Co-dominant SSR markers were developed for S. grevillei. Distribution and frequency of alleles at the three codominant SSR markers were analysed within two S. grevillei populations in two Larix Kaempteri stands located 700 m apart. •  Among eight SSR loci isolated from S. grevillei, five loci (designated SG1-5) were polymorphic and SG1-3 were co-dominant. Genets (73) previously identified by inter-simple sequence repeat markers at the Larix stands were divided by the combination of SG1-3 into 22 genotypes. Most of the SSR genotypes were spatially clustered, indicating that the dispersal distance of S. grevillei spores was relatively short. •  There was no conspicuous genetic differentiation within or between the two S. grevillei populations, indicating extensive gene flow. The spread of alleles within or between populations might be by repeats of short-distance spore dispersal rather than long-distance spore dispersal.

A Preliminary Note on Yeasts Associated With Fecal Pellets of Rodents and Marsupials of Atlantic Forest Fragments in Rio de Janeiro, Brazil

Yeasts had mean counts of above 106 CFU/g in the fecal pellets of small mammals from tropical forest fragments. Most of the 55 species isolated were fermentative ascomycetes, with the most frequent being Debaryomyces hansenii, Pichia membranifaciens and Issatchenkia orientalis, whereas Rhodotorula mucilaginosa was the most frequent yeast of basidiomycetous affinity.