The endangered northern bettong, Bettongia tropica, performs a unique and potentially irreplaceable dispersal role for truffle ectomycorrhizal fungi

Organisms that are highly connected in food webs often perform unique and vital functions within ecosystems. Understanding the unique ecological roles played by highly connected organisms and the consequences of their loss requires a comprehensive understanding of the functional redundancy among organisms. One important, yet poorly understood, food web is that between truffle‐forming ectomycorrhizal fungi and their mammalian consumers and dispersers. Mammalian fungal specialists rely on fungi as a food source, and they consume and disperse a higher diversity and abundance of fungi than do mycophagous mammals with generalist diets. Therefore, we hypothesise that mammalian fungal specialists are functionally distinct because they disperse a set of fungal taxa not fully nested within the set consumed by the combined generalist mammalian community (i.e. functional redundancy of fungal dispersal is limited). Using high‐throughput sequencing, we compared the fungal composition of 93 scats from the endangered fungal specialist northern bettong (Bettongia tropica) and 120 scats from nine co‐occurring generalist mammal species across three sites and three seasons. Compared with other generalist mammals, B. tropica consumed a more diverse fungal diet with more unique taxa. This aligns with our hypothesis that B. tropica performs a unique dispersal function for ectomycorrhizal truffle fungi. Additionally, modelling of mammalian extinctions predicted rapid loss of food web connections which could result in loss of gene flow for truffle taxa. Our results suggest that this system is sensitive to the extinction of highly connected specialist species like B. tropica and their loss could have consequences for ectomycorrhizal truffle fungal diversity. This suggests that the conservation of fungal specialists is imperative to maintaining ectomycorrhizal fungal diversity and healthy plant‐mycorrhizal relationships

Soil biotic and abiotic effects on seedling growth exhibit context-dependent interactions: evidence from a multi-country experiment on Pinus contorta invasion

The success of invasive plants is influenced by many interacting factors, but evaluating multiple possible mechanisms of invasion success and elucidating the relative importance of abiotic and biotic drivers is challenging, and therefore rarely achieved.We used live, sterile or inoculated soil from different soil origins (native range and introduced range plantation; and invaded plots spanning three different countries) in a fully factorial design to simultaneously examine the influence of soil origin and soil abiotic and biotic factors on the growth of invasive Pinus contorta.Our results displayed significant context dependency in that certain soil abiotic conditions in the introduced ranges (soil nitrogen, phosphorus or carbon content) influenced responses to inoculation treatments.Our findings do not support the enemy release hypothesis or the enhanced mutualism hypothesis, as biota from native and plantation ranges promoted growth similarly. Instead, our results support the missed mutualism hypothesis, as biota from invasive ranges were the least beneficial for seedling growth. Our study provides a novel perspective on how variation in soil abiotic factors can influence plant-soil feedbacks for an invasive tree across broad biogeographical contexts

The importance of declining mammalian fungal specialists for ectomycorrhizal fungal dispersal

Conservation is more than just preserving biodiversity but also preserving ecosystem processes. Understanding how loss of diversity can affect the functioning of ecosystems requires understanding of the system's functional redundancy. That is, how many species in the system perform similar roles and can compensate for the loss of similar species? In this thesis, I investigate the functional redundancy among mammal species involved in an important, yet poorly understood, interaction between three very different organisms; fungi, plants and mammals. Mycorrhizal fungi associate mutualistically with the roots of many plant species. In exchange for nutrients accessed by the fungi, the plants provide the fungus with sugars (carbohydrates) from their photosynthesis. Many mycorrhizal species form below-ground fruit-bodies (truffles) that rely on mammals for spore dispersal. This interaction led to the hypothesis that mammals are important for fungal species diversity, plant-fungal interactions and ecosystem functioning. However, little is known about how truffles contribute to the structure of mycorrhizal communities. For instance, are truffle taxa that mammals disperse important components of the mycorrhizal community as a whole and thus, can mammals influence mycorrhizal community structure? Globally, many different mammals are known to consume and disperse truffles, some to a much greater degree than others. For example, the term 'fungal specialists' is used for mammals that consume fungi for the majority of their diet (>50%, relative to other food types). Often as a consequence, fungal specialists can also consume (and disperse) a diversity of truffle species. Many mammals with generalist diets, on the other hand, frequently consume truffle fungi opportunistically. Hence, individual mammals with generalist diets often consume a lower diversity of truffle fungal species than mammals with fungal specialist diets. However, currently it is unknown whether the combined fungal dispersal role of mammals with generalist diets equates to that of a specialist (i.e.: is there functional redundancy in the system?). In other words, if a fungal specialist were to become extinct in an ecosystem, is there enough functional redundancy that the dispersal roles for truffle fungi will be fulfilled by the remaining mammals with generalist diets? Understanding this interaction is particularly relevant to Australian ecosystems. Unfortunately, Australia has the highest rate of mammal extinction and decline, including fungal specialists within the family Potoroidae. Additionally, the majority of Australia's native forests are dominated by woodland trees that host truffle-producing ectomycorrhizal (ECM) fungi (for instance, Eucalyptus, Corymbia, Allocasuarina, Melaleuca). In this thesis, I addressed a number of research questions aimed at better understanding how the loss of mammalian diversity could potentially impact on truffle populations and mycorrhizal communities. These research results pave the way to understanding how loss of mammal diversity could influence fungus-plant interactions and ecosystem functioning. In Chapter Two, a meta-analysis brings together discordant data on fungal diets of mammals across Australia. These data were used to ask whether there is functional redundancy in fungal dispersal roles among mammalian fungal specialists and mammals with generalist diets. Despite detecting a sampling bias in the literature, on average, fungal specialists consumed fungi at a higher diversity and abundance, and more consistently across seasons than mycophagous mammals with generalist diets, indicating little functional redundancy in general. However, some generalist mammals ate a fungal species diversity on par with specialists (Rattus fuscipes, Perameles nasuta and Wallabia bicolor) indicating that there may be functional redundancy in some systems. Studies presented in this meta-analysis utilised differences in morphological characters of spores to identify fungal species, however, this technique has limited resolution with some groups (e.g. Russulaceae). Additionally, much of the data could not be compared between studies because many taxa were undescribed (e.g. Unknown species 1). Results from Chapter Two are built on in Chapter Three, by directly comparing fungal diets of a specialist and nine co-occurring generalist fungal diets using modern DNA sequencing techniques. This direct comparison eliminated the biases associated with using data collected from different studies and allowed a higher resolution of fungal species diversity to be measured. I found that the fungal specialist, Bettongia tropica (northern bettong), consumed a significantly higher diversity and more unique mycorrhizal and truffle fungal taxa than the combined diets of the generalists. Bettongia tropica also had a significantly different fungal community in their diets. These trends were consistent across sites and seasons. These data suggest that there is little functional redundancy in this ecosystem and indicates that truffle fungi populations may be detrimentally impacted by the loss of the endangered B. tropica. To further understand whether potential loss of truffle taxa, via loss of specialists, would have detrimental impacts on fungal-plant interactions, a good understanding of the structure of the mycorrhizal community must first be obtained. Yet, particularly in Australia, little is known about the structure of mycorrhizal communities and how truffle diversity contributes to it. In Chapter Four, this knowledge gap was addressed by measuring the mycorrhizal community at different scales using molecular methods. I found that the dominant mycorrhizal fungal taxa associating with plant roots were truffle taxa found in mycophagous mammalian diets. Over 80% of truffle taxa associating with roots were within the diet of the fungal specialist, and this percentage was just over half (52%) for generalist mammals. These data indicate that mammals, particularly those with specialist fungal diets, are important in shaping ECM fungal communities. This adds credence to the hypothesis that the loss of mammals could have detrimental effects on ECM communities and fungal-plant relationships. Overall, my thesis addressed key knowledge gaps in the interactions between mycophagous mammals, ECM fungi and their host plants. This work also highlights previously overlooked ramifications of native mammal loss in Australia, drawing particular attention to specialist mycophagists whose role in maintaining the diversity of ECM truffle fungal taxa may be irreplaceable

Essential skills for young mycologists

Students attracted to a research career in mycology are often interested in approaches that can help build towards such a professional future. In light of this need, a workshop in mycological skills was held recently for students and early career researchers (ECRs) at the 2015 scientific meeting of the Australasian Mycological Society (AMS) in Canberra, Australia. The workshop was organized and chaired by the AMS student representative Susan Nuske, and featured four AMS members with different areas of mycological research expertise. The presenters were Ana Traven (Medical Mycology), Jeff Powell (Fungal Ecology), Diana Leemon (Applied Mycology), and Tom May (Fungal Systematics). Their brief was to outline what had inspired them to become a mycologist, the skills they had acquired which had been instrumental in their careers, and how young scientists could gain these skills

Common species affects the utility of non-invasive genetic monitoring of a cryptic endangered mammal: the bridled nailtail wallaby

Non-invasive methods of monitoring wild populations (such as genotyping faeces or hair) are now widely used and advocated. The potential advantages of such methods over traditional direct monitoring (such as live capture) are that accuracy improves because sampling of non-trappable individuals may be possible, species in difficult and remote terrain can be surveyed more efficiently, and disturbance to animals is minimal. Few studies have assessed the effects of interactions between species on remote sampling success. We test the use of non-invasive monitoring for the cryptic, forest-dwelling, solitary and endangered bridled nailtail wallaby (Onychogalea fraenata) that is sympatric with the ecologically similar and more common black-striped wallaby (Macropus dorsalis). Six types of hair traps were tested for 3668 trap days, and hairs were caught with about a 10% success rate. Camera traps showed that baited hair traps targeted both wallaby species. We microscopically identified hair as bridled nailtail wallaby or black-striped wallaby. We compared these hairs and their genotypes (using seven microsatellite loci) with known bridled nailtail wallaby hairs and genotypes derived from animal trapping. Trapped bridled nailtail wallaby hairs had characteristics that could be mistaken for black-stripe wallaby hairs; characteristics were not diagnostic. Genetic assignment tests consistently differentiated the known bridled nailtail wallaby samples from identified black-striped wallaby samples, however genetic overlap between most of the microsatellite markers means that they are not suitable for species identification of single samples, with the possible exception of the microsatellite locus B151. With similar trapping effort and within the same area, live-capture mark-recapture techniques estimated 40-60 individuals and non-invasive methods only detected 14 genotypes. A species-specific genetic marker would allow more efficient targeting of bridled nailtail wallaby samples and increase capture rates

The evolution of sociality in small, carnivorous marsupials: The lek hypothesis revisited

One of the few mammal species reported to have a mating system of lek promiscuity is the tree-hollow nesting marsupial, the agile antechinus, Antechinus agilis. Past conclusions about its mating system have been based on seasonal changes in social group size, sex-specific nest switching and space use. Thermoregulation has also been suggested as an explanation for variation in social behaviour in this species and its relatives. We tested predictions of the lekking and thermoregulation hypotheses to explain sociality in cavity nesting antechinuses using published data, and new data on brown and subtropical antechinuses. We found that across four species, social group size is negatively correlated with daily minimum temperature, but not with timing of breeding. Females have a matrilineal fission-fusion social system, which continues during the brief mating season, and males range increasingly further throughout their lives, contacting as many females as possible in nests. Males show no indication of fission-fusion sociality. All evidence in species other than A. agilis, and some data on A. agilis, indicate a mating system of scramble polygyny, and not lek promiscuity. We conclude that across species, thermoregulation is the main reason for seasonal variation in nesting group size in both sexes