Michelle Alice Jusino

Starting in 2019 in northern and central Florida, a thread blight caused by a previously undescribed fungus was observed with increasing frequency, affecting both hardwood and conifer hosts with a higher prevalence in wet, shaded environments. This emerging disease, called relampago blight, is caused by the fungus Parvodontia relampaga and is characterized by its distinct white, lightning-shaped rhizomorphs (fungal cords) that grow on the stems and branches of affected host plants. When the fungus fully develops, it can also grow on the undersides of plant leaves, causing dieback of leaves and small branches. This fungus has been found on a wide array of host plants and detected in 31 counties throughout Florida.

Mushrooms are often moved across and between continents, but how invasive mushrooms impact the biodiversity of animals or microbes in novel ranges remains unknown. The deadly Amanita phalloides (or death cap) has invaded local forests in California and is now common throughout the western coast of North America. The fungus produces a plethora of specialized metabolites (SMs), and while SMs may play an essential role in protecting spores, what the SMs are protecting spores against remains mysterious. Building on long-standing claims, we hypothesize the toxins are a defense against potentially antagonistic invertebrates, and we further hypothesize the metabolites act against microbial competitors in soils. We believe SMs play a role in fungal invasion biology, and the Californian A. phalloides’ have an ecological advantage because they have escaped co-evolved natural enemies and their SMs are acting as a novel defense against naïve competitors lacking co-evolved resistance to the death cap’s chemistry. To test our hypotheses, we asked 1) do native and invasive death caps host unique invertebrates compared to other co-occurring Amanita? and 2) do invasive death caps host a lower diversity of invertebrates compared to native European death caps? Next, we asked 3) is there a change in microbial diversity and community composition when the death cap’s toxins leach into Californian soils? We characterized the communities of invertebrates found in A. phalloides and related Amanita mushrooms collected from invasive and native ranges using metabarcoding. Our data support our hypothesis, showing the death caps have unique invertebrate communities compared to co-occurring Amanita and Californian death caps house significantly lower invertebrate biodiversity compared to native death caps. We are now characterizing the microbial communities in soils collected from beneath invasive A. phalloides’ and testing for the presence of toxins and metabolites. Our preliminary results confirm the toxins are leaching into the native soils of California. By characterizing fungal and bacterial communities, we are describing differences in microbial diversity and composition in the presence of the death cap’s SMs. Our research lays the foundation for understanding how invasive mushrooms change local biodiversity and mechanisms behind their successful advancement.

Pinus densa, an endemic and keystone tree in Florida's endangered pine rocklands ecosystem, faces increasing threats from sea level rise and salt intrusion. Ectomycorrhizal (ECM) fungi are critical for pine recruitment and survival, yet their diversity and response to salinity in this ecosystem have been unstudied. We used metabarcoding to survey the naturally occurring ECM fungi on the roots of mature Pinus densa at eight field sites with varying elevations, soil salinities, habitat patch sizes and distances from the ocean, followed by a manipulative greenhouse experiment to assess potential impacts of rising salinity, with four salinity levels on P. densa seedlings in soils that spanned a salinity gradient to evaluate survival and shifts in ECM communities. Results show that salinity stress threatens both P. densa and its ECM symbionts, with ECM fungal richness positively correlated with elevation and negatively correlated with salinity. Habitat patch size, distance from the ocean and soil pH showed no significant effect on richness, and pH was less predictive of community structure. In seedlings, higher salinity was associated with greater mortality and shifts in ECM community composition favouring Rhizopogon species and Pezizales taxa. These findings underscore the susceptibility of ECM fungi to increased salinity, which may disrupt mutualisms critical for coastal resilience. Understanding how salinity affects mutualistic fungi can inform predictions on the vulnerability of other coastal ecosystems to climate change and sea level rise.

Fungi are widely consumed across the animal kingdom for nutritional and defensive benefits. Millipedes, among the first air-breathing land animals, were also among the first terrestrial fungivores. As detritus-eating omnivores, most millipedes regularly consume fungi. Millipede diets diverged ∼200 million years ago, when obligate fungivorous millipedes (subterclass Colobognatha) diverged from their detritivorous counterparts. Despite their global distribution and uncommon diet, little is known about the association between Colobognaths and the fungi they consume. In 2019, surveys of fungal communities associated with the Colobognath Brachycybe lecontii revealed associations with at least 176 genera of culturable fungi. Given the known biases of culture-based approaches, a more comprehensive survey of B. lecontii ’s fungal microbiome using amplicon sequencing was undertaken. In this study, we generated amplicon sequence data to look for associations between fungi and B. lecontii , and to determine if patterns of fungal diversity are millipede- or habitat-driven. Altogether, the fungal microbiome of B. lecontii encompassed 620 fungal genera and 100 orders. Despite much greater observed fungal diversity in the amplicon-based study, sampling was likely not sufficient to capture the full diversity of fungi associated with B. lecontii . Taxonomic and functional diversity were significantly influenced by site and colony, indicating that community structure is shaped by geography and habitat. It remains unknown whether these findings are representative of the larger patterns of fungal diversity for the entire millipede subterclass. Nevertheless, the obligate fungivorous lifestyle employed by these long-extant animals may provide important clues regarding fungal diversity and function.

Cistaceae are shrubs, subshrubs and herbs that often occur in stressful, fire-prone or disturbed environments and form ectomycorrhizal (ECM) associations with symbiotic fungi. Although some Cistaceae are long-lived shrubs that grow to significant size, others are herbaceous annuals or short-lived plants. Thus, Cistaceae are atypical ECM hosts that are fundamentally different in their biology from trees that are the more typically studied ECM hosts. The Mediterranean region is the center of diversity for Cistaceae and the ectomycorrhizal fungi associated with Cistaceae hosts have primarily been studied in Europe, North Africa, and the Middle East. Mediterranean Cistaceae often host diverse communities of ECM fungi, but they also act as hosts for some ECM fungi that putatively show host-specificity or strong host preference for Cistaceae (including species of Delastria, Hebeloma, Terfezia, and Tirmania). The ECM associations of Cistaceae in North America, however, remain highly understudied. Here we use fungal DNA metabarcoding to document the ectomycorrhizal fungal communities associated with Crocanthemum and Lechea (Cistaceae) in open, fire-prone sandhill habitats in north Florida. At each site we also sampled nearby Pinus to determine whether small, herbaceous Cistaceae have specialized ECM fungi or whether they share their ECM fungal community with nearby pines. The ECM communities of Florida Cistaceae are dominated by Cenococcum (Ascomycota) and Russula (Basidiomycota) species but were also significantly associated with Delastria, an understudied genus of mostly truffle-like Pezizales (Ascomycota). Although many Cistaceae ECM fungi were shared with neighboring pines, the ECM communities with Cistaceae were nonetheless significantly different than those of pines.

Aquatic fungi drive important ecosystem processes, which may be affected by anthropogenic stressors, including changes in water quality. However, due to the great diversity of aquatic fungi, our understanding of the relationships among water quality variables, fungal community composition, and ecosystem function remains incomplete. Here, we show that aquatic fungal community structure and functional diversity correlate strongly with water quality. We used a multi‐marker survey of environmental DNA and long‐term water quality data to survey 17 stream, pond, and tidal creek sites within a coastal drainage network in southeastern Virginia, USA, targeting both the ITS2 and LSU barcoding regions. The community composition of Chytridiomycota and Ascomycota (fungal phyla) and aquatic hyphomycetes (a functional group) were strongly correlated with habitat type and water quality variables. Functional diversity of aquatic fungi decreased with warmer water, due mainly to the reduced richness of saprotrophic groups, and increased with total particulate phosphorus, due to the richness of algal parasites. Community dissimilarity analyses of samples using both ITS2 and LSU yielded consistent results, but per‐sample alpha diversity differed. This work reveals a surprising degree of local variation in aquatic fungal community composition and functional diversity within a coastal watershed, which was coupled with variation in water quality variables. Furthermore, eDNA sampling is an effective and efficient means to accurately characterize diverse aquatic fungal communities with exciting implications for addressing basic and applied research questions. Our work supports the prediction that community composition and functional diversity of aquatic fungi are impacted by impaired water quality and global change.

Invasive plants, which cause substantial economic and ecological impacts, acquire both pathogens and beneficial microbes in their introduced ranges. Communities of fungal endophytes are known to mediate impacts of pathogens on plant fitness but few studies have examined the temporal dynamics of fungal communities on invasive plants. The annual grass Microstegium vimineum, an invader of forests and riparian areas throughout the eastern United States, experiences annual epidemics of disease caused by Bipolaris pathogens. Our objective was to characterize the dynamics of foliar fungal communities on M. vimineum over a growing season during a foliar disease epidemic. First, we asked how the fungal community in the phyllosphere changed over 2 months that corresponded with increasing disease severity. Second, we experimentally suppressed disease with fungicide in half of the plots and asked how the treatment affected fungal community diversity and composition. We found increasingly diverse foliar fungal communities and substantial changes in community composition between timepoints using high-throughput amplicon sequencing of the internal transcribed spacer 2 region. Monthly fungicide application caused shifts in fungal community composition relative to control samples. Fungicide application increased diversity at the late-season timepoint, suggesting that it suppressed dominant fungicide sensitive taxa and allowed other fungal taxa to flourish. These results raise new questions regarding the roles of putative endophytes found in the phyllosphere given the limited number of pathogens known to cause disease on M. vimineum in its invasive range.

Summary: Forest fungal communities are shaped by the interactions between host tree root systems and the associated soil conditions. We investigated how the soil environment, root morphological traits, and root chemistry influence root‐inhabiting fungal communities in three tropical forest sites of varying successional status in Xishuangbanna, China. For 150 trees of 66 species, we measured root morphology and tissue chemistry. Tree species identity was confirmed by sequencing rbcL, and root‐associated fungal (RAF) communities were determined using high‐throughput ITS2 sequencing. Using distance‐based redundancy analysis and hierarchical variation partitioning, we quantified the relative importance of two soil variables (site average total phosphorus and available phosphorus), four root traits (dry matter content, tissue density, specific tip abundance, and forks), and three root tissue elemental concentrations (nitrogen, calcium, and manganese) on RAF community dissimilarity. The root and soil environment collectively explained 23% of RAF compositional variation. Soil phosphorus explained 76% of that variation. Twenty fungal taxa differentiated RAF communities among the three sites. Soil phosphorus most strongly affects RAF assemblages in this tropical forest. Variation in root calcium and manganese concentrations and root morphology among tree hosts, principally an architectural trade‐off between dense, highly branched vs less‐dense, herringbone‐type root systems, are important secondary determinants.