Allison Walker

Acadia University · Department of Biology

Marine fungal communities of created salt marshes of differing ages were compared with those of two reference natural salt marshes. Marine fungi occurring on the lower 30 cm of salt marsh plants Spartina alterniflora and Juncus roemerianus were inventoried with morphological and molecular methods (ITS T-RFLP analysis) to determine fungal species ri...

Saltmarshes are highly productive ecosystems that provide nursery and refuge habitat for animals, buffer storm-wave effects, and stabilize coastlines. Unfortunately, saltmarshes are in decline due to several cumulative stressors. Beneficial root-associated fungi are known to colonize >80% of land plants, but are understudied in intertidal zones. We...

Despite the rapid development of molecular techniques relevant for natural product research, culture isolates remain the primary source from which natural products chemists discover and obtain new molecules from microbial sources. Techniques for obtaining and identifying microbial isolates (such as filamentous fungi) are thus of crucial importance...

Terrestrial fungi play critical roles in nutrient cycling and food webs and can shape macroorganism communities as parasites and mutualists. Although estimates for the number of fungal species on the planet range from 1.5 to over 5 million, likely fewer than 10% of fungi have been identified so far. To date, a relatively small percentage of describ...

The use of naturally occurring epiphytic lichens can be an effective tool for regional monitoring of mercury (Hg) and other potentially toxic elements (PTEs). Nova Scotia, Canada is a hotspot for mercury and other trace metal accumulation in ecosystems; partially attributed to long-range transport of air pollution. The relative contribution of loca...

A comprehensive literature review of mycodiversity in sandy beaches and oceanic environments in Mexico is presented through the analysis of published works from 1949 to early 2023. In addition, four unexplored sandy beaches in the Pacific Ocean and Gulf of California were sampled in order to fill knowledge gaps in terms of sampling biases. Marine f...

Marine fungi play an integral role in the decomposition of intertidal organic substrata but remain understudied in cold-water habitats including Atlantic Canada. Marine inundated wood from the intertidal zone was sampled from 30 sites along the Bay of Fundy coastline in Nova Scotia, Canada. Wood types studied included attached and loose intertidal...

Early research on marine fungi was mostly descriptive, with an emphasis on their diversity and taxonomy, especially of those collected at rocky shores on seaweeds and driftwood. Subsequently, further substrata (e.g. salt marsh grasses, marine animals, seagrasses, sea foam, seawater, sediment) and habitats (coral reefs, deep-sea, hydrothermal vents,...

Novel species of fungi described in this study include those from various countries as follows: Australia , Agaricus albofoetidus , Agaricus aureoelephanti and Agaricus parviumbrus on soil, Fusarium ramsdenii from stem cankers of Araucaria cunninghamii , Keissleriella sporoboli from stem of Sporobolus natalensis , Leptosphaerulina queenslandica and...

Marine macroalgae are a polyphyletic group of photosynthetic eukaryotes and play critical roles in oxygen production, as primary producers, and in providing physical habitat structure. They harbor diverse microbial communities, including mutualistic, commensalistic, and parasitic fungi. These fungi may be obligately or facultatively marine and symb...

As an ecotone, sandy beaches exist within a multi-dimensional mesh of environmental gradients, shaped by numerous parameters (e.g. temperature, humidity, wave action, sand particle size and salinity). These limit the proliferation of a narrow group of fungal species. Obligate arenicolous marine fungi are an ecological assemblage of sand-associated...

Coastal salt marshes provide many ecosystem services; however, little is known of the biology of decomposer taxa in these systems. This study employed aboveground and belowground litterbags to characterize the fungal and mite communities associated with the dominant salt marsh grass, Sporobolus pumilus, in the Minas Basin, Nova Scotia. Decompositio...

Raptor pellets are regularly encountered in the field in a variety of habitats. Where multiple species of similar-sized raptors are sympatric, there can be uncertainty about which species produced a pellet based on visual assessments alone. We developed a DNA barcoding protocol that used environmental DNA (eDNA) to identify birds of prey that had p...

Despite the ecological importance of fungi, we still know little about their diversity in Canada. One of the largest hurdles to implementing fungal conservation initiatives is the lack of fungal distribution data. As anthropogenic impacts accelerate the speed of environmental change, it is imperative that we fill this major information gap, critica...

Virtually all examined plant species harbour fungal endophytes which asymptomatically infect or colonize living plant tissues, including leaves, branches, stems and roots. Endophyte-host interactions are complex and span the mutualist–pathogen continuum. Notably, mutualist endophytes can confer increased fitness to their host plants compared with u...

The microbiome, an influential factor affecting plant health and growth, is attracting increasing interest with respect to wine grape production. The purpose of this study was to characterize the microbiome (fungi and bacteria) of the soil, cover crop roots and grape (Vitis spp.) roots across rootstock and depth in a cool climate, organic vineyard....

Despite harsh conditions provided by wave action, salinity, UV exposure, and other pressures, lichens provide most of the substrate cover in the rocky littoral zone. We documented the vertical zonation and general ecology of several littoral members of the lichenized ascomycete family Verrucariaceae from 7 sites along Nova Scotia's Bay of Fundy coa...

We review what is known about ecosystem service (ES) delivery from agricultural dykelands and tidal wetlands around the dynamic Bay of Fundy in the face of climate change and sea-level rise, at the outset of the national NSERC ResNet project. Agricultural dykelands are areas of drained tidal wetland that have been converted to agricultural lands an...

Salt marshes are ecosystems of significant ecological importance for coastal stability and fundamental roles in marine ecosystems. Salt marshes are declining due to anthropogenic and natural causes including sea level rise. Coastal restoration efforts have increased worldwide, but many fail in long-term coastal stability. We used a naturally occurr...

Eastern Mountain Avens (Geum peckii Pursh, Rosaceae) is a globally rare and endangered perennial plant found only at two coastal bogs within Digby County (Nova Scotia, Canada) and at several alpine sites in the White Mountains of New Hampshire (USA). In Canada, the G. peckii population has declined over the past forty years due in part to habitat d...

Crocanthemum canadense (L.) Britt. (Cistaceae) is critically imperiled in Nova Scotia. The decline of Nova Scotian C. canadense is largely due to the loss of the Annapolis Valley sand barrens habitat. Fungal symbionts may aid in nutrient and water acquisition as well as plant defenses. The role of fungal associations with C. canadense is unknown; o...

Fungi are an important and understudied component of coastal biomes including sand beaches. Basic biogeographic diversity data are lacking for marine fungi in most parts of the world, despite their important role in decomposition. We examined intertidal fungal communities at several United States (US) Gulf of Mexico sand beach sites using morpholog...

Globally, marine sandy beaches face increasing anthropogenic pressures. Long-term maintenance of their functional capacities depends strongly on robust autochthonous biotic community baseline data. However, fine-scale temporal patterns remain poorly understood in human-impacted sites, limiting our knowledge of beach response to stressors. Marine ar...

The polyphyletic group of black fungi within the Ascomycota (Arthoniomycetes, Dothideomycetes, and Eurotiomycetes) is ubiquitous in natural and anthropogenic habitats. Partly because of their dark, melanin-based pigmentation, black fungi are resistant to stresses including UV-and ionizing-radiation, heat and desiccation, toxic metals, and organic p...

We surveyed Spartina saltmarsh sediment rhizosphere fungal communities at three salt marshes and two timepoints in coastal Nova Scotia. Based on ITS2 Illumina miSeq rDNA data and multivariate analysis, neither sediment zone nor collection period correlated with fungal ASV richness, but collection site did. However, Shannon diversity indicated that...

Fungi critically impact the health and function of global ecosystems and economies. In Canada, fungal researchers often work within silos defined by sub-discipline and institutional type, complicating the collaborations necessary to understand the impacts fungi have on the environment, economy, and plant and animal health. Here, we announce the est...

Geum peckii (Rosaceae), the Eastern Mountain Avens, is a small herbaceous plant that is listed as endangered federally and provincially. In Canada, this species is found in bogs on Brier Island and Harris Lake, Digby County, Nova Scotia. The only other population outside of Canada is in New Hampshire (USA). To enhance conservation research of this...

We present the first records of fungi associated with feathers from seabirds and sea ducks in the Canadian Arctic and sub-Arctic. Birds sampled in Nunavut and Newfoundland (Canada) included the Common Eider (Somateria mollissima), King Eider (S. spectabilis), Black-legged Kittiwake (Rissa tridactyla), Northern Fulmar (Fulmarus glacialis), Glaucous...

Fungi are present in saline environments that can be broadly categorized as either open ocean or intertidal (coastline) habitats. Many ecological niches exist within these environments, in which fungi adapted to marine conditions may act as saprobes, pathogens, or symbionts. These fungi have a substantial impact on ecosystem functions such as nutri...

Many field-collected fungal specimens are maintained in herbaria worldwide. These specimens contain an untapped wealth of taxonomic and ecological fungal biodiversity information. However, DNA can be difficult to obtain from preserved specimens. We present a DNA barcoding protocol specifically for preserved fungal specimens (ascomycetes and basidio...

Fusarium basal rot (FBR) caused by Fusarium oxysporum f. sp. cepae (FOC) affects onion production worldwide. Despite current control measures, (e.g. 4+ year crop rotations and fungicide application,) disease incidence is increasing in Nova Scotia (NS). This increase causes yearly economic losses of up to 20% onion production value in the Annapolis...

Since 2010, an unknown fungus in the Gnomoniaceae has been found on overwintered leaves and petioles of Styrax obassia (Styracaceae) in Japan. This fungus is characterized by dark brown immersed or partially erumpent ascomata with long necks and fusiform to obovoid asci each with an acute or long tapering stipe. Each ascus bears eight fusiform to f...

Biochar is gaining attention as an organic soil amendment that can increase plant yields and improve soil fertility. We studied the effect of biochar on the growth of fowl mannagrass (Glyceria striata (Lam.) Hitchc.) (Poaceae), propagated in a greenhouse for future re-introduction into restored wetlands. Three different application rates (10%, 50%,...

We describe the complete mating-type (MAT) locus for Phialocephala scopiformis Canadian Collection of Fungal Cultures (DAOMC) 229536 - a basal lineage within Vibrisseaceae. This strain is of interest due to its ability to produce the important antiinsectan rugulosin. We also provide some of the first insights into the genome structure and gene inve...

Despite the recent surge in mitochondrial (mt) genome sequencing, Kingdom Fungi remains underrepresented with respect to mtDNA. We describe the 36,919 bp mt genome of the conifer needle endophyte, Phialocephala scopiformis DAOMC 229536 (Helotiales, Ascomycota). This strain of P. scopiformis is of interest to the Canadian forestry industry as it pro...

Currently the spatial patterns of airbourne mercury associated with Nova Scotia lichens are largely unknown. Nova Scotia lichens are poorly represented in the online GenBank sequence database. We collected portions of a range of lichen species, with GPS coordinates and habitat data from opportunistically-selected locations throughout the province....

We present the first characterization of fungal community diversity of natural mixed-species biofilms on artificial marine reefs. Four artificial reefs in the Mississippi (MS) Sound, USA, representing low-profile (underwater) and high-profile (periodically air-exposed) conditions were sampled every 3 months over a 23-month period to investigate cha...

The discovery of new natural products from fungi isolated from substrata in marine environment has increased dramatically over the last few decades, cumulating in over 1000 new metabolites. The term ‘marine-derived fungi’ is used extensively in these reports, and it refers to the environment from which the fungi are isolated, in contrast to the cla...

We present the full genome of Phialocephala scopiformis DAOMC 229536 (Helotiales, Ascomycota), a foliar endophyte of white spruce from eastern Quebec. DAOMC 229536 produces the anti-insectan compound rugulosin, which inhibits a devastating forestry pest, the spruce budworm. This genome will enable fungal genotyping and host-endophyte evolutionary g...

Foliar endophytes of white pine were isolated from trees at a site in New Brunswick (Canada) and grown in liquid culture. Oxford disk bioassays of the resulting extracts against yeast showed that, of the 86 strains tested, 22 produced antifungal extracts. The resulting extracts were screened by LC-MS and showed variability in metabolite production,...

During three decades of research on conifer endophytes of the Acadian forest, numerous insights have been gained in conifer-fungal ecology and secondary metabolite production. Recently, we have explored endophyte assemblages of understory plants commonly occurring with pine. Here we report for the first time the production of the potent antifungal...

Phialocephala scopiformis is a foliar fungal endophyte of white spruce that produces the anti-insect compound rugulosin and other compounds in lower amounts. Seedlings inoculated with this and other toxigenic endophytes have increased tolerance to the spruce budworm, Choristoneura fumiferana. The presence of rugulosin in the diet and in needles inf...

Novel species of microfungi described in the present study include the following from South Africa: Cercosporella dolichandrae from Dolichandra unguiscati, Seiridium podocarpi from Podocarpus latifolius, Pseudocercospora parapseudarthriae from Pseudarthria hookeri, Neodevriesia coryneliae from Corynelia uberata on leaves of Afrocarpus falcatus, Ram...

Plasmodiophora diplantherae is known to occur throughout the pantropical distribution of its host, the seagrass genus Halodule. However, records in the subtropical region are limited to Tampa Bay, FL where it was detected once during an examination of herbar-ium specimens of H. beaudettei collected in December 1951 (den Hartog 1965) and to Fort Pie...

Five new species of Clavulina (Clavulinaceae, Cantharellales, Basidiomycota) are described from the Pakaraima Mountains of Guyana, occurring in rain forests dominated by the ectomycorrhizal tree Dicymbe corymbosa (Caesalpiniaceae). These clavarioid fungi have simple (i.e., unbranching) basidiomata, which is a relatively uncommon phenotypic feature...