Department of Biology

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Browsing Department of Biology by Subject "Biology"

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    Fungal species selection during ectomycorrhizal grazing by Collembola
    (Symbiosis, 2019-05) LeFait, Alexis; Gailey, James; Kernaghan, Gavin
    Collembola are one of the most abundant groups of arthropods, with fungi being an important part of their diet. Collembolan grazing of ectomycorrhizae (ECM) can sever connections between the host root and hyphal networks, interrupting nutrient flow and negatively impacting plant growth. Much of the previous information on interactions between Collembola and ECM has been based on mycelium grown in pure culture, which has artificially high nutrient levels and may lack physical and chemical grazing deterrents seen when ECM form on plant roots. We investigated Collembola feeding preferences by offering naturally occurring ECM, identified by ITS sequencing, to Folsomia candida and Protaphorura armata. We also assessed the gut content fungi of Folsomia collected in a mature Pinus strobus stand. We found that some ECM types, including the Tricholoma aestuans, Piloderma bicolor and the tuburculate ECM of Suillus spraguei, were readily grazed, while Cenococcum geophilum and Lactarius vinaceorufescens were unpalatable. Fungi forming unpalatable ECM were readily grazed when not in symbiosis with the host root.
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    Fungal succession during the decomposition of ectomycorrhizal fine roots
    (Microbial Ecology, 2019) Gray, Logan; Kernaghan, Gavin
    Ectomycorrhizal (ECM) fine roots account for a substantial proportion of forest production and their decomposition releases large amounts of nutrients to the soil ecosystem. However, little is known about the fungi involved in ECM decomposition, including assemblages of fungal saprotrophs, endophytes, and the ECM fungi themselves. To follow fungal succession during the degradation of senescing fine roots, understory seedlings of Abies balsamea and Picea rubens at two sites in the Acadian forest of Nova Scotia were either severed at the root collar or left as controls. Root systems were collected sequentially over two growing seasons and assessed for fine root loss and ECM mantle integrity. ECM were identified by ITS-PCR and grouped into broad morphological categories. Fungal communities colonizing the senescing fine roots were also monitored by systematically constructing clone libraries over the course of the experiment. ECM with cottony, weakly pigmented mantles (e.g., Cortinarius) degraded within the first year. Those with cottony, but intensely pigmented mantles (Piloderma), and smooth mantles with weak pigmentation (Russulaceae) degraded more slowly. Smooth, melanized ECM (Cenococcum and Tomentella) generally maintained integrity over the course of the experiment. Rates of fine root loss and changes in ECM mantle integrity were positively correlated with soil temperature. ECM DNA was detected throughout the experiment, and was not replaced by that of saprotrophic species during the two seasons sampled. However, fungal root endophytes (e.g., Helotiaceae) initially increased in abundance and then decreased as mantles degraded, suggesting a possible role in ECM decomposition.