Comparison of Three Techniques for the Study of Aquatic Hyphomycete Communities

Shearer, Carol A.; Lane, L. C.

doi:10.1080/00275514.1983.12023713

Cited by 43 publications

(22 citation statements)

References 18 publications

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“…The inhospitality of the substrate surface, microbivory, or active interference among fungal species during conidial attachment or germination might be responsible for such a decline. At least during later stages, there is little evidence for interference between mycelia of different species of aquatic hyphomycetes, since considerable interspecific intermingling of hyphae occurs at very small spatial scales (11,28). We are currently examining the earliest phase of fungal colonization to determine if this stage presents a bottleneck for later fungal diversity on decaying leaves.…”

Section: Discussionmentioning

confidence: 99%

Determining Diversity of Freshwater Fungi on Decaying Leaves: Comparison of Traditional and Molecular Approaches

Nikolcheva

Cockshutt

Bärlocher

2003

Appl Environ Microbiol

169

129

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Traditional microscope-based estimates of species richness of aquatic hyphomycetes depend upon the ability of the species in the community to sporulate. Molecular techniques which detect DNA from all stages of the life cycle could potentially circumvent the problems associated with traditional methods. Leaf disks from red maple, alder, linden, beech, and oak as well as birch wood sticks were submerged in a stream in southeastern Canada for 7, 14, and 28 days. Fungal biomass, estimated by the amount of ergosterol present, increased with time on all substrates. Alder, linden, and maple leaves were colonized earlier and accumulated the highest fungal biomass. Counts and identifications of released conidia suggested that fungal species richness increased, while community evenness decreased, with time (up to 11 species on day 28). Conidia of Articulospora tetracladia dominated. Modifications of two molecular methods-denaturing gradient gel electrophoresis (DGGE) and terminal restriction fragment length polymorphism (T-RFLP) analysis-suggested that both species richness and community evenness decreased with time. The dominant ribotype matched that of A. tetracladia. Species richness estimates based on DGGE were consistently higher than those based on T-RFLP analysis and exceeded those based on spore identification on days 7 and 14. Since traditional and molecular techniques assess different aspects of the fungal organism, both are essential for a balanced view of fungal succession on leaves decaying in streams.Aquatic hyphomycetes belong to a phylogenetically heterogeneous group of true fungi that dominate the breakdown of leaves and other allochthonous detritus in streams and rivers (5, 15). Their activity increases the palatability of the substrate to detritus feeders. Macroinvertebrates discriminate between, and show preferences for, particular fungal species (2, 6, 26). To fully characterize the fungal contribution to leaf decay and invertebrate nutrition, the aquatic hyphomycete community must be subdivided into its constituent species. The same principle applies when investigating relationships between biodiversity and ecological functions-a topic that has attracted increasing attention in the last decade (18,33).Most of the fungal biomass on decaying leaves consists of vegetative (nonreproducing) hyphae that cannot be identified through conventional microscopy. To characterize community structure, leaf surfaces often are examined for sporulating structures (e.g., see references 7 and 30), or conidia released from the leaf are collected, counted, and identified (e.g., see reference 3). The obvious shortcoming to these protocols is that absence of conidia might be due to the absence of species or to the presence of nonsporulating mycelium. In the initial phase of fungal colonization, between the landing of conidia and their growth into a sporulating colony, newly arrived species will escape detection by traditional microscope-based techniques.Molecular approaches characterize nucleic acids that are present in all...

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Section: Discussionmentioning

confidence: 99%

Determining Diversity of Freshwater Fungi on Decaying Leaves: Comparison of Traditional and Molecular Approaches

Nikolcheva

Cockshutt

Bärlocher

2003

Appl Environ Microbiol

169

129

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“…The preparation of leaf discs for the assessment of fungal sporulation followed in general Shearer and Lane [20]. Leaf discs were incubated in their respective wells, filled with 2 ml of deionized water for 96 h at 20 AE 18C on an orbital shaker set at 55 rpm.…”

Section: Characterization Of the Leaf-associated Microbial Communitiesmentioning

confidence: 99%

Ecotoxicological impact of the fungicide tebuconazole on an aquatic decomposer‐detritivore system

Zubrod

Bundschuh

Feckler

et al. 2011

Enviro Toxic and Chemistry

103

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Leaf litter breakdown is a fundamental process in aquatic ecosystems that is realized by microbial decomposers and invertebrate detritivores. Although this process may be adversely affected by fungicides, among other factors, no test design exists to assess combined effects on such decomposer-detritivore systems. Hence, the present study assessed effects of the model fungicide tebuconazole (65 µg/L) on the conditioning of leaf material (by characterizing the associated microbial community) as well as the combined effects (i.e., direct toxicity and food quality-related effects (=indirect)) on the energy processing of the leaf-shredding amphipod Gammarus fossarum using a five-week semistatic test design. Gammarids exposed to tebuconazole produced significantly less feces (≈ 20%), which in turn significantly increased their assimilation (≈ 30%). Moreover, a significantly reduced lipid content (≈ 20%) indicated lower physiological fitness. The conditioning process was altered as well, which was indicated by a significantly reduced fungal biomass (≈ 40%) and sporulation (≈ 30%) associated with the leaf material. These results suggest that tebuconazole affects both components of the investigated decomposer-detritivore system. However, adverse effects on the level of detritivores cannot be explicitly attributed to direct or indirect pathways. Nevertheless, as the endpoints assessed are directly related to leaf litter breakdown and associated energy transfer processes, the protectiveness of environmental risk assessment for this ecosystem function may be more realistically assessed in future studies by using this or comparable test designs.

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“…We could not use Skellam's competition model (1951) which assumes that competitors cannot coexist in the same patch. Such local exclusion is not true for unit-restricted fungi, which coexist inside each unit, such as a leaf (Shearer & Lane, 1983) or a coniferous needle (Kendrick & Burges, 1962), and form ''unit-communities'' (Swift, 1984). However, competition occurs inside units and decreases the spore production of both species (Zak & Rabatin, 1997;Newton et al, 1998) according to a pure propagule production competition model (Klausmeier, 2001).…”

Section: Introductionmentioning

confidence: 98%