Article

Significant diversity and potential problems associated with inferring population structure within the Cenococcum geophilum species complex

Department of Plant Pathology and Microbiology, University of California, Riverside, California 92521, USA.
Mycologia (Impact Factor: 2.13). 11/2007; 99(6):812-9. DOI: 10.3852/mycologia.99.6.812
Source: PubMed

ABSTRACT Cenococcum geophilum is perhaps the most widely distributed and most recognized ectomycorrhizal fungus with a host range of more than 200 tree species from 40 genera of both angiosperms and gymnosperms. We conducted a phylogenetic analysis on a large collection of isolates (n=74) from North America and Europe based on glyceraldehyde 3-phosphate dehydrogenase (gpd). A subset of isolates (n=22) also was analyzed with the more conservative LSU-rDNA locus. Significant nucleotide diversity was detected (approximately 20%) in the gpd region and the LSU-rDNA analysis supported that the C. geophilum isolates studied were monophyletic but distinct from two isolates, Am5-1 and N2-10, which previously were used in population genetic studies of this species. These results suggest that Am5-1 and N2-10 are likely two undescribed species or even genera. Our results suggest that C. geophilum sensu lato is a species complex and support previous molecular, physiological and morphological studies that have shown significant diversity in C. geophilum. This study also revealed that caution is advised when conducting population genetic studies in C. geophilum due to the possibility of pooling unrelated isolates. This potential problem also has implications for other fungal taxa because cryptic species routinely have been found in recent years based on molecular data.

0 Followers
 · 
47 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Despite the ubiquity and importance of ectomycorrhizal fungi to ecosystem function, our understanding of their functional ecology remains poor. The highly melanized and common ectomycorrhizal fungus, Cenococcum geophilum, is drought tolerant and abundant inwater-stressed habitats, yet the responsible functional traits have not been identified. The production of melanin, a class of complex dark polymers found in fungal cell walls, may be a key functional trait to water stress tolerance. To test this hypothesis, we devised a series of experiments determining the effect of the melanin biosynthesis inhibitor, tricyclazole, on response to osmotic and desiccation stresses. Melanin inhibition only had negative effects on growth when C. geophilum isolates were subjected to osmotic and desiccation stress (-1.7 MPa and desiccated) but not under control conditions (-0.01 MPa and nondesiccated).This suggests that melanin production is an important functional trait that contributes to water stress tolerance of this cosmopolitan ectomycorrhizal fungus.
    Fungal Ecology 12/2013; 6(6):479-486. DOI:10.1016/j.funeco.2013.08.004 · 2.99 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The ectomycorrhizal fungus Cenococcum geophilum (Ascomycota, Dothideomycetes) forms black, round to irregular sclerotia in forest soils. Fungi that colonize the sclerotia appear to affect sclerotia viability and may play an important role in the life history of Cenococcum. Some of the fungi could also affect nutrient cycling by decomposing Cenococcum sclerotia, which are melanized and recalcitrant to decay. We used a culture-based method to document the fungal communities growing inside surface-sterilized sclerotia that were collected from forest soils. Cenococcum was successfully isolated from 297 out of 971 sclerotia whereas 427 sclerotia hosted fungi other than Cenococcum. DNA barcoding of the ITS rDNA followed by grouping at 97% sequence similarity yielded 85 operational taxonomic units (OTUs) that consisted primarily of Ascomycota (e.g. Chaetothyriales, Eurotiales, Helotiales, Pleosporales) and a few Basidiomycota and Mucoromycotina. Although most fungal OTUs were infrequently cultured, several OTUs such as members of Asterostroma, Cladophialophora, Oidiodendron and Pleosporales were common and found across many sites. Our results suggest that Cenococcum sclerotia act as a substrate for diverse fungi. The occurrence of several OTUs in sclerotia across many sites suggests that these fungi may be active parasites of Cenococcum sclerotia or may preferencially use sclerotia as a nutrient source.This article is protected by copyright. All rights reserved.
    FEMS Microbiology Ecology 09/2014; 90(3). DOI:10.1111/1574-6941.12428 · 3.88 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The diversity of fungi along environmental gradients has been little explored in contrast to plants and animals. Consequently, environmental factors influencing the composition of fungal assemblages are poorly understood. The aim of this study was to determine whether the diversity and composition of leaf and root-associated fungal assemblages vary with elevation and to investigate potential explanatory variables. High-throughput sequencing of the Internal Transcribed Spacer 1 region was used to explore fungal assemblages along three elevation gradients, located in French mountainous regions. Beech forest was selected as a study system to minimise the host effect. The variation in species richness and specific composition was investigated for ascomycetes and basidiomycetes assemblages with a particular focus on root-associated ectomycorrhizal fungi. The richness of fungal communities associated with leaves or roots did not significantly relate to any of the tested environmental drivers, i.e. elevation, mean temperature, precipitation or edaphic variables such as soil pH or the ratio carbon∶nitrogen. Nevertheless, the ascomycete species richness peaked at mid-temperature, illustrating a mid-domain effect model. We found that leaf and root-associated fungal assemblages did not follow similar patterns of composition with elevation. While the composition of the leaf-associated fungal assemblage correlated primarily with the mean annual temperature, the composition of root-associated fungal assemblage was explained equally by soil pH and by temperature. The ectomycorrhizal composition was also related to these variables. Our results therefore suggest that above and below-ground fungal assemblages are not controlled by the same main environmental variables. This may be due to the larger amplitude of climatic variables in the tree foliage compared to the soil environment.
    PLoS ONE 06/2014; 9(6):e100668. DOI:10.1371/journal.pone.0100668 · 3.53 Impact Factor

Full-text (2 Sources)

Download
18 Downloads
Available from
May 22, 2014