Ian J Alexander

University of Aberdeen, Aberdeen, Scotland, United Kingdom

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Publications (67)301.08 Total impact

  • Ian C Anderson, David R Genney, Ian J Alexander
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    ABSTRACT: Ectomycorrhizal (ECM) mycelium is a key component of the ectomycorrhizal symbiosis, yet we know little regarding the fine-scale diversity and distribution of mycelium in ECM fungal communities. We collected four 20 × 20 × 2-cm(3) (800-cm(3) ) slices of Scots pine (Pinus sylvestris) forest soil and divided each into 100 2 × 2 × 2-cm(3) (8-cm(3) ) cubes. The presence of mycelium of ECM fungi was determined using an internal transcribed spacer (ITS) database terminal restriction fragment length polymorphism (T-RFLP) approach. As expected, many more ECM fungi were detected as mycelium than as ectomycorrhizas in a cube or slice. More surprisingly, up to one-quarter of the 43 species previously detected as ectomycorrhizas over an area of 400 m(2) could be detected in a single 8-cm(3) cube, and up to three-quarters in a single 800-cm(3) slice. ECM mycelium frequency decreased markedly with depth and there were distinct 'hotspots' of mycelium in the moss/F1 layer. Our data demonstrate a high diversity of ECM mycelium in a small (8-cm(3) ) volume of substrate, and indicate that the spatial scale at which ECM species are distributed as mycelium may be very different from the spatial scale at which they are distributed as tips.
    New Phytologist 12/2013; · 6.74 Impact Factor
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    Angela Hodge, Ian J. Alexander, Graham W. Gooday
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    ABSTRACT: Four ectomycorrhizal basidiomycetes (Boletinus cavipes, Paxillus involutus, Suillus variegatus and Pisolithus tinctorius), two pathogenic root-infecting basidiomycetes (Heterobasidion annosum and Armillaria ostoyae) and the oomycete Phytophthora cinnamomi were screened for chitinolytic activity in liquid culture. N-Acetylglucosaminidase, exo- and endo-chitinase activity were distinguished using fluorogenic 4-methylumbelliferyl substrates. N-Acetylglucosaminidase was the predominant enzyme activity recorded: exochitinase was the predominant chitinase. The pathogenic basidiomycetes had higher specific activities against all substrates than the ectomycorrhizal fungi. There was considerable variation in activity between the ectomycorrhizal isolates. P. cinnamomi showed N-acetylglucosaminidase activity only. In general, chitinolytic activities were highest when chitin was present in the growth medium and were repressed in the presence of glucose. Diammonium phosphate did not repress chitinolytic activities.
    Mycological Research 06/2013; 99(8):935-941. · 2.81 Impact Factor
  • S Jarvis, S Woodward, I J Alexander, A F S Taylor
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    ABSTRACT: Ectomycorrhizal fungi commonly associate with the roots of forest trees where they enhance nutrient and water uptake, promote seedling establishment and have an important role in forest nutrient cycling. Predicting the response of ectomycorrhizal fungi to environmental change is an important step to maintaining forest productivity in the future. These predictions are currently limited by an incomplete understanding of the relative significance of environmental drivers in determining the community composition of ectomycorrhizal (ECM) fungi at large spatial scales. To identify patterns of community composition in ECM fungi along regional scale gradients of climate and nitrogen deposition in Scotland, fungal communities were analysed from 15 semi-natural Scots pine (Pinus sylvestris L.) forests. Fungal taxa were identified by sequencing of the ITS rDNA region using fungal-specific primers. Non-metric multidimensional scaling was used to assess the significance of 16 climatic, pollutant and edaphic variables on community composition. Vector fitting showed that there was a strong influence of rainfall and soil moisture on community composition at the species level, and a smaller impact of temperature on the abundance of ectomycorrhizal exploration types. Nitrogen deposition was also found to be important in determining community composition, but only when the forest experiencing the highest deposition (9.8 kg N ha(-1) yr(-1) ) was included in the analysis. This finding supports previously published critical load estimates for ectomycorrhizal fungi of 5-10 kg N ha(-1) yr(-1) . This work demonstrates that both climate and nitrogen deposition can drive gradients of fungal community composition at a regional scale. © 2013 Blackwell Publishing Ltd.
    Global Change Biology 02/2013; · 6.91 Impact Factor
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    ABSTRACT: Fungi are a vital component of ecosystem biodiversity, but spend most of their lives hidden from view. Monitoring ectomycorrhizal (ECM) fungi has mostly relied on the abundance and distribution of above-ground sporocarps without consideration of their below-ground vegetative mycelium. Molecular methods may provide the means of obtaining this information and allow a more accurate determination of their possible decline and threat of extinction. Stipitate hydnoid sporocarp occurrence was recorded and mapped for 9 yr at two sites in Scotland, UK. Soil samples were collected at locations where sporocarps of Hydnellum aurantiacum, Hydnellum caeruleum, Phellodon niger or Sarcodon glaucopus had occurred 1–4 yr previously. Species-specific DNA was detected at all sporocarp locations and RNA was detected at 75 % of the locations indicating that these species remained below-ground and viable at the majority of locations for at least 4 yr in the absence of sporocarps.
    Fungal Ecology 10/2012; 5(5):633–640. · 2.85 Impact Factor
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    Anna Wilkinson, Ian Alexander, David Johnson
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    ABSTRACT: Ectomycorrhizal (EM) fungal communities are taxonomically diverse, and independent manipulation of both intra- and interspecific diversity has previously been shown to positively influence the productivity and activity of EM fungi. Here, we combine manipulations of intra- and interspecific richness and test the effects of a genotype-species gradient on the biomass production and respiration of EM fungi in vitro. Genotype identity had the most pronounced effect on fungal productivity, and in some cases variation within species was greater than between species. We found small negative effects of both species and genotype richness on biomass production, CO2 efflux and the final nitrogen (N) content of the fungal communities corresponding to mixed negative selection and complementarity effects. Our study highlights the degree of variability between individual EM fungi at the genotype level, and consequently emphasises the importance of individual genotypes for playing key roles in shaping belowground community functioning.
    Fungal Ecology 10/2012; 5(5):571–580. · 2.85 Impact Factor
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    ABSTRACT: Microbial ecology has made large advances over the last decade, mostly because of improvements in molecular analysis techniques that have enabled the detection and identification of progressively larger numbers of microbial species. However, determining the ecological patterns and processes taking place in communities of microbes remains a significant challenge. Are communities randomly assembled through dispersal and priority effects, or do species interact with each other leading to positive and negative associations? For mycorrhizal fungi, evidence is accumulating that stochastic and competitive interactions between species may both have a role in shaping community structure. Could the methodological approach, which is often incidence based, impact the outcomes detected? Here, we applied an incidence-based Terminal Restriction Fragment Length Polymorphism (T-RFLP) database approach to examine species diversity and ecological interactions within a community of ectomycorrhizal (ECM) fungi. Co-occurrence analysis revealed that the ECM community colonizing root tips was strongly structured by competitive interactions, or ecological processes generating a similar spatial pattern, rather than neutral processes. Analysis of β-diversity indicated that community structure was significantly more similar (spatially autocorrelated) at distances equal to or <3.41 m. The eight most frequently encountered species in the root tip community of ECM fungi displayed significant competitive interactions with at least one other species, showing that the incidence-based approach was capable of detecting this sort of ecological information.
    Molecular Ecology 09/2012; 21(20):5110-23. · 6.28 Impact Factor
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    ABSTRACT: The effects of biodiversity of aboveground organisms have been widely investigated in a range of ecosystems, yet whether similar responses are also seen in belowground microbial communities, such as ectomycorrhizal (EM) fungi, are little understood. We investigated, in vitro, the effects of a gradient of 1–8 species of EM fungi interacting with substratum carbon:nitrogen (C:N) ratio on biomass production and CO2 efflux. The model experimental systems enabled us to recover and measure biomass of individuals within communities and calculate net selection and complementarity effects. Both biomass and CO2 efflux increased with species richness particularly under high N concentrations. Moreover, net biodiversity effects were largely positive, driven by both selection and complementarity effects. Our results reveal, in pure culture, the implications of EM species richness on community productivity and C cycling, particularly under high N conditions, and constitute the basis for future experiments under natural conditions.
    Fungal Ecology - FUNGAL ECOL. 04/2012;
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    ABSTRACT: Contamination of irrigation water represents a major constraint to Bangladesh agriculture, resulting in elevated levels in the terrestrial systems. Lux bacterial biosensor technology has previously been used to measure the toxicity of metals in various environmental matrices. While arbuscular mycorrhizal fungi have their most significant effect on phosphorus uptake, but showed alleviated metal toxicity to the host plant. The study examined the effects of arsenic and inoculation with an arbuscular mycorrhizal fungus, Glomus mosseae, on lentil (Lens culinaris L. cv. Titore). Plants were grown with and without arbuscular mycorrhizal inoculum for 9 weeks in a sand and terra-green mixture (50:50, V/V) and watered with five levels of arsenic (0, 1, 2, 5, 10 mg As/L arsenate). The results showed that arsenic addition above 1 mg/L significantly reduced percentage of mycorrhizal root infection. On further analysis a close relationship was established with the vegetative and reproductive properties of lentil (L. culinaris) plants compared to the percentage bioluminescence of the soil leachate. However, arbuscular mycorrhizal fungal inoculation reduced arsenic concentration in roots and shoots. Higher concentrations of arsenic (5, 10 mg As/L arsenate) reduced the mycorrhizal efficiency to increase phosphorus content and nitrogen fixation. Therefore, this study showed that increased concentration of arsenic in irrigation water had direct implications to the lentil (L. culinaris) plants overall performance. Moreover the use of bioassay demonstrated that mycorrhiza and clay particle reduced arsenic bioavailability in soil.
    Journal of Environmental Sciences 01/2012; 24(6):1106-16. · 1.77 Impact Factor
  • Ian J Alexander, Holly Slater
    New Phytologist 08/2011; · 6.74 Impact Factor
  • Eneke Esoeyang Tambe Bechem, Ian James Alexander
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    ABSTRACT: A field survey was carried out to investigate the diversity of mycorrhizal fungi associated with Gnetum spp. in Cameroon. The extent and variation of ectomycorrhizal colonisation as well as the degree of host specificity were evaluated. Gnetum spp. were found to be almost always ectomycorrhizal in all sites visited. There were just two ectomycorrhizal morphotypes ('yellow' and 'white') associated with this plant. Such low diversity is unusual for an ectomycorrhizal plant. The yellow morphotype was the most widespread and prevalent and was identified by morphological and molecular methods to have been formed with Scleroderma sinnamariense. Propagules of this fungus were present in soil collected from farm lands, cocoa plantations, Chromolaena and bush fallows, as well as in a relatively undisturbed forest harbouring ectomycorrhizal legumes. The fungus responsible for the white morphotype was identified as also belonging to the genus Scleroderma by ITS sequence similarity. Arbuscular mycorrhizal structures were absent in cleared and stained portions of the roots.
    Mycorrhiza 04/2011; 22(2):99-108. · 2.96 Impact Factor
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    ABSTRACT: Arsenic (As)-contaminated irrigation water is responsible for high As levels in soils and crops in many parts of the world, particularly in the Bengal Delta, Bangladesh and West Bengal, India. While arbuscular mycorrhizal (AM) fungi markedly improve phosphorus (P) uptake, they can also alleviate metal toxicity. In this study, the effects of superphosphate and inoculation with the AM fungus Glomus mosseae on P and As uptake of lentil were investigated. Plant height, shoot dry weight, shoot/root P concentration, and shoot P content increased due to mycorrhizal inoculation. However, As concentration in roots/shoots and root As content were reduced, plant height, shoot dry weight, shoot/root P concentration/content, and root As concentration and content increased due to superphosphate application. Root P concentration decreased with increasing As concentration. It was apparent that As concentration and content in shoots/roots increased with increasing As concentration in irrigation water. Superphosphate interaction with G. mosseae reduced the role of mycorrhizal infection in terms of enhancing P nutrition and reducing uptake of potentially toxic As into plant parts. The role and relationship of mycorrhizal in respect of P nutrition and As remediation efficiency in plant parts was established. In conclusion, it was worth alluding to that lentil with AM fungal inoculation can reduce As uptake and improve P nutrition. However, in retrospect superphosphate increased P and As uptake and decreased the role of the mycorrhizal association. This resulted in stimulating increased P uptake while decreasing As uptake in lentil. KeywordsArbuscular mycorrhizas–Arsenate–Arsenic– Glomus mosseae –Lentil–Phosphorus uptake–Superphosphate
    Water Air and Soil Pollution 01/2011; 221(1):169-182. · 1.75 Impact Factor
  • Anna Wilkinson, Ian J. Alexander, David Johnson
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    ABSTRACT: The ectomycorrhizal mycelium is a large component of boreal and temperate forest soil microbial biomass and the resulting necromass is likely to be an important source of nutrients for saprotrophic microorganisms. Here we test the effects of species richness of ectomycorrhizal mycelial biomass on short-term CO2 efflux by amending forest soil with necromass from 8 fungal species added separately and in mixtures of 2, 4 and 8 species. All additions of necromass rapidly increased soil CO2 efflux compared to unamended controls but CO2 efflux increased significantly with species richness. Efflux of CO2 did not correlate with the carbon (C) or nitrogen (N) contents or the C:N ratio of the added necromass. The study demonstrates that species diversity of dead ectomycorrhizal fungal hyphae can have important consequences for soil CO2 efflux, and suggests decomposition of hyphae is regulated by specific constituents of the nutrient pools in the necromass rather than the total quantities added.
    Soil Biology & Biochemistry - SOIL BIOL BIOCHEM. 01/2011; 43(6):1350-1355.
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    ABSTRACT: • Fungi in the Rhizoscyphus ericae aggregate have been recovered from the roots of co-occurring ericaceous shrubs and ectomycorrhizal trees. However, to date, there is no evidence that the same individual genotypes colonize both hosts, and no information on the extent of the mycelial networks that might form. • Using spatially explicit core sampling, we isolated fungi from neighbouring Pinus sylvestris (ectomycorrhizal) and Vaccinium vitis-idaea (ericoid mycorrhizal) roots and applied intersimple sequence repeat (ISSR) typing to assess the occurrence and extent of shared genets. • Most isolates were identified as Meliniomyces variabilis, and isolates with identical ISSR profiles were obtained from neighbouring ericoid and ectomycorrhizal roots on a number of occasions. However, genet sizes were small (< 13  cm), and several genets were found in a single soil core. Genetic relatedness was independent of spatial separation at the scales investigated (< 43  m) and M. variabilis populations from sites 20  km apart were genetically indistinguishable. • We conclude that individual genets of M. variabilis can simultaneously colonize Scots pine and Vaccinium roots, but there is no evidence for the formation of large mycelial networks. Our data also suggest significant genotypic overlap between widely separated populations of this ubiquitous root-associated fungus.
    New Phytologist 10/2010; 188(1):210-22. · 6.74 Impact Factor
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    New Phytologist 04/2010; 186(2):281-5. · 6.74 Impact Factor
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    ABSTRACT: Spatial analysis was used to explore the distribution of individual species in an ectomycorrhizal (ECM) fungal community to address: whether mycorrhizas of individual ECM fungal species were patchily distributed, and at what scale; and what the causes of this patchiness might be. Ectomycorrhizas were extracted from spatially explicit samples of the surface organic horizons of a pine plantation. The number of mycorrhizas of each ECM fungal species was recorded using morphotyping combined with internal transcribed spacer (ITS) sequencing. Semivariograms, kriging and cluster analyses were used to determine both the extent and scale of spatial autocorrelation in species abundances, potential interactions between species, and change over time. The mycorrhizas of some, but not all, ECM fungal species were patchily distributed and the size of patches differed between species. The relative abundance of individual ECM fungal species and the position of patches of ectomycorrhizas changed between years. Spatial and temporal analysis revealed a dynamic ECM fungal community with many interspecific interactions taking place, despite the homogeneity of the host community. The spatial pattern of mycorrhizas was influenced by the underlying distribution of fine roots, but local root density was in turn influenced by the presence of specific fungal species.
    New Phytologist 02/2010; 186(3):755-68. · 6.74 Impact Factor
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    ABSTRACT: The plant intermediate wintergreen (Pyrola media, Ericaceae) is in need of conservation action in Scotland. Although widespread, it is locally distributed in dwarf shrub heath and more commonly in Scots pine (Pinus sylvestris) woodlands. A recent study on the mycorrhizal status of Pyrola suggested that they associate with a restricted range of ectomycorrhizal (ECM) fungi. Here, we examined the hypothesis that specialisation by P. media for fungi usually associated with Scots pine is a factor in promoting its occurrence in this habitat. The fungal community associated with the roots of P. media growing in a Scots pine forest was determined by morphotyping, polymerase chain reaction, cloning and sequencing. Molecular identification found 49 taxa representing ecto- and ericoid mycorrhizal fungi, dark septate endophytes, saprotrophs, and fungi of unknown trophic status. The majority of the taxa (67.4%) were Basidiomycota, with 24.4% known to be ECM fungi specific to Pinus sp. or conifers. However, a wide range of other mycorrhizal fungi with varying degrees of host specificity were also found, including taxa usually associated with deciduous hosts. In conclusion, the broad range of mycorrhizal fungi recovered from the roots of P. media suggests that specialization is not a major factor in determining its distribution. KeywordsConservation-Ericaceae-Fungal community-ITS-Mixotrophy-Mycorrhiza-Native woodland- Pinus sylvestris - Pyrola media
    Biodiversity and Conservation 01/2010; 19(14):3963-3971. · 2.26 Impact Factor
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    ABSTRACT: Individuals and not just species are key components of biodiversity, yet the relationship between intraspecific diversity and ecosystem functioning in microbial systems remains largely untested. This limits our ability to understand and predict the effects of altered genetic diversity in regulating key ecosystem processes and functions. Here, we use a model fungal system to test the hypothesis that intraspecific genotypic richness of Paxillus obscurosporus stimulates biomass and CO(2) efflux, but that this is dependent on nitrogen supply. Using controlled experimental microcosms, we show that populations containing several genotypes (maximum 8) of the fungus had greater productivity and produced significantly more CO(2) than those with fewer genotypes. Moreover, intraspecific diversity had a much stronger effect than a four-fold manipulation of the carbon:nitrogen ratio of the growth medium. The effects of intraspecific diversity were underpinned by strong roles of individuals, but overall intraspecific diversity increased the propensity of populations to over-yield, indicating that both complementarity and selection effects can operate within species. Our data demonstrate the importance of intraspecific diversity over a range of nitrogen concentrations, and the need to consider fine scale phylogenetic information of microbial communities in understanding their contribution to ecosystem processes.
    PLoS ONE 01/2010; 5(9):e12604. · 3.73 Impact Factor
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    ABSTRACT: New native pine forests provide potential new habitat for colonisation by stipitate hydnoid fungi but their ability to colonise and persist in these areas is unknown. Soil containing Scots pine seedlings and inoculum of Hydnellum peckii was transferred to Darroch Wids, which is a newly planted native forest on former agricultural land. Both H. peckii and Phellodon tomentosus were transferred to White Bridge, which once would have supported native Scots pine forest. Below-ground persistence of the inoculum was monitored by amplification of ITS sequences from soil DNA and RNA using species-specific primers, and root systems were screened for the presence of ectomycorrhizas of both target species. H. peckii DNA was consistently detected over 2.5 y in soil taken from the Darroch Wids site. The number of detections of H. peckii and P. tomentosus DNA at White Bridge showed a sharp decline over 1 y. RNA of the target species was detected in the majority of samples, however, no ectomycorrhizas were found at White Bridge. This suggests that establishment of new colonies of H. peckii and P. tomentosus is unpredictable.
    Fungal Ecology. 01/2010;
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    ABSTRACT: Interest in stipitate hydnoid fungi of the genera Bankera, Hydnellum, Phellodon and Sarcodon has increased due to the decline in numbers of sporocarps in Europe. Conservation of these fungi is hindered by a lack of understanding of their basic ecology. In particular, a better understanding of their belowground ecology is required. Real-time PCR in conjunction with spatially explicit sampling was used to quantify the relationship between sporocarps and mycelium of Hydnellum peckii and Phellodon tomentosus. Species-specific DNA of the target species was quantified in 100 soil samples collected on a 360 x 360 cm grid at five locations where sporocarps were present. All sporocarps within the grid and up to 2 m around the grid were mapped. Sporocarp production did not occur over the whole extent of the belowground mycelium of these two species, and mycelium extended up to 330 cm away from the immediate site of sporocarp production. Spatial analyses using Kernel-smoothing and Moran's I correlograms showed that, with a single exception, there was no quantitative relationship between sporocarp distribution and the belowground abundance of mycelium. These findings have important implications for the conservation of this rare group of fungi.
    FEMS Microbiology Ecology 07/2009; 69(3):344-52. · 3.56 Impact Factor
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    ABSTRACT: Spatial analysis techniques have recently become more common in ecological research. The application of these techniques to ecological problems has coincided with the development of molecular techniques for the study of ectomycorrhizal (ECM) fungal communities. Through determination of the spatial properties of ECM fungal species’ distribution (i.e. patch size and shape, degree of clustering), it may be possible to derive much more information about these communities than can be obtained from simple species abundance and frequency data. For example, the use of spatial analysis may enable detection of species interactions and temporal changes in species distribution, as well as illustrating how environmental properties may relate to ECM fungal distribution. This review discusses the application of spatial ecology concepts to, and the issues surrounding, spatially explicit sampling of ECM fungal communities in relation to current trends in ECM community research, and suggests directions for future research.
    06/2009: pages 155-165;

Publication Stats

1k Citations
301.08 Total Impact Points

Institutions

  • 1995–2013
    • University of Aberdeen
      • • Institute of Biological and Environmental Sciences
      • • School of Biological Sciences
      Aberdeen, Scotland, United Kingdom
  • 2012
    • James Hutton Institute
      Aberdeen, Scotland, United Kingdom
  • 2011
    • University of Buea
      • Department of Plant and Animal Science
      Buea, South-West Region, Cameroon
    • Lancaster University
      Lancaster, England, United Kingdom
  • 2009
    • Universität Basel
      Bâle, Basel-City, Switzerland
  • 2007
    • University of Western Sydney
      • Hawkesbury Institute for the Environment
      Penrith, New South Wales, Australia
    • University of Queensland
      Brisbane, Queensland, Australia
  • 2005–2007
    • Swedish University of Agricultural Sciences
      • Department of Forest Mycology and Plant Pathology
      Uppsala, Uppsala, Sweden
  • 2001
    • Centre for Ecology & Hydrology
      Wallingford, England, United Kingdom