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Use an analytical method called CLADISTICS to work out the Evolutionary pattern of agroup of organisms.
Cladistics is amethod of phylogenetic systematics which aims to determine an organism'sclassification, by decent, in a taxonomic system. Cladistics usessynapomorphies, which are shared derived characteristics, between groups oforganisms to make decisions about how the group fits into the classificationsystem. For this cladistic study the group of organisms known as ectomycorrhizaefungi has been selected.
Ectomychorrhizal(EM) fungi plays a key role in the growth and development of vascular plants (Allen,1991; Kendrick, 1992). Much work has been done on classification of the typesof associations between the fungi and the host plants (Brundrett, 2004) butmuch work remains on differentiation of the organisms beyond this level ofclassification (Wilkinson, 2001). Ectomycorrhizae form symbiotic relationshipswith woody plants and mychorrhizae abundance and diversity have been shown tohave effects on plant growth and survival (Hart and Klironomos, 2002).
Recently work has been done on identifying the evolutionary history of ectomycorrhizae common in basidiomycetes using DNA samples of 46 species which yielded 10,000 equally parsimonious trees (Hibbett et al, 2000). A key problem with construction of evolutionary histories of ectomycorrhizae is that most is DNA based rather than morphological or behavioural (Bruns and Shefferson, 2004). This data is needed to confirm that the DNA-based cladograms are correct.
The study willfocus on ectomycorrhizal associations with woody plants as these are easy to sampleand readily available. Field work will be undertaken in the summer of 2007when the ground is soft enough for soil samples. The purpose of the study isto be able to identify EM fungi using non-sexual state morphologicalcharacteristics which is a cheaper technique than doing a DNA analysis. Identifyingwhich species associate with which woody plants may be helpful in preparingsites for reforestation and could influence how forest sites are prepared forreplanting.
Aims &Objectives
The aim of thestudy is to further develop the classification system of ectomychorrhizae fungiand to complement other studies done in the field. The focus is to confimthat current techniques to construct ectomycorrhizal cladograms using DNA arein agreement with ectomycorrhizal cladograms based on morphological andbehavioural characteristics. If there is disagreement between the methods thaneither more development must be done on distinguishing physical characteristicsor the DNA identification methods must be reconsidered.
Context/literaturereview/background
Much work hasbeen done on identifying EM communities but most of this has been done oneither sexual states (early literature) or rDNA internal transcribed spacer (ITS)comparison (Horton and Bruns, 2002). Since early work concentrated on fruitingand spore forms of EM, this covered very little of the total EM which occurredmostly below ground (Horton, 2002).
However, advances in molecular technology have given mycologists a new way to determine species diversity and taxonomy of these morphologically difficult to determine EM. Work is being rapidly done on identifying EM using rDNA sequences and building databases for public use (Kõljalg et al, 2005).
Major papersreviewed include:
Wilkinson, D.M. (2001). Mycorrhizal evolution. Trends in Ecology & Evolution
Vol 16(2),p.64-65.
Bruns, T.D. andShefferson, R. P. (2004). Evolutionary studies of ectomycorrhizal fungi: recentadvances and future directions. Canadian Journal of Botany. Vol.82 (8)p. 1122 - 1133.
Horton, T.R.and Bruns, T.D. (2002). The molecular revolution in ectomycorrhizal ecology:peeking into the black-box. Molecular Ecology 10, p. 1855-1871
Horton, T.R.(2002). Molecular approaches to ectomycorrhizal diversity studies: variationin ITS at a local scale. Plant and Soil 244: 29-39.
Taylor AFS.(2002). Fungal diversity in ectomycorrhizal communities: sampling effort andspecies detection. Plant and Soil 244: 19-28.
Methodology
Samples will be taken of root material of 4 different types of treesthat are commercially important and readily available. To get a wide samplingof EM 2 softwoods and 2 hardwoods were chosen. It would have been possible tosample simply 1 species repeatedly but a wider range of samples is desirable tobuild more detailed cladograms. Samples will be taken in spring, mid-summerand fall to try and obtain samples of different morphs of the EM. Abiesbalsamea, Pinus resinosa and Picea rubens were the chosensoftwoods for their relative abundance and ease of identification in thefield. Fraxinus excelsior, Populus tremuloides and Betulapapyrifera were the hardwoods chosen for the same reasons.
Root samples will be collected from a tree of each species growingin close proximity. This will lead to duplicate species samples but will givean overall picture of the species diversity of the area. Typically some EMspecies will be dominant but some other species should be present. The sampleswill then be stored in cool temperatures to slow sample degradation whileawaiting analysis.
Samples will then be analyzed by locating EM, taking a cutting andsending it to a professional molecular lab for rDNA analysis of the ITS region.The same sample will then be fully morphologically characterized. Using the UNITEdatabase (Kõljalg, U et al, 2005) identification of the species based onmolecular characteristics will be made. This will be compared to themorphological-based cladistic identification to check if the morphologicalclassification system is valid.
Outline of datacollected
None to date.
Furtheranalysis
Further analysis depends on results from the comparison of themorphological based cladogram and the molecular analysis. If the two matchthen work can be continued to included more sample sites and more species couldbe identified. If the comparison is not a match, and this is the expectedresult from the trial, then a resampling should take place and more work shouldbe done on developing a classification system.
References
Allen, M. F. (1991).The Ecology of Mycorrhizae.
CopyrightCambridge University Press 1991.
Brundrett, M.(2004). Diversity and classification of mycorrhizal associations. BiologicalReviews 79: 473-495. Cambridge University Press. Copyright 2004Cambridge Philosophical Society.
Dominik T. (1959). Synopsis of a newclassification of the ectotrophic mycorrhizae established on morphological andanatomical characteristics.
Mycopathologia. Vol. 11:359-67.
Hibbett, D.S.,Gilbert, L and Donoghue, M.J. (2000). Evolutionary instability ofectomycorrhizal symbioses in basidiomycetes. Nature 407 p:506 - 508.
Kendrick B.1992. The Fifth Kingdom. Mycologue Publications, Waterloo
Kõljalg, U.,Larsson, K-H., Abarenkov, K., Nilsson, R.H., Alexander, I.J., Eberhardt, U.,Erland, S., Høiland, K., Kjøller, R., Larsson, E., Pennanen, T., Sen, R.,Taylor, A.F.S, Tedersoo, L. Vrålstad, T., Ursing, B.M. (2005). UNITE: a database providing web-basedmethods for the molecular identification of ectomycorrhizal fungi. New Phytologist. Vol166(3) p.1063
Hart and Klironomos,2002 M. Hart and J. Klironomos, Diversity of arbuscular mycorrhizal fungi andecosystem functioning. In: M. van der Heijden and I. Sanders, Editors, MycorrhizalEcology. Ecological Studies vol. 157, pp. 225-239.
van derHeijden, 2002 M. van der Heijden, Arbuscular mycorrhizal fungi as a determinantof plant diversity: in search for underlying mechanisms and general principals.In: M. van der Heijden and I. Sanders, Editors, Mycorrhizal Ecology.Ecological Studies vol. 157, pp. 243-261.
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