| 1. |
- Abarenkov, Kessy, et al.
(author)
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PlutoF—a web based workbench for ecological and taxonomic research, with an online implementation for fungal ITS sequences
- 2010
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In: Evolutionary Bioinformatics. - 1176-9343. ; 6, s. 189-196
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Journal article (peer-reviewed)abstract
- DNA sequences accumulating in the International Nucleotide Sequence Databases (INSD) form a rich source of information for taxonomic and ecological meta-analyses. However, these databases include many erroneous entries, and the data itself is poorly annotated with metadata, making it difficult to target and extract entries of interest with any degree of precision. Here we describe the web-based workbench PlutoF, which is designed to bridge the gap between the needs of contemporary research in biology and the existing software resources and databases. Built on a relational database, PlutoF allows remote-access rapid submission, retrieval, and analysis of study, specimen, and sequence data in INSD as well as for private datasets though web-based thin clients. In contrast to INSD, PlutoF supports internationally standardized terminology to allow very specific annotation and linking of interacting specimens and species. The sequence analysis module is optimized for identification and analysis of environmental ITS sequences of fungi, but it can be modified to operate on any genetic marker and group of organisms. The workbench is available at http://plutof.ut.ee.
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| 2. |
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| 3. |
- Bahram, Mohammad, et al.
(author)
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The distance decay of similarity in communities of ectomycorrhizal fungi in different ecosystems and scales
- 2013
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In: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745. ; 101:5, s. 1335-1344
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Journal article (peer-reviewed)abstract
- Despite recent advances in understanding community ecology of ectomycorrhizal fungi, little is known about their spatial patterning and the underlying mechanisms driving these patterns across different ecosystems. * This meta-study aimed to elucidate the scale, rate and causes of spatial structure of ectomycorrhizal fungal communities in different ecosystems by analysing 16 and 55 sites at the local and global scales, respectively. We examined the distance decay of similarity relationship in species- and phylogenetic lineage-based communities in relation to sampling and environmental variables. * Tropical ectomycorrhizal fungal communities exhibited stronger distance-decay patterns compared to non-tropical communities. Distance from the equator and sampling area were the main determinants of the extent of distance decay in fungal communities. The rate of distance decay was negatively related to host density at the local scale. At the global scale, lineage-level community similarity decayed faster with latitude than with longitude. * Synthesis. Spatial processes play a stronger role and over a greater scale in structuring local communities of ectomycorrhizal fungi than previously anticipated, particularly in ecosystems with greater vegetation age and closer to the equator. Greater rate of distance decay occurs in ecosystems with lower host density that may stem from increasing dispersal and establishment limitation. The relatively strong latitude effect on distance decay of lineage-level community similarity suggests that climate affects large-scale spatial processes and may cause phylogenetic clustering of ectomycorrhizal fungi at the global scale.
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| 4. |
- Kõljalg, Urmas, et al.
(author)
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Towards a unified paradigm for sequence-based identification of fungi.
- 2013
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In: Molecular ecology. - : Wiley. - 1365-294X .- 0962-1083. ; 22:21, s. 5271-7
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Journal article (peer-reviewed)abstract
- The nuclear ribosomal internal transcribed spacer (ITS) region is the formal fungal barcode and in most cases the marker of choice for the exploration of fungal diversity in environmental samples. Two problems are particularly acute in the pursuit of satisfactory taxonomic assignment of newly generated ITS sequences: (i) the lack of an inclusive, reliable public reference data set and (ii) the lack of means to refer to fungal species, for which no Latin name is available in a standardized stable way. Here, we report on progress in these regards through further development of the UNITE database (http://unite.ut.ee) for molecular identification of fungi. All fungal species represented by at least two ITS sequences in the international nucleotide sequence databases are now given a unique, stable name of the accession number type (e.g. Hymenoscyphus pseudoalbidus|GU586904|SH133781.05FU), and their taxonomic and ecological annotations were corrected as far as possible through a distributed, third-party annotation effort. We introduce the term 'species hypothesis' (SH) for the taxa discovered in clustering on different similarity thresholds (97-99%). An automatically or manually designated sequence is chosen to represent each such SH. These reference sequences are released (http://unite.ut.ee/repository.php) for use by the scientific community in, for example, local sequence similarity searches and in the QIIME pipeline. The system and the data will be updated automatically as the number of public fungal ITS sequences grows. We invite everybody in the position to improve the annotation or metadata associated with their particular fungal lineages of expertise to do so through the new Web-based sequence management system in UNITE.
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| 5. |
- Lindahl, Björn, et al.
(author)
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Fungal community analysis by high-throughput sequencing of amplified markers – a user's guide
- 2013
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In: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 199:1, s. 288-299
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Research review (peer-reviewed)abstract
- * Novel high-throughput sequencing methods outperform earlier approaches in terms of resolution and magnitude. They enable identification and relative quantification of community members and offer new insights into fungal community ecology. These methods are currently taking over as the primary tool to assess fungal communities of plant-associated endophytes, pathogens, and mycorrhizal symbionts, as well as free-living saprotrophs. * Taking advantage of the collective experience of six research groups, we here review the different stages involved in fungal community analysis, from field sampling via laboratory procedures to bioinformatics and data interpretation. We discuss potential pitfalls, alternatives, and solutions. * Highlighted topics are challenges involved in: obtaining representative DNA/RNA samples and replicates that encompass the targeted variation in community composition, selection of marker regions and primers, options for amplification and multiplexing, handling of sequencing errors, and taxonomic identification. * Without awareness of methodological biases, limitations of markers, and bioinformatics challenges, large-scale sequencing projects risk yielding artificial results and misleading conclusions.
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| 6. |
- Nilsson, R. Henrik, 1976, et al.
(author)
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A note on the incidence of reverse complementary fungal ITS sequences in the public sequence databases and a software tool for their detection and reorientation
- 2011
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In: Mycoscience. - : The Mycological Society of Japan. - 1340-3540 .- 1618-2545. ; 52:4, s. 278-282
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Journal article (peer-reviewed)abstract
- Reverse complementary DNA sequences––sequences that are inadvertently cast backward and in which all purines and pyrimidines are transposed––are not uncommon in sequence databases, where they may introduce noise into sequence-based research. We show that about 1% of the public fungal ITS sequences, the most commonly sequenced genetic marker in mycology, are reverse complementary, and we introduce an open source software solution to automate their detection and reorientation. The MacOSX/Linux/UNIX software operates on public or private datasets of any size, although some 50 base pairs of the 5.8S gene of the ITS region are needed for the analysis.
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| 7. |
- Nilsson, R. Henrik, 1976, et al.
(author)
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Five simple guidelines for establishing basic authenticity and reliability of newly generated fungal ITS sequences
- 2012
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In: MycoKeys. - : Pensoft Publishers. - 1314-4057 .- 1314-4049. ; 4, s. 37-63
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Journal article (peer-reviewed)abstract
- Molecular data form an important research tool in most branches of mycology. A non-trivial proportion of the public fungal DNA sequences are, however, compromised in terms of quality and reliability, contributing noise and bias to sequence-borne inferences such as phylogenetic analysis, diversity assessment, and barcoding. In this paper we discuss various aspects and pitfalls of sequence quality assessment. Based on our observations, we provide a set of guidelines to assist in manual quality management of newly generated, near-full-length (Sanger-derived) fungal ITS sequences and to some extent also sequences of shorter read lengths, other genes or markers, and groups of organisms. The guidelines are intentionally non-technical and do not require substantial bioinformatics skills or significant computational power. Despite their simple nature, we feel they would have caught the vast majority of the severely compromised ITS sequences in the public corpus. Our guidelines are nevertheless not infallible, and common sense and intuition remain important elements in the pursuit of compromised sequence data. The guidelines focus on basic sequence authenticity and reliability of the newly generated sequences, and the user may want to consider additional resources and steps to accomplish the best possible quality control. A discussion on the technical resources for further sequence quality management is therefore provided in the supplementary material.
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| 8. |
- Nilsson, R. Henrik, 1976, et al.
(author)
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Improving ITS sequence data for identification of plant pathogenic fungi
- 2014
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In: Fungal Diversity. - : Springer Science and Business Media LLC. - 1560-2745 .- 1878-9129. ; 67:1, s. 11-19
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Journal article (peer-reviewed)abstract
- Plant pathogenic fungi are a large and diverse assemblage of eukaryotes with substantial impacts on natural ecosystems and human endeavours. These taxa often have complex and poorly understood life cycles, lack observable, discriminatory morphological characters, and may not be amenable to in vitro culturing. As a result, species identification is frequently difficult. Molecular (DNA sequence) data have emerged as crucial information for the taxonomic identification of plant pathogenic fungi, with the nuclear ribosomal internal transcribed spacer (ITS) region being the most popular marker. However, international nucleotide sequence databases are accumulating numerous sequences of compromised or low-resolution taxonomic annotations and substandard technical quality, making their use in the molecular identification of plant pathogenic fungi problematic. Here we report on a concerted effort to identify high-quality reference sequences for various plant pathogenic fungi and to re-annotate incorrectly or insufficiently annotated public ITS sequences from these fungal lineages. A third objective was to enrich the sequences with geographical and ecological metadata. The results – a total of 31,954 changes – are incorporated in and made available through the UNITE database for molecular identification of fungi (http://unite.ut.ee), including standalone FASTA files of sequence data for local BLAST searches, use in the next-generation sequencing analysis platforms QIIME and mothur, and related applications. The present initiative is just a beginning to cover the wide spectrum of plant pathogenic fungi, and we invite all researchers with pertinent expertise to join the annotation effort.
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| 9. |
- Nilsson, R. Henrik, 1976, et al.
(author)
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Molecular identification of fungi: rationale, philosophical concerns, and the UNITE database
- 2011
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In: The Open Applied Informatics Journal. - : Bentham Science Publishers Ltd.. - 1874-1363. ; 5, s. 81-86
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Research review (peer-reviewed)abstract
- Fungi form a ubiquitous group of largely inconspicuous organisms that play key ecological roles in terrestrial nutrient cycling. The typically subterranean or otherwise unnoticeable nature of fungal life has left mycology with a partial understanding of fungal biology, and progress is hampered by factors such as the difficulty to delimit species and individuals of fungi and the sparsity of discriminatory morphological and physiological characters for reliable species identification. These and other complications have paved the way for DNA sequence data as an important source of information in mycology, and there are now twenty years’ worth of fungal sequence data available for scientific purposes. However, issues of data reliability and generality impede the use of publicly available fungal DNA sequences. The UNITE database for molecular identification of fungi (http://unite.ut.ee) was built as a response to the difficulties facing anyone seeking to identify environmental samples of fungi to species level using molecular data and the major international sequence databases. The present study describes the UNITE database and examines the role of UNITE in the light of emerging sequencing technologies, notably massively parallel (“454”) pyrosequencing. Environmental sampling of fungi is discussed from a taxonomic perspective.
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| 10. |
- Nilsson, R. Henrik, 1976, et al.
(author)
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New features of the UNITE database for molecular identification of fungi
- 2010
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In: 9th International Mycological Congress, Edinburgh, UK (oral presentation; FESIN/UNITE workshop).
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Conference paper (other academic/artistic)abstract
- New features of the UNITE database for molecular identification of fungi will be introduced. These includes an extractor for ITS1 and ITS2 of the ITS region, a new software package for chimera control, many new ways of representing ecological and geographical metadata - including layered maps - and the possibility to annotate GenBank entries.
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| 11. |
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| 12. |
- Schoch, Conrad L., et al.
(author)
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Finding needles in haystacks: linking scientific names, reference specimens and molecular data for Fungi
- 2014
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In: Database: The Journal of Biological Databases and Curation. - : Oxford University Press (OUP). - 1758-0463. ; 2014:bau061, s. 1-21
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Journal article (peer-reviewed)abstract
- DNA phylogenetic comparisons have shown that morphology-based species recognition often underestimates fungal diversity. Therefore, the need for accurate DNA sequence data, tied to both correct taxonomic names and clearly annotated specimen data, has never been greater. Furthermore, the growing number of molecular ecology and microbiome projects using high-throughput sequencing require fast and effective methods for en masse species assignments. In this article, we focus on selecting and re-annotating a set of marker reference sequences that represent each currently accepted order of Fungi. The particular focus is on sequences from the internal transcribed spacer region in the nuclear ribosomal cistron, derived from type specimens and/or ex-type cultures. Re-annotated and verified sequences were deposited in a curated public database at the National Center for Biotechnology Information (NCBI), namely the RefSeq Targeted Loci (RTL) database, and will be visible during routine sequence similarity searches with NR_prefixed accession numbers. A set of standards and protocols is proposed to improve the data quality of new sequences, and we suggest how type and other reference sequences can be used to improve identification of Fungi.
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| 13. |
- Tedersoo, L., et al.
(author)
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454 Pyrosequencing and Sanger sequencing of tropical mycorrhizal fungi provide similar results but reveal substantial methodological biases
- 2010
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In: New Phytologist. - : Wiley. - 0028-646X. ; 188:1, s. 291-301
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Journal article (peer-reviewed)abstract
- Compared with Sanger sequencing-based methods, pyrosequencing provides orders of magnitude more data on the diversity of organisms in their natural habitat, but its technological biases and relative accuracy remain poorly understood. This study compares the performance of pyrosequencing and traditional sequencing for species’ recovery of ectomycorrhizal fungi on root tips in a Cameroonian rain forest and addresses biases related to multi-template PCR and pyrosequencing analyses. Pyrosequencing and the traditional method yielded qualitatively similar results, but there were slight, but significant, differences that affected the taxonomic view of the fungal community. We found that most pyrosequencing singletons were artifactual and contained a strongly elevated proportion of insertions compared with natural intra- and interspecific variation. The alternative primers, DNA extraction methods and PCR replicates strongly influenced the richness and community composition as recovered by pyrosequencing. Pyrosequencing offers a powerful alternative for the identification of ectomycorrhizal fungi in pooled root samples, but requires careful selection of molecular tools. A well-populated backbone database facilitates the detection of biological and technical artifacts. The pyrosequencing pipeline is available at http://unite.ut.ee/454pipeline.tgz.
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| 14. |
- Tedersoo, Leho, et al.
(author)
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Global biogeography of the ectomycorrhizal/sebacina lineage (Fungi, Sebacinales) as revealed from comparative phylogenetic analyses
- 2014
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In: Molecular Ecology. - : Wiley. - 0962-1083 .- 1365-294X. ; 23:16, s. 4168-4183
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Journal article (peer-reviewed)abstract
- Compared with plants and animals, large-scale biogeographic patterns of microbes including fungi are poorly understood. By the use of a comparative phylogenetic approach and ancestral state reconstructions, we addressed the global biogeography, rate of evolution and evolutionary origin of the widely distributed ectomycorrhizal (EcM) /sebacina lineage that forms a large proportion of the Sebacinales order. We downloaded all publicly available internal transcribed spacer (ITS) sequences and metadata and supplemented sequence information from three genes to construct dated phylogenies and test biogeographic hypotheses. The /sebacina lineage evolved 45-57Myr ago that groups it with relatively young EcM taxa in other studies. The most parsimonious origin for /sebacina is inferred to be North American temperate coniferous forests. Among biogeographic traits, region and biome exhibited stronger phylogenetic signal than host family. Consistent with the resource availability (environmental energy) hypothesis, the ITS region is evolving at a faster rate in tropical than nontropical regions. Most biogeographic regions exhibited substantial phylogenetic clustering suggesting a strong impact of dispersal limitation over a large geographic scale. In northern Holarctic regions, however, phylogenetic distances and phylogenetic grouping of isolates indicate multiple recent dispersal events.
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| 15. |
- Tedersoo, Leho, et al.
(author)
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Global diversity and geography of soil fungi
- 2014
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In: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 346:6213, s. artikel nr 1256688-
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Journal article (peer-reviewed)abstract
- Fungi play major roles in ecosystem processes, but the determinants of fungal diversity and biogeographic patterns remain poorly understood. Using DNA metabarcoding data from hundreds of globally distributed soil samples, we demonstrate that fungal richness is decoupled from plant diversity. The plant-to-fungus richness ratio declines exponentially toward the poles. Climatic factors, followed by edaphic and spatial variables, constitute the best predictors of fungal richness and community composition at the global scale. Fungi show similar latitudinal diversity gradients to other organisms, with several notable exceptions. These findings advance our understanding of global fungal diversity patterns and permit integration of fungi into a general macroecological framework.
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| 16. |
- Tedersoo, Leho, et al.
(author)
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Spatial structure and the effects of host and soil environments on communities of ectomycorrhizal fungi in wooded savannas and rain forests of Continental Africa and Madagascar
- 2011
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In: Molecular Ecology. - 0962-1083 .- 1365-294X. ; 20:14, s. 3071-3080
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Journal article (peer-reviewed)abstract
- Mycorrhizal fungi play a key role in mineral nutrition of terrestrial plants, but the factors affecting natural distribution, diversity and community composition of particularly tropical fungi remain poorly understood. This study addresses shifts in community structure and species frequency of ectomycorrhizal (EcM) fungi in relation to host taxa, soil depth and spatial structure in four contrasting African ecosystems. We used the rDNA and plastid trnL intron sequence analysis for identification of fungi and host plants, respectively. By partitioning out spatial autocorrelation in plant and fungal distribution, we suggest that African EcM fungal communities are little structured by soil horizon and host at the plant species and family levels. These findings contrast with patterns of vegetation in these forests and EcM fungal communities in other tropical and temperate ecosystems. The low level of host preference indirectly supports an earlier hypothesis that pioneer Phyllanthaceae may facilitate the establishment of late successional Fabaceae and potentially other EcM host trees by providing compatible fungal inoculum in deforested and naturally disturbed ecosystems of tropical Africa.
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| 17. |
- Tedersoo, Leho, et al.
(author)
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Tidying up international nucleotide sequence databases: ecological, geographical and sequence quality annotation of ITS sequences of mycorrhizal fungi
- 2011
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In: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 6:9
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Journal article (peer-reviewed)abstract
- Sequence analysis of the ribosomal RNA operon, particularly the internal transcribed spacer (ITS) region, provides a powerful tool for identification of mycorrhizal fungi. The sequence data deposited in the International Nucleotide Sequence Databases (INSD) are, however, unfiltered for quality and are often poorly annotated with metadata. To detect chimeric and low-quality sequences and assign the ectomycorrhizal fungi to phylogenetic lineages, fungal ITS sequences were downloaded from INSD, aligned within family-level groups, and examined through phylogenetic analyses and BLAST searches. By combining the fungal sequence database UNITE and the annotation and search tool PlutoF, we also added metadata from the literature to these accessions. Altogether 35,632 sequences belonged to mycorrhizal fungi or originated from ericoid and orchid mycorrhizal roots. Of these sequences, 677 were considered chimeric and 2,174 of low read quality. Information detailing country of collection, geographical coordinates, interacting taxon and isolation source were supplemented to cover 78.0%, 33.0%, 41.7% and 96.4% of the sequences, respectively. These annotated sequences are publicly available via UNITE (http://unite.ut.ee/) for downstream biogeographic, ecological and taxonomic analyses. In European Nucleotide Archive (ENA; http://www.ebi.ac.uk/ena/), the annotated sequences have a special link-out to UNITE. We intend to expand the data annotation to additional genes and all taxonomic groups and functional guilds of fungi.
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| 18. |
- Tedersoo, Leho, et al.
(author)
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Towards global patterns in the diversity and community structure of ectomycorrhizal fungi.
- 2012
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In: Molecular Ecology. - 0962-1083 .- 1365-294X. ; 21:17, s. 4160-70
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Journal article (peer-reviewed)abstract
- Global species richness patterns of soil micro-organisms remain poorly understood compared to macro-organisms. We use a global analysis to disentangle the global determinants of diversity and community composition for ectomycorrhizal (EcM) fungi-microbial symbionts that play key roles in plant nutrition in most temperate and many tropical forest ecosystems. Host plant family has the strongest effect on the phylogenetic community composition of fungi, whereas temperature and precipitation mostly affect EcM fungal richness that peaks in the temperate and boreal forest biomes, contrasting with latitudinal patterns of macro-organisms. Tropical ecosystems experience rapid turnover of organic material and have weak soil stratification, suggesting that poor habitat conditions may contribute to the relatively low richness of EcM fungi, and perhaps other soil biota, in most tropical ecosystems. For EcM fungi, greater evolutionary age and larger total area of EcM host vegetation may also contribute to the higher diversity in temperate ecosystems. Our results provide useful biogeographic and ecological hypotheses for explaining the distribution of fungi that remain to be tested by involving next-generation sequencing techniques and relevant soil metadata.
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