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.

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.

454 Pyrosequencing and Sanger sequencing of tropical mycorrhizal fungi provide similar results but reveal substantial methodological biases.

• 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.

Low diversity and high host preference of ectomycorrhizal fungi in western Amazonia, a neotropical biodiversity hotspot.

Information about the diversity of tropical microbes, including fungi is relatively scarce. This study addresses the diversity, spatial distribution and host preference of ectomycorrhizal fungi (EcMF) in a neotropical rainforest site in North East Ecuador. DNA sequence analysis of both symbionts revealed relatively low richness of EcMF as compared with the richness of temperate regions that contrasts with high plant (including host) diversity. EcMF community was positively autocorrelated up to 8.5+/-1.0-m distance-roughly corresponding to the canopy and potentially rooting area of host individuals. Coccoloba (Polygonaceae), Guapira and Neea (Nyctaginaceae) differed by their most frequent EcMF. Two-thirds of these EcMF preferred one of the host genera, a feature uncommon in boreal forests. Scattered distribution of hosts probably accounts for the low EcMF richness. This study demonstrates that the diversity of plants and their mycorrhizal fungi is not always related and host preference among EcMF can be substantial outside the temperate zone.