View article

Thousands of ectomycorrhizal (ECM) fungal species exist, but estimates of global species richness of ECM fungi differ widely. Many genera have been proposed as being ECM, but in a number of studies evidence for the hypothesized ECM habit is lacking. Progress in estimating ECM species richness is therefore slow. In this paper we have retrieved studies providing evidence for the ECM habit of fungal species and for the identification of the mycobiont (s) in specific ECM associations, using published and web-based mycorrhiza literature. The identification methods considered are morphoanatomical characterization of naturally occurring ECMs, pure culture synthesis, molecular identification, and isotopic evidence. In addition, phylogenetic information is also considered as a relevant criterion to assess ECM habit. Of 343 fungal genera for which an ECM status has been alleged, about two thirds have supportive published evidence or ECM status can be at least hypothesized. For the remaining taxa, currently no indication exists as for their ECM nutritional habit, besides field observations of associations with putative hosts. Our survey clearly indicates that current knowledge of ECM fungal diversity, as supported by experimental evidence, is only partly complete, and that inclusion of many fungal genera in this trophic and ecological category is not verified at this stage. Care must thus be used when compiling lists of ECM and saprotrophic fungi in community-level studies on the basis of published information only. On the basis of our literature search we conservatively estimate ECM species richness around 7750 species. However, on the basis of …