Phylogenetic diversity and affiliation of tropical African ectomycorrhizal fungi

Abstract

Ectomycorrhizal fungi form a mutualistic symbiosis with plant roots, and are key for nutrient cycling in many ecosystems. Here we study the ectomycorrhizal fungal communities in the Oueme Superieur reserve forest in Benin (West Africa). We use phylogenetic methods to test if the species from the study site are closer to other tropical African species than to species from other regions. The Oueme Superieur community was represented by nine Operational Taxonomic Units in Amanitaceae, one in Boletaceae, one in Cantharellaceae, one in Cortinariaceae, two in Inocybaceae, fourteen in Russulaceae and three in Sclerodermataceae. Of these thirty-one Operational Taxonomic Units, twenty had no record in other areas, and unique Operational Taxonomic Units were found in all families except Boletaceae and Sclerodermataceae. The added phylogenetic diversity from these unique Operational Taxonomic Units tended to be higher than expected by chance in all families but Cantharellaceae. The Operational Taxonomic Units are generally fairly distinct and contribute proportionally to the phylogenetic diversity, reflecting that they do not only represent recently diverging species, but also more divergent lineages. Our analyses of the different families show that the communities of Amanitaceae, Inocybaceae, and Russulaceae are more closely related to the general Afrotropic community than expected by chance, at least measured as the nearest taxon distance. The lack of significant patterns in the other families may be due to lack of power, but the wide distribution of many Operational Taxonomic Units suggests that there are not likely to be strong patterns. It is only for Russulaceae that there is a significant pattern in the Oueme Superieur ectomycorrhizal fungal communities at a regional scale, with the Operational Taxonomic Units being less closely related than expected. At a global scale the patterns seem to reflect the overall distribution of the Afrotropic ectomycorrhizal fungal community. The phylogenetic patterns in the Afrotropic communities differ between families, from clustered to no clear pattern to over-dispersed measured as mean average phylogenetic distance. Each family seems to have its own biogeographic history, and there is no clear pattern for the ectomycorrhizal fungal community at large. Despite the lack of comprehensive taxonomic work to identify fungi in a region, it is still possible to draw some conclusions on their diversity using molecular phylogenetic methods. However, limited success in getting good sequence data from specimens, probably due to preservation issues in the field, and the lack of well annotated molecular data from many regions limit the power of these inferences.