Ectomycorrhizal fungi are shared between seedlings and adults in a monodominant Gilbertiodendron dewevrei rain forest in Cameroon

Ectomycorrhizal networks may facilitate the establishment and survival of seedlings regenerating under the canopies of tropical forests and are often invoked as a potential contributor to monodominance. We identified ectomycorrhizal fungi in a monodominant Gilbertiodendron dewevrei (Fabaceae) rain forest in Cameroon, using sporocarps and ectomycorrhizae of three age categories (seedlings, intermediate trees, and large trees) and tentatively revealed nutrient transfer through ectomycorrhizal networks by measuring spontaneous isotopic (C-13 and N-15) abundances in seedlings. Sporocarp surveys revealed fewer ectomycorrhizal fungal taxa (59 species from 1030 sporocarps) than molecular barcoding of ectomycorrhizal roots (75 operational taxonomic units from 828 ectomycorrhizae). Our observations suggest that ectomycorrhizal fungal diversity is similar to that in other mixed tropical forests and provide the first report of the Tuber-Helvella lineage in a tropical forest. Despite some differences, all age categories of G.dewevrei had overlapping ectomycorrhizal fungal communities, with families belonging to Thelephoraceae, Russulaceae, Sebacinaceae, Boletaceae, and Clavulinaceae. Of the 49 operational taxonomic units shared by the three age categories (65.3% of the ectomycorrhizal fungal community), 19 were the most abundant on root tips of all categories (38.7% of the shared taxa), supporting the likelihood of ectomycorrhizal networks. However, we obtained no evidence for nutrient transfer from trees to seedlings. We discuss the composition of the ectomycorrhizal fungal community among the G.dewevrei age categories and the possible role of common ectomycorrhizal networks in this rain forest. Resume Les reseaux mycorhiziens pourraient faciliter l'etablissement et la survie des semis sous la canopee des forets tropicales, en particulier dans les forets monodominantes. Pour etudier ce mecanisme, des champignons ont ete identifies a partir de sporophores et d'ectomycorhizes sur trois categories d'age (semis, arbres intermediaires, arbres adultes) et leur role potentiel dans le transfert de nutriments au benefice des semis a ete teste par des mesures de teneurs isotopiques spontanees (C-13 et N-15) dans une foret monodominante a Gilbertiodendron dewevrei (Fabaceae) du Cameroun. Les sporophores ont ete moins diversifies (59 especes parmi 1030 sporophores) que les ectomycorhizes (75 unites taxonomiques operationnelles parmi 828 ectomycorhizes). La diversite fongique ne differe pas de celle des forets tropicales mixtes. Nous decrivons la lignee Tuber-Helvella pour la premiere fois en foret tropicale. Malgre des differences, les categories d'age, G.dewevrei, partagent des especes de Thelephoraceae, Russulaceae, Sebacinaceae, Boletaceae et Clavulinaceae. Parmi les 49 unites taxonomiques operationnelles (65,3% de la communaute fongique) partages par les trois categories d'age, 19 d'entre eux (38,7% de la communaute fongique partagee) formeraient un reseau mycorhizien commun entre les arbres et les semis. Toutefois, les approches isotopiques n'ont pas permis de detecter de transfert de nutriments des arbres aux semis. Nous discutons la composition et le role des communautes fongiques des trois categories d'age de G.dewevrei dans cette foret tropicale humide.