Ectomycorrhizal fungi in tropical Africa: hidden diversity, spatial turnover, and functional effects on tree growth.

Abstract

Tropical Africa encompasses several biodiversity hotspots, yet knowledge of ectomycorrhizal (EcM) fungi, key organisms for forest ecosystem functioning, remains fragmented. This study provides the first comprehensive synthesis of EcM fungi across the region, aiming to (i) establish a species checklist as a basis for estimating gamma diversity, (ii) analyze spatial turnover across countries, and (iii) assess the functional effects of EcM fungi on tree seedling growth. We conducted a systematic literature search following PRISMA guidelines, retaining 158 publications published between 1927 and 2025. Species occurrence records were extracted from publications and complemented with data from GlobalFungi and GBIF databases. Statistical analyses in R were used to estimate species richness (Chao2, Jackknife 1 and Jackknife 2), analyze spatial turnover (Jaccard dissimilarity, Mantel correlogram, Generalized Dissimilarity Modelling), and assess the overall effect on tree seedling growth (cross-classified random-effects meta-analysis). We recorded 711 EcM fungal species from 59 genera and 20 families. Russula (169 species), Amanita (81), and Lactifluus (71) were the most represented. Estimated richness reached 1,226 species, indicating substantial undocumented diversity. Community composition showed extremely high heterogeneity among countries (95% dissimilarity), and increased turnover over broader geographic distances (r = -0.13, p < 0.05), suggesting dispersal limitation. Meta-analysis revealed that EcM fungi increased tree seedling growth by an average of 6% per month (p < 0.05), with Scleroderma verrucosum showing particularly strong positive effects. These findings indicate that EcM fungi are unevenly distributed across tropical Africa. They refine our understanding of diversity patterns and highlight the need for targeted sampling and integrating native EcM fungi into forest restoration.