Infrageneric variation in partner specificity: multiple ectomycorrhizal symbionts associate with Gnetum gnemon (Gnetophyta) in Papua New Guinea

Majority of autotrophic plants and fungi associate with multiple mycorrhizal partners, with notable exceptions being Gnetum africanum, Pisonia grandis, and Alnus spp from the phytobiont perspective. We hypothesized that an understorey tree species Gnetum gnemon hosts a narrow range of mycobionts as shown in G. africanum and suggested for South American species. Sampling and molecular analysis of G. gnemon root tips revealed that besides Scleroderma spp. this gymnosperm tree associates with several fungal species from unrelated lineages. However, all Scleroderma isolates that associate with Gnetum spp. belong to a narrow clade close to Scleroderma sinnamariense. Our results demonstrate for the first time that specificity for mycobionts may substantially differ within an ectomycorrhizal plant genus.