Ectomycorrhizal diversity associated with seedlings and mature trees in the Neotropics

Toyota Auditorium, Howard H. Baker Jr. Center for Public Policy

The ectomycorrhizal (EM) leguminous canopy tree Dicymbe corymbosa forms monodominant stands in the tropical forests of the central Guiana Shield region. Within these stands, D. corymbosa maintains a large bank of shade-tolerant seedlings that result from mast fruiting events. It has been proposed that common mycorrhizal networks support Dicymbe seedling recruitment and facilitate persistent monodominance, and that an absence of appropriate symbionts may inhibit these seedlings from successfully establishing in nearby mixed forests of AM-associated trees. Little is known, however, about the actual fungi forming mycorrhizae with these seedlings. Using molecular methods we examined EM fungi associated with roots of D. corymbosa seedlings within monodominant stands and along transition zones into AM-dominated mixed forest. Seedlings within monodominant stands hosted significantly higher EM fungal species diversity than those in transition zones, but no effect of distance from parent tree was detected in either location. EM fungi commonly recovered on seedlings included members of the Clavulinaceae, Inocybaceae, Russulaceae, and Thelephoraceae, all of which have been consistently found on adult D. corymbosa roots. The Boletaceae, however, were notably under-represented on seedlings.