Abstract
Polyporus leprieurii var. yasuniensis is a prolific wood-decay fungus inhabiting the forest floor of one of the most biodiverse places on earth, the Yasuní National Park in Ecuador. Basidiocarps and aerial rhizomorphs are commonly found growing on woody debris distributed along the floor of this forest ecosystem. Because of the extraordinary abundance of this fungus in the tropical rainforest, we carried out investigations to better understand the biological and ecological aspects contributing to its prolific distribution. Data on growth inhibition in paired competition studies with sixteen fungal isolates exemplifies defense mechanisms used to defend its territory, including pseudosclerotial plates and the development of a melanized rhizomorphic mat. Results of biomass loss on eleven types of tropical wood in microcosm experiments demonstrated the broad decay capacity of the fungus. In and ex situ observations provided information on how long rhizomorphs can prevail in highly competitive ecosystems as well as stressful conditions in the laboratory. Finally, high concentrations of metal ions occur on rhizomorphs as compared to colonized wood. Sequestration of metal ions from the environment by the melanized rhizomorphs may offer protection against competitors. The development of melanized rhizomorphs is key to find and colonize new substrates and resist changing environmental conditions.