Spatial Ecology of the Fungal Genus<i>Xylaria</i>in a Tropical Cloud Forest

Abstract

Abstract Fungal symbioses with plants are ubiquitous, ancient, and vital to both ecosystem function and plant health. However, benefits to fungal symbionts are not well explored, especially in non‐mycorrhizal fungi. The Foraging Ascomycete hypothesis proposes that some wood‐decomposing fungi may shift life‐history strategies to endophytism to bridge gaps in time and space between suitable substrates. To test this hypothesis we examine spatial relationships of X ylaria endophytic fungi in the forest canopy with X ylaria decomposer fungi on the forest floor. We sampled for fungi of the genus X ylaria using a spatially explicit sampling scheme in a remote Ecuadorian cloud forest, and concurrently carried out an extensive culture‐based sampling of fungal foliar endophytes. We found 36 species of X ylaria in our 0.5 ha plot, 31 of which were found to only occur as fruiting bodies. All five species of X ylaria found as endophytes were also found as fruiting bodies. We also tested the relationships of both stages of these fungi to environmental variables. Decomposer fungi were differentiated by species‐specific habitat preferences, with three species being found closer to water than expected by chance. In contrast, endophytes displayed no sensitivity to environmental conditions, such as host, moisture, or canopy cover. We found evidence of spatial linkage between life stages in two species. We also demonstrate that direct transmission of endophytes from leaves to woody substrates is possible. These results indicate that endophytism may represent one way for decomposer fungi to escape moisture limitation, and that endophytic fungi may act as sources of dispersal for decomposer fungi consistent with predictions of the Foraging Ascomycete hypothesis.