Spatial Ecology of the Fungal Genus Xylaria in a Tropical Cloud Forest

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 Xylaria endophytic fungi in the forest canopy with Xylaria decomposer fungi on the forest floor. We sampled for fungi of the genus Xylaria 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 Xylaria in our 0.5 ha plot, 31 of which were found to only occur as fruiting bodies. All five species of Xylaria 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.     

On identifying common distribution patterns and their causal factors: a probabilistic method applied to pteridophytes in the Iberian Peninsula

Abstract. The aim of this quantitative biogeographical analysis is to identify the existence of specific groups of pteridophytes with significantly similar distribution patterns (chorotypes) in the Iberian Peninsula, as well as to infer the environmental factors that may explain such groupings. We have applied a classification method to the pteridophyte species and have then tested the significance of the resulting groups. This allows the distinction of groups of species that occur together more frequently than expected at random from those which are just a product of the cluster analysis. The majority of the 113 pteridophyte species in the Iberian Peninsula are not distributed independently from each other, but eighteen chorotypes exist that are common to various species and three chorotypes that consist of one species each. Five species are distributed independently of the other species, and so their distribution areas overlap and segregate from the others at random. With the aim of finding a relation between the chorotypes identified and the processes that determine them, we investigated the possible incidence of certain environmental factors on the chorotype distributions by means of logistic regression. Factors that appear most frequently as possible causes of the distribution of the chorotypes are the water availability, climatic stress, availability of environmental energy, and disturbances caused by floods. Resumen . El objetivo de este análisis biogeográfico cuantitativo es identificar la posible existencia de grupos de especies de pteridófitos con patrones de distribución significantivamente similares (corotipos) en la Peninsula Ibérica, así como analizar los factores ambientales que explican tales grupos. Hemos aplicado un método de clasificatión biogeográfica de especies y después hemos comprobado la significación de los grupos resultantes. Esto nos ha permitido distinguir los grupos de especies que se asocian con más frecuencia de lo esperado por azar de aquellos grupos que se deben únicamente al análisis de agrupación. La mayoría de las 113 especies de pteridófitos en la Península Ibérica no se distribuyen independientemente unas de otras, sino que existen 18 corotipos que son comunes a varias especies y tres que están formados por una sola especie. Cinco especies se distribuyen independientemente de las restantes, y por tanto, sus áreas de distribución se solapan y se segregan con las demás al azar. Con objeto de encontrar una relación entre los corotipos identificados en el presente trabajo y los procesos que los determinan, investigamos por medio de regresiones logísticas la posible incidencia de ciertos factores ambientales sobre las distribuciones de los corotipos. Los factores que han aparecido más frecuentemente como posibles causas de las distribuciones de los corotipos son la disponibilidad de agua, el estrés climático, la energía ambiental disponible y los disturbios causados por las inundaciones.