Format: ORAL

Lohengrin A. Cavieres

1 Departamento de Botánica, Facultad de Ciencias Naturales y Oceanográficas, Universidad de Concepción 2 Instituto de Ecología y Biodiversidad (IEB).

Facilitation among plants occurs when the fitness of one species increases in the presence of neighboring plants. It has been suggested that the importance of facilitative interactions among plants increase with the environmental harshness. In high-elevation (alpine) habitats the abiotic harshness increases with elevation, and several studies have addressed how the intensity of facilitation among plants change along elevational gradients. However very few have addressed the frequency and importance of these interactions for the diversity of alpine environments. Using a dataset spanning 78 sites and 5 continents, we assessed the relative importance of facilitative interactions in determining plant diversity in alpine ecosystems. We focused on alpine plant communities dominated by cushion plants, a particular growth form that act as nurse plant for other species. Samples from cushions and open areas were combined in a single matrix accounting for the difference in cover between both microhabitats, and through rarefaction curves we assessed how many more species are added to the community due to the presence of cushions. In general, the presence of cushions consistently increased species richness at the entire community level. The magnitude of these increases in species richness varied with habitat severity where cushion species enhanced species richness more in systems with harsher environments and hence inherently impoverished in local diversity. Facilitative interactions with the nurse species appear to act as a safety net sustaining diversity under harsh conditions, demonstrating the importance of positive interactions among species in determining the diversity of alpine habitats in general. Funded by Fondecyt-1211197, ACT-210038, FB-0006.