Effects of Human Disturbance on Tropical Montane Epiphyte Assemblages: Studies from the Ecuadorian Andes

The present dissertation aims at contributing to our understanding of the processes that determine epiphyte diversity in anthropogenic landscapes. At a dry forest site, epiphytic bryophytes responded sensitively to human disturbance, but vascular epiphytes did not. At a moist forest site, vascular epiphyte assemblages on isolated remnant trees were impoverished markedly and strongly biased to xerotolerant taxa. Field-experimental work at this site could show that this was related to 1) strongly increased mortality of established plants on isolated remnant trees following their isolation in clear-cuts, and 2) reduced and compositionally biased establishment on isolated trees. Evidence is presented to suggest that growth conditions (especially microclimate) are a more decisive predictor of epiphyte communities in disturbed habitats at these sites than dispersal constraints. The response of epiphyte communities to disturbance may further vary with mesoclimate.