Understanding how plant communities respond to stress gradients can help to predict the effects of environmental changes. In tropical montane forests, elevation and topography comprise natural stress gradients, and high habitat fragmentation represents an additional human-induced factor of stress. This thesis evaluates how elevation, topography and edge effects drive the functional diversity of woody species, and how edge effects extend on the genetic structure of two species of Clusia. Soil properties were shown to be important drivers for leaf traits. Species with a conservative strategy were dominant in more stressful habitats; thus edge effects translated into shifts of plant strategies. Edge effects were also shown to break-up the genetic structure and increase the genetic differentiation of Clusia populations. Thus, it is shown how fragmentation, through edge effects, plays an important role for driving the functional composition and genetic patterns of woody species.