Monodominant communities can have a phenotypic trait variation (intraspecific variation) as extreme as the trait variation across a forest with multiple species. An example of such forests are those composed by Quercus, which is one of the most important genera of woody angiosperms in the Neotropics. In Colombia, Q. humboldtii Bonpl., or the Andean oak, is a characteristic element of montane ecosystems and the only representative of this genus. Although there are several studies on the ecology and genetic structure of this species, there are no studies on their functional trait diversity. Functional traits can help to better understand how organisms respond to different environmental conditions. Therefore, in this study we evaluated the functional trait differences in individuals of the Andean oak, in two ontogenetic stages (juveniles and adults) and in different sampling sites. We also evaluated the influence of external and internal filters on the community assembly at each site. Seven functional traits were recorded in juveniles and adults in three sampling sites along the Eastern Cordillera of the Andes. Additionally, we evaluated the influence of external and internal filters, based on a comparison of variance at different organizational levels, using T-statistics. We found significant differences in all functional traits between adults and juveniles, and among sampling sites. We also observed a greater influence of internal filters on the community assembly, compared to external filters. Habitat heterogeneity or facilitation between individuals at different life stages may be influential factors affecting the functional differences between sites. Given that the functional diversity of Andean oak populations is largely unexplored, we highlight the need of more research for the effective conservation of this threatened species.
