Biodiversità funzionale lungo gradiente altitudinale: un approccio multi-taxa nelle Alpi occidentali

In the last decades researchers linked biodiversity to ecosystem functioning, showing that biodiversity loss leads to the loss of ecosystem services. Functional diversity (FD) has been detected as one of the biodiversity components that better explain the mechanisms linking biodiversity and ecosystem processes. FD is defined as the distribution of species and of abundance within the functional space and relies on the principle that species are not equally distinct. Functional diversity has been shown to be a sensitive and practical tool to understand how biodiversity and environment influence each other and to predict community response to environmental changes. In my study, I analysed how functional diversity of birds, butterflies, carabids, spiders and staphylinids changes along altitudinal gradients in mountain ecosystems. The study fits inside the project ¿Animal biodiversity monitoring in alpine environment¿ that involves three protected areas in the Western Italian Alps. It is a long-term monitoring scheme started in 2006. The data used in this study refer to the first two sampling seasons: 2006-2008 and 2012-2013. The aims of my work have been: 1) to select the set of functional traits that can better explain how communities are influenced by environmental changes and to create a functional database for each taxon; 2) to compute different FD indices and infer how much each trait influences the quality of the indices; 3) to assess which is the relationship that occurs between each index and species richness and determine the changes between the sampling seasons; 4) to analyse the influence of environmental variables on FD. My results highlight that the study of functional diversity in mountain ecosystems has some constrains. First of all, it is difficult to find ecological and life-history information for many species that are endemic to the Alps or specialised to the alpine environment. Secondly, species-poor communities, typical of high altitude, partially reduced our possibility to fully describe the multi-dimensional functional space. In any case, interesting results which highlight differences between taxa and sampling seasons have been found. In particular, and according to literature, different components of functional diversity have different relationship with species richness, but the saturation curve of Michaelis-Menten was the model that better fits this relationship. Differences occurred between years, indicating that few changes in community composition may have already led to functional differences, despite the short time scale considered. Indeed, alpine environment are strictly linked to weather variability and characterised by less stabile communities than at low altitude. Moreover, FD showed in most cases a strong relationship with temperature and altitude, indicating that these are the environmental factors that most influence the community functional structure. Despite its constrains, FD is fundamental to have a deeper insight on how environmental changes are driving community functional structure. This will allow to identify the most vulnerable areas, where to develop sustainable management strategies that can lead to the maintenance of overall ecosystem functioning.