Beyond the patch: on landscape-explicit metapopulation dynamics

Climate change threatens biodiversity and species distribution all over the world at unprecedented rates. Human induced changes to landscape structure and habitat are redefining the relation between species and their environment. Understanding, characterizing and modeling the relation between complex landscape features and geographical species presence, the subject of this thesis, have thus gained paramount importance in order to make informed decisions on near- and far-term management strategies for species and landscape protection.

The present thesis pays particular attention to the understanding of how mountain landscapes, described as heterogeneous habitat matrices, govern the presence of a species in space and time. To this end, throughout this thesis a metapopulation model is considered, a spatially-explicit model based on the balance between colonization and extinction events in areas of different suitability. The classical patch-based modelling approach is extended here in various ways in order to incorporate landscape-explicit information about the habitat matrix.

A first theoretical study is performed on geometric, realistic, and real landscapes which highlights how different levels of connectivity, the degree to which different areas of similar habitat are actually linked together in the landscape (say, derived from geomorphic structures, such as valleys and peaks or emerging structures shaped by fluvial erosion and tectonic uplift) impact the dynamic of mountain species under climate change. A second, applied, study investigates how different landscape descriptors derived from Earth Observation data can be used in order to dynamically model the spatial, landscape-explicit, presence of two carabid species (Pterostichus flavofemoratus and Carabus depressus) in the Gran Paradiso National Park. In a final study, the consistency of the metapopulation model is investigated when considering different resolutions of the landscape matrix, i.e. different levels of coarse-graining. This last part is fundamental to the understanding of how conclusions drawn from local studies can be made general and extrapolated to larger regions.

Overall, this thesis bridges the fields of population and landscape ecology, focusing on modelling metapopulation dynamics in complex landscapes seen as the substrate for ecological interactions. The result from the three studies show that metapopulation ecology can profit from the insights of landscape ecology. The combination of the two fields can be a useful tool in furthering the understanding and monitoring of mountain species.