Advancing our understanding of animal dispersal and functional connectivity in human-altered landscapes: conceptual considerations and their empirical and simulation-based demonstration
von Femke Pflüger
Datum der mündl. Prüfung:2019-12-17
Betreuer:Prof. Dr. Niko Balkenhol
Gutachter:Prof. Dr. Niko Balkenhol
Gutachter:Prof. Dr. Matthias Waltert
EnglischDispersal, the movement from a natal site to a new breeding site, is a key process in ecology and evolution. By determining the dynamics and distribution of populations and gene flow among them, dispersal is essential for species persistence, especially for species in human-dominated landscapes threatened by habitat loss and fragmentation. Effective conservation management requires on one side an in-depth understanding of individual dispersal behavior and on the other side indicators that reliably specify negative environmental effects on dispersal prior to extinction. However, simplified assumptions are made on the behavioral process of dispersal and on the complexity of environmental influences. This could lead to false or incomplete conclusions to what extent the landscape is influencing dispersal and resulting distributions of populations and genetic variation. The thesis therefore deals with an integration of behavioral ecology into analyses on landscape-dispersal pattern relationships and examines the potential of reliable early-warning indicators for conservation. After a general introduction into the research context in chapter 1, resource selection functions and resemblance measures are used to illustrated in chapter 2 how different environmental factors are shaping the distribution of reintroduced brown bears (Ursus arctos) in the Central European Alps. Local habitat suitability and habitat similarity are important drivers of brown bear settlement, suggesting that testing different hypothesis on how the environment influences individual dispersal behavior at the three different stages of dispersal (emigration, movement and immigration) is vital for correctly identifying environmental predictors of population distribution. Chapter 3 deals with the conceptual and analytical integration of several environmental factors that are important for the behavioral process of dispersal in landscape genetic studies. A combined integration of local and intervening environmental factors can be feasible by using metapopulation connectivity indices, which allows to evaluate their relative importance in shaping resulting genetic pattern. The consideration of several environmental factors in landscape genetic studies could allow a comprehensive evaluation of landscape effects on dispersal and resulting distribution of populations and genetic variation. Individual-based simulations are used in chapter 4 to examine the development of genetic variation and population abundance during continuous habitat loss. Genetic diversity, genetic differentiation and population abundance exhibit non-linear responses to habitat loss with rapid changes beyond critical tipping points of habitat amount. Since the negative effects of habitat loss manifest first in genetic data before detectable changes in population abundance occur, genetic data could serve as an early warning indicator of upcoming species extinction in conservation. Chapter 5 summarizes and discusses the main findings of this work with respect to the current research context. The results of this work can enhance the understanding and prediction of dispersal in heterogeneous and human-modified landscapes and contribute to the protection of species threatened by habitat loss and fragmentation.
Keywords: Wildlife Sciences; Dispersal; Functional connectivity; Habitat suitability; Habitat loss; Resource / step selection functions; Landscape genetics; Individual-based simulations