Matching species to a changing landscape - Aquatic macroinvertebrates in a heterogeneous landscape

The goal of this thesis was the development, application and evaluation of a method by which relationships between aquatic macroinvertebrate species and their environment can be explained and aggregated to a manageable number of key relationships. The need for such a method is evident. From an applied point of view, knowledge on the impact of degradation is needed to derive sound possibilities to address the biodiversity crisis. From a fundamental point of view, knowledge on the causal mechanisms is needed to provide a predictive framework which explains how abiotic and biotic factors set limits to species occurrences, ultimately shaping ecosystems. Causal mechanisms explaining a species' environmental requirements are rooted in species traits (e.g., a chitinous exoskeleton, diapausing eggs, parental care, development time). By investigating interrelations between traits and interpreting their function, it was possible to define 'sets of co-adapted species traits designed by natural selection to solve particular ecological problems', which are termed life-history tactics. Species with alternative suites of traits that solved environmental problems in a similar way were assigned to the same tactic. This provided a functional classification spanning species from different systematic groups. Life-history tactics were successfully applied to a fundamental (abundance-occupancy relationship in macroecology) and an applied problem (effects of management in restoration ecology). Life-history tactics can aggregate information over many different species without sacrificing information on the causal mechanisms underlying a species' presence or absence. This makes life-history tactics ideally suited to fill the gap between a single species approach and a community approach. Environmental heterogeneity results from the interplay between abiotic conditions and the effect of interacting species. Life-history tactics can unravel the importance of abiotic boundary conditions and species interactions. Successful conservation of biodiversity will strongly depend on this ability to identify and subsequently strengthen the processes underlying landscape heterogeneit