Importance of landscape heterogeneity for the conservation of aquatic macroinvertebrate diversity in bog landscapes

Heterogeneous landscapes are biodiversity `hotspots¿. Degradation resulting from acidification, desiccation and eutrophication not only decreases habitat quality, but also causes heterogeneity to decline. While restoration measures aim at restoring habitat quality, they can further reduce heterogeneity when they affect large parts of an area (large scale) or cause disturbance (high intensity). Successful restoration of biological diversity therefore requires knowledge of the mechanisms underlying the relation between landscape heterogeneity and species diversity. This paper addresses two questions: (1) Do bog pools in a heterogeneous landscape harbour more aquatic macroinvertebrate species than those located in more homogeneous landscapes? (2) Is distance between water bodies an important factor determining species composition? To answer the first question, aquatic macroinvertebrate assemblages in bog pools with a similar water chemistry range were studied in bog remnants differing in landscape heterogeneity. The most heterogeneous remnant (Korenburgerveen) had the highest scores on all diversity indices, indicating that bog pools situated in a heterogeneous landscape have a higher diversity than those located in more homogeneous landscapes. To answer the second question, the most heterogeneous remnant was studied in greater detail. Adjacent water bodies were more similar in species composition than expected on the basis of differences in local environmental conditions. This indicates that not only environmental conditions, but also spatial configuration determines the species composition. In conclusion, species diversity in heterogeneous landscapes (i.e. those with a combination of different parts) is greater than the total number of species that would be present if the individual parts were separated. Conservation and restoration strategies should not only focus on enlarging habitat areas and restoring a single habitat type, but also on conserving and strengthening landscape heterogeneity. We present some guidelines for improving habitat quality without causing heterogeneity to decline.