Effects of landscape patterns on species richness--a modelling approach

Ecologists have suspected for a long time that landscape composition and landscape pattern are highly significant for species diversity. However, the way in which species diversity behaves in spatially different arranged landscapes is largely unexplained. This is currently the special focus of our investigation quantifying the relationship between landscape pattern and species richness. Therefore, we built a model which examines the effects of artificially structured landscape patterns on species richness ((alpha)-, (beta)-, (gamma)-diversity). By modifying habitat availability and spatial pattern of the habitat types we obtained different (alpha)-, (beta)- and (gamma)-diversity values. Additionally, we tested the effects of changing species community structure (ratio of generalists versus specialists) on diversity in combination with varying landscape patterns. The results showed that there was always a significant effect of landscape pattern on species richness. However, depending on the species community structure, we observed different strong relationships between habitat aggregation and species diversity. The higher is the rate of generalists in the species pool, the higher is the species richness at the local and regional scale. With increasing landscape aggregation, species richness decreased at all scales in all scenarios, whereas landscapes with only specialists occurring had always the lowest (alpha)-, (beta)- and (gamma)-diversity.