Additive partitioning of species diversity across multiple spatial scales: Implications for regional conservation of biodiversity

Ecologists and conservation biologists are keenly interested in how patterns of species diversity change across spatial scales. We examined how additive partitioning can be used to statistically evaluate spatial patterns of species diversity and develop conservation strategies. We applied additive partitioning to data on arboreal beetle diversity (richness, Shannon, Simpson) collected from a nested design consisting of four hierarchical levels-trees, forest stands, sites, and ecoregions-that corresponded to increasingly broader spatial scales within the eastern deciduous forest of Ohio and Indiana (U.S.A.). A significant percentage (relative to that of randomization tests) of total species richness and Shannon and Simpson diversity was attributed to beta diversity between ecoregions and, to a lesser extent, among sites (parks and nature preserves) within ecoregions. Hierarchical cluster analysis corroborated these findings. We also found differences between rare species (<0.05% of total abundance) and common species (>0.5% of total abundance) in the overall percentage of richness explained by each spatial scale. Rare species accounted for the majority (45%) of the 583 total beetle species in our study and were strongly influenced by broad spatial scales (i.e., ecoregions), whereas the richness of common species was significantly greater than expected across the range of spatial scales (from trees to ecoregions). Our results suggest that the most effective way to preserve beetle diversity in the eastern deciduous forest of the United States is to acquire and protect multiple sites within different ecoregions. More generally, we advocate the use of diversity partitioning because it complements existing models in conservation biology and provides a unique approach to understanding species diversity across spatial scales.