Towards the use of ecological heterogeneity to design reserve networks: a case study from Dadia National Park, Greece

In this paper, we present a novel approach for using ecological heterogeneity in reserve design. We measured five ecological heterogeneity indices (EHI) and we used a database of six biological groups (woody plants, orchids, orthopterans, aquatic and terrestrial herpetofauna and passerine birds) across 30 sites in a Mediterranean reserve (Greece). We found that all the five EHI were significantly related to the overall species richness and to the species richness of woody plants and birds. Two indices, measuring vertical vegetation complexity (1/D) and horizontal heterogeneity of landcover types (SIDI) in terms of Simpson's index, predicted well overall species richness and had significantly higher values inside the complementary reserve networks designed after five of the six biological groups. We compared five methods of forming reserve networks. The method of ecological heterogeneity (selecting those sites with the greatest 1/D and then SIDI) was less efficient (non-significantly) than the species-based methods (scoring and complementary networks) but significantly more efficient than the random method (randomly selected network). We also found that the method of complementary ecological heterogeneity (selecting those sites where each EHI had its maximum value) was not that efficient, as it did not differ significantly from the random method. These results underline the potential of the ecological heterogeneity method as an alternative tool in reserve design.