Simple tools for the evaluation of protected areas for the conservation of grasshoppers

Spatial conservation prioritization needs a strong informational background on the conservation value of sites. However, standard diversity indices do not distinguish between less valuable (e.g. invasive species) and highly valuable species (e.g. threatened endemics). Furthermore, park managers often lack the taxonomic capacity to study species-rich insect groups. Therefore, there is a need for indices that consider the conservation value of species and simple indicators for the conservation value of sites. The aim of our study was to develop such indices and test them in a biodiversity hotspot. We studied grasshopper diversity in the UNESCO World Heritage “Cape Floral Region Protected Areas” (South Africa). We used endemism, mobility and rarity to calculate a grasshopper conservation index (GCI) for each species and site and a standardized index (GCIn) to evaluate the mean conservation value of species per site. We analyzed the indicator value (IndVal) of environmental factors for identifying sites of high conservation value or high biodiversity. Unlike plant species richness, we found the highest species richness in the Eastern Cape. The main factors determining grasshopper diversity were vegetation heterogeneity, altitude and cover of bare ground. The abundance of wingless grasshopper species and the ratio of wingless to winged species were suitable indicators of conservation value (regarding the diversity of rare or endemic species) of sites. These factors might function as conservation indicators in other regions as well, as they are generally associated with the occurrence of endemic species. GCI/GCIn are globally applicable tools for the evaluation of grasshopper communities.