Landscape metrics as indicators: Quantifying habitat network changes of a bush-cricket Pholidoptera transsylvanica in Hungary

Fragmentation of habitats is a serious problem for many endangered species; a possible solution is the maintenance of landscape connectivity. Due to scarce sources, in managing and planning landscapes exact and quantitative priorities must be set. Application of mathematical tools, such as network analysis, can be useful help in these decisions. We illustrate the possibilities and results of this approach with a case study of endangered Pholidoptera transsylvanica bush-cricket population in the Aggtelek Karst, Northeast-Hungary, which inhabits 39 habitat patches connected with ecological corridors. A key issue in the long-term survival of this metapopulation is the maintenance of gene flow (by preserving the connectivity of the habitat network). We evaluated the landscape graph and our results are compared to earlier ones based on older methods. During the comparison, we used several network indices to set quantitative conservation preferences. In addition, we would like to draw attention to the need for constant monitoring (and possible treatments), because several changes (like secondary succession) have occurred during the years between the two studies, threatening landscape connectivity and long-term survival of certain species. A potential solution for preventing fragmentation is establishing new corridors or improving the existing ones: we estimated the possible effects of these changes. New corridors did not have major effect on the system; maintaining already functioning corridors is more effective.