Assessing preservation priorities of caves and karst areas using the frequency of endemic cave-dwelling species

Endemic and rare species as bioindicators of habitat vulnerability were used to develop protection and management plans for biotope prioritization (mainly islands habitats, lava tubes or groundwaters). Due to their narrow distribution, the endemic species (species confined to a restricted geographic area) are more susceptible to ecological disequilibrium and habitat loss than the widespread ones. Consequently, endemics become endangered in the context of ecological disturbance caused by anthropogenic pressure, making them suitable candidates to assess environmental preservation needs. Taking into consideration that most of the stygobitic and troglobitic species are endemic and confined to specific karst areas, based on their association and frequency we propose an endemicity index (EI) adapted to the fragmented nature of the cave habitat. We used a double ranking methodology: (1) ranking the endemic species according to their frequencies in caves, and (2) ranking the caves according to their EI computed for a geographic area. Further, by mapping the caves based on their related EI, we identified the hotspots of vulnerable karst areas. The EI has been developed using as case study of 380 caves from Romania, known up to now to be inhabited by a total of 278 endemic stygobitic and troglobitic species and subspecies. In our study area, 35 out of 380 caves with endemic species, narrowly distributed to karst areas of the Carpathian massifs and Dobrogea, had a considerable high EI. The EI proves to be highly sensitive to unique taxa (endemics recorded in only one cave) and also to other endemic taxa - recorded in more than one cave. However, all the endemites are confined to a specific geographic area (in this case of study - the Carpathians and Dobrogea karst area). EI provides a reliable criterion to rank caves using the contribution of endemic species in order to assess cave and karst vulnerability and prioritize them for environment protection management.