Living on the edge: population ecology of Phengaris teleius in Serbia

Due to their complex and interesting life cycle and alarming conservation status the Large Blue butterflies have become one of the most studied group of insects in Europe. In Serbia, however, Phengaris teleius has recently been discovered (in the far north of the country) and, since this initial finding, significant efforts have been made to map the local distribution of this species and to implement conservation measures. A mark-release-recapture study was initiated to obtain a more detailed report about population size and structure in Serbia. Results have shown that localities and patches within these localities are well connected by migration of butterflies and gave some evidence for metapopulation organisation. The total number of individuals was estimated at 15,000, which makes it one of the largest known metapopulations in Europe. Unusual for populations at the edge of the distribution range, these are characterized with large population estimates and relative stability. Compared to other areas in Europe, butterflies in Serbia start to fly 2 weeks later in the summer, probably a consequence of a late mowing regime initiated during July. Some evidence of a negative relationship between the survival of P. teleius adults and local population density was also found. With favourable management, these populations could remain stable for the foreseeable future. The preservation of large, healthy populations of P. teleius supported by a favourable management and monitoring programme along with the sustainability of individual dispersal translocation between patches should be a prime aim.