Metapopulation structure and conservation of the cranberry fritillary Boloria aquilonaris is (lepidoptera, nymphalidae) in Belgium

The spatial structure and dynamics of local populations of an endangered sp ecialist butterfly, the cranberry fritillary Boloria aquilonaris living on peat bogs was studied in Southern Belgium. Seventeen populations an the Ard enne uplands (Plateau des Tailles, Hautes-Fagnes, Plateau de Recogne, Plate au de St-Hubert) and one population in the forested lowlands of Lorraine we re monitored in 1996. The population structure and dynamics were investigat ed on the "Plateau des Tailles", the most important area for B. aquilonaris in Belgium with 12 distinct populations. A. mark-release-recapture survey was carried out on four sites in 1995 and 1996 within an area of 85 km(2). An unexpectedly high degree of interchange was detected between sites. This connectivity, together with the asynchrony of local dynamics suggest that populations act as a single metapopulation within the whole study area. We observed that adult butterflies were less prone to move out of their natal patch when this patch was small (< 1 ha), isolated and sheltered. Therefore , such patches must also be taken into account when planning the conservati on of the species. (C) 1998 Elsevier Science Ltd. All rights reserved.