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

The spatial structure and dynamics of local populations of an endangered specialist butterfly, the cranberry fritillary Boloria aquilonaris living on peat bogs was studied in Southern Belgium. Seventeen populations on the Ardenne uplands (Plateau des Tailles, Hautes-Fagnes, Plateau de Recogne, Plateau de St-Hubert) and one population in the forested lowlands of Lorraine were monitored in 1996. The population structure and dynamics were investigated 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 km2. 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 conservation of the species.