Population dynamics and the importance of habitat management for conservation of the butterfly Lopinga achine

1. Like many butterflies, the woodland brown Lopinga achine has disappeared from many locations in western Europe due to habitat loss. The population dynamics and the effects of tree and bush cover on population size were studied experimentally south of Linkoping, Sweden. 2. Most populations in the study area were small (< 500 individuals) and fluctuated synchronously between years. Long-term population dynamics and occurrence were closely correlated with tree and bush cover. Populations occurred only at sites with <greater than or equal to> 60% canopy cover, but population density decreased sharply where cover exceeded 90%. Survival from egg to adult was highest at the edges of glades (2.3 adults per female) and lowest in the deepest shade (0.7 adults) or open sun (0.6 adults). The annual rate of canopy closure at unmanaged sites decreased linearly with tree and bush cover, approximately 1% closure at 60% cover and 0.3% at 85% cover, making it possible to predict the impact of habitat changes for L achine. 3. In 1992-95, vegetation was cleared experimentally to create new glade edges at six unmanaged sites where the risk of extinction was high because few glades remained. On average, population size at five of the managed sites increased by > 90%. The population at the sixth site, managed in 1995, decreased by 30%. 4. Cover of the host-plant Carex montana increased significantly at edges of new glades and decreased in closed unaffected woods. Successful restoration probably requires the presence of C. montana along edges of new glades from the onset of management because this plant was slow to colonize plots where it was initially absent. 5. Currently, 86% of the sites in southern Sweden occupied by L. achine are unmanaged. If this situation continues, the metapopulation in this study will probably collapse within 20-40 years. Recovery programmes for L. achine should emphasize metapopulation dynamics, host-plant cover and vegetation dynamics over time. As with many butterflies, successful conservation requires a blend of detailed autoecology and active site management to produce the required successional conditions.