METAPOPULATION STRUCTURE OF COTESIA-MELITAEARUM, A SPECIALIST PARASITOID OF THE BUTTERFLY MELITAEA-CINXIA

We describe a classical metapopulation structure in a threatened speci es of butterfly, Melitaea cinxia, and in its specialist parasitoid, Co tesia melitaearum, in a large network of small habitat patches. The in cidence of the parasitoid in host populations was positively correlate d with the size of the host population and the area of the habitat pat ch (dry meadows), and negatively correlated with isolation from existi ng parasitoid populations. Our results demonstrate that C. melitaearum increases the risk of local extinction of its host and may thereby pl ay an important role in the metapopulation dynamics of the host butter fly. However, there is substantial population turnover in both species for reasons other than the host-parasitoid interaction as well. The p arasitoid is affected by an abundant generalist hyperparasitoid, Gelis agilis, which showed a strong spatially density-dependent response to C. melitaearum cocoon group size, suggesting that it may contribute t o population regulation of the primary parasitoid. We used an incidenc e function model to study the dynamics of the parasitoid metapopulatio n. The results indicate that the distribution of the parasitoid in the host populations is not at equilibrium, in agreement with the observe d high turnover rate in the host metapopulation.