GEOGRAPHIC-VARIATION N REPRODUCTIVE SUCCESS OF THE PARASITOID ASOBARA-TABIDA IN LARVAE OF SEVERAL DROSOPHILA SPECIES

1. Asobara tabida is a parasitoid of Drosophila larvae in fermenting s ubstrates. Because it is a widespread species, it may encounter differ ent biotic and abiotic circumstances in various parts of its range. 2. The species composition of the host population varies over the parasi toid's range: D. obscura-group species (especially D. subobscura) are the main hosts for northwestern and central European parasitoids; D. m elanogaster is the main host for southern European parasitoids. 3. D.m elanogaster larvae can defend themselves against A. tabida by encapsul ating the parasitoid egg, and survival in D. melanogaster is always lo wer than in D.subobscura. 4. Parasitoids from southern European popula tions are much better able to survive in D.melanogaster than their nor thwestern and central European conspecifics; parasitoids from differen t populations are equally well able to survive in D.subobscura. 5. The lower survival in D. melanogaster may be partly compensated for by th e larger size of parasitoids emerging from this host species compared to parasitoids emerging from D. subobscura. 6. Within population group s, larger A. tabida females have more eggs in their ovarioles. Additio nally, southern European females have more eggs and less fat than nort hern and western/central European females. The relationship between si ze and longevity is ambiguous. 7. It is concluded that parasitoids fro m different populations are adapted to region-specific circumstances.