The Origin of GregariousMuscidifurax(Hymenoptera: Pteromalidae) in North America: An Analysis Using Molecular Markers

Parasitic wasps of the genusMuscidifurax(Hymenoptera: Pteromalidae) are pupal parasitoids of various diptera and are important biological control agents of flies that breed in accumulated animal wastes and garbage. Most species ofMuscidifurax,including both North American speciesMuscidifurax raptorandMuscidifurax zaraptor,oviposit a single egg on each host (solitary oviposition). Recent collections in the central United States, however, have revealed populations ofMuscidifuraxwith gregarious oviposition. Previously, the only known gregariousMuscidifuraxwas the South American speciesMuscidifurax raptorellus,which is gregarious in Chile but solitary in Peru. We have developed species-specific molecular markers for the genusMuscidifuraxby RAPD–PCR and have used these markers to identify the origin of gregariousness in North America. Banding patterns from three of four primers clearly distinguishedM. raptor, M. zaraptor,andM. raptorellus,and those from the gregarious North American population most closely resembled those of South AmericanM. raptorellus.We conclude that the appearance of gregarious oviposition in central North America resulted from the introduction of gregariousM. raptorellus,rather than a novel development of gregariousness within existing populations ofM. raptororM. zaraptor.GregariousMuscidifuraxare very aggressive in the laboratory and are effective biological control agents, but how they interact with other parasitoid species that attack dipteran pupae in the field remains unknown.