The origin of gregarious Muscidifurax (Hymenoptera: Pteromalidae) in North America: An analysis using molecular markers

Parasitic wasps of the genus Muscidifurax (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 of Muscidifurax, including both North American species Muscidifurax raptor and Mudscidifurax zaraptor, oviposit a single egg on each host (solitary oviposition). Recent collections in the central United States, however, have revealed populations of Muscidifurax with gregarious oviposition. Previously, the only known gregarious Muscidifurax was the South American species Muscidifurax raptorellus, which is gregarious in Chile but solitary in Peru. We have developed species-specific molecular markers for the genus Muscidifurax by RAPD-PCR and have used these markers to identify the origin of gregariousness in North America. Banding patterns from three of four primers clearly distinguished M. raptor, M. zaraptor, and M. raptorellus, and those from the gregarious North American population most closely resembled those of South American M. raptorellus. We conclude that the appearance of gregarious oviposition in central North America resulted from the introduction of gregarious M. raptorellus, rather than a novel development of gregariousness within existing populations of M. raptor or M. zaraptor. Gregarious Muscidifurax are 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. (C) 1996 Academic Press,Inc.