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 ga rbage. Most species of Muscidifurax, including both North American spe cies Muscidifurax raptor and Mudscidifurax zaraptor, oviposit a single egg on each host (solitary oviposition). Recent collections in the ce ntral United States, however, have revealed populations of Muscidifura x with gregarious oviposition. Previously, the only known gregarious M uscidifurax was the South American species Muscidifurax raptorellus, w hich is gregarious in Chile but solitary in Peru. We have developed sp ecies-specific molecular markers for the genus Muscidifurax by RAPD-PC R 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 f rom the gregarious North American population most closely resembled th ose of South American M. raptorellus. We conclude that the appearance of gregarious oviposition in central North America resulted from the i ntroduction of gregarious M. raptorellus, rather than a novel developm ent of gregariousness within existing populations of M. raptor or M. z araptor. Gregarious Muscidifurax are very aggressive in the laboratory and are effective biological control agents, but how they interact wi th other parasitoid species that attack dipteran pupae in the field re mains unknown. (C) 1996 Academic Press,Inc.