South American origins of Microctonus hyperodae Loan (Hymenoptera: Braconidae) established in New Zealand as defined by morphometric analysis.
Eight South American geographic populations of the thelytokous parasitoid Microctonus hyperodae were released in New Zealand in 1991 to assist in the suppression of the pasture pest Listronotus bonariensis. With one exception, parasitoids from each South American geographic population were released in equal numbers at each New Zealand release site. It was postulated that the South American geographic population(s) best suited to the conditions encountered at each New Zealand release locality would eventually become prevalent there. A morphometric analysis of adult parasitoids of known South American origins, reported previously, allowed M. hyperodae derived from west of the Andes (2 collection sites in Chile) to be distinguished from parasitoids derived from east of the Andes (3 collection sites in Argentina and one each in Brazil and Uruguay). Parasitoids derived from a fourth site in Argentina (S. C. de Bariloche) could not be clearly discriminated from either the 'east of the Andes' or 'west of the Andes' categories. A morphometric analysis of M. hyperodae adults collected from five of the New Zealand release sites from 1992-94 is presented in this contribution. The analysis indicated that parasitoids derived from east of the Andes were significantly more prevalent than expected. The possible reasons for the initial success in New Zealand of one or more east of the Andes populations include the greater fecundity of M. hyperodae collected in Uruguay and the likelihood that M. hyperodae from east of the Andes co-evolved more recently with the stock from which New Zealand's L. bonariensis was founded.