Multivariate Assessment of Inter- and Intraspecific Variation in Performance Criteria of Several Pea Aphid Parasites (Hymenoptera: Aphidiidae)

Author： KAMBHAMPATI S. MACKAUER M.

Publisher： Entomological Society of America

ISSN： 1938-2901

Source： Annals of the Entomological Society of America, Vol.82, Iss.3, 1989-05, pp. : 314-324

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Abstract

Nine North American populations of Aphidius ervi Haliday, A. pisivorus Smith, A. smithi Sharma and Subba Rao, and Praon pequodorum Viereck from three locations (Chilliwack and Kamloops, B. C, and Sussex, N.J.) were examined under controlled laboratory conditions. The A. smithi (Kamloops) population had the highest average fecundity (735 eggs per female) and the highest intrinsic rate of increase (r_m = 0.487), A. ervi (Kamloops) the lowest average fecundity (284 eggs), and P. pequodorum (Sussex) the lowest rate of increase (r_m = 0.301). Thermal requirements for development were lower for Aphidius species than for P. pequodorum, with the exception of P. pequodorum (Sussex), which had a very long time-to-adult but a low temperature threshold. Multiple discriminant analysis based on eight performance variables made possible the complete separation of Aphidius and Praon populations into distinct groups. The Mahalanobis generalized distances between populations of recently introduced species (A. ervi and A. smithi) exceeded the distances between populations of the indigenous P. pequodorum, a fact indicating differences in divergence levels. It is suggested that the greater divergence levels among introduced species indicate possible founder effects during the sampling and colonization period. These findings are interpreted with regard to the recent decline and near extinction of A. smithi and its replacement by A. ervi in North America. The usefulness of parasite performance attributes as predictors of long-term establishment is discussed.