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Does parasitoid attack strategy influence host specialization? A test with North American Braconid parasitoids.
Althoff, David*,1, 1 Vanderbilt University, Nashville, TN
ABSTRACT- Parasitoids are one of the most species-rich groups of organisms on earth, second only to phytophagous insects. To help understand the ecology and evolution of this immense diversity, parasitoids are usually divided into categories associated with attack strategy and location of larval development. For example, koinobiont endoparasitoids temporarily paralyze their hosts, lay eggs within the host′s body, and the larvae develop internally while the host continues to grow. Idiobiont ectoparasitoids usually permanently paralyze their hosts, lay eggs on the surface of the host′s body, and the larvae develop externally. Koinobiont parasitoids in general (regardless of endo or ecto larval development) are hypothesized to have a restricted host range compared to idiobionts because the larvae must contend with functioning host defenses. Data from parasitoid communities attacking leafmining Lepidoptera in the United Kingdom and forest Lepidoptera in Canada support this hypothesis. To test the overall generality of this dichotomy in attack strategy and host ranges, I compared the number of host families attacked by koinobiont and idiobiont parasitoid genera of the family Braconidae (Hymenoptera) in North America. Contrary to expectations, there was no difference between the host ranges of koinobiont and idiobiont genera. Koinobiont genera attacked 2.70 host families on average and idiobiont genera attacked 3.11 families on average. Although potentially biased by the as yet unresolved taxonomy of braconid parasitoid genera, this study calls into question the utility of the koinobiont/idiobiont dichotomy with respect to predicting host specialization in parasitoids.
KEY WORDS: host range, specialization, attack strategy, Braconidae