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Title: The Evolution of Ovipositor Length in the Parasitic Hymenoptera and the Search for Predictability in Biological Control

item Sivinski, John
item Aluja, Martin

Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/26/2003
Publication Date: 6/26/2003
Citation: Sivinski, J.M., Aluja, M. 2003. The Evolution of Ovipositor Length in the Parasitic Hymenoptera and the Search for Predictability in Biological Control. Florida Entomologist. 86(2):143-150.

Interpretive Summary: Historically there have been many efforts by entomologists to better predict the fate of natural enemies brought into new environments for the biological control of pests. Not only would accurate predictions result in the more effective expenditure of the limited resources needed for exploration, rearing, and release, they would also minimize the risk of introducing a predator or parasitoid that attacks nontarget insects or competes with the natural enemies already present. Researchers at the Center for Medical, Agricultural, and Veterinary Entomology (Gainesville, FL) in collaboration with colleagues from the Instituto de Ecologia (Xalapa, Veracruz, Mexico) have examined how comparisons of parasitoid ovipositor lengths might help predict whether or not new species are likely to fit into groups of parasitoids already attacking a particular pest. In the case of the braconid parasitoids attacking tephritid fruit flies ( Anastrepha spp.) in Mexico, relative ovipositor lengths are not useful predictors. Until the ecological interactions among these natural enemies are better understood, it is recommended that biological control concentrate on conservation and augmentation rather than the introduction of foreign species.

Technical Abstract: Ovipositor lengths are thought to reflect the egg-laying and host-searching behaviors of parasitoids. For example, parasitoids that attack exposed foliage feeders often have short ovipositors compared to species that must penetrate a substrate to reach a host. However, the relationship between host accessability and ovipositor length is not apparent in a guild of braconids that oviposits in the larvae of frugivorous Mexican tephritids. While the longest ovipositors are up to 5X longer than the shortest, all attack roughly the same stages of their shared hosts, often in the same fruits. Nor is there any evidence that the shorter ovipositors represent a saving of material and energy that is redirected toward egg production or greater ability to disperse. It has been suggested that if the ovipositor length of an introduced parasitoid is substantially different from the ovipositors of species already present, then it is more likely to find an empty niche in its new environment, become established, and add to the control of its host. However, with the present lack of a simple explanation for the variety of ovipositor lengths within the Mexican guild it is not clear how predictive ovipositor length would be in this instance. Until the evolution and maintenance of the various lengths is better understood it may be more circumspect to practice fruit fly biological control through the conservation and augmentation of parasitoid species already present.