Niche breadth and interspecific competition between Doryctobracon crawfordi and Diachasmimorpha longicaudata (Hymenoptera: Braconidae), native and introduced parasitoids of Anastrepha spp. fruit flies (Diptera: Tephritidae)

• Competitive interactions between two species of fruit fly parasitoids were examined.
• Large niche overlap and strong competition were documented.
• The exotic Diachasmimorphalongicaudata outcompeted the native D.crawfordi.
• Simultaneous release for augmentative biological control is discouraged.

Interactions among multiple natural enemies can enhance or interfere with their impacts on host/prey populations. Such could be the case with two species of Braconidae that are currently considered for augmentative biological control of pestiferous tephritid fruit flies in Mexico: the exotic Diachasmimorpha longicaudata (Ashmead) and the native Doryctobracon crawfordi (Viereck). Since niche overlap and competition could influence the range and effectiveness of these parasitoids were they to be released together, we compared behaviors and morphologies that might influence their access to hosts. These included ovipositor length, diel pattern of oviposition, effect of host instar on development, host range, host-depth, foraging success in different sized host patches, and effects of super- and multi-parasitism. Intra- and interspecific adult interactions on host patches were also observed. There were significant overlaps in ovipositor length, diel patterns of oviposition, preferred host age, and host depth and size. D. crawfordi failed to exploit Anastrephaobliqua and Ceratitiscapitata, while D. longicaudata parasitized four tephritid species. D. longicaudata dominated D. crawfordi in multi-parasitism tests and was also better able to survive superparasitism than its competitor. Our results suggest that simultaneous augmentative release of these two species would result in substantial competition. However, because D. crawfordi is naturally found at greater densities than D. longicaudata at high elevations, perhaps because of greater tolerance for cold temperatures, releases in such areas might yield better results than releases of its otherwise superior competitor.

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