Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 28, 2010
Publication Date: November 1, 2010
Citation: Shapiro, J.P., Shirk, P.D., Kelley, K., Lewis, T.M., Horton, D.R. 2010. Identity of two sympatric species of Orius (Heteroptera: Anthocoridae). Journal of Insect Science. 10:189. Interpretive Summary: Two species of closely related predatory minute pirate bugs co-exist on an organic farm in North Florida. These predators are integral to the balance in an agro-ecosystem, and they play key roles in managing pest populations. Scientists at the USDA ARS, Center from Medical, Agricultural and Veterinary Entomology, Insect Behavior and Biocontrol Research Unit have examined the species identity of the two pirate bugs, Orius insidiosus and Orius pumilio to understand their filling a similar ecological niche. The ability to interbreed, the structures of their genitalia and their genetic relatedness were examined to determine their identities and they were found to be two species. This information will facilitate the conservation of these useful and critical beneficial insects for the control of damaging thrips and whitefly pests. It will also be employed in commercial rearing facilities that provide these predators to establish or augment greenhouse or field Orius populations.
Technical Abstract: The two minute pirate bugs, Orius insidiosus (Say) (Heteroptera: Anthocoridae) and Orius pumilio (Champion) (Heteroptera: Anthocoridae), are closely related and sympatric in north Florida. Interspecific matings between the two species did not result in viable progeny. Although the morphological structures of the male parameres in the two species were similar, the cone in O. pumilio was much broader with a greater spiral twist, and the flagellum was longer than in O. insidiosus. Correspondingly, there were differences in the morphology of the copulatory tubes of the females of the two species. In O. insidiosus, the organ was somewhat longer than in O. pumilio and oriented parallel to the abdominal midline, while the copulatory tube in O. pumilio tilted slightly towards the midline. Additionally, the copulatory tube for O. pumilio included a sclerotized basal mound that was not present in O. insidiosus. These morphological features suggest that successful copulation between these species may be quite difficult. In contrast to conspecific matings, interspecific matings resulted in few or no eggs laid over a period of 2 weeks. Comparison of the 18S ribosomal gene internal transcribed spacer 1 (ITS-1) sequences between the two species demonstrated only 91% homology. When yolk protein contents were examined to determine whether reproductive physiology had shifted to full egg production, interspecifically mated females contained amounts of yolk protein comparable to fed/unmated females, less than 10% of the yolk protein previously found in fed/conspecifically mated females. These findings together demonstrate that O. insidiosus and O. pumilio are indeed two separate species. However, their geographic coexistence suggests that they represent an example of sympatric divergent speciation.