Submitted to: Florida Entomologist
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/20/2010
Publication Date: 9/1/2010
Citation: Copeland, C.S., Hoy, M.A., Jeyaprakash, A., Aluja, M., Ramirez-Romero, R., Sivinski, J.M. 2010. Genetic characteristics of bisexual and female-only populations of Odontosema anastrephae (Hymenoptera:Figitidae). Florida Entomologist. 93(3):437-443. Interpretive Summary: Fruit fly are pests of hundreds of fruits and vegetables, but may be controlled by the mass-rearing and release of large numbers of parasitoids. One objection to this practice is the relatively high cost of rearing these natural enemies. Scientists at the USDA-ARS Center for Medical, Agricultural and Veterinary Entomology in collaboration with colleagues from the University of Florida and the Instituto de Ecologia (Xalapa, Veracruz, Mexico) are investigating bacteria that change male parasitoids into females. If these infections could be introduced into rearing cultures then the cost of producing useful natural enemies (females) would be cut in half. An all-female, infected parasitoid was recently found in Mexico and the bacteria responsible for sex-changing were identified. Explorations to find additional infected species will continue and attempts will eventually be made to pass bacteria to uninfected hosts.
Technical Abstract: Odontosema anastrephae Borgmeier is a figitid parasitoid of Anastrepha fruit fly larvae infesting fallen fruit. It is of potential use in biological control as a complement to parasitoids that attack larvae infesting fruit still on the tree and to parasitoids that can only oviposit near the surface of the fruit, because Odontosema pursues larvae deep within the pulp. A newly discovered Mexican all-female (presumably thelytokous) population, provisionally referred to here as O. near anastrephae, appears to be morphologically indistinguishable from arrhenotokous individuals. Thelytokous reproduction can potentially lower costs in mass rearing facilities and increase parasitoid efficacy in the field. This is to our knowledge the first known instance of an all-female taxon of specialist parasitoids of tephritid fruit fly pests. PCR amplification and sequencing of mitochondrial (COI) and nuclear (ITS2) genes suggested that these populations are genetically distinct, but no more so than often occurs among populations within recognized species. Because Wolbachia infections can lead to thelytoky, both populations were tested for infection by PCR amplification of the wsp gene. Wolbachia was present in the thelytokous, but not the arrhenotokous, population. In addition to the description of a thelytokous population of Odontosema, this study also presents the first genetic sequence data for any members of the genus Odontosema, enabling phylogenetic comparison between Odontosema and other figitid genera and the development of methods for the identification of Odontosema species by PCR. The implications of thelytoky for a cladistic definition of speciation, especially for newly diverging populations such as these, are discussed.