Submitted to: Biological Journal of the Linnean Society, London
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/9/2008
Publication Date: 4/1/2009
Citation: Caceres, C., Segura, D.F., Vera, T.M., Wornoayporn, V., Cladera, J.L., Teal, P.E., Sapountzis, P., Bourtzis, K., Zacharopouloul, A., Robinson, A.S. 2009. Incipient speciation revealed in Anastrepha fraterculus (Diptera; Tephritidae) by studies on mating compatibility, sex pheromones, hybridisation and cytology. Biological Journal of the Linnean Society. 97:152-165. Interpretive Summary: The South American fruit fly is a quarantine pest of significant importance to a wide variety of orchard and vegetable crops. There is considerable question about the species status of this pest because flies from different areas in the range which extends from the Southern US to Southern South America are not interbreeding. Because of the economic importance of the pest it is critical to understand if a single the fly is indeed a single species or a complex of related species. Scientist at the FAO/IAEA Programme of Nuclear Techniques in Food and Agriculture, Austria, Instituto de Genética , Argentina, Estación Experimental Agroindustrial Obispo Colombres, Argentina, Center for Medical, Agricultural, and Veterinary Entomology, USDA-ARS, Florida, Department of Environmental and Natural Resources Management, University of Ioannina, Greece and Department of Biology, University of Patras, Greece conducted a wide variety of studies on strains of the South American fruit fly originating from peru and Argentina and discovered that the two strains had distinctly different genetics, physiology, pheromone communication systems, behavior and exhibited essentially complete reproductive isolation. As a consequence these two strains fit the criteria for individual species status. This indicates that the South American fruit fly is indeed a species complex.
Technical Abstract: It is suggested that the nominal species Anastrepha fraterculus is a species complex and previous studies showed high levels of pre-zygotic isolation between two laboratory strains from Argentina and Peru. To further analyze this observation, experiments were carried out on the same populations and on their reciprocal hybrids, including pre- and post-zygotic isolation studies, pheromone analysis and mitotic and polytene chromosome analysis. A high level of pre-zygotic isolation had been maintained between the parental strains despite three years of laboratory rearing. The level of pre-zygotic isolation was reduced in matings with hybrids. There were also differences in other components of mating behavior. There were quantitative and qualitative differences in the sex pheromone of the two strains with the hybrids producing a mixture. The pre-zygotic isolation barriers were complemented by high levels of post-zygotic inviability and sex ratio distortion, probably not due to Wolbachia although there was evidence of some cytoplasmic factor involved in sex ratio distortion. Analysis of polytene chromosomes revealed a high level of asynapsis in the hybrids together with karyotypic differences between the parental strains. The combined results of this study would indicate that these two strains belong to different sub-species within the A. fraterculus complex.