Barcoding of parasitoid wasps (Braconidae and Chalcidoidea) associated with wild and cultivated olives in the Western Cape of South Africa

Abstract

Wild and cultivated olives harbor and share a diversity of insects, some of which are considered agricultural pests, such as the olive fruit fly. The assemblage of olive-associated parasitoids and seed wasps is rich and specialized in sub-Saharan Africa, with native species possibly coevolving with their hosts. Although historical entomological surveys reported on the diversity of olive wasp species in the Western Cape Province of South Africa, no comprehensive study has been performed in the region in the molecular era. In this study, a dual approach combining morphological and DNA-based methods was used for the identification of adult specimens reared from olive fruits. Four species of Braconidae and six species of Chalcidoidea were identified, and DNA barcoding methodologies were used to investigate conspecificity among individuals, based on randomly selected representative specimens. Morphological identifications were congruent with DNA data, as NJ and ML trees correctly placed the sequences for each species either at the genus or species level, depending on the available taxa coverage, and genetic distances strongly supported conspecificity. No clear evidence of cryptic diversity was found. Overall seed infestation and parasitism rates were higher in wild olives compared to cultivated olives, and highest for Eupelmus spermophilus and Utetes africanus. These results can be used for early DNA-based detection of wasp larvae in olives and to further investigate the biology and ecology of these species.Résumé : Les olives sauvages et cultivées abritent et partagent une grande diversité d'insectes, dont certains sont considérés comme des ravageurs, comme la mouche de l'olive. Il existe une riche diversité de parasitoïdes et de guêpes séminivores spécialisés associés aux oliviers en Afrique subsaharienne, dont plusieurs espèces indigènes qui auraient co-évolué avec leurs hôtes. Bien que des enquêtes entomologiques historiques aient rapporté la diversité des guêpes de l'olive dans la province du Cap-Occidental en Afrique du Sud, aucune étude approfondie n'a été réalisée dans cette région depuis l'avènement de méthodes moléculaires. Dans ce travail, une approche double combinant des méthodes morphologiques et basées sur l'ADN ont été employées pour identifier des spécimens adultes élevés sur des olives. Quatre espèces de Braconidae et six espèces de Chalcidoidea ont été identifiées sur la base de la morphologie et des méthodes de codage à barres de l'ADN ont été employées pour étudier la conspécificité chez des individus choisis au hasard parmi des spécimens représentatifs. Les identifications morphologiques étaient en accord avec les données moléculaires car les arbres NJ et ML ont correctement placé les séquences de chacune des espèces, soit en fonction du genre ou de l'espèce selon la couverture des taxons, et les distances génétiques ont fortement supporté la conspécificité. Aucune évidence claire de diversité cryptique n'a été trouvée. Globalement, les niveaux d'infestation des graines et les taux de parasitisme...

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