Species identification, lifestyles and mitogenomics of the elusive wasp assemblage associated with wild and cultivated olives in the Western Cape

Powell, Chante Melissa (2019-12)

Thesis (MScAgric)--Stellenbosch University, 2019

Thesis

ENGLISH ABSTRACT: While the international olive industry is greatly affected by the olive fruit fly (Bactrocera oleae), South African commercial crops are marginally affected. The rich assemblage of native parasitoid wasps found in the region may contribute to maintain B. oleae populations at low levels and has potential applications in biocontrol. Furthermore, agricultural losses in the Western Cape province are mainly due to the activity of olive seed wasps (OSW) associated with premature fruit drop; however, the status of several species as phytophagous, parasitoid and hyperparasitoid remains uncertain. Moreover, the genus Psyttalia (Braconidae: Opiinae) includes parasitoid species with potential for biocontrol of fruit-infesting tephritid pests such as B. oleae. In addition to the native Mediterranean tephritid parasitoid, Psyttalia concolor, two sub-Saharan parasitoid species; Psyttalia humilis and Psyttalia lounsburyi, are of particular interest as they can be utilized in exotic biocontrol applications of B. oleae. The aim of this study was to generate a comprehensive catalogue of the entomofauna associated with olive fruit by identifying all species affecting the fruit, confirming the status of putative olive seed wasps as phytophagous and contributing to the phylogeny of the family Braconidae. The comprehensive survey combined morphological and DNA-based methods in which four Braconidae species and six Chalcidoidea species were identified. Furthermore, morphological identifications were congruent with DNA data for all species, as neighbour-joining and maximum-likelihood trees correctly placed all sequences either at the genus or species level, depending on the available taxa coverage, and low genetic distances strongly supported conspecificity. These results can be used for early DNA-based species identification of wasp larvae in olives, and to further investigate their biology and ecology. In addition, a DNA-based identification tool was developed to identify immature specimens collected from olive seeds and for the simultaneous detection of five putative chalcid OSW (Eupelmus spermophilus, Eurytoma oleae, Eurytoma varicolor, Neochrysocharis formosus and Sycophila aethiopica). Eupelmus spermophilus, E. oleae and S. aethiopica were identified in olive seeds, and confirmed as phytophagous. This method can be used as a diagnostic tool for pest detection at an early stage of infestation when morphological identification is not feasible. Furthermore, it can provide new biological insights into the lifestyles of these elusive species. The near-complete mitochondrial genomes of Psyttalia concolor, Psyttalia humilis, and Psyttalia lounsburyi, three important parasitoids, were recovered using Sanger sequencing and next-generation sequencing. The three Psyttalia species had a particular gene arrangement involving tRNAs, different from all other Braconidae. Gene rearrangements varied substantially among Braconidae, potentially being useful for clarification of the complex phylogeny of the group. Phylogenetic reconstruction within the family Braconidae confirmed the division of two major lineages of cyclostome and non-cyclostome braconids. Furthermore, our analyses corroborated subfamily Aphidiinae as a sister group to the cyclostome braconids, a group previously thought to be a separate family (Aphidiidae). Overall, this study advances the knowledge of insects associated with olive fruit in the Western Cape, the status of phytophagous OSW, which was previously undetermined, and contributes to the phylogeny and understanding of gene rearrangement in the family Braconidae.

AFRIKAANSE OPSOMMING: Terwyl die internasionale olyf-industrie sterk beïnvloed word deur die olyf-vrugtevlieg (Bactrocera oleae), word die Suid-Afrikaanse kommersiële bedryf gering geraak deur die pesinsek. Die diverse samestelling van inheemse parasitiese wespe wat in die streek voorkom, mag bydra tot die beheer van B. oleae-populasies en vlieg-getalle laag hou en het dus potensiële toepassings in biobeheer. Verder is landbouverliese in die Wes-Kaap provinsie hoofsaaklik te wyte aan die aktiwiteit van olyfsaadwespe (OSW) wat verband hou met voortydige vrugval. Die status van verskillende olyfsaadwespe spesies as fitofagus, parasitoïed en hiperparasitoïed bly egter onseker. Die genus Psyttalia (Braconidae: Opiinae) bevat ook parasitiese spesies met die potensiaal vir biobeheer van vrugtebesmette tephritiede soos B. oleae. Benewens die inheemse Mediterreense tephritid-parasitoïed, is Psyttalia concolor, twee sub-Sahara-parasitoid-spesies; Psyttalia humilis en Psyttalia lounsburyi van besondere belang, aangesien dit gebruik kan word in eksotiese bio-beheertoepassings van B. oleae. Die doel van hierdie studie was om 'n omvattende katalogus van die entomofauna geassosieer met olyfvrugte saam te stel, deur spesies wat die vrug beïnvloed te identifiseer; om die vermeende status van die olyfsaadwesp as fitofagus te bevestig; en by te dra tot die filogenie van die familie Braconidae. Die uitgebreide opname het morfologiese en DNS-gebaseerde metodes gekombineer waarin vier Braconidae-spesies en ses Chalcidoidea-spesies eïdentifiseer is. Verder was morfologiese identifikasies ooreenstemmend met DNS-data vir alle spesies, met “neighbour-joining” en “maximum-likelihood” bome wat DNS volgordes in die korrekte genus- of spesies-kategorie geplaas het, afhangend van die beskikbare taxa-dekking, en genetiese afstande ondersteun ook die gevolgtrekking. Hierdie resultate kan gebruik word om vroeë DNS-gebaseerde spesie identifikasie van wesplarwes in olywe te doen, en om hul biologie en ekologie verder te ondersoek. Daarbenewens, is 'n DNS-gebaseerde identifikasiehulpmiddel ontwikkel om onvolwasse eksemplare te identifiseer wat versamel is uit olyfsade vir vyf vermeende chalcied OSW (Eupelmus spermophilus, Eurytoma oleae, Eurytoma varicolor, Neochrysocharis formosus en Sycophila aethiopica). Eupelmus spermophilus, E. oleae en S. aethiopica is in olyfsade geïdentifiseer en as fitofagus bevestig. Hierdie metode kan gebruik word as 'n diagnostiese hulpmiddel vir die opsporing van plae in 'n vroeë stadium van infestasie wanneer morfologiese identifikasie nie haalbaar is nie. Verder bied dit nuwe biologiese insigte oor die lewensstyle van hierdie ontwykende spesies. Die byna volledige mitochondriale genoom van Psyttalia concolor, Psyttalia humilis, en Psyttalia lounsburyi, drie belangrike parasitoïede, is met behulp van die Sanger en volgende generasie volgordebepaling bepaal. Die drie Psyttalia-spesies het 'n spesifieke gene-rangskikking gehad wat tRNA's behels, wat anders as alle ander Braconidae is. Geenherrangskikking wissel aansienlik onder Braconidae, wat nuttig kan wees om die komplekse filogenie van die groep te ontbloot. Filogenetiese rekonstruksie binne die familie Braconidae het die monofilie van twee hoofstamlyne van siklostoom- en nie-siklostoombrakoniede bevestig. Verder het die ontleding die subfamilie Aphidiinae bevestig as 'n sustergroep vir die siklostome-braconiede, wat voorheen as 'n afsonderlike familie (Aphidiidae) beskou was. In die algemeen bevorder hierdie studie die kennis van insekte wat in die Wes-Kaap geassosieer word met olyfvrugte, die status van fitofagiese OSW, wat voorheen onbepaald was, en dra dit by tot die filogenie en die begrip van geen-herrangskikking in die familie Braconidae.

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