Genetic diversity in a commercial black soldier fly, Hermetia illucens (Diptera: Stratiomydiae), population
| dc.contributor.advisor | Rhode, Clint | en_ZA |
| dc.contributor.advisor | Bester-van der Merwe, Aletta Elizabeth | en_ZA |
| dc.contributor.author | Badenhorst, Rozane | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of AgriSciences. Dept. of Genetics. | en_ZA |
| dc.date.accessioned | 2017-02-20T15:14:06Z | |
| dc.date.accessioned | 2017-03-29T12:17:47Z | |
| dc.date.available | 2017-02-20T15:14:06Z | |
| dc.date.available | 2017-03-29T12:17:47Z | |
| dc.date.issued | 2017-03 | |
| dc.description | Thesis (MSc)--Stellenbosch University, 2017. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: The applications of black soldier fly (BSF), Hermetia illucens, as a first-generation biotechnology address two global problems - the pressure on food security arising from unsustainable food production practices which exhausting fisheries resources by fishmeal production; and the vast accumulation of organic waste. Understanding the phenotypic and genetic changes experienced when establishing colonies of H. illucens is important for successfully establishing new colonies and managing already existing mass-rearing facilities. The aim of this study was to assess the changes in genetic diversity coupled with the phenotypic changes associated with colony establishment. Commercially-relevant phenotypic parameters were measured; including pupae weight, percentage eclosion, post-mating longevity, hatchability and egg clutch sizes over six successive generations (F0-F5). Hatchability, clutch size and pupae weight increased from F1 to F4, but a decline was apparent from F3 to F4. Post-mating longevity dramatically decreased from F1 (100%) to F4 (33%) and the F5 generation did not develop beyond the pre-pupae stage resulting in colony-collapse. The phenotypic changes can be explained by a combination of environmental, physiological and genetic effects. The positive trends observed during earlier generations (F0-F1) may reflect the population reacting to relaxed natural selection. While, at the end of the study period (F3-F5), natural selection in captivity resulted in a decrease in phenotypic variables. The colony collapse in the final generation, despite constant environmental conditions, possibly reflects the deleterious effects of random genetic drift and inbreeding depression. For the assessment of the genetic processes which may have resulted in the observed phenotypic changes, ten microsatellite markers were developed and characterised. Marker utility was tested on 37 wild individuals using three multiplex-PCR reactions. The number of alleles for each locus ranged from 4 to 21. Polymorphism information content ranged from 0.52 to 0.90, while observed and expected heterozygosity ranged from 0.30-0.65 and 0.55-0.91, respectively. Furthermore, the markers are useful in individual identification (PID = 1.2x10-11and PIDsib = 1.1x10-4) and parentage analysis (P1=1; P2 = 1). The markers proved useful in the assessment of genetic diversity and were used to understand the genetic mechanisms underlying phenotypic trends previously described. The assessment of genetic diversity revealed significant population differentiation as described by FST estimates across the experimental generations (P < 0.01), accompanied by a significant loss of genetic diversity. The final generation indicated a significantly higher number of private alleles and significantly lower observed heterozygosity in comparison to preceding generations (P < 0.05). Population bottlenecks and inbreeding were evident in the estimation of effective population size (Ne) and relatedness. Phenotypic parameters which significantly correlated (Pearson’s r) to changes in genetic diversity were pupation (%), clutch size, pupae weight and female post-mating longevity (P < 0.05). Results indicate the effects of inbreeding depression and genetic drift were amplified by a decrease in effective population size and increased relatedness amongst individuals. In summation, the assessment of changes in phenotypic measurements and genetic diversity during the establishment of an H. illucens colony, gave valuable insight into the genetic processes which occur during colony establishment; and are applicable to colony establishment and the management of already existing colonies. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Die toepassings van Hermetia illucens as 'n eerste-generasie biotegnologie is daarop gemik om twee probleme op te los; die druk op voedselsekerheid wat voortspruit uit onvolhoubare voedselproduksiepraktyke (bv. die uitputting van visseryhulpbronne om vismeel te produseer) en die opeenhoping van organiese afval. Dit is van waardevolle belang om die verandering van kommersiële-relevante fenotipes en mate van genetiese diversiteit tydens kolonie-stigting in H. illucens te verstaan en toe te pas wanneer nuwe kolonies gestig word of om reeds bestaande kolonies te bestuur. Die doel van hierdie studie was om die fenotipiese en genetiese veranderinge tydens kolonie-stigting te bestudeer. Kommersiële-relevante fenotipiese mates soos aanwysers van kolonie-fiksheid, -vrugbaarheid en -gesondheid was gemeet, insluitende papie-gewig, langslewendheid, uitbroeivermoë van eiers en eier-broeiselgroottes. Hierdie eienskappe was gemeet oor ses opeenvolgende geslagte (F0-F5). Uitbroeivermoë, eierbroeiselgroottes en papiegewig het toegeneem vanaf F1 tot F4, maar 'n afname word waargeneem vanaf F3 tot F4 vir al drie veranderlikes. Die langslewendheid van wyfies het ook dramaties afgeneem van F1 (100%) tot F4 (33%) en die F5 geslag het nie verder as die voor-papiese stadium ontwikkel nie, wat gelei het tot die ineenstorting van die kolonie. Die tendense in fenotipiese veranderinge kan verklaar word deur 'n kombinasie van omgewings-, fisiologiese- en genetiese effekte. Die positiewe tendense tydens vroeëre geslagte (F0-F1) kan toegeskryf word aan geleidelike aanpassing tot die kunsmatige omgewing. Daarteen, kan die afname in fenotipiese veranderlikes tydens die einde van die studietydperk (F3-F5) veroorsaak word deur die kolonie-onderhoudstrategie. Die ineenstorting van die kolonie in die sesde generasie, ten spyte van voortdurende konstante omgewingstoestande, verwys na die nadelige gevolge van genetiese drywing en gevolglike intelingsdepressie. Die volgende doelwit was om gereedskap te ontwikkelvir die ondersoek van genetiese verandering tydens massa-grootmaak. 'n Paneel van tien mikrosatelliet merkers was ontwikkel en gekarakteriseer. Die toepassing van mikrosatelliet genotipering was getoets in 37 wilde individue gdeur middel van drie multipleks-Polymerase Ketting Reaksie (PKR)-reaksies. Die aantal allele vir elke lokus het gewissel van 4 tot 21. Polimorfisme inligtinginhoud het gewissel van 0.52 tot 0.90, terwyl waargeneme en verwagte heterosigositeit gewissel het tussen 0.30-0.65 en 0.55-0.91, onderskeidelik. Die merkers was nuttig vir individuele identifikasie (PID = 1.2x10-11 en PIDsib = 1.1x10-4) asook ouerskap-analise (P1 = 1; P2 = 1). Die merkers wat hier aangebied word, sal nuttig wees vir verskeie toepassings, insluitend die beoordeling van genetiese diversiteit tydens die stigting van H. illucens kolonies. Die merkers was in die huidige studie gebruik om die geniese meganismes wat fenotipiese tendense dryf, te ondersoek. Betekenisvolle populasie-differensiasie soos beskryf deur FST skattings oor die eksperimentele geslagte (P < 0.01) was waargeneem, tesame met 'n beduidende verlies van alleliese rykheid en heterosigositeit. Die finale geslag het ook 'n aansienlike groter aantal private allele en laer heterosigositeit getoon, in vergelyking met vorige geslagte (P < 0.05). Die berekening van effektiewe populasiegrootte (Ne) en ondersoek na verwantskap dui op ʼn populasie bottelnek en inteling. Fenotipiese mates wat betekenisvolle korrelasier (Pearson se r) met veranderinge in genetiese diversiteit getoon het, was pupasie (%), eier-broeiselgrootte, papie-gewig en langslewendheid van wyfies na paring (P < 0.05). Die resultate dui aan dat die gevolge van intelingsdepressie en genetiese drywing versterk is deur 'n toenemende verwantskap tussen individue en klein effektiewe populasiegrootte. Ten slotte, die bevindinge van hierdie studie, sal nuttig wees in die toekomstige vestiging van H. illucens kolonies, asook vir die bestuur van reeds bestaande kolonies. | af_ZA |
| dc.format.extent | 134 pages : illustrations | |
| dc.identifier.uri | http://hdl.handle.net/10019.1/101182 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject | Black soldier fly, Hermetia illucens (Diptera: Stratiomydiae) | en_ZA |
| dc.subject | Black soldier fly -- Population genetics | en_ZA |
| dc.subject | Black soldier fly -- Genetic diversity | en_ZA |
| dc.subject | Hermetia illucens -- Colony establishment | en_ZA |
| dc.subject | UCTD | en_ZA |
| dc.title | Genetic diversity in a commercial black soldier fly, Hermetia illucens (Diptera: Stratiomydiae), population | en_ZA |
| dc.type | Thesis | en_ZA |