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The worldwide population genetics of Harmonia axyridis: how the invasive Harlequin Ladybird invaded, and moves within, South Africa
Thesis (MSc)--Stellenbosch University, 2022.
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2022
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| _version_ | 1867613877982724096 |
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| access_status_str | Open Access |
| author | Collop, Amy |
| author2 | Karsten, Minette |
| author_browse | Collop, Amy Karsten, Minette |
| author_facet | Karsten, Minette Collop, Amy |
| author_sort | Collop, Amy |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MSc)--Stellenbosch University, 2022. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/125136 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:43:08.148Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2022 |
| publishDateRange | 2022 |
| publishDateSort | 2022 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/125136 The worldwide population genetics of Harmonia axyridis: how the invasive Harlequin Ladybird invaded, and moves within, South Africa Collop, Amy Karsten, Minette Terblanche, John S. Clusella-Trullas, Susana Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology. Ladybugs -- Geographical distribution Population genetics Biological invasions -- South Africa Introduced organisms -- Dispersal Harmonia axyridis -- South Africa UCTD Thesis (MSc)--Stellenbosch University, 2022. ENGLISH ABSTRACT: Understanding the introduction pathways used by invasive species is critical to formulate management plans and prevent new invasions. The Harlequin ladybird, Harmonia axyridis, is an invasive Coccinellidae beetle native to Asia that has become established on four continents beyond its native range. Harmonia axyridis has had several adverse impacts on native arthropod communities, is an agricultural pest, and can cause allergies in some humans. This species was first observed in South Africa in 2001 and has subsequently spread throughout most of the country and to some neighbouring countries (Lesotho and eSwatini). The worldwide invasion pathways of H. axyridis has previously been investigated where east North America was identified as an invasive bridgehead population. This describes when a single location acts as the source of colonists invading multiple new territories. However, these studies only included limited sampling within South Africa and then from samples collected more than 10 years ago (between 1998 and 2010). Using microsatellite data and comprehensive geographic coverage of international beetle samples (N=408 from 17 sample locations), with a strong focus on South African populations (N=379 from 14 sample locations), the source of colonists invading South Africa and the beetle’s movement within the country were determined. Genetic structure analyses suggest South Africa’s H. axyridis population are derived from admixture between beetles originating from eastern North America and an unsampled (not included in this study) population. The invasive population in east North America demonstrated characteristics of an invasive bridgehead scenario as it also acted as the source of colonists invading parts of South America and Europe. Admixture between two genetic groups may have increased the adaptive ability of beetles within South Africa and/or reduced the potentially negative effects of inbreeding depression and genetic bottlenecks. Along with the possibility of multiple sequential introductions (i.e. high propagule pressure) into South Africa, this may explain the high genetic diversity estimates for South African H. axyridis beetles (HE=0.582-0.625) compared to beetles from the native range (HE=0.440-0.636). Harmonia axyridis beetles appear to be frequently exchanging genetic information across South Africa, with no clear genetic structure between sampled locations (K=2). Evidence of isolation-by-distance within South Africa suggests that the genetic variation between sample locations results from the moderate accumulation of genetic differences between individuals separated by large geographic distances. Management plans would therefore have to consider H. axyridis’ high connectivity across South Africa when assessing potential control or management strategies and at what scale it should be implemented. Future studies could investigate the factors (biotic and abiotic) that may be promoting its invasiveness in South Africa and the impacts it has had on local insect biodiversity. Harmonia axyridis could also be used as a model species to investigate the potential effects genetic admixture has on adaptive ability and determine if transport hubs in east North America promoted the invasive success of the bridgehead region. AFRIKAANSE OPSOMMING: Vir die formulasie van bestuursplanne en om nuwe invalle te voorkom is dit noodsaaklik om die kolonisasieroetes wat deur indringerspesies gebruik word te verstaan. Die Harlekyn-liewenheersbesie, Harmonia axyridis, is 'n indringer Coccinellidae-kewer inheems aan Asië en is tans teenwoordig op vier kontinente buite hierdie verspreiding. Harmonia axyridis het verskeie nadelige impakte op inheemse geleedpotige gemeenskappe, is 'n landbouplaag en kan allergieë by sommige mense veroorsaak. Die besie is vir die eerste keer in 2001 in Suid-Afrika waargeneem en het daarna deur die grootste deel van die land asook na sommige buurlande (Lesotho en eSwatini) versprei. Die wêreldwye kolonisasieroete van H. axyridis is voorheen ondersoek en oos Noord-Amerika is as 'n indringerbrugbevolking geïdentifiseer. Dit is wanneer 'n enkele lokaliteit optree as die bron van koloniste wat na verskeie nuwe gebiede versprei. Hierdie vorige studies het egter slegs beperkte steekproefneming binne Suid-Afrika ingesluit en die monsters was ook meer as 10 jaar tevore (tussen 1998 en 2010) versamel. In hierdie studie het ek die bron van koloniste wat in Suid-Afrika gevestig het, sowel as die kewer se beweging binne Suid-Afrika bepaal deur gebruik te maak van mikrosatelliet data en omvattende geografiese dekking van internasionale kewermonsters (N=408 van 17 steekproeflokasies), met 'n sterk fokus op Suid-Afrikaanse populasies (N=379 van 14 steekproeflokasies). Genetiese struktuur ontledings dui daarop dat Suid-Afrika se H. axyridis-bevolking afkomstig is van vermenging tussen kewers van Oos-Noord-Amerika en 'n onbekende bevolking (nie by hierdie studie ingesluit nie). Die indringer bevolking in Oos-Noord-Amerika toon kenmerke van 'n indringerbrugbevolking, aangesien dit ook opgetree het as die bron van koloniste wat dele van Suid-Amerika en Europa binnegeval het. Vermenging tussen twee genetiese groepe het moontlik die aanpasbaarheid van kewers in Suid-Afrika verhoog en/of die potensieel negatiewe effekte van intelingsdepressie en genetiese knelpunte verminder. Saam met die moontlikheid van veelvuldige opeenvolgende kolonisasies in Suid-Afrika, kan dit die hoë genetiese diversiteit in Suid-Afrikaanse H. axyridis-kewers (HE =0.582-0.625) in vergelyking met kewers uit die inheemse verspreiding (HE = 0.440-0.636) verklaar. Harmonia axyridis kewers blyk gereeld genetiese materiaal in Suid-Afrika uit te ruil, met geen duidelike genetiese struktuur tussen lokalieite nie (K=2). Bewyse van isolasie-oor-afstand binne Suid-Afrika dui daarop dat die genetiese variasie tussen lokaliteite die gevolg is van die matige versameling van genetiese verskille tussen individue geskei deur groot geografiese afstande. Bestuursplanne sal dus H. axyridis se hoë konnektiwiteit regoor Suid-Afrika in ag moet neem wanneer potensiële beheer- of bestuurstrategieë geassesseer word, asook op watter skaal dit geïmplementeer moet word. Toekomstige studies kan die faktore (bioties en abioties) ondersoek wat die kolonisasie van H. axyridis in Suid-Afrika bevorder en die moontlike impak wat dit op plaaslike insekbiodiversiteit het. Harmonia axyridis kan ook as 'n modelspesie gebruik word om die potensiële uitwerking van genetiese vermenging op aanpasbaarheid te ondersoek en te bepaal of die hoof vervoernetwerke in Oos-Noord- Amerika die sukses van die brughoofstreek bevorder het. Masters 2022-03-08T18:15:03Z 2022-04-29T12:55:32Z 2022-03-08T18:15:03Z 2022-03-08 Thesis http://hdl.handle.net/10019.1/125136 en Stellenbosch University x, 73 pages : illustrations, maps application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Ladybugs -- Geographical distribution Population genetics Biological invasions -- South Africa Introduced organisms -- Dispersal Harmonia axyridis -- South Africa UCTD Collop, Amy The worldwide population genetics of Harmonia axyridis: how the invasive Harlequin Ladybird invaded, and moves within, South Africa |
| title | The worldwide population genetics of Harmonia axyridis: how the invasive Harlequin Ladybird invaded, and moves within, South Africa |
| title_full | The worldwide population genetics of Harmonia axyridis: how the invasive Harlequin Ladybird invaded, and moves within, South Africa |
| title_fullStr | The worldwide population genetics of Harmonia axyridis: how the invasive Harlequin Ladybird invaded, and moves within, South Africa |
| title_full_unstemmed | The worldwide population genetics of Harmonia axyridis: how the invasive Harlequin Ladybird invaded, and moves within, South Africa |
| title_short | The worldwide population genetics of Harmonia axyridis: how the invasive Harlequin Ladybird invaded, and moves within, South Africa |
| title_sort | worldwide population genetics of harmonia axyridis how the invasive harlequin ladybird invaded and moves within south africa |
| topic | Ladybugs -- Geographical distribution Population genetics Biological invasions -- South Africa Introduced organisms -- Dispersal Harmonia axyridis -- South Africa UCTD |
| url | http://hdl.handle.net/10019.1/125136 |
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