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The gigas effect: A reliable predictor of ploidy? Case studies in Oxalis
Thesis (MSc)--Stellenbosch University, 2021.
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| Format: | Thesis |
| Language: | en_ZA en_ZA |
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Stellenbosch : Stellenbosch University
2021
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| _version_ | 1867614097977114624 |
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| access_status_str | Open Access |
| author | Becker, Frederik Willem |
| author2 | Dreyer, L. L. |
| author_browse | Becker, Frederik Willem Dreyer, L. L. |
| author_facet | Dreyer, L. L. Becker, Frederik Willem |
| author_sort | Becker, Frederik Willem |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MSc)--Stellenbosch University, 2021. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/110095 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA en_ZA |
| last_indexed | 2026-06-10T12:46:38.139Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2021 |
| publishDateRange | 2021 |
| publishDateSort | 2021 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/110095 The gigas effect: A reliable predictor of ploidy? Case studies in Oxalis Becker, Frederik Willem Dreyer, L. L. Oberlander, Kenneth C. Travnicek, Pavel Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology. Gigas Polyploidy -- Evolution Oxalis -- Phylogeny Whole genome duplication UCTD Thesis (MSc)--Stellenbosch University, 2021. ENGLISH ABSTRACT: Whole Genome Duplication (WGD), or polyploidy is an important evolutionary process, but literature is divided over its long-term evolutionary potential to generate diversity and lead to lineage divergence. WGD often causes major phenotypic changes in polyploids, of which the most prominent is the Gigas effect. The Gigas effect refers to the enlargement of plant cells due to their increased amount of DNA, causing plant organs to enlarge as well. This enlargement has been associated with fitness advantages in polyploids, enabling them to successfully establish and persist, eventually causing speciation. Using Oxalis as a study system, I examine whether Oxalis polyploids exhibit the Gigas effect using 24 species across the genus from the Oxalis living research collection at the Stellenbosch University Botanical Gardens, Stellenbosch. Given that the Gigas effect also holds great potential to increase a polyploid’s competitive ability, and as a result, invasiveness, I also tested for the Gigas effect in 15 traits and WGD-associated increased self-fertilization and bulbil production in the weedy species O. purpurea. Using known correlates of the Gigas effect (stomata length, epidermal cell area and pollen grain diameter) I show that Oxalis polyploids display a very inconsistent and small Gigas effect – contrary to that predicted from the literature. With extensive sampling across 20 populations of O. purpurea in its native range, I show a similar pattern for stomata length, pollen grain diameter and epidermal cell area in this species. In addition, I found a large decrease in effect size of polyploidy and substantial variation across traits in 12 further leaf and flower traits studied. O. purpurea showed very high levels of self-incompatibility among both diploids and polyploids, but polyploids produced significantly more and heavier bulbils than diploids. Overall, these results revealed a very small and inconsistent Gigas effect among Oxalis polyploids. There is, however, an association between polyploidy and invasive potential, using bulbil production as a proxy for invasiveness. Polyploid success and persistence in Oxalis could be as a result of a temporary initial Gigas effect upon formation, which later becomes diluted through local adaptation. AFRIKAANSE OPSOMMING: Heel Genoom Duplisering (HGD), of polyploidie, is ‘n belangrike evolusionêre proses, maar die literatuur is verdeeld oor die lang termyn evolusionêre potensiaal van HGD om spesies te vorm. HGD veroorsaak opvallende veranderinge in fenotipiese eienskappe waarvan die mees prominente effek die “Gigas” effek is. Die “Gigas” effek verwys na die vergroting van plant selle as gevolg van meer DNA en, gevolglik, ook groter organe. Hierdie vergroting het ‘n sterk verwantskap met verhoogde fiksheid in polyploiëde wat lei daarnatoe dat hulle gevestigde bevolkings vorm en aanhou voortleef. Dit kan gevolglik lei daarnatoe dat polyploiëde nuwe spesies kan vorm. Ek ondersoek die vraag of polyploiëde betroubaar die “Gigas” effek toon deur gebruik te maak van 24 spesies in die Oxalis genus van die Oxalis lewende versameling in die Stellenbosch Universiteit Botaniese Tuine. Gegewe die fikdheids voordele van die “Gigas” effek, is daar ook dikwels eienskappe te vind wat sterk verband hou met indringende eienskappe van plante. Daarom toets ek ook vir die “Gigas” effek in 15 eienskappe en HGD-verwante afbraak in self-onversoenbare genetiese faktore in voortplanting en klonale-bol produksie in die onkruidagtige spesie, Oxalis purpurea. Deur gebruik te maak van bekende korrelerende eienskappe van die “Gigas” effek (huidmodjie lengte, epidermale sel oppervlak en stuifmeel korrel diameter) wys ek dat Oxalis polyploiëde ‘n baie klein en strydige “Gigas” effek het, teenstrydig met die voorspellings van die literatuur. Met ‘n monsterneming van 20 bevolkings van O. purpurea wys ek ook dieselfde patroon in hierdie eienskappe. Verder vind ek ook ‘n geweldige afname in effek-grootte van polyploiëde en aansienlik meer variasie in 12 blaar en blom kemerke waar ek hierdie effek ondersoek het. O. purpurea wys baie sterk self-onversoenbaarheid vir beide diploiëde en polyploiëde, maar polyploiëde vervaardig meer en swaarder kloon-bolletjies teennoor diploiëde. Die uitslag van hierdie studies wys dat daar ‘n baie klein en strydige “Gigas” effek in Oxalis polyploiëde voorkom. Daar is wel ‘n verwantskap tussen polyploidie en indringendheid in O. purpurea deur gebruik te maak van klonale-bol produksie as ‘n toon-kenmerk van indringendheid. Die algehele sukses en voortbestaan van polyploiëde in Oxalis mag die uitkoms wees van ‘n tydelik “Gigas” effek onmiddelik na vorming, maar die effek raak later verlore deur plaaslike aanpassing oor geslagte. Masters 2021-02-26T16:30:21Z 2021-04-21T14:40:09Z 2021-02-26T16:30:21Z 2021-04-21T14:40:09Z 2021-03 Thesis http://hdl.handle.net/10019.1/110095 en_ZA en_ZA Stellenbosch University ix, 81 pages application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Gigas Polyploidy -- Evolution Oxalis -- Phylogeny Whole genome duplication UCTD Becker, Frederik Willem The gigas effect: A reliable predictor of ploidy? Case studies in Oxalis |
| title | The gigas effect: A reliable predictor of ploidy? Case studies in Oxalis |
| title_full | The gigas effect: A reliable predictor of ploidy? Case studies in Oxalis |
| title_fullStr | The gigas effect: A reliable predictor of ploidy? Case studies in Oxalis |
| title_full_unstemmed | The gigas effect: A reliable predictor of ploidy? Case studies in Oxalis |
| title_short | The gigas effect: A reliable predictor of ploidy? Case studies in Oxalis |
| title_sort | gigas effect a reliable predictor of ploidy case studies in oxalis |
| topic | Gigas Polyploidy -- Evolution Oxalis -- Phylogeny Whole genome duplication UCTD |
| url | http://hdl.handle.net/10019.1/110095 |
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