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Pollinator-mediated floral diversication of annual dimorphotheca daisies in the Cape Floristic Region
Thesis (MSc)--Stellenbosch University, 2024.
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867613930945249280 |
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| access_status_str | Open Access |
| author | Engelen, Arjan |
| author2 | Ellis, Allan G. |
| author_browse | Ellis, Allan G. Engelen, Arjan |
| author_facet | Ellis, Allan G. Engelen, Arjan |
| author_sort | Engelen, Arjan |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MSc)--Stellenbosch University, 2024. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/131652 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:43:58.501Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/131652 Pollinator-mediated floral diversication of annual dimorphotheca daisies in the Cape Floristic Region Engelen, Arjan Ellis, Allan G. Stellenbosch University. Faculty of Science. Dept. of Botany & Zoology. Pollinators -- South Africa -- Greater Cape Floristic Region Animal-plant relationships Plants -- Variation -- Genetics Biogeography Dimorphotheca daisies -- Phylogeny UCTD Thesis (MSc)--Stellenbosch University, 2024. ENGLISH ABSTRACT: Local adaptation to geographically variable pollinator fauna plays an important role in angiosperm speciation within the Greater Cape Floristic Region (GCFR). While the Orchidaceae and Iridaceae have received extensive study in this field, less attention has been given to generalist lineages such as the Asteraceae, despite evidence of spatially structured floral trait variation underlain by pollinator-mediated selection gradients. Moreover, the prevailing theory of pollinator-driven divergence emphasize shifts in the fundamental pollination niche through pollinator distributional limits, yet many studies focus solely on the realized pollination niche, potentially overlooking the influence of other factors like spatial variation in the plant community context. This thesis explores spatial variation in pollinator availability and use as drivers of floral divergence in Dimorphotheca pluvialis-sinuata, an annual daisy species complex native to the GCFR, focusing on pollination generalist populations in the complex’s south-western distribution. Chapter 2 characterizes floral variation, maps its spatial structure, and assesses its genetic basis through a common garden experiment. Multivariate analyses classify the floral variation into three discrete morphotypes based on ray floret colour patterns and disc floret appendage dimensions. These traits remain distinct across growth environments, indicating evolutionary divergence rather than phenotypic plasticity. Spatial analysis reveals an allopatric distribution of morphotypes with minimal trait introgression, suggesting geographic isolation as pivotal in maintaining the spatially discrete variation in the system. Chapter 3 examines pollinator mosaics considering both pollinator use and availability, tests for local adaptation to visitor visual preferences, and evaluates the role of ray colour and disc morphology in the ethological isolation of morphotypes. All three morphotypes attract a rich insect community composed of the same set of dominant visitors, with limited evidence for the influence of trait filtering and the plant community context on differences in the use of these visitors between morphotypes. Despite this, an essentially qualitative mosaic composed of unique and highly effective pollinator species was available in each morphotype’s distribution. The unique species showed strong preferences for ray colour and disc appendage variants that were native to their distributions, with ubiquitous visitors being largely indiscriminate in their floral preferences. This suggests that floral divergence in D. pluvialis-sinuata reflects local adaptation through the relative fitness advantage of attracting the unique visitor assemblage, while these adaptations incur little to no cost in the attraction of dominant visitors. Consequently, ethological isolation in sympatry is weak, suggesting that pollinator-mediated selection alone is unlikely to maintain floral differences between the three morphotypes. This study is the first in GCFR pollination ecology to show that pollinator-mediated selection has contributed to striking geographic variation in floral traits within a generalized pollination system. It concludes that while pollinator-mediated selection plays a role in divergence, dispersal barriers or habitat specialization are likely more influential in maintaining floral differences across the landscape. Thus, the study offers insight into the potential interplay of multiple processes underlying geographically structured floral variation, and it encourages the need for a broader taxonomic perspective on the drivers of floral evolution in the Cape. AFRIKAANSE OPSOMMING: Plaaslike aanpassing aan geografies veranderlike bestuiwerfauna speel 'n belangrike rol in angiosperm spesiasie binne die Groter Kaapse Blomstreek (GKBR). Terwyl die Orchidaceae en Iridaceae uitgebreide studie in hierdie veld ontvang het, is minder aandag gegee aan generale lineages soos die Asteraceae, ten spyte van bewyse van ruimtelik gestruktureerde florale eienskapvariasie wat onderliggend is aan bestuiwer-gemedieerde seleksiegradiënte. Verder beklemtoon die heersende teorie van bestuiwer-gedrewe divergensie verskuiwings in die fundamentele bestuiwingsnis deur bestuiwer-verspreidingsgrense, maar baie studies fokus uitsluitlik op die gerealiseerde bestuiwingsnis, wat moontlik die invloed van ander faktore soos ruimtelike variasie in die plantgemeenskapkonteks oorsien. Hierdie tesis ondersoek ruimtelike variasie in bestuiwerbeskikbaarheid en -gebruik as drywers van florale divergensie in Dimorphotheca pluvialis-sinuata, 'n jaarlikse madeliefie spesiekompleks inheems aan die GKBR, met die fokus op bestuiwing-generalis populasies in die suidweselike verspreiding van die kompleks. Hoofstuk 2 karakteriseer florale variasie, karteer sy ruimtelike struktuur, en assesseer sy genetiese grondslag deur 'n gemeenskapstuin eksperiment. Multivariante ontledings klassifiseer die florale variasie in drie afsonderlike morfotipes gebaseer op straalblom kleurpatrone en skyfblom aanhangsel dimensies. Hierdie eienskappe bly duidelik oor groei- omgewings, wat dui op evolusionêre divergensie eerder as fenotipiese plastisiteit. Ruimtelike analise toon 'n allopatiese verspreiding van morfotipes met minimale eienskap introgressie, wat dui op geografiese isolasie as kritiek vir die handhawing van die ruimtelik diskrete variasie in die stelsel. Hoofstuk 3 ondersoek bestuiwer mozaïe deur beide bestuiwer gebruik en beskikbaarheid te oorweeg, toets vir plaaslike aanpassing aan besoekers se visuele voorkeure, en evalueer die rol van straalkleur en skyfmorfologie in die etologiese isolasie van morfotipes. Al drie morfotipes lok 'n ryk insekgemeenskap aan wat hoofsaaklik bestaan uit dieselfde stel dominante besoekers, met beperkte bewyse vir die invloed van eienskap filtrering en die plantgemeenskap konteks op verskille in die gebruik van hierdie besoekers tussen morfotipes. Ten spyte hiervan was 'n essensieel kwalitatiewe mozaïek van unieke en hoogs effektiewe bestuiwer spesies beskikbaar in elke morfotipe se verspreiding. Die unieke spesies toon sterk voorkeure vir straal kleur en skyf aanhangsel variasies wat inheems is aan hul verspreidings, terwyl alomteenwoordige besoekers grootliks ondiskriminerend is in hul florale voorkeure. Dit dui daarop dat florale divergensie in D. pluvialis-sinuata plaaslike aanpassing weerspieël deur die relatiewe fiksheidsvoordeel van die aantrek van die unieke besoekersamestelling, terwyl hierdie aanpassings min tot geen koste in die aantrek van dominante besoekers veroorsaak. Gevolglik is etologiese isolasie in sinpatry swak, wat aandui dat bestuiwer-gemedieerde seleksie alleen onwaarskynlik is om florale verskille tussen die drie morfotipes te handhaaf. Hierdie studie, uniek in GKBR bestuiwing ekologie, beklemtoon hoe bestuiwer-gemedieerde seleksie bydra tot opvallende geografiese florale variasie binne 'n veralgemeende bestuiwingstelsel. Dit sluit af dat terwyl bestuiwer-gemedieerde seleksie 'n rol speel in divergensie, verspreidingsbarrières of habitat spesialisasie waarskynlik groter invloed het op die handhawing van florale verskille regoor die landskap. Die bevindinge beklemtoon die kompleksiteit van faktore wat bydra tot geografies gestruktureerde florale variasie en bepleit vir 'n breër taksonomiese perspektief op die drywers van florale evolusie in die Kaap. Masters 2025-02-04T06:12:14Z 2025-02-04T06:12:14Z 2024-12 Thesis https://scholar.sun.ac.za/handle/10019.1/131652 en Stellenbosch University vii, 114 pages : illustrations (some color), maps application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Pollinators -- South Africa -- Greater Cape Floristic Region Animal-plant relationships Plants -- Variation -- Genetics Biogeography Dimorphotheca daisies -- Phylogeny UCTD Engelen, Arjan Pollinator-mediated floral diversication of annual dimorphotheca daisies in the Cape Floristic Region |
| title | Pollinator-mediated floral diversication of annual dimorphotheca daisies in the Cape Floristic Region |
| title_full | Pollinator-mediated floral diversication of annual dimorphotheca daisies in the Cape Floristic Region |
| title_fullStr | Pollinator-mediated floral diversication of annual dimorphotheca daisies in the Cape Floristic Region |
| title_full_unstemmed | Pollinator-mediated floral diversication of annual dimorphotheca daisies in the Cape Floristic Region |
| title_short | Pollinator-mediated floral diversication of annual dimorphotheca daisies in the Cape Floristic Region |
| title_sort | pollinator mediated floral diversication of annual dimorphotheca daisies in the cape floristic region |
| topic | Pollinators -- South Africa -- Greater Cape Floristic Region Animal-plant relationships Plants -- Variation -- Genetics Biogeography Dimorphotheca daisies -- Phylogeny UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/131652 |
| work_keys_str_mv | AT engelenarjan pollinatormediatedfloraldiversicationofannualdimorphothecadaisiesinthecapefloristicregion |