The role of competition and mutualism in shaping microbial communities in Protea flowers
| dc.contributor.advisor | Roets, Francois | en_ZA |
| dc.contributor.advisor | Dreyer, L. L. | en_ZA |
| dc.contributor.author | Mukwevho, Vuledzani Oral | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of Agrisciences. Dept. of Conservation Ecology and Entomology. | en_ZA |
| dc.date.accessioned | 2019-11-18T11:52:02Z | |
| dc.date.accessioned | 2019-12-11T06:40:06Z | |
| dc.date.available | 2021-05-18T03:00:12Z | |
| dc.date.issued | 2019-12 | |
| dc.description | Thesis (PhDAgric)--Stellenbosch University, 2019. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: Protea is a keystone member of the Cape floristic region and a crucial part of the ecological functioning of the fynbos ecosystem. These plants structurally dominate fynbos vegetation and they maintain large numbers of phytophagous organisms and pollinators. Their iconic inflorescences form the basis of a thriving cut flower industry, but this is under threat from pests and pathogens. Protea inflorescences and infructescences are also colonised by saprobic fungi that are of phytosanitary concern. These are dominated by ophiostomatoid fungi in the genera Knoxdaviesia and Sporothrix that form complex, often mutualistic, interactions with mites, pollinating insects and pollinating birds. How these fungi affect their host plants are not currently known. Also, it is unknown how they are able to dominate fungal communities within an environment optimal also for the dominance of common contaminant saprobic fungi. The fourteen described species of ophiostomatoid fungi from Protea inflorescences have well-defined host ranges and may even be associated with specific tissue types. Here I test various hypotheses related to fungal competitive abilities to explain patterns of association between ophiostomatoid fungal species, ‗environmentally acquired‘ fungal taxa, and their hosts. I showed that host chemistry partially explain host exclusivity of ophiostomatoid fungi, but that differences in the actions of spore vectors may be more important. I found that without ophiostomatoid fungi, infructuscences are dominated by ‗environmentally acquired‘ fungi such as Penicillium, Cladosporium and Fusarium. Even though the ophiostomatoid fungi are comparatively weak competitors, they are able to defend captured space against these when they colonise structures early and when they grow on their usual hosts. Although ophiostomatoid fungi do not increase numbers of viable seeds, they prevent seed release when recruitment will be suboptimal. This is because infructuscences containing ophiostomatoid fungi persist longer on plants. There is therefore mutual benefit for the association between Protea and ophiostomatoid fungi. I also uncovered complex interactions between different ophiostomatoid fungi within individual infructescences. Some species are neutral competitors and they can occupy the same tissue types within individual infructescences, while others are strong competitors on specific tissue types and can exclude competing species. Again the actions of spore vectors likely explain the persistence of weaker competitors in this scenario, but the actions of possible bacterial mutualists or other microbes should not be ignored in future studies. In this work I demonstrated the use of fungal competition studies for investigations into host relations and dispersal ecology of microbes in an atypical ecosystem, but these same techniques can be adapted to investigate associations between microbes in multiple other systems. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Protea is ʼn sleutel lid van die Kaapse Floristiese streek en ʼn uiters belangrike deel van die ekologiese funksionering van die fynbos ekosisteem. Hierdie plante domineer fynbos plantegroei struktureel, en hulle onderhou groot getalle fitofae organismes en bestuiwers. Hulle ikoniese bloeiwyses vorm die basis van ʼn suksesvolle snyblom industrie, maar dit word bedreig deur peste en patogene. Protea bloeiwyses en saadkeëls word ook gekoloniseer deur saprofitiese fungi wat ʼn fitosanitêre probleem skep. Hierdie word gedomineer deur ophiostomatiede fungi in die genera Knoxdaviesia en Sporothrix wat komplekse, dikwels mutualistiese interaksies met myte, bestuiwer insekte en bestuiwer voëls vorm. Dis steeds onbekend hoe hierdie fungi hul gasheerplante beïnvloed. Dis verder onbekend hoe hulle in staat is om fungi gemeenskappe te domineer binne ʼn omgewing wat ook optimaal is vir dominansie deur algemene, kontaminerende saprofitiese fungi. Die veertien beskryfde spesies van ophiostomatiede fungi vanaf Protea bloeiwyses het goed gedefinieerde gasheer reekse en mag selfs met spesifieke weefseltipes geassosieer wees. Hier toets ek verskeie hipoteses wat verban hou met fungi se kompeterende vermoëns om die patrone van assosiasie tussen ophiostomatiese fungs spesies, kontaminerende fungus taxa en hulle gashere te verduidelik. Ek wys dat gasheer chemie gasheer eksklusiwiteit van ophiostomatiede fungi ten dele verduidelik, maar dat verskille in die aksies van spoorvektore meer belangrik mag wees. Ek het gevind dat sonder ophiostomatiede fungi, bloeiwyses gedomineer word deur kontaminerende fungis soos Penicillium, Cladosporium en Fusarium. Al is die ophiostomatiede fungi vergelykend swak kompeteerders, is hulle in staat om geannekseerde ruimte te beskerm teen hierdie genera wanneer hulle strukture vroeg koloniseer en wanneer hulle op hulle gewone gashere groei. Alhoewel ophiostomatiede fungi nie die aantal lewensvatbare sade vermeerder nie, verhoed hulle saadvrystelling wanneer suksesvolle ontkieming suboptimaal is. Daar is dus mutualistiese voordeel vir die assosiasie tussen Protea en ophiostomatiede fungi. Ek het ook die komplekse interaksies tussen verskillende ophiostomatiede fungi binne individuele saadkeëls ontrafel. Sommige spesie is neutrale kompeteerders en hulle kan dieselfde weefseltipes binne individuele saadkeëls bewoon, terwyl ander sterk kompeteerders is op spesifieke weefseltipes en kan kompeterende spesie uitsluit. Weereens verduidelik die aksie van spoorvektore waarskynlik die behoud van swakker kompeteerders in hierdie senario, maar die aksies van moontlike bakteriële mutualiste of ander mikrobe moet nie geïgnoreer word in toekomstige studies nie. In hierdie werk het ek gedemonstreer hoe fungus kompetisie studies in ondersoeke na gasheerverwantskappe en verspreidingsekologie van mikrobe in ʼn atipiese sisteem gebruik kan word, maar hierdie selfde tegnieke kan aangepas word om assosiasies tussen mikrobe in verkeie ander sisteme te ondersoek. | af_ZA |
| dc.description.version | Doctoral | |
| dc.embargo.terms | 2021-05-18 | |
| dc.format.extent | xiv, 123 pages : illustrations (some color) | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/106951 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.subject | Protea -- Flowering | en_ZA |
| dc.subject | Protea -- Breeding -- South Africa -- Cape Floristic region | en_ZA |
| dc.subject | Protea -- Ecology | en_ZA |
| dc.subject | Protea -- Diseases and pests -- South Africa | en_ZA |
| dc.subject | Insect-plant relationships | en_ZA |
| dc.subject | Protea -- Effect of climatic changes on | en_ZA |
| dc.title | The role of competition and mutualism in shaping microbial communities in Protea flowers | en_ZA |
| dc.type | Thesis | en_ZA |