Variation in breeding systems and consequences for reproductive traits in Erica

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dc.contributor.advisorMidgley, Jeremy Jen_ZA
dc.contributor.advisorJohnson, Steven Den_ZA
dc.contributor.authorArendse, Brittanyen_ZA
dc.date.accessioned2015-12-01T09:25:16Z
dc.date.available2015-12-01T09:25:16Z
dc.date.issued2015en_ZA
dc.descriptionIncludes bibliographical referencesen_ZA
dc.description.abstractErica makes up 7% of all species in the Cape flora. It is the most species-rich genus in the Cape Floristic Region (CFR), which has an area 0f 90 000km². Erica species have great inter- and intra-specific variation in floral form as well as in post-fire regeneration strategies. Previous studies of other plant groups (Barrett et al. 1996; Button et al. 2012) have illustrated changes in floral traits with a shift from outcrossing to selfing. The aim of this thesis was to determine whether similar changes occur in Erica. I thus analysed breeding systems in Erica in relation to floral traits, pollinators, and fire survivals strategies. Seed and fruit set data obtained from hand-pollination treatments suggested that self- fertilization occurs rarely. Autonomous selfing did not generally yield significant seed set. When comparing changes in floral traits with increased selfing ability and pollination syndromes weak relationships were observed. Average plant height showed a positive relationship with selfing ability but this correlation was not significant. Comparing traits within small and large flowered species separately yielded significant relationships between corolla size and selfing ability of small-flowered species.. Furthermore, general trends indicate that small-flowered species have increased ability to self-fertilise when corolla sizes are larger, corolla apertures larger and herkogamy reduced. Large-flowered species employ the same strategy but average corolla aperture is reduced. A trade-off between the size and the number of flowers was seen within the Erica genus. Small-flowered species had significantly more flowers compared to larger- flowered species that had markedly fewer flowers per unit height. This finding has implications for the selfing potential of small-flowered species as increased self- incompatibility may have evolved in order to reduce the effects of increased geitonogamy due to increased floral number. The prediction that self-fertilisation would be increased in seeders compared to resprouters, on the basis that seeders are more reliant on seeds for persistence than resprouters, was not realised when comparing the selfing ability of different fire- survival strategies. Erica mammosa, a species with morphs possessing both fire-survival strategies, shows no significant differences in selfing ability, this includes differences in pollen-ovule (P/O) ratios. However, indices suggest the resprouting form of E. mammosa to have an increased ability to self-fertilize while the seeder form has an increased ability for autonomous selfing. The 29 species analysed were divided into outcrossers and facultative outcrossers based on selfing indices but these did not fit neatly within Cruden’s proposed P/O ranges (facultative autogamy: P/Os= 32-397; facultative outcrossers: P/Os= 160.7 - 2258.6; outcrossers: P/Os= 1062 - 19525). This may be due to his classification of species into breeding systems being based on relatively few distantly related species per category with extremely variable P/O ratios per category. For example, outcrossers ranged an order of magnitude (from 1000+ to 20 000). It is also true that this ratio can be influenced by a variety of different factors, these include: habitat, evolutionary history and pollination syndrome. Consequently, P/O ratios in Erica do not seem to reflect pollination syndromes very well. Presumably, sex allocation theory may explain the relationship of breeding system with P/O ratios better. Histological studies of pollen tube growth for self- and cross-pollinated flowers of eight species suggested that Erica has late acting self-incompatibility (LSI). LSI is a barrier to selfing that occurs in the ovary. However, I could not determine if the rejection process occurs pre- or post-fertilization. Although, a large amount of knowledge is still lacking, this preliminary study provided insight into the reproductive biology of Erica.en_ZA
dc.identifier.apacitationArendse, B. (2015). <i>Variation in breeding systems and consequences for reproductive traits in Erica</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Biological Sciences. Retrieved from http://hdl.handle.net/11427/15494en_ZA
dc.identifier.chicagocitationArendse, Brittany. <i>"Variation in breeding systems and consequences for reproductive traits in Erica."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 2015. http://hdl.handle.net/11427/15494en_ZA
dc.identifier.citationArendse, B. 2015. Variation in breeding systems and consequences for reproductive traits in Erica. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Arendse, Brittany AB - Erica makes up 7% of all species in the Cape flora. It is the most species-rich genus in the Cape Floristic Region (CFR), which has an area 0f 90 000km². Erica species have great inter- and intra-specific variation in floral form as well as in post-fire regeneration strategies. Previous studies of other plant groups (Barrett et al. 1996; Button et al. 2012) have illustrated changes in floral traits with a shift from outcrossing to selfing. The aim of this thesis was to determine whether similar changes occur in Erica. I thus analysed breeding systems in Erica in relation to floral traits, pollinators, and fire survivals strategies. Seed and fruit set data obtained from hand-pollination treatments suggested that self- fertilization occurs rarely. Autonomous selfing did not generally yield significant seed set. When comparing changes in floral traits with increased selfing ability and pollination syndromes weak relationships were observed. Average plant height showed a positive relationship with selfing ability but this correlation was not significant. Comparing traits within small and large flowered species separately yielded significant relationships between corolla size and selfing ability of small-flowered species.. Furthermore, general trends indicate that small-flowered species have increased ability to self-fertilise when corolla sizes are larger, corolla apertures larger and herkogamy reduced. Large-flowered species employ the same strategy but average corolla aperture is reduced. A trade-off between the size and the number of flowers was seen within the Erica genus. Small-flowered species had significantly more flowers compared to larger- flowered species that had markedly fewer flowers per unit height. This finding has implications for the selfing potential of small-flowered species as increased self- incompatibility may have evolved in order to reduce the effects of increased geitonogamy due to increased floral number. The prediction that self-fertilisation would be increased in seeders compared to resprouters, on the basis that seeders are more reliant on seeds for persistence than resprouters, was not realised when comparing the selfing ability of different fire- survival strategies. Erica mammosa, a species with morphs possessing both fire-survival strategies, shows no significant differences in selfing ability, this includes differences in pollen-ovule (P/O) ratios. However, indices suggest the resprouting form of E. mammosa to have an increased ability to self-fertilize while the seeder form has an increased ability for autonomous selfing. The 29 species analysed were divided into outcrossers and facultative outcrossers based on selfing indices but these did not fit neatly within Cruden’s proposed P/O ranges (facultative autogamy: P/Os= 32-397; facultative outcrossers: P/Os= 160.7 - 2258.6; outcrossers: P/Os= 1062 - 19525). This may be due to his classification of species into breeding systems being based on relatively few distantly related species per category with extremely variable P/O ratios per category. For example, outcrossers ranged an order of magnitude (from 1000+ to 20 000). It is also true that this ratio can be influenced by a variety of different factors, these include: habitat, evolutionary history and pollination syndrome. Consequently, P/O ratios in Erica do not seem to reflect pollination syndromes very well. Presumably, sex allocation theory may explain the relationship of breeding system with P/O ratios better. Histological studies of pollen tube growth for self- and cross-pollinated flowers of eight species suggested that Erica has late acting self-incompatibility (LSI). LSI is a barrier to selfing that occurs in the ovary. However, I could not determine if the rejection process occurs pre- or post-fertilization. Although, a large amount of knowledge is still lacking, this preliminary study provided insight into the reproductive biology of Erica. DA - 2015 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2015 T1 - Variation in breeding systems and consequences for reproductive traits in Erica TI - Variation in breeding systems and consequences for reproductive traits in Erica UR - http://hdl.handle.net/11427/15494 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/15494
dc.identifier.vancouvercitationArendse B. Variation in breeding systems and consequences for reproductive traits in Erica. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 2015 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/15494en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDepartment of Biological Sciencesen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherBotanyen_ZA
dc.subject.otherPlant Ecologyen_ZA
dc.titleVariation in breeding systems and consequences for reproductive traits in Ericaen_ZA
dc.typeMaster Thesis
dc.type.qualificationlevelMasters
dc.type.qualificationnameMScen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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