Evolution of Spur Length in a Moth-pollinated Orchid
There is considerable evidence that pollinator shifts can explain many differences in flower morphology between closely related plant species, but the extent to which pollinator shifts can explain the maintenance of among-population variation in floral traits within species is poorly known. In this...
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Uppsala universitet, Ekologisk botanik
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ndltd-UPSALLA1-oai-DiVA.org-uu-1130862013-01-08T13:07:04ZEvolution of Spur Length in a Moth-pollinated OrchidengBoberg, ElinUppsala universitet, Ekologisk botanikUppsala : Acta Universitatis Upsaliensis2010Platanthera bifoliafloral evolutionnatural selectionpollinationspur lengthpopulation differentiationdivergent selectiondisruptive selectionreproductive isolationBiologyBiologiThere is considerable evidence that pollinator shifts can explain many differences in flower morphology between closely related plant species, but the extent to which pollinator shifts can explain the maintenance of among-population variation in floral traits within species is poorly known. In this thesis, I combined comparative and experimental approaches to examine the evolution of floral traits in the moth-pollinated orchid Platanthera bifolia. More specifically, I investigated (1) the relationship between flower and pollinator morphology, (2) phenotypic selection on morphology and phenology in populations in contrasting environments, (3) components of prezygotic reproductive isolation among divergent populations, and (4) the adaptive and functional significance of two correlated floral traits. A study of Scandinavian of P. bifolia populations revealed that spur length was positively correlated with proboscis length of local pollinators, which suggests that variation in spur length reflects adaptive evolution in response to geographically variable pollinator-mediated selection. A phenotypic selection study on Öland, SE Sweden, suggested that disruptive selection on spur length contributes to the maintenance of a bimodal distribution of spur length in mixed habitats, but provided very limited evidence of divergent selection on plant morphology and flowering phenology in grassland and woodland habitats. Field experiments revealed strong reproductive isolation between divergent populations on Öland, due to differences in spatial distribution, flowering phenology, and pollinators, and among-population incompatibility. The results suggest that prezygotic reproductive isolation contributes to the maintenance of population differentiation in floral traits in P. bifolia. A field manipulation experiment demonstrated that spur length but not perianth size affects pollination success and seed production. This suggests that among-population differentiation in perianth size may be the result of a genetic correlation with spur length. Taken together, the results of this thesis suggest that pollinator-mediated selection can shape the evolution of intraspecific floral variation. Doctoral thesis, comprehensive summaryinfo:eu-repo/semantics/doctoralThesistexthttp://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-113086urn:isbn:978-91-554-7714-1Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, 1651-6214 ; 712application/pdfinfo:eu-repo/semantics/openAccess |
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English |
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Doctoral Thesis |
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Platanthera bifolia floral evolution natural selection pollination spur length population differentiation divergent selection disruptive selection reproductive isolation Biology Biologi |
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Platanthera bifolia floral evolution natural selection pollination spur length population differentiation divergent selection disruptive selection reproductive isolation Biology Biologi Boberg, Elin Evolution of Spur Length in a Moth-pollinated Orchid |
description |
There is considerable evidence that pollinator shifts can explain many differences in flower morphology between closely related plant species, but the extent to which pollinator shifts can explain the maintenance of among-population variation in floral traits within species is poorly known. In this thesis, I combined comparative and experimental approaches to examine the evolution of floral traits in the moth-pollinated orchid Platanthera bifolia. More specifically, I investigated (1) the relationship between flower and pollinator morphology, (2) phenotypic selection on morphology and phenology in populations in contrasting environments, (3) components of prezygotic reproductive isolation among divergent populations, and (4) the adaptive and functional significance of two correlated floral traits. A study of Scandinavian of P. bifolia populations revealed that spur length was positively correlated with proboscis length of local pollinators, which suggests that variation in spur length reflects adaptive evolution in response to geographically variable pollinator-mediated selection. A phenotypic selection study on Öland, SE Sweden, suggested that disruptive selection on spur length contributes to the maintenance of a bimodal distribution of spur length in mixed habitats, but provided very limited evidence of divergent selection on plant morphology and flowering phenology in grassland and woodland habitats. Field experiments revealed strong reproductive isolation between divergent populations on Öland, due to differences in spatial distribution, flowering phenology, and pollinators, and among-population incompatibility. The results suggest that prezygotic reproductive isolation contributes to the maintenance of population differentiation in floral traits in P. bifolia. A field manipulation experiment demonstrated that spur length but not perianth size affects pollination success and seed production. This suggests that among-population differentiation in perianth size may be the result of a genetic correlation with spur length. Taken together, the results of this thesis suggest that pollinator-mediated selection can shape the evolution of intraspecific floral variation. |
author |
Boberg, Elin |
author_facet |
Boberg, Elin |
author_sort |
Boberg, Elin |
title |
Evolution of Spur Length in a Moth-pollinated Orchid |
title_short |
Evolution of Spur Length in a Moth-pollinated Orchid |
title_full |
Evolution of Spur Length in a Moth-pollinated Orchid |
title_fullStr |
Evolution of Spur Length in a Moth-pollinated Orchid |
title_full_unstemmed |
Evolution of Spur Length in a Moth-pollinated Orchid |
title_sort |
evolution of spur length in a moth-pollinated orchid |
publisher |
Uppsala universitet, Ekologisk botanik |
publishDate |
2010 |
url |
http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-113086 http://nbn-resolving.de/urn:isbn:978-91-554-7714-1 |
work_keys_str_mv |
AT bobergelin evolutionofspurlengthinamothpollinatedorchid |
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1716509392954720256 |