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Divergent selection on flowering phenology but not on floral morphology between two closely related orchids
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
Ecole Normale Supérieure de Lyon.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
(English)Manuscript (preprint) (Other academic)
National Category
Ecology Evolutionary Biology
Identifiers
URN: urn:nbn:se:uu:diva-358245OAI: oai:DiVA.org:uu-358245DiVA, id: diva2:1241919
Available from: 2018-08-26 Created: 2018-08-26 Last updated: 2018-08-26
In thesis
1. Evolutionary Ecology of Floral Traits in Fragrant Orchids
Open this publication in new window or tab >>Evolutionary Ecology of Floral Traits in Fragrant Orchids
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Why are flowers so diverse? Much of floral evolution is thought to be driven by pollinator-mediated selection. However, the connection between macroevolutionary patterns of floral diversity and microevolutionary processes remains poorly understood. In this thesis, I have used the fragrant orchids Gymnadenia conopsea s.s. and Gymnadenia densiflora to investigate the role of pollinators as agents of selection on floral traits and to test whether they cause spatial variation in selection. I addressed the following questions (1) Is there divergent selection on flowering phenology and floral traits between these two closely related species? (2) What is the contribution of pollinators relative to other selective agents to selection on phenology, visual display, floral scent and spur length? (3) Do diurnal and nocturnal pollinators mediate different selection patterns? (4) Does spatial variation in pollinator communities cause spatial variation in selection?

A phenotypic selection study in G. conopsea s.s. and G. densiflora indicated that divergent selection on flowering time contributes to the maintenance of phenological differentiation between the two species. Hand-pollination experiments combined with selection analysis showed that while pollinators were the main selective agent on spur length, their contribution to selection on phenology, visual display and floral scent was more variable and sometimes opposed by non-pollinator mediated selection. Selection analyses combined with a selective exclusion experiment showed that diurnal and nocturnal pollinators exerted different selection patterns on floral traits. Hand-pollination experiments also demonstrated that variation in pollinator-mediated selection largely explained spatial variation in net selection on phenology, visual display and spur length among four populations. A study of floral scent emission of G. conopsea s.s. in the field coupled with a growth-chamber experiment revealed genetically-based variation in floral scent consistent with a scenario where spatial variation in relative importance of nocturnal and diurnal pollinators has resulted in the evolution of different scent emission rhythms.

Taken together, the results support the hypothesis that pollinators cause spatial variation in selection on floral traits. They also highlight the importance of experimentally identifying sources of selection to reveal conflicting and reinforcing selection by multiple agents and thus advance our understanding of the evolutionary ecology of floral traits.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 64
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1713
Keywords
agents of selection, diurnal and nocturnal pollination, divergent selection, field experiment, floral evolution, floral scent, Gymnadenia conopsea, Gymnadenia densiflora, Orchidaceae, phenotypic selection, pollinator-mediated selection, spatial variation, scent rhythm
National Category
Ecology Evolutionary Biology
Identifiers
urn:nbn:se:uu:diva-358249 (URN)978-91-513-0425-0 (ISBN)
Public defence
2018-10-12, Zootissalen, Villavägen 9, Uppsala, 13:00 (English)
Opponent
Supervisors
Available from: 2018-09-20 Created: 2018-08-26 Last updated: 2018-10-02

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