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- Chapurlat, Elodie, et al.
(författare)
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Diel pattern of floral scent emission matches the relative importance of diurnal and nocturnal pollinators in populations of Gymnadenia conopsea
- 2018
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Ingår i: Annals of Botany. - : Oxford University Press (OUP). - 0305-7364 .- 1095-8290. ; 121, s. 711-721
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Tidskriftsartikel (refereegranskat)abstract
- Background and AimsFloral scent is considered an integral component of pollination syndromes, and its composition and timing of emission are thus expected to match the main pollinator type and time of activity. While floral scent differences among plant species with different pollination systems can be striking, studies on intraspecific variation are sparse, which limits our understanding of the role of pollinators in driving scent divergence.MethodsHere, we used dynamic headspace sampling to quantify floral scent emission and composition during the day and at night in the natural habitat of six Scandinavian populations of the fragrant orchid Gymnadenia conopsea. We tested whether diel scent emission and composition match pollinator type by comparing four populations in southern Sweden, where nocturnal pollinators are more important for plant reproductive success than are diurnal pollinators, with two populations in central Norway, where the opposite is true. To determine to what extent scent patterns quantified in the field reflected plasticity, we also measured scent emission in a common growth chamber environment.Key ResultsBoth scent composition and emission rates differed markedly between day and night, but only the latter varied significantly among populations. The increase in scent emission rate at night was considerably stronger in the Swedish populations compared with the Norwegian populations. These patterns persisted when plants were transferred to a common environment, suggesting a genetic underpinning of the scent variation.ConclusionsThe results are consistent with a scenario where spatial variation in relative importance of nocturnal and diurnal pollinators has resulted in selection for different scent emission rhythms. Our study highlights the importance of adding a characterization of diel variation of scent emission rates to comparative studies of floral scent, which so far have often focused on scent composition only.
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| 2. |
- Chapurlat, Elodie, 1988-
(författare)
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Evolutionary Ecology of Floral Traits in Fragrant Orchids
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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