| 1. |
- Eisen, Katherine E., et al.
(författare)
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Honest floral signalling traits vary across and within populations in an insect-pollinated plant
- 2023
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Ingår i: Functional Ecology. - 0269-8463. ; 37:9, s. 2511-2522
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Tidskriftsartikel (refereegranskat)abstract
- In flowering plants that produce concealed rewards, pollinator foraging preferences may select for floral advertisement traits that are correlated with rewards. To date, studies have not focused on the potential for honest signals to vary across populations, which could occur due to differences in pollinator communities or plant mating system. We tested for variation in honest signals across and within populations and mating systems in Arabis alpina, a broadly distributed arctic-alpine perennial herb that is visited by a variable community of insects. In a greenhouse common garden, we tested for correlations between corolla area, floral scent and nectar volume in 29 populations. In 12 field populations, we examined variation in pollen limitation and corolla area. Across and within populations and mating systems, larger flowers generally produced more nectar. Total scent emission was not correlated with nectar production, but two compounds—phenylacetaldehyde and benzyl alcohol—may be honest signals in some populations. Corolla area was correlated with pollen limitation only across populations. Our results suggest that honest signals may be similar across populations but may not result from contemporary direct selection on floral advertisements. Read the free Plain Language Summary for this article on the Journal blog.
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| 2. |
- Hederström, Veronica, et al.
(författare)
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Pollinator-mediated effects of landscape-scale land use on grassland plant community composition and ecosystem functioning – seven hypotheses
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Ingår i: Biological Reviews. - 1464-7931.
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Tidskriftsartikel (refereegranskat)abstract
- Environmental change is disrupting mutualisms between organisms worldwide. Reported declines in insect populations and changes in pollinator community compositions in response to land use and other environmental drivers have put the spotlight on the need to conserve pollinators. While this is often motivated by their role in supporting crop yields, the role of pollinators for reproduction and resulting taxonomic and functional assembly in wild plant communities has received less attention. Recent findings suggest that observed and experimental gradients in pollinator availability can affect plant community composition, but we know little about when such shifts are to be expected, or the impact they have on ecosystem functioning. Correlations between plant traits related to pollination and plant traits related to other important ecosystem functions, such as productivity, nitrogen uptake or palatability to herbivores, lead us to expect non-random shifts in ecosystem functioning in response to changes in pollinator communities. At the same time, ecological and evolutionary processes may counteract these effects of pollinator declines, limiting changes in plant community composition, and in ecosystem functioning. Despite calls to investigate community- and ecosystem-level impacts of reduced pollination, the study of pollinator effects on plants has largely been confined to impacts on plant individuals or single-species populations. With this review we aim to break new ground by bringing together aspects of landscape ecology, ecological and evolutionary plant–insect interactions, and biodiversity–ecosystem functioning research, to generate new ideas and hypotheses about the ecosystem-level consequences of pollinator declines in response to land-use change, using grasslands as a focal system. Based on an integrated set of seven hypotheses, we call for more research investigating the putative pollinator-mediated links between landscape-scale land use and ecosystem functioning. In particular, future research should use combinations of experimental and observational approaches to assess the effects of changes in pollinator communities over multiple years and across species on plant communities and on trait distributions both within and among species.
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| 3. |
- Luizzi, Victoria J., et al.
(författare)
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Phenotypic plasticity in floral scent in response to nutrient, but not water, availability in the perennial plant Arabis alpina
- 2021
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Ingår i: Functional Ecology. - : Wiley. - 0269-8463 .- 1365-2435. ; 35:8, s. 1655-1665
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Tidskriftsartikel (refereegranskat)abstract
- Floral scent is an important mediator of plant–pollinator interactions. Multiple recent studies report ample intraspecific scent variation among populations and individuals. Yet, few studies have eastimated effects of phenotypic plasticity on floral scent in response to differing environmental factors. In this study, we investigated the effects of nutrient and water availability on floral scent in self-compatible and self-incompatible populations of the perennial herb Arabis alpina. We subjected greenhouse grown plants to different nutrient and water treatments in a crossed design, examined the effects on floral scent emission rate and composition, compared the level of plasticity to that of other plant traits, and conducted hand-pollinations of nutrient-limited individuals to test for a potential allocation cost of scent production. For both self-compatible and self-incompatible populations, the per-flower scent emission rate was 1.2–4 times higher when nutrients were abundant, but this effect explained little variation in scent emission rate and was limited compared to plasticity in flower number. There was no effect of water treatment on scent emission. Additionally, neither treatment had an effect on the composition of the floral scent, and there was no detectable trade-off between scent and seed production that would imply a cost of floral scent production. Overall, while per-flower floral scent emission displayed limited phenotypic plasticity in response to nutrient conditions, the total amount of scent emitted by plants may increase more strongly at higher nutrient availabilities due to an increase in flower production. Therefore, our results suggest that fitness benefits due to increased scent emission rates under favourable nutrient conditions might depend on the extent to which floral scent serves as a long- or short-distance pollinator attractant for the focal plant species. A free Plain Language Summary can be found within the Supporting Information of this article.
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| 4. |
- Petrén, Hampus, et al.
(författare)
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Differences in mating system and predicted parental conflict affect post-pollination reproductive isolation in a flowering plant
- 2023
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Ingår i: Evolution; international journal of organic evolution. - : Oxford University Press (OUP). - 1558-5646 .- 0014-3820. ; 77:4, s. 1019-1030
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Tidskriftsartikel (refereegranskat)abstract
- Mating system shifts from outcrossing to selfing are frequent in plant evolution. Relative to outcrossing, selfing is associated with reduced parental conflict over seed provisioning, which may result in postzygotic, asymmetric, reproductive isolation in crosses between populations of different mating systems. To test the hypothesis that post-pollination reproductive isolation between populations increases with increasing differences in mating system and predicted parental conflict, we performed a crossing experiment involving all combinations of three self-compatible populations (with low outcrossing rates), and three self-incompatible populations (with high outcrossing rates) of the arctic-alpine herb Arabis alpina, assessing fitness-related seed and plant traits of the progeny. Predicted levels of parental conflict ("genome strength") were quantified based on strength of self-incompatibility and estimates of outcrossing rates. Crosses between self-compatible and self-incompatible populations yielded very small seeds of low viability, resulting in strong reproductive isolation. In 14 of 15 reciprocal between-population crosses, seeds were heavier when the paternal plant had the stronger genome, and seed mass differences between cross directions increased with an increased difference in parental conflict. Overall, our results suggest that, when sufficiently large, differences in mating system and hence in expected parental conflict may result in strong post-pollination reproductive barriers contributing to speciation.
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| 5. |
- Petrén, Hampus, et al.
(författare)
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Evolution of floral scent in relation to self-incompatibility and capacity for autonomous self-pollination in the perennial herb Arabis alpina
- 2021
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Ingår i: Annals of Botany. - : Oxford University Press (OUP). - 0305-7364 .- 1095-8290. ; 127:6, s. 737-747
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Tidskriftsartikel (refereegranskat)abstract
- Background and Aims: The transition from outcrossing to selfing is a frequent evolutionary shift in flowering plants and is predicted to result in reduced allocation to pollinator attraction if plants can self-pollinate autonomously. The evolution of selfing is associated with reduced visual floral signalling in many systems, but effects on floral scent have received less attention. We compared multiple populations of the arctic-alpine herb Arabis alpina (Brassicaceae), and asked whether the transition from self-incompatibility to self-compatibility has been associated with reduced visual and chemical floral signalling. We further examined whether floral signalling differ between self-compatible populations with low and high capacity for autonomous self-pollination, as would be expected if benefits of signalling decrease with reduced dependence on pollinators for pollen transfer. Methods: In a common garden we documented flower size and floral scent emission rate and composition in eight self-compatible and nine self-incompatible A. alpina populations. These included self-compatible Scandinavian populations with high capacity for autonomous self-pollination, self-compatible populations with low capacity for autonomous self-pollination from France and Spain, and self-incompatible populations from Italy and Greece. Key Results: The self-compatible populations produced smaller and less scented flowers than the self-incompatible populations. However, flower size and scent emission rate did not differ between self-compatible populations with high and low capacity for autonomous self-pollination. Floral scent composition differed between self-compatible and self-incompatible populations, but also varied substantially among populations within the two categories. Conclusions: Our study demonstrates extensive variation in floral scent among populations of a geographically widespread species. Contrary to expectation, floral signalling did not differ between self-compatible populations with high and low capacity for autonomous self-pollination, indicating that dependence on pollinator attraction can only partly explain variation in floral signalling. Additional variation may reflect adaptation to other aspects of local environments, genetic drift, or a combination of these processes.
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| 6. |
- Petrén, Hampus, et al.
(författare)
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Innate preference hierarchies coupled with adult experience, rather than larval imprinting or transgenerational acclimation, determine host plant use in Pieris rapae
- 2021
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Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 11:1, s. 242-251
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Tidskriftsartikel (refereegranskat)abstract
- The evolution of host range drives diversification in phytophagous insects, and understanding the female oviposition choices is pivotal for understanding host specialization. One controversial mechanism for female host choice is Hopkins' host selection principle, where females are predicted to increase their preference for the host species they were feeding upon as larvae. A recent hypothesis posits that such larval imprinting is especially adaptive in combination with anticipatory transgenerational acclimation, so that females both allocate and adapt their offspring to their future host. We study the butterfly Pieris rapae, for which previous evidence suggests that females prefer to oviposit on host individuals of similar nitrogen content as the plant they were feeding upon as larvae, and where the offspring show higher performance on the mother's host type. We test the hypothesis that larval experience and anticipatory transgenerational effects influence female host plant acceptance (no-choice) and preference (choice) of two host plant species (Barbarea vulgaris and Berteroa incana) of varying nitrogen content. We then test the offspring performance on these hosts. We found no evidence of larval imprinting affecting female decision-making during oviposition, but that an adult female experience of egg laying in no-choice trials on the less-preferred host Be. incana slightly increased the P. rapae propensity to oviposit on Be. incana in subsequent choice trials. We found no transgenerational effects on female host acceptance or preference, but negative transgenerational effects on larval performance, because the offspring of P. rapae females that had developed on Be. incana as larvae grew slower on both hosts, and especially on Be. incana. Our results suggest that among host species, preferences are guided by hard-wired preference hierarchies linked to species-specific host traits and less affected by larval experience or transgenerational effects, which may be more important for females evaluating different host individuals of the same species.
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| 7. |
- Petrén, Hampus
(författare)
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The evolutionary ecology of plant reproductive diversity and floral signals : Mating system and floral scent in Arabis alpina
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Flowering plants display an extraordinary floral- and reproductive diversity. Variation in the size, shape, colour and scent of flowers, and in systems and strategies of mating, is ubiquitous in comparisons of different species, but also exists among different conspecific populations. Diversity in these characters is central to the evolution of flowering plants and the formation of new species. In this thesis, I use the arctic-alpine plant Arabis alpina to explore various causes of intraspecific variation in floral scent, and consequences of evolutionary shifts in plant mating system. By combining experiments in the greenhouse, genomic data and studies in the field, I examine how mating system, natural selection, genetic differentiation and phenotypic plasticity shape intraspecific floral scent variation, and investigate the impact of mating system shifts for the build-up of reproductive isolation. Comparing the floral scent of different A. alpina populations distributed across Europe, I found that self-compatible populations had a lower floral scent emission rate and partly different scent composition compared to self-incompatible populations. For both self-compatible and self-incompatible populations, there was limited phenotypic plasticity in floral scent, with some effect of nutrient availability, but not of water availability, on scent emission rates. Comparing the genomic and phenotypic differentiation among self-incompatible populations, it was evident that closely related populations could differ considerably in floral scent. Estimating selection on floral scent, I found some evidence that patterns of selection differed between populations. By crossing plants from self-compatible populations with plants from self-incompatible populations, I found considerable reproductive isolation, consistent with parental conflict over seed provisioning being higher in self-incompatible than in self-compatible populations. Taken together, the results of my thesis reveal some of the complex patterns behind floral scent diversification, and demonstrate the importance of mating system shifts for the evolution of floral signalling and reproductive isolation among flowering plants.
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| 8. |
- Schäpers, Alexander, et al.
(författare)
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Female fecundity variation affects reproducibility of experiments on host plant preference and acceptance in a phytophagous insect
- 2017
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Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 284:1849
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Tidskriftsartikel (refereegranskat)abstract
- Reproducibility is a scientific cornerstone. Many recent studies, however, describe a reproducibility crisis and call for assessments of reproducibility across scientific domains. Here, we explore the reproducibility of a classic ecological experiment—that of assessing female host plant preference and acceptance in phytophagous insects, a group in which host specialization is a key driver of diversification. We exposed multiple cohorts of Pieris napi butterflies from the same population to traditional host acceptance and preference tests on three Brassicaceae host species. Whereas the host plant rank order was highly reproducible, the propensity to oviposit on low-ranked hosts varied significantly even among cohorts exposed to similar conditions. Much variation could be attributed to among-cohort variation in female fecundity, a trait strongly correlated both to female size and to the size of the nuptial gift a female receives during mating. Small males provide small spermatophores, and in our experiment small females that mated with small males had a disproportionally low propensity to oviposit on low-ranked hosts. Hence, our results provide empirical support to the theoretical prediction that female host utilization is strongly affected by non-genetic, environmental variation, and that such variation can affect the reproducibility of ecological experiments even under seemingly identical conditions.
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