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Wróblewska A, Ostrowiecka B, Kotowicz J, Jermakowicz E, Tałałaj I, Szefer P. What are the drivers of female success in food-deceptive orchids? Ecol Evol 2024; 14:e11233. [PMID: 38646005 PMCID: PMC11026981 DOI: 10.1002/ece3.11233] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Revised: 03/05/2024] [Accepted: 03/20/2024] [Indexed: 04/23/2024] Open
Abstract
A large suite of floral signals, and environmental and biotic characteristics influence the behavior of pollinators, affecting the female success of food-deceptive orchids. In this study, we examined the many factors shaping the reproductive output of three orchid taxa: Dactylorhiza majalis, D. incarnata var. incarnata, and D. fuchsii. We applied a statistical model to correlate female success (number of fruit sets) with individual characteristics (plant and inflorescence height, number of flowers, and spur length), number of pollinaria removed, flowering time, and density of floral units of co-flowering rewarding plants. Our findings suggested that the broad spectrum of variations in Dactylorhiza's morphological traits, floral display, and flowering phenology within different environmental contexts has a significant impact on their reproductive success. The number of fruits increased with an increase in the number of pollinaria removed in the studied Dactylorhiza taxa. In contrast, a higher number of flowers per inflorescence and higher inflorescences in relation to individual height always decreased fruit set. We observed that low number of co-flowering rewarding plants in populations could affect the Dactylorhiza reproductive output as magnets and competitor plants. The synchronization of flowering, or lack thereof, between Dactylorhiza and rewarding plants can limit reproductive success. This demonstrates that the food deception strategy is multidirectional, and reproductive output can vary considerably both spatially and temporally within the context of this strategy.
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Affiliation(s)
- Ada Wróblewska
- Faculty of BiologyUniversity of BialystokBiałystokPoland
| | | | | | | | | | - Piotr Szefer
- Faculty of ScienceUniversity of South BohemiaČeské BudějoviceCzech Republic
- Biology Centre, Institute of EntomologyCzech Academy of SciencesČeské BudějoviceCzech Republic
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2
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Pontarp M, Runemark A, Friberg M, Opedal ØH, Persson AS, Wang L, Smith HG. Evolutionary plant-pollinator responses to anthropogenic land-use change: impacts on ecosystem services. Biol Rev Camb Philos Soc 2024; 99:372-389. [PMID: 37866400 DOI: 10.1111/brv.13026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 10/06/2023] [Accepted: 10/09/2023] [Indexed: 10/24/2023]
Abstract
Agricultural intensification at field and landscape scales, including increased use of agrochemicals and loss of semi-natural habitats, is a major driver of insect declines and other community changes. Efforts to understand and mitigate these effects have traditionally focused on ecological responses. At the same time, adaptations to pesticide use and habitat fragmentation in both insects and flowering plants show the potential for rapid evolution. Yet we lack an understanding of how such evolutionary responses may propagate within and between trophic levels with ensuing consequences for conservation of species and ecological functions in agroecosystems. Here, we review the literature on the consequences of agricultural intensification on plant and animal evolutionary responses and interactions. We present a novel conceptualization of evolutionary change induced by agricultural intensification at field and landscape scales and emphasize direct and indirect effects of rapid evolution on ecosystem services. We exemplify by focusing on economically and ecologically important interactions between plants and pollinators. We showcase available eco-evolutionary theory and plant-pollinator modelling that can improve predictions of how agricultural intensification affects interaction networks, and highlight available genetic and trait-focused methodological approaches. Specifically, we focus on how spatial genetic structure affects the probability of propagated responses, and how the structure of interaction networks modulates effects of evolutionary change in individual species. Thereby, we highlight how combined trait-based eco-evolutionary modelling, functionally explicit quantitative genetics, and genomic analyses may shed light on conditions where evolutionary responses impact important ecosystem services.
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Affiliation(s)
- Mikael Pontarp
- Department of Biology, Lund University, Sölvegatan 37, Lund, 22362, Sweden
| | - Anna Runemark
- Department of Biology, Lund University, Sölvegatan 37, Lund, 22362, Sweden
| | - Magne Friberg
- Department of Biology, Lund University, Sölvegatan 37, Lund, 22362, Sweden
| | - Øystein H Opedal
- Department of Biology, Lund University, Sölvegatan 37, Lund, 22362, Sweden
| | - Anna S Persson
- Centre for Environmental and Climate Science (CEC), Lund University, Sölvegatan 37, Lund, 22362, Sweden
| | - Lingzi Wang
- Centre for Environmental and Climate Science (CEC), Lund University, Sölvegatan 37, Lund, 22362, Sweden
- School of Mathematical Sciences, University of Southampton, 58 Salisbury Rd, Southampton, SO17 1BJ, UK
| | - Henrik G Smith
- Department of Biology, Lund University, Sölvegatan 37, Lund, 22362, Sweden
- Centre for Environmental and Climate Science (CEC), Lund University, Sölvegatan 37, Lund, 22362, Sweden
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3
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Brown KS, Caruso CM. The effect of experimental pollinator decline on pollinator-mediated selection on floral traits. Ecol Evol 2023; 13:e10706. [PMID: 37953983 PMCID: PMC10636310 DOI: 10.1002/ece3.10706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Accepted: 10/22/2023] [Indexed: 11/14/2023] Open
Abstract
Human-mediated environmental change, by reducing mean fitness, is hypothesized to strengthen selection on traits that mediate interactions among species. For example, human-mediated declines in pollinator populations are hypothesized to reduce mean seed production by increasing the magnitude of pollen limitation and thus strengthen pollinator-mediated selection on floral traits that increase pollinator attraction or pollen transfer efficiency. To test this hypothesis, we measured two female fitness components and six floral traits of Lobelia siphilitica plants exposed to supplemental hand-pollination, ambient open-pollination, or reduced open-pollination treatments. The reduced treatment simulated pollinator decline, while the supplemental treatment was used to estimate pollen limitation and pollinator-mediated selection. We found that plants in the reduced pollination treatment were significantly pollen limited, resulting in pollinator-mediated selection for taller inflorescences and more vibrant petals, both traits that could increase pollinator attraction. This contrasts with plants in the ambient pollination treatment, where reproduction was not pollen limited and there was not significant pollinator-mediated selection on any floral trait. Our results support the hypothesis that human-mediated environmental change can strengthen selection on traits of interacting species and suggest that these traits have the potential to evolve in response to changing environments.
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Affiliation(s)
- Kaitlyn S. Brown
- Department of Integrative BiologyUniversity of GuelphGuelphOntarioCanada
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Lozada-Gobilard S, Nielsen N, Sapir Y. Flower Size as an Honest Signal in Royal Irises ( Iris Section Oncocyclus, Iridaceae). PLANTS (BASEL, SWITZERLAND) 2023; 12:2978. [PMID: 37631189 PMCID: PMC10459770 DOI: 10.3390/plants12162978] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Revised: 08/06/2023] [Accepted: 08/15/2023] [Indexed: 08/27/2023]
Abstract
Flower traits, such as flower size or color changes, can act as honest signals indicating greater rewards such as nectar; however, nothing is known about shelter-rewarding systems. Large flowers of Royal irises offer overnight shelter as a reward to Eucera bees. A black patch might signal the entrance to the tunnel (shelter) and, together with the flower size, these might act as honest signals. We hypothesize that larger flowers and black patches indicate larger tunnels, and larger tunnels will increase pollinator visits, enhancing the plants' reproductive success. We measured seven species in a controlled environment and two species from three natural populations varying in flower size. Fruit and seed sets were assessed in these natural populations. We found a positive correlation between the flower, patch size, and tunnel volume, suggesting that the flowers and patch size act as honest signals, both under controlled conditions and in the wild. However, in natural populations, this positive relationship and its effect on fitness was population-specific. Flower size increased the fitness in YER I. petrana, and interactions between flower/patch size and tunnel size increased the fitness in YER and I. atropurpurea NET populations. This suggests that the honesty of the signal is positively selected in these two populations. This study supports the hypothesis that pollinator-mediated selection leads to the honest signaling of flower advertisement.
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Affiliation(s)
- Sissi Lozada-Gobilard
- The Botanical Garden, School of Plant Sciences and Food Security, G.S. Wise Faculty of Life Science, Tel Aviv University, Tel Aviv 69978, Israel; (N.N.); (Y.S.)
- Biodiversity Unit, Department of Biology, Lund University, 223 62 Lund, Sweden
| | - Nadine Nielsen
- The Botanical Garden, School of Plant Sciences and Food Security, G.S. Wise Faculty of Life Science, Tel Aviv University, Tel Aviv 69978, Israel; (N.N.); (Y.S.)
| | - Yuval Sapir
- The Botanical Garden, School of Plant Sciences and Food Security, G.S. Wise Faculty of Life Science, Tel Aviv University, Tel Aviv 69978, Israel; (N.N.); (Y.S.)
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Qiu Y, Yan X, Ma H, Wang Y, Yang R, Opedal ØH, Zhao Z. Proximity to oilseed rape fields affects plant pollination and pollinator‐mediated selection on a co‐flowering plant on the Tibetan Plateau. Evol Appl 2023; 16:814-823. [PMID: 37124085 PMCID: PMC10130553 DOI: 10.1111/eva.13538] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Revised: 12/18/2022] [Accepted: 02/11/2023] [Indexed: 03/08/2023] Open
Abstract
The ecological effects of mass-flowering crops on pollinator abundance and species richness of neighbouring habitats are well established, yet the potential evolutionary consequences remain unclear. We studied effects of proximity to a mass-flowering crop on the pollination of local co-flowering plants and on patterns of natural selection on a pollination-generalised plant on the Tibetan Plateau. We recorded pollinator visitation rates and community composition at different distances (near vs. far) to oilseed rape (Brassica napus) fields in two habitat types and quantified pollinator-mediated selection on attractive traits of Trollius ranunculoides. The proximity to oilseed rape increased pollinator visitation in neighbouring alpine meadows and changed pollinator composition in neighbouring shrub meadows. Trollius ranunculoides in the alpine meadow near oilseed rape received three times more pollinator visits (mainly bees) and consequently had a 16.5% increase in seed set but also received slightly more heterospecific pollen per stigma. In contrast, pollinator visitation to T. ranunculoides in the shrub meadow near oilseed rape was three times lower (mainly flies), leading to a 10.7% lower seed despite no effect on pollen deposition. The proximity to the oilseed rape field intensified pollinator-mediated selection on flower size and weakened selection on flower height of T. ranunculoides in the alpine meadow but did not affect phenotypic selection on either trait in the shrub meadow. Our study highlights context-dependent variation in plant-pollinator interactions close to mass-flowering oilseed rape, suggesting potential effects on the evolution of flower traits of native plants through altered pollinator-mediated selection. However, context dependence may make these effects difficult to predict.
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Affiliation(s)
- Yizhi Qiu
- State Key Laboratory of Herbage Improvement and Grassland Agro‐ecosystems, College of Ecology Lanzhou University Lanzhou China
- Northwest Institute of Eco‐Environment and Resources Chinese Academy of Sciences Lanzhou China
| | - Xiaoping Yan
- State Key Laboratory of Herbage Improvement and Grassland Agro‐ecosystems, College of Ecology Lanzhou University Lanzhou China
| | - Hui Ma
- State Key Laboratory of Herbage Improvement and Grassland Agro‐ecosystems, College of Ecology Lanzhou University Lanzhou China
| | - Yuxian Wang
- State Key Laboratory of Herbage Improvement and Grassland Agro‐ecosystems, College of Ecology Lanzhou University Lanzhou China
| | - Rong Yang
- Northwest Institute of Eco‐Environment and Resources Chinese Academy of Sciences Lanzhou China
| | - Øystein H. Opedal
- Department of Biology, Biodiversity Unit Lund University Lund Sweden
| | - Zhigang Zhao
- State Key Laboratory of Herbage Improvement and Grassland Agro‐ecosystems, College of Ecology Lanzhou University Lanzhou China
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Rodríguez-Otero C, Hedrén M, Friberg M, Opedal ØH. Analysis of trait-performance-fitness relationships reveals pollinator-mediated selection on orchid pollination traits. AMERICAN JOURNAL OF BOTANY 2023:e16128. [PMID: 36655508 DOI: 10.1002/ajb2.16128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Revised: 07/24/2022] [Accepted: 08/01/2022] [Indexed: 06/17/2023]
Abstract
PREMISE The role of pollinators in evolutionary floral divergence has spurred substantial effort into measuring pollinator-mediated phenotypic selection and its variation in space and time. For such estimates, the fitness consequences of pollination processes must be separated from other factors affecting fitness. METHODS We built a fitness function linking phenotypic traits of food-deceptive orchids to female reproductive success by including pollinator visitation and pollen deposition as intermediate performance components and used the fitness function to estimate the strength of pollinator-mediated selection through female reproductive success. We also quantified male performance as pollinarium removal and assessed similarity in trait effects on male and female performance. RESULTS The proportion of plants visited at least once by an effective pollinator was moderate to high, ranging from 53.7% to 85.1%. Tall, many-flowered plants were often more likely to be visited and pollinated. Given effective pollination, pollen deposition onto stigmas tended to be more likely for taller plants. Pollen deposition further depended on traits affecting the physical fit of pollinators to flowers (flower size, spur length), though the exact relationships varied in time and space. Using the fitness function to assess pollinator-mediated selection through female reproductive success acting on multiple traits, we found that selection varied detectably among taxa after accounting for sampling uncertainty. Across taxa, selection on most traits was stronger on average and more variable when pollination was less reliable. CONCLUSIONS These results support pollination-related trait-performance-fitness relationships and thus pollinator-mediated selection on traits functionally involved in the pollination process.
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Affiliation(s)
| | - Mikael Hedrén
- Department of Biology, Biodiversity Unit, Lund University, SE, 22362, Lund, Sweden
| | - Magne Friberg
- Department of Biology, Biodiversity Unit, Lund University, SE, 22362, Lund, Sweden
| | - Øystein H Opedal
- Department of Biology, Biodiversity Unit, Lund University, SE, 22362, Lund, Sweden
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7
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Gfrerer E, Laina D, Gibernau M, Comes HP, Hörger AC, Dötterl S. Variation in scent amount but not in composition correlates with pollinator visits within populations of deceptive Arum maculatum L. (Araceae). FRONTIERS IN PLANT SCIENCE 2023; 13:1046532. [PMID: 36699827 PMCID: PMC9869488 DOI: 10.3389/fpls.2022.1046532] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Accepted: 11/28/2022] [Indexed: 06/17/2023]
Abstract
Floral scent is vital for pollinator attraction and varies among and within plant species. However, little is known about how inter-individual variation in floral scent affects the abundance and composition of floral visitor assemblages within populations. Moreover, for deceptive plants it is predicted that intra-population variation in scent can be maintained by negative frequency-dependent selection, but empirical evidence is still lacking. To investigate the ecological and evolutionary relations between inter-individual scent variation (i.e., total emission and composition) and floral visitors in deceptive plants, we studied floral scent, visitor assemblages, and fruit set in two populations of fly-pollinated (Psychodidae, Sphaeroceridae; Diptera) and deceptive Arum maculatum from Austria (JOS) and northern Italy (DAO). By correlating individual data on floral scent and visitor assemblages, we show that inter-individual variation in floral scent partly explains variation in visitor assemblages. The quantity of floral scent emitted per individual correlated positively with visitor abundance in both populations but explained visitor composition only in DAO, where strongly scented inflorescences attracted more sphaerocerid flies. However, in each population, the composition of floral scent did not correlate with the composition of floral visitors. There was also no evidence of negative frequency-dependent selection on floral scent. Instead, in JOS, more frequent scent phenotypes attracted more pollinators and were more likely to set an infructescence than rarer ones. Our results show that floral scent, despite being key in pollinator attraction in A. maculatum, only partly explains variation in pollinator abundance and composition. Overall, this study is the first to shed light on the importance of inter-individual variation in floral scent in explaining floral visitor assemblages at the population level in a deceptive plant species.
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Affiliation(s)
- Eva Gfrerer
- Department of Environment and Biodiversity, Paris Lodron University of Salzburg, Salzburg, Austria
| | - Danae Laina
- Department of Environment and Biodiversity, Paris Lodron University of Salzburg, Salzburg, Austria
| | - Marc Gibernau
- Laboratory of Sciences for the Environment, Centre National de la Recherche Scientifique (CNRS) – University of Corsica, Ajaccio, France
| | - Hans Peter Comes
- Department of Environment and Biodiversity, Paris Lodron University of Salzburg, Salzburg, Austria
| | - Anja C. Hörger
- Department of Environment and Biodiversity, Paris Lodron University of Salzburg, Salzburg, Austria
| | - Stefan Dötterl
- Department of Environment and Biodiversity, Paris Lodron University of Salzburg, Salzburg, Austria
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8
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Wu Y, Liu G, Sletvold N, Duan X, Tong Z, Li Q. Soil water and nutrient availability interactively modify pollinator-mediated directional and correlational selection on floral display. THE NEW PHYTOLOGIST 2023; 237:672-683. [PMID: 36229922 DOI: 10.1111/nph.18537] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Accepted: 09/30/2022] [Indexed: 06/16/2023]
Abstract
The individual and combined effects of abiotic factors on pollinator-mediated selection on floral traits are not well documented. To examine potential interactive effects of water and nutrient availability on pollinator-mediated selection on three floral display traits of Primula tibetica, we manipulated pollination and nutrient availability in a factorial experiment, conducted at two common garden sites with different soil water content (natural vs addition). We found that both water and nutrient availability affected floral trait expression in P. tibetica and that hand pollination increased seed production most when both nutrient content and water content were high, indicating joint pollen and resource limitation. We documented selection on all floral traits, and pollinators contributed to directional and correlational selection on plant height and number of flowers. Soil water and nutrient availability interactively influenced the strength of both pollinator-mediated directional and correlational selection, with significant selection observed when nutrient or water availability was high, but not when none or both were added. The results suggest that resource limitation constrains the response of P. tibetica to among-individual variation in pollen receipt, that addition of nutrients or water leads to pollinator-mediated selection and that effects of the two abiotic factors are nonadditive.
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Affiliation(s)
- Yun Wu
- School of Architecture and Civil Engineering, Xihua University, Chengdu, 610039, China
| | - Guangli Liu
- College of Landscape Architecture, Sichuan Agricultural University, Chengdu, 611130, China
| | - Nina Sletvold
- Plant Ecology and Evolution, Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-752 36, Uppsala, Sweden
| | - Xuyu Duan
- College of Landscape Architecture, Sichuan Agricultural University, Chengdu, 611130, China
| | - Zhaoli Tong
- Yunnan Key Laboratory of Plant Reproductive Adaptation and Evolutionary Ecology, Yunnan University, Kunming, 650091, China
- Laboratory of Ecology and Evolutionary Biology, School of Ecology and Environmental Science, Yunnan University, Kunming, 650091, China
| | - Qingjun Li
- Yunnan Key Laboratory of Plant Reproductive Adaptation and Evolutionary Ecology, Yunnan University, Kunming, 650091, China
- Laboratory of Ecology and Evolutionary Biology, School of Ecology and Environmental Science, Yunnan University, Kunming, 650091, China
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9
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Huang X, Chen M, Wang L, Yang M, Yang N, Li Z, Duan Y. Phenotypic Selection in Halenia elliptica D. Don (Gentianaceae), an Alpine Biennial with Mixed Mating System. PLANTS 2022; 11:plants11111488. [PMID: 35684261 PMCID: PMC9183009 DOI: 10.3390/plants11111488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Revised: 05/30/2022] [Accepted: 05/30/2022] [Indexed: 11/16/2022]
Abstract
The transition from outcrossing to selfing is a common evolutionary trend in flowering plants, and floral traits change significantly with the evolution of selfing. Whether or not plant traits are subjected to selection remains an open question in species with mixed mating systems. We examined phenotypic selection in two populations of Halenia elliptica with different selfing rates. We found that the pollen–ovule ratio, seed size, plant height, spur length, and pollinator visitation rate in the population with the higher selfing rate were lower than those in the population with the lower selfing rate. Selfing provides reproductive assurance for populations when pollinator service is low, and the floral traits that are associated with selfing syndrome are evident in populations with a higher selfing rate but are subjected to weak selection in each of the two populations with different selfing rates. Directional selection for an early flowering time indicated that late blooming flowers could experience a risk of seed development in alpine environments, and for large plants, selection indicated that seed production could be limited by the available resources. The floral traits that are associated with pollinator attraction and specialization could be subjected to weak selection at the plant level as selfing evolves, and the selective pressures that are independent of pollinators might not change significantly; highlighting the selective biotic and abiotic pressures that shape the morphological traits of plant species and their independence from the mating system.
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Affiliation(s)
- Xiaojuan Huang
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi’an 710069, China;
- The Germplasm Bank of Wild Species, Institute of Tibetan Plateau Research at Kunming, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China; (M.C.); (L.W.); (N.Y.)
| | - Minyu Chen
- The Germplasm Bank of Wild Species, Institute of Tibetan Plateau Research at Kunming, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China; (M.C.); (L.W.); (N.Y.)
| | - Linlin Wang
- The Germplasm Bank of Wild Species, Institute of Tibetan Plateau Research at Kunming, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China; (M.C.); (L.W.); (N.Y.)
| | - Mingliu Yang
- School of Ecology and Environmental Science, Yunnan University, Kunming 650091, China;
| | - Nacai Yang
- The Germplasm Bank of Wild Species, Institute of Tibetan Plateau Research at Kunming, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China; (M.C.); (L.W.); (N.Y.)
| | - Zhonghu Li
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi’an 710069, China;
- Correspondence: (Z.L.); (Y.D.); Tel.: +86-29-88302411 (Z.L.); +86-87165223231 (Y.D.)
| | - Yuanwen Duan
- The Germplasm Bank of Wild Species, Institute of Tibetan Plateau Research at Kunming, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China; (M.C.); (L.W.); (N.Y.)
- Yunnan Lijiang Forest Ecosystem National Observation and Research Station, Kunming Institute of Botany, Chinese Academy of Sciences, Lijiang 674100, China
- Correspondence: (Z.L.); (Y.D.); Tel.: +86-29-88302411 (Z.L.); +86-87165223231 (Y.D.)
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10
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Lu NN, Ma Y, Hou M, Zhao ZG. The function of floral traits and phenotypic selection in Aconitum gymnandrum (Ranunculaceae). PLANT BIOLOGY (STUTTGART, GERMANY) 2021; 23:931-938. [PMID: 34396652 DOI: 10.1111/plb.13305] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Accepted: 06/07/2021] [Indexed: 06/13/2023]
Abstract
Floral evolution in angiosperms is thought to be driven by pollinator-mediated selection. Understanding flower integration and adaptation requires resolving the additive and nonadditive contributions of floral pollinator attraction and pollination efficiency traits to fitness components. In this study, a flower manipulation experiment with a factorial design was used to study the adaptive significance of galea height (a putative attraction trait) and entrance width (a putative efficiency trait) in Aconitum gymnandrum Maxim. flowers. Simultaneously, phenotypic selection analysis was conducted to examine selection by pollinators on galea height, entrance width, nectar production and plant height. Increased galea height increased the pollinator visitation rate, which confirmed its attractiveness function. Increasing floral entrance width by spreading the lower sepals increased the seed number per fruit without affecting pollinator visitation. This suggests a pollination efficiency role for the entrance width. The phenotypic selection analysis, however, did not provide evidence of pollinator-mediated selection for either of these traist, but it did for plant height. According to the manipulation treatment and correlational selection results, the combined variation in galea height and entrance width of A. gymnandrum flowers did not have nonadditive effects on female reproductive success. This study demonstrated the adaptive value of A. gymnandrum flowers through manipulation of an attractiveness trait and an efficiency trait. However, neither trait was associated with pollinator-mediated selection. A combination of manipulating traits and determining current phenotypic selection could help to elucidate the mechanism of selection on floral traits involved in different functions and flower integration.
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Affiliation(s)
- N-N Lu
- School of Life Science, North-West Normal University, Lanzhou, China
| | - Y Ma
- State Key Laboratory of Grassland and Agro-Ecosystems, School of Life Sciences, Lanzhou University, Lanzhou, China
| | - M Hou
- State Key Laboratory of Grassland and Agro-Ecosystems, School of Life Sciences, Lanzhou University, Lanzhou, China
| | - Z-G Zhao
- State Key Laboratory of Grassland and Agro-Ecosystems, School of Life Sciences, Lanzhou University, Lanzhou, China
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11
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Gfrerer E, Laina D, Gibernau M, Fuchs R, Happ M, Tolasch T, Trutschnig W, Hörger AC, Comes HP, Dötterl S. Floral Scents of a Deceptive Plant Are Hyperdiverse and Under Population-Specific Phenotypic Selection. FRONTIERS IN PLANT SCIENCE 2021; 12:719092. [PMID: 34630465 PMCID: PMC8500232 DOI: 10.3389/fpls.2021.719092] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Accepted: 08/12/2021] [Indexed: 06/13/2023]
Abstract
Floral scent is a key mediator in plant-pollinator interactions. However, little is known to what extent intraspecific scent variation is shaped by phenotypic selection, with no information yet in deceptive plants. In this study, we collected inflorescence scent and fruit set of the deceptive moth fly-pollinated Arum maculatum L. (Araceae) from six populations north vs. five populations south of the Alps, accumulating to 233 samples in total, and tested for differences in scent, fruit set, and phenotypic selection on scent across this geographic barrier. We recorded 289 scent compounds, the highest number so far reported in a single plant species. Most of the compounds occurred both north and south of the Alps; however, plants of the different regions emitted different absolute and relative amounts of scent. Fruit set was higher north than south of the Alps, and some, but not all differences in scent could be explained by differential phenotypic selection in northern vs. southern populations. This study is the first to provide evidence that floral scents of a deceptive plant are under phenotypic selection and that phenotypic selection is involved in shaping geographic patterns of floral scent in such plants. The hyperdiverse scent of A. maculatum might result from the imitation of various brood substrates of its pollinators.
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Affiliation(s)
- Eva Gfrerer
- Department of Biosciences, Paris Lodron University of Salzburg, Salzburg, Austria
| | - Danae Laina
- Department of Biosciences, Paris Lodron University of Salzburg, Salzburg, Austria
| | - Marc Gibernau
- Laboratory of Sciences for the Environment, CNRS – University of Corsica, Ajaccio, France
| | - Roman Fuchs
- Department of Biosciences, Paris Lodron University of Salzburg, Salzburg, Austria
| | - Martin Happ
- Lab for Intelligent Data Analytics Salzburg, Paris Lodron University of Salzburg, Salzburg, Austria
| | - Till Tolasch
- FG Tierökologie, University of Hohenheim, Stuttgart, Germany
| | - Wolfgang Trutschnig
- Department of Mathematics, Paris Lodron University of Salzburg, Salzburg, Austria
| | - Anja C. Hörger
- Department of Biosciences, Paris Lodron University of Salzburg, Salzburg, Austria
| | - Hans Peter Comes
- Department of Biosciences, Paris Lodron University of Salzburg, Salzburg, Austria
| | - Stefan Dötterl
- Department of Biosciences, Paris Lodron University of Salzburg, Salzburg, Austria
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12
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Trunschke J, Lunau K, Pyke GH, Ren ZX, Wang H. Flower Color Evolution and the Evidence of Pollinator-Mediated Selection. FRONTIERS IN PLANT SCIENCE 2021; 12:617851. [PMID: 34381464 PMCID: PMC8350172 DOI: 10.3389/fpls.2021.617851] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Accepted: 05/14/2021] [Indexed: 06/01/2023]
Abstract
The evolution of floral traits in animal-pollinated plants involves the interaction between flowers as signal senders and pollinators as signal receivers. Flower colors are very diverse, effect pollinator attraction and flower foraging behavior, and are hypothesized to be shaped through pollinator-mediated selection. However, most of our current understanding of flower color evolution arises from variation between discrete color morphs and completed color shifts accompanying pollinator shifts, while evidence for pollinator-mediated selection on continuous variation in flower colors within populations is still scarce. In this review, we summarize experiments quantifying selection on continuous flower color variation in natural plant populations in the context of pollinator interactions. We found that evidence for significant pollinator-mediated selection is surprisingly limited among existing studies. We propose several possible explanations related to the complexity in the interaction between the colors of flowers and the sensory and cognitive abilities of pollinators as well as pollinator behavioral responses, on the one hand, and the distribution of variation in color phenotypes and fitness, on the other hand. We emphasize currently persisting weaknesses in experimental procedures, and provide some suggestions for how to improve methodology. In conclusion, we encourage future research to bring together plant and animal scientists to jointly forward our understanding of the mechanisms and circumstances of pollinator-mediated selection on flower color.
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Affiliation(s)
- Judith Trunschke
- CAS Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China
| | - Klaus Lunau
- Institute of Sensory Ecology, Heinrich-Heine-University, Düsseldorf, Germany
| | - Graham H. Pyke
- CAS Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China
- Department of Biological Sciences, Macquarie University, Ryde, NSW, Australia
| | - Zong-Xin Ren
- CAS Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China
| | - Hong Wang
- CAS Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China
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13
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Albertsen E, Opedal ØH, Bolstad GH, Pérez-Barrales R, Hansen TF, Pélabon C, Armbruster WS. Using ecological context to interpret spatiotemporal variation in natural selection. Evolution 2020; 75:294-309. [PMID: 33230820 DOI: 10.1111/evo.14136] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 09/20/2020] [Accepted: 10/03/2020] [Indexed: 12/14/2022]
Abstract
Spatiotemporal variation in natural selection is expected, but difficult to estimate. Pollinator-mediated selection on floral traits provides a good system for understanding and linking variation in selection to differences in ecological context. We studied pollinator-mediated selection in five populations of Dalechampia scandens (Euphorbiaceae) in Costa Rica and Mexico. Using a nonlinear path-analytical approach, we assessed several functional components of selection, and linked variation in pollinator-mediated selection across time and space to variation in pollinator assemblages. After correcting for estimation error, we detected moderate variation in net selection on two out of four blossom traits. Both the opportunity for selection and the mean strength of selection decreased with increasing reliability of cross-pollination. Selection for pollinator attraction was consistently positive and stronger on advertisement than reward traits. Selection on traits affecting pollen transfer from the pollinator to the stigmas was strong only when cross-pollination was unreliable and there was a mismatch between pollinator and blossom size. These results illustrate how consideration of trait function and ecological context can facilitate both the detection and the causal understanding of spatiotemporal variation in natural selection.
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Affiliation(s)
- Elena Albertsen
- Norwegian Institute for Bioeconomy Research, Trondheim, 7031, Norway.,Centre for Biodiversity Dynamics, Department of Biology, Norwegian University of Science and Technology, Trondheim, 7491, Norway
| | - Øystein H Opedal
- Centre for Biodiversity Dynamics, Department of Biology, Norwegian University of Science and Technology, Trondheim, 7491, Norway.,Department of Biology, Lund University, Lund, SE-22362, Sweden
| | - Geir H Bolstad
- Norwegian Institute for Nature Research (NINA), Trondheim, 7485, Norway
| | - Rocío Pérez-Barrales
- School of Biological Sciences, University of Portsmouth, Portsmouth, PO1 2DY, United Kingdom
| | - Thomas F Hansen
- Centre for Ecological and Evolutionary Synthesis, Department of Biology, University of Oslo, Oslo, 0316, Norway
| | - Christophe Pélabon
- Centre for Biodiversity Dynamics, Department of Biology, Norwegian University of Science and Technology, Trondheim, 7491, Norway
| | - W Scott Armbruster
- School of Biological Sciences, University of Portsmouth, Portsmouth, PO1 2DY, United Kingdom.,Institute of Arctic Biology, University of Alaska, Fairbanks, Alaska, 99775, USA
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14
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Joffard N, Le Roncé I, Langlois A, Renoult J, Buatois B, Dormont L, Schatz B. Floral trait differentiation in Anacamptis coriophora: Phenotypic selection on scents, but not on colour. J Evol Biol 2020; 33:1028-1038. [PMID: 32500947 DOI: 10.1111/jeb.13657] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Revised: 05/14/2020] [Accepted: 05/23/2020] [Indexed: 01/26/2023]
Abstract
Current divergent selection may promote floral trait differentiation among conspecific populations in flowering plants. However, whether this applies to complex traits such as colour or scents has been little studied, even though these traits often vary within species. In this study, we compared floral colour and odour as well as selective pressures imposed upon these traits among seven populations belonging to three subspecies of the widespread, generalist orchid Anacamptis coriophora. Colour was characterized using calibrated photographs, and scents were sampled using dynamic headspace extraction and analysed using gas chromatography-mass spectrometry. We then quantified phenotypic selection exerted on these traits by regressing fruit set values on floral trait values. We showed that the three studied subspecies were characterized by different floral colour and odour, with one of the two predominant floral volatiles emitted by each subspecies being taxon-specific. Plant size was positively correlated with fruit set in most populations, whereas we found no apparent link between floral colour and female reproductive success. We detected positive selection on several taxon-specific compounds in A. coriophora subsp. fragrans, whereas no selection was found on floral volatiles of A. coriophora subsp. coriophora and A. coriophora subsp. martrinii. This study is one of the first to document variation in phenotypic selection exerted on floral scents among conspecific populations. Our results suggest that selection could contribute to ongoing chemical divergence among A. coriophora subspecies.
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Affiliation(s)
- Nina Joffard
- Centre d'Ecologie Fonctionnelle et Evolutive, EPHE-PSL, CNRS, Univ. Montpellier, Univ. Paul Valéry Montpellier 3, IRD, Montpellier, France
- Evolutionsbiologiskt Centrum (EBC), Uppsala, Sweden
| | - Iris Le Roncé
- Centre d'Ecologie Fonctionnelle et Evolutive, EPHE-PSL, CNRS, Univ. Montpellier, Univ. Paul Valéry Montpellier 3, IRD, Montpellier, France
- Département de biologie, École Normale Supérieure de Lyon, Lyon, France
| | - Alban Langlois
- Centre d'Ecologie Fonctionnelle et Evolutive, EPHE-PSL, CNRS, Univ. Montpellier, Univ. Paul Valéry Montpellier 3, IRD, Montpellier, France
- Université Toulouse III Paul Sabatier, Toulouse, France
| | - Julien Renoult
- Centre d'Ecologie Fonctionnelle et Evolutive, EPHE-PSL, CNRS, Univ. Montpellier, Univ. Paul Valéry Montpellier 3, IRD, Montpellier, France
| | - Bruno Buatois
- Centre d'Ecologie Fonctionnelle et Evolutive, EPHE-PSL, CNRS, Univ. Montpellier, Univ. Paul Valéry Montpellier 3, IRD, Montpellier, France
| | - Laurent Dormont
- Centre d'Ecologie Fonctionnelle et Evolutive, EPHE-PSL, CNRS, Univ. Montpellier, Univ. Paul Valéry Montpellier 3, IRD, Montpellier, France
| | - Bertrand Schatz
- Centre d'Ecologie Fonctionnelle et Evolutive, EPHE-PSL, CNRS, Univ. Montpellier, Univ. Paul Valéry Montpellier 3, IRD, Montpellier, France
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15
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Chen M, Zuo XA, Zhao XY. Comparative Floral Characters, Pollinator Limitation, and Pollination Success in Different Habitats of Caragana microphylla Lam. Front Ecol Evol 2020. [DOI: 10.3389/fevo.2020.00170] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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16
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Chapurlat E, Le Roncé I, Ågren J, Sletvold N. Divergent selection on flowering phenology but not on floral morphology between two closely related orchids. Ecol Evol 2020; 10:5737-5747. [PMID: 32607187 PMCID: PMC7319237 DOI: 10.1002/ece3.6312] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Revised: 03/09/2020] [Accepted: 03/30/2020] [Indexed: 11/08/2022] Open
Abstract
Closely related species often differ in traits that influence reproductive success, suggesting that divergent selection on such traits contribute to the maintenance of species boundaries. Gymnadenia conopsea ss. and Gymnadenia densiflora are two closely related, perennial orchid species that differ in (a) floral traits important for pollination, including flowering phenology, floral display, and spur length, and (b) dominant pollinators. If plant-pollinator interactions contribute to the maintenance of trait differences between these two taxa, we expect current divergent selection on flowering phenology and floral morphology between the two species. We quantified phenotypic selection via female fitness in one year on flowering start, three floral display traits (plant height, number of flowers, and corolla size) and spur length, in six populations of G. conopsea s.s. and in four populations of G. densiflora. There was indication of divergent selection on flowering start in the expected direction, with selection for earlier flowering in two populations of the early-flowering G. conopsea s.s. and for later flowering in one population of the late-flowering G. densiflora. No divergent selection on floral morphology was detected, and there was no significant stabilizing selection on any trait in the two species. The results suggest ongoing adaptive differentiation of flowering phenology, strengthening this premating reproductive barrier between the two species. Synthesis: This study is among the first to test whether divergent selection on floral traits contribute to the maintenance of species differences between closely related plants. Phenological isolation confers a substantial potential for reproductive isolation, and divergent selection on flowering time can thus greatly influence reproductive isolation and adaptive differentiation.
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Affiliation(s)
- Elodie Chapurlat
- Plant Ecology and EvolutionDepartment of Ecology and GeneticsEvolutionary Biology CentreUppsala UniversityUppsalaSweden
| | - Iris Le Roncé
- Plant Ecology and EvolutionDepartment of Ecology and GeneticsEvolutionary Biology CentreUppsala UniversityUppsalaSweden
- Master BioSciencesÉcole Normale Supérieure de LyonUniversité Claude Bernard Lyon 1Université de LyonLyonFrance
| | - Jon Ågren
- Plant Ecology and EvolutionDepartment of Ecology and GeneticsEvolutionary Biology CentreUppsala UniversityUppsalaSweden
| | - Nina Sletvold
- Plant Ecology and EvolutionDepartment of Ecology and GeneticsEvolutionary Biology CentreUppsala UniversityUppsalaSweden
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17
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Eisen KE, Wruck AC, Geber MA. Floral density and co‐occurring congeners alter patterns of selection in annual plant communities*. Evolution 2020; 74:1682-1698. [DOI: 10.1111/evo.13960] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 02/13/2020] [Accepted: 03/01/2020] [Indexed: 11/29/2022]
Affiliation(s)
- Katherine E. Eisen
- Department of Ecology and Evolutionary Biology Cornell University Ithaca New York 14853
| | - Amy C. Wruck
- Department of Ecology and Evolutionary Biology Cornell University Ithaca New York 14853
| | - Monica A. Geber
- Department of Ecology and Evolutionary Biology Cornell University Ithaca New York 14853
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18
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Tye M, Dahlgren JP, Sletvold N. Pollen limitation in a single year is not compensated by future reproduction. Oecologia 2020; 192:989-997. [PMID: 32078036 PMCID: PMC7165156 DOI: 10.1007/s00442-020-04623-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Accepted: 02/08/2020] [Indexed: 11/30/2022]
Abstract
Seed production is critical to the persistence of most flowering plant populations, but may be strongly pollen limited. To what extent long-lived plants can compensate pollen limitation by increasing future reproduction is poorly understood. We tested for compensation in two Dactylorhiza species that differ in reproductive investment by experimentally reducing and increasing pollination in two independent annual cohorts and monitoring demographic responses in the subsequent 2 years for the 2014 cohort and in 1 year for the 2015 cohort. Demographic rates in the second year were significantly affected by pollination treatment in both species, but specific responses differed both between species and years. There was no effect of pollination treatment on demographic responses in the third year. In sum, effects were too weak to make up for the lost reproduction; total fruit production across all 3 years was by far highest in the increased pollination treatment in both species. These results show that long-lived plants do not necessarily compensate for pollen limitation by increasing future reproduction. It further suggests that even periodic declines in pollination rates may have severe demographic consequences, particularly in populations where germination is not density dependent. This has implications for predicting plant population viability in response to changes in pollination intensity.
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Affiliation(s)
- Matthew Tye
- Department of Ecology and Genetics, Uppsala University, SE-752 36, Uppsala, Sweden
| | - Johan P Dahlgren
- Department of Biology and The SDU Interdisciplinary Centre on Population Dynamics, University of Southern Denmark, 5230, Odense, Denmark
| | - Nina Sletvold
- Department of Ecology and Genetics, Uppsala University, SE-752 36, Uppsala, Sweden.
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19
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Trunschke J, Sletvold N, Ågren J. Manipulation of trait expression and pollination regime reveals the adaptive significance of spur length. Evolution 2020; 74:597-609. [PMID: 31944284 DOI: 10.1111/evo.13927] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2019] [Revised: 12/21/2019] [Accepted: 01/07/2020] [Indexed: 12/13/2022]
Abstract
Understanding the mechanisms of adaptive population differentiation requires that both the functional and adaptive significance of divergent traits are characterized in contrasting environments. Here, we (a) determined the effects of floral spur length on pollen removal and receipt using plants with artificial spurs representing the species-wide variation in length, and (b) quantified pollinator-mediated selection on spur length and three traits contributing to floral display in two populations each of the short-spurred and the long-spurred ecotype of the orchid Platanthera bifolia. Both pollen receipt and removal reached a maximum at 28-29 mm long spurs in a short-spurred population visited by short-tongued moths. In contrast, pollen receipt increased linearly across the tested range (4-52 mm) and pollen removal was unrelated to spur length in a long-spurred population predominantly visited by a long-tongued moth. The experimentally documented effects on pollen transfer were not reflected in pollinator-mediated selection through female fitness or pollen removal indicating that the natural within-population variation in spur length was insufficient to result in detectable variation in pollen limitation. Our study illustrates how combining trait manipulation with analysis of causes and strength of phenotypic selection can illuminate the functional and adaptive significance of trait expression when trait variation is limited.
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Affiliation(s)
- Judith Trunschke
- Plant Ecology and Evolution, Department of Ecology and Genetics, EBC, Uppsala University, SE-752 36, Uppsala, Sweden.,Current Address: Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, P. R. China
| | - Nina Sletvold
- Plant Ecology and Evolution, Department of Ecology and Genetics, EBC, Uppsala University, SE-752 36, Uppsala, Sweden
| | - Jon Ågren
- Plant Ecology and Evolution, Department of Ecology and Genetics, EBC, Uppsala University, SE-752 36, Uppsala, Sweden
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20
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Zhang B, Claßen-Bockhoff R. Sex-differential reproduction success and selection on floral traits in gynodioecious Salvia pratensis. BMC PLANT BIOLOGY 2019; 19:375. [PMID: 31455268 PMCID: PMC6712674 DOI: 10.1186/s12870-019-1972-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Accepted: 08/13/2019] [Indexed: 06/10/2023]
Abstract
BACKGROUND Gynodioecy, a sexual system with hermaphrodite and female individuals in a population, raises the question how the two sexual morphs are maintained. Salvia pratensis is a gynodioecious species featured by its modified stamens that act as a lever mechanism in pollination. Given sexual dimorphism in floral traits of the species, it is predictable that two sexual morphs differ in their interplay with pollinators and thus in their fitness. In this study, we investigated sex-specific reproduction success and floral adaptation in a population of S. pratensis. RESULTS We found that two sexual morphs in S. pratensis distinctly differed in their floral proportions. Female flowers fitted better to the pollinators than hermaphrodites in terms of touching the stigmas when being probed, and hence were more efficient in pollen deposition. Floral traits overall underwent stronger selection in the population, with stigma position and corolla length subject to disruptive selection mediated by different body-sized bumble bees; some selections on floral traits were significantly different in the strength, even opposite in the direction between two morphs. Flower production tended to be under correlational selection with floral structural traits, implying that a large plant with many flowers did not show an advantage in fitness unless its flower construction mechanically matched the pollinators well. CONCLUSIONS In conclusion, the pollinator-mediated selection likely played an important role in the evolution and maintenance of sexual dimorphism in the gynodioecious S. pratensis; and sex-divergent mechanical interaction with pollinators served as a critical mechanism by which female individuals were maintained in the population with a female advantage in pollen deposition efficiency (i.e. receiving pollen).
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Affiliation(s)
- Bo Zhang
- Key Laboratory of Grassland Ecosystem of Ministry of Education, and Sino-U.S. Centers for Grazingland Ecosystem Sustainability, College of Grassland Science, Gansu Agricultural University, Lanzhou, 730070, China.
- Institute of Organismic and Molecular Evolution, Johannes Gutenberg-University, 55099, Mainz, Germany.
| | - Regine Claßen-Bockhoff
- Institute of Organismic and Molecular Evolution, Johannes Gutenberg-University, 55099, Mainz, Germany.
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21
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Chapurlat E, Ågren J, Anderson J, Friberg M, Sletvold N. Conflicting selection on floral scent emission in the orchid Gymnadenia conopsea. THE NEW PHYTOLOGIST 2019; 222:2009-2022. [PMID: 30767233 DOI: 10.1111/nph.15747] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Accepted: 02/04/2019] [Indexed: 06/09/2023]
Abstract
Floral scent is a crucial trait for pollinator attraction. Yet only a handful of studies have estimated selection on scent in natural populations and no study has quantified the relative importance of pollinators and other agents of selection. In the fragrant orchid Gymnadenia conopsea, we used electroantennographic data to identify floral scent compounds detected by local pollinators and quantified pollinator-mediated selection on emission rates of 10 target compounds as well as on flowering start, visual display and spur length. Nocturnal pollinators contributed more to reproductive success than diurnal pollinators, but there was significant pollinator-mediated selection on both diurnal and nocturnal scent emission. Pollinators selected for increased emission of two compounds and reduced emission of two other compounds, none of which were major constituents of the total bouquet. In three cases, pollinator-mediated selection was opposed by nonpollinator-mediated selection, leading to weaker or no detectable net selection. Our study demonstrates that minor scent compounds can be targets of selection, that pollinators do not necessarily favour stronger scent signalling, and that some scent compounds are subject to conflicting selection from pollinators and other agents of selection. Hence, including floral scent traits into selection analysis is important for understanding the mechanisms behind floral evolution.
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Affiliation(s)
- Elodie Chapurlat
- Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, 752 36, Uppsala, Sweden
| | - Jon Ågren
- Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, 752 36, Uppsala, Sweden
| | - Joseph Anderson
- Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, 752 36, Uppsala, Sweden
| | - Magne Friberg
- Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, 752 36, Uppsala, Sweden
- Department of Biology, Lund University, SE-223 62, Lund, Sweden
| | - Nina Sletvold
- Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, 752 36, Uppsala, Sweden
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22
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Parachnowitsch AL, Manson JS, Sletvold N. Evolutionary ecology of nectar. ANNALS OF BOTANY 2019; 123:247-261. [PMID: 30032269 PMCID: PMC6344224 DOI: 10.1093/aob/mcy132] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2018] [Accepted: 06/16/2018] [Indexed: 05/24/2023]
Abstract
Background Floral nectar is an important determinant of plant-pollinator interactions and an integral component of pollination syndromes, suggesting it is under pollinator-mediated selection. However, compared to floral display traits, we know little about the evolutionary ecology of nectar. Combining a literature review with a meta-analysis approach, we summarize the evidence for heritable variation in nectar traits and link this variation to pollinator response and plant fitness. We further review associations between nectar traits and floral signals and discuss them in the context of honest signalling and targets of selection. Scope Although nectar is strongly influenced by environmental factors, heritable variation in nectar production rate has been documented in several populations (mean h2 = 0.31). Almost nothing is known about heritability of other nectar traits, such as sugar and amino acid concentrations. Only a handful of studies have quantified selection on nectar traits, and few find statistically significant selection. Pollinator responses to nectar traits indicate they may drive selection, but studies tying pollinator preferences to plant fitness are lacking. So far, only one study conclusively identified pollinators as selective agents on a nectar trait, and the role of microbes, herbivores, nectar robbers and abiotic factors in nectar evolution is largely hypothetical. Finally, there is a trend for positive correlations among floral cues and nectar traits, indicating honest signalling of rewards. Conclusions Important progress can be made by studies that quantify current selection on nectar in natural populations, as well as experimental approaches that identify the target traits and selective agents involved. Signal-reward associations suggest that correlational selection may shape evolution of nectar traits, and studies exploring these more complex forms of natural selection are needed. Many questions about nectar evolution remain unanswered, making this a field ripe for future research.
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Affiliation(s)
- Amy L Parachnowitsch
- Plant Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden
- Department of Biology, University of New Brunswick, Fredericton, New Brunswick, Canada
| | - Jessamyn S Manson
- Department of Biology, University of Virginia, Charlottesville, VA, USA
| | - Nina Sletvold
- Plant Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden
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23
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Caruso CM, Eisen KE, Martin RA, Sletvold N. A meta-analysis of the agents of selection on floral traits. Evolution 2018; 73:4-14. [PMID: 30411337 DOI: 10.1111/evo.13639] [Citation(s) in RCA: 86] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2018] [Revised: 10/23/2018] [Accepted: 10/24/2018] [Indexed: 01/03/2023]
Abstract
Floral traits are hypothesized to evolve primarily in response to selection by pollinators. However, selection can also be mediated by other environmental factors. To understand the relative importance of pollinator-mediated selection and its variation among trait and pollinator types, we analyzed directional selection gradients on floral traits from experiments that manipulated the environment to identify agents of selection. Pollinator-mediated selection was stronger than selection by other biotic factors (e.g., herbivores), but similar in strength to selection by abiotic factors (e.g., soil water), providing partial support for the hypothesis that floral traits evolve primarily in response to pollinators. Pollinator-mediated selection was stronger on pollination efficiency traits than on other trait types, as expected if efficiency traits affect fitness via interactions with pollinators, but other trait types also affect fitness via other environmental factors. In addition to varying among trait types, pollinator-mediated selection varied among pollinator taxa: selection was stronger when bees, long-tongued flies, or birds were the primary visitors than when the primary visitors were Lepidoptera or multiple animal taxa. Finally, reducing pollinator access to flowers had a relatively small effect on selection on floral traits, suggesting that anthropogenic declines in pollinator populations would initially have modest effects on floral evolution.
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Affiliation(s)
- Christina M Caruso
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
| | - Katherine E Eisen
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada.,Current Address: Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, New York, 14853
| | - Ryan A Martin
- Department of Biology, Case Western Reserve University, Cleveland, Ohio, 44106
| | - Nina Sletvold
- Department of Ecology and Genetics, Uppsala University, Uppsala, 751 05, Sweden
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24
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Santangelo JS, Thompson KA, Johnson MTJ. Herbivores and plant defences affect selection on plant reproductive traits more strongly than pollinators. J Evol Biol 2018; 32:4-18. [PMID: 30339305 DOI: 10.1111/jeb.13392] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Revised: 10/10/2018] [Accepted: 10/15/2018] [Indexed: 01/14/2023]
Abstract
Pollinators and herbivores can both affect the evolutionary diversification of plant reproductive traits. However, plant defences frequently alter antagonistic and mutualistic interactions, and therefore, variation in plant defences may alter patterns of herbivore- and pollinator-mediated selection on plant traits. We tested this hypothesis by conducting a common garden field experiment using 50 clonal genotypes of white clover (Trifolium repens) that varied in a Mendelian-inherited chemical antiherbivore defence-the production of hydrogen cyanide (HCN). To evaluate whether plant defences alter herbivore- and/or pollinator-mediated selection, we factorially crossed chemical defence (25 cyanogenic and 25 acyanogenic genotypes), herbivore damage (herbivore suppression) and pollination (hand pollination). We found that herbivores weakened selection for increased inflorescence production, suggesting that large displays are costly in the presence of herbivores. In addition, herbivores weakened selection on flower size but only among acyanogenic plants, suggesting that plant defences reduce the strength of herbivore-mediated selection. Pollinators did not independently affect selection on any trait, although pollinators weakened selection for later flowering among cyanogenic plants. Overall, cyanogenic plant defences consistently increased the strength of positive directional selection on reproductive traits. Herbivores and pollinators both strengthened and weakened the strength of selection on reproductive traits, although herbivores imposed ~2.7× stronger selection than pollinators across all traits. Contrary to the view that pollinators are the most important agents of selection on reproductive traits, our data show that selection on reproductive traits is driven primarily by variation in herbivory and plant defences in this system.
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Affiliation(s)
- James S Santangelo
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada.,Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada
| | - Ken A Thompson
- Biodiversity Research Centre & Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Marc T J Johnson
- Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada
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25
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Caruso CM, Martin RA, Sletvold N, Morrissey MB, Wade MJ, Augustine KE, Carlson SM, MacColl ADC, Siepielski AM, Kingsolver JG. What Are the Environmental Determinants of Phenotypic Selection? A Meta-analysis of Experimental Studies. Am Nat 2017; 190:363-376. [DOI: 10.1086/692760] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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26
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Scopece G, Juillet N, Lexer C, Cozzolino S. Fluctuating selection across years and phenotypic variation in food-deceptive orchids. PeerJ 2017; 5:e3704. [PMID: 28852594 PMCID: PMC5572944 DOI: 10.7717/peerj.3704] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Accepted: 07/27/2017] [Indexed: 11/20/2022] Open
Abstract
Nectarless flowers that deceive pollinators offer an opportunity to study asymmetric plant-insect interactions. Orchids are a widely used model for studying these interactions because they encompass several thousand species adopting deceptive pollination systems. High levels of intra-specific phenotypic variation have been reported in deceptive orchids, suggesting a reduced consistency of pollinator-mediated selection on their floral traits. Nevertheless, several studies report on widespread directional selection mediated by pollinators even in these deceptive orchids. In this study we test the hypothesis that the observed selection can fluctuate across years in strength and direction thus likely contributing to the phenotypic variability of this orchid group. We performed a three-year study estimating selection differentials and selection gradients for nine phenotypic traits involved in insect attraction in two Mediterranean orchid species, namely Orchis mascula and O. pauciflora, both relying on a well-described food-deceptive pollination strategy. We found weak directional selection and marginally significant selection gradients in the two investigated species with significant intra-specific differences in selection differentials across years. Our data do not link this variation with a specific environmental cause, but our results suggest that pollinator-mediated selection in food-deceptive orchids can change in strength and in direction over time. In perennial plants, such as orchids, different selection differentials in the same populations in different flowering seasons can contribute to the maintenance of phenotypic variation often reported in deceptive orchids.
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Affiliation(s)
- Giovanni Scopece
- Department of Biology, University of Naples Federico II, Naples, Italy
| | - Nicolas Juillet
- UMR Peuplements Végétaux et Bioagresseurs en Milieu Tropical, Université de la Réunion, Pôle de Protection des Plantes, Saint Pierre, La Réunion, France
| | - Christian Lexer
- Department of Botany and Biodiversity Research, University of Vienna, Vienna, Austria
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27
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Emel SL, Franks SJ, Spigler RB. Phenotypic selection varies with pollination intensity across populations of Sabatia angularis. THE NEW PHYTOLOGIST 2017; 215:813-824. [PMID: 28542815 DOI: 10.1111/nph.14608] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Accepted: 04/05/2017] [Indexed: 06/07/2023]
Abstract
Pollinators are considered primary selective agents acting on plant traits, and thus variation in the strength of the plant-pollinator interaction might drive variation in the opportunity for selection and selection intensity across plant populations. Here, we examine whether these critical evolutionary parameters covary with pollination intensity across wild populations of the biennial Sabatia angularis. We quantified pollination intensity in each of nine S. angularis populations as mean stigmatic pollen load per population. For female fitness and three components, fruit number, fruit set (proportion of flowers setting fruit) and number of seeds per fruit, we evaluated whether the opportunity for selection varied with pollination intensity. We used phenotypic selection analyses to test for interactions between pollination intensity and selection gradients for five floral traits, including flowering phenology. The opportunity for selection via fruit set and seeds per fruit declined significantly with increasing pollen receipt, as expected. We demonstrated significant directional selection on multiple traits across populations. We also found that selection intensity for all traits depended on pollination intensity. Consistent with general theory about the relationship between biotic interaction strength and the intensity of selection, our study suggests that variation in pollination intensity drives variation in selection across S. angularis populations.
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Affiliation(s)
- Sarah L Emel
- Department of Biology, Temple University, BioLife Building, 1900 N. 12th St, Philadelphia, PA, 19122, USA
| | - Steven J Franks
- Department of Biological Sciences, Fordham University, Larkin Hall, 441 E. Fordham Road, Bronx, NY, 20458, USA
| | - Rachel B Spigler
- Department of Biology, Temple University, BioLife Building, 1900 N. 12th St, Philadelphia, PA, 19122, USA
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28
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Johnston MO, Bartkowska MP. Individual pollen limitation, phylogeny and selection. THE NEW PHYTOLOGIST 2017; 214:909-912. [PMID: 28397359 DOI: 10.1111/nph.14562] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Affiliation(s)
- Mark O Johnston
- Department of Biology, Dalhousie University, Halifax, NS, B3H 4R2, Canada
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29
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Trunschke J, Sletvold N, Ågren J. Interaction intensity and pollinator-mediated selection. THE NEW PHYTOLOGIST 2017; 214:1381-1389. [PMID: 28240377 DOI: 10.1111/nph.14479] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Accepted: 01/15/2017] [Indexed: 05/26/2023]
Abstract
In animal-pollinated plants, the opportunity for selection and the strength of pollinator-mediated selection are expected to increase with the degree of pollen limitation. However, whether differences in pollen limitation can explain variation in pollinator-mediated and net selection among animal-pollinated species is poorly understood. In the present study, we quantified pollen limitation, variance in relative fitness and pollinator-mediated selection on five traits important for pollinator attraction (flowering start, plant height, flower number, flower size) and pollination efficiency (spur length) in natural populations of 12 orchid species. Pollinator-mediated selection was quantified by subtracting estimates of selection gradients for plants receiving supplemental hand-pollination from estimates obtained for open-pollinated control plants. Mean pollen limitation ranged from zero to 0.96. Opportunity for selection, pollinator-mediated selection and net selection were all positively related to pollen limitation, whereas nonpollinator-mediated selection was not. Opportunity for selection varied five-fold, strength of pollinator-mediated selection varied three-fold and net selection varied 1.5-fold among species. Supplemental hand-pollination reduced both opportunity for selection and selection on floral traits. The results show that the intensity of biotic interactions is an important determinant of the selection regime, and indicate that the potential for pollinator-mediated selection and divergence in floral traits is particularly high in species that are strongly pollen-limited.
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Affiliation(s)
- Judith Trunschke
- Plant Ecology and Evolution, Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18 D, Uppsala, SE-752 36, Sweden
| | - Nina Sletvold
- Plant Ecology and Evolution, Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18 D, Uppsala, SE-752 36, Sweden
| | - Jon Ågren
- Plant Ecology and Evolution, Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18 D, Uppsala, SE-752 36, Sweden
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30
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Sapir Y. Pollinator‐mediated selection is better detected when controlling for resource limitation. Funct Ecol 2017. [DOI: 10.1111/1365-2435.12800] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yuval Sapir
- The Botanical Garden School of Plant Sciences and Food Security Tel Aviv University Ramat Aviv Tel Aviv69978 Israel
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31
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Sletvold N, Ågren J. Experimental reduction in interaction intensity strongly affects biotic selection. Ecology 2016; 97:3091-3098. [DOI: 10.1002/ecy.1554] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Revised: 07/15/2016] [Accepted: 07/21/2016] [Indexed: 10/21/2022]
Affiliation(s)
- Nina Sletvold
- Plant Ecology and Evolution; Department of Ecology and Genetics; Evolutionary Biology Centre; Uppsala University; Norbyvägen 18 D, SE-752 36 Uppsala Sweden
| | - Jon Ågren
- Plant Ecology and Evolution; Department of Ecology and Genetics; Evolutionary Biology Centre; Uppsala University; Norbyvägen 18 D, SE-752 36 Uppsala Sweden
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32
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Affiliation(s)
- Nina Sletvold
- Plant Ecology and Evolution Department of Ecology and Genetics Evolutionary Biology Centre Uppsala University Norbyvägen 18 D SE‐752 36 Uppsala Sweden
| | - Matthew Tye
- Plant Ecology and Evolution Department of Ecology and Genetics Evolutionary Biology Centre Uppsala University Norbyvägen 18 D SE‐752 36 Uppsala Sweden
| | - Jon Ågren
- Plant Ecology and Evolution Department of Ecology and Genetics Evolutionary Biology Centre Uppsala University Norbyvägen 18 D SE‐752 36 Uppsala Sweden
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33
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Sletvold N, Trunschke J, Smit M, Verbeek J, Ågren J. Strong pollinator-mediated selection for increased flower brightness and contrast in a deceptive orchid. Evolution 2016; 70:716-24. [PMID: 26878831 DOI: 10.1111/evo.12881] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Revised: 01/12/2016] [Accepted: 01/27/2016] [Indexed: 11/30/2022]
Abstract
Contrasting flower color patterns that putatively attract or direct pollinators toward a reward are common among angiosperms. In the deceptive orchid Anacamptis morio, the lower petal, which makes up most of the floral display, has a light central patch with dark markings. Within populations, there is pronounced variation in petal brightness, patch size, amount of dark markings, and contrast between patch and petal margin. We tested whether pollinators mediate selection on these color traits and on morphology (plant height, number of flowers, corolla size, spur length), and whether selection is consistent with facilitated or negative frequency-dependent pollination. Pollinators mediated strong selection for increased petal brightness (Δβpoll = 0.42) and contrast (Δβpoll = 0.51). Pollinators also tended to mediate stabilizing selection on brightness (Δγpoll = -0.27, n.s.) favoring the most common phenotype in the population. Selection for reduced petal brightness among hand-pollinated plants indicated a fitness cost associated with brightness. The results demonstrate that flower color traits influence pollination success and seed production in A. morio, indicating that they affect attractiveness to pollinators, efficiency of pollen transfer, or both. The documented selection is consistent with facilitated pollination and selection for color convergence toward cooccurring rewarding species.
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Affiliation(s)
- Nina Sletvold
- Department of Plant Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18 D, SE-752 36, Uppsala, Sweden.
| | - Judith Trunschke
- Department of Plant Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18 D, SE-752 36, Uppsala, Sweden
| | - Mart Smit
- Department of Plant Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18 D, SE-752 36, Uppsala, Sweden
| | - Jeffrey Verbeek
- Department of Plant Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18 D, SE-752 36, Uppsala, Sweden
| | - Jon Ågren
- Department of Plant Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18 D, SE-752 36, Uppsala, Sweden
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34
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Chapurlat E, Ågren J, Sletvold N. Spatial variation in pollinator-mediated selection on phenology, floral display and spur length in the orchid Gymnadenia conopsea. THE NEW PHYTOLOGIST 2015; 208:1264-1275. [PMID: 26183369 DOI: 10.1111/nph.13555] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2015] [Accepted: 06/09/2015] [Indexed: 06/04/2023]
Abstract
Spatial variation in plant-pollinator interactions may cause variation in pollinator-mediated selection on floral traits, but to establish this link conclusively experimental studies are needed. We quantified pollinator-mediated selection on flowering phenology and morphology in four populations of the fragrant orchid Gymnadenia conopsea, and compared selection mediated by diurnal and nocturnal pollinators in two of the populations. Variation in pollinator-mediated selection explained most of the among-population variation in the strength of directional and correlational selection. Pollinators mediated correlational selection on pairs of display traits, and on one display trait and spur length, a trait affecting pollination efficiency. Only nocturnal pollinators selected for longer spurs, and mediated stronger selection on the number of flowers compared with diurnal pollinators in one population. The two types of pollinators caused correlational selection on different pairs of traits and selected for different combinations of spur length and number of flowers. The results demonstrate that spatial variation in interactions with pollinators may result in differences in directional and correlational selection on floral traits in a plant with a semi-generalized pollination system, and suggest that differences in the relative importance of diurnal and nocturnal pollinators can cause variation in selection.
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Affiliation(s)
- Elodie Chapurlat
- Plant Ecology and Evolution, Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-752 36, Uppsala, Sweden
| | - Jon Ågren
- Plant Ecology and Evolution, Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-752 36, Uppsala, Sweden
| | - Nina Sletvold
- Plant Ecology and Evolution, Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-752 36, Uppsala, Sweden
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35
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Sletvold N, Moritz KK, Agren J. Additive effects of pollinators and herbivores result in both conflicting and reinforcing selection on floral traits. Ecology 2015; 96:214-21. [PMID: 26236906 DOI: 10.1890/14-0119.1] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Mutualists and antagonists are known to respond to similar floral cues, and may thus cause opposing selection on floral traits. However, we lack a quantitative understanding of their independent and interactive effects. In a population of the orchid Gymnadenia conopsea, we manipulated the intensity of pollination and herbivory in a factorial design to examine whether both interactions influence selection on flowering phenology, floral display, and morphology. Supplemental hand-pollination increased female fitness by 31% and one-quarter of all plants were damaged by herbivores. Both interactions contributed to selection. Pollinators mediated selection for later flowering and herbivores for earlier flowering, while both selected for longer spurs. The strength of selection was similar for both agents, and their effects were additive. As a consequence, there was no. net selection on phenology, whereas selection on spur length was strong. The experimental results demonstrate that both pollinators and herbivores can markedly influence the strength of selection on flowering phenology and floral morphology, and cause both conflicting and reinforcing selection. They also indicate that the direction of selection on phenology will vary with the relative intensity of the mutualistic and antagonistic interaction, potentially resulting in both temporal and among-population variation in optimal flowering time.
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36
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Bartkowska MP, Johnston MO. Pollen limitation and its influence on natural selection through seed set. J Evol Biol 2015; 28:2097-105. [PMID: 26310698 DOI: 10.1111/jeb.12741] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Revised: 08/09/2015] [Accepted: 08/17/2015] [Indexed: 11/30/2022]
Abstract
Stronger pollen limitation should increase competition among plants, leading to stronger selection on traits important for pollen receipt. The few explicit tests of this hypothesis, however, have provided conflicting support. Using the arithmetic relationship between these two quantities, we show that increased pollen limitation will automatically result in stronger selection (all else equal) although other factors can alter selection independently of pollen limitation. We then tested the hypothesis using two approaches. First, we analysed the published studies containing information on both pollen limitation and selection. Second, we explored how natural selection measured in one Ontario population of Lobelia cardinalis over 3 years and two Michigan populations in 1 year relates to pollen limitation. For the Ontario population, we also explored whether pollinator-mediated selection is related to pollen limitation. Consistent with the hypothesis, we found an overall positive relationship between selection strength and pollen limitation both among species and within L. cardinalis. Unexpectedly, this relationship was found even for vegetative traits among species, and was not found in L. cardinalis for pollinator-mediated selection on nearly all trait types.
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Affiliation(s)
- M P Bartkowska
- Department of Biology, Life Sciences Centre, Dalhousie University, Halifax, NS, Canada
| | - M O Johnston
- Department of Biology, Life Sciences Centre, Dalhousie University, Halifax, NS, Canada
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37
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Sletvold N, Ågren J. Climate-dependent costs of reproduction: Survival and fecundity costs decline with length of the growing season and summer temperature. Ecol Lett 2015; 18:357-64. [DOI: 10.1111/ele.12417] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 12/08/2014] [Accepted: 01/13/2015] [Indexed: 11/29/2022]
Affiliation(s)
- Nina Sletvold
- Plant Ecology and Evolution; Department of Ecology and Genetics; EBC; Uppsala University; Norbyvägen 18 D SE-752 36 Uppsala Sweden
- NTNU University Museum; Norwegian University of Science and Technology; N-7491 Trondheim Norway
| | - Jon Ågren
- Plant Ecology and Evolution; Department of Ecology and Genetics; EBC; Uppsala University; Norbyvägen 18 D SE-752 36 Uppsala Sweden
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38
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Walsh RP, Arnold PM, Michaels HJ. Effects of pollination limitation and seed predation on female reproductive success of a deceptive orchid. AOB PLANTS 2014; 6:plu031. [PMID: 24916060 PMCID: PMC4094650 DOI: 10.1093/aobpla/plu031] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/20/2013] [Accepted: 06/02/2014] [Indexed: 06/03/2023]
Abstract
For many species of conservation significance, multiple factors limit reproduction. This research examines the contributions of plant height, number of flowers, number of stems, pollen limitation and seed predation to female reproductive success in the deceit-pollinated orchid, Cypripedium candidum. The deceptive pollination strategy employed by many orchids often results in high levels of pollen limitation. While increased floral display size may attract pollinators, C. candidum's multiple, synchronously flowering stems could promote selfing and also increase attack by weevil seed predators. To understand the joint impacts of mutualists and antagonists, we examined pollen limitation, seed predation and the effects of pollen source over two flowering seasons (2009 and 2011) in Ohio. In 2009, 36 pairs of plants size-matched by flower number, receiving either supplemental hand or open pollination, were scored for fruit maturation, mass of seeds and seed predation. Pollen supplementation increased proportion of flowers maturing into fruit, with 87 % fruit set when hand pollinated compared with 46 % for naturally pollinated flowers. Inflorescence height had a strong effect, as taller inflorescences had higher initial fruit set, while shorter stems had higher predation. Seed predation was seen in 73 % of all fruits. A parallel 2011 experiment that included a self-pollination treatment and excluded seed predators found initial and final fruit set were higher in the self and outcross pollination treatments than in the open-pollinated treatment. However, seed mass was higher in both open pollinated and outcross pollination treatments compared with hand self-pollinated. We found greater female reproductive success for taller flowering stems that simultaneously benefited from increased pollination and reduced seed predation. These studies suggest that this species is under strong reinforcing selection to increase allocation to flowering stem height. Our results may help explain the factors limiting seed production in other Cypripedium and further emphasize the importance of management in orchid conservation.
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Affiliation(s)
- Ryan P Walsh
- Department of Biological Sciences, Bowling Green State University, Bowling Green, OH 43402, USA
| | - Paige M Arnold
- Department of Biological Sciences, Bowling Green State University, Bowling Green, OH 43402, USA
| | - Helen J Michaels
- Department of Biological Sciences, Bowling Green State University, Bowling Green, OH 43402, USA
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39
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Sletvold N, Agren J. There is more to pollinator-mediated selection than pollen limitation. Evolution 2014; 68:1907-18. [PMID: 24635099 DOI: 10.1111/evo.12405] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2013] [Accepted: 03/02/2014] [Indexed: 11/26/2022]
Abstract
Spatial variation in pollinator-mediated selection (Δβpoll ) is a major driver of floral diversification, but we lack a quantitative understanding of its link to pollen limitation (PL) and net selection on floral traits. For 2-5 years, we quantified Δβpoll on floral traits in two populations each of two orchid species differing in PL. In both species, spatiotemporal variation in Δβpoll explained much of the variation in net selection. Selection was consistently stronger and the proportion that was pollinator-mediated was higher in the severely pollen-limited deceptive species than in the rewarding species. Within species, variation in PL could not explain variation in Δβpoll for any trait, indicating that factors influencing the functional relationship between trait variation and pollination success govern a major part of the observed variation in Δβpoll . Separating the effects of variation in mean interaction intensity and in the functional significance of traits will be necessary to understand spatiotemporal variation in selection exerted by the biotic environment.
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Affiliation(s)
- Nina Sletvold
- Plant Ecology and Evolution, Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18 D, SE-752 36 Uppsala, Sweden; NTNU University Museum, N-7491 Trondheim, Norway.
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