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Castellanos MC, Montero-Pau J, Ziarsolo P, Blanca JM, Cañizares J, Pausas JG. Quantitative genetic analysis of floral traits shows current limits but potential evolution in the wild. Proc Biol Sci 2023; 290:20230141. [PMID: 37122252 PMCID: PMC10130720 DOI: 10.1098/rspb.2023.0141] [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: 01/31/2022] [Accepted: 03/22/2023] [Indexed: 05/02/2023] Open
Abstract
The vast variation in floral traits across angiosperms is often interpreted as the result of adaptation to pollinators. However, studies in wild populations often find no evidence of pollinator-mediated selection on flowers. Evolutionary theory predicts this could be the outcome of periods of stasis under stable conditions, followed by shorter periods of pollinator change that provide selection for innovative phenotypes. We asked if periods of stasis are caused by stabilizing selection, absence of other forms of selection or by low trait ability to respond even if selection is present. We studied a plant predominantly pollinated by one bee species across its range. We measured heritability and evolvability of traits, using genome-wide relatedness in a large wild population, and combined this with estimates of selection on the same individuals. We found evidence for both stabilizing selection and low trait heritability as potential explanations for stasis in flowers. The area of the standard petal is under stabilizing selection, but the variability is not heritable. A separate trait, floral weight, presents high heritability, but is not currently under selection. We show how a simple pollination environment coincides with the absence of current prerequisites for adaptive evolutionary change, while heritable variation remains to respond to future selection pressures.
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Affiliation(s)
- Maria Clara Castellanos
- School of Life Sciences, Universityof Sussex, Brighton BN1 9QG, UK
- CIDE-CSIC, Montcada, Valencia, Spain
| | - Javier Montero-Pau
- COMAV, Universitat Politècnica de València, Valencia, Spain
- Cavanilles Institute of Biodiversity and Evolutionary Biology, Universitat de València, Valencia, Spain
| | - Peio Ziarsolo
- COMAV, Universitat Politècnica de València, Valencia, Spain
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2
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Carlson ML, Fulkerson JR. Phenotypic selection on floral traits in the arctic plant
Parrya nudicaulis
(Brassicaceae). Ecol Evol 2022; 12:e8624. [PMID: 35261739 PMCID: PMC8888260 DOI: 10.1002/ece3.8624] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Revised: 10/20/2021] [Accepted: 10/29/2021] [Indexed: 11/06/2022] Open
Abstract
The evolution of floral traits is often attributed to pollinator‐mediated selection; however, the importance of pollinators as selective agents in arctic environments is poorly resolved. In arctic and subarctic regions that are thought to be pollen limited, selection is expected to either favor floral traits that increase pollinator attraction or promote reproductive assurance through selfing. We quantified phenotypic selection on floral traits in two arctic and two subarctic populations of the self‐compatible, but largely pollinator‐dependent, Parrya nudicaulis. Additionally, we measured selection in plants in both open pollination and pollen augmentation treatments to estimate selection imposed by pollinators in one population. Seed production was found to be limited by pollen availability and strong directional selection on flower number was observed. We did not detect consistently greater magnitudes of selection on floral traits in the arctic relative to the subarctic populations. Directional selection for more pigmented flowers in one arctic population was observed, however. In some populations, selection on flower color was found to interact with other traits. We did not detect consistently stronger selection gradients across all traits for plants exposed to pollinator selection relative to those in the pollen augmentation treatment; however, directional selection tended to be higher for some floral traits in open‐pollinated plants.
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Affiliation(s)
- Matthew L. Carlson
- Alaska Center for Conservation Science University of Alaska Anchorage Anchorage Alaska USA
- Biological Sciences Department University of Alaska Anchorage Anchorage Alaska USA
| | - Justin R. Fulkerson
- Alaska Center for Conservation Science University of Alaska Anchorage Anchorage Alaska USA
- Biological Sciences Department University of Alaska Anchorage Anchorage Alaska USA
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3
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Valadão-Mendes LB, Rocha I, Meireles DAL, Leite FB, Sazima M, Maruyama PK, Brito VLG. Flower morphology and plant-bee pollinator interactions are related to stamen dimorphism in Melastomataceae. PLANT BIOLOGY (STUTTGART, GERMANY) 2022; 24:240-248. [PMID: 34741381 DOI: 10.1111/plb.13359] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Accepted: 10/11/2021] [Indexed: 06/13/2023]
Abstract
Approximately 20,000 species of flowering plant offer mainly pollen to their pollinators, generally bees. Stamen dimorphism, a floral trait commonly present in some pollen flowers, is thought to be associated with exclusive pollen provision for highly effective bee pollinators. Notwithstanding, little is known about how stamen dimorphism is related to other floral morphological traits and, consequently, plant-pollinator interactions at the community scale. Here we investigated the relationship between stamen dimorphism and other floral morphological traits, as well as the interactions with pollinators in plants of Melastomataceae. We characterized each plant species as stamen dimorphic or stamen isomorphic according to differences in size and shape between stamen sets. Data on interactions between the plants and their bee pollinators were analysed as quantitative bipartite networks. We found that petal and style size and shape were correlated to stamen dimorphism. Stamen dimorphic species present larger flowers and less variable style shapes than stamen isomorphic species. Furthermore, stamen dimorphism is associated with higher richness of visiting bees, i.e. higher ecological generalization. During the evolutionary history of Melastomataceae, the dependence on pollinators for fruit set has possibly favoured the evolution of larger flowers with dimorphic stamens, which in turn are able to make use of a larger spectrum of pollen-collecting bees, leading to ecological generalization.
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Affiliation(s)
- L B Valadão-Mendes
- Programa de Pós-Graduação em Ecologia, Conservação e Manejo de Vida Silvestre, Universidade Federal de Minas Gerais, Belo Horizonte, Brasil
- Centro de Síntese Ecológica e Conservação, Departamento de Genética, Ecologia e Evolução, ICB, Universidade Federal de Minas Gerais, Belo Horizonte, Brasil
| | - I Rocha
- Instituto de Biologia, Universidade Federal de Uberlândia, Uberlândia, Brasil
| | - D A L Meireles
- Programa de Pós-Graduação em Ecologia e Conservação dos Recursos Naturais, Universidade Federal de Uberlândia, Uberlândia, Brasil
- Departamento de Ecologia, Instituto de Ciências Biologicas, Universidade Federal de Goiás, Goiânia, Brasil
| | - F B Leite
- Programa de Pós-Graduação em Biologia Vegetal, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, Brasil
| | - M Sazima
- Departamento de Biologia Vegetal, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, Brasil
| | - P K Maruyama
- Centro de Síntese Ecológica e Conservação, Departamento de Genética, Ecologia e Evolução, ICB, Universidade Federal de Minas Gerais, Belo Horizonte, Brasil
| | - V L G Brito
- Instituto de Biologia, Universidade Federal de Uberlândia, Uberlândia, Brasil
- Programa de Pós-Graduação em Biologia Vegetal, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, Brasil
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4
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Toji T, Hirota SK, Ishimoto N, Suyama Y, Itino T. Intraspecific independent evolution of floral spur length in response to local flower visitor size in Japanese Aquilegia in different mountain regions. Ecol Evol 2022; 12:e8668. [PMID: 35261751 PMCID: PMC8888250 DOI: 10.1002/ece3.8668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2021] [Revised: 02/03/2022] [Accepted: 02/07/2022] [Indexed: 11/10/2022] Open
Abstract
Geographic differences in floral traits may reflect geographic differences in effective pollinator assemblages. Independent local adaptation to pollinator assemblages in multiple regions would be expected to cause parallel floral trait evolution, although sufficient evidence for this is still lacking. Knowing the intraspecific evolutionary history of floral traits will reveal events that occur in the early stages of trait diversification. In this study, we investigated the relationship between flower spur length and pollinator size in 16 populations of Aquilegia buergeriana var. buergeriana distributed in four mountain regions in the Japanese Alps. We also examined the genetic relationship between yellow- and red-flowered individuals, to see if color differences caused genetic differentiation by pollinator isolation. Genetic relationships among 16 populations were analyzed based on genome-wide single-nucleotide polymorphisms. Even among populations within the same mountain region, pollinator size varied widely, and the average spur length of A. buergeriana var. buergeriana in each population was strongly related to the average visitor size of that population. Genetic relatedness between populations was not related to the similarity of spur length between populations; rather, it was related to the geographic proximity of populations in each mountain region. Our results indicate that spur length in each population evolved independently of the population genetic structure but in parallel in response to local flower visitor size in different mountain regions. Further, yellow- and red-flowered individuals of A. buergeriana var. buergeriana were not genetically differentiated. Unlike other Aquilegia species in Europe and America visited by hummingbirds and hawkmoths, the Japanese Aquilegia species is consistently visited by bumblebees. As a result, genetic isolation by flower color may not have occurred.
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Affiliation(s)
- Tsubasa Toji
- Graduate School of Medicine, Science and TechnologyShinshu UniversityMatsumotoJapan
| | - Shun K. Hirota
- Field Science Center, Graduate School of Agricultural ScienceTohoku UniversityOsakiJapan
| | | | - Yoshihisa Suyama
- Field Science Center, Graduate School of Agricultural ScienceTohoku UniversityOsakiJapan
| | - Takao Itino
- Faculty of ScienceShinshu UniversityMatsumotoJapan
- Department of Biology and Institute of Mountain ScienceShinshu UniversityMatsumotoJapan
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McMann N, Peichel A, Savage JA. Early spring flowers rely on xylem hydration but are not limited by stem xylem conductivity. THE NEW PHYTOLOGIST 2022; 233:838-850. [PMID: 34618926 DOI: 10.1111/nph.17782] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Accepted: 09/13/2021] [Indexed: 06/13/2023]
Abstract
Many woody plants produce large floral displays early in the spring when xylem transport can be variable and often reduced. To determine whether stem hydraulics impact floral water use, we quantified floral transpiration and tested whether it was correlated with stem xylem conductivity in five temperate woody species that flower before producing leaves. We measured inflorescence gas exchange, examined the relationship between diffusive conductance and inflorescence morphology, and estimated the amount of water supplied to an inflorescence by the phloem. We also tested for correlation between transpiration and native stem xylem conductivity for branches with leaves and branches with flowers. The flowers of our study species obtain most of their water from the xylem. Diffusive conductance was higher in small inflorescences, but water content and daily transpiration rates were greater for larger inflorescences. We found no correlation between floral transpiration per branch and stem xylem conductivity within species. The data suggest that inflorescence water loss during anthesis is not limited by the xylem in our study species. We highlight the impact of floral morphology on hydraulic traits and encourage exploration into temporal shifts in floral hydration.
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Affiliation(s)
- Natalie McMann
- Department of Biology, University of Minnesota Duluth, 207 Swenson Science Building, 1035 Kirby Drive, Duluth, MN, 55812, USA
| | - Alexander Peichel
- Department of Biology, University of Minnesota Duluth, 207 Swenson Science Building, 1035 Kirby Drive, Duluth, MN, 55812, USA
| | - Jessica A Savage
- Department of Biology, University of Minnesota Duluth, 207 Swenson Science Building, 1035 Kirby Drive, Duluth, MN, 55812, USA
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Minachilis K, Kantsa A, Petanidou T. Bumblebees, the proficient mountain pollinators: evidence from Stachys germanica (Lamiaceae) along the altitudinal gradient of Mount Olympus, Greece. Biol J Linn Soc Lond 2021. [DOI: 10.1093/biolinnean/blab113] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Abstract
Pollen limitation and its drivers along altitudinal clines form a controversial topic, highlighting the need for more studies and in different biomes. We tested the hypothesis that the populations of a predominantly bee-pollinated plant are pollen-limited along elevations and examined whether this is related to bee visitation rate. For two years, we studied flower visitation, pollen limitation and mating system using five populations of Stachys germanica L. occurring between 327 and 1936 m a.s.l. on Mt. Olympus, Greece. S. germanica showed moderate to high self-compatibility, low spontaneous self-pollination and low pollen limitation across all altitudes and years. Bumblebees were the dominant pollinators; their visitation increased with altitude and was positively correlated with seed set and negatively correlated with pollen limitation. The opposite trend was found for the visitation by other pollinators. Seed mass was independent of visitation. Low pollen limitation is evidently due to high bumblebee visitation along the altitude, whereas seed mass could be linked to resource availability or environmental conditions. Our findings underline the functional role of bumblebees on Mediterranean mountains, and the need to focus on bumblebee conservation on this legendary mountain.
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Affiliation(s)
- Konstantinos Minachilis
- Laboratory of Biogeography and Ecology, Department of Geography, University of the Aegean, Mytilene, Greece
| | - Aphrodite Kantsa
- Laboratory of Biogeography and Ecology, Department of Geography, University of the Aegean, Mytilene, Greece
- Department of Environmental Systems Science, ETH Zürich, Zürich, Switzerland
| | - Theodora Petanidou
- Laboratory of Biogeography and Ecology, Department of Geography, University of the Aegean, Mytilene, Greece
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7
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Toji T, Ishimoto N, Egawa S, Nakase Y, Hattori M, Itino T. Intraspecific convergence of floral size correlates with pollinator size on different mountains: a case study of a bumblebee-pollinated Lamium (Lamiaceae) flowers in Japan. BMC Ecol Evol 2021; 21:64. [PMID: 33894742 PMCID: PMC8067403 DOI: 10.1186/s12862-021-01796-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Accepted: 04/15/2021] [Indexed: 11/18/2022] Open
Abstract
Background Geographic differences in floral size sometimes reflect geographic differences in pollinator size. However, we know little about whether this floral size specialization to the regional pollinator size occurred independently at many places or occurred once and then spread across the distribution range of the plant species. Results We investigated the relationship between the local floral size of flowers and local pollinator size in 12 populations of Lamium album var. barbatum on two different mountains in the Japan Alps. Then, using 10 microsatellite markers, we analyzed genetic differentiation among the 12 populations. The results showed that local floral size was correlated with the average size of relevant morphological traits of the local pollinators: floral size was greater in populations visited frequently by the largest flower visitors, Bombus consobrinus queens, than it was in other populations. We also found that the degree of genetic similarity between populations more closely reflected interpopulation geographic proximity than interpopulation similarity in floral size. Conclusions Although genetic similarity of populations was highly associated with geographic proximity, floral size varied independently of geographic proximity and was associated with local pollinator size. These results suggest that in L. album var. barbatum, large floral size evolved independently in populations on different mountains as a convergent adaptation to locally abundant large bumblebee species. Supplementary Information The online version contains supplementary material available at 10.1186/s12862-021-01796-8.
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Affiliation(s)
- Tsubasa Toji
- Graduate School of Medicine, Science and Technology, Shinshu University, Matsumoto, 3-1-1 Asahi, Nagano, 390-8621, Japan.
| | - Natsumi Ishimoto
- Faculty of Science, Shinshu University, Matsumoto, 3-1-1 Asahi, Nagano, 390-8621, Japan
| | - Shin Egawa
- Faculty of Science, Shinshu University, Matsumoto, 3-1-1 Asahi, Nagano, 390-8621, Japan
| | - Yuta Nakase
- Faculty of Science, Shinshu University, Matsumoto, 3-1-1 Asahi, Nagano, 390-8621, Japan
| | - Mitsuru Hattori
- Graduate School of Fisheries and Environmental Sciences, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki, 852-8521, Japan
| | - Takao Itino
- Faculty of Science, Shinshu University, Matsumoto, 3-1-1 Asahi, Nagano, 390-8621, Japan.,Department of Biology and Institute of Mountain Science, Shinshu University, Matsumoto, 3-1-1 Asahi, Nagano, 390-8621, Japan
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8
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Kuppler J, Wieland J, Junker RR, Ayasse M. Drought-induced reduction in flower size and abundance correlates with reduced flower visits by bumble bees. AOB PLANTS 2021; 13:plab001. [PMID: 33628409 PMCID: PMC7891244 DOI: 10.1093/aobpla/plab001] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 01/05/2021] [Indexed: 05/04/2023]
Abstract
Reduced water availability can cause physiological stress in plants that affects floral development leading to changes in floral morphology and traits that mediate interactions with pollinators. As pollinators can detect small changes in trait expressions, drought-induced changes in floral traits could affect pollinator visitations. However, the linkage between changes in floral traits and pollinator visitations under drought conditions is not well explored. We, therefore, tested whether drought-induced changes in floral morphology and abundance of flowers are linked to changes in pollinator visitations. We conducted flight cage experiments with a radio frequency identification system for automated visitation recordings with bumble bees (Bombus terrestris) and common charlock (Sinapis arvensis) as the model system. In total, we recorded interactions for 31 foraging bumble bees and 6569 flower visitations. We found that decreasing soil moisture content correlated with decreasing size of all measured morphological traits except stamen length and nectar tube width. The reductions in floral size, petal width and length, nectar tube depth and number of flowers resulted in decreasing visitation rates by bumble bees. These decreasing visitations under lower soil moisture availability might be explained by lower numbers of flowers and thus a reduced attractiveness and/or by increased difficulties experienced by bumble bees in handling smaller flowers. Whether these effects act additively or synergistically on pollinator behaviour and whether this leads to changes in pollen transfer and to different selectionp ressures require further investigation.
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Affiliation(s)
- J Kuppler
- Institute of Evolutionary Ecology and Conservation Genomics, Ulm University, Ulm, Germany
- Corresponding author’s e-mail address:
| | - J Wieland
- Institute of Evolutionary Ecology and Conservation Genomics, Ulm University, Ulm, Germany
| | - R R Junker
- Evolutionary Ecology of Plants, Department of Biology, Philipps-University Marburg, Marburg, Germany
- Department of Biosciences, University of Salzburg, Salzburg, Austria
| | - M Ayasse
- Institute of Evolutionary Ecology and Conservation Genomics, Ulm University, Ulm, Germany
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Zu P, Schiestl FP, Gervasi D, Li X, Runcie D, Guillaume F. Floral signals evolve in a predictable way under artificial and pollinator selection in Brassica rapa. BMC Evol Biol 2020; 20:127. [PMID: 32972368 PMCID: PMC7517814 DOI: 10.1186/s12862-020-01692-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Accepted: 09/16/2020] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND Angiosperms employ an astonishing variety of visual and olfactory floral signals that are generally thought to evolve under natural selection. Those morphological and chemical traits can form highly correlated sets of traits. It is not always clear which of these are used by pollinators as primary targets of selection and which would be indirectly selected by being linked to those primary targets. Quantitative genetics tools for predicting multiple traits response to selection have been developed since long and have advanced our understanding of evolution of genetically correlated traits in various biological systems. We use these tools to predict the evolutionary trajectories of floral traits and understand the selection pressures acting on them. RESULTS We used data from an artificial selection and a pollinator (bumblebee, hoverfly) evolution experiment with fast cycling Brassica rapa plants to predict evolutionary changes of 12 floral volatiles and 4 morphological floral traits in response to selection. Using the observed selection gradients and the genetic variance-covariance matrix (G-matrix) of the traits, we showed that the observed responses of most floral traits including volatiles were predicted in the right direction in both artificial- and bumblebee-selection experiment. Genetic covariance had a mix of constraining and facilitating effects on evolutionary responses. We further revealed that G-matrices also evolved in the selection processes. CONCLUSIONS Overall, our integrative study shows that floral signals, especially volatiles, evolve under selection in a mostly predictable way, at least during short term evolution. Evolutionary constraints stemming from genetic covariance affected traits evolutionary trajectories and thus it is important to include genetic covariance for predicting the evolutionary changes of a comprehensive suite of traits. Other processes such as resource limitation and selfing also need to be considered for a better understanding of floral trait evolution.
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Affiliation(s)
- Pengjuan Zu
- Department of Systematic and Evolutionary Botany, University of Zürich, Zollikerstrasse 107, CH-8008, Zürich, Switzerland
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA
| | - Florian P Schiestl
- Department of Systematic and Evolutionary Botany, University of Zürich, Zollikerstrasse 107, CH-8008, Zürich, Switzerland
| | - Daniel Gervasi
- Department of Systematic and Evolutionary Botany, University of Zürich, Zollikerstrasse 107, CH-8008, Zürich, Switzerland
| | - Xin Li
- Department of Plant Sciences, University of California Davis, One Shields Avenue, Davis, CA, 95616, USA
| | - Daniel Runcie
- Department of Plant Sciences, University of California Davis, One Shields Avenue, Davis, CA, 95616, USA
| | - Frédéric Guillaume
- Department of Evolutionary Biology and Environmental Studies, University of Zürich, Winterthurerstrasse 190, CH-8057, Zürich, Switzerland.
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Phillips RD, Peakall R, van der Niet T, Johnson SD. Niche Perspectives on Plant-Pollinator Interactions. TRENDS IN PLANT SCIENCE 2020; 25:779-793. [PMID: 32386827 DOI: 10.1016/j.tplants.2020.03.009] [Citation(s) in RCA: 55] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2019] [Revised: 03/12/2020] [Accepted: 03/25/2020] [Indexed: 05/03/2023]
Abstract
Ecological niches are crucial for species coexistence and diversification, but the niche concept has been underutilized in studying the roles of pollinators in plant evolution and reproduction. Pollination niches can be objectively characterized using pollinator traits, abundance, and distributions, as well as network topology. We review evidence that floral traits represent adaptations to pollination niches, where tradeoffs in trait deployment reinforce niche specialization. In turn, specialized pollination niches potentially increase speciation rates, foster species coexistence, and constrain species range limits. By linking studies of adaptation with those on speciation and coexistence, the pollination niche provides an organizing principle for research on plant reproduction, and conceptually unites these studies with fields of biology where the niche perspective is already firmly established.
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Affiliation(s)
- Ryan D Phillips
- Department of Ecology, Environment, and Evolution, La Trobe University, VIC 3086, Australia; Kings Park Science, Department of Biodiversity, Conservation, and Attractions, WA 6005, Australia; Ecology and Evolution, Research School of Biology, The Australian National University, Canberra, ACT 2600, Australia.
| | - Rod Peakall
- Ecology and Evolution, Research School of Biology, The Australian National University, Canberra, ACT 2600, Australia
| | - Timotheüs van der Niet
- Centre for Functional Biodiversity, School of Life Sciences, University of KwaZulu-Natal, P Bag X01, Scottsville 3209, South Africa
| | - Steven D Johnson
- Centre for Functional Biodiversity, School of Life Sciences, University of KwaZulu-Natal, P Bag X01, Scottsville 3209, South Africa
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11
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Zhao R, Zhang H, An L. Plant size influences abundance of floral visitors and biomass allocation for the cushion plant Thylacospermum caespitosum under an extreme alpine environment. Ecol Evol 2019; 9:5501-5511. [PMID: 31110698 PMCID: PMC6509400 DOI: 10.1002/ece3.5147] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Revised: 03/18/2019] [Accepted: 03/18/2019] [Indexed: 01/18/2023] Open
Abstract
Variation in size may influence the abundance of visitors and reproductive allocation for cushion plants in the extreme alpine environments. To assess effects of plant size on the abundance of main visitors and reproductive allocation in Thylacospermum caespitosum populations at two altitudes, the abundance of the visitors, visiting frequency, total number of flowers, number of fruits, number of unseeded flowers, and reproductive allocation were investigated during the period of reproductive growth. Concurrently, the effects of plant size on the visitors' contributions to fruit setting rate were assessed by a bagging experiment. Our results showed that flies (Musca domestica and Dasyphora asiatica) were the main pollinating insects of T. caespitosum, and they could obvious facilitate (p < 0.05) the fruit setting rate of this cushion plant. Seed set and floral visitation were significantly influenced (p < 0.001) by plant size. Moreover, the reproductive allocation and fruit setting rate of T. caespitosum was influenced (p < 0.001) by plant size. More biomass was allocated to reproduction in plants of greater diameter. There is an increase in reproductive success (increases of fruit number with increase in plant size) in relation to plant size. In conclusion, the extent of M. domestica and D. asiatica to facilitate the fruit setting rate mainly depended on the size of T. caespitosum. Size-dependent reproductive allocation occurred in T. caespitosum and was the chief factor affecting the contribution of flies to fruit setting rate. These traits reflect reproductive fitness of T. caespitosum related to plant size in extreme alpine environments.
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Affiliation(s)
- Ruiming Zhao
- MOE Key Laboratory of Cell Activities and Stress AdaptationsSchool of Life SciencesLanzhou UniversityLanzhouChina
| | - Hua Zhang
- MOE Key Laboratory of Cell Activities and Stress AdaptationsSchool of Life SciencesLanzhou UniversityLanzhouChina
| | - Lizhe An
- The College of ForestryBeijing Forestry UniversityBeijingChina
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12
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Opedal ØH. The evolvability of animal-pollinated flowers: towards predicting adaptation to novel pollinator communities. THE NEW PHYTOLOGIST 2019; 221:1128-1135. [PMID: 30145801 DOI: 10.1111/nph.15403] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Accepted: 07/23/2018] [Indexed: 06/08/2023]
Abstract
In the event of a community turnover, population decline, or complete disappearance of pollinators, animal-pollinated plants may respond by adapting to novel pollinators or by changing their mating system. The ability of populations to adapt is determined by their ability to respond to novel selection pressures, i.e. their evolvability. In the short term, evolvability is determined by standing genetic variation in the trait under selection. To evaluate the evolutionary potential of plant reproductive systems, I compiled genetic-variance estimates for a large selection of floral traits mediating shifts in pollination and mating systems. Then, I computed evolvabilities and compared these among trait groups and against the evolvabilities of vegetative traits. Evolvabilities of most floral traits were substantial yet tended to be lower than the median for vegetative traits. Among floral traits, herkogamy (anther-stigma distance), floral-display traits and perhaps floral-volatile concentrations had greater-than-average evolvabilities, while the evolvabilities of pollinator-fit traits were below average. These results suggest that most floral traits have the potential to evolve rapidly in response to novel selection pressures, providing resilience of plant reproductive systems in the event of changing pollinator communities.
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Affiliation(s)
- Øystein H Opedal
- Centre for Biodiversity Dynamics, Department of Biology, Norwegian University of Science and Technology, NTNU, Trondheim, 7491, Norway
- Research Centre for Ecological Change, Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland
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13
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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: 91] [Impact Index Per Article: 15.2] [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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14
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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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15
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Campbell DR, Faidiga A, Trujillo G. Clines in traits compared over two decades in a plant hybrid zone. ANNALS OF BOTANY 2018; 122:315-324. [PMID: 29800076 PMCID: PMC6070099 DOI: 10.1093/aob/mcy072] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Accepted: 04/17/2018] [Indexed: 05/30/2023]
Abstract
Background and Aims Clines in traits across hybrid zones reflect a balance between natural selection and gene flow. Changes over time in average values for traits, and especially the shapes of their clines, are rarely investigated in plants, but could result from evolution in an unstable hybrid zone. Differences in clines between floral and vegetative traits could indicate different strengths of divergent selection. Methods Five floral and two vegetative traits were measured in 12 populations along an elevational gradient spanning a natural hybrid zone between Ipomopsis aggregata and Ipomopsis tenuituba. We compared clines in the floral traits with those measured 25 years ago. Observed changes in mean trait values were compared with predictions based on prior estimates of natural selection. We also compared the steepness and position of clines between the floral and vegetative traits. Key Results Corolla length has increased over five generations to an extent that matches predictions from measurements of phenotypic selection and heritability. The shape of its cline, and that of other traits, has not changed detectably. Clines varied across traits, but not all floral traits showed steeper clines than did vegetative traits. Both suites of morphological traits had steeper clines than did neutral molecular markers. Conclusions The increase in corolla length provides a rare example of a match between predicted and observed evolution of a plant trait in natural populations. The clinal properties are consistent with the hypothesis that habitat-mediated divergent selection on vegetative traits and pollinator-mediated selection on floral traits both maintain species differences across the hybrid zone.
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Affiliation(s)
- Diane R Campbell
- Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697, USA
- Rocky Mountain Biological Laboratory, Crested Butte, CO 81224, USA
| | | | - Gabriel Trujillo
- Rocky Mountain Biological Laboratory, Crested Butte, CO 81224, USA
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16
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Knight TM, Ashman T, Bennett J, Burns JH, Passonneau S, Steets JA. Reflections on, and visions for, the changing field of pollination ecology. Ecol Lett 2018; 21:1282-1295. [DOI: 10.1111/ele.13094] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Revised: 03/10/2018] [Accepted: 04/17/2018] [Indexed: 01/03/2023]
Affiliation(s)
- T. M. Knight
- Institute of Biology Martin Luther University Halle‐Wittenberg Am Kirchtor 1 06108 Halle Germany
- Department Community Ecology Helmholtz Centre for Environmental Research – UFZ Theodor‐Lieser‐Straße 4 06120 Halle Germany
- German Centre for Integrative Biodiversity Research (iDiv) Halle‐Jena‐Leipzig Deutscher Platz 5e 04103 Leipzig Germany
| | - T.‐L. Ashman
- Department of Biological Sciences University of Pittsburgh Pittsburgh PA15260 USA
| | - J. M. Bennett
- Institute of Biology Martin Luther University Halle‐Wittenberg Am Kirchtor 1 06108 Halle Germany
- German Centre for Integrative Biodiversity Research (iDiv) Halle‐Jena‐Leipzig Deutscher Platz 5e 04103 Leipzig Germany
| | - J. H. Burns
- Department of Biology Case Western Reserve University Cleveland OH44106‐7080 USA
| | - S. Passonneau
- Institute of Biology Martin Luther University Halle‐Wittenberg Am Kirchtor 1 06108 Halle Germany
- Department Community Ecology Helmholtz Centre for Environmental Research – UFZ Theodor‐Lieser‐Straße 4 06120 Halle Germany
- German Centre for Integrative Biodiversity Research (iDiv) Halle‐Jena‐Leipzig Deutscher Platz 5e 04103 Leipzig Germany
| | - J. A. Steets
- Department of Plant Biology, Ecology, and Evolution Oklahoma State University Stillwater OK74078 USA
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17
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Smith SD, Kriebel R. Convergent evolution of floral shape tied to pollinator shifts in Iochrominae (Solanaceae)*. Evolution 2018; 72:688-697. [DOI: 10.1111/evo.13416] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 12/01/2017] [Accepted: 12/08/2017] [Indexed: 12/31/2022]
Affiliation(s)
- Stacey D. Smith
- Department of Ecology and Evolutionary Biology University of Colorado Boulder Colorado 80305
| | - Ricardo Kriebel
- Department of Botany University of Wisconsin – Madison Madison Wisconsin 53706
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18
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Kettenbach JA, Miller-Struttmann N, Moffett Z, Galen C. How shrub encroachment under climate change could threaten pollination services for alpine wildflowers: A case study using the alpine skypilot, Polemonium viscosum. Ecol Evol 2017; 7:6963-6971. [PMID: 28904775 PMCID: PMC5587488 DOI: 10.1002/ece3.3272] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Revised: 06/06/2017] [Accepted: 06/25/2017] [Indexed: 11/06/2022] Open
Abstract
Under climate change, shrubs encroaching into high altitude plant communities disrupt ecosystem processes. Yet effects of encroachment on pollination mutualisms are poorly understood. Here, we probe potential fitness impacts of interference from encroaching Salix (willows) on pollination quality of the alpine skypilot, Polemonium viscosum. Overlap in flowering time of Salix and Polemonium is a precondition for interference and was surveyed in four extant and 25 historic contact zones. Pollinator sharing was ascertained from observations of willow pollen on bumble bees visiting Polemonium flowers and on Polemonium pistils. We probed fitness effects of pollinator sharing by measuring the correlation between Salix pollen contamination and seed set in naturally pollinated Polemonium. To ascertain whether Salix interference occurred during or after pollination, we compared seed set under natural pollination, conspecific pollen addition, and Salix pollen addition. In current and past contact zones Polemonium and Salix overlapped in flowering time. After accounting for variance in flowering date due to latitude, Salix and Polemonium showed similar advances in flowering under warmer summers. This trend supports the idea that sensitivity to temperature promotes reproductive synchrony in both species. Salix pollen is carried by bumble bees when visiting Polemonium flowers and accounts for up to 25% of the grains on Polemonium pistils. Salix contamination correlates with reduced seed set in nature and when applied experimentally. Postpollination processes likely mediate these deleterious effects as seed set in nature was not limited by pollen delivery. SYNTHESIS As willows move higher with climate change, we predict that they will drive postpollination interference, reducing the fitness benefits of pollinator visitation for Polemonium and selecting for traits that reduce pollinator sharing.
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Affiliation(s)
| | | | - Zoë Moffett
- Department of Biology Colorado College Colorado Springs CO USA
| | - Candace Galen
- Division of Biological Sciences University of Missouri Columbia MO USA
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19
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Campbell DR. EVOLUTION OF FLORAL TRAITS IN A HERMAPHRODITIC PLANT: FIELD MEASUREMENTS OF HERITABILITIES AND GENETIC CORRELATIONS. Evolution 2017; 50:1442-1453. [DOI: 10.1111/j.1558-5646.1996.tb03918.x] [Citation(s) in RCA: 102] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/1995] [Accepted: 11/28/1995] [Indexed: 11/27/2022]
Affiliation(s)
- Diane R. Campbell
- Department of Ecology and Evolutionary Biology University of California Irvine California 92717
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20
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Hamilton MB. GENETIC FINGERPRINT‐INFERRED POPULATION SUBDIVISION AND SPATIAL GENETIC TESTS FOR ISOLATION BY DISTANCE AND ADAPTATION IN THE COASTAL PLANT
LIMONIUM CAROLINIANUM. Evolution 2017; 51:1457-1468. [DOI: 10.1111/j.1558-5646.1997.tb01469.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/1996] [Accepted: 06/11/1997] [Indexed: 11/29/2022]
Affiliation(s)
- Matthew B. Hamilton
- Department of Ecology and Evolutionary Biology Brown University Box G‐W Providence Rhode Island 02912
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21
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Real-time divergent evolution in plants driven by pollinators. Nat Commun 2017; 8:14691. [PMID: 28291771 PMCID: PMC5424062 DOI: 10.1038/ncomms14691] [Citation(s) in RCA: 155] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Accepted: 01/23/2017] [Indexed: 12/28/2022] Open
Abstract
Pollinator-driven diversification is thought to be a major source of floral variation in plants. Our knowledge of this process is, however, limited to indirect assessments of evolutionary changes. Here, we employ experimental evolution with fast cycling Brassica rapa plants to demonstrate adaptive evolution driven by different pollinators. Our study shows pollinator-driven divergent selection as well as divergent evolution in plant traits. Plants pollinated by bumblebees evolved taller size and more fragrant flowers with increased ultraviolet reflection. Bumblebees preferred bumblebee-pollinated plants over hoverfly-pollinated plants at the end of the experiment, showing that plants had adapted to the bumblebees' preferences. Plants with hoverfly pollination became shorter, had reduced emission of some floral volatiles, but increased fitness through augmented autonomous self-pollination. Our study demonstrates that changes in pollinator communities can have rapid consequences on the evolution of plant traits and mating system.
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22
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Kamath A, Levin RA, Miller JS. Floral size and shape evolution following the transition to gender dimorphism. AMERICAN JOURNAL OF BOTANY 2017; 104:451-460. [PMID: 28298376 DOI: 10.3732/ajb.1600442] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2016] [Accepted: 02/03/2017] [Indexed: 06/06/2023]
Abstract
PREMISE OF THE STUDY Floral morphology is expected to evolve following the transition from cosexuality to gender dimorphism in plants, as selection through male and female function becomes dissociated. Specifically, male-biased dimorphism in flower size can arise through selection for larger flowers through male function, selection for smaller flowers through female function, or both. The evolutionary pathway to floral dimorphism can be most effectively reconstructed in species with intraspecific variation in sexual system. We examined the evolution of flower size and shape in Lycium californicum, whose populations are either gender dimorphic with male and female plants, or cosexual with hermaphroditic plants. METHODS Floral morphology was characterized in populations spanning the species' complete range. For a subset of the range where cosexual and dimorphic populations are in close proximity, we compared the size and shape of flowers from female and male plants in dimorphic populations to hermaphrodites in cosexual populations, accounting for variation associated with abiotic environmental conditions. KEY RESULTS The magnitude of flower size dimorphism varied across dimorphic populations. After controlling for environmental variation across cosexual and dimorphic populations, flowers on males were larger than flowers on females and hermaphrodites, whereas flower size did not differ between females and hermaphrodites. Flower shape differences were associated with mating type, sexual system, and environmental variation. CONCLUSIONS While abiotic environmental gradients shape both overall flower size and shape, male-biased flower size dimorphism in L. californicum appears to arise through selection for larger flowers in males but not smaller flowers in females.
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Affiliation(s)
- Ambika Kamath
- Department of Biology, Amherst College, Amherst, Massachusetts 01002 USA
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138 USA
| | - Rachel A Levin
- Department of Biology, Amherst College, Amherst, Massachusetts 01002 USA
| | - Jill S Miller
- Department of Biology, Amherst College, Amherst, Massachusetts 01002 USA
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23
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Pacheco DA, Dudley LS, Cabezas J, Cavieres LA, Arroyo MTK. Plastic Responses Contribute to Explaining Altitudinal and Temporal Variation in Potential Flower Longevity in High Andean Rhodolirion montanum. PLoS One 2016; 11:e0166350. [PMID: 27861586 PMCID: PMC5115873 DOI: 10.1371/journal.pone.0166350] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Accepted: 10/27/2016] [Indexed: 11/28/2022] Open
Abstract
The tendency for flower longevity to increase with altitude is believed by many alpine ecologists to play an important role in compensating for low pollination rates at high altitudes due to cold and variable weather conditions. However, current studies documenting an altitudinal increase in flower longevity in the alpine habitat derive principally from studies on open-pollinated flowers where lower pollinator visitation rates at higher altitudes will tend to lead to flower senescence later in the life-span of a flower in comparison with lower altitudes, and thus could confound the real altitudinal pattern in a species´ potential flower longevity. In a two-year study we tested the hypothesis that a plastic effect of temperature on flower longevity could contribute to an altitudinal increase in potential flower longevity measured in pollinator-excluded flowers in high Andean Rhodolirium montanum Phil. (Amaryllidaceae). Using supplemental warming we investigated whether temperature around flowers plastically affects potential flower longevity. We determined tightly temperature-controlled potential flower longevity and flower height for natural populations on three alpine sites spread over an altitudinal transect from 2350 and 3075 m a.s.l. An experimental increase of 3.1°C around flowers significantly decreased flower longevity indicating a plastic response of flowers to temperature. Flower height in natural populations decreased significantly with altitude. Although temperature negatively affects flower longevity under experimental conditions, we found no evidence that temperature around flowers explains site variation in flower longevity over the altitudinal gradient. In a wetter year, despite a 3.5°C temperature difference around flowers at the extremes of the altitudinal range, flower longevity showed no increase with altitude. However, in a drier year, flower longevity increased significantly with altitude. The emerging picture suggests an increase in flower longevity along the altitudinal gradient is less common for potential flower longevity than for open-pollination flower longevity. Independently of any selection that may occur on potential longevity, plastic responses of flowers to environmental conditions are likely to contribute to altitudinal variation in flower longevity, especially in dry alpine areas. Such plastic responses could push flowers of alpine species towards shorter life-lengths under climate change, with uncertain consequences for successful pollination and plant fitness in a warming world.
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Affiliation(s)
- Diego Andrés Pacheco
- Instituto de Ecología y Biodiversidad, Santiago, Chile
- Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
- * E-mail:
| | - Leah S. Dudley
- Biology Department, University of Wisconsin-Stout, Menomonie, Wisconsin, United States of America
| | - Josefina Cabezas
- Instituto de Ecología y Biodiversidad, Santiago, Chile
- Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Lohengrin A. Cavieres
- Instituto de Ecología y Biodiversidad, Santiago, Chile
- Departamento de Botánica, Facultad de Ciencias Naturales y Oceanográficas, Universidad de Concepción, Concepción, Chile
| | - Mary T. K. Arroyo
- Instituto de Ecología y Biodiversidad, Santiago, Chile
- Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
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24
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Zhao Z, Lu N, Conner JK. Adaptive pattern of nectar volume within inflorescences: bumblebee foraging behavior and pollinator-mediated natural selection. Sci Rep 2016; 6:34499. [PMID: 27687244 PMCID: PMC5043277 DOI: 10.1038/srep34499] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 09/14/2016] [Indexed: 11/09/2022] Open
Abstract
Larger floral displays increase pollinator visitation as well as among-flower self-pollination (geitonogamy) in self-compatible species. Dichogamy (temporal separation of gender expression) can limit geitonogamy and increase outcrossing but this depends on pollinator behavior within inflorescences. Declining nectar volume from lower to upper flowers is a hypothesized adaptation to increase outcrossing and pollen export by encouraging the upward movment of pollinators from female to male flowers and by reducing the number of flowers probed per inflorescence, but supporting evidence has been equivocal. We tested this hypothesis in Aconitum gymnandrum by studying floral display and rewards, pollinator visitation, and pollinator-mediated selection on floral traits. We found that larger inflorescences of A. gymnandrum attracted more pollinators, but did not increase the number of flowers probed per visit. Nectar production declined with increasing flower height on average, but the opposite pattern was also common. Bumblebees responded strongly to the nectar pattern, moving from higher to lower nectar concentration. Finally, there was significant pollinator-mediated direct selection for this pattern of declining nectar volume after correcting for correlations with flower size, number, and mean nectar volume. Together, the results strongly suggest that declining nectar production in higher flowers is an adaptation to enhance outcrossing in A. gymnandrum.
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Affiliation(s)
- Zhigang Zhao
- State Key Laboratory of Grassland and Agro-Ecosystems, School of Life Sciences, Lanzhou University, Lanzhou, 730000, China
| | - Ningna Lu
- College of Life Sciences, Northwest Normal University, 730000 Lanzhou, China
| | - Jeffrey K Conner
- Kellogg Biological Station and Department of Plant Biology, Michigan State University, Hickory Corners, Michigan, 49060, USA
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25
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Diller C, Fenster CB. Corolla chirality does not contribute to directed pollen movement in Hypericum perforatum (Hypericaceae): mirror image pinwheel flowers function as radially symmetric flowers in pollination. Ecol Evol 2016; 6:5076-86. [PMID: 27547334 PMCID: PMC4979728 DOI: 10.1002/ece3.2268] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2016] [Revised: 05/24/2016] [Accepted: 05/25/2016] [Indexed: 12/19/2022] Open
Abstract
Corolla chirality, the pinwheel arrangement of petals within a flower, is found throughout the core eudicots. In 15 families, different chiral type flowers (i.e., right or left rotated corolla) exist on the same plant, and this condition is referred to as unfixed/enantiomorphic corolla chirality. There are no investigations on the significance of unfixed floral chirality on directed pollen movement even though analogous mirror image floral designs, for example, enantiostyly, has evolved in response to selection to direct pollinator and pollen movement. Here, we examine the role of corolla chirality on directing pollen transfer, pollinator behavior, and its potential influence on disassortative mating. We quantified pollen transfer and pollinator behavior and movement for both right and left rotated flowers in two populations of Hypericum perforatum. In addition, we quantified the number of right and left rotated flowers at the individual level. Pollinators were indifferent to corolla chirality resulting in no difference in pollen deposition between right and left flowers. Corolla chirality had no effect on pollinator and pollen movement between and within chiral morphs. Unlike other mirror image floral designs, corolla chirality appears to play no role in promoting disassortative mating in this species.
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Affiliation(s)
- Carolina Diller
- Department of Biology University of Maryland College Park Maryland 20742
| | - Charles B Fenster
- Department of Biology and Microbiology South Dakota State University Brookings South Dakota 57007
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26
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Zu P, Blanckenhorn WU, Schiestl FP. Heritability of floral volatiles and pleiotropic responses to artificial selection in Brassica rapa. THE NEW PHYTOLOGIST 2016; 209:1208-1219. [PMID: 26391626 DOI: 10.1111/nph.13652] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Accepted: 08/12/2015] [Indexed: 06/05/2023]
Abstract
The evolution of the vast diversity of floral volatiles is little understood, although they serve fundamental functions, such as pollinator attraction and herbivore deterrence. Floral volatiles are often species specific, yet highly variable and sensitive to environmental factors. To date, nothing is known about the heritability of floral volatiles, and whether individual compounds can evolve independently or solely in concert with the whole volatile bouquet. We conducted bi-directional artificial selection on four target floral volatiles to estimate heritability and correlated pleiotropic responses in the wild turnip (Brassica rapa). The realized heritability of the four target volatiles ranged from 20% to 45%. The average narrow-sense heritability of all 13 analyzed floral volatiles was 18% based on parent-offspring regressions. There were pleiotropic effects of the selected floral volatile compounds on other constituents of the floral scent bouquet, on flowering time and on some morphological traits. We found that the whole floral scent bouquet changed, even when there was selection only on single compounds, with the overall phenotypic covariance being unaffected. Our study demonstrates that floral scent can evolve rapidly under phenotypic selection, but with additional correlated responses in traits that are not direct targets of selection.
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Affiliation(s)
- Pengjuan Zu
- Institute of Systematic Botany, University of Zürich, Zollikerstrasse 107, CH-8008, Zürich, Switzerland
| | - Wolf U Blanckenhorn
- Institute of Evolutionary Biology and Environmental Studies, University of Zürich, Winterthurerstrasse 190, CH-8057, Zürich, Switzerland
| | - Florian P Schiestl
- Institute of Systematic Botany, University of Zürich, Zollikerstrasse 107, CH-8008, Zürich, Switzerland
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27
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Kuriya S, Hattori M, Nagano Y, Itino T. Altitudinal flower size variation correlates with local pollinator size in a bumblebee-pollinated herb, Prunella vulgaris L. (Lamiaceae). J Evol Biol 2015; 28:1761-9. [PMID: 26174480 DOI: 10.1111/jeb.12693] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Revised: 07/02/2015] [Accepted: 07/07/2015] [Indexed: 11/30/2022]
Abstract
The influence of locally different species interactions on trait evolution is a focus of recent evolutionary studies. However, few studies have demonstrated that geographically different pollinator-mediated selection influences geographic variation in floral traits, especially across a narrow geographic range. Here, we hypothesized that floral size variation in the Japanese herb Prunella vulgaris L. (Lamiaceae) is affected by geographically different pollinator sizes reflecting different pollinator assemblages. To evaluate this hypothesis, we posed two questions. (1) Is there a positive correlation between floral length and the proboscis length of pollinators (bumblebees) across altitude in a mountain range? (2) Does the flower-pollinator size match influence female and male plant fitness? We found geographic variation in the assemblage of pollinators of P. vulgaris along an altitudinal gradient, and, as a consequence, the mean pollinator proboscis length also changed altitudinally. The floral corolla length of P. vulgaris also varied along an altitudinal gradient, and this variation strongly correlated with the local pollinator size but did not correlate with altitude itself. Furthermore, we found that the size match between the floral corolla length and bee proboscis length affected female and male plant fitness and the optimal size match (associated with peak fitness) was similar for the female and male fitness. Collectively, these results suggest that pollinator-mediated selection influences spatial variation in the size of P. vulgaris flowers at a fine spatial scale.
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Affiliation(s)
- S Kuriya
- Department of Biology, Faculty of Science, Shinshu University, Matsumoto, Nagano, Japan
| | - M Hattori
- Department of Biology, Faculty of Science, Shinshu University, Matsumoto, Nagano, Japan
| | - Y Nagano
- Department of Biology, Faculty of Science, Shinshu University, Matsumoto, Nagano, Japan
| | - T Itino
- Department of Biology, Faculty of Science, Shinshu University, Matsumoto, Nagano, Japan.,Institute of Mountain Science, Shinshu University, Matsumoto, Nagano, Japan
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Peterson ML, Miller TJ, Kay KM. An ultraviolet floral polymorphism associated with life history drives pollinator discrimination in Mimulus guttatus. AMERICAN JOURNAL OF BOTANY 2015; 102:396-406. [PMID: 25784473 DOI: 10.3732/ajb.1400415] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
UNLABELLED • PREMISE OF THE STUDY Ultraviolet (UV) floral patterns are common in angiosperms and mediate pollinator attraction, efficiency, and constancy. UV patterns may vary within species, yet are cryptic to human observers. Thus, few studies have explicitly described the distribution or ecological significance of intraspecific variation in UV floral patterning. Here, we describe the geographic distribution and pattern of inheritance of a UV polymorphism in the model plant species Mimulus guttatus (Phrymaceae). We then test whether naturally occurring UV phenotypes influence pollinator interactions within M. guttatus.• METHODS We document UV patterns in 18 annual and 19 perennial populations and test whether UV pattern is associated with life history. To examine the pattern of inheritance, we conducted crosses within and between UV phenotypes. Finally, we tested whether bee pollinators discriminate among naturally occurring UV phenotypes in two settings: wild bee communities and captive Bombus impatiens.• KEY RESULTS Within M. guttatus, perennial populations exhibit a small bulls-eye pattern, whereas a bilaterally symmetric runway pattern occurs mainly in annual populations. Inheritance of UV patterning is consistent with a single-locus Mendelian model in which the runway phenotype is dominant. Bee pollinators discriminate against unfamiliar UV patterns in both natural and controlled settings.• CONCLUSIONS We describe a widespread UV polymorphism associated with life history divergence within Mimulus guttatus. UV pattern influences pollinator visitation and should be considered when estimating reproductive barriers between life history ecotypes. This work develops a new system to investigate the ecology and evolution of UV floral patterning in a species with extensive genomic resources.
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Affiliation(s)
- Megan L Peterson
- Ecology and Evolutionary Biology, University of California Santa Cruz, 1156 High Street, Santa Cruz, California 95064 USA
| | - Timothy J Miller
- Ecology and Evolutionary Biology, University of California Santa Cruz, 1156 High Street, Santa Cruz, California 95064 USA
| | - Kathleen M Kay
- Ecology and Evolutionary Biology, University of California Santa Cruz, 1156 High Street, Santa Cruz, California 95064 USA
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Zhao ZG, Wang YK. Selection by pollinators on floral traits in generalized Trollius ranunculoides (Ranunculaceae) along altitudinal gradients. PLoS One 2015; 10:e0118299. [PMID: 25692295 PMCID: PMC4334720 DOI: 10.1371/journal.pone.0118299] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Accepted: 01/13/2015] [Indexed: 11/25/2022] Open
Abstract
Abundance and visitation of pollinator assemblages tend to decrease with altitude, leading to an increase in pollen limitation. Thus increased competition for pollinators may generate stronger selection on attractive traits of flowers at high elevations and cause floral adaptive evolution. Few studies have related geographically variable selection from pollinators and intraspecific floral differentiation. We investigated the variation of Trollius ranunculoides flowers and its pollinators along an altitudinal gradient on the eastern Qinghai-Tibet Plateau, and measured phenotypic selection by pollinators on floral traits across populations. The results showed significant decline of visitation rate of bees along altitudinal gradients, while flies was unchanged. When fitness is estimated by the visitation rate rather than the seed number per plant, phenotypic selection on the sepal length and width shows a significant correlation between the selection strength and the altitude, with stronger selection at higher altitudes. However, significant decreases in the sepal length and width of T. ranunculoides along the altitudinal gradient did not correspond to stronger selection of pollinators. In contrast to the pollinator visitation, mean annual precipitation negatively affected the sepal length and width, and contributed more to geographical variation in measured floral traits than the visitation rate of pollinators. Therefore, the sepal size may have been influenced by conflicting selection pressures from biotic and abiotic selective agents. This study supports the hypothesis that lower pollinator availability at high altitude can intensify selection on flower attractive traits, but abiotic selection is preventing a response to selection from pollinators.
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Affiliation(s)
- Zhi-Gang Zhao
- State Key Laboratory of Grassland and Agro-ecosystems, School of Life Sciences, Lanzhou University, Lanzhou, 730000, P.R. China
- * E-mail:
| | - Yi-Ke Wang
- State Key Laboratory of Grassland and Agro-ecosystems, School of Life Sciences, Lanzhou University, Lanzhou, 730000, P.R. China
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Wellborn GA, Langerhans RB. Ecological opportunity and the adaptive diversification of lineages. Ecol Evol 2015; 5:176-95. [PMID: 25628875 PMCID: PMC4298445 DOI: 10.1002/ece3.1347] [Citation(s) in RCA: 95] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Revised: 10/30/2014] [Accepted: 11/07/2014] [Indexed: 11/16/2022] Open
Abstract
The tenet that ecological opportunity drives adaptive diversification has been central to theories of speciation since Darwin, yet no widely accepted definition or mechanistic framework for the concept currently exists. We propose a definition for ecological opportunity that provides an explicit mechanism for its action. In our formulation, ecological opportunity refers to environmental conditions that both permit the persistence of a lineage within a community, as well as generate divergent natural selection within that lineage. Thus, ecological opportunity arises from two fundamental elements: (1) niche availability, the ability of a population with a phenotype previously absent from a community to persist within that community and (2) niche discordance, the diversifying selection generated by the adaptive mismatch between a population's niche-related traits and the newly encountered ecological conditions. Evolutionary response to ecological opportunity is primarily governed by (1) spatiotemporal structure of ecological opportunity, which influences dynamics of selection and development of reproductive isolation and (2) diversification potential, the biological properties of a lineage that determine its capacity to diversify. Diversification under ecological opportunity proceeds as an increase in niche breadth, development of intraspecific ecotypes, speciation, and additional cycles of diversification that may themselves be triggered by speciation. Extensive ecological opportunity may exist in depauperate communities, but it is unclear whether ecological opportunity abates in species-rich communities. Because ecological opportunity should generally increase during times of rapid and multifarious environmental change, human activities may currently be generating elevated ecological opportunity - but so far little work has directly addressed this topic. Our framework highlights the need for greater synthesis of community ecology and evolutionary biology, unifying the four major components of the concept of ecological opportunity.
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Affiliation(s)
- Gary A Wellborn
- Department of Biology, University of OklahomaNorman, Oklahoma, 73019
| | - R Brian Langerhans
- Department of Biological Sciences and W.M. Keck Center for Behavioral Biology, North Carolina State UniversityCampus Box 7617, Raleigh, North Carolina, 27695
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Nagano Y, Abe K, Kitazawa T, Hattori M, Hirao AS, Itino T. Changes in pollinator fauna affect altitudinal variation of floral size in a bumblebee-pollinated herb. Ecol Evol 2014; 4:3395-407. [PMID: 25535556 PMCID: PMC4228614 DOI: 10.1002/ece3.1191] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Revised: 07/17/2014] [Accepted: 07/21/2014] [Indexed: 11/07/2022] Open
Abstract
Geographic trait variations are often caused by locally different selection regimes. As a steep environmental cline along altitude strongly influences adaptive traits, mountain ecosystems are ideal for exploring adaptive differentiation over short distances. We investigated altitudinal floral size variation of Campanula punctata var. hondoensis in 12 populations in three mountain regions of central Japan to test whether the altitudinal floral size variation was correlated with the size of the local bumblebee pollinator and to assess whether floral size was selected for by pollinator size. We found apparent geographic variations in pollinator assemblages along altitude, which consequently produced a geographic change in pollinator size. Similarly, we found altitudinal changes in floral size, which proved to be correlated with the local pollinator size, but not with altitude itself. Furthermore, pollen removal from flower styles onto bees (plant's male fitness) was strongly influenced by the size match between flower style length and pollinator mouthpart length. These results strongly suggest that C. punctata floral size is under pollinator-mediated selection and that a geographic mosaic of locally adapted C. punctata exists at fine spatial scale.
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Affiliation(s)
- Yusuke Nagano
- Department of Biology, Faculty of Science, Shinshu University3-1-1 Asahi, Matsumoto, Nagano, 390-8621, Japan
| | - Kota Abe
- Department of Biology, Faculty of Science, Shinshu University3-1-1 Asahi, Matsumoto, Nagano, 390-8621, Japan
| | - Tomoaki Kitazawa
- Department of Biology, Faculty of Science, Shinshu University3-1-1 Asahi, Matsumoto, Nagano, 390-8621, Japan
| | - Mitsuru Hattori
- Department of Biology, Faculty of Science, Shinshu University3-1-1 Asahi, Matsumoto, Nagano, 390-8621, Japan
| | - Akira S Hirao
- Sugadaira Montane Research Center, University of TsukubaUeda, Nagano, 386–2201, Japan
| | - Takao Itino
- Department of Biology, Faculty of Science, Shinshu University3-1-1 Asahi, Matsumoto, Nagano, 390-8621, Japan
- Institute of Mountain Science, Shinshu University3-1-1 Asahi, Matsumoto, Nagano, 390-8621, Japan
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Mutualists and antagonists drive among-population variation in selection and evolution of floral display in a perennial herb. Proc Natl Acad Sci U S A 2013; 110:18202-7. [PMID: 24145439 DOI: 10.1073/pnas.1301421110] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Spatial variation in the direction of selection drives the evolution of adaptive differentiation. However, few experimental studies have examined the relative importance of different environmental factors for variation in selection and evolutionary trajectories in natural populations. Here, we combine 8 y of observational data and field experiments to assess the relative importance of mutualistic and antagonistic interactions for spatial variation in selection and short-term evolution of a genetically based floral display dimorphism in the short-lived perennial herb Primula farinosa. Natural populations of this species include two floral morphs: long-scaped plants that present their flowers well above the ground and short-scaped plants with flowers positioned close to the ground. The direction and magnitude of selection on scape morph varied among populations, and so did the frequency of the short morph (median 19%, range 0-100%; n = 69 populations). A field experiment replicated at four sites demonstrated that variation in the strength of interactions with grazers and pollinators were responsible for among-population differences in relative fitness of the two morphs. Selection exerted by grazers favored the short-scaped morph, whereas pollinator-mediated selection favored the long-scaped morph. Moreover, variation in selection among natural populations was associated with differences in morph frequency change, and the experimental removal of grazers at nine sites significantly reduced the frequency of the short-scaped morph over 8 y. The results demonstrate that spatial variation in intensity of grazing and pollination produces a selection mosaic, and that changes in biotic interactions can trigger rapid genetic changes in natural plant populations.
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Abstract
Flowers exhibit amazing morphological diversity in many traits, including their size. In addition to interspecific flower size differences, many species maintain significant variation in flower size within and among populations. Flower size variation can contribute to reproductive isolation of species and thus has clear evolutionary consequences. In this review we integrate information on flower size variation from both evolutionary and developmental biology perspectives. We examine the role of flower size in the context of mating system evolution. In addition, we describe what is currently known about the genetic basis of flower size based on quantitative trait locus (QTL) mapping in several different plant species and molecular genetic studies in model plants, primarily Arabidopsis thaliana. Work in Arabidopsis suggests that many independent pathways regulate floral organ growth via effects on cell proliferation and/or cell expansion.
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Affiliation(s)
- Beth A Krizek
- Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA.
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Becklin KM, Gamez G, Uelk B, Raguso RA, Galen C. Soil fungal effects on floral signals, rewards, and aboveground interactions in an alpine pollination web. AMERICAN JOURNAL OF BOTANY 2011; 98:1299-308. [PMID: 21795735 DOI: 10.3732/ajb.1000450] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
PREMISE OF THE STUDY Plants interact with above- and belowground organisms; the combined effects of these interactions determine plant fitness and trait evolution. To better understand the ecological and evolutionary implications of multispecies interactions, we explored linkages between soil fungi, pollinators, and floral larcenists in Polemonium viscosum (Polemoniaceae). METHODS Using a fungicide, we experimentally reduced fungal colonization of krummholz and tundra P. viscosum in 2008-2009. We monitored floral signals and rewards, interactions with pollinators and larcenists, and seed set for fungicide-treated and control plants. KEY RESULTS Fungicide effects varied among traits, between interactions, and with environmental context. Treatment effects were negligible in 2008, but stronger in 2009, especially in the less-fertile krummholz habitat. There, fungicide increased nectar sugar content and damage by larcenist ants, but did not affect pollination. Surprisingly, fungicide also enhanced seed set, suggesting that direct resource costs of soil fungi exceed indirect benefits from reduced larceny. In the tundra, fungicide effects were negligible in both years. However, pooled across treatments, colonization by mycorrhizal fungi in 2009 correlated negatively with the intensity and diversity of floral volatile organic compounds, suggesting integrated above- and belowground signaling pathways. CONCLUSIONS Fungicide effects on floral rewards in P. viscosum link soil fungi to ecological costs of pollinator attraction. Trait-specific linkages to soil fungi should decouple expression of sensitive and buffered floral phenotypes in P. viscosum. Overall, this study demonstrates how multitrophic linkages may lead to shifting selection pressures on interaction traits, restricting the evolution of specialization.
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Affiliation(s)
- Katie M Becklin
- Division of Biological Sciences, University of Missouri, Columbia, Missouri 65211, USA.
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Sahli HF, Conner JK. TESTING FOR CONFLICTING AND NONADDITIVE SELECTION: FLORAL ADAPTATION TO MULTIPLE POLLINATORS THROUGH MALE AND FEMALE FITNESS. Evolution 2011; 65:1457-73. [DOI: 10.1111/j.1558-5646.2011.01229.x] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Heather F. Sahli
- Kellogg Biological Station and Department of Plant Biology
Michigan State University Michigan 49060
- E‐mail:
| | - Jeffrey K. Conner
- Kellogg Biological Station and Department of Plant Biology
Michigan State University Michigan 49060
- E‐mail:
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36
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Galen C, Kaczorowski R, Todd SL, Geib J, Raguso RA. Dosage-Dependent Impacts of a Floral Volatile Compound on Pollinators, Larcenists, and the Potential for Floral Evolution in the Alpine Skypilot Polemonium viscosum. Am Nat 2011; 177:258-72. [DOI: 10.1086/657993] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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37
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Sletvold N, Grindeland JM, Agren J. Pollinator-mediated selection on floral display, spur length and flowering phenology in the deceptive orchid Dactylorhiza lapponica. THE NEW PHYTOLOGIST 2010; 188:385-392. [PMID: 20497348 DOI: 10.1111/j.1469-8137.2010.03296.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
• Nonrewarding animal-pollinated plants commonly experience severe pollen limitation, which should result in strong selection on traits affecting the success of pollination. However, the importance of pollinators as selective agents on floral traits in deceptive species has not been quantified experimentally. • Here, we quantified pollinator-mediated selection (Δβ(poll)) on floral morphology and start of flowering in the deceptive orchid Dactylorhiza lapponica by subtracting estimates of selection gradients for plants receiving supplemental hand-pollination from estimates obtained for open-pollinated control plants. • There was directional selection for taller plants with more flowers and longer spurs, but no statistically significant selection on corolla size or flowering start. Pollinator-mediated selection accounted for all observed selection on spur length (Δβ(poll) = 0.32), 76% of the selection on plant height (Δβ(poll) = 0.19) and 42% of the selection on number of flowers (Δβ(poll = 0.30). Sixteen per cent of developing fruits were consumed by insect herbivores, but fruit herbivory had only minor effects on the strength of pollinator-mediated selection. • Our results demonstrate that pollinators mediate selection on floral traits likely to affect both pollinator attraction and pollination efficiency, and are consistent with the hypothesis that deceptive species experience strong selection for increased display and mechanical fit between flower and pollinator.
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Affiliation(s)
- Nina Sletvold
- NTNU, Museum of Natural History and Archaeology, Trondheim, Norway.
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38
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Parachnowitsch AL, Kessler A. Pollinators exert natural selection on flower size and floral display in Penstemon digitalis. THE NEW PHYTOLOGIST 2010; 188:393-402. [PMID: 20723076 DOI: 10.1111/j.1469-8137.2010.03410.x] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
• A major gap in our understanding of floral evolution, especially micro-evolutionary processes, is the role of pollinators in generating patterns of natural selection on floral traits. Here we explicitly tested the role of pollinators in selecting floral traits in a herbaceous perennial, Penstemon digitalis. • We manipulated the effect of pollinators on fitness through hand pollinations and compared phenotypic selection in open- and hand-pollinated plants. • Despite the lack of pollen limitation in our population, pollinators mediated selection on floral size and floral display. Hand pollinations removed directional selection for larger flowers and stabilizing selection on flower number, suggesting that pollinators were the agents of selection on both of these traits. • We reviewed studies that measured natural selection on floral traits by biotic agents and generally found stronger signatures of selection imposed by pollinators than by herbivores and co-flowering plant species.
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Affiliation(s)
- Amy L Parachnowitsch
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853, USA.
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39
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Boberg E, Ågren J. Despite their apparent integration, spur length but not perianth size affects reproductive success in the moth-pollinated orchidPlatanthera bifolia. Funct Ecol 2009. [DOI: 10.1111/j.1365-2435.2009.01595.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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40
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Harder LD, Johnson SD. Darwin's beautiful contrivances: evolutionary and functional evidence for floral adaptation. THE NEW PHYTOLOGIST 2009; 183:530-545. [PMID: 19552694 DOI: 10.1111/j.1469-8137.2009.02914.x] [Citation(s) in RCA: 221] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Although not 'a professed botanist', Charles Darwin made seminal contributions to understanding of floral and inflorescence function while seeking evidence of adaptation by natural selection. This review considers the legacy of Darwin's ideas from three perspectives. First, we examine the process of floral and inflorescence adaptation by surveying studies of phenotypic selection, heritability and selection responses. Despite widespread phenotypic and genetic capacity for natural selection, only one-third of estimates indicate phenotypic selection. Second, we evaluate experimental studies of floral and inflorescence function and find that they usually demonstrate that reproductive traits represent adaptations. Finally, we consider the role of adaptation in floral diversification. Despite different diversification modes (coevolution, divergent use of the same pollen vector, pollinator shifts), evidence of pollination ecotypes and phylogenetic patterns suggests that adaptation commonly contributes to floral diversity. Thus, this review reveals a contrast between the inconsistent occurrence of phenotypic selection and convincing experimental and comparative evidence that floral traits are adaptations. Rather than rejecting Darwin's hypotheses about floral evolution, this contrast suggests that the tempo of creative selection varies, with strong, consistent selection during episodes of diversification, but relatively weak and inconsistent selection during longer, 'normal' periods of relative phenotypic stasis.
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Affiliation(s)
- Lawrence D Harder
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada T2N 1N4
| | - Steven D Johnson
- School of Biological and Conservation Sciences, University of KwaZulu-Natal, Private Bag X01 Scottsville, Pietermaritzburg 3209, South Africa
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41
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Stinchcombe JR, Weinig C, Heath KD, Brock MT, Schmitt J. Polymorphic genes of major effect: consequences for variation, selection and evolution in Arabidopsis thaliana. Genetics 2009; 182:911-22. [PMID: 19416942 PMCID: PMC2710169 DOI: 10.1534/genetics.108.097030] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2008] [Accepted: 04/24/2009] [Indexed: 11/18/2022] Open
Abstract
The importance of genes of major effect for evolutionary trajectories within and among natural populations has long been the subject of intense debate. For example, if allelic variation at a major-effect locus fundamentally alters the structure of quantitative trait variation, then fixation of a single locus can have rapid and profound effects on the rate or direction of subsequent evolutionary change. Using an Arabidopsis thaliana RIL mapping population, we compare G-matrix structure between lines possessing different alleles at ERECTA, a locus known to affect ecologically relevant variation in plant architecture. We find that the allele present at ERECTA significantly alters G-matrix structure-in particular the genetic correlations between branch number and flowering time traits-and may also modulate the strength of natural selection on these traits. Despite these differences, however, when we extend our analysis to determine how evolution might differ depending on the ERECTA allele, we find that predicted responses to selection are similar. To compare responses to selection between allele classes, we developed a resampling strategy that incorporates uncertainty in estimates of selection that can also be used for statistical comparisons of G matrices.
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Affiliation(s)
- John R Stinchcombe
- Department of Ecology and Evolutionary Biology, Unversity of Toronto, Toronto, Ontario
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Sandring S, Agren J. Pollinator-mediated selection on floral display and flowering time in the perennial herb Arabidopsis lyrata. Evolution 2009; 63:1292-300. [PMID: 19154392 DOI: 10.1111/j.1558-5646.2009.00624.x] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The evolution of floral display and flowering time in animal-pollinated plants is commonly attributed to pollinator-mediated selection. Yet, the causes of selection on flowering phenology and traits contributing to floral display have rarely been tested experimentally in natural populations. We quantified phenotypic selection on morphological and phenological characters in the perennial, outcrossing herb Arabidopsis lyrata in two years using female reproductive success as a proxy of fitness. To determine whether selection on floral display and flowering phenology can be attributed to interactions with pollinators, selection was quantified both for open-pollinated controls and for plants receiving supplemental hand-pollination. We documented directional selection for many flowers, large petals, late start of flowering, and early end of flowering. Seed output was pollen-limited in both years and supplemental hand-pollination reduced the magnitude of selection on number of flowers, and reversed the direction of selection on end of flowering. The results demonstrate that interactions with pollinators may affect the strength of selection on floral display and the direction of selection on phenology of flowering in natural plant populations. They thus support the contention that pollinators can drive the evolution of both floral display and flowering time.
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Affiliation(s)
- Saskia Sandring
- Plant Ecology, Department of Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, Villavägen 14, Uppsala SE-752 36, Sweden.
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Crepet WL, Niklas KJ. Darwin's second 'abominable mystery': Why are there so many angiosperm species? AMERICAN JOURNAL OF BOTANY 2009; 96:366-81. [PMID: 21628194 DOI: 10.3732/ajb.0800126] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
The rapid diversification and ecological dominance of the flowering plants beg the question "Why are there so many angiosperm species and why are they so successful?" A number of equally plausible hypotheses have been advanced in response to this question, among which the most widely accepted highlights the mutually beneficial animal-plant relationships that are nowhere better developed nor more widespread than among angiosperm species and their biotic vectors for pollination and dispersal. Nevertheless, consensus acknowledges that there are many other attributes unique to or characteristic of the flowering plants. In addition, the remarkable coevolution of the angiosperms and pollination/dispersal animal agents could be an effect of the intrinsic adaptability of the flowering plants rather than a primary cause of their success, suggesting that the search for underlying causes should focus on an exploration of the genetic and epigenetic mechanisms that might facilitate adaptive evolution and speciation. Here, we explore angiosperm diversity promoting attributes in their general form and draw particular attention to those that, either individually or collectively, have been shown empirically to favor high speciation rates, low extinction rates, or broad ecological tolerances. Among these are the annual growth form, homeotic gene effects, asexual/sexual reproduction, a propensity for hybrid polyploidy, and apparent "resistance" to extinction. Our survey of the literature suggests that no single vegetative, reproductive, or ecological feature taken in isolation can account for the evolutionary success of the angiosperms. Rather, we believe that the answer to Darwin's second "abominable mystery" lies in a confluence of features that collectively make the angiosperms unique among the land plants.
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Affiliation(s)
- William L Crepet
- Department of Plant Biology, Cornell University, Ithaca, New York 14853 USA
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Irwin RE, Galen C, Rabenold JJ, Kaczorowski R, McCutcheon ML. MECHANISMS OF TOLERANCE TO FLORAL LARCENY IN TWO WILDFLOWER SPECIES. Ecology 2008; 89:3093-3104. [DOI: 10.1890/08-0081.1] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2008] [Revised: 03/04/2008] [Accepted: 03/13/2008] [Indexed: 11/18/2022]
Affiliation(s)
- Rebecca E. Irwin
- Biology Department, Dartmouth College, Hanover, New Hampshire 03755 USA
- Rocky Mountain Biological Laboratory, Crested Butte, Colorado 81224 USA
| | - Candace Galen
- Division of Biological Sciences, University of Missouri, Columbia, Missouri 65211 USA
| | - Jessica J. Rabenold
- Division of Biological Sciences, University of Missouri, Columbia, Missouri 65211 USA
| | - Rainee Kaczorowski
- Division of Biological Sciences, University of Missouri, Columbia, Missouri 65211 USA
| | - Meghan L. McCutcheon
- Rocky Mountain Biological Laboratory, Crested Butte, Colorado 81224 USA
- School of Natural Sciences, Hampshire College, Amherst, Massachusetts 01002 USA
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45
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Caruso CM, Yakobowski SJ. Selection on floral and carbon uptake traits of Lobelia siphilitica is similar in females and hermaphrodites. J Evol Biol 2008; 21:1514-23. [PMID: 18811667 DOI: 10.1111/j.1420-9101.2008.01610.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Sexual dimorphism is common in plants and animals. Although this dimorphism is often assumed to be adaptive, natural selection has rarely been measured on sexually dimorphic traits of plants. We measured phenotypic selection via seed set on two floral and four carbon uptake traits of female and hermaphrodite Lobelia siphilitica. Because females can reproduce only via seeds, which are costlier than pollen, we predicted that females with smaller flowers and enhanced carbon uptake would have higher fitness, resulting in either sex morph-specific directional selection or stabilizing selection for different optimal trait values in females and hermaphrodites. We found that directional selection on one carbon uptake trait differed between females and hermaphrodites. We did not detect significant stabilizing selection on traits of either sex morph. Our results provide little support for the hypothesis that sexual dimorphism in gynodioecious plants evolved in response to sex morph-specific selection.
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Affiliation(s)
- C M Caruso
- Department of Integrative Biology, University of Guelph, Guelph, ON, Canada.
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46
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Day–night fluctuations in floral scent and their effects on reproductive success in Lilium auratum. POPUL ECOL 2008. [DOI: 10.1007/s10144-008-0097-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Kutschera U, Niklas KJ. Macroevolution via secondary endosymbiosis: a Neo-Goldschmidtian view of unicellular hopeful monsters and Darwin’s primordial intermediate form. Theory Biosci 2008; 127:277-89. [DOI: 10.1007/s12064-008-0046-8] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2008] [Accepted: 06/02/2008] [Indexed: 10/21/2022]
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48
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Feulner M, Möseler BM, Nezadal W. Introgression und morphologische Variabilität bei der Blauen Himmelsleiter, Polemonium caeruleum L. in Nordbayern, Deutschland. ACTA ACUST UNITED AC 2008. [DOI: 10.1002/fedr.20011120306] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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49
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Muchhala N. Adaptive Trade‐Off in Floral Morphology Mediates Specialization for Flowers Pollinated by Bats and Hummingbirds. Am Nat 2007; 169:494-504. [PMID: 17427121 DOI: 10.1086/512047] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2006] [Accepted: 10/02/2006] [Indexed: 11/04/2022]
Abstract
Evolution toward increased specificity in pollination systems is thought to have played a central role in the diversification of angiosperms. Theory predicts that the presence of trade-offs in adapting to different pollinator types will favor specialization, yet few studies have attempted to characterize such interactions in nature. I conducted flight cage experiments with bats, hummingbirds, and artificial flowers to examine effects of corolla width on pollination. I videotaped visits to analyze pollinator behavior and counted pollen grains transferred to stigmas. Results demonstrated that flower-pollinator fit is critical to effective pollination; wide corollas guided bat snouts better, and narrow corollas guided hummingbird bills better. Poor fit resulted in variable entry angles and decreased pollen transfer. A model using these results predicts that wide corollas will be selected for when bats make more than 44% of the visits and narrow corollas when they make fewer. Intermediate corollas are never favored (i.e., generalization is always suboptimal). This is the first study to clearly document a pollinator-mediated fitness trade-off in floral morphology.
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Affiliation(s)
- Nathan Muchhala
- Department of Biology, University of Miami, Miami, Florida 33143, USA.
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Galliot C, Hoballah ME, Kuhlemeier C, Stuurman J. Genetics of flower size and nectar volume in Petunia pollination syndromes. PLANTA 2006; 225:203-12. [PMID: 16871396 DOI: 10.1007/s00425-006-0342-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2006] [Accepted: 05/31/2006] [Indexed: 05/11/2023]
Abstract
The two related Petunia species, P. axillaris and P. integrifolia, are sympatric at various locations in South America but do not hybridise. Divergent pollinator preferences are believed to be in part responsible for their reproductive isolation. The volume of nectar produced and several components of flower morphology might contribute to pollinator-dependant reproductive isolation. In this study, we aimed to identify the genetic changes underlying the quantitative differences observed between these two Petunia species in flower size and nectar volume. We mapped quantitative trait loci (QTL) responsible for the different phenotypes of P. axillaris and P. integrifolia in an inter-specific backcross population. QTL of small to moderate effect control the differences in flower size and volume of nectar. In addition, we observed strong suppression of meiotic recombination in Petunia, even between closely related species, which precluded a fine resolution of QTL mapping. Thus, our data suggest that flower size and nectar volume are highly polygenic. They are likely to have evolved gradually through pollinator-mediated adaptation or reinforcement, and are not likely to have been primary factors in early steps of pollinator isolation of P. axillaris and P. integrifolia.
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Affiliation(s)
- Céline Galliot
- Institute of Plant Sciences, University of Berne, Altenbergrain 21, 3013 Berne, Switzerland.
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