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Johnson SE, Hamann E, Franks SJ. Rapid-cycling Brassica rapa evolves even earlier flowering under experimental drought. AMERICAN JOURNAL OF BOTANY 2022; 109:1683-1692. [PMID: 35587234 DOI: 10.1002/ajb2.16002] [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: 12/09/2021] [Revised: 04/14/2022] [Accepted: 04/14/2022] [Indexed: 06/15/2023]
Abstract
PREMISE Changes in climate can impose selection on populations and may lead to rapid evolution. One such climatic stress is drought, which plant populations may respond to with escape (rapid growth and early flowering) or avoidance (slow growth and efficient water-use). However, it is unclear if drought escape would be a viable strategy for populations that already flower early from prior selection. METHODS In an experimental evolution study, we subjected rapid-cycling Brassica rapa (RCBr), which was previously selected for early flowering, to four generations of experimental drought or watered conditions. We then grew ancestral and descendant populations concurrently under drought and watered conditions to assess evolution, plasticity, and adaptation. RESULTS The RCBr populations that evolved under drought had earlier flowering and lower water-use efficiency than the populations that evolved under watered conditions, indicating evolutionary divergence. The drought descendants also had a trend of earlier flowering compared to ancestors, indicating evolution. Evolution of earlier flowering under drought followed the direction of selection and increased fitness and was consistent with studies in natural and experimental populations of this species, suggesting adaptive evolution. CONCLUSIONS We found rapid adaptive evolution of drought escape in RCBr and little evidence for constraints on flowering time evolution, even though RCBr already flowers extremely early. Our results suggest that some populations may harbor sufficient genetic variation for evolution even after strong selection has occurred. Our study also illustrates the utility of combining artificial selection, experimental evolution, and the resurrection approach to study the evolution of functional traits.
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Affiliation(s)
- Stephen E Johnson
- Department of Biological Sciences, Fordham University, Bronx, NY, 10458, USA
| | - Elena Hamann
- Department of Biological Sciences, Fordham University, Bronx, NY, 10458, USA
| | - Steven J Franks
- Department of Biological Sciences, Fordham University, Bronx, NY, 10458, USA
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2
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Relaxed selection and the evolution of the chasmogamous flower of Impatiens capensis (Balsaminaceae). Evol Ecol 2022. [DOI: 10.1007/s10682-022-10155-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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3
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Gao L, Yu G, Hu F, Li Z, Li W, Peng C. The Patterns of Male and Female Flowers in Flowering Stage May Not Be Optimal Resource Allocation for Fruit and Seed Growth. PLANTS (BASEL, SWITZERLAND) 2021; 10:plants10122819. [PMID: 34961290 PMCID: PMC8706146 DOI: 10.3390/plants10122819] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Revised: 12/14/2021] [Accepted: 12/15/2021] [Indexed: 06/14/2023]
Abstract
Changes in the proportions of male and female flowers in monoecious plants in response to external environmental conditions are directly related to the reproductive fitness of plants. The monoecious cucumber (Cucumber sativus) plant was used in this study to assess the responses of sex differentiation and the breeding process to nutrient supply and the degree of artificial pollination using pollen solutions of different concentrations. We found that the nutrient supply significantly improved the number of female flowers, while pollination treatments did not obviously increase the number of male flowers. Continuous pollination changed the number of female flowers especially in the later stage of the pollination experiment. Therefore, pollination changed the ratio of male and female flowers in the flowering stage of cucumber. Pollination treatment affected the fruit growth, seed set, and fruit yield. The number of fruit, fruit set percentage, and total seeds per plant did not increase with the pollination level, but individual fruit weight and seed number in one fruit did increase. The differentiation of male and female flowers in the flowering stage of cucumber is a response to nutrient and pollination resources, but this response is not the optimal resource allocation for subsequent fruit development and seed maturity, which suggests that the response of plants to external environment resources is short-term and direct.
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Waterton J, Mazer SJ, Meyer JR, Cleland EE. Trade-off drives Pareto optimality of within- and among-year emergence timing in response to increasing aridity. Evol Appl 2021; 14:658-673. [PMID: 33767742 PMCID: PMC7980269 DOI: 10.1111/eva.13145] [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: 01/10/2020] [Revised: 08/20/2020] [Accepted: 09/22/2020] [Indexed: 11/30/2022] Open
Abstract
Adaptation to current and future climates can be constrained by trade-offs between fitness-related traits. Early seedling emergence often enhances plant fitness in seasonal environments, but if earlier emergence in response to seasonal cues is genetically correlated with lower potential to spread emergence among years (i.e., bet-hedging), then this functional trade-off could constrain adaptive evolution. Consequently, selection favoring both earlier within-year emergence and greater spread of emergence among years-as is expected in more arid environments-may constrain adaptive responses to trait value combinations at which a performance gain in either function (i.e., evolving earlier within- or greater among-year emergence) generates a performance loss in the other. All such trait value combinations that cannot be improved for both functions simultaneously are described as Pareto optimal and together constitute the Pareto front. To investigate how this potential emergence timing trade-off might constrain adaptation to increasing aridity, we sourced seeds of two grasses, Stipa pulchra and Bromus diandrus, from multiple maternal lines within populations across an aridity gradient in California and examined their performance in a greenhouse experiment. We monitored emergence and assayed ungerminated seeds for viability to determine seed persistence, a metric of potential among-year emergence spread. In both species, maternal lines with larger fractions of persistent seeds emerged later, indicating a trade-off between within-year emergence speed and potential among-year emergence spread. In both species, populations on the Pareto front for both earlier emergence and larger seed persistence fraction occupied significantly more arid sites than populations off the Pareto front, consistent with the hypothesis that more arid sites impose the strongest selection for earlier within-year emergence and greater among-year emergence spread. Our results provide an example of how evaluating genetically based correlations within populations and applying Pareto optimality among populations can be used to detect evolutionary constraints and adaptation across environmental gradients.
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Affiliation(s)
- Joseph Waterton
- Ecology, Behavior & Evolution SectionUniversity of California San DiegoLa JollaCAUSA
| | - Susan J. Mazer
- Department of Ecology, Evolution and Marine BiologyUniversity of California Santa BarbaraSanta BarbaraCAUSA
| | - Justin R. Meyer
- Ecology, Behavior & Evolution SectionUniversity of California San DiegoLa JollaCAUSA
| | - Elsa E. Cleland
- Ecology, Behavior & Evolution SectionUniversity of California San DiegoLa JollaCAUSA
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5
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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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Aguiar JMRBV, Maciel AA, Santana PC, Telles FJ, Bergamo PJ, Oliveira PE, Brito VLG. Intrafloral Color Modularity in a Bee-Pollinated Orchid. FRONTIERS IN PLANT SCIENCE 2020; 11:589300. [PMID: 33304366 PMCID: PMC7693458 DOI: 10.3389/fpls.2020.589300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Accepted: 10/15/2020] [Indexed: 05/11/2023]
Abstract
Flower color has been studied in different ecological levels of organization, from individuals to communities. However, it is unclear how color is structured at the intrafloral level. In bee-pollinated flowers, the unidirectional gradient in color purity and pollen mimicry are two common processes to explain intrafloral color patterns. Considering that floral traits are often integrated, usually reflecting evolutionary modules under pollinator-mediated selection, we hypothesize that such intrafloral color patterns are structured by intrafloral color modules as perceived by bee color vision system. Here, we studied the tropical bee-pollinated orchid Cattleya walkeriana, given its intrafloral color complexity and variation among individuals. Considering bee color vision, we investigated if intrafloral color modules arose among intrafloral patches (tip or base of the sepals, petals, and labellum). We expected a separate color module between the labellum patches (the main attractive structure in orchids) and petals and sepals. We measured the color reflectance and calculated the photoreceptor excitation, spectral purity, hue, and the chromatic contrast of the floral structures in the hexagon color model. Spectral purity (saturation) was higher in the labellum tip in comparison to petals and sepals, generating a unidirectional gradient. Labellum base presented a less saturated yellow UV-absorbing color, which may reflect a pollen mimicry strategy. C. walkeriana presented three intrafloral color modules corresponding to the color of petals and sepals, the color of the labellum tip, and the color of labellum base. These color modules were unrelated to the development of floral structures. Given the importance of intrafloral color patterns in bee attraction and guidance, our results suggest that intrafloral patterns could be the outcome of evolutionary color modularization under pollinator-mediated selection.
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Affiliation(s)
- João Marcelo Robazzi Bignelli Valente Aguiar
- Programa de Pós-Graduação em Entomologia, Departamento de Biologia, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | - Artur Antunes Maciel
- Programa de Pós-Graduação em Ecologia e Conservação dos Recursos Naturais, Instituto de Biologia, Universidade Federal de Uberlândia, Uberlândia, Brazil
| | - Pamela Cristina Santana
- Programa de Pós-Graduação em Ecologia, Departamento de Ecologia, Universidade de São Paulo, São Paulo, Brazil
| | - Francismeire Jane Telles
- Programa de Pós-Graduação em Ecologia e Conservação dos Recursos Naturais, Instituto de Biologia, Universidade Federal de Uberlândia, Uberlândia, Brazil
| | | | | | - Vinicius Lourenço Garcia Brito
- Instituto de Biologia, Universidade Federal de Uberlândia, Uberlândia, Brazil
- *Correspondence: Vinicius Lourenço Garcia Brito,
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Spigler RB, Woodard AJ. Context-dependency of resource allocation trade-offs highlights constraints to the evolution of floral longevity in a monocarpic herb. THE NEW PHYTOLOGIST 2019; 221:2298-2307. [PMID: 30256414 DOI: 10.1111/nph.15498] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Accepted: 09/14/2018] [Indexed: 06/08/2023]
Abstract
Floral longevity is a critical component of floral display, yet there is a conspicuous paucity of empirical research on its evolution within species. Evolutionary models of floral longevity are grounded in resource allocation theory and propose that selection acts on heritable variation to optimize longevity in light of competing floral construction and maintenance costs. Key assumptions remain untested within wild species. We measured maximum floral longevity alongside protandry, flower size, flower number and flowering rate across families of the monocarpic herb Sabatia angularis grown under high and low resources. We evaluated genetic variation, plasticity and correlations between display traits, including fundamental resource-allocation trade-offs and their interactions with resource availability. All display traits showed significant genetic variation. Resource availability influenced mean floral longevity and flower number, with genetic variation in these responses. Importantly, both floral longevity-flower number and flower number-size trade-offs were significant and stronger under low resources. This study reinforces the application of resource allocation theory to floral display trait evolution. Our work highlights the context-dependency of trade-offs and the potential importance of plasticity in resource allocation, with plants investing in the construction of new flowers at faster rates when resources are high rather than in the maintenance of longer-lived flowers.
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Affiliation(s)
- Rachel B Spigler
- Department of Biology, Temple University, 1900 N. 12th Street, Philadelphia, PA, 19122, USA
| | - Alyssa J Woodard
- Department of Biology, Temple University, 1900 N. 12th Street, Philadelphia, PA, 19122, USA
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Landis JB, Bell CD, Hernandez M, Zenil-Ferguson R, McCarthy EW, Soltis DE, Soltis PS. Evolution of floral traits and impact of reproductive mode on diversification in the phlox family (Polemoniaceae). Mol Phylogenet Evol 2018; 127:878-890. [DOI: 10.1016/j.ympev.2018.06.035] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Revised: 06/20/2018] [Accepted: 06/20/2018] [Indexed: 01/19/2023]
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9
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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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10
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Zu P, Schiestl FP. The effects of becoming taller: direct and pleiotropic effects of artificial selection on plant height in Brassica rapa. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2017; 89:1009-1019. [PMID: 27889935 DOI: 10.1111/tpj.13440] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Revised: 10/07/2016] [Accepted: 11/18/2016] [Indexed: 06/06/2023]
Abstract
Plant height is an important trait for plant reproductive success. Plant height is often under pollinator-mediated selection, and has been shown to be correlated with various other traits. However, few studies have examined the evolutionary trajectory of plant height under selection and the pleiotropic effects of plant height evolution. We conducted a bi-directional artificial selection experiment on plant height with fast cycling Brassica rapa plants to estimate its heritability and genetic correlations, and to reveal evolutionary responses to artificial selection on height and various correlated traits. With the divergent lines obtained through artificial selection, we subsequently conducted pollinator-choice assays and investigated resource limitation of fruit production. We found that plant height variation is strongly genetically controlled (with a realized heritability of 41-59%). Thus, plant height can evolve rapidly under phenotypic selection. In addition, we found remarkable pleiotropic effects in phenology, morphology, floral scent, color, nectar and leaf glucosinolates. Most traits were increased in tall-line plants, but flower size, UV reflection and glucosinolates were decreased, indicating potential trade-offs. Pollinators preferred plants of the tall selection lines over the short selection lines in both greenhouse experiments with bumblebees and field experiment with natural pollinators. We did not detect any differences in resource limitation between plants of the different selection lines. Overall, our study predicts that increased height should evolve under positive pollinator-mediated directional selection with potential trade-offs in floral signals and herbivore defense.
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Affiliation(s)
- Pengjuan Zu
- Department of Systematic and Evolutionary Botany, University of Zürich, Zollikerstrasse 107, CH-8008 Zürich, Switzerland
| | - Florian P Schiestl
- Department of Systematic and Evolutionary Botany, University of Zürich, Zollikerstrasse 107, CH-8008 Zürich, Switzerland
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11
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Puentes A, Granath G, Ågren J. Similarity in G matrix structure among natural populations of Arabidopsis lyrata. Evolution 2016; 70:2370-2386. [PMID: 27501272 DOI: 10.1111/evo.13034] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Accepted: 07/25/2016] [Indexed: 12/31/2022]
Abstract
Understanding the stability of the G matrix in natural populations is fundamental for predicting evolutionary trajectories; yet, the extent of its spatial variation and how this impacts responses to selection remain open questions. With a nested paternal half-sib crossing design and plants grown in a field experiment, we examined differences in the genetic architecture of flowering time, floral display, and plant size among four Scandinavian populations of Arabidopsis lyrata. Using a multivariate Bayesian framework, we compared the size, shape, and orientation of G matrices and assessed their potential to facilitate or constrain trait evolution. Flowering time, floral display and rosette size varied among populations and significant additive genetic variation within populations indicated potential to evolve in response to selection. Yet, some characters, including flowering start and number of flowers, may not evolve independently because of genetic correlations. Using a multivariate framework, we found few differences in the genetic architecture of traits among populations. G matrices varied mostly in size rather than shape or orientation. Differences in multivariate responses to selection predicted from differences in G were small, suggesting overall matrix similarity and shared constraints to trait evolution among populations.
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Affiliation(s)
- Adriana Puentes
- Department of Plant Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-752 36 Uppsala, Sweden. .,Department of Ecology, Swedish University of Agricultural Sciences, SE-750 07 Uppsala, Sweden.
| | - Gustaf Granath
- Department of Plant Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-752 36 Uppsala, Sweden.,Department of Ecology, Swedish University of Agricultural Sciences, SE-750 07 Uppsala, Sweden
| | - Jon Ågren
- Department of Plant Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-752 36 Uppsala, Sweden
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12
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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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13
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Griswold CK. Additive genetic variation and evolvability of a multivariate trait can be increased by epistatic gene action. J Theor Biol 2015; 387:241-57. [DOI: 10.1016/j.jtbi.2015.09.023] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Revised: 08/26/2015] [Accepted: 09/17/2015] [Indexed: 10/22/2022]
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14
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Cao GX, Worley AC. Life history trade-offs and evidence for hierarchical resource allocation in two monocarpic perennials. PLANT BIOLOGY (STUTTGART, GERMANY) 2013; 15:158-165. [PMID: 22672109 DOI: 10.1111/j.1438-8677.2012.00612.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The evolution of floral display is thought to be constrained by trade-offs between the size and number of flowers; however, empirical evidence for the trade-off is inconsistent. We examined evidence for trade-offs and hierarchical allocation of resources within and between two populations each of the monocarpic perennials, Cardiocrinum cordatum and C. giganteum. Within all populations, flower size-number trade-offs were evident after accounting for variation in plant size. In addition, variation in flower size explained much variation in flower-level allocation to attraction, and female and male function, a pattern consistent with hierarchical allocation. However, between population differences in flower size (C. cordatum) and number (C. giganteum) were not consistent with size-number trade-offs or hierarchical allocation. The population-level difference in C. cordatum likely reflects the combined influence of a time lag between initiation and maturation of flowers, and higher light levels in one population. Thus, our study highlights one mechanism that may account for the apparent independence of flower size and number in many studies. A prediction of sex allocation theory was also supported. In C. giganteum: plants from one population invested more mass in pistils and less in stamens than did plants from the other population. Detection of floral trade-offs in Cardiocrinum may be facilitated by monocarpic reproduction, production of a single inflorescence and ease of measuring plant size.
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Affiliation(s)
- G-X Cao
- Department of Forestry, Sichuan Agricutural University, Yaan, China.
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15
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Chaney L, Baucom RS. The evolutionary potential of Baker's weediness traits in the common morning glory, Ipomoea purpurea (Convolvulaceae). AMERICAN JOURNAL OF BOTANY 2012; 99:1524-1530. [PMID: 22922396 DOI: 10.3732/ajb.1200096] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
PREMISE OF THE STUDY Many reports have cited Baker's list of weediness traits, or those that exemplify the "ideal" weed, yet few have considered the evolutionary potential of such traits as a group. Thus, it is unknown whether constraints on the evolution of increased weediness, such as a lack of genetic variation or genetic correlations between the traits, are present. Ipomoea purpurea, the common morning glory, is a problematic weed that exhibits many of Baker's ideal weed traits. METHODS We used progeny from a half/full-sib breeding design in a series of three greenhouse experiments to assess the presence of genetic variation, narrow sense heritabilities, and genetic correlations in Baker's growth, competition, and fitness "weediness" traits in two populations of I. purpurea. KEY RESULTS We uncovered genetic variation underlying reproductive fitness traits and competitive ability in at least one population, but no evidence of genetic variation underlying growth rate in either population. Genetic correlations between many of the weediness characters differed significantly from zero; however, their direction and/or magnitude differed between populations. CONCLUSIONS We found that increased weediness in the common morning glory is more likely to occur through selection on reproductive output and competitive ability rather than through selection on growth rate. Assessing Baker's traits in a quantitative genetics framework can provide a solid perspective on their evolutionary potential and a unique framework within which to determine how weeds will respond to different environmental stresses and/or scenarios of global climate change.
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Affiliation(s)
- Lindsay Chaney
- Department of Biological Sciences, 721 Rieveschl Hall, University of Cincinnati, Cincinnati, Ohio 45221, USA
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Lamy JB, Bouffier L, Burlett R, Plomion C, Cochard H, Delzon S. Uniform selection as a primary force reducing population genetic differentiation of cavitation resistance across a species range. PLoS One 2011; 6:e23476. [PMID: 21858137 PMCID: PMC3155568 DOI: 10.1371/journal.pone.0023476] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2011] [Accepted: 07/19/2011] [Indexed: 11/18/2022] Open
Abstract
Background Cavitation resistance to water stress-induced embolism determines plant survival during drought. This adaptive trait has been described as highly variable in a wide range of tree species, but little is known about the extent of genetic and phenotypic variability within species. This information is essential to our understanding of the evolutionary forces that have shaped this trait, and for evaluation of its inclusion in breeding programs. Methodology We assessed cavitation resistance (P50), growth and carbon isotope composition in six Pinus pinaster populations in a provenance and progeny trial. We estimated the heritability of cavitation resistance and compared the distribution of neutral markers (FST) and quantitative genetic differentiation (QST), for retrospective identification of the evolutionary forces acting on these traits. Results/Discussion In contrast to growth and carbon isotope composition, no population differentiation was found for cavitation resistance. Heritability was higher than for the other traits, with a low additive genetic variance (h2ns = 0.43±0.18, CVA = 4.4%). QST was significantly lower than FST, indicating uniform selection for P50, rather than genetic drift. Putative mechanisms underlying QST<FST are discussed.
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Affiliation(s)
- Jean-Baptiste Lamy
- INRA, UMR 1202 BIOGECO, F-33610 Cestas, France
- Université de Bordeaux, UMR 1202 BIOGECO, F-33610 Cestas, France
- INRA, UMR 547 PIAF, University of Blaise Pascal, F-63100 Clermont-Ferrand, France
| | - Laurent Bouffier
- INRA, UMR 1202 BIOGECO, F-33610 Cestas, France
- FCBA, Station Sud-Ouest, Domaine de Sivaillan, F-33480 Moulis en Médoc, France
| | - Régis Burlett
- INRA, UMR 1202 BIOGECO, F-33610 Cestas, France
- Université de Bordeaux, UMR 1202 BIOGECO, F-33610 Cestas, France
| | - Christophe Plomion
- INRA, UMR 1202 BIOGECO, F-33610 Cestas, France
- Université de Bordeaux, UMR 1202 BIOGECO, F-33610 Cestas, France
| | - Hervé Cochard
- INRA, UMR 547 PIAF, University of Blaise Pascal, F-63100 Clermont-Ferrand, France
| | - Sylvain Delzon
- INRA, UMR 1202 BIOGECO, F-33610 Cestas, France
- Université de Bordeaux, UMR 1202 BIOGECO, F-33610 Cestas, France
- * E-mail:
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Sicard A, Lenhard M. The selfing syndrome: a model for studying the genetic and evolutionary basis of morphological adaptation in plants. ANNALS OF BOTANY 2011; 107:1433-43. [PMID: 21303786 PMCID: PMC3108801 DOI: 10.1093/aob/mcr023] [Citation(s) in RCA: 217] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2010] [Revised: 11/17/2010] [Accepted: 01/04/2011] [Indexed: 05/05/2023]
Abstract
BACKGROUND In angiosperm evolution, autogamously selfing lineages have been derived from outbreeding ancestors multiple times, and this transition is regarded as one of the most common evolutionary tendencies in flowering plants. In most cases, it is accompanied by a characteristic set of morphological and functional changes to the flowers, together termed the selfing syndrome. Two major areas that have changed during evolution of the selfing syndrome are sex allocation to male vs. female function and flower morphology, in particular flower (mainly petal) size and the distance between anthers and stigma. SCOPE A rich body of theoretical, taxonomic, ecological and genetic studies have addressed the evolutionary modification of these two trait complexes during or after the transition to selfing. Here, we review our current knowledge about the genetics and evolution of the selfing syndrome. CONCLUSIONS We argue that because of its frequent parallel evolution, the selfing syndrome represents an ideal model for addressing basic questions about morphological evolution and adaptation in flowering plants, but that realizing this potential will require the molecular identification of more of the causal genes underlying relevant trait variation.
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Affiliation(s)
| | - Michael Lenhard
- Institut für Biochemie und Biologie, Universität Potsdam, Karl-Liebknecht-Straße 24–25, D-14476 Potsdam, Germany
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Rosas-Guerrero V, Quesada M, Armbruster WS, Pérez-Barrales R, Smith SD. INFLUENCE OF POLLINATION SPECIALIZATION AND BREEDING SYSTEM ON FLORAL INTEGRATION AND PHENOTYPIC VARIATION IN IPOMOEA. Evolution 2010; 65:350-64. [DOI: 10.1111/j.1558-5646.2010.01140.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Flanagan RJ, Mitchell RJ, Karron JD. Effects of multiple competitors for pollination on bumblebee foraging patterns and Mimulus ringens reproductive success. OIKOS 2010. [DOI: 10.1111/j.1600-0706.2010.18777.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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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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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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Gómez JM, Abdelaziz M, Muñoz-Pajares J, Perfectti F. HERITABILITY AND GENETIC CORRELATION OF COROLLA SHAPE AND SIZE INERYSIMUM MEDIOHISPANICUM. Evolution 2009; 63:1820-31. [DOI: 10.1111/j.1558-5646.2009.00667.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Agrawal AF, Stinchcombe JR. How much do genetic covariances alter the rate of adaptation? Proc Biol Sci 2009; 276:1183-91. [PMID: 19129097 DOI: 10.1098/rspb.2008.1671] [Citation(s) in RCA: 180] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Genetically correlated traits do not evolve independently, and the covariances between traits affect the rate at which a population adapts to a specified selection regime. To measure the impact of genetic covariances on the rate of adaptation, we compare the rate fitness increases given the observed G matrix to the expected rate if all the covariances in the G matrix are set to zero. Using data from the literature, we estimate the effect of genetic covariances in real populations. We find no net tendency for covariances to constrain the rate of adaptation, though the quality and heterogeneity of the data limit the certainty of this result. There are some examples in which covariances strongly constrain the rate of adaptation but these are balanced by counter examples in which covariances facilitate the rate of adaptation; in many cases, covariances have little or no effect. We also discuss how our metric can be used to identify traits or suites of traits whose genetic covariances to other traits have a particularly large impact on the rate of adaptation.
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Affiliation(s)
- Aneil F Agrawal
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario, Canada M5S 3B2.
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Sherrard ME, Maherali H, Latta RG. WATER STRESS ALTERS THE GENETIC ARCHITECTURE OF FUNCTIONAL TRAITS ASSOCIATED WITH DROUGHT ADAPTATION INAVENA BARBATA. Evolution 2009; 63:702-15. [DOI: 10.1111/j.1558-5646.2008.00580.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Smith RA, Rausher MD. SELECTION FOR CHARACTER DISPLACEMENT IS CONSTRAINED BY THE GENETIC ARCHITECTURE OF FLORAL TRAITS IN THE IVYLEAF MORNING GLORY. Evolution 2008; 62:2829-41. [DOI: 10.1111/j.1558-5646.2008.00494.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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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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Smith SD, Ané C, Baum DA. THE ROLE OF POLLINATOR SHIFTS IN THE FLORAL DIVERSIFICATION OFIOCHROMA(SOLANACEAE). Evolution 2008; 62:793-806. [DOI: 10.1111/j.1558-5646.2008.00327.x] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Sargent RD, Goodwillie C, Kalisz S, Ree RH. Phylogenetic evidence for a flower size and number trade-off. AMERICAN JOURNAL OF BOTANY 2007; 94:2059-2062. [PMID: 21636399 DOI: 10.3732/ajb.94.12.2059] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The size and number of flowers displayed together on an inflorescence (floral display) influences pollinator attraction and pollen transfer and receipt, and is integral to plant reproductive success and fitness. Life history theory predicts that the evolution of floral display is constrained by trade-offs between the size and number of flowers and inflorescences. Indeed, a trade-off between flower size and flower number is a key assumption of models of inflorescence architecture and the evolution of floral display. Surprisingly, however, empirical evidence for the trade-off is limited. In particular, there is a lack of phylogenetic evidence for a trade-off between flower size and number. Analyses of phylogenetic independent contrasts (PICs) of 251 angiosperm species spanning 63 families yielded a significant negative correlation between flower size and flower number. At smaller phylogenetic scales, analyses of individual genera did not always find evidence of a trade-off, a result consistent with previous studies that have examined the trade-off for a single species or genus. Ours is the first study to support an angiosperm-wide trade-off between flower size and number and supports the theory that life history constraints have influenced the evolution of floral display.
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Affiliation(s)
- Risa D Sargent
- Department of Integrative Biology, University of California, Berkeley, California 94720-3140 USA
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Brock MT, Weinig C. Plasticity and environment-specific covariances: an investigation of floral-vegetative and within flower correlations. Evolution 2007; 61:2913-24. [PMID: 17941839 DOI: 10.1111/j.1558-5646.2007.00240.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Floral traits are commonly thought to be more canalized than vegetative ones. In addition, floral and vegetative traits are hypothesized to be genetically decoupled, enabling vegetative structures to respond plastically to environmental heterogeneity, and to evolve in response to selection without disrupting the reproductive function of flowers. To test these hypotheses, we evaluate the genetic architecture of floral and vegetative traits in natural populations of Arabidopsis thaliana raised under variable light-quality environments. Plants were grown either under high or low ratios of red to far-red (R:FR) light, an aspect of light quality that varies with neighbor proximity and regulates competitive shade-avoidance responses. Across environments, we detected significant genetic variation for the average expression of all measured floral traits (petal length and width, stamen length, pistil length, stigma-anther separation, and exsertion of both the stamen and pistil beyond the corolla). Light quality significantly influenced the absolute size of several floral traits as well as the allometry (i.e., relative scaling) of all floral traits, and genotypes differed in the plasticity of floral traits to the light treatments. Exposure to low relative to high R:FR resulted in significantly greater elongation in the vegetative trait, petiole length, and genotypes again differed in the plasticity of this trait to R:FR. Consistent with prior studies, most floral traits were less plastic than the vegetative trait; herkogamy (i.e., stigma-anther separation) was the exception and expressed more variable trait values across environments than petiole length, apparently as a consequence of the independent responses of stamens and pistils. Flowers also showed strong phenotypic integration; genotypic correlations were significantly positive among floral traits within each light treatment. Although floral-vegetative correlations were not significant in the high R:FR light treatment, significant correlations were detected between petal traits, pistil length, and petiole length under low R:FR, in contrast to the widely held hypothesis that floral and vegetative traits are genetically independent. Finally, we detected selection for reduced herkogamy in the low R:FR light treatment. The observed correlation between functional trait groups suggest that vegetative plasticity may affect the expression of floral traits in some environments, and that environment-specific constraints may exist on the evolution of floral and vegetative traits.
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Affiliation(s)
- Marcus T Brock
- Department of Plant Biology, University of Minnesota, Saint Paul, Minnesota 55108, USA.
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Miller JS, Diggle PK. Correlated evolution of fruit size and sexual expression in andromonoecious Solanum sections Acanthophora and Lasiocarpa (Solanaceae). AMERICAN JOURNAL OF BOTANY 2007; 94:1706-15. [PMID: 21636367 DOI: 10.3732/ajb.94.10.1706] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Andromonoecy is hypothesized to evolve as a mechanism enabling plants to independently allocate resources to female and male function. If staminate flower production is a mechanism to regulate allocation to female function (i.e., fruit production), then large-fruited species should be more strongly andromonoecious than smaller-fruited taxa because more resources are required to mature large fruit. We combined phylogenetically independent contrast analyses with extensive phenotypic characterization under common greenhouse conditions to examine the predicted relationship between fruit mass and the strength of andromonoecy among 13 species in Solanum sections Acanthophora and Lasiocarpa. The strength of andromonoecy, defined as the proportion of staminate flowers produced within inflorescences, was significantly and positively associated with fruit mass in both naïve and phylogenetically independent analyses. Our results are consistent with the hypothesis that andromonoecy functions as a mechanism to regulate allocation to female function and suggest that the strength of andromonoecy is also associated with resource limitation. In general, we find that strong andromonoecy appears to arise via reductions in hermaphroditic flower number. However, increases in staminate flowers have also contributed to transitions to strong andromonoecy in certain species. Finally, our analyses identified a suite of correlated characters (flower size, ovary width, fruit mass) that are associated with changes in the sexual expression of andromonoecy.
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Affiliation(s)
- Jill S Miller
- Department of Biology, Amherst College, Amherst, Massachusetts 01002 USA
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Ashman TL. The limits on sexual dimorphism in vegetative traits in a gynodioecious plant. Am Nat 2007; 166 Suppl 4:S5-16. [PMID: 16224712 DOI: 10.1086/444598] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Gynodioecious plants exhibit modest sexual dimorphism in vegetative and phenological traits, which stands in stark contrast to pronounced dimorphism in reproductive traits. I evaluate the roles of limited genetic variation, negative genetic covariation (within and between sex morphs), and lack of gender-differential selection in contributing to minimal sexual dimorphism for these traits in Fragaria virginiana. Major findings are as follows. First, selection was sometimes differential but rarely divergent between male and female fertility modes. Second, response to selection was constrained by low genetic variation and extensive genetic covariance. In fact, covariance between traits within sex morphs appears to represent a constraint on par with that of covariance between sex morphs. Third, these constraints combine with different modes of gamete transmission to produce very different gender-specific contributions to the mean phenotypes of the next generation. Finally, predicted responses to selection for several traits are concordant with the degree and direction of dimorphism in a closely related dioecious species. In sum, this work suggests that minimal sexual dimorphism in vegetative and phenological traits is due to similar directional selection via male and female fertility combined with the constraints of low genetic variation and extensive genetic covariance both within and between sex morphs.
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Affiliation(s)
- Tia-Lynn Ashman
- Department Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA.
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Lambrecht SC, Dawson TE. Correlated variation of floral and leaf traits along a moisture availability gradient. Oecologia 2006; 151:574-83. [PMID: 17180373 DOI: 10.1007/s00442-006-0617-7] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2006] [Accepted: 11/08/2006] [Indexed: 10/23/2022]
Abstract
Variation in flower size is an important aspect of a plant's life history, yet few studies have shown how flower size varies with environmental conditions and to what extent foliar responses to the environment are correlated with flower size. The objectives of this study were to (1) develop a theoretical framework for linking flower size and leaf size to their costs and benefits, as assessed using foliar stable carbon isotope ratio (delta(13)C) under varying degrees of water limitation, and then (2) examine how variation in flower size within and among species growing along a naturally occurring moisture availability gradient correlates with variation in delta(13)C and leaf size. Five plant species were examined at three sites in Oregon. Intra- and inter-specific patterns of flower size in relation to moisture availability were the same: the ratios of the area of flower display to total leaf area and of individual flower area to leaf area were greater at sites with more soil moisture compared to those sites with less soil moisture. The increase in flower area per unit increase in leaf area was greater at sites with more soil moisture than at sites where water deficit can occur. Values of delta(13)C, an index of water-use efficiency, were greater for plants with larger floral size. The patterns we observed generalize across species, irrespective of overall plant morphology or pollination system. These correlations between flower size, moisture availability, and delta(13)C suggest that water loss from flowers can influence leaf responses to the environment, which in turn may indirectly mediate an effect on flower size.
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Affiliation(s)
- Susan C Lambrecht
- Department of Biological Sciences and the Center for Biodiversity, San José State University, San Jose, CA 95192, USA.
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Bratteler M, Lexer C, Widmer A. Genetic architecture of traits associated with serpentine adaptation of Silene vulgaris. J Evol Biol 2006; 19:1149-56. [PMID: 16780515 DOI: 10.1111/j.1420-9101.2006.01090.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Serpentine soils provide a difficult substrate for plant colonization and growth and therefore represent an ideal system for studying the genetics of habitat adaptation and the evolution of plant-ecotypes. Using an F2 mapping population derived from an intraspecific cross between a serpentine and a nonserpentine ecotype of Silene vulgaris, the genetic architecture of seven morphological, physiological and life-history traits was explored. A quantitative trait locus (QTL) analysis identified 23 QTLs, 15 of which were classified as major QTLs. The observed genetic architecture suggests that traits potentially involved in habitat adaptation are controlled by few genes of major effect and have evolved under consistent directional selection. Several linkage groups harboured overlapping QTLs for different traits, which can be due to either pleiotropy or linkage. The potential roles of these factors and of the time available for habitat adaptation and ecological speciation on serpentine are discussed.
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Affiliation(s)
- M Bratteler
- ETH Zurich, Plant Ecological Genetics, Institute of Integrative Biology, 8092, Zurich, Switzerland
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Ashman TL, Majetic CJ. Genetic constraints on floral evolution: a review and evaluation of patterns. Heredity (Edinb) 2006; 96:343-52. [PMID: 16598191 DOI: 10.1038/sj.hdy.6800815] [Citation(s) in RCA: 159] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The characteristics of flowers influence most aspects of angiosperm reproduction, including the agents of pollination and patterns of mating. Thus, a clear view of the forces that mediate floral phenotypic evolution is central to understanding angiosperm diversity. Here, we inform on the capacity for floral phenotype to respond to selection by reviewing published data on heritabilities and genetic correlations for several classes of floral traits (primary sexual, attraction, mating system) in hermaphroditic plants. We find significant heritability for all floral traits but also variation among them, as well as a tendency for heritability to vary with mating system, but not life history. We additionally test predictions stemming from life history theory (eg, negative covariation between male-female traits and flower size-flower number), and ideas concerning the extent and pattern of genetic integration between flowers and leaves, and between the sexes of dioecious and gynodioecious species. We find mixed evidence for life history tradeoffs. We find strong support for floral integration and its relation with floral morphology (actinomorphy vs zygomorphy) and for a decoupling of floral and vegetative traits, but no evidence that modular integration varies with floral morphology. Lastly, we find mixed evidence for a relationship between the level of sexual dimorphism in attraction traits and the between-sex correlation in gender dimorphic plants.
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Affiliation(s)
- T-L Ashman
- 1Department of Biological Sciences, University of Pittsburgh, 4249 Fifth Ave and Ruskin, Pittsburgh, PA 15260, USA.
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Culley TM, Dunbar-Wallis AK, Sakai AK, Weller SG, Mishio M, Campbell DR, Herzenach M. Genetic variation of ecophysiological traits in two gynodioecious species of Schiedea (Caryophyllaceae). THE NEW PHYTOLOGIST 2006; 169:589-601. [PMID: 16411961 DOI: 10.1111/j.1469-8137.2005.01588.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Evolution of dimorphic breeding systems may involve changes in ecophysiological traits as well as floral morphology because of greater resource demands on females. Differences between related species suggest that ecophysiological traits should be heritable, and species with higher female frequencies should show greater sexual differentiation. We used modified partial diallel crossing designs to estimate narrow-sense heritabilities and genetic correlations of sex-specific ecophysiological and morphological traits in closely related gynodioecious Schiedea salicaria (13% females) and Schiedea adamantis (39% females). In S. salicaria, hermaphrodites and females differed in photosynthetic rate and specific leaf area (SLA). Narrow-sense heritabilities were significant for stomatal conductance, SLA and inflorescence number in hermaphrodites, and for SLA and inflorescence number in females. Schiedea adamantis had no sexual dimorphism in measured traits; stomatal conductance, stem number and inflorescence number were heritable in females, and stem number was heritable in hermaphrodites. In both species, significant genetic correlations of traits between sexes were rare, indicating that traits can evolve independently in response to sex-differential selection. Significant genetic correlations were detected between certain traits within sexes of both species. Low heritability of some ecophysiological traits may reflect low additive genetic variability or high phenotypic plasticity in these traits.
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Affiliation(s)
- Theresa M Culley
- Department of Ecology and Evolutionary Biology, University of California Irvine 92697, USA.
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Huang SQ, Tang LL, Sun JF, Lu Y. Pollinator response to female and male floral display in a monoecious species and its implications for the evolution of floral dimorphism. THE NEW PHYTOLOGIST 2006; 171:417-24. [PMID: 16866947 DOI: 10.1111/j.1469-8137.2006.01766.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Pollinator-mediated selection has been hypothesized as one cause of size dimorphism between female and male flowers. Flower number, ignored in studies of floral dimorphism, may interact with flower size to affect pollinator selectivity. In the present study, we explored pollinator response, and estimated pollen receipt and removal, in experimental populations of monoecious Sagittaria trifolia, in which plants were manipulated to display three, six, nine or 12 female or male flowers per plant. In this species, female flowers are smaller but have a more compressed flowering period than males, creating larger female floral displays. Overall, pollinators preferred to visit male rather than female displays of the same size. Both first visit per foraging bout and visitation rates to female displays increased with display size. However, large male displays did not show increased attractiveness to pollinators. A predicted relationship that pollen removal, rather than pollen receipt, is limited by pollinator visitation was confirmed in the experimental populations. The results suggest that the lack of selection on large male displays may affect the evolution of floral dimorphism in this species.
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Armbruster WS, Antonsen L, Pélabon C. PHENOTYPIC SELECTION ON DALECHAMPIA BLOSSOMS: HONEST SIGNALING AFFECTS POLLINATION SUCCESS. Ecology 2005. [DOI: 10.1890/04-1873] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Abstract
Protandry (when male function precedes female) can enhance fitness by reducing selfing and increasing pollen export and outcrossed siring success. However, responses to selection on protandry may be constrained by genetic variation and correlations among floral traits. We examined these potential constraints in protandrous Chamerion angustifolium (Onagraceae) by estimating genetic variation in male-phase duration and associated floral traits using a paternal half-sib design and selection experiment. Narrow-sense heritability of male-phase duration was estimated as 0.23 (SE +/- 0.04) and was positively correlated with floral display. The selection experiment shortened male-phase duration 0.8 SD from the parental average of 17.0 h and lengthened it by 2.0 SD. Furthermore, fixed floral longevity caused a negative association between male- and female-phase durations. These results suggest that selection on male-phase duration is not limited by genetic variation. However, changes in male-phase duration may influence pollinators through correlated changes in floral display and reduced opportunities for pollen receipt during female phase.
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Affiliation(s)
- M B Routley
- Department of Botany, University of Guelph, Guelph, ON, Canada.
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Caruso CM, Maherali H, Mikulyuk A, Carlson K, Jackson RB. GENETIC VARIANCE AND COVARIANCE FOR PHYSIOLOGICAL TRAITS IN LOBELIA: ARE THERE CONSTRAINTS ON ADAPTIVE EVOLUTION? Evolution 2005. [DOI: 10.1554/04-501] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Delph LF, Frey FM, Steven JC, Gehring JL. Investigating the independent evolution of the size of floral organs via G-matrix estimation and artificial selection. Evol Dev 2004; 6:438-48. [PMID: 15509226 DOI: 10.1111/j.1525-142x.2004.04052.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The attractiveness of a plant to pollinators is dependent on both the number of flowers produced and the size of the petals. However, limiting resources often result in a size/number trade-off, whereby the plant can make either more flowers or larger flowers, but not both. If developmental genes underlying sepal and petal identity (some of which overlap) also influence size, then this shared genetic basis could constrain the independent evolution of floral size and attractiveness. Here, we determined whether the size of sepals and petals in the dioecious perennial, Silene latifolia, are developmentally independent by performing two experiments: a genetic variance-covariance experiment to estimate genetic correlations between calyx width, petal-limb length, flower mass, and number and a four-bout artificial-selection experiment to alter calyx width and estimate the correlated response in petal-limb length. In addition, we determined whether variation in petal-limb length is the result of cell expansion or cell proliferation. The first experiment revealed that petal-limb length is not genetically correlated with calyx width, and the second experiment confirmed this; selection on calyx width did not result in a predictable or significant change in petal-limb length. Flower number was negatively correlated with all the floral traits measured, indicating a flower size/number trade-off. Cell number, but not size, explained a significant amount of the variation in petal-limb length. We conclude that the size of the two outer floral organs can evolve independently. This species can therefore increase the number of flowers produced by decreasing investment in the calyx without simultaneously decreasing petal size and the attractiveness of each individual flower to pollinators.
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Affiliation(s)
- Lynda F Delph
- Department of Biology, Indiana University, Bloomington, IN 47405, USA.
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Delph LF, Gehring JL, Frey FM, Arntz AM, Levri M. GENETIC CONSTRAINTS ON FLORAL EVOLUTION IN A SEXUALLY DIMORPHIC PLANT REVEALED BY ARTIFICIAL SELECTION. Evolution 2004. [DOI: 10.1554/03-645] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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