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Pretz C, Smith SD. Intraspecific breakdown of self-incompatibility in Physalis acutifolia (Solanaceae). AOB PLANTS 2022; 14:plab080. [PMID: 35079331 PMCID: PMC8783618 DOI: 10.1093/aobpla/plab080] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Accepted: 12/21/2021] [Indexed: 05/13/2023]
Abstract
Variation in mating systems is prevalent throughout angiosperms, with many transitions between outcrossing and selfing above and below the species level. This study documents a new case of an intraspecific breakdown of self-incompatibility in a wild relative of tomatillo, Physalis acutifolia. We used controlled greenhouse crosses to identify self-incompatible (SI) and self-compatible (SC) individuals grown from seed sampled across seven sites across Arizona and New Mexico. We measured 14 flower and fruit traits to test for trait variation associated with mating system. We also quantified pollen tube growth in vivo and tested for the presence of the S-RNase proteins in SI and SC styles. We found that seed from six of the seven sites produced SI individuals that terminated self-pollen tubes in the style and showed detectable S-RNase expression. By contrast, seed from one Arizona site produced SC individuals with no S-RNase expression. These SC individuals displayed typical selfing-syndrome traits such as smaller corollas, reduced stigma-anther distances, and a smaller pollen-ovule ratio. We also found plasticity in self-incompatibility as most of the SI individuals became SC and lost S-RNase expression roughly after 6 months in the greenhouse. While fixed differences in mating systems are known among the SI wild species and the often SC domesticated tomatillos, our study is the first to demonstrate intraspecific variation in natural populations as well as variation in SI over an individual's lifespan.
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Affiliation(s)
- Chelsea Pretz
- Department of Ecology and Evolutionary Biology, University of Colorado, 1900 Pleasant Street, Boulder, CO 80309, USA
- Corresponding author’s e-mail address:
| | - Stacey D Smith
- Department of Ecology and Evolutionary Biology, University of Colorado, 1900 Pleasant Street, Boulder, CO 80309, USA
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2
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Rifkin JL, Cao G, Rausher MD. Genetic architecture of divergence: the selfing syndrome in Ipomoea lacunosa. AMERICAN JOURNAL OF BOTANY 2021; 108:2038-2054. [PMID: 34648660 DOI: 10.1002/ajb2.1749] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2021] [Revised: 05/28/2021] [Accepted: 05/29/2021] [Indexed: 06/13/2023]
Abstract
PREMISE Highly selfing plant species frequently display a distinctive suite of traits termed the selfing syndrome. Here we tested the hypothesis that these traits are grouped into correlated evolutionary modules and determined the degree of independence between such modules. METHODS We evaluated phenotypic correlations and QTL overlaps in F2 offspring of a cross between the morning glories Ipomoea lacunosa and I. cordatotriloba and investigated how traits clustered into modules at both the phenotypic and genetic level. We then compared our findings to other QTL studies of the selfing syndrome. RESULTS In the I. lacunosa selfing syndrome, traits grouped into modules that displayed correlated evolution within but not between modules. QTL overlap predicted phenotypic correlations, and QTLs affecting the same trait module were significantly physically clustered in the genome. The genetic architecture of the selfing syndrome varied across systems, but the pattern of stronger within- than between-module correlation was widespread. CONCLUSIONS The genetic architecture we observe in the selfing syndrome is consistent with a growing understanding of floral morphological integration achieved via pleiotropy in clustered traits. This view of floral evolution is consistent with resource limitation or predation driving the evolution of the selfing syndrome, but invites further research into both the selective causes of the selfing syndrome and how genetic architecture itself evolves in response to changes in mating system.
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Affiliation(s)
- Joanna L Rifkin
- Department of Ecology and Evolutionary Biology, The University of Toronto, 25 Willcocks Street, Toronto, ON, M5S 3B2, Canada
| | - Gongyuan Cao
- Department of Biology, Duke University, 124 Science Drive, Durham, NC, 27701, USA
| | - Mark D Rausher
- Department of Biology, Duke University, 124 Science Drive, Durham, NC, 27701, USA
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Rose JP, Sytsma KJ. Complex interactions underlie the correlated evolution of floral traits and their association with pollinators in a clade with diverse pollination systems. Evolution 2021; 75:1431-1449. [PMID: 33818785 DOI: 10.1111/evo.14220] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 02/15/2021] [Accepted: 03/14/2021] [Indexed: 11/28/2022]
Abstract
Natural selection by pollinators is an important factor in the morphological diversity and adaptive radiation of flowering plants. Selection by similar pollinators in unrelated plants leads to convergence in floral morphology, or "floral syndromes." Previous investigations into floral syndromes have mostly studied relatively small and/or simple systems, emphasizing vertebrate pollination. Despite the importance of multiple floral traits in plant-pollinator interactions, these studies have examined few quantitative traits, so their co-variation and phenotypic integration have been underexplored. To gain better insights into pollinator-trait dynamics, we investigate the model system of the phlox family (Polemoniaceae), a clade of ∼400 species pollinated by a diversity of vectors. Using a comprehensive phylogeny and large dataset of traits and observations of pollinators, we reconstruct ancestral pollination system, accounting for the temporal history of pollinators. We conduct phylogenetically controlled analyses of trait co-variation and association with pollinators, integrating many analyses over phylogenetic uncertainty. Pollinator shifts are more heterogeneous than previously hypothesized. The evolution of floral traits is partially constrained by phylogenetic history and trait co-variation, but traits are convergent and differences are associated with different pollinators. Trait shifts are usually gradual, rather than rapid, suggesting complex genetic and ecological interactions of flowers at macroevolutionary scales.
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Affiliation(s)
- Jeffrey P Rose
- Department of Botany, University of Wisconsin-Madison, Madison, Wisconsin, 53706.,Current Address: Department of Biology, University of Nebraska at Kearney, Kearney, Nebraska, 68849
| | - Kenneth J Sytsma
- Department of Botany, University of Wisconsin-Madison, Madison, Wisconsin, 53706
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Sun Y, Bossdorf O, Grados RD, Liao Z, Müller-Schärer H. Rapid genomic and phenotypic change in response to climate warming in a widespread plant invader. GLOBAL CHANGE BIOLOGY 2020; 26:6511-6522. [PMID: 32702177 DOI: 10.1111/gcb.15291] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2020] [Accepted: 07/14/2020] [Indexed: 05/02/2023]
Abstract
Predicting plant distributions under climate change is constrained by our limited understanding of potential rapid adaptive evolution. In an experimental evolution study with the invasive common ragweed (Ambrosia artemisiifolia L.) we subjected replicated populations of the same initial genetic composition to simulated climate warming. Pooled DNA sequencing of parental and offspring populations showed that warming populations experienced greater genetic divergence from their parents, than control populations. In a common environment, offspring from warming populations showed more convergent phenotypes in seven out of nine plant traits, with later flowering and larger biomass, than plants from control populations. For both traits, we also found a significantly higher ratio of phenotypic to genetic differentiation across generations for warming than for control populations, indicating stronger response to selection under warming conditions. As a measure for evolutionary rate, the phenotypic and sequence divergence between generations were assessed using the Haldane metric. Our approach combining comparisons between generations (allochronic) and between treatments (synchronic) in an experimental evolutionary field study, and linking population genomic data with phenotyping analyses provided a powerful test to detect rapid responses to selection. Our findings demonstrate that ragweed populations can rapidly evolve in response to climate change within a single generation. Short-term evolutionary responses to climate change may aggravate the impact of some plant invaders in the future and should be considered when making predictions about future distributions and impacts of plant invaders.
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Affiliation(s)
- Yan Sun
- Plant Evolutionary Ecology, Institute of Evolution & Ecology, University of Tübingen, Tübingen, Germany
| | - Oliver Bossdorf
- Plant Evolutionary Ecology, Institute of Evolution & Ecology, University of Tübingen, Tübingen, Germany
| | - Ramon D Grados
- Plant Evolutionary Ecology, Institute of Evolution & Ecology, University of Tübingen, Tübingen, Germany
- Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain
| | - ZhiYong Liao
- Plant Evolutionary Ecology, Institute of Evolution & Ecology, University of Tübingen, Tübingen, Germany
- CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, China
| | - Heinz Müller-Schärer
- Department of Biology/Ecology & Evolution, University of Fribourg, Fribourg, Switzerland
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5
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Abstract
The angiosperm flower develops through a modular programme which, although ancient and conserved, provides the flexibility that has allowed an almost infinite variety of floral forms to emerge. In this review, we explore the evolution of floral diversity, focusing on our recent understanding of the mechanistic basis of evolutionary change. We discuss the various ways in which flower size and floral organ size can be modified, the means by which flower shape and symmetry can change, and the ways in which floral organ position can be varied. We conclude that many challenges remain before we fully understand the ecological and molecular processes that facilitate the diversification of flower structure.
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Emms SK, Hove AA, Dudley LS, Mazer SJ, Verhoeven AS. Could seasonally deteriorating environments favour the evolution of autogamous selfing and a drought escape physiology through indirect selection? A test of the time limitation hypothesis using artificial selection in Clarkia. ANNALS OF BOTANY 2018; 121:753-766. [PMID: 29351591 PMCID: PMC5853010 DOI: 10.1093/aob/mcx197] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Accepted: 12/08/2017] [Indexed: 05/25/2023]
Abstract
BACKGROUND AND AIMS The evolution of selfing from outcrossing may be the most common transition in plant reproductive systems and is associated with a variety of ecological circumstances and life history strategies. The most widely discussed explanation for these associations is the reproductive assurance hypothesis - the proposition that selfing is favoured because it increases female fitness when outcross pollen receipt is limited. Here an alternative explanation, the time limitation hypothesis, is addressed, one scenario of which proposes that selfing may evolve as a correlated response to selection for a faster life cycle in seasonally deteriorating environments. METHODS Artificial selection for faster maturation (early flowering) or for low herkogamy was performed on Clarkia unguiculata (Onagraceae), a largely outcrossing species whose closest relative, C. exilis, has evolved higher levels of autogamous selfing. Direct responses to selection and correlated evolutionary changes in these traits were measured under greenhouse conditions. Direct responses to selection on early flowering and correlated evolutionary changes in the node of the first flower, herkogamy, dichogamy, gas exchange rates and water use efficiency (WUE) were measured under field conditions. KEY RESULTS Lines selected for early flowering and for low herkogamy showed consistent, statistically significant responses to direct selection. However, there was little or no evidence of correlated evolutionary changes in flowering date, floral traits, gas exchange rates or WUE. CONCLUSIONS These results suggest that the maturation rate and mating system have evolved independently in Clarkia and that the time limitation hypothesis does not explain the repeated evolution of selfing in this genus, at least through its indirect selection scenario. They also suggest that the life history and physiological components of drought escape are not genetically correlated in Clarkia, and that differences in gas exchange physiology between C. unguiculata and C. exilis have evolved independently of differences in mating system and life history.
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Affiliation(s)
- Simon K Emms
- Department of Biology, University of St. Thomas, Saint Paul, MN, USA
| | - Alisa A Hove
- Department of Biology, Warren Wilson College, Asheville, NC, USA
| | - Leah S Dudley
- Department of Biology, University of Wisconsin-Stout, Menomonie, WI, USA
| | - Susan J Mazer
- Department of Ecology, Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, CA, USA
| | - Amy S Verhoeven
- Department of Biology, University of St. Thomas, Saint Paul, MN, USA
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Voillemot M, Rougemont Q, Roux C, Pannell JR. The divergence history of the perennial plant Linaria cavanillesii
confirms a recent loss of self-incompatibility. J Evol Biol 2017; 31:136-147. [DOI: 10.1111/jeb.13209] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2017] [Revised: 11/03/2017] [Accepted: 11/07/2017] [Indexed: 11/30/2022]
Affiliation(s)
- M. Voillemot
- Department of Ecology and Evolution; Biophore/Sorge; University of Lausanne; Lausanne Switzerland
| | - Q. Rougemont
- Institut de Biologie Intégrative et des Systèmes (IBIS); University of Laval; Québec City Québec Canada
| | - C. Roux
- Department of Ecology and Evolution; Biophore/Sorge; University of Lausanne; Lausanne Switzerland
- Unité Evo-Eco-Paléo (EEP) - UMR 8198; CNRS; Université de Lille Sciences et Technologies; Villeneuve d'Ascq Cedex France
| | - J. R. Pannell
- Department of Ecology and Evolution; Biophore/Sorge; University of Lausanne; Lausanne Switzerland
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8
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Kvalnes T, Ringsby TH, Jensen H, Hagen IJ, Rønning B, Pärn H, Holand H, Engen S, Saether BE. Reversal of response to artificial selection on body size in a wild passerine. Evolution 2017; 71:2062-2079. [DOI: 10.1111/evo.13277] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Accepted: 05/11/2017] [Indexed: 01/16/2023]
Affiliation(s)
- Thomas Kvalnes
- Centre for Biodiversity Dynamics (CBD), Department of Biology; Norwegian University of Science and Technology (NTNU); NO-7491 Trondheim Norway
| | - Thor Harald Ringsby
- Centre for Biodiversity Dynamics (CBD), Department of Biology; Norwegian University of Science and Technology (NTNU); NO-7491 Trondheim Norway
| | - Henrik Jensen
- Centre for Biodiversity Dynamics (CBD), Department of Biology; Norwegian University of Science and Technology (NTNU); NO-7491 Trondheim Norway
| | - Ingerid Julie Hagen
- Centre for Biodiversity Dynamics (CBD), Department of Biology; Norwegian University of Science and Technology (NTNU); NO-7491 Trondheim Norway
| | - Bernt Rønning
- Centre for Biodiversity Dynamics (CBD), Department of Biology; Norwegian University of Science and Technology (NTNU); NO-7491 Trondheim Norway
| | - Henrik Pärn
- Centre for Biodiversity Dynamics (CBD), Department of Biology; Norwegian University of Science and Technology (NTNU); NO-7491 Trondheim Norway
| | - Håkon Holand
- Centre for Biodiversity Dynamics (CBD), Department of Biology; Norwegian University of Science and Technology (NTNU); NO-7491 Trondheim Norway
| | - Steinar Engen
- Centre for Biodiversity Dynamics (CBD); Department of Mathematical Sciences, Norwegian University of Science and Technology (NTNU); NO-7491 Trondheim Norway
| | - Bernt-Erik Saether
- Centre for Biodiversity Dynamics (CBD), Department of Biology; Norwegian University of Science and Technology (NTNU); NO-7491 Trondheim Norway
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Voillemot M, Pannell JR. Maintenance of mixed mating after the loss of self-incompatibility in a long-lived perennial herb. ANNALS OF BOTANY 2017; 119:177-190. [PMID: 27941096 PMCID: PMC5218368 DOI: 10.1093/aob/mcw203] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Revised: 06/23/2016] [Accepted: 07/19/2016] [Indexed: 05/09/2023]
Abstract
BACKGROUND AND AIMS Many hermaphroditic plants avoid self-fertilization by means of a molecular self-incompatibility (SI) system, a complex trait that is difficult to evolve but relatively easy to lose. Loss of SI is a prerequisite for an evolutionary transition from obligate outcrossing to self-fertilization, which may bring about rapid changes in the genetic diversity and structure of populations. Loss of SI is also often followed by the evolution of a 'selfing syndrome', with plants having small flowers, little nectar and few pollen grains per ovule. Here, we document the loss of SI in the long-lived Spanish toadflax Linaria cavanillesii, which has led to mixed mating rather than a transition to a high rate of selfing and in which an outcrossing syndrome has been maintained. METHODS We performed crosses within and among six populations of L. cavanillesii in the glasshouse, measured floral traits in a common-garden experiment, performed a pollen-limitation experiment in the field and conducted population genetic analyses using microsatellites markers. KEY RESULTS Controlled crosses revealed variation in SI from fully SI through intermediate SI to fully self-compatible (SC). Flowers of SC individuals showed no evidence of a selfing syndrome. Although the SC population of L. cavanillesii had lower within-population genetic diversity than SI populations, as expected, population differentiation among all populations was extreme and represents an FST outlier in the distribution for both selfing and outcrossing species of flowering plants. CONCLUSIONS Together, our results suggest that the transition to SC in L. cavanillesii has probably been very recent, and may have been aided by selection during or following a colonization bottleneck rather than in the absence of pollinators. We find little indication that the transition to SC has been driven by selection for reproductive assurance under conditions currently prevailing in natural populations.
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Affiliation(s)
- Marie Voillemot
- Department of Ecology and Evolution, Biophore Building, University of Lausanne, CH-1015 Lausanne, Switzerland
| | - John R Pannell
- Department of Ecology and Evolution, Biophore Building, University of Lausanne, CH-1015 Lausanne, Switzerland
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10
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Herkogamy and its effects on mating patterns in Arabidopsis thaliana. PLoS One 2013; 8:e57902. [PMID: 23469099 PMCID: PMC3582510 DOI: 10.1371/journal.pone.0057902] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2012] [Accepted: 01/28/2013] [Indexed: 12/26/2022] Open
Abstract
The evolution of mating systems, which exhibit an extraordinary diversity in flowering plants, is of central interest in plant biology. Herkogamy, the spatial separation of sexual organs within flowers, is a widespread floral mechanism that is thought to be an adaptive trait reducing self-pollination in hermaphroditic plants. In contrast with previous studies of herkogamy that focused on plants with relatively large floral displays, we here characterized herkogamy in Arabidopsis thaliana, a model plant with a strong selfing syndrome. Developmental features, reproductive consequences, and genetic architecture of herkogamy were exploited using naturally variable A. thaliana accessions, under both greenhouse and natural conditions. Our results demonstrate that the degree of herkogamy can strongly influence the mating patterns of A. thaliana: approach herkogamy can effectively promote outcrossing, no herkogamy is also capable of enhancing the opportunity for outcrossing, and reverse herkogamy facilitates efficient self-pollination. In addition, we found that the expression of herkogamy in A. thaliana was environment-dependent and regulated by multiple quantitative trait loci. This study reveals how minor modifications in floral morphology may cause dramatic changes in plant mating patterns, provides new insights into the function of herkogamy, and suggests the way for dissecting the genetic basis of this important character in a model plant.
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11
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Andersson S. Does inbreeding promote evolutionary reduction of flower size? Experimental evidence from Crepis tectorum (Asteraceae). AMERICAN JOURNAL OF BOTANY 2012; 99:1388-1398. [PMID: 22859658 DOI: 10.3732/ajb.1200116] [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 Small, autogamous flowers have evolved repeatedly in the plant kingdom. While much attention has focused on the mechanisms that promote the shift to autogamy, there is still a paucity of information on the factors that underlie the reduction of flower size so prevalent in selfing lineages. In this study of Crepis tectorum, I examine the role of inbreeding, acting alone or together with selection, in promoting evolutionary reduction of flower size. METHODS Experimental crosses were performed to produce progeny populations that differed in inbreeding and (or) selection history. Progenies were grown in two different environments and scored for flower size and other characters. KEY RESULTS Inbreeding depressed flower and fruit size, but also caused changes in flowering time and the number of heads produced. Despite some inconsistencies in the results for the last progeny generation, the decline in flower size was persistent over generations, consistent across environments, and similar in magnitude to the effects of selection for small flower size and the floral reduction inferred to have taken place during the shift toward autogamy within the study species. The floral size reduction was largely independent of changes in overall vigor, and there was considerable adaptive potential in flower size (measured by sib analyses and parent-offspring comparisons) after inbreeding. CONCLUSIONS The results of this study indicate that inbreeding can promote evolutionary reduction of flower size and highlight the close, persistent association between flower and fruit size in the study species.
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12
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Baker JA, Heins DC, King RW, Foster SA. Rapid shifts in multiple life history traits in a population of threespine stickleback. J Evol Biol 2011; 24:863-70. [PMID: 21276108 DOI: 10.1111/j.1420-9101.2010.02217.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Measurement of the rate of phenotypic or genetic change provides data bearing on many questions of fundamental interest to biologists, including how fast changes can proceed, whether shifts occur gradually or in bursts and how long high rates of change can be sustained. Because traits exist in functionally and genetically correlated suites, studies tracking many traits are likely to be the most informative. We quantify very rapid phenotypic changes in egg size (now smaller), clutch size (larger) and the age/size of both breeding females and males (younger, smaller) in an Alaskan population, with these traits shifting at rates from 0.13 to 0.30 haldanes over a 10-year period. In contrast, female reproductive effort and the allometric relationship of clutch size to body size changed little. These shifts appear to be caused by an altered selective landscape, with the presumed selective agent being increasing lake productivity. Some of the traits undoubtedly have at heritable component and thus represent genetic evolution as well as phenotypic.
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Affiliation(s)
- J A Baker
- Department of Biology, Lasry Center for BioScience, Clark University, Worcester, MA 01610, USA.
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13
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Mojica JP, Kelly JK. Viability selection prior to trait expression is an essential component of natural selection. Proc Biol Sci 2010; 277:2945-50. [PMID: 20462906 PMCID: PMC2982025 DOI: 10.1098/rspb.2010.0568] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2010] [Accepted: 04/20/2010] [Indexed: 11/12/2022] Open
Abstract
Natural selection operates throughout the life cycle of an organism. Correlative studies typically fail to consider the effects of viability selection prior to trait expression. A 3-year field experiment on the wildflower Mimulus guttatus demonstrates that this unmeasured component of selection can be very strong. As in previous studies, we find that fecundity is positively related to flower size. However, survival to flowering is much lower in large-flowered genotypes than in small-flowered genotypes. Aggregating viability and fecundity, lifetime fitness through female function generally favoured smaller flowered genotypes. This result differs from the great majority of field studies, which suggest strong positive selection on flower size. It has important cautionary implications for studies of natural and sexual selection on adult characters generally, in both plants and animals.
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Affiliation(s)
| | - John K. Kelly
- Department of Ecology and Evolutionary Biology, University of Kansas, 1200 Sunnyside Avenue, Lawrence, KS 66045, USA
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15
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Barkman TJ, Bendiksby M, Lim SH, Salleh KM, Nais J, Madulid D, Schumacher T. Accelerated rates of floral evolution at the upper size limit for flowers. Curr Biol 2008; 18:1508-13. [PMID: 18848446 DOI: 10.1016/j.cub.2008.08.046] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2008] [Revised: 08/11/2008] [Accepted: 08/12/2008] [Indexed: 10/21/2022]
Abstract
Evolutionary theory explains phenotypic change as the result of natural selection, with constraint limiting the direction, magnitude, and rate of response [1]. Constraint is particularly likely to govern evolutionary change when a trait is at perceived upper or lower limits. Macroevolutionary rates of floral-size change are unknown for any angiosperm family, but it is predicted that rates should be diminished near the upper size limit of flowers, as has been shown for mammal body mass [2]. Our molecular results show that rates of floral-size evolution have been extremely rapid in the endoholoparasite Rafflesia, which contains the world's largest flowers [3]. These data provide the first estimates of macroevolutionary rates of floral-size change and indicate that in this lineage, floral diameter increased by an average of 20 cm (and up to 90 cm)/million years. In contrast to our expectations, it appears that the magnitude and rate of floral-size increase is greater for lineages with larger flowered ancestors. This study suggests that constraints on rates of floral-size evolution may not be limiting in Rafflesia, reinforcing results of artificial- and natural-selection studies in other plants that demonstrated the potential for rapid size changes [4-6].
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Affiliation(s)
- Todd J Barkman
- Department of Biological Sciences, Western Michigan University, Kalamazoo, Michigan 49008, USA.
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Herlihy CR, Eckert CG. Evolutionary analysis of a key floral trait in aquilegia canadensis (ranunculaceae): genetic variation in herkogamy and its effect on the mating system. Evolution 2007; 61:1661-74. [PMID: 17598747 DOI: 10.1111/j.1558-5646.2007.00137.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The mating system of flowering plant populations evolves through selection on genetically based phenotypic variation in floral traits. The physical separation of anthers and stigmas within flowers (herkogamy) is expected to be an important target of selection to limit self-fertilization. We investigated the pattern of phenotypic and genetic variation in herkogamy and its effect of self-fertilization in a broad sample of natural populations of Aquilegia canadensis, a species that is highly selfing despite strong inbreeding depression. Within natural populations, plants exhibit substantial phenotypic variation in herkogamy caused primarily by variation in pistil length rather than stamen length. Compared to other floral traits, herkogamy is much more variable and a greater proportion of variation is distributed among rather than within individuals. We tested for a genetic component of this marked phenotypic variation by growing naturally pollinated seed families from five populations in a common greenhouse environment. For three populations, we detected a significant variation in herkogamy among families, and a positive regression between parental herkogamy measured in the field and progeny herkogamy in the greenhouse, suggesting that there is often genetic variation in herkogamy within natural populations. We estimated levels of self-fertilization for groups of flowers that differed in herkogamy and show that, as expected, herkogamy was associated with reduced selfing in 13 of 19 populations. In six of these populations, we performed floral emasculations to show that this decrease in selfing is due to decreased autogamy (within-flower selfing), the mode of selfing that herkogamy should most directly influence. Taken together, these results suggest that increased herkogamy should be selected to reduce the production of low-quality selfed seed. The combination of high selfing and substantial genetic variation for herkogamy in A. canadensis is enigmatic, and reconciling this observation will require a more integrated analysis of how herkogamy influences not only self-fertilization, but also patterns of outcross pollen import and export.
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Lehtilä K, Holmén Bränn K. Correlated effects of selection for flower size in Raphanus raphanistrum. ACTA ACUST UNITED AC 2007. [DOI: 10.1139/b07-007] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The evolution of flower size may be constrained by trade-offs between flower size and other plant traits. The aim of this study was to determine how selection on flower size affects both reproductive and vegetative traits. Raphanus raphanistrum L. was used as the study species. Artificial selection for small and large petal size was carried out for two generations. We measured the realized heritability of flower size and recorded flower production, time to flowering, plant size, and seed production in the two selection lines. The realized heritability was h2 = 0.49. Our study, therefore, showed that R. raphanistrum has potential for rapid evolutionary change of floral size. The lines with large flowers produced smaller seeds and started to flower later than the lines with small flowers. There was no trade-off between flower size and flower number, but the lines selected for large flower size had more flowers and a larger plant size than lines selected for small flowers. Estimates of restricted maximum likelihood (REML) analysis of pedigrees also showed that flower size had a positive genetic correlation with start of flowering and plant height.
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Affiliation(s)
- Kari Lehtilä
- School of Life Sciences, Södertörn University College, SE-14189 Huddinge, Sweden
- Department of Botany, Stockholm University, SE-10691 Stockholm, Sweden
| | - Kristina Holmén Bränn
- School of Life Sciences, Södertörn University College, SE-14189 Huddinge, Sweden
- Department of Botany, Stockholm University, SE-10691 Stockholm, Sweden
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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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Strakosh SC, Ferguson CJ. POLLINATION BIOLOGY OF FOUR SOUTHWESTERN SPECIES OF PHLOX (POLEMONIACEAE): INSECT VISITATION IN RELATION TO COROLLA TUBE LENGTH. SOUTHWEST NAT 2005. [DOI: 10.1894/0038-4909(2005)050[0291:pbofss]2.0.co;2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Medrano M, Herrera CM, Barrett SCH. Herkogamy and mating patterns in the self-compatible daffodil Narcissus longispathus. ANNALS OF BOTANY 2005; 95:1105-11. [PMID: 15797899 PMCID: PMC4246901 DOI: 10.1093/aob/mci129] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
BACKGROUND AND AIMS Floral design in self-compatible plants can influence mating patterns. This study investigated Narcissus longispathus, a self-compatible bee-pollinated species with wide variation in anther-stigma separation (herkogamy), to determine the relationship between variation in this floral trait and the relative amounts of cross- and self-fertilization. METHODS Anther-stigma separation was measured in the field in six populations of N. longispathus from south-eastern Spain. Variation in herkogamy during the life of individual flowers was also quantified. Multilocus outcrossing rates were estimated from plants differing in herkogamy using allozyme markers. KEY RESULTS Anther-stigma separation varied considerably among flowers within the six populations studied (range = 1-10 mm). This variation was nearly one order of magnitude larger than the slight, statistically non-significant developmental variation during the lifespan of individual flowers. Estimates of multilocus outcrossing rate for different herkogamy classes (t(m) range = 0.49-0.76) failed to reveal a monotonic increase with increasing herkogamy. CONCLUSIONS It is suggested that the lack of a positive relationship between herkogamy and outcrossing rate, a result that has not been previously documented for other species, could be mostly related to details of the foraging behaviour of pollinators.
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Affiliation(s)
- Mónica Medrano
- Estación Biológica de Doñana, Consejo Superior de Investigaciones Científicas, E-41013 Sevilla, Spain.
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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; 58:1936-46. [PMID: 15521453 DOI: 10.1111/j.0014-3820.2004.tb00481.x] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Sexual dimorphism is one of the most widespread and recognizable patterns of phenotypic variation in the biotic world. Sexual dimorphism in floral display is striking in the dioecious plant Silene latifolia, with males making many, small flowers compared to females. We investigated this dimorphism via artificial selection on two populations to determine whether genetic variation exists within populations for flower size and the extent of the between-sex correlation, whether a flower size and number trade-off exists within each sex, and whether pollen and ovule production vary with flower size. We selected for decreased flower size (calyx width) in females and increased flower size in males and measured the response to selection in size and correlated responses in flower dry mass, flower number, and pollen or ovule number per flower. Four bouts of selection in each of two selection programs were performed, for a total of three selection lines to decrease size, three to increase it, and two control lines. Flower size always significantly responded to selection and we always found a significant correlated response in the sex not under selection. Selection decreased but did not eliminate the sexual dimorphism in flower dry mass and number. A negative relationship between flower size and number within each sex was revealed. Whereas ovule number showed a significant correlated response to selection on flower size, pollen number did not. Our results indicate that although substantial additive genetic variation for flower size exists, the high between-sex genetic correlation would likely constrain flower size from becoming more sexually dimorphic. Furthermore, floral display within each sex is constrained by a flower size and number trade-off. Given this trade-off and lack of variation in pollen production with flower size, we suggest that sexual dimorphism evolved via sexual selection to increase flower number in males but not females.
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Affiliation(s)
- Lynda F Delph
- Department of Biology, Jordan Hall, 1001 East Third Street, Indiana University, Bloomington, Indiana 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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