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Rehman AU, Iso-Touru T, Junkers J, Rantanen M, Karhu S, Fischer D, Alsheikh M, Hjeltnes SH, Mezzetti B, Davik J, Schulman AH, Hytönen T, Haikonen T. Multi-model GWAS reveals key loci for horticultural traits in reconstructed garden strawberry. PHYSIOLOGIA PLANTARUM 2024; 176:e14440. [PMID: 39030778 DOI: 10.1111/ppl.14440] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2024] [Revised: 06/08/2024] [Accepted: 06/10/2024] [Indexed: 07/22/2024]
Abstract
The cultivated garden strawberry (Fragaria × ananassa) has a rich history, originating from the hybridization of two wild octoploid strawberry species in the 18th century. Two-step reconstruction of Fragaria × ananassa through controlled crossings between pre-improved selections of its parental species is a promising approach for enriching the breeding germplasm of strawberry for wider adaptability. We created a population of reconstructed strawberry by hybridizing elite selections of F. virginiana and F. chiloensis. A replicated field experiment was conducted to evaluate the population's performance for eleven horticulturally important traits, over multiple years. Population structure analyses based on Fana-50 k SNP array data confirmed pedigree-based grouping of the progenies into four distinct groups. As complex traits are often influenced by environmental variables, and population structure can lead to spurious associations, we tested multiple genome-wide association study (GWAS) models. GWAS uncovered 39 quantitative trait loci (QTL) regions for eight traits distributed across twenty chromosomes, including 11 consistent and 28 putative QTLs. Candidate genes for traits including winter survival, flowering time, runnering vigor, and hermaphrodism were identified within the QTL regions. To our knowledge, this study marks the first comprehensive investigation of adaptive and horticultural traits in a large, multi-familial reconstructed strawberry population using SNP markers.
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Affiliation(s)
- Attiq Ur Rehman
- Natural Resources Institute Finland (Luke), Finland
- Doctoral Program in Plant Sciences, University of Helsinki, Finland
| | | | - Jakob Junkers
- Norwegian Institute of Bioeconomy Research, Ås, Norway
| | | | - Saila Karhu
- Natural Resources Institute Finland (Luke), Finland
| | | | - Muath Alsheikh
- Graminor AS, Norway
- Faculty of Life Sciences, Department of Plant Sciences, Norwegian University of Life Sciences, Ås, Norway
| | | | - Bruno Mezzetti
- Department of Agriculture, Food and Environmental Sciences, Università Politecnica delle Marche, Ancona, Italy
| | - Jahn Davik
- Norwegian Institute of Bioeconomy Research, Ås, Norway
| | - Alan H Schulman
- Natural Resources Institute Finland (Luke), Finland
- Viikki Plant Science Centre, Finland
- Institute of Biotechnology, University of Helsinki, Finland
| | - Timo Hytönen
- Viikki Plant Science Centre, Finland
- Department of Agricultural Sciences, University of Helsinki, Finland
| | - Tuuli Haikonen
- Natural Resources Institute Finland (Luke), Finland
- Viikki Plant Science Centre, Finland
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2
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Qiao Q, Cao Q, Zhang R, Wu M, Zheng Y, Xue L, Lei J, Sun H, Liston A, Zhang T. Genomic analyses provide insights into sex differentiation of tetraploid strawberry (Fragaria moupinensis). PLANT BIOTECHNOLOGY JOURNAL 2024; 22:1552-1565. [PMID: 38184782 PMCID: PMC11123429 DOI: 10.1111/pbi.14286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Revised: 12/20/2023] [Accepted: 12/22/2023] [Indexed: 01/08/2024]
Abstract
The strawberry genus, Fragaria, exhibits a wide range of sexual systems and natural ploidy variation. Nearly, all polyploid strawberry species exhibit separate sexes (dioecy). Research has identified the sex-determining sequences as roughly conserved but with repeatedly changed genomic locations across octoploid strawberries. However, it remains unclear whether tetraploid wild strawberries evolved dioecy independently or shared a common origin with octoploid strawberries. In this study, we investigated the sex determinants of F. moupinensis, a dioecious plant with heterogametic females (ZW). Utilizing a combination of haplotype-resolved genome sequencing of the female F. moupinensis, k-mer-based and coverage-based genome-wide association studies (GWAS), and transcriptomic analysis, we discovered a non-recombining, approximately 33.6 kb W-specific region on chromosome 2a. Within this region, only one candidate sex-determining gene (FmoAFT) was identified. Furthermore, an extensive resequencing of the entire Fragaria genus indicated that the W-specific region displays conservative female specificity across all tetraploid species. This observation suggests that dioecy evolved independently in tetraploid and octoploid strawberries. Moreover, employing virus-induced gene silencing (VIGS), we knocked down the expression of the FmoAFT homologue transcript in cultivated strawberries, revealing its potential role in promoting female functions during early carpel development. We also applied DNA affinity purification sequencing (DAP-seq) and yeast one-hybrid assays to identify potential direct targets of FmoAFT. These insights shed new light on the genetic basis and evolutionary history of sex determination in strawberries, thereby facilitating the formulation of strategies to manipulate sex determination in breeding programs.
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Affiliation(s)
- Qin Qiao
- College of Horticulture and LandscapeYunnan Agricultural UniversityKunmingChina
| | - Qiang Cao
- College of Horticulture and LandscapeYunnan Agricultural UniversityKunmingChina
| | - Rengang Zhang
- Key Laboratory for Plant Diversity and Biogeography of East AsiaKunming Institute of Botany, Chinese Academy of SciencesKunmingChina
| | - Mingzhao Wu
- School of AgricultureYunnan UniversityKunmingChina
| | | | - Li Xue
- College of HorticultureShenyang Agricultural UniversityShenyangChina
| | - Jiajun Lei
- College of HorticultureShenyang Agricultural UniversityShenyangChina
| | - Hang Sun
- Key Laboratory for Plant Diversity and Biogeography of East AsiaKunming Institute of Botany, Chinese Academy of SciencesKunmingChina
| | - Aaron Liston
- Department of Botany and Plant PathologyOregon State UniversityCorvallisOregonUSA
| | - Ticao Zhang
- Key Laboratory for Plant Diversity and Biogeography of East AsiaKunming Institute of Botany, Chinese Academy of SciencesKunmingChina
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3
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Masaka K, Takada T. Transition model for the hermaphroditism-dioecy continuum in higher plants. Ecol Modell 2023. [DOI: 10.1016/j.ecolmodel.2022.110135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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4
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Baskin JM, Baskin CC. Seed germination of gynodioecious species: theoretical considerations and a comparison of females and hermaphrodites. PLANTA 2020; 252:73. [PMID: 33025176 DOI: 10.1007/s00425-020-03472-5] [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: 06/20/2020] [Accepted: 09/15/2020] [Indexed: 06/11/2023]
Abstract
Better seed germination of females than of hermaphrodites is not a major contributor to the greater geometric lifetime fitness that females require to be maintained in a gynodioecious population. Gynodioecy is a sexually dimorphic breeding system in which females (F, male sterile) and hermaphrodites (H) coexist in the same population. For plants with nuclear (biparental) inheritance of male sterility, theory predicts that except when the product of selfing rate (s) and inbreeding depression (δ) in H is high (sδ > 0.50), F must compensate (female advantage) for the loss of gene transmission via pollen production by producing more or higher-quality offspring than H to be maintained in the population. For species with cytoplasmic (maternal) inheritance of male sterility, the female requires only a small compensation in seed production or some other offspring fitness trait to persist. Reallocation to seeds of resources saved by loss of pollen production is expected to increase the quantity (number) and/or quality (mass, germinability) of seeds produced by F, thus compensating for the lack of pollen production. The primary aim of our study was to compare seed germination of F and H via a literature review. Based on theoretical considerations, we hypothesized that seeds of F should germinate better or equally as well as those of H. We found that of 235 case studies for 47 species Fgerm > Hgerm in 48.1%, Fgerm = Hgerm in 38.3% and Fgerm < Hgerm in 13.6%. Our results are very similar to those of a previously published meta-analysis that included germination of F and H for 12 species. For 162 cases on seed size, F > H in 29.0%, F = H in 63.6% and F < H in 7.4%. Since [(Fgerm > Hgerm) < (Fgerm ≤ Hgerm)] and [(Fseedsize > Hseedsize) < (Fseedsize ≤ Hseedsize)], these results suggest that seed quality is not a major fitness component of female advantage.
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Affiliation(s)
- Jerry M Baskin
- Department of Biology, University of Kentucky, Lexington, KY, 40506-0225, USA
| | - Carol C Baskin
- Department of Biology, University of Kentucky, Lexington, KY, 40506-0225, USA.
- Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY, 40546-0312, USA.
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5
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Varga S, Soulsbury CD. Environmental stressors affect sex ratios in sexually dimorphic plant sexual systems. PLANT BIOLOGY (STUTTGART, GERMANY) 2020; 22:890-898. [PMID: 32333831 DOI: 10.1111/plb.13125] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Accepted: 03/29/2020] [Indexed: 06/11/2023]
Abstract
Revealing the environmental pressures determining the frequency of females amongst populations of sexually dimorphic plants is a key research question. Analyses of sex ratio variation have been mainly done in dioecious plants, which misses key plant sexual systems that might represent intermediate stages in the evolution of dioecy from hermaphroditism. We investigated female frequency across populations of sexually dimorphic plant species in relation to environmental stressors (temperature, precipitation), totaling 342 species, 2011 populations, representing 40 orders and three different sexual systems (dioecy, gynodioecy and subdioecy). We also included the biome where the population was located to test how female frequency may vary more broadly with climate conditions. After correcting for phylogeny, our results for gynodioecious systems showed a positive relationship between female frequency and increased environmental stress, with the main effects being temperature-related. Subdioecious systems also showed strong positive relationships with temperature, and positive and negative relationships related to precipitation, while no significant effects on sex ratio in dioecious plants were detected. Combined, we show that female frequencies in an intermediate sexual system on the pathway from hermaphroditism to dioecy respond strongly to environmental stressors and have different selective agents driving female frequency.
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Affiliation(s)
- S Varga
- School of Life Sciences, University of Lincoln, Joseph Banks Laboratories, Lincoln, LN6 7TS, UK
| | - C D Soulsbury
- School of Life Sciences, University of Lincoln, Joseph Banks Laboratories, Lincoln, LN6 7TS, UK
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Penagos Zuluaga JC, Queenborough SA, Comita LS. Flowering sex ratios and costs of reproduction in gynodioecious Ocotea oblonga (Lauraceae). Biol J Linn Soc Lond 2020. [DOI: 10.1093/biolinnean/blaa117] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Abstract
In gynodioecious plant species, both female and hermaphrodite individuals produce fruit, but only hermaphrodites produce pollen. Such sex-specific differences in reproductive investment may contribute to dimorphism, but the magnitude and ecological effects are still unclear, especially for gynodioecious tropical trees where collecting flowers and determining the sex is complex. We documented flowering and fruiting over three years in a natural population of Ocotea oblonga (Lauraceae) trees in a tropical moist forest, Panama. We determined sex from freshly collected flowers, counted and measured fruit, and used long-term growth data for each individual. We confirmed that O. oblonga is gynodioecious. No tree switched sex or had flowers of both sexes. The population was hermaphrodite-biased. We found no ecological differences in reproductive investment (seed, fruit, or tree size, or growth rate) between the sexes, indicating that the sex differential in the cost of reproduction is much smaller in woody gynodioecious taxa than in dioecious taxa. Females produced more fruit than hermaphrodites, which may contribute to their persistence in the population. Accordingly, and contrary to most studies of temperate gynodioecious populations, our study of a tropical tree shows no differential cost of reproduction in a hermaphrodite-biased population. Consequently, other factors such as seed fertility or herbivory could drive the biased sex ratio in this population.
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Affiliation(s)
| | - Simon A Queenborough
- School of Forestry and Environmental Studies, Yale University, New Haven, CT, USA
| | - Liza S Comita
- School of Forestry and Environmental Studies, Yale University, New Haven, CT, USA
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Roux C, Pannell JR. The opposing effects of genetic drift and Haldane's sieve on floral-morph frequencies in tristylous metapopulations. THE NEW PHYTOLOGIST 2019; 224:1229-1240. [PMID: 31505031 PMCID: PMC6856859 DOI: 10.1111/nph.16187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Accepted: 08/01/2019] [Indexed: 06/10/2023]
Abstract
Tristyly is a genetic floral polymorphism in which three floral morphs are maintained at equal frequencies by negative frequency-dependent selection on alleles at two interacting loci. Because dominant alleles at these loci are maintained at a lower frequency than their recessive counterparts, they are more likely to be lost by founder events and genetic drift. Here we examine the hypothesis that dominant alleles under negative frequency-dependent selection should also be more likely to re-invade populations than recessive alleles, due to Haldane's Sieve, because recessive alleles not expressed in a heterozygote state cannot benefit from positive selection when rare. We used computer simulations of tristylous metapopulations to verify that Haldane's Sieve acting on migrants into occupied demes can indeed reverse the bias in allele frequencies expected for small single tristylous populations, particularly in situations of rapid population growth following colonisation. This effect is manifest both locally and at the metapopulation level. Our study illustrates the potential effect of Haldane's Sieve in the novel context of an iconic plant sexual-system polymorphism under the influence of metapopulation dynamics.
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Affiliation(s)
- Camille Roux
- CNRSUMR 8198 – Evo‐Eco‐PaleoUniv. LilleLilleF‐59000France
| | - John R. Pannell
- Department of Ecology and EvolutionUniversity of LausanneLausanne1015Switzerland
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8
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Hobza R, Hudzieczek V, Kubat Z, Cegan R, Vyskot B, Kejnovsky E, Janousek B. Sex and the flower - developmental aspects of sex chromosome evolution. ANNALS OF BOTANY 2018; 122:1085-1101. [PMID: 30032185 PMCID: PMC6324748 DOI: 10.1093/aob/mcy130] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Accepted: 07/13/2018] [Indexed: 05/07/2023]
Abstract
Background The evolution of dioecious plants is occasionally accompanied by the establishment of sex chromosomes: both XY and ZW systems have been found in plants. Structural studies of sex chromosomes are now being followed up by functional studies that are gradually shedding light on the specific genetic and epigenetic processes that shape the development of separate sexes in plants. Scope This review describes sex determination diversity in plants and the genetic background of dioecy, summarizes recent progress in the investigation of both classical and emerging model dioecious plants and discusses novel findings. The advantages of interspecies hybrids in studies focused on sex determination and the role of epigenetic processes in sexual development are also overviewed. Conclusions We integrate the genic, genomic and epigenetic levels of sex determination and stress the impact of sex chromosome evolution on structural and functional aspects of plant sexual development. We also discuss the impact of dioecy and sex chromosomes on genome structure and expression.
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Affiliation(s)
- Roman Hobza
- Department of Plant Developmental Genetics, Institute of Biophysics of the Czech Academy of Sciences, Kralovopolska, Brno, Czech Republic
| | - Vojtech Hudzieczek
- Department of Plant Developmental Genetics, Institute of Biophysics of the Czech Academy of Sciences, Kralovopolska, Brno, Czech Republic
| | - Zdenek Kubat
- Department of Plant Developmental Genetics, Institute of Biophysics of the Czech Academy of Sciences, Kralovopolska, Brno, Czech Republic
| | - Radim Cegan
- Department of Plant Developmental Genetics, Institute of Biophysics of the Czech Academy of Sciences, Kralovopolska, Brno, Czech Republic
| | - Boris Vyskot
- Department of Plant Developmental Genetics, Institute of Biophysics of the Czech Academy of Sciences, Kralovopolska, Brno, Czech Republic
| | - Eduard Kejnovsky
- Department of Plant Developmental Genetics, Institute of Biophysics of the Czech Academy of Sciences, Kralovopolska, Brno, Czech Republic
| | - Bohuslav Janousek
- Department of Plant Developmental Genetics, Institute of Biophysics of the Czech Academy of Sciences, Kralovopolska, Brno, Czech Republic
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9
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Bruns EL, Miller I, Hood ME, Carasso V, Antonovics J. The role of infectious disease in the evolution of females: Evidence from anther-smut disease on a gynodioecious alpine carnation. Evolution 2018; 73:497-510. [PMID: 30411338 DOI: 10.1111/evo.13640] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Revised: 10/17/2018] [Accepted: 11/01/2018] [Indexed: 12/01/2022]
Abstract
In flowering plants, the evolution of females is widely hypothesized to be the first step in the evolutionary pathway to separate male and female sexes, or dioecy. Natural enemies have the potential to drive this evolution if they preferentially attack hermaphrodites over females. We studied sex-based differences in exposure to anther-smut (Microbotryum), a sterilizing pollinator-transmitted disease, in Dianthus pavonius, a gynodioecious perennial herb. We found that within a heavily diseased population, females consistently had lower levels of Microbotryum spore deposition relative to hermaphrodites and that this difference was driven by rapid floral closing in females following successful pollination. We further show that this protective closing behavior is frequency dependent; females close faster when they are rare. These results indicate that anther-smut disease is an important source of selection for females, especially since we found in a common garden experiment no evidence that females have any inherent fecundity advantages over hermaphrodites. Finally, we show that among populations, those where anther-smut is present have a significantly higher frequency of females than those where the disease is absent. Taken together our results indicate that anther-smut disease is likely an important biotic factor driving the evolution and maintenance of females in this gynodioecious species.
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Affiliation(s)
- Emily L Bruns
- Department of Biology, University of Virginia, Charlottesville, Virginia, 22904
| | - Ian Miller
- Department of Biology, University of Virginia, Charlottesville, Virginia, 22904.,Current Address: Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey, 08544
| | - Michael E Hood
- Department of Biology, Amherst College, Amherst, Massachusetts, 01002
| | | | - Janis Antonovics
- Department of Biology, University of Virginia, Charlottesville, Virginia, 22904
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10
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Stone JD, Olson MS. Pollination context alters female advantage in gynodioecious
Silene vulgaris. J Evol Biol 2017; 31:111-122. [DOI: 10.1111/jeb.13203] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2015] [Revised: 10/14/2017] [Accepted: 10/26/2017] [Indexed: 11/30/2022]
Affiliation(s)
- J. D. Stone
- Department of Biology and Wildlife University of Alaska Fairbanks Fairbanks AK USA
| | - M. S. Olson
- Department of Biology and Wildlife University of Alaska Fairbanks Fairbanks AK USA
- Institute of Arctic Biology University of Alaska Fairbanks Fairbanks AK USA
- Department of Biological Sciences Texas Tech University Lubbock TX USA
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11
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Chen J, Niu Y, Li Z, Yang Y, Sun H. Sex allocation in gynodioecious Cyananthus delavayi differs between gender morphs and soil quality. PLANT REPRODUCTION 2017; 30:107-117. [PMID: 28597166 DOI: 10.1007/s00497-017-0303-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Accepted: 05/27/2017] [Indexed: 06/07/2023]
Abstract
Sex allocation in Cyananthus delavayi. Gynodioecy, where females and hermaphrodites coexist in the same natural population, is particularly suitable for predicting the ecological pressures that drive the stability of gender polymorphism. Since females have a disadvantage in that they only contribute to the next generation via ovules, they should gain an advantage via other means, of which resource allocation is an important component. Thus, to study their sex allocation is very helpful to understand how the dimorphic sexual system is maintained in natural systems. We studied the sex allocation patterns and reproductive output of the gynodioecious Cyananthus delavayi in three populations with different soil qualities (organic matter, N, P and K). The hermaphroditic flowers and pistils were much larger than those of female individuals. Although both gender morphs invested similar biomass in the pistils, females allocated more of their resource pool to the seed production, while hermaphrodites allocated more to pollinator advertisement. The pollen production of hermaphrodites did not differ between populations, suggesting that pollen production by hermaphrodites was not limited by soil nutrients. Fruit set of females, but not hermaphrodites, decreased with declining soil quality, whereas seeds per fruit of both females and hermaphrodites were highest in poor soils. Overall, this study shows that females achieve greater reproductive success by allocating more of their resource pool to enhancing seed production, which should favor their presence in gynodioecious populations. The hermaphrodites achieve reproductive success from both pollen and seed production, and unnecessarily reduce their allocation to pollen production. Soil quality should explain, at least partially, the sexual allocation patterns. Furthermore, some of our findings contradict previous hypotheses, thus adding a new example to the body of research on plant sex allocation and the development of future theories.
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Affiliation(s)
- Jianguo Chen
- Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, Yunnan, China
| | - Yang Niu
- Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, Yunnan, China
| | - Zhimin Li
- School of Life Sciences, Yunnan Normal University, Kunming, Yunnan, China
| | - Yang Yang
- Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, Yunnan, China.
| | - Hang Sun
- Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, Yunnan, China.
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12
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Bruijning M, Visser MD, Muller-Landau HC, Wright SJ, Comita LS, Hubbell SP, de Kroon H, Jongejans E. Surviving in a Cosexual World: A Cost-Benefit Analysis of Dioecy in Tropical Trees. Am Nat 2017; 189:297-314. [PMID: 28221824 DOI: 10.1086/690137] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Dioecy has a demographic disadvantage compared with hermaphroditism: only about half of reproductive adults produce seeds. Dioecious species must therefore have fitness advantages to compensate for this cost through increased survival, growth, and/or reproduction. We used a full life cycle approach to quantify the demographic costs and benefits associated with dioecy while controlling for demographic differences between dioecious and hermaphroditic species related to other functional traits. The advantage of this novel approach is that we can focus on the effect of breeding system across a diverse tree community. We built a composite integral projection model for hermaphroditic and dioecious tree populations from Barro Colorado Island, Panama, using long-term demographic and newly collected reproductive data. Integration of all costs and benefits showed that compensation was realized through increased seed production, resulting in no net costs of dioecy. Compensation was also facilitated by the low contribution of reproduction to population growth. Estimated positive effects of dioecy on tree growth and survival were small and insignificant for population growth rates. Our model revealed that, for long-lived organisms, the cost of having males is smaller than generally expected. Hence, little compensation is required for dioecious species to maintain population growth rates similar to those of hermaphroditic species.
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13
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Van Etten ML, Chang SM. Frequency-dependent pollinator discrimination acts against female plants in the gynodioecious Geranium maculatum. ANNALS OF BOTANY 2014; 114:1769-78. [PMID: 25326647 PMCID: PMC4649693 DOI: 10.1093/aob/mcu204] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2014] [Accepted: 09/01/2014] [Indexed: 06/04/2023]
Abstract
BACKGROUND AND AIMS Gynodioecy, the co-occurrence of female and hermaphroditic individuals, is thought to be an intermediate step between hermaphroditism and separate sexes, a major transition in flowering plants. Because retaining females in a population requires that they have increased seed fitness (to compensate for the lack of pollen fitness), factors that affect seed fitness are of great importance to the evolution of this mating system and have often been studied. However, factors negatively affecting female fitness are equally important and have been largely neglected. One such factor stems from female flowers being less attractive to insects than hermaphrodite flowers, thereby decreasing their relative fitness. METHODS To test the severity and consequences of this type of pollinator discrimination in Geranium maculatum, experimental populations with the range of sex ratios observed in nature were created, ranging from 13 % to 42 % females. Pollinators were observed in order to measure the strength of discrimination, and pollen deposition and seed production of both sexes were measured to determine the fitness consequences of this discrimination. Additionally a comparison was made across the sex ratios to determine whether discrimination was frequency-dependent. KEY RESULTS It was found that female flowers, on average, were visited at half of the rate of hermaphrodite flowers, which decreased their pollen receipt and seed production. Additionally, females were most discriminated against when rare, due to both changes in the pollinators' behaviour and a shift in pollinator composition. CONCLUSIONS The results suggest that pollinator discrimination negatively affects females' relative fitness when they are rare. Thus, the initial spread of females in a population, the first step in the evolution of gynodioecy, may be made more difficult due to pollinator discrimination.
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Affiliation(s)
- Megan L Van Etten
- Institute of Agriculture and Environment, Massey University, Palmerston North, New Zealand
| | - Shu-Mei Chang
- Plant Biology Department, University of Georgia, Athens, GA 30602, USA
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14
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Liston A, Cronn R, Ashman TL. Fragaria: a genus with deep historical roots and ripe for evolutionary and ecological insights. AMERICAN JOURNAL OF BOTANY 2014; 101:1686-99. [PMID: 25326614 DOI: 10.3732/ajb.1400140] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The cultivated strawberry, Fragaria ×ananassa, is one of the youngest domesticated plants. Its 18th century origin via hybridization in Europe between the North American F. virginiana and the South American F. chiloensis was documented by the botanist Antoine Nicolas Duchesne. His 1766 "Natural History of Strawberries" is an extraordinary work that integrates fundamental discoveries on the biology, ecology, and phylogeny of Fragaria with applied information on cultivation and ethnobotanical uses, serving as an inspiration for current research in the genus. Fragaria species exhibit the full range of sexual systems in the gynodioecy pathway from hermaphroditism to dioecy (and back again), as well as variation in self-compatibility, and evidence of sex chromosomes with female heterogamety. The genus is also characterized by interspecific hybridization and polyploidy, with a natural range of ploidy levels from diploids to decaploids. This biological diversity, combined with the availability of genomic resources and the ease of growing and experimenting with the plants, makes Fragaria a very attractive system for ecological and evolutionary genomics. The goal of this review is to introduce Fragaria as a model genus and to provide a roadmap for future integrative research. These research directions will deepen our understanding of the ecological and evolutionary context that shaped the ancestors of the cultivated strawberry, not only providing information that can be applied to efforts to shape the future of this important fruit crop but also our understanding of key transitions in plant evolution.
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Affiliation(s)
- Aaron Liston
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon 97331 USA
| | - Richard Cronn
- Pacific Northwest Research Station, USDA Forest Service, Corvallis, Oregon 97331 USA
| | - Tia-Lynn Ashman
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 USA
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Pannell JR, Eppley SM, Dorken ME, Berjano R. Regional variation in sex ratios and sex allocation in androdioecious Mercurialis annua. J Evol Biol 2014; 27:1467-77. [PMID: 24618014 DOI: 10.1111/jeb.12352] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Revised: 02/03/2014] [Accepted: 02/03/2014] [Indexed: 11/29/2022]
Abstract
In androdioecious metapopulations, where males co-occur with hermaphrodites, the absence of males from certain populations or regions may be explained by locally high selfing rates, high hermaphrodite outcross siring success (e.g. due to high pollen production by hermaphrodites), or to stochastic processes (e.g. the failure of males to invade populations or regions following colonization or range expansion by hermaphrodites). In the Iberian Peninsula and Morocco, the presence of males with hermaphrodites in the wind-pollinated androdioecious plant Mercurialis annua (Euphorbiaceae) varies both among populations within relatively small regions and among regions, with some regions lacking males from all populations. The species is known to have expanded its range into the Iberian Peninsula from a southern refugium. To account for variation in male presence in M. annua, we test the following hypotheses: (1) that males are absent in areas where plant densities are lower, because selfing rates should be correspondingly higher; (2) that males are absent in areas where hermaphrodites produce more pollen; and (3) that males are absent in areas where there is an elevated proportion of populations in which plant density and hermaphrodite pollen production disfavour their invasion. We found support for predictions two and three in Morocco (the putative Pleistocene refugium for M. annua) but no support for any hypothesis in Iberia (the expanded range). Our results are partially consistent with a hypothesis of sex-allocation equilibrium for populations in Morocco; in Iberia, the absence of males from large geographical regions is more consistent with a model of sex-ratio evolution in a metapopulation with recurrent population turnover. Our study points to the role of both frequency-dependent selection and contingencies imposed by colonization during range expansions and in metapopulations.
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Affiliation(s)
- J R Pannell
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
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16
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Yakimowski SB, Barrett SCH. Variation and evolution of sex ratios at the northern range limit of a sexually polymorphic plant. J Evol Biol 2014; 27:1454-66. [DOI: 10.1111/jeb.12322] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Revised: 12/08/2013] [Accepted: 12/16/2013] [Indexed: 10/25/2022]
Affiliation(s)
- S. B. Yakimowski
- Department of Ecology and Evolutionary Biology; University of Toronto; Toronto ON Canada
| | - S. C. H. Barrett
- Department of Ecology and Evolutionary Biology; University of Toronto; Toronto ON Canada
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17
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Phylogenetic and biogeographic analyses of the Sino-Himalayan endemic genus Cyananthus (Campanulaceae) and implications for the evolution of its sexual system. Mol Phylogenet Evol 2013; 68:482-97. [DOI: 10.1016/j.ympev.2013.04.027] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2012] [Revised: 04/14/2013] [Accepted: 04/22/2013] [Indexed: 11/21/2022]
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18
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Sinclair JP, Maxwell GD, Freeman DC. Consanguineous mating, specialization, and the environment: how multiple variable interactions affect the evolution of dioecy. AMERICAN JOURNAL OF BOTANY 2013; 100:1038-1049. [PMID: 23620206 DOI: 10.3732/ajb.1200579] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
PREMISE The evolution of dioecy in plants is usually modeled as a consequence of self-fertilization. While increased seed and pollen production and dispersal patterns of specialized unisexuals have been examined, mating among relatives and interaction effects have been largely ignored. Here, we examine multiple variables simultaneously providing a more ecologically realistic set of conditions favoring the evolution of dioecy. • METHODS We developed two complementary models to explore the evolution of dioecious plants. In both models, we examined the effects of inbreeding, compensation, and specialization on unisexual invasibility and were able to directly measure the influence of related matings on such a system. • KEY RESULTS Our results support previous studies indicating dispersal specialization, consanguineous mating, and inbreeding depression facilitate the evolution of dioecy. However, our results suggest that it is the interaction effect of multiple forces acting simultaneously that allows for unisexual invasion at thresholds and frequencies witnessed in nature. Additionally, our results suggest that subdioecious populations often result, and depending on population conditions, dioecy evolves at different rates, lending importance to the ecological and life history conditions of the species. • CONCLUSION Mating among relatives significantly enhances the invasibility of a unisexual mutant into a hermaphroditic population and lowers the levels of inbreeding depression required for invasion than previously reported conditions for unisexual invasion especially, if we consider multiple pressures simultaneously.
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Affiliation(s)
- Jordan P Sinclair
- Wayne State University, Department of Biological Sciences, Detroit, MI 48202, USA
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19
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Sakai AK, Weller SG, Campbell DR, Culley TM, Dunbar-Wallis AK, Andres AM. Measure for measure: comparing morphological and biomass traits for sex allocation in two gynodioecious species. AMERICAN JOURNAL OF BOTANY 2013; 100:1071-1082. [PMID: 23703857 DOI: 10.3732/ajb.1300045] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
PREMISE OF THE STUDY Sex allocation models assume male and female traits are measured in a common currency, allocation traits show heritability, and tradeoffs between investment in the two sexual functions occur. The potential for model predictions and genetic parameters to depend on the currency used is not well understood, despite frequent use of measures not in a common currency. • METHODS We analyzed the relationship between common currency (biomass of carpels, seeds, and stamens) measures and morphological measures (numbers of ovules, seeds, and pollen) in Schiedea salicaria (12-13% females) and S. adamantis (39% females), two closely related gynodioecious species. Additionally, we compared heritabilities and genetic correlations for male and female allocation between these two types of measures. • KEY RESULTS Ovule, seed, and pollen number show greater sexual dimorphism in S. adamantis than in S. salicaria. Most but not all morphological traits and analogous biomass traits are highly correlated with a linear relationship. Narrow-sense heritabilities based on the two methods are often similar, but higher for ovule number than carpel mass and lower for anther number than stamen mass in S. adamantis. Neither trait type shows negative genetic correlations between male and female function. • CONCLUSIONS Both trait types show greater sexual dimorphism in S. adamantis, and significant heritabilities suggest that morphological traits will continue to evolve with breeding system changes. Although most relationships between morphological and biomass traits are linear, curvilinear relationships for two traits suggest that caution is warranted if morphological and common currency traits are used interchangeably in fitness gain curves.
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Affiliation(s)
- Ann K Sakai
- Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697, USA.
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20
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Lorenzi MC, Sella G. In Between Breeding Systems: Neither Dioecy Nor Androdioecy Explains Sexual Polymorphism in Functionally Dioecious Worms. Integr Comp Biol 2013; 53:689-700. [DOI: 10.1093/icb/ict043] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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21
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Salamone I, Govindarajulu R, Falk S, Parks M, Liston A, Ashman TL. Bioclimatic, ecological, and phenotypic intermediacy and high genetic admixture in a natural hybrid of octoploid strawberries. AMERICAN JOURNAL OF BOTANY 2013; 100:939-950. [PMID: 23579477 DOI: 10.3732/ajb.1200624] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
PREMISE OF THE STUDY Hybrid zones provide "natural laboratories" for understanding the processes of selection, reinforcement, and speciation. We sought to gain insight into the degree of introgression and the extent of ecological-phenotypic intermediacy in the natural hybrid strawberry, Fragaria × ananassa subsp. cuneifolia. • METHODS We used whole-plastome sequencing to identify parental species-specific (Fragaria chiloensis and F. virginiana) chloroplast single-nucleotide polymorphisms and combined the use of these with nuclear microsatellite markers to genetically characterize the hybrid zone. We assessed the potential role of selection in the observed geographic patterns by bioclimatically characterizing the niche of the hybrid populations and phenotypically characterizing hybrid individuals of known genomic constitution. • KEY RESULTS Significant admixture and little overall maternal bias in chloroplast or nuclear genomes suggest a high degree of interfertility among the parental and hybrid species and point to a long history of backcrossing and genetic mixing in the hybrid zone. Even though hybrids were phenotypically intermediate to the parental species, there was a discernible fingerprint of the parental genotype within hybrid individuals. Thus, although the pattern of introgression observed suggests geographic limitations to gene flow, it may be reinforced by selection for specific parental traits in the bioclimatically intermediate habitat occupied by the hybrid. • CONCLUSIONS This work uncovered the genetic complexity underlying the hybrid zone of the wild relatives of the cultivated strawberry. It lays the foundation for experimental dissection of the causes of genomic introgression and nuclear-cytoplasmic disassociation, and for understanding other parts of Fragaria evolutionary history.
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Affiliation(s)
- Isabella Salamone
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
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22
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Litrico I, Maurice S. Resources, competition and selfing: their influence on reproductive system evolution. Evol Ecol 2012. [DOI: 10.1007/s10682-012-9613-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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23
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Roumet M, Ostrowski MF, David J, Tollon C, Muller MH. Estimation of mating system parameters in an evolving gynodioecous population of cultivated sunflower (Helianthus annuus L.). Heredity (Edinb) 2012; 108:366-74. [PMID: 21915147 PMCID: PMC3313044 DOI: 10.1038/hdy.2011.79] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2011] [Revised: 07/22/2011] [Accepted: 08/02/2011] [Indexed: 11/09/2022] Open
Abstract
Cultivated plants have been molded by human-induced selection, including manipulations of the mating system in the twentieth century. How these manipulations have affected realized parameters of the mating system in freely evolving cultivated populations is of interest for optimizing the management of breeding populations, predicting the fate of escaped populations and providing material for experimental evolution studies. To produce modern varieties of sunflower (Helianthus annuus L.), self-incompatibility has been broken, recurrent generations of selfing have been performed and male sterility has been introduced. Populations deriving from hybrid-F1 varieties are gynodioecious because of the segregation of a nuclear restorer of male fertility. Using both phenotypic and genotypic data at 11 microsatellite loci, we analyzed the consanguinity status of plants of the first three generations of such a population and estimated parameters related to the mating system. We showed that the resource reallocation to seed in male-sterile individuals was not significant, that inbreeding depression on seed production averaged 15-20% and that cultivated sunflower had acquired a mixed-mating system, with ∼50% of selfing among the hermaphrodites. According to theoretical models, the female advantage and the inbreeding depression at the seed production stage were too low to allow the persistence of male sterility. We discuss our methods of parameter estimation and the potential of such study system in evolutionary biology.
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Affiliation(s)
- M Roumet
- UMR AGAP 1334, INRA, Montpellier, Mauguio, France
| | | | - J David
- UMR AGAP 1334, INRA, Montpellier, Mauguio, France
| | - C Tollon
- UMR AGAP 1334, INRA, Montpellier, Mauguio, France
| | - M-H Muller
- UMR AGAP 1334, INRA, Montpellier, Mauguio, France
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Dufay M, Billard E. How much better are females? The occurrence of female advantage, its proximal causes and its variation within and among gynodioecious species. ANNALS OF BOTANY 2012; 109:505-19. [PMID: 21459860 PMCID: PMC3278283 DOI: 10.1093/aob/mcr062] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2010] [Accepted: 02/10/2011] [Indexed: 05/09/2023]
Abstract
BACKGROUND Gynodioecy is a reproductive system of interest for evolutionary biologists, as it poses the question of how females can be maintained while competing with hermaphrodites that possess both male and female functions. One necessary condition for the maintenance of this polymorphism is the occurrence of a female advantage, i.e. a better seed production or quality by females compared with hermaphrodites. Theoretically, its magnitude can be low when sterility mutations are cytoplasmic, while a 2-fold advantage is needed in the case of nuclear sterility. Such a difference is often thought to be due to reduced inbreeding depression in obligatory outcrossed females. Finally, variation in sex ratio and female advantage occur among populations of some gynodioecious species, though the prevalence of such variation is unknown. SCOPE By reviewing and analysing the data published on 48 gynodioecious species, we examined three important issues about female advantage. (1) Are reduced selfing and inbreeding depression likely to be the major cause of female advantage? (2) What is the magnitude of female advantage and does it fit theoretical predictions? (3) Does the occurrence or the magnitude of female advantage vary among populations within species and why? CONCLUSIONS It was found that a female advantage occurred in 40 species, with a magnitude comprised between 1 and 2 in the majority of cases. In many species, reduced selfing may not be a necessary cause of this advantage. Finally, female advantage varied among populations in some species, but both positive and negative correlations were found with female frequency. The role of reduced selfing in females for the evolution of gynodioecy, as well as the various processes that affect sex ratios and female advantage in populations are discussed.
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Affiliation(s)
- Mathilde Dufay
- Laboratoire GEPV FRE-CNRS 3268, Université des Sciences et Technologies de Lille - Lille 1, Villeneuve d'Ascq Cedex, France.
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25
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Li J, Koski MH, Ashman TL. Functional characterization of gynodioecy in Fragaria vesca ssp. bracteata (Rosaceae). ANNALS OF BOTANY 2012; 109:545-52. [PMID: 22052984 PMCID: PMC3278295 DOI: 10.1093/aob/mcr279] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2011] [Accepted: 10/03/2011] [Indexed: 05/23/2023]
Abstract
BACKGROUND AND AIMS Gynodioecy is a phylogenetically widespread and important sexual system where females coexist with hermaphrodites. Because dioecy can arise from gynodioecy, characterization of gynodioecy in close relatives of dioecious and sub-dioecious species can provide insight into this transition. Thus, we sought to determine whether Fragaria vesca ssp. bracteata, a close relative to F. chiloensis and F. virginiana, exhibits the functional and population genetic hallmarks of a gynodioecious species. METHODS We compared reproductive allocation of females and hermaphrodites grown in the greenhouse and estimated genetic diversity (allelic diversity, heterozygosity) and inbreeding coefficients for field-collected adults of both sexes using simple sequence repeat (SSR) markers. We estimated mating system and early seed fitness from open-pollinated families of both sex morphs. KEY RESULTS Under greenhouse conditions, females and hermaphrodites allocated similarly to all reproductive traits except flower number, and, as a consequence, females produced 30 % fewer seeds per plant than hermaphrodites. Under natural conditions, hermaphrodites produce seeds by self-fertilization approx. 75 % of the time, and females produced outcrossed seeds with very little biparental inbreeding. Consistent with inbreeding depression, seeds from open-pollinated hermaphrodites were less likely to germinate than those from females, and family-level estimates of hermaphrodite selfing rates were negatively correlated with germination success and speed. Furthermore, estimates of inbreeding depression based on genetic markers and population genetic theory indicate that inbreeding depression in the field could be high. CONCLUSIONS The joint consideration of allocation and mating system suggests that compensation may be sufficient to maintain females given the current understanding of sex determination. Fragaria vesca ssp. bracteata exhibited similar sex morph-dependent patterns of mating system and genetic diversity, but less reproductive trait dimorphism, than its sub-dioecious and dioecious congeners.
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Affiliation(s)
- Junmin Li
- Institute of Ecology, Taizhou University, Linhai 317000, China
| | - Matthew H. Koski
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260-3929, USA
| | - Tia-Lynn Ashman
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260-3929, USA
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26
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De Cauwer I, Arnaud JF, Courseaux A, Dufay M. Sex-specific fitness variation in gynodioecious Beta vulgaris ssp. maritima: do empirical observations fit theoretical predictions? J Evol Biol 2011; 24:2456-72. [PMID: 21955089 DOI: 10.1111/j.1420-9101.2011.02380.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
In gynodioecious species, in which hermaphroditic and female plants co-occur, the maintenance of sexual polymorphism relies on the genetic determination of sex and on the relative fitness of the different phenotypes. Flower production, components of male fitness (pollen quantity and pollen quality) and female fitness (fruit and seed set) were measured in gynodioecious Beta vulgaris spp. maritima, in which sex is determined by interactions between cytoplasmic male sterility (CMS) genes and nuclear restorers of male fertility. The results suggested that (i) female had a marginal advantage over hermaphrodites in terms of flower production only, (ii) restored CMS hermaphrodites (carrying both CMS genes and nuclear restorers) suffered a slight decrease in fruit production compared to non-CMS hermaphrodites and (iii) restored CMS hermaphrodites were poor pollen producers compared to non-CMS hermaphrodites, probably as a consequence of complex determination of restoration. These observations potentially have important consequences for the conditions of maintenance of sexual polymorphism in B. vulgaris and are discussed in the light of existing theory on evolutionary dynamics of gynodioecy.
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Affiliation(s)
- I De Cauwer
- Laboratoire de Génétique et Évolution des Populations Végétales, FRE CNRS 3268, Bâtiment SN2, Université des Sciences et Technologies de Lille - Lille 1, Villeneuve d'Ascq Cedex, France.
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27
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Perry LE, Dorken ME. The evolution of males: support for predictions from sex allocation theory using mating arrays of sagittaria latifolia (alismataceae). Evolution 2011; 65:2782-91. [PMID: 21967421 DOI: 10.1111/j.1558-5646.2011.01344.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Investment in male function should often yield diminishing fitness returns, subjecting the evolution of male phenotypes to substantial constraints. In plants, the subdivision of male function via the gradual presentation of pollen might minimize these constraints by preventing the saturation of receptive stigmas. Here, we report on an investigation of (1) patterns of investment in male function by plants in hermaphroditic (monoecious) and dioecious populations of Sagittaria latifolia, and (2) patterns of siring success by males versus hermaphrodites in experimental mating arrays. We show that in natural populations, males from dioecious populations had greater investment in male function than hermaphrodites in monoecious populations. However, as a proportion of total flower production, males presented substantially fewer flowers at once than hermaphrodites. In comparison with hermaphrodites, therefore, males prolonged the period over which they presented pollen. In mating arrays comprised of females, males, and hermaphrodites, siring success by males increased linearly with flower production. This finding is consistent with the existence of a linear gain curve for male function in S. latifolia and supports the idea that the gradual deployment of male function enables plants to avoid diminishing returns on the investment in male function.
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Affiliation(s)
- Laura E Perry
- Department of Biology, Trent University, Peterborough, ON, K9J 7B8, Canada.
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28
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Spigler RB, Ashman TL. Sex ratio and subdioecy in Fragaria virginiana: the roles of plasticity and gene flow examined. THE NEW PHYTOLOGIST 2011; 190:1058-1068. [PMID: 21352233 DOI: 10.1111/j.1469-8137.2011.03657.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Here we examined the roles of sex-differential plasticity (SDP) and gene flow in sex ratio evolution of subdioecious Fragaria virginiana. We assessed whether female frequency varied with resource availability in 17 natural populations and then characterized plasticity and mean investment in allocation to female function at flower and plant levels in the sex morphs in the glasshouse. We estimated patterns of population divergence using five microsatellite markers. We reveal SDP in fruit production substantial enough to translate into a higher equilibrium female frequency at low resources. Thus SDP can account, in part, for the strong negative relationship between female frequency and resources found in the field. Pollen-bearing morphs varied in plasticity across populations, and the degree of plasticity in fruit number was positively correlated with in situ variation in nitrogen (N) availability, suggesting an adaptive component to sex-allocation plasticity. Low neutral genetic differentiation, indicating high gene flow or recent divergence, may contribute to the absence of population differentiation in fruit-setting ability of pollen-bearing morphs despite considerable sex ratio variation. We consider how these processes, in addition to other features of this system, may work in concert to influence sex ratios and to hinder the evolution of dioecy in F. virginiana.
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Affiliation(s)
- Rachel B Spigler
- Department of Biological Sciences, University of Pittsburgh, 4249 Fifth Ave, Pittsburgh, PA 15260-3929, USA
| | - Tia-Lynn Ashman
- Department of Biological Sciences, University of Pittsburgh, 4249 Fifth Ave, Pittsburgh, PA 15260-3929, USA
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29
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Garraud C, Brachi B, Dufay M, Touzet P, Shykoff JA. Genetic determination of male sterility in gynodioecious Silene nutans. Heredity (Edinb) 2011; 106:757-64. [PMID: 20808324 PMCID: PMC3186230 DOI: 10.1038/hdy.2010.116] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2010] [Revised: 07/30/2010] [Accepted: 07/30/2010] [Indexed: 11/08/2022] Open
Abstract
Gynodioecy, the coexistence of female and hermaphrodite plants within a species, is often under nuclear-cytoplasmic sex determination, involving cytoplasmic male sterility (CMS) genes and nuclear restorers. A good knowledge of CMS and restorer polymorphism is essential for understanding the evolution and maintenance of gynodioecy, but reciprocal crossing studies remain scarce. Although mitochondrial diversity has been studied in a few gynodioecious species, the relationship between mitotype diversity and CMS status is poorly known. From a French sample of Silene nutans, a gynodioecious species whose sex determination remains unknown, we chose the four most divergent mitotypes that we had sampled at the cytochrome b gene and tested by reciprocal crosses whether they carry distinct CMS genes. We show that gynodioecy in S. nutans is under nuclear-cytoplasmic control, with at least two different CMSs and up to four restorers with epistatic interactions. Female occurrence and frequency were highly dependent on the mitotype, suggesting that the level of restoration varies greatly among CMSs. Two of the mitotypes, which have broad geographic distributions, represent different CMSs and are very unequally restored. We discuss the dynamics of gynodioecy at the large-scale meta-population level.
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Affiliation(s)
- C Garraud
- Laboratoire Ecologie, Systématique et Evolution, UMR 8079 Univ Paris-Sud, Orsay, France.
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30
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Spigler RB, Lewers KS, Ashman TL. GENETIC ARCHITECTURE OF SEXUAL DIMORPHISM IN A SUBDIOECIOUS PLANT WITH A PROTO-SEX CHROMOSOME. Evolution 2010; 65:1114-26. [DOI: 10.1111/j.1558-5646.2010.01189.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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31
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Preece T, Mao Y. The evolution of gynodioecy on a lattice. J Theor Biol 2010; 266:219-25. [PMID: 20599548 DOI: 10.1016/j.jtbi.2010.06.025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2010] [Revised: 06/14/2010] [Accepted: 06/16/2010] [Indexed: 11/26/2022]
Abstract
Gynodioecy is a breeding system in plants where populations consist of hermaphrodites and females. The females result from a genetic mutation which impairs pollen production in hermaphrodite plants. Most previous models for the evolution of gynodioecy do not take into account any spatial detail, which might be expected to play an important role in populations with short range interactions caused by poor or no locomotion. In this article we present a generalised mean-field analysis (which ignores any spatial detail), together with stochastic spatial simulations, to investigate the spatial effect on the evolution of gynodioecy. We show that, in a population of hermaphrodites where male sterility is caused by a dominant allele in a nuclear gene, mean-field calculations greatly underestimate the reproductive advantage females require to become viable under spatial constraints. This suggests that gynodioecy is less likely to evolve in plants with more localised pollination and seed setting. This may have implications for the evolution of dioecy, a breeding system in plants where the population consists of males and females, as gynodioecy is thought to be a route to dioecy. Our results also demonstrate that a lower frequency of females should be expected for gynodioecious populations when interactions are local. This is relevant when comparing the results of breeding experiments with observations of female frequency in the wild.
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Affiliation(s)
- T Preece
- School of Physics and Astronomy, University of Nottingham, University Park, Nottingham NG7 2RD, UK.
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32
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Lu Y, Luo YB, Huang SQ. Reduced recombination in gynodioecious populations of a facultative apomictic orchid. PLANT BIOLOGY (STUTTGART, GERMANY) 2010; 12:814-819. [PMID: 20701706 DOI: 10.1111/j.1438-8677.2009.00283.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Many plants combine sexual reproduction with some form of asexual reproduction to different degrees, and lower genetic diversity is expected with asexuality. Moreover, the ratios of sexual morphs in species with gender dimorphism are expected to vary in proportion to the reproductive success of the sexual process. Hence, sex ratios can directly influence the genetic structure and diversity of a population. We investigated genotypic diversity in 23 populations of a facultative, apomictic gynodioecious orchid, Satyrium ciliatum, to examine the effect on genotypic diversity of variation in the frequency of females and in the amount of sexual reproduction. The study involved one pure female, seven gynodioecious (both females and hermaphrodites present) and 15 hermaphroditic populations. Pollinia receipt was higher in hermaphroditic than in gynodioecious populations. Analyses of variation in ISSRs demonstrated that genotypic diversity was high in all populations and was not significantly different between hermaphroditic and gynodioecious populations. We used character compatibility analysis to determine the extent to which recombination by sexual reproduction contributed to genotypic diversity. The results indicate that the contribution of recombination to genotypic diversity is higher in hermaphroditic than in gynodioecious populations, consistent with the finding that hermaphroditic populations received higher amounts of pollinia. Our finding of reduced recombination in gynodioecious populations suggests that maintenance of sex in hermaphrodites plays an important role in generating genotypic diversity in this apomictic orchid.
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Affiliation(s)
- Y Lu
- College of Life Sciences, Wuhan University, Wuhan, China
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FROMHAGE LUTZ, KOKKO HANNA. Spatial seed and pollen games: dispersal, sex allocation, and the evolution of dioecy. J Evol Biol 2010; 23:1947-56. [DOI: 10.1111/j.1420-9101.2010.02057.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Barrett SCH. Darwin's legacy: the forms, function and sexual diversity of flowers. Philos Trans R Soc Lond B Biol Sci 2010; 365:351-68. [PMID: 20047864 PMCID: PMC2838255 DOI: 10.1098/rstb.2009.0212] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Charles Darwin studied floral biology for over 40 years and wrote three major books on plant reproduction. These works have provided the conceptual foundation for understanding floral adaptations that promote cross-fertilization and the mechanisms responsible for evolutionary transitions in reproductive systems. Many of Darwin's insights, gained from careful observations and experiments on diverse angiosperm species, remain remarkably durable today and have stimulated much current research on floral function and the evolution of mating systems. Here I review Darwin's seminal contributions to reproductive biology and provide an overview of the current status of research on several of the main topics to which he devoted considerable effort, including the consequences to fitness of cross- versus self-fertilization, the evolution and function of stylar polymorphisms, the adaptive significance of heteranthery, the origins of dioecy and related gender polymorphisms, and the transition from animal pollination to wind pollination. Post-Darwinian perspectives on floral function now recognize the importance of pollen dispersal and male outcrossed siring success in shaping floral adaptation. This has helped to link work on pollination biology and mating systems, two subfields of reproductive biology that remained largely isolated during much of the twentieth century despite Darwin's efforts towards integration.
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Affiliation(s)
- Spencer C H Barrett
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario M5S 3B2, Canada.
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Spigler RB, Lewers KS, Johnson AL, Ashman TL. Comparative Mapping Reveals Autosomal Origin of Sex Chromosome in Octoploid Fragaria virginiana. J Hered 2010; 101 Suppl 1:S107-17. [DOI: 10.1093/jhered/esq001] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
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Wilk JA, Kramer AT, Ashley MV. High variation in clonal vs. sexual reproduction in populations of the wild strawberry, Fragaria virginiana (Rosaceae). ANNALS OF BOTANY 2009; 104:1413-9. [PMID: 19797422 PMCID: PMC2778387 DOI: 10.1093/aob/mcp239] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2009] [Revised: 06/12/2009] [Accepted: 08/11/2009] [Indexed: 05/21/2023]
Abstract
BACKGROUND AND AIMS Many plants reproduce both clonally and sexually, and the balance between the two modes of reproduction will vary among populations. Clonal reproduction was characterized in three populations of the wild strawberry, Fragaria virginiana, to determine the extent that reproductive mode varied locally between sites. The study sites were fragmented woodlands in Cook County, Illinois, USA. METHODS A total of 95 strawberry ramets were sampled from the three sites via transects. Ramets were mapped and genotyped at five variable microsatellite loci. The variability at these five loci was sufficient to assign plants to clones with high confidence, and the spatial pattern of genets was mapped at each site. KEY RESULTS A total of 27 distinct multilocus genotypes were identified. Of these, 18 genotypes were detected only once, with the remaining nine detected in multiple ramets. The largest clone was identified in 16 ramets. No genets were shared between sites, and each site exhibited markedly different clonal and sexual recruitment patterns, ranging from two non-overlapping and widespread genets to 19 distinct genets. Only one flowering genet was female; the remainder were hermaphrodites. CONCLUSIONS Local population history or fine-scale ecological differences can result in dramatically different reproductive patterns at small spatial scales. This finding may be fairly widespread among clonal plant species, and studies that aim to characterize reproductive modes in species capable of asexual reproduction need to evaluate reproductive modes in multiple populations and sites.
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Affiliation(s)
- John A. Wilk
- Department of Biological Sciences, University of Illinois Chicago, M/C 066, 845 W. Taylor St, Chicago IL 60607, USA
| | - Andrea T. Kramer
- Department of Biological Sciences, University of Illinois Chicago, M/C 066, 845 W. Taylor St, Chicago IL 60607, USA
- Botanic Gardens Conservation International and Chicago Botanic Garden, 1000 Lake Cook Road, Glencoe, IL 60022, USA
| | - Mary V. Ashley
- Department of Biological Sciences, University of Illinois Chicago, M/C 066, 845 W. Taylor St, Chicago IL 60607, USA
- For correspondence. E-mail
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Van Etten ML, Chang SM. Effects of environmental heterogeneity on the distribution of sexes within and among populations in a gynodioecious species, Geranium maculatum. THE NEW PHYTOLOGIST 2009; 183:649-660. [PMID: 19659586 DOI: 10.1111/j.1469-8137.2009.02940.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Populations containing both females and hermaphrodites (dimorphic) are generally found in drier sites than those with only hermaphrodites (monomorphic). The sex-differential plasticity hypothesis (SDP) suggests that this is caused by hermaphrodites reducing allocation to seeds in harsh environments, allowing female establishment. We proposed that a similar process could explain sex distribution within populations. We compared light availability and soil moisture between sites of three monomorphic and three dimorphic populations of Geranium maculatum and between microsites occupied by females and hermaphrodites within populations. We also correlated seed production in dimorphic populations with environmental measures. We found that dimorphic and monomorphic populations occurred in sites with similar soil moisture but within two dimorphic populations females occurred in drier microsites than hermaphrodites, as predicted by the SDP hypothesis. Contrary to the predictions, hermaphrodites' seed production was not influenced by the environment. Rather, females' seed production was correlated with environmental conditions in two populations, although the direction of the correlation differed between populations. Our results suggest that in this species, the SDP hypothesis does not explain sex distribution among or within populations. However, microsite environments may influence the distribution of sexes within a population and potentially aid in maintaining gynodioecy.
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Affiliation(s)
- Megan L Van Etten
- Department of Plant Biology, University of Georgia, Athens, GA 30602, USA
| | - Shu-Mei Chang
- Department of Plant Biology, University of Georgia, Athens, GA 30602, USA
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Case AL, Ashman TL. Resources and pollinators contribute to population sex-ratio bias and pollen limitation inFragaria virginiana(Rosaceae). OIKOS 2009. [DOI: 10.1111/j.1600-0706.2009.17520.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Dorken ME, Pannell JR. Hermaphroditic Sex Allocation Evolves When Mating Opportunities Change. Curr Biol 2009; 19:514-7. [DOI: 10.1016/j.cub.2009.01.067] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2008] [Revised: 01/30/2009] [Accepted: 01/30/2009] [Indexed: 10/21/2022]
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Penet L, Collin CL, Ashman TL. Florivory increases selfing: an experimental study in the wild strawberry, Fragaria virginiana. PLANT BIOLOGY (STUTTGART, GERMANY) 2009; 11:38-45. [PMID: 19121112 DOI: 10.1111/j.1438-8677.2008.00141.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Florivores are antagonists that damage flowers, and have direct negative effects on flowering and pollination of the attacked plants. While florivory has mainly been studied for its consequences on seed production or siring success, little is known about its impact on mating systems. Damage to flowers can alter pollinator attraction to the plant and may therefore modify patterns of pollen transfer. However, the consequences of damage for mating systems can take two forms: a decrease in flower number reduces opportunities for intra-inflorescence pollen deposition (geitonogamy), which, in turn, may lead to a decrease in selfing; whereas a decrease in floral display may also reduce overall visitation and thus increase the chances of self-pollination via facilitated or autonomous autogamy. We investigated the effects of damage by a bud-clipping weevil (Anthonomus signatus) in Fragaria virginiana in an experimental setting mimicking natural conditions. We found that increased damage led to an increase in selfing, a result consistent with the increased autogamy pathway. We discuss the implications of this finding and evaluate the generality of florivore-mediated mating system expression.
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Affiliation(s)
- L Penet
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
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ROSAS F, DOMÍNGUEZ CA. Male sterility, fitness gain curves and the evolution of gender specialization from distyly in Erythroxylum havanense. J Evol Biol 2009; 22:50-9. [DOI: 10.1111/j.1420-9101.2008.01618.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Spigler RB, Lewers KS, Main DS, Ashman TL. Genetic mapping of sex determination in a wild strawberry, Fragaria virginiana, reveals earliest form of sex chromosome. Heredity (Edinb) 2008; 101:507-17. [PMID: 18797475 DOI: 10.1038/hdy.2008.100] [Citation(s) in RCA: 138] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The evolution of separate sexes (dioecy) from hermaphroditism is one of the major evolutionary transitions in plants, and this transition can be accompanied by the development of sex chromosomes. Studies in species with intermediate sexual systems are providing unprecedented insight into the initial stages of sex chromosome evolution. Here, we describe the genetic mechanism of sex determination in the octoploid, subdioecious wild strawberry, Fragaria virginiana Mill., based on a whole-genome simple sequence repeat (SSR)-based genetic map and on mapping sex determination as two qualitative traits, male and female function. The resultant total map length is 2373 cM and includes 212 markers on 42 linkage groups (mean marker spacing: 14 cM). We estimated that approximately 70 and 90% of the total F. virginiana genetic map resides within 10 and 20 cM of a marker on this map, respectively. Both sex expression traits mapped to the same linkage group, separated by approximately 6 cM, along with two SSR markers. Together, our phenotypic and genetic mapping results support a model of gender determination in subdioecious F. virginiana with at least two linked loci (or gene regions) with major effects. Reconstruction of parental genotypes at these loci reveals that both female and hermaphrodite heterogamety exist in this species. Evidence of recombination between the sex-determining loci, an important hallmark of incipient sex chromosomes, suggest that F. virginiana is an example of the youngest sex chromosome in plants and thus a novel model system for the study of sex chromosome evolution.
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Affiliation(s)
- R B Spigler
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260-3929, USA
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Ashman TL, Diefenderfer C. Sex ratio represents a unique context for selection on attractive traits: consequences for the evolution of sexual dimorphism. Am Nat 2008; 157:334-47. [PMID: 18707294 DOI: 10.1086/319192] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
We explored the idea that sex ratio represents a unique context for selection on attractive traits by manipulating sex ratio and pollinator abundance in experimental populations of a gender-dimorphic wild strawberry Fragaria virginiana. We found that increasing the frequency of functional males (the pollen-bearing morph) increased the frequency of pollen-collecting syrphid flies in the pollinator assemblage, decreased pollinator visitation to less preferred morph (females), and decreased the degree of pollen limitation of females. Moreover, sex ratio influenced the strength of selection on petal size through female fitness but did not alter the strength of selection through male fitness components, suggesting that sex ratio can alter the gender bias of selection on an attractive trait. This study of context-dependent selection has important implications for the evolution of sexual dimorphism in attractive traits. First, it suggests that only certain conditions generate male-biased selection and, thus, could lead to selection-driven male-biased petal size dimorphism. Second, it suggests that flexible pollinator foraging may be an important mechanism by which sex ratio influences selection on attractive traits. Finally, it implies that variation in sex ratio could limit the evolution of sexual dimorphism and/or could maintain genetic variation in attractive traits.
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Affiliation(s)
- T L Ashman
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA.
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Dorken ME, Pannell JR. Density-dependent regulation of the sex ratio in an annual plant. Am Nat 2008; 171:824-30. [PMID: 18429672 DOI: 10.1086/587524] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Sex ratios are subject to strong frequency-dependent selection regulated by the mating system and the relative male versus female investment. In androdioecious plant populations, where males co-occur with hermaphrodites, the sex ratio depends on the rate of self-fertilization by hermaphrodites and on the relative pollen production of males versus hermaphrodites. Here, we report evolutionary changes in the sex ratio from experimental mating arrays of the androdioecious plant Mercurialis annua. We found that the progeny sex ratio depended strongly on density, with fewer males in the progeny of plants grown under low density. This occurred in part because of a plastic adjustment in pollen production by hermaphrodites, which produced more pollen when grown at low density than at high density. Our results provide support for the prediction that environmental conditions govern sex ratios through their effects on the relative fertility of unisexual versus hermaphrodite individuals.
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Affiliation(s)
- Marcel E Dorken
- Department of Plant Sciences, South Parks Road, University of Oxford, Oxford OX1 3RB, United Kingdom.
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Dorken ME, Mitchard ETA. PHENOTYPIC PLASTICITY OF HERMAPHRODITE SEX ALLOCATION PROMOTES THE EVOLUTION OF SEPARATE SEXES: AN EXPERIMENTAL TEST OF THE SEX-DIFFERENTIAL PLASTICITY HYPOTHESIS USINGSAGITTARIA LATIFOLIA(ALISMATACEAE). Evolution 2008; 62:971-8. [DOI: 10.1111/j.1558-5646.2008.00336.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Bailey MF, Delph LF. Sex-ratio evolution in nuclear-cytoplasmic gynodioecy when restoration is a threshold trait. Genetics 2007; 176:2465-76. [PMID: 17717197 PMCID: PMC1950646 DOI: 10.1534/genetics.107.076554] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Gynodioecious plant species, which have populations consisting of female and hermaphrodite individuals, usually have complex sex determination involving cytoplasmic male sterility (CMS) alleles interacting with nuclear restorers of fertility. In response to recent evidence, we present a model of sex-ratio evolution in which restoration of male fertility is a threshold trait. We find that females are maintained at low frequencies for all biologically relevant parameter values. Furthermore, this model predicts periodically high female frequencies (>50%) under conditions of lower female seed fecundity advantages (compensation, x = 5%) and pleiotropic fitness effects associated with restorers of fertility (costs of restoration, y = 20%) than in other models. This model explains the maintenance of females in species that have previously experienced invasions of CMS alleles and the evolution of multiple restorers. Sensitivity of the model to small changes in cost and compensation values and to initial conditions may explain why populations of the same species vary widely for sex ratio.
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Affiliation(s)
- Maia F Bailey
- Department of Biology, Indiana University, Bloomington, IN 47405, USA.
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Sakai AK, Weller SG, Culley TM, Campbell DR, Dunbar-Wallis AK, Andres A. Sexual dimorphism and the genetic potential for evolution of sex allocation in the gynodioecious plant, Schiedea salicaria. J Evol Biol 2007; 21:18-29. [PMID: 18005115 DOI: 10.1111/j.1420-9101.2007.01439.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Sex allocation theory addresses how separate sexes can evolve from hermaphroditism but little is known about the genetic potential for shifts in sex allocation in flowering plants. We tested assumptions of this theory using the common currency of biomass and measurements of narrow-sense heritabilities and genetic correlations in Schiedea salicaria, a gynodioecious species under selection for greater differentiation of the sexes. Female (carpel) biomass showed heritable variation in both sexes. Male (stamen) biomass in hermaphrodites also had significant heritability, suggesting the potential for further evolution of dioecy. Significant positive genetic correlations between females and hermaphrodites in carpel mass may slow differentiation between the sexes. Within hermaphrodites, there were no negative genetic correlations between male and female biomass as assumed by models for the evolution of dioecy, suggesting that S. salicaria is capable of further changes in biomass allocation to male and female functions and evolution toward dioecy.
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Affiliation(s)
- A K Sakai
- Department of Ecology and Evolutionary Biology, University of California, Irvine, CA, USA
| | - S G Weller
- Department of Ecology and Evolutionary Biology, University of California, Irvine, CA, USA
| | - T M Culley
- Department of Ecology and Evolutionary Biology, University of California, Irvine, CA, USA
| | - D R Campbell
- Department of Ecology and Evolutionary Biology, University of California, Irvine, CA, USA
| | - A K Dunbar-Wallis
- Department of Ecology and Evolutionary Biology, University of California, Irvine, CA, USA
| | - A Andres
- Department of Ecology and Evolutionary Biology, University of California, Irvine, CA, USA
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Case AL, Ashman TL. An experimental test of the effects of resources and sex ratio on maternal fitness and phenotypic selection in gynodioecious Fragaria virginiana. Evolution 2007; 61:1900-11. [PMID: 17683432 DOI: 10.1111/j.1558-5646.2007.00148.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Resources, sex ratio, and seed production by hermaphrodites covary among natural populations of many gynodioecious plant species, such that they are functionally "more dioecious" as resources become more limiting. Strong correlations among these three factors confound our understanding of their relative roles in maintaining polymorphic sexual systems. We manipulated resource availability and sex ratio and measured their effects on relative fertility and phenotypic selection through the maternal fitness of females and hermaphrodites of Fragaria virginiana. Two results were particularly surprising. First, hermaphrodites showed little variability in fecundity across resource treatments and showed strong positive and context-dependent selection for fruit set. This suggests that variation in hermaphrodite seed production along resource gradients in nature may result from adaptation rather than plasticity. Second, although females increased their fecundity with higher resources, their fertility was unaffected by sex ratio, which is predicted to mediate pollen limitation of females in natural populations where they are common. Selection on petal size of females was also weak, indicating a minimal effect of pollinator attraction on variation in the fertility of female plants. Hence, we found no mechanistic explanation for the complete absence of high-resource high female populations in nature. Despite strong selection for increased fruit set of hermaphrodites, both the strength of selection and its contribution to the maintenance of gynodioecy are severely reduced under conditions where females have high relative fecundity (i.e., low resources and high-female sex ratios). High relative fertility plus high female frequency means that the evolution of phenotypic traits in hermaphrodites (i.e., response to selection via seed function) should be manifested through females because most hermaphrodites will have female mothers. Fruit set was never under strong selection in females; hence, selection to increase fruit set hermaphrodites will be less effective in maintaining their fruiting ability in natural populations with low resources and high female frequency. In sum, both sex ratio and resource availability influence trait evolution indirectly-through their effects on relative fertility of the sexes and patterns of selection. Sex ratio did not impose strong pollen limitation on females but did directly moderate the outcome of natural selection by biasing the maternal sex of the next generation. This direct effect of sex ratio on the manifestation of natural selection is expected to have far greater impact on the evolution of traits, such as seed-producing ability in hermaphrodites and the maintenance of sexual polymorphisms in nature, compared to indirect effects of sex ratio on relative fertility of the sexes.
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Affiliation(s)
- Andrea L Case
- Department of Biological Sciences, Kent State University, Kent, Ohio 44242, USA.
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