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Wang CH, Zou TT, Liu WQ, Wang XF. The influence of self-pollen deposition on female reproductive success in a self-incompatible plant, Akebia quinata. FRONTIERS IN PLANT SCIENCE 2022; 13:935217. [PMID: 36035715 PMCID: PMC9399832 DOI: 10.3389/fpls.2022.935217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Accepted: 07/11/2022] [Indexed: 06/15/2023]
Abstract
Geitonogamy is inevitable in hermaphrodite and monecious. Even for self-incompatible species, the negative effects of self-pollen are unavoidable when geitonogamous or self-mating occurs. However, the influence of self-pollen on consecutive development of flowers (e.g., fruiting and seeding) was seldom evaluated. Here, the self-incompatible monecious species, Akebia quinata, was used to estimate the influence of self-pollen deposition. We evaluated the extent of pollen limitation and geitonogamous mating under natural conditions by count of stigmatic pollen load and pollen tracking experiment. Hand pollination with different amount and combinations of self vs. cross pollen grains was applied to detect the response of fruit and seed set. The results showed that geitonogamy and pollen limitation occurred under natural conditions in A. quinata. Carpel numbers, ratio of self- and cross-pollen, and the interactive effect of ratio of self- and cross-pollen and total mixed pollen numbers, and not total pollen grain number, determined the effect of self-pollen on female reproductive success. The effect of self-pollen depended on its intensity. In general, the transfer of self-pollen significantly affected young fruit set. However, a little self-pollen together with cross-pollen did not reduce young fruit production. Although self-incompatible plants have evolved physiological mechanisms that reduce self-fertilization, our results provide new insights into the effects of self-pollen and the adaptive significance of self-incompatible monecious species.
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Affiliation(s)
- Chun-Hui Wang
- College of Life Sciences, Wuhan University, Wuhan, China
- Ecology and Environment Monitoring and Scientific Research Center, Yangtze Basin Ecology and Environment Administration, Ministry of Ecology and Environment of the People's Republic of China, Wuhan, China
| | - Ting-Ting Zou
- College of Life Sciences, Wuhan University, Wuhan, China
| | - Wei-Qi Liu
- College of Life Sciences, Wuhan University, Wuhan, China
| | - Xiao-Fan Wang
- College of Life Sciences, Wuhan University, Wuhan, China
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2
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Voillemot M, Rougemont Q, Roux C, Pannell JR. The divergence history of the perennial plant Linaria cavanillesii
confirms a recent loss of self-incompatibility. J Evol Biol 2017; 31:136-147. [DOI: 10.1111/jeb.13209] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2017] [Revised: 11/03/2017] [Accepted: 11/07/2017] [Indexed: 11/30/2022]
Affiliation(s)
- M. Voillemot
- Department of Ecology and Evolution; Biophore/Sorge; University of Lausanne; Lausanne Switzerland
| | - Q. Rougemont
- Institut de Biologie Intégrative et des Systèmes (IBIS); University of Laval; Québec City Québec Canada
| | - C. Roux
- Department of Ecology and Evolution; Biophore/Sorge; University of Lausanne; Lausanne Switzerland
- Unité Evo-Eco-Paléo (EEP) - UMR 8198; CNRS; Université de Lille Sciences et Technologies; Villeneuve d'Ascq Cedex France
| | - J. R. Pannell
- Department of Ecology and Evolution; Biophore/Sorge; University of Lausanne; Lausanne Switzerland
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3
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Ho EKH, Agrawal AF. Aging asexual lineages and the evolutionary maintenance of sex. Evolution 2017; 71:1865-1875. [PMID: 28444897 DOI: 10.1111/evo.13260] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Revised: 04/13/2017] [Accepted: 04/17/2017] [Indexed: 12/24/2022]
Abstract
Finite populations of asexual and highly selfing species suffer from a reduced efficacy of selection. Such populations are thought to decline in fitness over time due to accumulating slightly deleterious mutations or failing to adapt to changing conditions. These within-population processes that lead nonrecombining species to extinction may help maintain sex and outcrossing through species level selection. Although inefficient selection is proposed to elevate extinction rates over time, previous models of species selection for sex assumed constant diversification rates. For sex to persist, classic models require that asexual species diversify at rates lower than sexual species; the validity of this requirement is questionable, both conceptually and empirically. We extend past models by allowing asexual lineages to decline in diversification rates as they age, that is nonrecombining lineages "senesce" in diversification rates. At equilibrium, senescing diversification rates maintain sex even when asexual lineages, at young ages, diversify faster than their sexual progenitors. In such cases, the age distribution of asexual lineages contains a peak at intermediate values rather than showing the exponential decline predicted by the classic model. Coexistence requires only that the average rate of diversification in asexuals be lower than that of sexuals.
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Affiliation(s)
- Eddie K H Ho
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, M5S 3B2, Canada
| | - Aneil F Agrawal
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, M5S 3B2, Canada
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4
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Abu Awad D, Billiard S. The double edged sword: The demographic consequences of the evolution of self-fertilization. Evolution 2017; 71:1178-1190. [DOI: 10.1111/evo.13222] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2016] [Accepted: 02/26/2017] [Indexed: 01/27/2023]
Affiliation(s)
- Diala Abu Awad
- Univ. Lille, CNRS, UMR 8198 - Evo-Eco-Paleo; F-59000 Lille France
- INRA, UMR AGAP; 2 place Pierre Viala F-34060 Montpellier Cedex 1; France
| | - Sylvain Billiard
- Univ. Lille, CNRS, UMR 8198 - Evo-Eco-Paleo; F-59000 Lille France
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5
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Käfer J, Marais GAB, Pannell JR. On the rarity of dioecy in flowering plants. Mol Ecol 2017; 26:1225-1241. [PMID: 28101895 DOI: 10.1111/mec.14020] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Revised: 12/27/2016] [Accepted: 12/28/2016] [Indexed: 01/21/2023]
Abstract
Dioecy, the coexistence of separate male and female individuals in a population, is a rare but phylogenetically widespread sexual system in flowering plants. While research has concentrated on why and how dioecy evolves from hermaphroditism, the question of why dioecy is rare, despite repeated transitions to it, has received much less attention. Previous phylogenetic and theoretical studies have suggested that dioecy might be an evolutionary dead end. However, recent research indicates that the phylogenetic support for this hypothesis is attributable to a methodological bias and that there is no evidence for reduced diversification in dioecious angiosperms. The relative rarity of dioecy thus remains a puzzle. Here, we review evidence for the hypothesis that dioecy might be rare not because it is an evolutionary dead end, but rather because it easily reverts to hermaphroditism. We review what is known about transitions between hermaphroditism and dioecy, and conclude that there is an important need to consider more widely the possibility of transitions away from dioecy, both from an empirical and a theoretical point of view, and by combining tools from molecular evolution and insights from ecology.
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Affiliation(s)
- Jos Käfer
- Laboratoire de Biométrie et Biologie Evolutive, CNRS, UMR 5558, Université Lyon 1, Bât. Grégor Mendel 43, bd du 11 novembre 1918, 69622, Villeurbanne cedex, France
| | - Gabriel A B Marais
- Laboratoire de Biométrie et Biologie Evolutive, CNRS, UMR 5558, Université Lyon 1, Bât. Grégor Mendel 43, bd du 11 novembre 1918, 69622, Villeurbanne cedex, France
| | - John R Pannell
- Department of Ecology and Evolution, University of Lausanne, Biophore Building, 1015, Lausanne, Switzerland
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6
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Voillemot M, Pannell JR. Maintenance of mixed mating after the loss of self-incompatibility in a long-lived perennial herb. ANNALS OF BOTANY 2017; 119:177-190. [PMID: 27941096 PMCID: PMC5218368 DOI: 10.1093/aob/mcw203] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Revised: 06/23/2016] [Accepted: 07/19/2016] [Indexed: 05/09/2023]
Abstract
BACKGROUND AND AIMS Many hermaphroditic plants avoid self-fertilization by means of a molecular self-incompatibility (SI) system, a complex trait that is difficult to evolve but relatively easy to lose. Loss of SI is a prerequisite for an evolutionary transition from obligate outcrossing to self-fertilization, which may bring about rapid changes in the genetic diversity and structure of populations. Loss of SI is also often followed by the evolution of a 'selfing syndrome', with plants having small flowers, little nectar and few pollen grains per ovule. Here, we document the loss of SI in the long-lived Spanish toadflax Linaria cavanillesii, which has led to mixed mating rather than a transition to a high rate of selfing and in which an outcrossing syndrome has been maintained. METHODS We performed crosses within and among six populations of L. cavanillesii in the glasshouse, measured floral traits in a common-garden experiment, performed a pollen-limitation experiment in the field and conducted population genetic analyses using microsatellites markers. KEY RESULTS Controlled crosses revealed variation in SI from fully SI through intermediate SI to fully self-compatible (SC). Flowers of SC individuals showed no evidence of a selfing syndrome. Although the SC population of L. cavanillesii had lower within-population genetic diversity than SI populations, as expected, population differentiation among all populations was extreme and represents an FST outlier in the distribution for both selfing and outcrossing species of flowering plants. CONCLUSIONS Together, our results suggest that the transition to SC in L. cavanillesii has probably been very recent, and may have been aided by selection during or following a colonization bottleneck rather than in the absence of pollinators. We find little indication that the transition to SC has been driven by selection for reproductive assurance under conditions currently prevailing in natural populations.
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Affiliation(s)
- Marie Voillemot
- Department of Ecology and Evolution, Biophore Building, University of Lausanne, CH-1015 Lausanne, Switzerland
| | - John R Pannell
- Department of Ecology and Evolution, Biophore Building, University of Lausanne, CH-1015 Lausanne, Switzerland
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7
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Laenen B, Machac A, Gradstein SR, Shaw B, Patiño J, Désamoré A, Goffinet B, Cox CJ, Shaw AJ, Vanderpoorten A. Increased diversification rates follow shifts to bisexuality in liverworts. THE NEW PHYTOLOGIST 2016; 210:1121-1129. [PMID: 27074401 DOI: 10.1111/nph.13835] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Accepted: 12/01/2015] [Indexed: 06/05/2023]
Abstract
Shifts in sexual systems are one of the key drivers of species diversification. In contrast to angiosperms, unisexuality prevails in bryophytes. Here, we test the hypotheses that bisexuality evolved from an ancestral unisexual condition and is a key innovation in liverworts. We investigate whether shifts in sexual systems influence diversification using hidden state speciation and extinction analysis (HiSSE). This new method compares the effects of the variable of interest to the best-fitting latent variable, yielding robust and conservative tests. We find that the transitions in sexual systems are significantly biased toward unisexuality, even though bisexuality is coupled with increased diversification. Sexual systems are strongly conserved deep within the liverwort tree but become much more labile toward the present. Bisexuality appears to be a key innovation in liverworts. Its effects on diversification are presumably mediated by the interplay of high fertilization rates, massive spore production and long-distance dispersal, which may separately or together have facilitated liverwort speciation, suppressed their extinction, or both. Importantly, shifts in liverwort sexual systems have the opposite effect when compared to angiosperms, leading to contrasting diversification patterns between the two groups. The high prevalence of unisexuality among liverworts suggests, however, a strong selection for sexual dimorphism.
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Affiliation(s)
- Benjamin Laenen
- Department of Ecology, Environment and Plant Sciences, Science for Life Laboratory, Stockholm University, Stockholm, 10691, Sweden
- Department of Conservation Biology and Evolution, Institute of Botany, University of Liège, Liège, 4000, Belgium
| | - Antonin Machac
- Center for Macroecology, Evolution, and Climate, Natural History Museum of Denmark, Universitetsparken 15, DK 2100, Copenhagen, Denmark
- Department of Ecology, Charles University, Vinicna 7, Prague 2, 12844, Czech Republic
- Center for Theoretical Study, Charles University and Academy of Sciences of the Czech Republic, Jilska 1, Prague 1, 11000, Czech Republic
| | - S Robbert Gradstein
- Département Systématique et Evolution, Muséum National d'Histoire Naturelle, Paris, 75005, France
| | - Blanka Shaw
- Department of Biology, Duke University, Durham, NC, 27708, USA
| | - Jairo Patiño
- Department of Conservation Biology and Evolution, Institute of Botany, University of Liège, Liège, 4000, Belgium
| | - Aurélie Désamoré
- Department of Conservation Biology and Evolution, Institute of Botany, University of Liège, Liège, 4000, Belgium
- Department of Zoology, Naturhistoriska Riksmuseet, Stockholm, 10405, Sweden
| | - Bernard Goffinet
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, 06269, USA
| | - Cymon J Cox
- Centro de Ciências do Mar (CCMAR), Universidade do Algarve, Campus de Gambelas, Faro, 8005-139, Portugal
| | - A Jonathan Shaw
- Department of Biology, Duke University, Durham, NC, 27708, USA
| | - Alain Vanderpoorten
- Department of Conservation Biology and Evolution, Institute of Botany, University of Liège, Liège, 4000, Belgium
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8
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Limits to Adaptation in Partially Selfing Species. Genetics 2016; 203:959-74. [PMID: 27098913 DOI: 10.1534/genetics.116.188821] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 04/15/2016] [Indexed: 12/26/2022] Open
Abstract
In outcrossing populations, "Haldane's sieve" states that recessive beneficial alleles are less likely to fix than dominant ones, because they are less exposed to selection when rare. In contrast, selfing organisms are not subject to Haldane's sieve and are more likely to fix recessive types than outcrossers, as selfing rapidly creates homozygotes, increasing overall selection acting on mutations. However, longer homozygous tracts in selfers also reduce the ability of recombination to create new genotypes. It is unclear how these two effects influence overall adaptation rates in partially selfing organisms. Here, we calculate the fixation probability of beneficial alleles if there is an existing selective sweep in the population. We consider both the potential loss of the second beneficial mutation if it has a weaker advantage than the first one, and the possible replacement of the initial allele if the second mutant is fitter. Overall, loss of weaker adaptive alleles during a first selective sweep has a larger impact on preventing fixation of both mutations in highly selfing organisms. Furthermore, the presence of linked mutations has two opposing effects on Haldane's sieve. First, recessive mutants are disproportionally likely to be lost in outcrossers, so it is likelier that dominant mutations will fix. Second, with elevated rates of adaptive mutation, selective interference annuls the advantage in selfing organisms of not suffering from Haldane's sieve; outcrossing organisms are more able to fix weak beneficial mutations of any dominance value. Overall, weakened recombination effects can greatly limit adaptation in selfing organisms.
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9
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Castillo DM, Gibson AK, Moyle LC. Assortative mating and self-fertilization differ in their contributions to reinforcement, cascade speciation, and diversification. Curr Zool 2016; 62:169-181. [PMID: 29491904 PMCID: PMC5804227 DOI: 10.1093/cz/zow004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Accepted: 01/07/2016] [Indexed: 11/14/2022] Open
Abstract
Cascade speciation and reinforcement can evolve rapidly when traits are pleiotropic and act as both signal/cue in nonrandom mating. Here, we examine the contribution of two key traits-assortative mating and self-fertilization-to reinforcement and (by extension) cascade speciation. First, using a population genetic model of reinforcement we find that both assortative mating and self-fertilization can make independent contributions to increased reproductive isolation, consistent with reinforcement. Self-fertilization primarily evolves due to its 2-fold transmission advantage when inbreeding depression (d) is lower (d < 0.45) but evolves as a function of the cost of hybridization under higher inbreeding depression (0.45 < d < 0.48). When both traits can evolve simultaneously, increased self-fertilization often prohibits the evolution of assortative mating. We infer that, under specific conditions, mating system transitions are more likely to lead to increased reproductive isolation and initiate cascade speciation, than assortative mating. Based on the results of our simulations, we hypothesized that transitions to self-fertilization could contribute to clade-wide diversification if reinforcement or cascade speciation is common. We tested this hypothesis with comparative data from two different groups. Consistent with our hypothesis, there was a trend towards uniparental reproduction being associated with increased diversification rate in the Nematode phylum. For the plant genus Mimulus, however, self-fertilization was associated with reduced diversification. Reinforcement driving speciation via transitions to self-fertilization might be short lived or unsustainable across macroevolutionary scales in some systems (some plants), but not others (such as nematodes), potentially due to differences in susceptibility to inbreeding depression and/or the ability to transition between reproductive modes.
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Affiliation(s)
- Dean M. Castillo
- Department of Biology, 1001 East Third Street, Indiana University, Bloomington, IN 47405, USA
| | - Amanda K. Gibson
- Department of Biology, 1001 East Third Street, Indiana University, Bloomington, IN 47405, USA
| | - Leonie C. Moyle
- Department of Biology, 1001 East Third Street, Indiana University, Bloomington, IN 47405, USA
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10
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Ashkani J, Rees DJG. A Comprehensive Study of Molecular Evolution at the Self-Incompatibility Locus of Rosaceae. J Mol Evol 2015; 82:128-45. [PMID: 26714486 DOI: 10.1007/s00239-015-9726-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Accepted: 12/16/2015] [Indexed: 10/22/2022]
Abstract
The family Rosaceae includes a range of important fruit trees, most of which have the S-RNase-based self-incompatibility (SI). Several models have been developed to explain how pollen (SLF) and pistil (S-RNase) components of the S-locus interact. It was discovered in 2010 that additional SLF proteins are involved in pollen specificity, and a Collaborative Non-Self Recognition model has been proposed for SI in Solanaceae; however, the validity of such model remains to be elucidated for other species. The results of this study support the divergent evolution of the S-locus genes from two Rosaceae subfamilies, Prunoideae/Amygdaloideae and Maloideae, The difference identified in the selective pressures between the two lineages provides evidence for positive selection at specific sites in both the S-RNase and the SLF proteins. The evolutionary findings of this study support the role of multiple SLF proteins leading to a Collaborative Non-Self Recognition model for SI in the Maloideae. Furthermore, the identification of the sites responsible for SI specificity determination and the mapping of these sites onto the modelled tertiary structure of ancestor proteins provide useful information for rational functional redesign and protein engineering for the future engineering of new functional alleles providing increased diversity in the SI system in the Maloideae.
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Affiliation(s)
- Jahanshah Ashkani
- Biotechnology Department, University of the Western Cape, Private Bag X17, Bellville, 7535, South Africa. .,Biotechnology Platform, Agricultural Research Council, Private Bag X5, Onderstepoort, 0110, South Africa.
| | - D J G Rees
- Biotechnology Platform, Agricultural Research Council, Private Bag X5, Onderstepoort, 0110, South Africa
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11
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Salcedo A, Kalisz S, Wright SI. Limited genomic consequences of mixed mating in the recently derived sister species pair, Collinsia concolor and Collinsia parryi. J Evol Biol 2014; 27:1400-12. [PMID: 24796997 DOI: 10.1111/jeb.12384] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Revised: 03/07/2014] [Accepted: 03/12/2014] [Indexed: 11/30/2022]
Abstract
Highly selfing species often show reduced effective population sizes and reduced selection efficacy. Whether mixed mating species, which produce both self and outcross progeny, show similar patterns of diversity and selection remains less clear. Examination of patterns of molecular evolution and levels of diversity in species with mixed mating systems can be particularly useful for investigating the relative importance of linked selection and demographic effects on diversity and the efficacy of selection, as the effects of linked selection should be minimal in mixed mating populations, although severe bottlenecks tied to founder events could still be frequent. To begin to address this gap, we assembled and analysed the transcriptomes of individuals from a recently diverged mixed mating sister species pair in the self-compatible genus, Collinsia. The de novo assembly of 52 and 37 Mbp C. concolor and C. parryi transcriptomes resulted in ~40 000 and ~55 000 contigs, respectively, both with an average contig size ~945. We observed a high ratio of shared polymorphisms to fixed differences in the species pair and minimal differences between species in the ratio of synonymous to replacement substitutions or codon usage bias implying comparable effective population sizes throughout species divergence. Our results suggest that differences in effective population size and selection efficacy in mixed mating taxa shortly after their divergence may be minimal and are likely influenced by fluctuating mating systems and population sizes.
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Affiliation(s)
- A Salcedo
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada
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12
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Abstract
Self-fertilization is generally seen to be disadvantageous in the long term. It increases genetic drift, which subsequently reduces polymorphism and the efficiency of selection, which also challenges adaptation. However, high selfing rates can increase the fixation probability of recessive beneficial mutations, but existing theory has generally not accounted for the effect of linked sites. Here, we analyze a model for the fixation probability of deleterious mutants that hitchhike with selective sweeps in diploid, partially selfing populations. Approximate analytical solutions show that, conditional on the sweep not being lost by drift, higher inbreeding rates increase the fixation probability of the deleterious allele, due to the resulting reduction in polymorphism and effective recombination. When extending the analysis to consider a distribution of deleterious alleles, as well as the average fitness increase after a sweep, we find that beneficial alleles generally need to be more recessive than the previously assumed dominance threshold (h < 1/2) for selfing to be beneficial from one-locus theory. Our results highlight that recombination aiding the efficiency of selection on multiple loci amplifies the fitness benefits of outcrossing over selfing, compared to results obtained from one-locus theory. This effect additionally increases the parameter range under which obligate outcrossing is beneficial over partial selfing.
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13
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Särkinen T, Bohs L, Olmstead RG, Knapp S. A phylogenetic framework for evolutionary study of the nightshades (Solanaceae): a dated 1000-tip tree. BMC Evol Biol 2013; 13:214. [PMID: 24283922 PMCID: PMC3850475 DOI: 10.1186/1471-2148-13-214] [Citation(s) in RCA: 273] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Accepted: 09/16/2013] [Indexed: 01/02/2023] Open
Abstract
BACKGROUND The Solanaceae is a plant family of great economic importance. Despite a wealth of phylogenetic work on individual clades and a deep knowledge of particular cultivated species such as tomato and potato, a robust evolutionary framework with a dated molecular phylogeny for the family is still lacking. Here we investigate molecular divergence times for Solanaceae using a densely-sampled species-level phylogeny. We also review the fossil record of the family to derive robust calibration points, and estimate a chronogram using an uncorrelated relaxed molecular clock. RESULTS Our densely-sampled phylogeny shows strong support for all previously identified clades of Solanaceae and strongly supported relationships between the major clades, particularly within Solanum. The Tomato clade is shown to be sister to section Petota, and the Regmandra clade is the first branching member of the Potato clade. The minimum age estimates for major splits within the family provided here correspond well with results from previous studies, indicating splits between tomato and potato around 8 Million years ago (Ma) with a 95% highest posterior density (HPD) 7-10 Ma, Solanum and Capsicum c. 19 Ma (95% HPD 17-21), and Solanum and Nicotiana c. 24 Ma (95% HPD 23-26). CONCLUSIONS Our large time-calibrated phylogeny provides a significant step towards completing a fully sampled species-level phylogeny for Solanaceae, and provides age estimates for the whole family. The chronogram now includes 40% of known species and all but two monotypic genera, and is one of the best sampled angiosperm family phylogenies both in terms of taxon sampling and resolution published thus far. The increased resolution in the chronogram combined with the large increase in species sampling will provide much needed data for the examination of many biological questions using Solanaceae as a model system.
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Affiliation(s)
- Tiina Särkinen
- Department of Life Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK
- Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh EH3 5LR, UK
| | - Lynn Bohs
- Department of Biology, University of Utah, 257 S 1400 E, Salt Lake City, UT 84112, USA
| | | | - Sandra Knapp
- Department of Life Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK
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14
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Wright SI, Kalisz S, Slotte T. Evolutionary consequences of self-fertilization in plants. Proc Biol Sci 2013; 280:20130133. [PMID: 23595268 PMCID: PMC3652455 DOI: 10.1098/rspb.2013.0133] [Citation(s) in RCA: 238] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Accepted: 03/22/2013] [Indexed: 01/17/2023] Open
Abstract
The transition from outcrossing to self-fertilization is one of the most common evolutionary changes in plants, yet only about 10-15% of flowering plants are predominantly selfing. To explain this phenomenon, Stebbins proposed that selfing may be an 'evolutionary dead end'. According to this hypothesis, transitions from outcrossing to selfing are irreversible, and selfing lineages suffer from an increased risk of extinction owing to a reduced potential for adaptation. Thus, although selfing can be advantageous in the short term, selfing lineages may be mostly short-lived owing to higher extinction rates. Here, we review recent results relevant to the 'dead-end hypothesis' of selfing and the maintenance of outcrossing over longer evolutionary time periods. In particular, we highlight recent results regarding diversification rates in self-incompatible and self-compatible taxa, and review evidence regarding the accumulation of deleterious mutations in selfing lineages. We conclude that while some aspects of the hypothesis of selfing as a dead end are supported by theory and empirical results, the evolutionary and ecological mechanisms remain unclear. We highlight the need for more studies on the effects of quantitative changes in outcrossing rates and on the potential for adaptation, particularly in selfing plants. In addition, there is growing evidence that transitions to selfing may themselves be drivers of speciation, and future studies of diversification and speciation should investigate this further.
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Affiliation(s)
- Stephen I. Wright
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Canada
| | - Susan Kalisz
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
| | - Tanja Slotte
- Department of Evolutionary Biology, Evolutionary Biology Centre (EBC), Uppsala University, Uppsala, Sweden
- Science for Life Laboratory, Uppsala University, Uppsala, Sweden
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15
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Ferrer MM, Good SV. Self-sterility in flowering plants: preventing self-fertilization increases family diversification rates. ANNALS OF BOTANY 2012; 110:535-53. [PMID: 22684683 PMCID: PMC3400452 DOI: 10.1093/aob/mcs124] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
BACKGROUND AND SCOPE New data are presented on the distribution and frequency of self-sterility (SS) - predominantly pre-zygotic self-incompatibility (SI) systems - in flowering plants and the hypothesis is tested that families with self-sterile taxa have higher net diversification rates (DRs) than those with exclusively self-compatible taxa using both absolute and relative rate tests. KEY RESULTS Three major forms of SI systems (where pollen is rejected at the stigmatic, stylar or ovarian interface) are found to occur in the oldest families of flowering plants, with times of divergence >100 million years before the present (mybp), while post-fertilization SS and heterostyly appear in families with crown ages of 81 and 87 mybp, respectively. It is also founnd that many (22) angiosperm families exhibit >1 SI phenotype and that the distribution of different types of SS does not show strong phylogenetic clustering, collectively suggesting that SS and SI systems have evolved repeatedly de novo in angiosperm history. Families bearing self-sterile taxa have higher absolute DRs using all available calibrations of the angiosperm tree, and this affect is caused mostly by the high DR of families with homomorphic SI systems (in particular stigmatic SI) or those in which multiple SS/SI phenotypes have been observed (polymorphic). Lastly, using sister comparisons, it is further demonstrated that in 29 of 38 sister pairs (including 95 families), the self-sterile sister group had higher species richness and DR than its self-compatible sister based on either the total number of taxa in the clade with SS or only the estimated fraction to harbour SS based on literature surveys. CONCLUSIONS Collectively, these analyses point to the importance of SS, particularly pre-zygotic SI in the evolution of flowering plants.
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Affiliation(s)
- Miriam M Ferrer
- Universidad Autónoma de Yucatán, Departamento de Ecología Tropical, Km. 15·5 carretera Mérida - Xmatkuil, Mérida, Yucatán, 97000, México.
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Guo YL, Zhao X, Lanz C, Weigel D. Evolution of the S-locus region in Arabidopsis relatives. PLANT PHYSIOLOGY 2011; 157:937-46. [PMID: 21810962 PMCID: PMC3192562 DOI: 10.1104/pp.111.174912] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2011] [Accepted: 08/01/2011] [Indexed: 05/21/2023]
Abstract
The S locus, a single polymorphic locus, is responsible for self-incompatibility (SI) in the Brassicaceae family and many related plant families. Despite its importance, our knowledge of S-locus evolution is largely restricted to the causal genes encoding the S-locus receptor kinase (SRK) receptor and S-locus cysteine-rich protein (SCR) ligand of the SI system. Here, we present high-quality sequences of the genomic region of six S-locus haplotypes: Arabidopsis (Arabidopsis thaliana; one haplotype), Arabidopsis lyrata (four haplotypes), and Capsella rubella (one haplotype). We compared these with reference S-locus haplotypes of the self-compatible Arabidopsis and its SI congener A. lyrata. We subsequently reconstructed the likely genomic organization of the S locus in the most recent common ancestor of Arabidopsis and Capsella. As previously reported, the two SI-determining genes, SCR and SRK, showed a pattern of coevolution. In addition, consistent with previous studies, we found that duplication, gene conversion, and positive selection have been important factors in the evolution of these two genes and appear to contribute to the generation of new recognition specificities. Intriguingly, the inactive pseudo-S-locus haplotype in the self-compatible species C. rubella is likely to be an old S-locus haplotype that only very recently became fixed when C. rubella split off from its SI ancestor, Capsella grandiflora.
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Affiliation(s)
- Ya-Long Guo
- Department of Molecular Biology, Max Planck Institute for Developmental Biology, 72076 Tuebingen, Germany.
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Zhang X, Wang L, Yuan Y, Tian D, Yang S. Rapid copy number expansion and recent recruitment of domains in S-receptor kinase-like genes contribute to the origin of self-incompatibility. FEBS J 2011; 278:4323-37. [DOI: 10.1111/j.1742-4658.2011.08349.x] [Citation(s) in RCA: 14] [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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Busch JW, Joly S, Schoen DJ. Demographic signatures accompanying the evolution of selfing in Leavenworthia alabamica. Mol Biol Evol 2011; 28:1717-29. [PMID: 21199892 DOI: 10.1093/molbev/msq352] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The evolution of selfing from outcrossing is a common transition, yet little is known about the mutations and selective factors that promote this shift. In the mustard family, single-locus self-incompatibility (SI) enforces outcrossing. In this study, we test whether mutations causing self-compatibility (SC) are linked to the self-incompatibility locus (S-locus) in Leavenworthia alabamica, a species where two selfing races (a2 and a4) co-occur with outcrossing populations. We also infer the ecological circumstances associated with origins of selfing using molecular sequence data. Genealogical reconstruction of the Lal2 locus, the putative ortholog of the SRK locus, showed that both selfing races are fixed for one of two different S-linked Lal2 sequences, whereas outcrossing populations harbor many S-alleles. Hybrid crosses demonstrated that S-linked mutations cause SC in each selfing race. These results strongly suggest two origins of selfing in this species, a result supported by population admixture analysis of 16 microsatellite loci and by a population tree built from eight nuclear loci. One selfing race (a4) shows signs of a severe population bottleneck, suggesting that reproductive assurance might have caused the evolution of selfing in this case. In contrast, the population size of race a2 cannot be distinguished from that of outcrossing populations after correcting for differences in selfing rates. Coalescent-based analyses suggest a relatively old origin of selfing in the a4 race (∼150 ka ago), whereas selfing evolved recently in the a2 race (∼12-48 ka ago). These results imply that S-locus mutations have triggered two recent shifts to selfing in L. alabamica, but that these transitions are not always associated with a severe population bottleneck, suggesting that factors other than reproductive assurance may play a role in its evolution.
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Affiliation(s)
- Jeremiah W Busch
- School of Biological Sciences and The Center for Reproductive Biology, Washington State University, WA, USA.
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