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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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2
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Yuan S, Barrett SCH, Li C, Li X, Xie K, Zhang D. Genetics of distyly and homostyly in a self-compatible Primula. Heredity (Edinb) 2018; 122:110-119. [PMID: 29728676 DOI: 10.1038/s41437-018-0081-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2017] [Revised: 03/16/2018] [Accepted: 03/17/2018] [Indexed: 12/23/2022] Open
Abstract
The transition from outcrossing to selfing through the breakdown of distyly to homostyly has occurred repeatedly among families of flowering plants. Homostyles can originate by major gene changes at the S-locus linkage group, or by unlinked polygenic modifiers. Here, we investigate the inheritance of distyly and homostyly in Primula oreodoxa, a subalpine herb endemic to Sichuan, China. Controlled self- and cross-pollinations confirmed that P. oreodoxa unlike most heterostylous species is fully self-compatible. Segregation patterns indicated that the inheritance of distyly is governed by a single Mendelian locus with the short-styled morph carrying at least one dominant S-allele (S-) and long-styled plants homozygous recessive (ss). Crossing data were consistent with a model in which homostyly results from genetic changes at the distylous linkage group, with the homostylous allele (Sh) dominant to the long-styled allele (s), but recessive to the short-styled allele (S). Progeny tests of open-pollinated seed families revealed high rates of intermorph mating in the L-morph but considerable selfing and possibly intramorph mating in the S-morph and in homostyles. S-morph plants homozygous at the S-locus (SS) occurred in several populations but may experience viability selection. The crossing data from distylous and homostylous plants are consistent with either recombination at the S-locus governing distyly, or mutation at gene(s) controlling sex-organ height; both models predict the same patterns of segregation. Recent studies on the molecular genetics of distyly in Primula demonstrating the hemizygous nature of genes at the S-locus make it more likely that homostyles have resulted from mutation rather than recombination.
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Affiliation(s)
- Shuai Yuan
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, 510650, China.,University of Chinese Academy of Sciences, Beijing, 10049, China
| | - Spencer C H Barrett
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks St., Toronto, Ontario, M5S 3B2, Canada
| | - Cehong Li
- Biological Resources Research Station at E'mei Mountain, Sichuan, Leshan, 614201, China
| | - Xiaojie Li
- Biological Resources Research Station at E'mei Mountain, Sichuan, Leshan, 614201, China
| | - Kongping Xie
- Biological Resources Research Station at E'mei Mountain, Sichuan, Leshan, 614201, China
| | - Dianxiang Zhang
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, 510650, China.
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3
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Husband BC, Barrett SCH. EFFECTIVE POPULATION SIZE AND GENETIC DRIFT IN TRISTYLOUSEICHHORNIA PANICULATA(PONTEDERIACEAE). Evolution 2017; 46:1875-1890. [DOI: 10.1111/j.1558-5646.1992.tb01175.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/1991] [Accepted: 02/22/1992] [Indexed: 10/19/2022]
Affiliation(s)
- Brian C. Husband
- Department of Botany; University of Toronto; Toronto Ontario M5S 3B2 Canada
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Kohn JR, Barrett SCH. EXPERIMENTAL STUDIES ON THE FUNCTIONAL SIGNIFICANCE OF HETEROSTYLY. Evolution 2017; 46:43-55. [PMID: 28564966 DOI: 10.1111/j.1558-5646.1992.tb01983.x] [Citation(s) in RCA: 77] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/1990] [Accepted: 06/27/1991] [Indexed: 11/27/2022]
Abstract
Heterostyly has been viewed as both an antiselfing device and a mechanism that increases the proficiency of pollen transfer between plants. We used experimental manipulation of the morph structure of garden populations of self-compatible, tristylous Eichhornia paniculata to investigate the function of floral polymorphism. Outcrossing rates (t), levels of intermorph mating (d), and morph-specific male and female reproductive success were compared in replicate trimorphic and monomorphic populations. In trimorphic populations, t and d averaged 0.81 (2 SE = 0.03) and 0.77 (2 SE = 0.03) respectively, with no difference in either parameter among morphs. Ninety-five percent of outcrossed seeds were therefore the result of intermorph fertilizations. Male reproductive success of the long-styled morph was low, especially in comparison with plants of the short-styled morph. Outcrossing rates for each morph were higher in trimorphic than monomorphic populations where t averaged 0.71 (2 SE = 0.01), 0.30 (2 SE = 0.04) and 0.43 (2 SE = 0.1) for the long-, mid-, and short-styled morphs, respectively. Seed set was lower in monomorphic populations, particularly those composed of the L morph, reflecting reduced pollen deposition. Floral polymorphism therefore increased both outcrossing rate and fecundity but the magnitude of the differences varied among morphs. If the ancestral condition in heterostylous groups resembled the L morph, as has been suggested, data from this study suggests that the selective basis for the establishment of floral polymorphism could have been increased pollen transfer rather than higher levels of outcrossing.
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Affiliation(s)
- Joshua R Kohn
- Department of Botany, University of Toronto, Toronto, ON, M5S 3B2, CANADA
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5
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Eckert CG, Manicacci D, Barrett SCH. GENETIC DRIFT AND FOUNDER EFFECT IN NATIVE VERSUS INTRODUCED POPULATIONS OF AN INVADING PLANT,LYTHRUM SALICARIA(LYTHRACEAE). Evolution 2017; 50:1512-1519. [DOI: 10.1111/j.1558-5646.1996.tb03924.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/1995] [Accepted: 08/08/1995] [Indexed: 11/26/2022]
Affiliation(s)
| | - Domenica Manicacci
- Centre d'Ecologie Fonctionelle et Evolutive; Centre Nationale de la Recherche Scientifique (CNRS); BP 5051 34 033 Montpellier France
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6
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Glover DE, Barrett SCH. VARIATION IN THE MATING SYSTEM OF EICHHORNIA PANICULATA (SPRENG.) SOLMS. (PONTEDERIACEAE). Evolution 2017; 40:1122-1131. [PMID: 28563501 DOI: 10.1111/j.1558-5646.1986.tb05738.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/1985] [Accepted: 07/08/1986] [Indexed: 11/28/2022]
Abstract
A multilocus procedure was used to estimate outcrossing rates from allozyme data in nine populations of Eichhornia paniculata from NE Brazil and Jamaica. The populations were chosen to represent stages in a proposed model of the evolutionary breakdown of tristyly to semi-homostyly; they differed in morph structure (trimorphic, dimorphic, or monomorphic) and floral traits likely to influence the mating system. The interpopulation range in outcrossing rate, t, was 0.96-0.29. Two additional populations from Jamaica, composed exclusively of self-pollinating, semi-homostylous, mid-styled plants, were invariant at 21 isozyme loci, precluding estimates of outcrossing frequency. Trimorphic populations from Brazil had uniformly high outcrossing rates of 0.96-0.88. Values for the floral morphs within populations were not significantly different. A controlled pollination experiment, comparing the competitive ability of self and cross pollen using the Got-3 marker locus, provided evidence that the maintenance of high outcrossing rates in trimorphic populations results from the prepotency of cross pollen and/or the selective abortion of selfed zygotes. Morph-dependent variation in t was detected within a dimorphic population with the L morph outcrossing with a frequency of 0.76 in comparison with 0.36 in the M morph. The difference in the mating system of floral morphs results from modifications in position of short-level stamens in flowers of the M morph resulting in automatic self-pollination. The occurrence of E. paniculata populations composed exclusively of self-pollinating, mid-styled variants is thought to be associated with the spread of genes modifying stamen position. The high level of self-fertilization demonstrated in the M morph would allow automatic selection of these genes, augmented by fertility assurance in the absence of specialized pollinators.
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Affiliation(s)
- Deborah E Glover
- Department of Botany, University of Toronto, Toronto, Ontario, M5S 1A1, Canada
| | - Spencer C H Barrett
- Department of Botany, University of Toronto, Toronto, Ontario, M5S 1A1, Canada
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Campbell DR, Waser NM, Price MV. INDIRECT SELECTION OF STIGMA POSITION IN
IPOMOPSIS AGGREGATA
VIA A GENETICALLY CORRELATED TRAIT. Evolution 2017; 48:55-68. [DOI: 10.1111/j.1558-5646.1994.tb01294.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/1992] [Accepted: 06/09/1993] [Indexed: 11/30/2022]
Affiliation(s)
- Diane R. Campbell
- Department of Ecology and Evolutionary Biology University of California Irvine California 92717
- Rocky Mountain Biological Laboratory Crested Butte Colorado 81224
| | - Nickolas M. Waser
- Department of Biology University of California Riverside California 92521
- Rocky Mountain Biological Laboratory Crested Butte Colorado 81224
| | - Mary V. Price
- Department of Biology University of California Riverside California 92521
- Rocky Mountain Biological Laboratory Crested Butte Colorado 81224
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Barrett SCH, Morgan MT, Husband BC. THE DISSOLUTION OF A COMPLEX GENETIC POLYMORPHISM: THE EVOLUTION OF SELF-FERTILIZATION IN TRISTYLOUS EICHHORNIA PANICULATA
(PONTEDERIACEAE). Evolution 2017; 43:1398-1416. [DOI: 10.1111/j.1558-5646.1989.tb02591.x] [Citation(s) in RCA: 117] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/1988] [Accepted: 05/31/1989] [Indexed: 10/19/2022]
Affiliation(s)
| | - Martin T. Morgan
- Department of Botany; University of Toronto; Toronto ON M5S 3B2 CANADA
| | - Brian C. Husband
- Department of Botany; University of Toronto; Toronto ON M5S 3B2 CANADA
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9
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Cruzan MB, Barrett SCH. CONTRIBUTION OF CRYPTIC INCOMPATIBILITY TO THE MATING SYSTEM OFEICHHORNIA PANICULA TA(PONTEDERIACEAE). Evolution 2017; 47:925-934. [DOI: 10.1111/j.1558-5646.1993.tb01245.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/1991] [Accepted: 11/02/1992] [Indexed: 11/30/2022]
Affiliation(s)
- Mitchell B. Cruzan
- Department of Botany; University of Toronto; Toronto Ontario M5S 3B2 Canada
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10
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Eckert CG, Barrett SCH. STOCHASTIC LOSS OF STYLE MORPHS FROM POPULATIONS OF TRISTYLOUSLYTHRUM SALICARIAANDDECODON VERTICILLATUS(LYTHRACEAE). Evolution 2017; 46:1014-1029. [PMID: 28564411 DOI: 10.1111/j.1558-5646.1992.tb00616.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/1991] [Accepted: 12/13/1991] [Indexed: 11/30/2022]
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Arunkumar R, Wang W, Wright SI, Barrett SCH. The genetic architecture of tristyly and its breakdown to self-fertilization. Mol Ecol 2016; 26:752-765. [DOI: 10.1111/mec.13946] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2016] [Revised: 11/02/2016] [Accepted: 11/07/2016] [Indexed: 11/29/2022]
Affiliation(s)
- Ramesh Arunkumar
- Department of Ecology and Evolutionary Biology; University of Toronto; 25 Willcocks Street Toronto Ontario Canada M5S 3B2
| | - Wei Wang
- Department of Ecology and Evolutionary Biology; University of Toronto; 25 Willcocks Street Toronto Ontario Canada M5S 3B2
| | - Stephen I. Wright
- Department of Ecology and Evolutionary Biology; University of Toronto; 25 Willcocks Street Toronto Ontario Canada M5S 3B2
| | - Spencer C. H. Barrett
- Department of Ecology and Evolutionary Biology; University of Toronto; 25 Willcocks Street Toronto Ontario Canada M5S 3B2
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12
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Costa J, Castro S, Loureiro J, Barrett SCH. Variation in style morph frequencies in tristylous Lythrum salicaria in the Iberian Peninsula: the role of geographical and demographic factors. ANNALS OF BOTANY 2016; 117:331-40. [PMID: 26658100 PMCID: PMC4724046 DOI: 10.1093/aob/mcv173] [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: 08/04/2015] [Revised: 09/01/2015] [Accepted: 10/05/2015] [Indexed: 06/05/2023]
Abstract
BACKGROUND AND AIMS The balance between stochastic forces and negative frequency-dependent selection largely determines style morph frequencies in heterostylous populations. Investigation of morph frequencies at geographical range limits can provide insights into the forces maintaining the floral polymorphism, and the factors causing biased morph ratios. Here, we investigate style morph frequencies in populations at the south-western European range limit of tristylous Lythrum salicaria, to explore the role of demographic and geographical factors influencing morph ratios in its native range. METHODS We measured morph composition and evenness, and the size of 96 populations, along a north to south latitudinal transect from Galicia to Andalucia, Iberian Peninsula, traversing a steep climatic gradient. To examine the potential influence of morph-specific fitness components on morph ratios, we examined reproductive traits in 19 populations. KEY RESULTS Most populations of L. salicaria were trimorphic (94·79 %), the majority exhibiting 1 : 1 : 1 morph ratios (68·75 %). Populations with biased morph ratios had a deficiency of the short-styled morph. Population size and morph evenness were positively associated with latitude, with smaller populations and those with less even morph ratios occurring towards the south. Greater variance in morph evenness was evident at the southern range margin. There were no consistent differences in components of reproductive fitness among style morphs, but southern populations produced less fruit and seed than more northerly populations. CONCLUSIONS Our results demonstrate the influence of finite population size on morph frequencies in L. salicaria. However, they also illustrate the resilience of Iberian populations to the factors causing deviations from isoplethy and morph loss, especially at the southern range limit where populations are smaller. The maintenance of tristyly in small populations of L. salicaria may be aided by the genetic connectivity of populations in agricultural landscapes resulting from gene flow through pollen and seed dispersal.
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Affiliation(s)
- Joana Costa
- Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal and
| | - Sílvia Castro
- Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal and
| | - João Loureiro
- Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal and
| | - Spencer C H Barrett
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario, Canada M5S 3B2
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Zhou W, Barrett SCH, Wang H, Li DZ. Reciprocal herkogamy promotes disassortative mating in a distylous species with intramorph compatibility. THE NEW PHYTOLOGIST 2015; 206:1503-1512. [PMID: 25664897 DOI: 10.1111/nph.13326] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Accepted: 01/11/2015] [Indexed: 06/04/2023]
Abstract
Mating patterns in heterostylous species with intramorph compatibility have the potential to deviate from symmetrical disassortative mating owing to ecological and reproductive factors influencing pollen dispersal. Here, we investigate potential and realized patterns of mating in distylous Luculia pinceana (Rubiaceae), a species with intramorph compatibility. Our analysis provides an opportunity to test Darwin's hypothesis that reciprocal herkogamy promotes disassortative pollen transfer. We combined measurements of sex-organ reciprocity and pollen production to predict potential pollen transfer and mating patterns in a population from SW China. Marker-based paternity analysis was then used to estimate realized patterns of disassortative and assortative mating at the individual and floral morph levels. Both potential and realized mating patterns indicated a significant component of disassortative mating, satisfying theoretical conditions for the maintenance of floral dimorphism. Levels of assortative mating (37.7%) were significantly lower than disassortative mating (62.3%), but numerous offspring resulting from intramorph mating were detected in the majority of maternal seed families in both floral morphs. Our results provide empirical support for Darwin's cross-promotion hypothesis on the function of reciprocal herkogamy, but indicate that in most heterostylous species strong diallelic incompatibility may be a general requirement for complete disassortative mating.
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Affiliation(s)
- Wei Zhou
- Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, 132 Lanhei Road, Kunming, Yunnan, 650201, China
- Plant Germplasm and Genomics Center, Germplasm Bank of Wild Species, Kunming Institute of Botany, Chinese Academy of Sciences, 132 Lanhei Road, Kunming, Yunnan, 650201, China
| | - Spencer C H Barrett
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, M5S 3B2, Canada
| | - Hong Wang
- Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, 132 Lanhei Road, Kunming, Yunnan, 650201, China
| | - De-Zhu Li
- Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, 132 Lanhei Road, Kunming, Yunnan, 650201, China
- Plant Germplasm and Genomics Center, Germplasm Bank of Wild Species, Kunming Institute of Botany, Chinese Academy of Sciences, 132 Lanhei Road, Kunming, Yunnan, 650201, China
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Costa J, Ferrero V, Loureiro J, Castro M, Navarro L, Castro S. Sexual reproduction of the pentaploid, short-styled Oxalis pes-caprae allows the production of viable offspring. PLANT BIOLOGY (STUTTGART, GERMANY) 2014; 16:208-14. [PMID: 23594049 DOI: 10.1111/plb.12010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Accepted: 12/31/2012] [Indexed: 05/13/2023]
Abstract
Reproduction is a key factor for the successful establishment and spread of introduced species. Oxalis pes-caprae is a tristylous species with a self- and morph-incompatibility sexual system that, in the invaded range of the western Mediterranean Basin, has been found to reproduce asexually because only the pentaploid, short-styled morph (5x S-morph) was introduced. The objective of this study was to test the ability of the 5x S-morph of O. pes-caprae to produce viable offspring in the absence of compatible mates, exploring the hypothesis that new morphs could have emerged by sexual reproduction events of the initially introduced morph. Pollen germination, pollen tube development, fruit and seed production, seed germination and offspring ploidy levels were analysed after controlled hand-pollinations to assess self- and morph-incompatibility and production of viable gametes by the 5x S-morph. The self-incompatibility system is still operating, but a partial breakdown in the morph-incompatibility system combined with the production of viable gametes was observed, allowing sexual reproduction of the 5x S-morph in the invaded range. The ability of the 5x S-morph to reproduce sexually may have major consequences for the dynamics of invasive populations of O. pes-caprae and could be one of the factors involved in the occurrence of new floral morphs in this invaded range.
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Affiliation(s)
- J Costa
- Department of Life Sciences, Centre for Functional Ecology (CFE), University of Coimbra, Coimbra, Portugal
| | - V Ferrero
- Department of Life Sciences, Centre for Functional Ecology (CFE), University of Coimbra, Coimbra, Portugal
- Department of Plant Biology, Faculty of Science, University of Vigo, Vigo, Spain
| | - J Loureiro
- Department of Life Sciences, Centre for Functional Ecology (CFE), University of Coimbra, Coimbra, Portugal
| | - M Castro
- Department of Life Sciences, Centre for Functional Ecology (CFE), University of Coimbra, Coimbra, Portugal
| | - L Navarro
- Department of Plant Biology, Faculty of Science, University of Vigo, Vigo, Spain
| | - S Castro
- Department of Life Sciences, Centre for Functional Ecology (CFE), University of Coimbra, Coimbra, Portugal
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Winn AA, Elle E, Kalisz S, Cheptou PO, Eckert CG, Goodwillie C, Johnston MO, Moeller DA, Ree RH, Sargent RD, Vallejo-Marín M. Analysis of inbreeding depression in mixed-mating plants provides evidence for selective interference and stable mixed mating. Evolution 2011; 65:3339-59. [PMID: 22133210 DOI: 10.1111/j.1558-5646.2011.01462.x] [Citation(s) in RCA: 120] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Hermaphroditic individuals can produce both selfed and outcrossed progeny, termed mixed mating. General theory predicts that mixed-mating populations should evolve quickly toward high rates of selfing, driven by rapid purging of genetic load and loss of inbreeding depression (ID), but the substantial number of mixed-mating species observed in nature calls this prediction into question. Lower average ID reported for selfing than for outcrossing populations is consistent with purging and suggests that mixed-mating taxa in evolutionary transition will have intermediate ID. We compared the magnitude of ID from published estimates for highly selfing (r > 0.8), mixed-mating (0.2 ≤ r ≥ 0.8), and highly outcrossing (r < 0.2) plant populations across 58 species. We found that mixed-mating and outcrossing taxa have equally high average lifetime ID (δ= 0.58 and 0.54, respectively) and similar ID at each of four life-cycle stages. These results are not consistent with evolution toward selfing in most mixed-mating taxa. We suggest that prevention of purging by selective interference could explain stable mixed mating in many natural populations. We identify critical gaps in the empirical data on ID and outline key approaches to filling them.
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Affiliation(s)
- Alice A Winn
- Department of Biological Science, Florida State University, Tallahassee, Florida 32306-4295, USA.
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Asymmetrical mating patterns and the evolution of biased style-morph ratios in a tristylous daffodil. Genet Res (Camb) 2008; 90:3-15. [DOI: 10.1017/s0016672307008956] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
SummaryNon-random mating in plant populations can be influenced by numerous reproductive and demographic factors, including floral morphology and inter-plant distance. Here, we investigate patterns of outcrossed mating through male function inNarcissus triandrus, a tristylous, bee-pollinated wild daffodil from the Iberian Peninsula, to test pollen transfer models which predict that floral morphology promotes asymmetrical mating and biased morph ratios. Unlike other tristylous species,N. triandrushas an incompatibility system that permits intra-morph mating and long-level rather than mid-level stamens in the L-morph. Incomplete sex-organ reciprocity should result in significant intra-morph mating in the L-morph. We measured mating patterns in two L-biased populations – dimorphic (two style morphs) and trimorphic (three style morphs) – using multilocus genotyping and maximum-likelihood-based paternity analysis. We also examined the spatial distribution of style morphs and neutral markers to investigate the potential consequence of spatially restricted mating on morph ratios. As predicted, we detected significant amounts of intra-morph mating in the L-morph in both populations. Pollen transfer coefficients generally supported predictions based on the Darwinian hypothesis that anthers and stigmas of equivalent level promote pollinator-mediated cross-pollination in heterostylous populations. There was evidence of significant spatial aggregation of both style morphs and neutral markers in populations ofN. triandrus, probably as a result of restricted pollen and seed dispersal. Our results provide empirical support for theoretical models of pollen transfer, which indicate that the commonly observed L-biased morph ratios inNarcissusspecies result from significant intra-morph mating in the L-morph because of its atypical floral morphology.
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Bai WN, Zeng YF, Zhang DY. Mating patterns and pollen dispersal in a heterodichogamous tree, Juglans mandshurica (Juglandaceae). THE NEW PHYTOLOGIST 2007; 176:699-707. [PMID: 17725556 DOI: 10.1111/j.1469-8137.2007.02202.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Mating patterns in heterodichogamous species are generally considered to be disassortative between flowering morphs, but this hypothesis has hitherto not been vigorously tested. Here, mating patterns and pollen dispersal were studied in Juglans mandshurica, a heterodichogamous wind-pollinated species that is widely distributed in northern and north-eastern China. Paternity analyses carried out on 11 microsatellite loci were used to estimate morph-specific rates of outcrossing and disassortative mating. Pollen dispersal and genetic structure were also investigated in the population under study. The mating pattern of J. mandshurica was highly outcrossing and disassortative. Pairwise values of intramorph relatedness were much higher than those of intermorph relatedness, and a low level of biparental inbreeding was detected. There was no significant difference in outcrossing and disassortative mating rates between the two morphs. The effective pollen dispersal distribution showed an excess of near-neighbor matings, and most offspring of individual trees were sired by one or two nearby trees. These results corroborate the previous suggestion that mating in heterodichogamous plant species is mainly disassortative between morphs, which not only prevents selfing but also effectively reduces intramorph inbreeding.
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Affiliation(s)
- Wei-Ning Bai
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- MOE Key Laboratory for Biodiversity Science and Ecological Engineering, College of Life Sciences, Beijing Normal University, Beijing 100875, China
| | - Yan-Fei Zeng
- MOE Key Laboratory for Biodiversity Science and Ecological Engineering, College of Life Sciences, Beijing Normal University, Beijing 100875, China
| | - Da-Yong Zhang
- MOE Key Laboratory for Biodiversity Science and Ecological Engineering, College of Life Sciences, Beijing Normal University, Beijing 100875, China
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Baker AM, Thompson JD, Barrett SC. Evolution and maintenance of stigma-height dimorphism in Narcissus. II. Fitness comparisons between style morphs. Heredity (Edinb) 2000; 84 ( Pt 5):514-24. [PMID: 10849076 DOI: 10.1046/j.1365-2540.2000.00686.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Populations of the insect-pollinated geophytes Narcissus assoanus and N. dubius (Amaryllidaceae) are commonly dimorphic for stigma height. An extensive survey of populations of the two species in SW France revealed a wide range of style-morph frequencies, particularly populations with significantly more long-styled than short-styled plants. Here we employ experimental and theoretical approaches to investigate potential selective mechanisms governing the variation in style-morph frequencies. Controlled pollination of both species demonstrated that N. assoanus is moderately self-sterile whereas N. dubius is highly self-compatible. Both intra- and intermorph crosses of N. assoanus were equally fertile, indicating that the species does not exhibit heteromorphic incompatibility. Estimates of female fertility (fruit- and seed-set) and multilocus estimates of outcrossing using allozyme markers provided no evidence of morph-specific differences in maternal components of reproductive success in natural populations of the two species. This result suggested that differences between the morphs in male fertility may be largely responsible for the observed morph-ratio variation. To investigate this hypothesis we developed a mating model that incorporates the genetics of stigma-height dimorphism and contrasting rates of assortative and disassortative mating in the style morphs. Simulation results demonstrated that stigma-height dimorphism will always be maintained when levels of disassortative mating are greater than assortative mating, and that the observed L-biased populations in Narcissus spp. probably result from greater levels of assortative mating in this morph in comparison with the S-morph.
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Affiliation(s)
- A M Baker
- Department of Botany, University of Toronto, Ontario, Canada.
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Eckert CG, Manicacci D, Barrett SCH. Frequency-dependent selection on morph ratios in tristylous Lythrum salicaria (Lythraceae). Heredity (Edinb) 1996. [DOI: 10.1038/hdy.1996.185] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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Eckert CG, Barrett SCH. Post-pollination mechanisms and the maintenance of outcrossing in self-compatible, tristylous, Decodon verticillatus (Lythraceae). Heredity (Edinb) 1994. [DOI: 10.1038/hdy.1994.56] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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Genetic drift and the maintenance of the style length polymorphism in tristylous populations of Eichhornia paniculata (Pontederiaceae). Heredity (Edinb) 1992. [DOI: 10.1038/hdy.1992.148] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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Heterostylous Genetic Polymorphisms: Model Systems for Evolutionary Analysis. EVOLUTION AND FUNCTION OF HETEROSTYLY 1992. [DOI: 10.1007/978-3-642-86656-2_1] [Citation(s) in RCA: 93] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
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Morgan MT, Barrett SCH. Outcrossing rates and correlated mating within a population of Eichhornia paniculata (Pontederiaceae). Heredity (Edinb) 1990. [DOI: 10.1038/hdy.1990.33] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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Glover DE, Barrett SCH. Genetic variation in continental and island populations of Eichhornia paniculata (Pontederiaceae). Heredity (Edinb) 1987. [DOI: 10.1038/hdy.1987.91] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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