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Benvenuti S, Mazzoncini M. Entomogamy in wildflowers: What level of pollinator biodiversity is required? ACTA OECOLOGICA 2021. [DOI: 10.1016/j.actao.2021.103737] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Bee-Mediated Selection Favors Floral Sex Specialization in a Heterantherous Species: Strategies to Solve the Pollen Dilemma. PLANTS 2020; 9:plants9121685. [PMID: 33271837 PMCID: PMC7760250 DOI: 10.3390/plants9121685] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 11/27/2020] [Indexed: 12/15/2022]
Abstract
Animal-pollinated plants show a broad variation in floral morphology traits and gametophyte production within populations. Thus, floral traits related to plant reproduction and sexuality are usually exposed to pollinator-mediated selection. Such selective pressures may be even stronger in heterantherous and pollen flowers, in which pollen contributes to both bee feeding and pollination, overcoming the “pollen dilemma” or the inability to perform both functions simultaneously. We describe the phenotypic gender and sexual organ morphology of flowers in two populations of Macairea radula (Melastomataceae), a heterantherous and buzz-pollinated species with pollen flowers. We estimated selection gradients on these traits through female and male fitness components. Both populations showed sizeable phenotypic gender variation, from strict hermaphrodites to increased femaleness or maleness. We found a continuous variation in style and stamen size, and this variation was correlated with corresponding shape values of both sexual organs. We detected bee-mediated selection towards short and long styles through seed number and towards intermediate degrees of heteranthery through pollen removal in one population, and selection towards increased maleness through pollen dispersal in both populations. Our results suggest that bee-mediated selection favors floral sex specialization and stylar dimorphism in M. radula, optimizing reproductive success and solving the pollen dilemma.
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Wessinger CA, Hileman LC. Parallelism in Flower Evolution and Development. ANNUAL REVIEW OF ECOLOGY EVOLUTION AND SYSTEMATICS 2020. [DOI: 10.1146/annurev-ecolsys-011720-124511] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Flower evolution is characterized by widespread repetition, with adaptations to pollinator environment evolving in parallel. Recent studies have expanded our understanding of the developmental basis of adaptive floral novelties—petal fusion, bilateral symmetry, heterostyly, and floral dimensions. In this article, we describe patterns of trait evolution and review developmental genetic mechanisms underlying floral novelties. We discuss the diversity of mechanisms for parallel adaptation, the evidence for constraints on these mechanisms, and how constraints help explain observed macroevolutionary patterns. We describe parallel evolution resulting from similarities at multiple hierarchical levels—genetic, developmental, morphological, functional—which indicate general principles in floral evolution, including the central role of hormone signaling. An emerging pattern is mutational bias that may contribute to rapid patterns of parallel evolution, especially if the derived trait can result from simple degenerative mutations. We argue that such mutational bias may be less likely to govern the evolution of novelties patterned by complex developmental pathways.
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Affiliation(s)
- Carolyn A. Wessinger
- Department of Biological Sciences, University of South Carolina, Columbia, South Carolina 29208, USA
| | - Lena C. Hileman
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas 66045, USA
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Barrett SCH. 'A most complex marriage arrangement': recent advances on heterostyly and unresolved questions. THE NEW PHYTOLOGIST 2019; 224:1051-1067. [PMID: 31631362 DOI: 10.1111/nph.16026] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Accepted: 05/23/2019] [Indexed: 05/09/2023]
Abstract
Heterostylous genetic polymorphisms provide paradigmatic systems for investigating adaptation and natural selection. Populations are usually comprised of two (distyly) or three (tristyly) mating types, maintained by negative frequency-dependent selection resulting from disassortative mating. Theory predicts this mating system should result in equal style-morph ratios (isoplethy) at equilibrium. Here, I review recent advances on heterostyly, focusing on examples challenging stereotypical depictions of the polymorphism and unresolved questions. Comparative analyses indicate multiple origins of heterostyly, often within lineages. Ecological studies demonstrate that structural components of heterostyly are adaptations improving the proficiency of animal-mediated cross-pollination and reducing pollen wastage. Both neutral and selective processes cause deviations from isoplethy in heterostylous populations, and, under some ecological and demographic conditions, cause breakdown of the polymorphism, resulting in either the evolution of autogamy and mixed mating, or transitions to alternative outcrossing systems, including dioecy. Earlier ideas on the genetic architecture of the S-locus supergene governing distyly have recently been overturned by discovery that the dominant S-haplotype is a hemizygous region absent from the s-haplotype. Ecological, phylogenetic and molecular genetic data have validated some features of theoretical models on the selection of the polymorphism. Although heterostyly is the best-understood floral polymorphism in angiosperms, many unanswered questions remain.
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Affiliation(s)
- Spencer C H Barrett
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, M5S 3B2, Canada
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Hu D, Li W, Gao S, Lei T, Hu J, Shen P, Li Y, Li J. Untargeted metabolomic profiling reveals that different responses to self and cross pollination in each flower morph of the heteromorphic plant Plumbago auriculata. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2019; 144:413-426. [PMID: 31634809 DOI: 10.1016/j.plaphy.2019.10.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Revised: 10/08/2019] [Accepted: 10/08/2019] [Indexed: 06/10/2023]
Abstract
Heteromorphic self-incompatibility (HetSI), which is regulated by sporophytes, occurs in some species as a strategy to promote cross-pollination. This research aimed to reveal metabolic changes occurring in HetSI. We used fluorescence microscopy as a tool to compare growth behavior in self-incompatible (SI) and self-compatible (SC) pollination in both pin and thrum flowers of Plumbago auriculata and to identify the ideal timepoint for sample collection for subsequent experiments. We also employed scanning electron microscopy (SEM) to evaluate intermorph structural differences in the pollen grains and stigmas in relation to HetSI. Importantly, UPLC-MS/MS was applied in this study to identify metabolites, compare metabolic differences between pin and thrum styles and monitor metabolic changes in SC and SI pollinations in the two types of flowers. The metabolites mainly included amino acids/peptides, flavonoids, glycosides/sugars, phenols, other organic acids, fatty acids (derivatives)/lipids, amines, aldehydes, alkaloids, alcohols and other compounds. Surprisingly, energy-related nutrients such as amino acids/peptides and tricarboxylic acid cycle-related metabolites were found at higher levels in SI pollinations than in SC pollinations. This result indicates that physiological changes in pollen-stigma interactions differ in pin and thrum styles and SC and SI pollinations and that energy deficiency is not one of the reasons for HetSI.
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Affiliation(s)
- Di Hu
- Landscape Research Institute, Sichuan Agricultural University, Huimin Road 211, Wenjiang District, Chengdu, 611130, China.
| | - Wenji Li
- Landscape Research Institute, Sichuan Agricultural University, Huimin Road 211, Wenjiang District, Chengdu, 611130, China.
| | - Suping Gao
- Landscape Research Institute, Sichuan Agricultural University, Huimin Road 211, Wenjiang District, Chengdu, 611130, China.
| | - Ting Lei
- Landscape Research Institute, Sichuan Agricultural University, Huimin Road 211, Wenjiang District, Chengdu, 611130, China.
| | - Ju Hu
- Landscape Research Institute, Sichuan Agricultural University, Huimin Road 211, Wenjiang District, Chengdu, 611130, China.
| | - Ping Shen
- Landscape Research Institute, Sichuan Agricultural University, Huimin Road 211, Wenjiang District, Chengdu, 611130, China.
| | - Yurong Li
- Landscape Research Institute, Sichuan Agricultural University, Huimin Road 211, Wenjiang District, Chengdu, 611130, China.
| | - Jiani Li
- Landscape Research Institute, Sichuan Agricultural University, Huimin Road 211, Wenjiang District, Chengdu, 611130, China.
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Costa J, Torices R, Barrett SCH. Evolutionary history of the buildup and breakdown of the heterostylous syndrome in Plumbaginaceae. THE NEW PHYTOLOGIST 2019; 224:1278-1289. [PMID: 30825331 DOI: 10.1111/nph.15768] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2018] [Accepted: 02/23/2019] [Indexed: 05/27/2023]
Abstract
The evolutionary pathways leading to the heterostylous syndrome are not well understood, and models concerning the origins of distyly differ in the order in which reciprocal herkogamy and self-incompatibility evolve. We investigated the evolution and breakdown of distyly in Plumbaginaceae, a family with considerable diversity of floral traits and reproductive systems. Using Bayesian Markov chain Monte Carlo analyses and stochastic character mapping, we examined the evolutionary assembly and breakdown of the heterostylous syndrome based on a well-resolved phylogeny of 121 species of Plumbaginaceae and six outgroup taxa using five nuclear and plastid gene regions. We used the distribution of reproductive traits and reconstructed ancestral characters across phylogenies to evaluate competing models for the evolution of distyly. The most likely common ancestor of Plumbaginaceae was self-incompatible and monomorphic for sex-organ arrangement and pollen-stigma characters. Character state reconstructions indicated that reciprocal herkogamy evolved at least three times and that shifts to selfing and apomixis occurred on multiple occasions. Our results provide comparative support for the early ideas of H. G. Baker on evolutionary pathways in Plumbaginaceae, and the more recent selfing avoidance model by D. & B. Charlesworth in which distyly evolves from self-incompatible ancestors.
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Affiliation(s)
- Joana Costa
- Department of Life Sciences, Centre for Functional Ecology, University of Coimbra, Calçada Martim de Freitas, 3000-456, Coimbra, Portugal
| | - Rubén Torices
- Area of Biodiversity and Conservation, Universidad Rey Juan Carlos, c/Tulipán s/n., Móstoles, Madrid, E-28933, Spain
| | - Spencer C H Barrett
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, ON, Canada, M5S 3B2
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Barranco D, Arroyo J, Santos-Gally R. Avoiding sexual interference: herkogamy and dichogamy in style dimorphic flowers of Narcissus broussonetii (Amaryllidaceae). AOB PLANTS 2019; 11:plz038. [PMID: 31528325 PMCID: PMC6735907 DOI: 10.1093/aobpla/plz038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Accepted: 07/22/2019] [Indexed: 06/10/2023]
Abstract
Spatial (herkogamy) or temporal (dichogamy) separation of sex organs are mechanisms considered to restrict self-pollination and promote outcrossing. Additionally, avoidance of self-interference is proposed to be the driving force for the evolution of these mechanisms, particularly in self-incompatible species. However, species with anthers and stigmas at different levels may increase the rate of imprecise pollen transfer, resulting in pollen discounting. Non-reciprocal stylar dimorphism has been considered a transitional, unstable stage towards the evolution of reciprocal style dimorphism (distyly), to simultaneously avoid interference and lack of precision. In this study we investigate the spatial and temporal separation of sex organs in a population of the style dimorphic and self-incompatible Narcissus broussonetii and their consequences in the reciprocity between the sex organs of morphs and their fecundity. First, we evaluated the relative growth of sex organs after anthesis. Then, we studied the stigma receptivity along the flower lifespan including its effect on seed production in both morphs. Finally, given the weak reciprocity between the sex organs of morphs of this species, we estimated population genetic diversity parameters in Long- and Short-styled plants to explore differences between them as a result of rates of inbreeding due to different mating strategies. We observed that Long-styled plants and Short-styled plants present different strategies to avoid sexual interference and both of them had negative consequences in the reciprocity between the sex organs of morphs. Long-styled plants exhibited a delay in stigma receptivity and a higher growth rate of the style after anthesis, while Short-styled plants presented higher herkogamy and no delay in stigma receptivity. These findings suggest that the avoidance of self-interference, in stylar dimorphic Narcissus species, seems to be more critical than improving of reciprocity between the sex organs of morphs. This might explain why reciprocal herkogamy (distyly) is rare in the genus.
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Affiliation(s)
- Daniel Barranco
- Departamento de Biología Vegetal y Ecología, Universidad de Sevilla, apartado, Sevilla, Spain
| | - Juan Arroyo
- Departamento de Biología Vegetal y Ecología, Universidad de Sevilla, apartado, Sevilla, Spain
| | - Rocío Santos-Gally
- Departamento de Biología Vegetal y Ecología, Universidad de Sevilla, apartado, Sevilla, Spain
- CONACyT-Instituto de Ecología, A.P. 70-275, Ciudad Universitaria, Universidad Nacional Autónoma de México, Ciudad de México, México
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Arima K, Kyogoku D, Nakahama N, Suetsugu K, Ohtani M, Ishii C, Terauchi H, Terauchi Y, Isagi Y. Mating pattern of a distylous primrose in a natural population: unilateral outcrossing and asymmetric selfing between sexual morphs. Evol Ecol 2018. [DOI: 10.1007/s10682-018-9965-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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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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Yuan S, Barrett SCH, Duan T, Qian X, Shi M, Zhang D. Ecological correlates and genetic consequences of evolutionary transitions from distyly to homostyly. ANNALS OF BOTANY 2017; 120:775-789. [PMID: 28961784 PMCID: PMC5691548 DOI: 10.1093/aob/mcx098] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2017] [Accepted: 07/29/2017] [Indexed: 05/24/2023]
Abstract
BACKGROUND AND AIMS The outbreeding floral polymorphism heterostyly frequently breaks down, resulting in the evolution of self-fertilization as a result of homostyle formation. Here, the loss of floral polymorphism in distylous Primula oreodoxa, a sub-alpine species restricted to western Sichuan, China, was examined by investigating the ecological correlates and genetic consequences of mating system transitions. Several key questions were addressed. (1) What are the frequencies, geographical distribution and reproductive characteristics of floral morphs in distylous and homostylous populations? (2) Does increased elevation influence pollinator service and the likelihood of inbreeding in populations? (3) How often has homostyly originated and what are the consequences of the breakdown of distyly for the amounts and distribution of genetic diversity in populations? METHODS Fourteen populations throughout the range of P. oreodoxa were sampled, and morph frequencies and floral characteristics were recorded. Polymorphism at microsatellite loci and chloroplast DNA (cpDNA) variation were used to quantify population genetic structure and genetic relationships among populations. Controlled pollinations and studies of pollen tube growth and fertility were conducted to determine the compatibility status of populations and their facility for autonomous self-pollination. Finally, visitation rates of long- and short-tongued pollinators to distylous and homostylous populations at different elevations were compared to determine if increased elevation was associated with deterioration in pollinator service. KEY RESULTS In contrast to most heterostylous species, both distylous and homostylous morphs of P. oreodoxa are highly self-compatible, but only homostyles have the facility for autonomous self-pollination. Homostyles set significantly more fruit and seeds following open pollination than the distylous morphs. Visitation by long-tongued pollinators was significantly lower in homostylous populations, and overall rates of insect visitation decreased with elevation. Genetic diversity was significantly lower in homostylous populations, with evidence of increased inbreeding at higher elevation. Patterns of cpDNA variation were consistent with multiple transitions from distyly to homostyly and limited gene flow among populations. CONCLUSIONS The results of this study support the hypothesis that the multiple loss of floral polymorphism in distylous P. oreodoxa is associated with unsatisfactory pollinator service, with homostyles benefiting from reproductive assurance as a result of autonomous self-pollination.
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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, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Spencer C H Barrett
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada
| | - Tingting Duan
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
- Guangdong Ocean University, Zhanjiang, China
| | - Xin Qian
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Miaomiao Shi
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
| | - Dianxiang Zhang
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
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11
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Stone JL, Thomson JD. THE EVOLUTION OF DISTYLY: POLLEN TRANSFER IN ARTIFICIAL FLOWERS. Evolution 2017; 48:1595-1606. [DOI: 10.1111/j.1558-5646.1994.tb02198.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/1993] [Accepted: 01/12/1994] [Indexed: 11/28/2022]
Affiliation(s)
- Judy L. Stone
- Department of Ecology and Evolution State University of New York Stony Brook New York 11794
| | - James D. Thomson
- Department of Ecology and Evolution State University of New York Stony Brook New York 11794
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12
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Kohn JR, Graham SW, Morton B, Doyle JJ, Barrett SCH. RECONSTRUCTION OF THE EVOLUTION OF REPRODUCTIVE CHARACTERS IN PONTEDERIACEAE USING PHYLOGENETIC EVIDENCE FROM CHLOROPLAST DNA RESTRICTION‐SITE VARIATION. Evolution 2017; 50:1454-1469. [DOI: 10.1111/j.1558-5646.1996.tb03919.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/1995] [Accepted: 11/28/1995] [Indexed: 12/01/2022]
Affiliation(s)
- Joshua R. Kohn
- University of California at San Diego Department of Biology 9500 Gilman Drive La Jolla California 92093‐0116
| | - Sean W. Graham
- Department of Botany University of Toronto Toronto Ontario M5S 3B2 Canada
| | - Brian Morton
- Department of Biological Sciences, Barnard College Columbia University 30009 Broadway New York New York 10027
| | - Jeff J. Doyle
- Bailey Hortorium Cornell University Ithaca New York 14853
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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. POLLEN DISCOUNTING AND THE SPREAD OF A SELFING VARIANT IN TRISTYLOUS EICHHORNIA PANICULATA: EVIDENCE FROM EXPERIMENTAL POPULATIONS. Evolution 2017; 48:1576-1594. [PMID: 28568426 DOI: 10.1111/j.1558-5646.1994.tb02197.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/1993] [Accepted: 12/07/1993] [Indexed: 11/28/2022]
Abstract
Floral traits that increase self-fertilization are expected to spread unless countered by the effects of inbreeding depression, pollen discounting (reduced outcross pollen success by individuals with increased rates of self-fertilization), or both. Few studies have attempted to measure pollen discounting because to do so requires estimating the male outcrossing success of plants that differ in selfing rate. In natural populations of tristylous Eichhornia paniculata, selfing variants of the mid-styled morph are usually absent from populations containing all three style morphs but often predominate in nontrimorphic populations. We used experimental garden populations of genetically marked plants to investigate whether the effects of population morph structure on relative gamete transmission by unmodified (M) and selfing variants (M') of the mid-styled morph could explain their observed distribution. Transmission through ovules and self and outcross pollen by plants of the M and M' morphs were compared under trimorphic, dimorphic (S morph absent), and monomorphic (L and S morphs absent) population structures. Neither population structure nor floral morphology affected female reproductive success, but both had strong effects on the relative transmission of male gametes. The frequency of self-fertilization in the M' morph was consistently higher than that of the M morph under all morph structures, and the frequency of self-fertilization by both morphs increased as morph diversity of experimental populations declined. In trimorphic populations, total transmission by the M and M' morphs did not differ. The small, nonsignificant increase in selfing by the M' relative to the M morph was balanced by decreased outcross siring success, particularly on the S morph. In populations lacking the S morph, male gamete transmission by the M' morph was approximately 1.5 times greater than that by the M morph because of both increased selfing and increased success through outcross pollen donation. Therefore, gamete transmission strongly favored the M' morph only in the absence of the S morph, a result consistent with the distribution of the M' morph in nature. This study indicates that floral traits that alter the selfing rate can have large and context-dependent influences on outcross pollen donation.
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Affiliation(s)
- Joshua R Kohn
- University of California at San Diego, Department of Biology 0116, La Jolla, California, 92093
| | - Spencer C H Barrett
- Department of Botany, University of Toronto, Toronto, Ontario, M5S 3B2, Canada
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15
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Ågren J, Ericson L. POPULATION STRUCTURE AND MORPH-SPECIFIC FITNESS DIFFERENCES IN TRISTYLOUS LYTHRUM SALICARIA. Evolution 2017; 50:126-139. [DOI: 10.1111/j.1558-5646.1996.tb04479.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/1994] [Accepted: 01/04/1995] [Indexed: 11/28/2022]
Affiliation(s)
- Jon Ågren
- Department of Ecological Botany; Umeå University; S-901 87 Umeå Sweden
| | - Lars Ericson
- Department of Ecological Botany; Umeå University; S-901 87 Umeå Sweden
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16
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O'Neil P, Schmitt J. GENETIC CONSTRAINTS ON THE INDEPENDENT EVOLUTION OF MALE AND FEMALE REPRODUCTIVE CHARACTERS IN THE TRISTYLOUS PLANT
LYTHRUM SALICARIA. Evolution 2017; 47:1457-1471. [DOI: 10.1111/j.1558-5646.1993.tb02168.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/1992] [Accepted: 03/30/1993] [Indexed: 11/28/2022]
Affiliation(s)
- Pamela O'Neil
- Graduate Program in Ecology and Evolutionary Biology Brown University Providence Rhode Island 02912
| | - Johanna Schmitt
- Graduate Program in Ecology and Evolutionary Biology Brown University Providence Rhode Island 02912
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17
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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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Conner JK, Rush S, Kercher S, Jennetten P. MEASUREMENTS OF NATURAL SELECTION ON FLORAL TRAITS IN WILD RADISH (RAPHANUS RAPHANISTRUM). II. SELECTION THROUGH LIFETIME MALE AND TOTAL FITNESS. Evolution 2017; 50:1137-1146. [PMID: 28565276 DOI: 10.1111/j.1558-5646.1996.tb02354.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/1995] [Accepted: 01/26/1996] [Indexed: 11/28/2022]
Abstract
It has often been suggested that selection on floral traits in hermaphroditic plants should occur primarily through differences in male fitness. However, measurements of selection on floral traits through differences in lifetime male fitness have been lacking. We measured selection on a variety of wild radish floral traits using lifetime male fitness measures derived from genetic paternity analysis. These male fitness estimates were then combined with estimates of lifetime female fitness of the same plants to produce measurements of selection based on lifetime total fitness. Contrary to the prediction above, there was no strong evidence for selection on floral morphology through male fitness differences in any of the three years of the study, but there was strong selection for increased flower size through female fitness differences in one year. The main determinant of both male and female fitness in all years was flower number; this lead to moderately positive correlations between male and female fitness in all three years.
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Affiliation(s)
- Jeffrey K Conner
- Department of Ecology, Ethology, and Evolution, University of Illinois, Shelford Vivarium, 606 East Healey Street, Champaign, Illinois, 61820
| | - Scott Rush
- Department of Ecology, Ethology, and Evolution, University of Illinois, Shelford Vivarium, 606 East Healey Street, Champaign, Illinois, 61820
| | - Suzanne Kercher
- Department of Ecology, Ethology, and Evolution, University of Illinois, Shelford Vivarium, 606 East Healey Street, Champaign, Illinois, 61820
| | - Peter Jennetten
- Department of Ecology, Ethology, and Evolution, University of Illinois, Shelford Vivarium, 606 East Healey Street, Champaign, Illinois, 61820
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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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Gavrilets S, Cruzan MB. NEUTRAL GENE FLOW ACROSS SINGLE LOCUS CLINES. Evolution 2017; 52:1277-1284. [PMID: 28565387 DOI: 10.1111/j.1558-5646.1998.tb02009.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/1997] [Accepted: 05/04/1998] [Indexed: 12/01/2022]
Abstract
We study the strength of the genetic barrier to neutral gene flow in a general one-locus, two-allele model that includes viability selection as well as fertility selection and premating isolation. We have separately considered adult migration and pollen migration. Our theoretical results suggest that selection against hybrid formation in the form of fertility selection or assortative mating is more effective in preventing introgression of neutral alleles than is reduction in hybrid viability. We argue that in experimental studies of introgression testing of F1 hybrids is as important as testing of parental forms. To illustrate the utility of this approach, we estimate the strength of the barrier to neutral gene flow between Piriqueta caroliniana and P. viridis, between Iris hexagona and I. fulva, and between Chorthippus brunneus and C. biguttulus.
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Affiliation(s)
- Sergey Gavrilets
- Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, Tennessee, 37996-1610.,Department of Mathematics, University of Tennessee, Knoxville, Tennessee, 37996-1610
| | - Mitchell B Cruzan
- Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, Tennessee, 37996-1610.,Department of Botany, University of Tennessee, Knoxville, Tennessee, 37996-1610
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Cruzan MB, Barrett SCH. Postpollination discrimination between self and outcross pollen covaries with the mating system of a self-compatible flowering plant. AMERICAN JOURNAL OF BOTANY 2016; 103:568-576. [PMID: 26507113 DOI: 10.3732/ajb.1500139] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 05/28/2015] [Indexed: 06/05/2023]
Abstract
PREMISE OF THE STUDY Variation in the mating system of hermaphroditic plant populations is determined by interactions between genetic and environmental factors operating via both pre- and postmating processes. Models predicting the maintenance of intermediate outcrossing rates in animal-pollinated plants often assume that the mating system is primarily controlled by floral morphology and pollinator availability, but rarely has the influence of postpollination processes on variation in outcrossing been examined. METHODS We investigated the influence of stylar discrimination between illegitimate and legitimate pollen-tube growth and the pollen-load capacity of stigmas on mating-system variation in the annual, tristylous species Eichhornia paniculata using controlled crosses and genetic markers. This species exhibits an exceptionally broad range of outcrossing rates in natural populations. KEY RESULTS There was significant variation among populations in the pollen-load capacity of stigmas and the ability of styles to discriminate between illegitimate vs. legitimate pollen. There was strong correspondence between stylar-discrimination ability and variation in outcrossing rate among populations and style morphs. The combination of stigmatic pollen-load capacity and stylar discrimination explained more than 80% of the variation in outcrossing rates among populations. CONCLUSIONS The finding that stigmatic pollen-load capacity and stylar-discrimination ability contributed significantly to explaining the wide range of outcrossing rates in E. paniculata suggests that postpollination mechanisms play an important role in governing mating patterns in this species. The difference in levels of stylar discrimination between outcrossing and selfing populations may reflect a trade-off between selection for increased outcrossing and greater reproductive assurance.
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Affiliation(s)
- Mitchell B Cruzan
- Department of Biology, Portland State University, Portland, Oregon 97207 USA
| | - Spencer C H Barrett
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Ontario M5S 3B2 Canada
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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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Lee YW, Gould BA, Stinchcombe JR. Identifying the genes underlying quantitative traits: a rationale for the QTN programme. AOB PLANTS 2014; 6:plu004. [PMID: 24790125 PMCID: PMC4038433 DOI: 10.1093/aobpla/plu004] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2013] [Accepted: 01/01/2014] [Indexed: 05/19/2023]
Abstract
The goal of identifying the genes or even nucleotides underlying quantitative and adaptive traits has been characterized as the 'QTN programme' and has recently come under severe criticism. Part of the reason for this criticism is that much of the QTN programme has asserted that finding the genes and nucleotides for adaptive and quantitative traits is a fundamental goal, without explaining why it is such a hallowed goal. Here we outline motivations for the QTN programme that offer general insight, regardless of whether QTNs are of large or small effect, and that aid our understanding of the mechanistic dynamics of adaptive evolution. We focus on five areas: (i) vertical integration of insight across different levels of biological organization, (ii) genetic parallelism and the role of pleiotropy in shaping evolutionary dynamics, (iii) understanding the forces maintaining genetic variation in populations, (iv) distinguishing between adaptation from standing variation and new mutation, and (v) the role of genomic architecture in facilitating adaptation. We argue that rather than abandoning the QTN programme, we should refocus our efforts on topics where molecular data will be the most effective for testing hypotheses about phenotypic evolution.
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Affiliation(s)
- Young Wha Lee
- Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, ON, CanadaM5S 3B2
| | - Billie A. Gould
- Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, ON, CanadaM5S 3B2
| | - John R. Stinchcombe
- Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, ON, CanadaM5S 3B2
- Centre for the Analysis of Genome Evolution and Function, University of Toronto, Toronto, ON, CanadaM5S 3B2
- Corresponding author's e-mail address:
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Weber JJ, Weller SG, Sakai AK, Nguyen A, Tai ND, Domínguez CA, Molina-Freaner FE. Purging of inbreeding depression within a population of Oxalis alpina (Oxalidaceae). AMERICAN JOURNAL OF BOTANY 2012; 99:923-932. [PMID: 22539518 DOI: 10.3732/ajb.1100383] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
PREMISE OF THE STUDY Variation among individuals in levels of inbreeding depression associated with selfing levels could influence mating system evolution by purging deleterious alleles, but empirical evidence for this association is limited. METHODS We investigated the association of family-level inbreeding depression and presumed inbreeding history in a tristylous population of Oxalis alpina (Oxalidaceae). KEY RESULTS Mid-styled individuals possessed the greatest degree of self-compatibility (SC) and produced more autogamous capsules than short- or long-styled individuals. Offspring of highly self-compatible mid-styled individuals showed reduced inbreeding depression. Mid-styled plants that produced capsules autogamously exhibited reduced stigma-anther separation compared to mid-styled plants that produced no capsules autogamously. Reduced inbreeding depression was not correlated with stigma-anther separation, suggesting that self-compatibility and autogamy evolve before morphological changes in stigma-anther separation. CONCLUSIONS Purging of inbreeding depression occurred in SC mid-styled maternal families. Low inbreeding depression in SC mid-styled plants may lead to retention of the mid-styled morph in populations, despite the occurrence of higher selfing rates in mid-styled relative to short- or long-styled morphs. Variation among individuals in levels of self-fertilization within populations may lead to associations between inbreeding lineages and lower levels of inbreeding depression, influencing the evolution of mating systems.
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Affiliation(s)
- Jennifer J Weber
- Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697, USA
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Harder LD, Johnson SD. Darwin's beautiful contrivances: evolutionary and functional evidence for floral adaptation. THE NEW PHYTOLOGIST 2009; 183:530-545. [PMID: 19552694 DOI: 10.1111/j.1469-8137.2009.02914.x] [Citation(s) in RCA: 221] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Although not 'a professed botanist', Charles Darwin made seminal contributions to understanding of floral and inflorescence function while seeking evidence of adaptation by natural selection. This review considers the legacy of Darwin's ideas from three perspectives. First, we examine the process of floral and inflorescence adaptation by surveying studies of phenotypic selection, heritability and selection responses. Despite widespread phenotypic and genetic capacity for natural selection, only one-third of estimates indicate phenotypic selection. Second, we evaluate experimental studies of floral and inflorescence function and find that they usually demonstrate that reproductive traits represent adaptations. Finally, we consider the role of adaptation in floral diversification. Despite different diversification modes (coevolution, divergent use of the same pollen vector, pollinator shifts), evidence of pollination ecotypes and phylogenetic patterns suggests that adaptation commonly contributes to floral diversity. Thus, this review reveals a contrast between the inconsistent occurrence of phenotypic selection and convincing experimental and comparative evidence that floral traits are adaptations. Rather than rejecting Darwin's hypotheses about floral evolution, this contrast suggests that the tempo of creative selection varies, with strong, consistent selection during episodes of diversification, but relatively weak and inconsistent selection during longer, 'normal' periods of relative phenotypic stasis.
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Affiliation(s)
- Lawrence D Harder
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada T2N 1N4
| | - Steven D Johnson
- School of Biological and Conservation Sciences, University of KwaZulu-Natal, Private Bag X01 Scottsville, Pietermaritzburg 3209, South Africa
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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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Brys R, Jacquemyn H, Hermy M. Impact of mate availability, population size, and spatial aggregation of morphs on sexual reproduction in a distylous, aquatic plant. AMERICAN JOURNAL OF BOTANY 2007; 94:119-127. [PMID: 21642214 DOI: 10.3732/ajb.94.1.119] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
In distylous, self-incompatible plants, clonal propagation, unbalanced floral morph frequencies, and reduced population size can interfere with the functioning of distyly by compromising legitimate intermorph pollinations, resulting in reduced reproductive output. Here, we examined the mating system and the impact of mate availability, population size, and spatial aggregation of morphs on reproductive output in the distylous, clonal, aquatic plant Hottonia palustris. Controlled pollinations under greenhouse conditions detected no spontaneous selfing without the action of a pollen vector (autonomous autogamy) and demonstrated very low fruit and seed development after self-pollination. Intermorph (legitimate) crossings resulted in high reproductive output in both floral morphs (long- and short-styled individuals), whereas intramorph (illegitimate) crossings decreased fruit and seed development by more than 50%, indicating that the species has partial intramorph-incompatibility. In natural populations, small population size and increasing deviation of floral morph frequencies negatively affected reproductive outcome. Individuals of the majority morph type developed significantly fewer fruit and seeds than individuals of the minority morph type. This rapid decline in fecundity was symmetrical, indicating that regardless of which morph was in the majority, the same patterns of negative frequency-dependent mating occurred. Increasing spatial isolation between compatible morphs significantly reduced fruit and seed set in both morphs similarly. This study provides clear indications of frequency- and context-dependent mating in natural populations of a distylous plant species.
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Affiliation(s)
- Rein Brys
- Division of Forest, Nature and Landscape Research, Catholic University of Leuven, Celestijnenlaan 200 E, B-3001 Leuven, Belgium
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Hodgins KA, Barrett SCH. Mating patterns and demography in the tristylous daffodil Narcissus triandrus. Heredity (Edinb) 2006; 96:262-70. [PMID: 16449981 DOI: 10.1038/sj.hdy.6800792] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Mating patterns in plant populations are influenced by interactions between reproductive traits and ecological conditions, both factors that are likely to vary geographically. Narcissus triandrus, a wide-ranging heterostylous herb, exhibits populations with either two (dimorphic) or three (trimorphic) style morphs and displays substantial geographical variation in demographic attributes and floral morphology. Here, we investigate this variation to determine if demography, morphology, and mating system differ between the two sexual systems. Our surveys in Portugal and NW Spain indicated that dimorphic populations were less dense, of smaller size, and had larger plants and flowers compared to trimorphic populations. Outcrossing rates estimated using allozyme markers revealed similar outcrossing rates in dimorphic and trimorphic populations (t(m) dimorphic=0.759; t(m) trimorphic=0.710). All populations experienced significant inbreeding in progeny (mean F=0.143). In contrast, parental estimates of inbreeding were not significantly different from zero (mean F=0.062), implying that few inbred offspring survive to reproductive maturity due to inbreeding depression. Although the majority of inbreeding results from selfing, significant levels of biparental inbreeding were also detected in eight of the nine populations (mean s(s)-s(m)=0.081). Density was negatively associated with levels of selfing but positively associated with biparental inbreeding. Population size was positively associated with outcrossing but not biparental inbreeding. There were no consistent differences among the style morphs in outcrossing or biparental inbreeding indicating that the maintenance of trimorphism vs dimorphism is unlikely to be associated with inbreeding of maternal parents.
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Affiliation(s)
- K A Hodgins
- Department of Botany, University of Toronto, 25 Willcocks Street, Toronto, ON, Canada M5S 3B2.
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Hodgins KA, Barrett SCH. Female reproductive success and the evolution of mating-type frequencies in tristylous populations. THE NEW PHYTOLOGIST 2006; 171:569-80. [PMID: 16866959 DOI: 10.1111/j.1469-8137.2006.01800.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
In tristylous populations, mating-type frequencies are governed by negative frequency-dependent selection typically resulting in equal morph ratios at equilibrium. However, Narcissus triandrus generally exhibits long-styled (L)-biased populations with a deficiency of the mid-styled (M)-morph. Here we used a pollen-transfer model and measurements of female fertility in natural populations to investigate whether these uneven morph ratios were associated with variation in female reproductive success. Our theoretical analysis demonstrated that morph ratio bias can result from maternal fitness differences among the morphs, and that these effects were magnified by asymmetrical mating. In nine out of 15 populations of N. triandrus, seed set differed significantly among the morphs, but pollen limitation occurred in only two of 11 populations investigated. Average seed set of the M-morph was positively associated with its frequency in populations. Flower size was negatively correlated with the seed set of the M-morph. Our results suggest that interactions between mating patterns and female fertility are responsible for variation in morph frequencies and loss of the M-morph from tristylous populations of N. triandrus.
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Affiliation(s)
- Kathryn A Hodgins
- Department of Botany, University of Toronto, 25 Willcocks Street, Toronto, Ontario M5S 3B2, Canada.
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Armbruster WS, Pérez-Barrales R, Arroyo J, Edwards ME, Vargas P. Three-dimensional reciprocity of floral morphs in wild flax (Linum suffruticosum): a new twist on heterostyly. THE NEW PHYTOLOGIST 2006; 171:581-90. [PMID: 16866960 DOI: 10.1111/j.1469-8137.2006.01749.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Here, we studied the floral morphology and pollination of the distylous plant Linum suffruticosum (Linaceae) in southern Spain. We observed a previously unreported form of distyly that involved twisting and bending of styles and stamens during floral development to achieve three-dimensional reciprocity of anthers and stigmas in the long-styled (pin) and short-styled (thrum) morphs. This developmental pattern causes pin pollen to be placed on the underside of pollinating Usia flies (Bombyliidae), and thrum pollen to be placed on the top of the thorax and abdomen. The pin stigmas contact the flies on the dorsum, apparently picking up predominantly thrum pollen, and the thrum stigmas contact the flies on the ventral surface, apparently picking up predominantly pin pollen. This form of heterostyly would appear on morphological grounds to be far more efficient in dispersing pollen between compatible morphs than the typical pin-thrum system. If so, this plant fits Darwin's prediction of efficient pollen flow between heterostylous morphs more closely than anything Darwin himself reported. Molecular phylogenetic analyses indicate that this form of heterostyly evolved in a lineage that already had typical heterostyly. The analyses also indicate that there have been several independent origins of heterostyly in Linum and at least one reversal to stylar monomorphism.
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Affiliation(s)
- W Scott Armbruster
- School of Biological Sciences, University of Portsmouth, Portsmouth PO1 2DY, UK.
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Jesson LK, Barrett SCH, Day T. A theoretical investigation of the evolution and maintenance of mirror-image flowers. Am Nat 2003; 161:916-30. [PMID: 12858276 DOI: 10.1086/375176] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2002] [Accepted: 11/14/2002] [Indexed: 11/04/2022]
Abstract
Enantiostyly is the deflection of the female sex organ either to the left or to the right side of the floral axis, resulting in mirror-image flowers. Two types of enantiostyly occur: in monomorphic enantiostyly, individuals exhibit both flower forms, whereas in dimorphic enantiostyly, the forms occur on separate plants. Monomorphic enantiostyly is known from at least 10 families, whereas dimorphic enantiostyly is reported in only three. Phylogenetic evidence suggests that monomorphic enantiostyly has evolved from a straight-styled ancestor and that dimorphic enantiostyly is derived from monomorphic enantiostyly. Here, we use theoretical models to investigate the role of pollen transfer in influencing these evolutionary transitions. We used numerical calculations to examine the evolution of monomorphic and dimorphic enantiostyly under different conditions of pollen transfer, inbreeding depression, and pollinator visitation. Our results demonstrate that in comparison to a putative straight-styled ancestor, both monomorphic and dimorphic enantiostyly function to reduce geitonogamous pollen transfer with a concomitant increase in pollen export. Our calculations suggest that the first stage in the evolution of monomorphic enantiostyly involves the deflection of the style only, followed by selection for reciprocity in anther position to promote more precise cross-pollination. Constraints associated with the developmental genetics of left-right asymmetries may account for the low number of evolutionary transitions from monomorphic to dimorphic enantiostyly, despite the evolutionary stability of this condition once it arises.
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Affiliation(s)
- Linley K Jesson
- Department of Botany, University of Toronto, 25 Willcocks Street, Toronto, Ontario M5S 3B2, Canada.
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Thompson JD, Barrett SCH, Baker AM. Frequency-dependent variation in reproductive success in Narcissus: implications for the maintenance of stigma-height dimorphism. Proc Biol Sci 2003; 270:949-53. [PMID: 12803910 PMCID: PMC1691332 DOI: 10.1098/rspb.2002.2318] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Negative frequency-dependent selection is a major selective force maintaining sexual polymorphisms. However, empirical demonstrations of frequency-dependent reproductive success are rare, particularly in plants. We investigate this problem by manipulating the frequencies of style morphs in a natural population of Narcissus assoanus, a self-incompatible herb with style-length dimorphism and intra-morph compatibility. We predicted that the reproductive success of morphs would vary negatively with their frequency because of the effects of morph-specific differences in sex-organ position on patterns of pollen transfer. This prediction was generally supported. The fruit and seed set of the two morphs did not differ significantly in plots with 1 : 1 morph ratios. However, short-styled plants produced significantly fewer seeds than long-styled plants in monomorphic plots, and significantly more seeds than long-styled plants in plots with 'long-biased' morph ratios. These patterns indicate that in the absence of physiological barriers to intra-morph mating, negative frequency-dependent selection contributes to the maintenance of stylar polymorphism through inter-morph pollen transfer. Our experimental results also provide insights into the mechanisms governing the biased style-morph ratios in populations of Narcissus species.
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Affiliation(s)
- John D Thompson
- Centre d'Ecologie Fonctionnelle et Evolutive, CNRS, 1919 Route de Mende, 34293 Montpellier Cedex 5, France.
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Pailler T, Maurice S, Thompson JD. Pollen transfer patterns in a distylous plant with overlapping pollen-size distributions. OIKOS 2002. [DOI: 10.1034/j.1600-0706.2002.990211.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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ALVES DOS SANTOS ISABEL. Flower-visiting bees and the breakdown of the tristylous breeding system of Eichhornia azurea (Swartz) Kunth (Pontederiaceae). Biol J Linn Soc Lond 2002. [DOI: 10.1046/j.1095-8312.2002.00122.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Li P, Johnston MO. Comparative floral morphometrics of distyly and homostyly in three evolutionary lineages of Amsinckia (Boraginaceae). ACTA ACUST UNITED AC 2001. [DOI: 10.1139/b01-107] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Using three ancestor-descendant lineages of Amsinckia (Boraginaceae), we studied changes in floral morphology associated with evolution of the breeding system. Each lineage comprised a distylous ancestor and a homostylous descendant: (i) Amsinckia furcata Suksd. Amsinckia vernicosa Hook. & Arn.; (ii) Amsinckia douglasiana A. DC. Amsinckia tessellata var. gloriosa (Suksd.) Hoover; and (iii) Amsinckia spectabilis Fischer & C. Meyer. Comparisons of 26 floral traits were made between pins and thrums within the distylous groups, between distyly (pins and thrums combined) and homostyly as well as among pins, thrums, and homostyles. Differences among the morphs were also compared across the three lineages. In distylous flowers, the six traits directly related to stamen height or pistil height varied as expected from their close relationship to the definition of pins and thrums, with the stamen-height-related characters greater in thrums and the pistil-height-related characters greater in pins. Thrums had larger pollen grains in all lineages. Pollen production was either similar in the two distylous morphs or lower in thrums than in pins, depending on species. Thrums also tended to have larger style cross-sectional area and style transmission tissue cross-sectional area. In two of three lineages, thrums had longer corollas, whereas pins exceeded thrums in functional antherstigma separation and in stigmatic papilla size. The size order of a trait in pins versus thrums was consistent in all lineages for 18 of 26 traits; in seven of the eight remaining traits, A. spectabilis was the unusual lineage. Sepal length, corolla width, and stigma size did not differ significantly between the two distylous morphs. In homostyles, traits related to anther height and pistil height were intermediate between pins and thrums in all lineages; for other traits, including antherstigma separation and overall size, homostyles generally had the smallest values. For most traits, lineages differed in the degree of differentiation among the three morphs as well as between distyly and homostyly. Thus, in Amsinckia, the evolution of homostyly involves a general reduction in flower size, but by an amount that varies both among traits and among lineages.Key words: Amsinckia, dimorphism, distyly, floral evolution, homostyly, mating system.
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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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Cook LM, Soltis PS. Mating systems of diploid and allotetraploid populations of Tragopogon (Asteraceae). II. Artificial populations. Heredity (Edinb) 2000; 84 ( Pt 4):410-5. [PMID: 10849064 DOI: 10.1046/j.1365-2540.2000.00654.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Polyploidization has long been recognized as an important force in the diversification of plants. Theoretical models predict that polyploids may be expected to exhibit higher rates of self-fertilization than do closely related diploid species. Wild populations of the neopolyploid Tragopogon mirus (4n) exhibited slightly higher rates of outcrossing than did populations of one of its progenitors, T. dubius (2n). In the current study, outcrossing rates in populations of T. dubius and T. mirus were estimated using artificial arrays constructed to maximize the chances of detecting outcrossing events. The artificial diploid population is more highly outcrossing (t=0.727; family-level estimates range from 0.00 to 1. 32) than the tetraploid population (t=0.591; family-level estimates range from 0.00 to 1.14), although the difference between them is not statistically significant. The results of this study, combined with those of the previous work on wild populations, suggest that mating systems in these species vary more among populations than between ploidal levels. This could be because of the relatively recent origins of the tetraploid species; there may have been insufficient time since the formations of the tetraploids for shifts in mating systems to occur.
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Affiliation(s)
- L M Cook
- Department of Botany, PO Box 64238, Washington State University, Pullman, WA 99164-4238, USA.
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Abstract
Computer simulations are used to evaluate maximum likelihood methods for inferring male fertility in plant populations. The maximum likelihood method can provide substantial power to characterize male fertilities at the population level. Results emphasize, however, the importance of adequate experimental design and evaluation of fertility estimates, as well as limitations to inference (e.g., about the variance in male fertility or the correlation between fertility and phenotypic trait value) that can be reasonably drawn.
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Affiliation(s)
- M T Morgan
- Départment of Botany, Department of Genetics and Cell Biology, Washington State University, Pullman, Washington 99164-4238, USA.
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Barrett SCH, Cole WW, Arroyo J, Cruzan MB, Lloyd DG. Sexual polymorphisms in Narcissus triandrus (Amaryllidaceae): is this species tristylous? Heredity (Edinb) 1997. [DOI: 10.1038/hdy.1997.21] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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The comparative biology of pollination and mating in flowering plants. Philos Trans R Soc Lond B Biol Sci 1997. [DOI: 10.1098/rstb.1996.0110] [Citation(s) in RCA: 229] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The diversification of many flowering plant families has been attributed to adaptive radiation of pollination and mating systems accompanying changes in ecology and life history. Reproductive traits in seed plants therefore provide a potentially rich source of diversity for comparative and phylogenetic studies. Here we address three topics in reproductive biology: floral allocation strategies, mating systems and life history, and the origin of complex reproductive syndromes using various comparative methods. Results from these studies generally complement and inform those obtained from previous microevolutionary work at the population level. Historical inferences concerning reproductive character evolution in some taxa can be hampered by topological uncertainties in tree reconstruction and a lack of resolution in molecular phylogenies. Future insights into the ecology and evolution of plant reproductive adaptations using comparative approaches will require well resolved phylogenies, particularly at the species level.
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Conner JK, Davis R, Rush S. The effect of wild radish floral morphology on pollination efficiency by four taxa of pollinators. Oecologia 1995; 104:234-245. [DOI: 10.1007/bf00328588] [Citation(s) in RCA: 106] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/1995] [Accepted: 05/19/1995] [Indexed: 11/28/2022]
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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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Unequal morph frequencies in populations of tristylous Lythrum salicaria (Lythraceae) from southern Sweden. Heredity (Edinb) 1994. [DOI: 10.1038/hdy.1994.10] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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Thompson JD, Dommée B. Sequential variation in the components of reproductive success in the distylousJasminum fruticans (Oleaceae). Oecologia 1993; 94:480-487. [PMID: 28313987 DOI: 10.1007/bf00566962] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/1992] [Accepted: 12/11/1992] [Indexed: 12/01/2022]
Abstract
A 2-year study of three natural populations of the distylousJasminum fruticans showed that mean fruit and seed production were significantly greater in shortstyled plants (thrums) than in long-styled plants (pins). In this study, we investigated the role of four sequential factors which may differentially influence fruit and seed set in the two floral morphs: (1) differences in flowering phenology, (2) a limitation of pollen transfer towards pins, (3) a differential capacity of the two morphs to act through famale and male function and (4) differential fruit abortion in the two morphs. Fruit set was significantly influenced by differences in flowering phenology although there were no differences in flowering time between the two morphs. supplementary pollinations in a natural population significantly increased fruit set and reduced the difference in fruit set between the two morphs in relation to controls, indicating a limitation on pollen transfer which was most severe towards pin stigmas. In reciprocal crosses, seed set was significantly dependent on the paternal and maternal identity of the pin parent. There was no significant variation among thrums for their performance as male or female parent. Furthermore, individual pin plants with relatively high percentage seed set as female parents gave poor seed set as male parents and vice-versa. Whereas fruit removal had no effect on seed number in thrum plants, a greater proportion of viable seeds were produced on pin plants which were left to naturally mature their fruits than on pins which had fruits artificially removed, suggesting the occurrence of selective fruit abortion in pins but not in thrums. The initially greater maternal fitness of thrums due to their greater success as pollen recipients may thus be opposed by increased viable seed set in the pins due to factors acting after the pollination stage. The relative reproductive success of floral morphs in the distylousJ. fruticans is thus differentially influenced by ecological factors occurring at different stages of the reproductive process.
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Affiliation(s)
- John D Thompson
- Centre d'Ecologie Fonctionelle et Evolutive, C.N.R.S., Route de Mende, B.P. 5051, 34033, Montpellier Cedex, France
| | - Bertrand Dommée
- Centre d'Ecologie Fonctionelle et Evolutive, C.N.R.S., Route de Mende, B.P. 5051, 34033, Montpellier Cedex, France
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Al Wadi H, Richards AJ. Primary homostyly in Primula L. subgenus Sphondylia (Duby) Rupr. and the evolution of distyly in Primula. THE NEW PHYTOLOGIST 1993; 124:329-338. [PMID: 33874351 DOI: 10.1111/j.1469-8137.1993.tb03823.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We have studied eight species classified within Primula L. subgenus Sphondylia (Duby) Rupr. Two have monomorphic flowers and four have typically distylous flowers. P. floribunda Wall, includes both monomorphic and distylous races, while P. boveana Decres. has an incompletely discontinuous dimorphism for style length and pollen size, but is monomorphic for anther position. All the species have been tested and they are fully self-fertile. Evidence suggests that dimorphisms for style length (G/g), pollen size (P/p) and anther position (A/a) are each under independent genetic control. In the monomorphic P. verticillata, variations in stigma papilla length and style cell length appear to result from developmental correlates with style-length variation. Both the monomorphic species show some continuous variation for herkogamy. Several of the species studied show an incomplete development of the full distylous syndrome typical of most Primula species. If it is assumed that these represent evolutionary stages in the development of the full syndrome, and if it is assumed that diallelic incompatibility evolved after the evolution of distyly, then it would appear that the components of the distyly linkage group are likely to have evolved from a non-herkogamous ancestor in the following order: (i) short style mutant G; (ii) small pollen mutant p; (iii) low anther position mutant a.
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Affiliation(s)
- Hussen Al Wadi
- Department of Agricultural and Environmental Science, Ridley Building, University of Newcastle upon Tyne, NE1 7RU, UK
| | - A J Richards
- Department of Agricultural and Environmental Science, Ridley Building, University of Newcastle upon Tyne, NE1 7RU, UK
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