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Holt R, Kwok A, Dorken ME. Increased spatial-genetic structure in a population of the clonal aquatic plant Sagittaria latifolia (Alismataceae) following disturbance. Heredity (Edinb) 2020; 124:514-523. [PMID: 31827265 PMCID: PMC7028999 DOI: 10.1038/s41437-019-0286-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 11/02/2019] [Accepted: 11/07/2019] [Indexed: 11/09/2022] Open
Abstract
The spatial genetic structure (SGS) of plant populations is determined by the outcome of key ecological processes, including pollen and seed dispersal, the intensity of local resource competition among newly recruited plants, and patterns of mortality among established plants. Changes in the magnitude of SGS over time can provide insights into the operation of these processes. We measured SGS in a population of the clonal aquatic plant, Sagittaria latifolia that had been disturbed by flooding, both before and after the flood. Over the four-year interval between measurements, we found substantial changes in the magnitude of SGS. In the first measurement (pre-flood), SGS was weak, even over short distances. By contrast, there was substantial SGS in the second measurement (post-flood), particularly over short distances. This change in SGS was accompanied by near complete turnover in the genotypic composition of the population. The genotypic richness of the population (the number of unique clones scaled by the sample size) was halved over the four-year interval. The clonal subrange-the distances between shoots within clones-also shrank considerably, with more than 5% of shoots having clone-mates at distances >10 m before the flood, but fewer than 5% of shoots having clone-mates at distances beyond 2 m afterwards. Clonal turnover and the re-establishment of SGS in clonal populations are both expected following local extirpation and recruitment. These data reveal the genetic signatures of disturbance and a subsequent flush of seedling recruitment and clonal expansion.
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Affiliation(s)
- Ryan Holt
- Environmental and Life Sciences Graduate Program, Trent University, Peterborough, ON, K9J 0G2, Canada
| | - Allison Kwok
- Environmental and Life Sciences Graduate Program, Trent University, Peterborough, ON, K9J 0G2, Canada
| | - Marcel E Dorken
- Department of Biology, Trent University, Peterborough, ON, K9J 0G2, Canada.
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Wang X, Huang L, Gichira AW, Wang X. The effects of density on size-dependent gender plasticity in the monoecious species Sagittaria potamogetifolia (Alismataceae). Saudi J Biol Sci 2019; 26:413-420. [PMID: 31485186 PMCID: PMC6717134 DOI: 10.1016/j.sjbs.2018.11.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Revised: 11/20/2018] [Accepted: 11/20/2018] [Indexed: 11/23/2022] Open
Abstract
AIM To test the fitness-gain curve model proposes that cosexual plants adjust their sex ratios and resource allocation depending on their size. In this study, the monoecious species Sagittaria potamogetifolia was used as a model to determine the effects of plant size and density on gender modification and reproductive allocation. METHODS AND MATERIALS Various traits, including flower number and plant biomass, were measured under four different artificially constructed population density treatments. More male flowers were produced than female flowers per individual at high densities, while the opposite trend was observed at low densities. This trend was particularly evident in the highest density treatment. RESULTS A trade-off was discovered between male-female sex allocations in the highest density treatment (40 individuals m-2). The allometric growth of reproductive organs compared with plant size was detected, as evidenced by the reproductive structures' biomass and flower numbers. However, in the highest density treatment, size was weakly negatively correlated with femaleness. CONCLUSION Thus, S. potamogetifolia has a reproductive strategy that easily adjusts to different reproductive environmental densities.
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Affiliation(s)
- Xiaowen Wang
- Laboratory of Plant Mating Systems and Evolutionary Genetics, College of Life Sciences, Wuhan University, Wuhan, P.O. Box: 430072, Hubei Province, China
| | - Lanjie Huang
- College of Life Sciences, Hubei University, Wuhan, P.O. Box: 430072, China
| | - Andrew Wanyoike Gichira
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, P.O. Box: 430074, Hubei Province, China
- Life Science College, University of Chinese Academy of Sciences, Beijing, P.O. Box: 100049, China
| | - Xiaofan Wang
- College of Life Sciences, Wuhan University, Wuhan, P.O. Box: 430072, Hubei Province, China
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Goodnoe TT, Hill JP. Plasticity of female reproductive resource allocation depends on the presence or absence of prior environmental sex determination in Ceratopteris richardii. Ecol Evol 2018; 8:6133-6143. [PMID: 29988448 PMCID: PMC6024121 DOI: 10.1002/ece3.4159] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Revised: 04/04/2018] [Accepted: 04/09/2018] [Indexed: 11/17/2022] Open
Abstract
Resource allocation plasticity enables individuals to alter patterns of nutrient use between reproductive and vegetative output to better fit their current environment. In sexually labile plant species, abiotic environmental factors can influence expression of dimorphic gender, resulting in environmental sex determination (ESD), which potentially reduces the need for plasticity of resource allocation by preemptively matching an individual's future nutrient demands to resource availability in its location. Ceratopteris richardii gametophytes exhibit gender-dependent differences in relative carbon and nitrogen content, and ESD in certain nutrient environments. This study examined whether prior ESD in C. richardii gametophyte populations reduced subsequent plasticity of reproductive allocation compared to instances where no ESD occurred, by quantifying phenotypic responses to reduced P, N, or CO 2 availabilities. All three nutrient-limited environments resulted in decreased size of egg-bearing (meristic) gametophytes compared to nonlimited environments, but gametophytes failed to respond to N and CO 2 limitation at the time of sex determination, resulting in no ESD. N limitation resulted in a predictable allometric re-allocation of resources based on small gametophyte size, whereas CO 2 limitation caused a change in reproductive output consistent with true plasticity. Withholding exogenous P caused ESD and had no effect on relative reproductive output of resultant meristic gametophytes because the size decrease was minor. Under P limitation, ESD matched the resource demands of gender phenotypes to their environment before the onset of developmental dimorphism, reducing the need for large allocation adjustments after sex determination.
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Affiliation(s)
- Taylor T. Goodnoe
- Department of Biological SciencesIdaho State UniversityPocatelloIdaho
| | - Jeffrey P. Hill
- Department of Biological SciencesIdaho State UniversityPocatelloIdaho
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Stojanova B, Maurice S, Cheptou PO. Is plasticity across seasons adaptive in the annual cleistogamous plant Lamium amplexicaule? ANNALS OF BOTANY 2016; 117:681-91. [PMID: 26995537 PMCID: PMC4817529 DOI: 10.1093/aob/mcw013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Accepted: 11/23/2015] [Indexed: 05/20/2023]
Abstract
BACKGROUND AND AIMS Many angiosperms exhibit cleistogamy, the production of both cleistogamous flowers (CL), which remain closed and obligately self-pollinated, and chasmogamous flowers (CH), which are potentially open-pollinated. The CH proportion can be plastic. Plasticity is adaptive if environmental changes can be reliably assessed and responded to with an appropriate phenotype and if plastic genotypes have higher fitness in variable environments than non-plastic ones. METHODS We studied the plastic response of four natural populations from northern and southern France of an annual cleistogamous plant, Lamium amplexicaule, to predictable seasonal variation. Plants were grown in a semi-controlled environment in spring and in autumn. We assessed the variation in flower number, phenology and cleistogamy-related traits, which were all plastic with respect to season. The CH proportion was higher in spring than in autumn in all four populations. KEY RESULTS We showed significant stabilizing selection for cleistogamy traits, with higher optimal CH proportions and more pronounced stabilizing selection in spring than in autumn. Observed CH proportions were close to the predicted optimal CH proportions in each season except in autumn for southern populations, which do not experience the autumnal growing season in nature. CONCLUSIONS These results are consistent with adaptive plasticity across seasons of cleistogamy in L. amplexicaule.We propose that adaptive plasticity of cleistogamy could be driven by pollination environment variation, with CL flowers providing reproductive assurance when pollinators are scarce and CH flowers reducing the inbreeding depression in offspring when pollinators are abundant.
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Affiliation(s)
- B Stojanova
- LBPV LUNAM Université de Nantes, 2 chemin de la Houssinière, 44000 Nantes, France, Institut des Sciences de l'Evolution, Université de Montpellier, CNRS, IRD, EPHE - C.C. 065, Place Eugène Bataillon - 34095 Montpellier cedex 05, France and CEFE UMR 5175, CNRS, Université de Montpellier, Université Paul-Valéry Montpellier, EPHE - 1919, route de Mende - 34293 Montpellier cedex 05, France
| | - S Maurice
- Institut des Sciences de l'Evolution, Université de Montpellier, CNRS, IRD, EPHE - C.C. 065, Place Eugène Bataillon - 34095 Montpellier cedex 05, France and
| | - P-O Cheptou
- CEFE UMR 5175, CNRS, Université de Montpellier, Université Paul-Valéry Montpellier, EPHE - 1919, route de Mende - 34293 Montpellier cedex 05, France
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Varga S, Laaksonen E, Siikamäki P, Kytöviita MM. Absence of sex differential plasticity to light availability during seed maturation in Geranium sylvaticum. PLoS One 2015; 10:e0118981. [PMID: 25738943 PMCID: PMC4349700 DOI: 10.1371/journal.pone.0118981] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Accepted: 01/27/2015] [Indexed: 11/24/2022] Open
Abstract
Sex-differential plasticity (SDP) hypothesis suggests that since hermaphrodites gain fitness through both pollen and seed production they may have evolved a higher degree of plasticity in their reproductive strategy compared to females which achieve fitness only through seed production. SDP may explain the difference in seed production observed between sexes in gynodioecious species in response to resource (nutrients or water) availability. In harsh environments, hermaphrodites decrease seed production whereas females keep it relatively similar regardless of the environmental conditions. Light availability can be also a limiting resource and thus could theoretically affect differently female and hermaphrodite seed output even though this ecological factor has been largely overlooked. We tested whether the two sexes in the gynodioecious species Geranium sylvaticum differ in their tolerance to light limitation during seed maturation in the field. We used a fully factorial block experiment exposing female and hermaphrodite plants to two different light environments (control and shade) after their peak flowering period. Specifically, we measured fruit and seed production in response to decreased light availability and compared it between the sexes. Shading reduced the number of fruits and seeds produced, but the decrease was similar between the sexes. Furthermore, shading delayed seed production by three days in both sexes, but did not affect seed mass, seed P content, or the probability of re-flowering the following year. Our results give no evidence for reproductive SDP in response to light during seed maturation.
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Affiliation(s)
- Sandra Varga
- Department of Biological and Environmental Science, University of Jyväskylä, P.O. Box 35, 40014, Jyväskylä, Finland
| | - Ester Laaksonen
- Department of Biology, University of Oulu, P.O. Box 3000, 90014, Oulu, Finland
| | | | - Minna-Maarit Kytöviita
- Department of Biological and Environmental Science, University of Jyväskylä, P.O. Box 35, 40014, Jyväskylä, Finland
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Renner SS. The relative and absolute frequencies of angiosperm sexual systems: dioecy, monoecy, gynodioecy, and an updated online database. AMERICAN JOURNAL OF BOTANY 2014; 101:1588-96. [PMID: 25326608 DOI: 10.3732/ajb.1400196] [Citation(s) in RCA: 326] [Impact Index Per Article: 32.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
UNLABELLED • PREMISE OF THE STUDY Separating sexual function between different individuals carries risks, especially for sedentary organisms. Nevertheless, many land plants have unisexual gametophytes or sporophytes. This study brings together data and theoretical insights from research over the past 20 yr on the occurrence and frequency of plant sexual systems, focusing on the flowering plants.• METHODS A list of genera with dioecious species, along with other information, is made available (http://www.umsl.edu/∼renners/). Frequencies of other sexual systems are tabulated, and data on the genetic regulation, ecological context, and theoretical benefits of dioecy reviewed.• KEY RESULTS There are 15600 dioecious angiosperms in 987 genera and 175 families, or 5-6% of the total species (7% of genera, 43% of families), with somewhere between 871 to 5000 independent origins of dioecy. Some 43% of all dioecious angiosperms are in just 34 entirely dioecious clades, arguing against a consistent negative influence of dioecy on diversification. About 31.6% of the dioecious species are wind-pollinated, compared with 5.5-6.4% of nondioecious angiosperms. Also, 1.4% of all angiosperm genera contain dioecious and monoecious species, while 0.4% contain dioecious and gynodioecious species. All remaining angiosperm sexual systems are rare. Chromosomal sex determination is known from 40 species; environmentally modulated sex allocation is common. Few phylogenetic studies have focused on the evolution of dioecy.• CONCLUSIONS The current focus is on the genetic mechanisms underlying unisexual flowers and individuals. Mixed strategies of sexual and vegetative dispersal, together with plants' sedentary life style, may often favor polygamous systems in which sexually inconstant individuals can persist. Nevertheless, there are huge entirely dioecious clades of tropical woody plants.
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Affiliation(s)
- Susanne S Renner
- Systematic Botany and Mycology, University of Munich, 80638 Munich, Germany
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Pannell JR, Eppley SM, Dorken ME, Berjano R. Regional variation in sex ratios and sex allocation in androdioecious Mercurialis annua. J Evol Biol 2014; 27:1467-77. [PMID: 24618014 DOI: 10.1111/jeb.12352] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Revised: 02/03/2014] [Accepted: 02/03/2014] [Indexed: 11/29/2022]
Abstract
In androdioecious metapopulations, where males co-occur with hermaphrodites, the absence of males from certain populations or regions may be explained by locally high selfing rates, high hermaphrodite outcross siring success (e.g. due to high pollen production by hermaphrodites), or to stochastic processes (e.g. the failure of males to invade populations or regions following colonization or range expansion by hermaphrodites). In the Iberian Peninsula and Morocco, the presence of males with hermaphrodites in the wind-pollinated androdioecious plant Mercurialis annua (Euphorbiaceae) varies both among populations within relatively small regions and among regions, with some regions lacking males from all populations. The species is known to have expanded its range into the Iberian Peninsula from a southern refugium. To account for variation in male presence in M. annua, we test the following hypotheses: (1) that males are absent in areas where plant densities are lower, because selfing rates should be correspondingly higher; (2) that males are absent in areas where hermaphrodites produce more pollen; and (3) that males are absent in areas where there is an elevated proportion of populations in which plant density and hermaphrodite pollen production disfavour their invasion. We found support for predictions two and three in Morocco (the putative Pleistocene refugium for M. annua) but no support for any hypothesis in Iberia (the expanded range). Our results are partially consistent with a hypothesis of sex-allocation equilibrium for populations in Morocco; in Iberia, the absence of males from large geographical regions is more consistent with a model of sex-ratio evolution in a metapopulation with recurrent population turnover. Our study points to the role of both frequency-dependent selection and contingencies imposed by colonization during range expansions and in metapopulations.
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Affiliation(s)
- J R Pannell
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
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Yakimowski SB, Barrett SCH. Variation and evolution of sex ratios at the northern range limit of a sexually polymorphic plant. J Evol Biol 2014; 27:1454-66. [DOI: 10.1111/jeb.12322] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Revised: 12/08/2013] [Accepted: 12/16/2013] [Indexed: 10/25/2022]
Affiliation(s)
- S. B. Yakimowski
- Department of Ecology and Evolutionary Biology; University of Toronto; Toronto ON Canada
| | - S. C. H. Barrett
- Department of Ecology and Evolutionary Biology; University of Toronto; Toronto ON Canada
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Litrico I, Maurice S. Resources, competition and selfing: their influence on reproductive system evolution. Evol Ecol 2012. [DOI: 10.1007/s10682-012-9613-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Van Drunen WE, Dorken ME. Trade-offs between clonal and sexual reproduction in Sagittaria latifolia (Alismataceae) scale up to affect the fitness of entire clones. THE NEW PHYTOLOGIST 2012; 196:606-616. [PMID: 22897332 DOI: 10.1111/j.1469-8137.2012.04260.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Many plants combine sexual reproduction with vegetative propagation, but how trade-offs between these reproductive modes affect fitness is poorly understood. Although such trade-offs have been demonstrated at the level of individual shoots (ramets), there is little evidence that they scale up to affect genet fitness. For hermaphrodites, reproductive investment is further divided between female and male sexual functions. Female function should generally incur greater carbon costs than male function, which might involve greater nitrogen (N) costs. Using a common garden experiment with diclinous, clonal Sagittaria latifolia we manipulated investment in reproduction through female and male sex functions of 412 plants from monoecious and dioecious populations. We detected a 1:1 trade-off between biomass investment in female function and clonal reproduction. For male function, there was no apparent trade-off between clonal and sexual reproduction in terms of biomass investment. Instead, male function incurred a substantially higher N cost. Our results indicate that: trade-offs between investment in clonal propagation and sexual reproduction occur at the genet level in S. latifolia; and sexual reproduction interferes with clonal expansion, with investment in female function limiting the quantity of clonal propagules produced, and investment in male function limiting the nutrient content of clonal propagules.
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Affiliation(s)
- Wendy E Van Drunen
- Department of Biology, Trent University, 1600 West Bank Drive, Peterborough, ON, K9J 7B8, Canada
| | - Marcel E Dorken
- Department of Biology, Trent University, 1600 West Bank Drive, Peterborough, ON, K9J 7B8, Canada
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Perry LE, Pannell JR, Dorken ME. Two's company, three's a crowd: experimental evaluation of the evolutionary maintenance of trioecy in Mercurialis annua (Euphorbiaceae). PLoS One 2012; 7:e35597. [PMID: 22532862 PMCID: PMC3330815 DOI: 10.1371/journal.pone.0035597] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Accepted: 03/19/2012] [Indexed: 11/25/2022] Open
Abstract
Trioecy is an uncommon sexual system in which males, females, and hermaphrodites co-occur as three clearly different gender classes. The evolutionary stability of trioecy is unclear, but would depend on factors such as hermaphroditic sex allocation and rates of outcrossing vs. selfing. Here, trioecious populations of Mercurialis annua are described for the first time. We examined the frequencies of females, males and hermaphrodites across ten natural populations and evaluated the association between the frequency of females and plant densities. Previous studies have shown that selfing rates in this species are density-dependent and are reduced in the presence of males, which produce substantially more pollen than hermaphrodites. Accordingly, we examined the evolutionary stability of trioecy using an experiment in which we (a) indirectly manipulated selfing rates by altering plant densities and the frequency of males in a fully factorial manner across 20 experimental plots and (b) examined the effect of these manipulations on the frequency of the three sex phenotypes in the next generation of plants. In the parental generation, we measured the seed and pollen allocations of hermaphrodites and compared them with allocations by unisexual plants. In natural populations, females occurred at higher frequencies in denser patches, a finding consistent with our expectations. Under our experimental conditions, however, no combination of plant densities and male frequencies was associated with increased frequencies of females. Our results suggest that the factors that regulate female frequencies in trioecious populations of M. annua are independent of those regulating male frequencies (density), and that the stable co-existence of all three sex phenotypes within populations is unlikely.
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Affiliation(s)
- Laura E. Perry
- Department of Biology, Trent University, Peterborough, Ontario, Canada
| | - John R. Pannell
- Department of Plant Sciences, University of Oxford, Oxford, United Kingdom
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
| | - Marcel E. Dorken
- Department of Biology, Trent University, Peterborough, Ontario, Canada
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Karron JD, Ivey CT, Mitchell RJ, Whitehead MR, Peakall R, Case AL. New perspectives on the evolution of plant mating systems. ANNALS OF BOTANY 2012; 109:493-503. [PMID: 22210849 PMCID: PMC3278297 DOI: 10.1093/aob/mcr319] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
BACKGROUND The remarkable diversity of mating patterns and sexual systems in flowering plants has fascinated evolutionary biologists for more than a century. Enduring questions about this topic include why sexual polymorphisms have evolved independently in over 100 plant families, and why proportions of self- and cross-fertilization often vary dramatically within and among populations. Important new insights concerning the evolutionary dynamics of plant mating systems have built upon a strong foundation of theoretical models and innovative field and laboratory experiments. However, as the pace of advancement in this field has accelerated, it has become increasingly difficult for researchers to follow developments outside their primary area of research expertise. SCOPE In this Viewpoint paper we highlight three important themes that span and integrate different subdisciplines: the changes in morphology, phenology, and physiology that accompany the transition to selfing; the evolutionary consequences of pollen pool diversity in flowering plants; and the evolutionary dynamics of sexual polymorphisms. We also highlight recent developments in molecular techniques that will facilitate more efficient and cost-effective study of mating patterns in large natural populations, research on the dynamics of pollen transport, and investigations on the genetic basis of sexual polymorphisms. This Viewpoint also serves as the introduction to a Special Issue on the Evolution of Plant Mating Systems. The 15 papers in this special issue provide inspiring examples of recent discoveries, and glimpses of exciting developments yet to come.
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Affiliation(s)
- Jeffrey D Karron
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI 53201, USA.
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Spigler RB, Ashman TL. Gynodioecy to dioecy: are we there yet? ANNALS OF BOTANY 2012; 109:531-43. [PMID: 21807691 PMCID: PMC3278288 DOI: 10.1093/aob/mcr170] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2011] [Accepted: 05/05/2011] [Indexed: 05/08/2023]
Abstract
BACKGROUND The 'gynodioecy-dioecy pathway' is considered to be one of the most important evolutionary routes from hermaphroditism to separate sexes (dioecy). Despite a large accumulation of evidence for female seed fertility advantages in gynodioecious species (females and hermaphrodites coexist) in support of the first step in the gynodioecy-dioecy pathway, we still have very little evidence for the second step, i.e. the transition from gynodioecy to dioecy. SCOPE We review the literature to evaluate whether basic predictions by theory are supported. To establish whether females' seed fertility advantage and frequencies are sufficient to favour the invasion of males, we review these for species along the gynodioecy-dioecy pathway published in the last 5 years. We then review the empirical evidence for predictions deriving from the second step, i.e. hermaphrodites' male fertility increases with female frequency, selection favours greater male fertility in hermaphrodites in gynodioecious species, and, where males and hermaphrodites coexist with females (subdioecy), males have greater male fertility than hermaphrodites. We review how genetic control and certain ecological features (pollen limitation, selfing, plasticity in sex expression and antagonists) influence the trajectory of a population along the gynodioecy-dioecy pathway. CONCLUSIONS Females tend to have greater seed fertility advantages over hermaphrodites where the two coexist, and this advantage is positively correlated with female frequency across species, as predicted by theory. A limited number of studies in subdioecious species have demonstrated that males have an advantage over hermaphrodites, as also predicted by theory. However, less evidence exists for phenotypic selection to increase male traits of hermaphrodites or for increasing male function of hermaphrodites in populations with high female frequency. A few key case studies underline the importance of examining multiple components of male fertility and the roles of pollen limitation, selfing and plasticity, when evaluating advantages. We conclude that we do not yet have a full understanding of the transition from gynodioecy to dioecy.
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Affiliation(s)
| | - Tia-Lynn Ashman
- Department of Biological Sciences, 4249 Fifth Ave., University of Pittsburgh, Pittsburgh, PA 15260-3929, USA
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15
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Vaughton G, Ramsey M. Gender plasticity and sexual system stability in Wurmbea. ANNALS OF BOTANY 2012; 109:521-30. [PMID: 21831858 PMCID: PMC3278287 DOI: 10.1093/aob/mcr163] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
BACKGROUND AND AIMS Sexually dimorphic populations are often located in drier habitats than cosexual populations. Gender plasticity (GP), whereby hermaphrodites alter female and male functions depending on resources, and sex-differential plasticity (SDP) between hermaphrodites and unisexuals are predicted to affect sexual system stability. Here, GP and SDP are evaluated in cosexual and gynodioecious Wurmbea biglandulosa and sub-dioecious and dioecious W. dioica. METHODS GP was evaluated under two resource conditions, compared among sexual systems and assessed as to whether (1) males produced perfect flowers and (2) hermaphrodites altered investment in perfect (female function) and total (male function) flowers. SDP was assessed within sexual systems as differences between sex functions of hermaphrodites vs. unisexuals. Males and hermaphrodites were compared to assess whether size thresholds for female function differed among sexual systems. Plasticity costs were evaluated using correlations between female function and male traits in hermaphrodites, and in W. dioica by comparing hermaphrodite and male regressions between plant size and pollen production. KEY RESULTS In dioecious W. dioica no males exhibited GP, whereas 100 % did in gynodioecious and cosexual W. biglandulosa. In sub-dioecious W. dioica, resources affected GP (high, 66 %; low, 42 %). Hermaphrodites in all sexual systems reduced perfect but not total flowers under low resources. Unisexuals were unaffected, demonstrating SDP for female function only. Thresholds for female function were greater in sub-dioecious W. dioica than in W. biglandulosa. Plasticity costs were detected only in sub-dioecious W. dioica. CONCLUSIONS SDP for female function could assist female establishment in cosexual populations and maintain females in gynodioecious and sub-dioecious populations. Although the absence of male SDP should stabilize sub-dioecy, plasticity costs would render sub-dioecy unstable, favouring canalized males over hermaphrodites. This study highlights the importance of interactions between environmental conditions and hermaphrodite sex expression for the stability of dimorphic sexual systems.
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Affiliation(s)
- Glenda Vaughton
- Botany, University of New England, Armidale, NSW 2351, Australia.
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16
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Avise J. Clones, hermaphrodites and pregnancies: nature's oddities offer evolutionary lessons on reproduction. J Zool (1987) 2011. [DOI: 10.1111/j.1469-7998.2011.00869.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- J.C. Avise
- Department of Ecology and Evolutionary Biology; University of California; Irvine; CA; USA
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17
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Perry LE, Dorken ME. The evolution of males: support for predictions from sex allocation theory using mating arrays of sagittaria latifolia (alismataceae). Evolution 2011; 65:2782-91. [PMID: 21967421 DOI: 10.1111/j.1558-5646.2011.01344.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Investment in male function should often yield diminishing fitness returns, subjecting the evolution of male phenotypes to substantial constraints. In plants, the subdivision of male function via the gradual presentation of pollen might minimize these constraints by preventing the saturation of receptive stigmas. Here, we report on an investigation of (1) patterns of investment in male function by plants in hermaphroditic (monoecious) and dioecious populations of Sagittaria latifolia, and (2) patterns of siring success by males versus hermaphrodites in experimental mating arrays. We show that in natural populations, males from dioecious populations had greater investment in male function than hermaphrodites in monoecious populations. However, as a proportion of total flower production, males presented substantially fewer flowers at once than hermaphrodites. In comparison with hermaphrodites, therefore, males prolonged the period over which they presented pollen. In mating arrays comprised of females, males, and hermaphrodites, siring success by males increased linearly with flower production. This finding is consistent with the existence of a linear gain curve for male function in S. latifolia and supports the idea that the gradual deployment of male function enables plants to avoid diminishing returns on the investment in male function.
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Affiliation(s)
- Laura E Perry
- Department of Biology, Trent University, Peterborough, ON, K9J 7B8, Canada.
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18
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Spigler RB, Ashman TL. Sex ratio and subdioecy in Fragaria virginiana: the roles of plasticity and gene flow examined. THE NEW PHYTOLOGIST 2011; 190:1058-1068. [PMID: 21352233 DOI: 10.1111/j.1469-8137.2011.03657.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Here we examined the roles of sex-differential plasticity (SDP) and gene flow in sex ratio evolution of subdioecious Fragaria virginiana. We assessed whether female frequency varied with resource availability in 17 natural populations and then characterized plasticity and mean investment in allocation to female function at flower and plant levels in the sex morphs in the glasshouse. We estimated patterns of population divergence using five microsatellite markers. We reveal SDP in fruit production substantial enough to translate into a higher equilibrium female frequency at low resources. Thus SDP can account, in part, for the strong negative relationship between female frequency and resources found in the field. Pollen-bearing morphs varied in plasticity across populations, and the degree of plasticity in fruit number was positively correlated with in situ variation in nitrogen (N) availability, suggesting an adaptive component to sex-allocation plasticity. Low neutral genetic differentiation, indicating high gene flow or recent divergence, may contribute to the absence of population differentiation in fruit-setting ability of pollen-bearing morphs despite considerable sex ratio variation. We consider how these processes, in addition to other features of this system, may work in concert to influence sex ratios and to hinder the evolution of dioecy in F. virginiana.
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Affiliation(s)
- Rachel B Spigler
- Department of Biological Sciences, University of Pittsburgh, 4249 Fifth Ave, Pittsburgh, PA 15260-3929, USA
| | - Tia-Lynn Ashman
- Department of Biological Sciences, University of Pittsburgh, 4249 Fifth Ave, Pittsburgh, PA 15260-3929, USA
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19
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Castilla AR, Alonso C, Herrera CM. Exploring local borders of distribution in the shrub Daphne laureola: Individual and populations traits. ACTA OECOLOGICA-INTERNATIONAL JOURNAL OF ECOLOGY 2011. [DOI: 10.1016/j.actao.2011.02.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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20
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Van Etten ML, Chang SM. Effects of environmental heterogeneity on the distribution of sexes within and among populations in a gynodioecious species, Geranium maculatum. THE NEW PHYTOLOGIST 2009; 183:649-660. [PMID: 19659586 DOI: 10.1111/j.1469-8137.2009.02940.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Populations containing both females and hermaphrodites (dimorphic) are generally found in drier sites than those with only hermaphrodites (monomorphic). The sex-differential plasticity hypothesis (SDP) suggests that this is caused by hermaphrodites reducing allocation to seeds in harsh environments, allowing female establishment. We proposed that a similar process could explain sex distribution within populations. We compared light availability and soil moisture between sites of three monomorphic and three dimorphic populations of Geranium maculatum and between microsites occupied by females and hermaphrodites within populations. We also correlated seed production in dimorphic populations with environmental measures. We found that dimorphic and monomorphic populations occurred in sites with similar soil moisture but within two dimorphic populations females occurred in drier microsites than hermaphrodites, as predicted by the SDP hypothesis. Contrary to the predictions, hermaphrodites' seed production was not influenced by the environment. Rather, females' seed production was correlated with environmental conditions in two populations, although the direction of the correlation differed between populations. Our results suggest that in this species, the SDP hypothesis does not explain sex distribution among or within populations. However, microsite environments may influence the distribution of sexes within a population and potentially aid in maintaining gynodioecy.
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Affiliation(s)
- Megan L Van Etten
- Department of Plant Biology, University of Georgia, Athens, GA 30602, USA
| | - Shu-Mei Chang
- Department of Plant Biology, University of Georgia, Athens, GA 30602, USA
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21
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Dorken ME, Pannell JR. Hermaphroditic Sex Allocation Evolves When Mating Opportunities Change. Curr Biol 2009; 19:514-7. [DOI: 10.1016/j.cub.2009.01.067] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2008] [Revised: 01/30/2009] [Accepted: 01/30/2009] [Indexed: 10/21/2022]
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