Biased Sex Ratios in Plants: Theory and Trends

Sinclair, Jordan P.; Emlen, John T.; Freeman, D. Carl

doi:10.1007/s12229-011-9065-0

Cited by 95 publications

(71 citation statements)

References 75 publications

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“…The widespread occurrence in dioecious species of both sexual and clonal reproduction provides an opportunity to investigate how these two reproductive modes interact to influence sex ratios and fitness in plant populations. The classical theoretical arguments of Düsing (34), and Fisher (35) predict 1:1 sex ratios in dioecious populations, but recent comparative studies of plant populations indicate considerable variation in sex ratios both within and among species (36,37). Determining the ecological, demographic, and genetic factors responsible for this variation is an important problem in evolutionary biology.…”

Section: Clonality In Plants With Sexual Polymorphismsmentioning

confidence: 99%

Influences of clonality on plant sexual reproduction

Barrett

2015

Proc. Natl. Acad. Sci. U.S.A.

216

195

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Flowering plants possess an unrivaled diversity of mechanisms for achieving sexual and asexual reproduction, often simultaneously. The commonest type of asexual reproduction is clonal growth (vegetative propagation) in which parental genotypes (genets) produce vegetative modules (ramets) that are capable of independent growth, reproduction, and often dispersal. Clonal growth leads to an expansion in the size of genets and increased fitness because large floral displays increase fertility and opportunities for outcrossing. Moreover, the clonal dispersal of vegetative propagules can assist "mate finding," particularly in aquatic plants. However, there are ecological circumstances in which functional antagonism between sexual and asexual reproductive modes can negatively affect the fitness of clonal plants. Populations of heterostylous and dioecious species have a small number of mating groups (two or three), which should occur at equal frequency in equilibrium populations. Extensive clonal growth and vegetative dispersal can disrupt the functioning of these sexual polymorphisms, resulting in biased morph ratios and populations with a single mating group, with consequences for fertility and mating. In populations in which clonal propagation predominates, mutations reducing fertility may lead to sexual dysfunction and even the loss of sex. Recent evidence suggests that somatic mutations can play a significant role in influencing fitness in clonal plants and may also help explain the occurrence of genetic diversity in sterile clonal populations. Highly polymorphic genetic markers offer outstanding opportunities for gaining novel insights into functional interactions between sexual and clonal reproduction in flowering plants.clonal growth | dioecy | geitonogamy | heterostyly | somatic mutations

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Section: Clonality In Plants With Sexual Polymorphismsmentioning

confidence: 99%

Influences of clonality on plant sexual reproduction

Barrett

2015

Proc. Natl. Acad. Sci. U.S.A.

216

195

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“…Recent reviews of sex ratio in dioecious species report that male-biased sex ratios are almost twice as frequent as female-biased sex ratios (Sinclair et al 2012, Field et al 2013. …”

Section: Discussionmentioning

confidence: 99%

“…In particular, male-biased sex ratio was associated to fleshy fruits, biotic pollination and seed dispersal (Sinclair et al 2012). Fuchsia parviflora, shows those characteristics and a significant overall male-biased sex ratio was found (P < 0.03).…”

Section: Sex Ratio In Fuchsia Parvifloramentioning

confidence: 99%

Population size, sex-ratio and sexual dimorphism in <em>Fuchsia parviflora</em> (Onagraceae) an endemic dioecious shrub

2017

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Background: In small dioecious populations stochastic events may increase biased sex ratios decreasing the viability of populations. Moreover, pollinators may promote pollen limitation if sexual dimorphism related to pollinator attraction, such as flower size and number of flowers are present. Questions: 1) In order to estimate the viability of natural populations of Fuchsia parviflora, population size, sex ratio and fruit production were estimated in natural populations. In addition, number of flowers and floral traits were compared between genders as a way to predict pollinator preferences to particular gender. Studied species: Fuchsia parviflora is an endemic Mexican dioecious, animal-pollinated shrub. Methods: In 2012 and 2013 population sizes and sex ratios were estimated in 12 populations in the states of Michoacan and Jalisco. In addition, the number of flowers and floral traits were estimated between genders. Results: Population sizes varied widely from 14 to 550 individuals and an overall significant male-bias was found. Male frequency varied from 50 to 78 % among populations and some male-biased populations were also the small populations. A significant negative correlation between population size and male frequency was found, but no relationship was found between population size and number of flowers or fruit production. Reproductive plant height varied among populations but not between genders within populations. Male plants had larger number of flowers but floral longevity did not differ between genders. Consistently in all evaluated populations, staminate flowers had longer floral tubes and wider corolla diameter than pistillate flowers. Conclusions: In accordance to stochastic sex ratio fluctuations by small population sizes, it was expected to find populations with male and female-biased sex ratios. However, the absence of female-biased sex ratio suggests that male plants may have a higher survival chance but this hypothesis has to be tested. Although populations seem not to be seed-limited, some populations were cut during this study to plant avocado trees, suggesting the need to implement conservation efforts to preserve populations of F. parviflora. Keywords: biotic pollination, dioecy, floral dimorphism, population size. ResumenAntecedentes: En poblaciones dioicas pequeñas, eventos estocásticos pueden incrementar los sesgos en las proporciones sexuales lo que puede afectar la viabilidad de las poblaciones. Además, los polinizadores pueden promover la limitación de polen si existe un fuerte dimorfismo sexual en el tamaño y número de flores. Preguntas: Con la finalidad de estimar la viabilidad de las poblaciones de Fuchsia parviflora se estimaron los tamaños poblacionales, las proporciones sexuales y la producción de frutos en poblaciones naturales. Además, se comparó el despliegue floral y los caracteres florales entre géneros como una forma de predecir posibles sesgos de los polinizadores hacia algún género en particular. Especie de estudio: Fuchsia parviflora es un arbusto dioico de ...

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“…The preponderance of archegoniate gametophytes in dioecious bryophytes contrasts with a preponderance of staminate sporophytes in dioecious angiosperms (with interesting exceptions) [44,45]. A factor that may contribute to female biases being more common in bryophytes than in angiosperms is that pollen can be transferred to ovules over much greater distances than sperm can be transferred to archegonia.…”

Section: (A) Female Advantagementioning

confidence: 97%

Living together and living apart: the sexual lives of bryophytes

Haig¹

2016

Phil. Trans. R. Soc. B

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One contribution of 15 to a theme issue 'Weird sex: the underappreciated diversity of sexual reproduction'. Haploid gametophytes of bryophytes spread by clonal growth but mate locally, within an area defined by the range of sperm movement. Rarity of establishment from spores or vegetative competition can result in unisexual populations unable to reproduce sexually. Females typically outcompete males, probably because females expend fewer resources than males on the production of gametes. Extreme sexual dimorphism-tiny males growing as epiphytes on much larger females-has evolved many times. Haploid selfing is common in bryophytes with bisexual gametophytes, and results in completely homozygous sporophytes. Spores from these sporophytes recapitulate the genotype of their single haploid parent. This process can be considered analogous to 'asexual' reproduction with 'sexual' reproduction occurring after rare outcrossing between haploid parents. Ferns also produce bisexual haploid gametophytes but, unlike bryophytes, haploid outcrossing predominates over haploid selfing. This difference is probably related to clonal growth and vegetative competition occurring in the haploid but not the diploid phase in bryophytes, but the reverse in ferns. Ferns are thereby subject to stronger inbreeding depression than bryophytes.This article is part of the themed issue 'Weird sex: the underappreciated diversity of sexual reproduction'. Sexual lives of bryophytesAnimal life histories are characterized by multicellular diploid individuals that produce haploid gametes by meiosis. Gametes are the only haploid cells of such life cycles. The life histories of bryophytes (mosses, liverworts and hornworts) are fundamentally different. Multicellular haploid gametophytes (gameteproducing plants) produce gametes by mitosis. The fertilization of an ovum by a sperm produces a zygote that develops into a short-lived multicellular diploid sporophyte (spore-producing plant) that grows attached to the maternal gametophyte on which it depends for nutrients. Sporophytes produce haploid spores by meiosis that germinate to produce new gametophytes (figure 1). Mating is restricted to the distance over which sperm can find ova, usually in the millimetre to centimetre range [1]. Clonal expansion occurs via vegetative spread of gametophytes into neighbouring space and production of gemmae (asexual propagules) that disperse gametophytic clones to new sites [2].Gametophytes of dioecious bryophytes are unisexual, producing either eggs or sperm, but not both. Males and females compete for space but require close proximity for sexual reproduction. By contrast, gametophytes of monoecious bryophytes are bisexual, able to produce both eggs and sperm. A bisexual gametophyte that fertilizes its own eggs engenders homozygous sporophytes all of whose spores are genetically identical (excepting meiotic errors and postzygotic mutations). Roughly 70% of liverworts, 60% of mosses and 40% of hornworts are dioecious [3]. Bryophyte life cycles are not only fascinating in th...

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Biased Sex Ratios in Plants: Theory and Trends

Cited by 95 publications

References 75 publications

Influences of clonality on plant sexual reproduction

Influences of clonality on plant sexual reproduction

Population size, sex-ratio and sexual dimorphism in <em>Fuchsia parviflora</em> (Onagraceae) an endemic dioecious shrub

Living together and living apart: the sexual lives of bryophytes

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