SEX RATIO OF<i>RUMEX HASTATULUS:</i>THE EFFECT OF ENVIRONMENTAL FACTORS AND CERTATION

Conn, Jeffery S.; Blum, Udo

doi:10.1111/j.1558-5646.1981.tb04980.x

Cited by 36 publications

(16 citation statements)

References 28 publications

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“…Similar to several other dioecious species of Rumex with sex chromosomes (7,(21)(22)(23)(24), there is evidence that progeny sex ratios are also influenced by nongenetic factors, specifically the amount of pollen deposited on stigmas. By experimentally manipulating the distance between male pollen donors and female recipients of R. nivalis in a common garden, Stehlik and Barrett (25) demonstrated that seed sex ratios were dependent on the specific maternal pollination environment.…”

supporting

confidence: 52%

“…Females at closer distances to males had higher stigmatic pollen loads and produced more strongly female-biased seed sex ratios compared with more distant females. However, attempts to demonstrate relations between male proximity and progeny sex ratios have been inconclusive in other Rumex species (23,24), and the role of maternal pollination environment in affecting progeny sex ratios in natural populations has not been investigated.Here we investigate whether the composition of the local mating neighborhood in natural populations of dioecious R. nivalis influences progeny sex ratios. Under the certation hypothesis, progeny sex ratios of maternal parents of R. nivalis located in close proximity to males should be more female-biased as a result of higher pollen loads, leading to increased competition between female-versus male-determining pollen tubes.…”

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confidence: 99%

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Environmental influence on primary sex ratio in a dioecious plant

Stehlik

Friedman²,

Barrett

2008

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

102

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The proximity of mates can influence mating opportunities and the quantity and quality of offspring, especially in dioecious plant species. Progeny sex ratios modulated by environmental conditions is one of the most radical ways in which offspring quality may be influenced, yet it has rarely been reported in plants. A mechanism proposed to influence progeny sex ratios in dioecious plants involves competition between female-and male-determining microgametophytes (certation) as a result of variation in pollination intensity. However, the role of selective fertilization in dioecious plants is controversial and has not been demonstrated under field conditions. Here we investigate whether natural variation in the spatial arrangement of females and males influences pollination intensity and progeny sex ratios in the wind-pollinated herb Rumex nivalis. Based on previous experimental manipulation of pollination intensity in this species, we predicted that maternal parents in close proximity to males would produce more strongly female-biased progeny sex ratios. We tested this prediction in six alpine populations in Switzerland by measuring the distance between focal females and neighboring males and assessing pollen loads and seed sex ratios of maternal parents. In four of the six populations, females positioned in close proximity to males captured more pollen and exhibited more female-biased sex ratios. Our results demonstrate that demographic aspects of the maternal mating environment can influence progeny sex ratios. The most probable explanation for biased primary sex ratios in Rumex is selective fertilization resulting from pollen tube competition.female-biased sex ratios ͉ pollination intensity ͉ selective fertilization T he spatial context in which reproduction occurs is of critical importance for plants because of their sessile habit. Most plants mate and disperse offspring locally, so that mating success is context-dependent and influenced by plant density and the phenotypic composition of neighborhoods (1-3). Dioecious species are especially sensitive to spatial structure and composition because of the restricted number of mating groups within populations. Female reproductive success can be influenced by male flowering density, depending on the extent of pollen dispersal (4-6). Patch density and the local sex ratio may also affect parental fitness through their influence on pollination intensity. The amount of pollen captured by stigmas could potentially affect both the quality of offspring and progeny sex ratios through gametophytic competition (certation) and selective fertilization (7,8). However, the relative roles of genetic and environmental factors in governing primary sex ratios in dioecious populations are still poorly understood, and evidence for environmentally induced variation in primary sex ratios is limited despite considerable heterogeneity in seed sex ratios (9).Sex determination induced by the environment is one of the most direct ways in which progeny sex ratios can vary. Environmental sex de...

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supporting

confidence: 52%

mentioning

confidence: 99%

Environmental influence on primary sex ratio in a dioecious plant

Stehlik

Friedman²,

Barrett

2008

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

102

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“…When this competition was particularly intense, for example, when pollen was very abundant, the competitive inferiority of the Y-bearing pollen was manifested as an increasing femalebiased sex ratio. Since Correns's (1917Correns's ( , 1928 work, pollen competition has been shown to influence the sex ratio in other plant species (Smith 1963;Conn and Blum 1981), especially those with chromosomal (i.e., X/Y) sex-determination mechanisms (Lloyd 1974). More recently, however, Correns's original results have proven difficult to reproduce (Carroll and Mulcahy 1993;Purrington 1993;Lassere et al 1996).…”

Section: Pollen Competition and The Sex Ratiomentioning

confidence: 99%

“…The results identify the ecological conditions under which sex-linked genes are most likely to realize a transmission advantage via sex-ratio distortion. We also address the long-standing hypothesis that pollen competition is the direct cause of sexratio bias in many plant species (Correns 1928;Smith 1963;Conn and Blum 1981;Carroll and Mulcahy 1993;Lassere et al 1996).…”

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Pollen Performance and Sex‐ratio Evolution in a Dioecious Plant

1999

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Abstract.-There has been a proliferation of studies, in a variety of taxa, that have detected sex-linked or cytoplasmic genes that enhance their own transmission via sex-ratio distortion. One of the most important parameters influencing the dynamics of these elements is the magnitude of their transmission advantage. In many systems, the mechanism of sex-ratio distortion is to abort X-or Y-bearing gametes. With this mechanism, the transmission advantage associated with sex-ratio distortion is diminished when the production of male gametes limits offspring production or when competition among the gametes of different males is intense. In this study, we analyzed the outcome of pollen competition between males that produced different sex ratios in the dioecious plant, Silene alba, and estimated how the sex-ratio bias influenced the transmission properties of the sex chromosomes. We varied the intensity of pollen competition by controlling the quantity of pollen used in crosses and used a combination of single-male pollinations and pollen mixtures to evaluate the effects of multiple paternity. Paternity in pollen mixtures was estimated using allozymes. Sex-ratio bias was directly influenced by the quantity of pollen, but the magnitude of this effect was small. The relative performance of pollen from different males varied substantially, especially when there was multiple paternity. Specifically, males with biased sex ratios sired far fewer offspring of either sex in pollen mixtures. In crosses involving single males, however, these "sex-ratio" males produced the same number of offspring as other males, so the female bias caused a significant transmission advantage for X-linked genes. X-linked genes could enhance their transmission via sex-ratio distortion in Silene populations, but the magnitude of this transmission advantage will depend on the ecological circumstances that influence the opportunity for multiple paternity.

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“…Furthermore, competition can be manipulated by varying the amount of pollen deposited, which significantly affects siring proportions in some species (e.g., Cucurbita pepo) but not others (9,25). In dioecious Rumex, the amount of pollen deposited alters the relative success of X-and Y-bearing gametophytes and hence the resulting sex ratio (26,27). A recent genomic analysis of fixed and polymorphic sites in Arabidopsis thaliana found evidence of both stronger purifying selection and more extensive positive selection among pollen-expressed genes than among randomly chosen genes (28).…”

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confidence: 99%

Evolution of haploid selection in predominantly diploid organisms

Otto

Scott

Immler

2015

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

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Diploid organisms manipulate the extent to which their haploid gametes experience selection. Animals typically produce sperm with a diploid complement of most proteins and RNA, limiting selection on the haploid genotype. Plants, however, exhibit extensive expression in pollen, with actively transcribed haploid genomes.Here we analyze models that track the evolution of genes that modify the strength of haploid selection to predict when evolution intensifies and when it dampens the "selective arena" within which male gametes compete for fertilization. Considering deleterious mutations, evolution leads diploid mothers to strengthen selection among haploid sperm/pollen, because this reduces the mutation load inherited by their diploid offspring. If, however, selection acts in opposite directions in haploids and diploids ("ploidally antagonistic selection"), mothers evolve to reduce haploid selection to avoid selectively amplifying alleles harmful to their offspring. Consequently, with maternal control, selection in the haploid phase either is maximized or reaches an intermediate state, depending on the deleterious mutation rate relative to the extent of ploidally antagonistic selection. By contrast, evolution generally leads diploid fathers to mask mutations in their gametes to the maximum extent possible, whenever masking (e.g., through transcript sharing) increases the average fitness of a father's gametes. We discuss the implications of this maternal-paternal conflict over the extent of haploid selection and describe empirical studies needed to refine our understanding of haploid selection among seemingly diploid organisms.pollen competition | antagonistic selection | haploid selection | sperm competition | evolutionary theory

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SEX RATIO OFRUMEX HASTATULUS:THE EFFECT OF ENVIRONMENTAL FACTORS AND CERTATION

Cited by 36 publications

References 28 publications

Environmental influence on primary sex ratio in a dioecious plant

Environmental influence on primary sex ratio in a dioecious plant

Pollen Performance and Sex‐ratio Evolution in a Dioecious Plant

Evolution of haploid selection in predominantly diploid organisms

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