scholarly journals Meiotic sex ratio variation in natural populations of Ceratodon purpureus (Ditrichaceae)

2014 ◽  
Vol 101 (9) ◽  
pp. 1572-1576 ◽  
Author(s):  
T. E. Norrell ◽  
K. S. Jones ◽  
A. C. Payton ◽  
S. F. McDaniel
Keyword(s):  
Sex Ratio ◽  
Natural Populations ◽  
Ceratodon Purpureus ◽  
Ratio Variation

scholarly journals Sex ratio variation shapes the ecological effects of a globally introduced freshwater fish

2015 ◽  
Vol 282 (1817) ◽  
pp. 20151970 ◽  
Author(s):  
David C. Fryxell ◽  
Heather A. Arnett ◽  
Travis M. Apgar ◽  
Michael T. Kinnison ◽  
Eric P. Palkovacs
Keyword(s):  
Sexual Dimorphism ◽  
Sex Ratio ◽  
Evolutionary Ecology ◽  
Natural Populations ◽  
Trophic Cascades ◽  
Zooplankton Abundance ◽  
Sexually Dimorphic ◽  
Ecosystem Responses ◽  
Ratio Variation

Sex ratio and sexual dimorphism have long been of interest in population and evolutionary ecology, but consequences for communities and ecosystems remain untested. Sex ratio could influence ecological conditions whenever sexual dimorphism is associated with ecological dimorphism in species with strong ecological interactions. We tested for ecological implications of sex ratio variation in the sexually dimorphic western mosquitofish, Gambusia affinis . This species causes strong pelagic trophic cascades and exhibits substantial variation in adult sex ratios. We found that female-biased populations induced stronger pelagic trophic cascades compared with male-biased populations, causing larger changes to key community and ecosystem responses, including zooplankton abundance, phytoplankton abundance, productivity, pH and temperature. The magnitude of such effects indicates that sex ratio is important for mediating the ecological role of mosquitofish. Because both sex ratio variation and sexual dimorphism are common features of natural populations, our findings should encourage broader consideration of the ecological significance of sex ratio variation in nature, including the relative contributions of various sexually dimorphic traits to these effects.

Sex Ratio Variation in the Intertidal Isopod, Jaera Albifrons

1996 ◽  
Vol 76 (3) ◽  
pp. 825-828 ◽  
Author(s):  
Stuart B. Piertney ◽  
Gary R. Carvalho
Keyword(s):  
Environmental Factors ◽  
Sex Ratio ◽  
Natural Populations ◽  
Light Regimes ◽  
Ratio Bias ◽  
Sex Ratio Bias ◽  
Ratio Variation ◽  
South Wales

Thirty ‘rock-populations’ of the intertidal isopod, Jaera albifrons (Isopoda: Asellota), from South Wales area were found to display a significant and persistent sex ratio bias, with females outnumbering males by up to 12 to 1. This thelygeny was not mirrored in broods that were isolated in aquaria after insemination, nor in broods that developed under various temperature and light regimes. Such a discrepancy suggests that the mechanism generating sex ratio biases in natural populations is not innate, nor is influenced by cytoplasmic or environmental factors. The possible causes of thelygeny in natural populations are discussed.

scholarly journals Sex expression and genotypic sex ratio vary with region and environment in the wetland moss Drepanocladus lycopodioides

2019 ◽  
Vol 192 (2) ◽  
pp. 421-434
Author(s):  
Irene Bisang ◽  
Johan Ehrlén ◽  
Lars Hedenäs
Keyword(s):  
Sex Ratio ◽  
Life Histories ◽  
Sex Chromosome ◽  
Sex Ratios ◽  
Natural Populations ◽  
Environmental Parameters ◽  
Sex Expression ◽  
Ratio Variation ◽  
Female Flowering ◽  
Female Bias

Abstract Sex ratio variation is common among organisms with separate sexes. In bryophytes, sex chromosome segregation at meiosis suggests a balanced progeny sex ratio. However, most bryophyte populations exhibit female-biased phenotypic sex ratios based on the presence of reproductive structures on gametophytes. Many bryophyte populations do not form sexual organs, and genotypic sex ratio variation in such populations is mostly unknown. We tested sex expression, and phenotypic and genotypic sex ratios against environmental parameters in natural populations of the unisexual wetland moss Drepanocladus lycopodiodes at 11 sites in each of three regions in southern Sweden. We identified sex in 660 individual ramets, based on sexual structures, when present, or with a specifically designed molecular marker, when absent. All regions exhibited a female bias in phenotypic and genotypic sex ratios. Sex ratio biases and sex expression differed between regions. Sex ratios were less female-biased in larger patches. Wetter patches exhibited a stronger female bias in genotypic sex ratio and lower sex expression. This is the first evidence of environmental effects on genotypic sex ratio in mosses. A higher frequency of females in wet patches could be due to higher female resource demands for sporophyte production or higher male sensitivity to wetness. A higher incidence of females than males in moister sites aligns with female flowering plants, but differs from reproductive bryophytes in drier environments. Taken together with previous results, our data indicate that sex ratio variation and its drivers differ among species, their life histories and environments.

scholarly journals Natural variation in social conditions affects male mate choosiness in the amphipod Gammarus roeselii

2021 ◽  
Author(s):  
Konrad Lipkowski ◽  
Sophie Steigerwald ◽  
Lisa M Schulte ◽  
Carolin Sommer-Trembo ◽  
Jonas Jourdan
Keyword(s):  
Population Density ◽  
Sex Ratio ◽  
Natural Variation ◽  
Natural Populations ◽  
Social Background ◽  
Social Conditions ◽  
Background Information ◽  
Male Mating ◽  
Natural Environments ◽  
Male Mate

Abstract The extent of male mate choosiness is driven by a trade-off between various environmental factors associated with the costs of mate acquisition, quality assessment and opportunity costs. Our knowledge about natural variation in male mate choosiness across different populations of the same species, however, remains limited. In this study, we compared male mate choosiness across 10 natural populations of the freshwater amphipod Gammarus roeselii (Gervais 1835), a species with overall high male mating investments, and evaluated the relative influence of population density and sex ratio (both affecting mate availability) on male mate choosiness. We investigated amplexus establishment after separating mating pairs and presenting focal males with a novel, size-matched female from the same population. Our analysis revealed considerable effects of sex ratio and (to a lesser extent) population density on time until amplexus establishment (choosiness). Male amphipods are able to perceive variable social conditions (e.g., sex ratio) and modify their mating strategy accordingly: We found choosiness to be reduced in increasingly male-biased populations, whereas selectivity increases when sex ratio becomes female biased. With this, our study expands our limited knowledge on natural variations in male mate choosiness and illustrates the importance of sex ratio (i.e., level of competition) for male mating decisions in natural environments. Accounting for variation in sex ratios, therefore, allows envisioning a distinctive variation of choosiness in natural populations and highlights the importance of considering social background information in future behavioral studies.

scholarly journals Sex Chromosome Meiotic Drive in Stalk-Eyed Flies

Genetics ◽  
1997 ◽  
Vol 147 (3) ◽  
pp. 1169-1180 ◽  
Author(s):  
Daven C Presgraves ◽  
Emily Severance ◽  
Gerald S Willrinson
Keyword(s):  
Sex Ratio ◽  
Sex Chromosome ◽  
Sex Ratios ◽  
Natural Populations ◽  
Meiotic Drive ◽  
Operational Sex Ratio ◽  
Genetic Modifiers ◽  
Ratio Distortion ◽  
The Impact ◽  
Sex Ratio Distortion

Meiotically driven sex chromosomes can quickly spread to fixation and cause population extinction unless balanced by selection or suppressed by genetic modifiers. We report results of genetic analyses that demonstrate that extreme female-biased sex ratios in two sister species of stalk-eyed flies, Cyrtodiopsis dalmanni and C. whitei, are due to a meiotic drive element on the X chromosome (Xd). Relatively high frequencies of Xd in C. dalmanni and C. whitei (13–17% and 29%, respectively) cause female-biased sex ratios in natural populations of both species. Sex ratio distortion is associated with spermatid degeneration in male carriers of Xd. Variation in sex ratios is caused by Y-linked and autosomal factors that decrease the intensity of meiotic drive. Y-linked polymorphism for resistance to drive exists in C. dalmanni in which a resistant Y chromosome reduces the intensity and reverses the direction of meiotic drive. When paired with Xd, modifying Y chromosomes (Ym) cause the transmission of predominantly Y-bearing sperm, and on average, production of 63% male progeny. The absence of sex ratio distortion in closely related monomorphic outgroup species suggests that this meiotic drive system may predate the origin of C. whitei and C. dalmanni. We discuss factors likely to be involved in the persistence of these sex-linked polymorphisms and consider the impact of Xd on the operational sex ratio and the intensity of sexual selection in these extremely sexually dimorphic flies.

scholarly journals Population sex ratio variation in a monogamous long-lived bird, the wandering albatross

2005 ◽  
Vol 74 (2) ◽  
pp. 285-291 ◽  
Author(s):  
HENRI WEIMERSKIRCH ◽  
JOELLE LALLEMAND ◽  
JULIEN MARTIN
Keyword(s):  
Sex Ratio ◽  
Ratio Variation ◽  
Wandering Albatross
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