scholarly journals Persistence of a Wolbachia-driven sex ratio bias in an island population of Eurema butterflies

2020 ◽  
Author(s):  
Daisuke Kageyama ◽  
Satoko Narita ◽  
Tatsuro Konagaya ◽  
Mai N. Miyata ◽  
Jun Abe ◽  
...  
Keyword(s):  
Sex Ratio ◽  
High Frequency ◽  
Sex Ratios ◽  
Female Offspring ◽  
Host Population ◽  
Island Population ◽  
Sex Ratio Bias ◽  
Negative Effect ◽  
Males And Females ◽  
Butterfly Population

AbstractIt is generally believed that when maternally inherited sex ratio distorters become predominant, either the host population goes extinct or nuclear suppressors evolve in the host. Here, we show an empirical case where all-female-producing Wolbachia is likely to be stably maintained at a high frequency. On an island population of the butterfly Eurema mandarina, a Wolbachia strain wFem, which makes female hosts produce all-female offspring without sibling lethality (female drive), is highly prevalent. We found that, with some fluctuations, wFem appeared to be stably maintained for at least 12 years at a high frequency, resulting in the existence of an abnormally high number of virgin females. Interestingly, comparison between sex ratios of captive individuals and sex ratios deduced from wFem frequencies suggested a plastic behavioral change of males and females in response to the shift of sex ratios. wFem presence does not affect brood size but has a slightly negative effect on body size. Stable coexistence of wFem-positive and -negative females in the population may be explained via mate choice by males, which keeps wFem in check. Taken together, this butterfly population is an attractive model for future studies on the population dynamics of sex ratios and mating behavior.

scholarly journals How do biases in sex ratio and disease characteristics affect the spread of sexually transmitted infections?

2020 ◽  
Author(s):  
Naerhulan Halimubieke ◽  
Alistair Pirrie ◽  
Tamás Székely ◽  
Ben Ashby
Keyword(s):  
Sex Ratio ◽  
Sexually Transmitted Infections ◽  
Sex Ratios ◽  
Population Level ◽  
Disease Prevalence ◽  
Host Population ◽  
Sexually Transmitted ◽  
Disease Characteristics ◽  
Adult Sex Ratio ◽  
Males And Females

AbstractThe epidemiology of sexually transmitted infections (STIs) is inherently linked to host mating dynamics. Studies across many taxa show that adult sex ratio, a major determinant of host mating dynamics, is often skewed - sometimes strongly - toward males or females. However, few predictions exist for the effects of skewed sex ratio on STI epidemiology, and none when coupled with sex biased disease characteristics. Here we use mathematical modelling to examine how interactions between sex ratio and disease characteristics affect STI prevalence in males and females. Notably, we find that while overall disease prevalence peaks at equal sex ratios, prevalence per sex peaks at skewed sex ratios. Furthermore, disease characteristics, sex-biased or not, drive predictable differences in male and female STI prevalence as sex ratio varies, with higher transmission and lower virulence generally increasing differences between the sexes for a given sex ratio. These findings may be due to a balance between increased per-capita mating in the less common sex, and a reduction in mating rate - hence disease prevalence - at the population level. Our work reveals new insights into how STI prevalence in males and females depends on a complex interaction between host population sex ratio and disease characteristics.

A new male-killing parasitism:Spiroplasmabacteria infect the ladybird beetleAnisosticta novemdecimpunctata(Coleoptera: Coccinellidae)

Parasitology ◽  
2006 ◽  
Vol 132 (6) ◽  
pp. 757-765 ◽  
Author(s):  
M. C. TINSLEY ◽  
M. E. N. MAJERUS
Keyword(s):  
Phylogenetic Analysis ◽  
Sex Ratio ◽  
High Efficiency ◽  
Sex Ratios ◽  
Egg Hatch ◽  
Hatch Rate ◽  
Male Killing ◽  
Offspring Sex ◽  
Novel Host ◽  
Males And Females

Whilst most animals invest equally in males and females when they reproduce, a variety of vertically transmitted parasites has evolved the ability to distort the offspring sex ratios of their hosts. One such group of parasites are male-killing bacteria. Here we report the discovery of females of the ladybirdAnisosticta novemdecimpunctatathat produced highly female-biased offspring sex ratios associated with a 50% reduction in egg hatch rate. This trait was maternally transmitted with high efficiency, was antibiotic sensitive and was infectious following experimental haemolymph injection. We identified the cause as a male-killingSpiroplasmabacterium and phylogenetic analysis of rDNA revealed that it belongs to theSpiroplasma ixodetisclade in which other sex ratio distorters lie. We tested the potential for interspecific horizontal transfer by injection from an infectedA. novemdecimpunctataline into uninfected individuals of the two-spot ladybirdAdalia bipunctata. In this novel host, the bacterium was able to establish infection, transmit vertically and kill male embryos.

scholarly journals Analysis of the sex ratio in Bradysia matogrossensis (Diptera, Sciaridae)

2000 ◽  
Vol 23 (1) ◽  
pp. 97-103 ◽  
Author(s):  
Lincoln S. Rocha ◽  
André Luiz P. Perondini
Keyword(s):  
Sex Ratio ◽  
Sex Determination ◽  
X Chromosome ◽  
Control Mechanism ◽  
Sex Ratios ◽  
Laboratory Strain ◽  
Chromosome Elimination ◽  
Common Control ◽  
Males And Females ◽  
Successive Generations

In sciarid flies, the control of sex determination and of the progeny sex ratio is exercised by the parental females, and is based on differential X-chromosome elimination in the initial stages of embryogenesis. In some species, the females produce unisexual progenies (monogenic females) while in others, the progenies consist of males and females (digenic females). The sex ratio of bisexual progenies is variable, and departs considerably from 1:1. Bradysia matogrossensis shows both monogenic and digenic reproduction. In a recently established laboratory strain of this species, 15% of the females were digenic, 10% produced only females, 13% produced only males, and 62% produced progenies with one predominant sex (33% predominantly of female and 29% predominantly male progenies). These progeny sex ratios were maintained in successive generations. Females from female-skewed progenies yielded female- and male-producing daughters in a 1:1 ratio. In contrast, daughters of females from male-skewed progenies produce bisexual or male-skewed progenies. The X-chromosome of B. matogrossensis shows no inversion or other gross aberration. These results suggest that the control of the progeny sex ratio (or differential X-chromosome elimination) involves more than one locus or, at least, more than one pair of alleles. The data also suggest that, in sciarid flies, monogeny and digeny may share a common control mechanism.

scholarly journals Recruitment sex ratios in gray-tailed voles (Microtus canicaudus) in response to density, sex ratio, and season

2003 ◽  
Vol 81 (8) ◽  
pp. 1306-1311 ◽  
Author(s):  
Monica L Bond ◽  
Jerry O Wolff ◽  
Sven Krackow
Keyword(s):  
Population Density ◽  
Sex Ratio ◽  
Resource Competition ◽  
Sex Ratios ◽  
Female Offspring ◽  
High Population ◽  
Reproductive Value ◽  
High Population Density ◽  
Adult Sex Ratio ◽  
Sex Ratio Adjustment

We tested predictions associated with three widely used hypotheses for facultative sex-ratio adjustment of vertebrates using eight enclosed populations of gray-tailed voles, Microtus canicaudus. These were (i) the population sex ratio hypothesis, which predicts that recruitment sex ratios should oppose adult sex-ratio skews, (ii) the local resource competition hypothesis, which predicts female-biased recruitment at low adult population density and male-biased recruitment at high population density, and (iii) the first cohort advantage hypothesis, which predicts that recruitment sex ratios should be female biased in the spring and male biased in the autumn. We monitored naturally increasing population densities with approximately equal adult sex ratios through the spring and summer and manipulated adult sex ratios in the autumn and measured subsequent sex ratios of recruits. We did not observe any significant sex-ratio adjustment in response to adult sex ratio or high population density; we did detect an influence of time within the breeding season, with more female offspring observed in the spring and more male offspring observed in the autumn. Significant seasonal increases in recruitment sex ratios indicate the capacity of female gray-tailed voles to manipulate their offspring sex ratios and suggest seasonal variation in the relative reproductive value of male and female offspring to be a regular phenomenon.

scholarly journals Consistent sex ratio bias of individual female dragon lizards

2006 ◽  
Vol 2 (4) ◽  
pp. 569-572 ◽  
Author(s):  
Tobias Uller ◽  
Beth Mott ◽  
Gaetano Odierna ◽  
Mats Olsson
Keyword(s):  
Genetic Variation ◽  
Sex Ratio ◽  
Incubation Temperature ◽  
Sex Ratios ◽  
Phenotypic Traits ◽  
Female Size ◽  
Offspring Sex Ratio ◽  
Phenotypic Differences ◽  
Sex Ratio Bias ◽  
Offspring Sex

Sex ratio evolution relies on genetic variation in either the phenotypic traits that influence sex ratios or sex-determining mechanisms. However, consistent variation among females in offspring sex ratio is rarely investigated. Here, we show that female painted dragons ( Ctenophorus pictus ) have highly repeatable sex ratios among clutches within years. A consistent effect of female identity could represent stable phenotypic differences among females or genetic variation in sex-determining mechanisms. Sex ratios were not correlated with female size, body condition or coloration. Furthermore, sex ratios were not influenced by incubation temperature. However, the variation among females resulted in female-biased mean population sex ratios at hatching both within and among years.

scholarly journals Sperm sex ratio adjustment in a mammal: perceived male competition leads to elevated proportions of female-producing sperm

2020 ◽  
Vol 16 (6) ◽  
pp. 20190929
Author(s):  
Renée C. Firman ◽  
Jamie N. Tedeschi ◽  
Francisco Garcia-Gonzalez
Keyword(s):  
Sex Ratio ◽  
Sex Allocation ◽  
Sex Ratios ◽  
Female Offspring ◽  
Male Competition ◽  
Offspring Sex ◽  
Sex Ratio Adjustment ◽  
Adaptive Adjustment ◽  
Male House

Mammal sex allocation research has focused almost exclusively on maternal traits, but it is now apparent that fathers can also influence offspring sex ratios. Parents that produce female offspring under conditions of intense male–male competition can benefit with greater assurance of maximized grand-parentage. Adaptive adjustment in the sperm sex ratio, for example with an increase in the production of X-chromosome bearing sperm (CBS), is one potential paternal mechanism for achieving female-biased sex ratios. Here, we tested this mechanistic hypothesis by varying the risk of male–male competition that male house mice perceived during development, and quantifying sperm sex ratios at sexual maturity. Our analyses revealed that males exposed to a competitive ‘risk’ produced lower proportions of Y-CBS compared to males that matured under ‘no risk’ of competition. We also explored whether testosterone production was linked to sperm sex ratio variation, but found no evidence to support this. We discuss our findings in relation to the adaptive value of sperm sex ratio adjustments and the role of steroid hormones in socially induced sex allocation.

Estimating the Frequency of Constrained Sex Allocation in Field Populations of Hymenoptera

Behaviour ◽  
1990 ◽  
Vol 114 (1-4) ◽  
pp. 137-147 ◽  
Author(s):  
H.C.J. Godfray ◽  
I.C.W. Hardy
Keyword(s):  
Sex Ratio ◽  
Sex Allocation ◽  
Sex Ratios ◽  
Parasitoid Species ◽  
Ratio Bias ◽  
Sex Ratio Bias ◽  
Sex Ratio Theory

Abstract1) Sex ratio theory has assumed that females can produce offspring of both sexes. It has been suggested that some females in haplodiploid populations are only able to produce sons (constrained sex allocation), for example because they are virgin. The presence of such females influences the optimal sex ratio of unconstrained females. The relevance of these ideas to field sex ratios is largely untested. 2) The frequencies of constrained oviposition in three Drosophila parasitoid species are estimated. Constrained, ovipositing females were distinguished by the absence of sperm in the spermatheca. Constrained females were absent or rare in these species. 3) We review data from the literature that allow an estimate of the frequency of constrained females. 4) We conclude that the available evidence suggests that while constrained oviposition is uncommon, there are some species in which constrained females are sufficiently common to select for an observable sex ratio bias by unconstrained females.

scholarly journals Effect of exposure time of pregnant females guppies, Poecilia reticulata Peters, in 17a-methyltestosterone solution on sex ratio of their offsprings

2007 ◽  
Vol 1 (1) ◽  
pp. 47
Author(s):  
M. Zairin Junior ◽  
A. Yunianti ◽  
R.R.S.P.S. Dewi ◽  
Kusman Sumawidjaja
Keyword(s):  
Sex Ratio ◽  
Exposure Time ◽  
Treatment Duration ◽  
Poecilia Reticulata ◽  
Female Offspring ◽  
Control Group ◽  
Time Interval ◽  
Water Flea ◽  
Pregnant Females ◽  
Males And Females

<p>ABSTRACT</p><p>This experiment was carried out to study the effect of female broodstocks immersion in 17amethyltestosterone (MT) solution on sex ratio of their offspring, Three-months old males and females were paired to mate in aquaria for four days.  Broodstocks were fed with frozen blood worm and water flea 2-3 tii-nes daily.  Twelve days after mating, female broodstock were treated by immersing in 2 mg/1 MT solution for 0. 6, 12, 24 and 48 hours.  Birthed guppy babies were collected and reared separately from their parents.  During the rearing period, the babies were fed with artemia nauplius and silkworm until identification for male and female.  Percentage of female offspring in control group were higher than those of male.  Exposure of pregnant females to MT solution for 0, 6, 12, 24, and 48 hours resulted in 42, 1'/o, 51%, 84,6%, 1 00%, dan 100% of males offspring, respectively.  The best result was obtained from 24 hours treatment.  Longer treatment duration tend to shorten time interval between treatment and birth. Key words :  Guppy, 17(x-methyltestosterone, exposure time, broodstock immersion, sex ratio   ABSTRAK Penefitian ini bertuiuan untuk mengetahui pengaruh lama waktu perendaman induk di dalam larutan hormon 17a-metiltestosteron (MT) terhadap nisbah kelamin ikan gapi.  Induk Ikan gapi berumur tiga bulan dikawinkan berpasangan di dalam akuarium selama empat hari Induk diberi pakan cuk merah beku dan kutu air dengan frekuensi 2-3 kali sehari.  Dua belas hari setelah masa perkawinan, induk betina diberi perlakuan berupa perendaman di dalam larutan MT 2 mg/1 selama 0 (kontrol), 6, 12, 24, dan 48 jam.  Anak-anak ikan gapi yang baru lahir dipelihara terpisah dari induknya.  Selama masa pemeliharaan, anak ikan gapi diberi pakan nauplius artemia dan cacing rambut.  Pemeliharaan berlangsung sampai jenis kelamin anak ikan gapi dapat diidentifikasi.  Persentase anak ikan gapi betina pada semua ulangan kontrol lebih tinggi daripada .iantan dengan perbandingan persentase rata-rata 57,9%: 42,1%.  Adapun pada lama waktu perendaman 0, 6, 12, 24, dan 48 jam, menghasilkan persentase anak ikan gapi berfenotip jantan berturut-turut sebesar 42,1%, 51%, 84,6%, 100%, dan 100%.  Lama waktu perendaman terbaik adalah 24 jam.  Selain itu terdapat kecenderungan bahwa semakin lama waktu perendaman semakin cepat kelahirannya. Kata kunci :  Ikan gapi, 17ot-metiltestosteron, lama perendaman, perendaman induk, nisbah kelamin</p>

scholarly journals Seed sexing revealed female bias in two Rumex species

2011 ◽  
Vol 80 (2) ◽  
pp. 93-97 ◽  
Author(s):  
Dagmara Kwolek ◽  
Andrzej J. Joachimiak
Keyword(s):  
Sex Ratio ◽  
Sex Chromosomes ◽  
Dna Markers ◽  
Sex Chromosome ◽  
Sex Ratios ◽  
Ratio Bias ◽  
Sex Ratio Bias ◽  
Y Chromosomes ◽  
Sex Chromosome System ◽  
Female Bias

Sex-ratio bias in seeds of dioecious <em>Rumex</em> species with sex chromosomes is an interesting and still unsettled issue. To resolve gender among seeds of <em>R. acetosa</em> and <em>R. thyrsiflorus</em> (two species with an XX/XY1Y2 sex chromosome system), this work applied a PCR-based method involving DNA markers located on Y chromosomes. Both species showed female-biased primary sex ratios, with female bias greater in <em>R. acetosa</em> than in <em>R. thyrsiflorus</em>. The observed predominance of female seeds is consistent with the view that the female biased sex ratios in <em>Rumex </em>are conditioned not only postzygotically but also prezygotically.

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