scholarly journals Flow cytometric sexing of spider sperm reveals an equal sperm production ratio in a female-biased species

2014 ◽  
Vol 10 (5) ◽  
pp. 20140159 ◽  
Author(s):  
B. Vanthournout ◽  
K. Deswarte ◽  
H. Hammad ◽  
T. Bilde ◽  
B. Lambrecht ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Sex Allocation ◽  
Evolutionarily Stable Strategy ◽  
General Rule ◽  
Sperm Cells ◽  
Sperm Production ◽  
Male And Female ◽  
Ratio Bias ◽  
Sex Ratio Bias ◽  
Production Ratio

Producing equal amounts of male and female offspring has long been considered an evolutionarily stable strategy. Nevertheless, exceptions to this general rule (i.e. male and female biases) are documented in many taxa, making sex allocation an important domain in current evolutionary biology research. Pinpointing the underlying mechanism of sex ratio bias is challenging owing to the multitude of potential sex ratio-biasing factors. In the dwarf spider, Oedothorax gibbosus , infection with the bacterial endosymbiont Wolbachia results in a female bias. However, pedigree analysis reveals that other factors influence sex ratio variation. In this paper, we investigate whether this additional variation can be explained by the unequal production of male- and female-determining sperm cells during sperm production. Using flow cytometry, we show that males produce equal amounts of male- and female-determining sperm cells; thus bias in sperm production does not contribute to the sex ratio bias observed in this species. This demonstrates that other factors such as parental genes suppressing endosymbiont effects and cryptic female choice might play a role in sex allocation in this species.

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 Haploid selection, sex ratio bias, and transitions between sex-determining systems

2018 ◽  
Author(s):  
Michael Francis Scott ◽  
Matthew Miles Osmond ◽  
Sarah Perin Otto
Keyword(s):  
Sex Ratio ◽  
Sex Determination ◽  
Sex Chromosomes ◽  
Pollen Competition ◽  
Diploid Males ◽  
Mendelian Segregation ◽  
Male And Female ◽  
Ratio Bias ◽  
Sex Ratio Bias ◽  
Haploid Selection

AbstractSex determination is remarkably dynamic; many taxa display shifts in the location of sex-determining loci or the evolution of entirely new sex-determining systems. Predominant theories for why we observe such transitions generally conclude that novel sex-determining systems are favoured by selection if they equalise the sex ratio or increase linkage with a locus that experiences different selection in males vs. females. We use population genetic models to extend these theories in two ways: (1) We consider the dynamics of loci very tightly linked to the ancestral sex-determining loci, e.g., within the non-recombining region of the ancestral sex chromosomes. Variation at such loci can favour the spread of new sex-determining systems in which the heterogametic sex changes (XY to ZW or ZW to XY) and the new sex-determining region is less closely linked (or even unlinked) to the locus under selection. (2) We consider selection upon haploid genotypes either during gametic competition (e.g., pollen competition) or meiosis (i.e., non-Mendelian segregation), which can cause the zygotic sex ratio to become biased. Haploid selection can drive transitions between sex-determining systems without requiring selection to act differently in diploid males vs. females. With haploid selection, we find that transitions between male and female heterogamety can evolve where linkage with the sex-determining locus is either strengthened or weakened. Furthermore, we find that sex-ratio biases may increase or decrease with the spread of new sex chromosomes, which implies that transitions between sex-determining systems cannot be simply predicted by selection to equalise the sex ratio. In fact, under many conditions, we find that transitions in sex determination are favoured equally strongly in cases where the sex ratio bias increases or decreases. Overall, our models predict that sex determination systems should be highly dynamic, particularly when haploid selection is present, consistent with the evolutionary lability of this trait in many taxa.Author summarySystems of sex determination are strikingly diverse and labile in many clades. This poses the question: what drives transitions between sex-determining systems? Here, we use models to derive conditions under which new sex-determining systems spread. Prevailing views suggest that new sex-determining systems are favoured when they equalize the sex ratio and/or when they are more closely linked to genes that experience differential selection in males and females. Our models include selection upon haploid genotypes (meiotic drive or gametic competition), which biases the sex-ratio and occurs differently in male and female gametes. Surprisingly, we find the two forces (selection to equalize the sex ratio and the benefits of hitchhiking alongside driven alleles that distort the sex ratio) will often be equally strong, and thus neither is sufficient to explain the spread of new sex-determining systems in every case. We also find that new sex-determining alleles can spread despite being less closely linked to selected loci as long as initial linkage is tight or haploid selection is present. Our models therefore predict that loci in previously unexpected genomic locations and/or experiencing various types of selection (including haploid selection) can now be implicated as drivers of transitions between sex-determining systems.

Parental sex allocation and sex-specific survival drive offspring sex ratio bias in little owls

2019 ◽  
Vol 73 (6) ◽  
Author(s):  
Matthias Tschumi ◽  
Jolanda Humbel ◽  
Joscha Erbes ◽  
Julien Fattebert ◽  
Jochen Fischer ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Sex Allocation ◽  
Offspring Sex Ratio ◽  
Ratio Bias ◽  
Sex Ratio Bias ◽  
Offspring Sex

CULTURAL INHERITANCE AS A MECHANISM FOR POPULATION SEX-RATIO BIAS IN REPTILES

Evolution ◽  
2007 ◽  
Vol 55 (5) ◽  
pp. 1049-1055 ◽  
Author(s):  
Steven Freedberg ◽  
Michael J. Wade
Keyword(s):  
Sex Ratio ◽  
Cultural Inheritance ◽  
Ratio Bias ◽  
Sex Ratio Bias

Behavioral variation in nesting phenology may offset sex-ratio bias in tuatara

2018 ◽  
Vol 329 (6-7) ◽  
pp. 373-381 ◽  
Author(s):  
Nicola J. Nelson ◽  
Susan N. Keall ◽  
Jeanine M. Refsnider ◽  
Anna L. Carter
Keyword(s):  
Sex Ratio ◽  
Behavioral Variation ◽  
Ratio Bias ◽  
Sex Ratio Bias

Translocation reverses birth sex ratio bias depending on its timing during gestation: evidence for the action of two sex-allocation mechanisms

2007 ◽  
Vol 19 (7) ◽  
pp. 831 ◽  
Author(s):  
W. L. Linklater
Keyword(s):  
Glucose Metabolism ◽  
Sex Ratio ◽  
Sex Allocation ◽  
Preimplantation Embryo ◽  
Sex Ratio Bias ◽  
In Captivity ◽  
Developmental Asynchrony ◽  
Adjustment Mechanisms ◽  
Excess Glucose

Many sex allocation mechanisms are proposed but rarely have researchers considered and tested more than one at a time. Four facultative birth sex ratio (BSR) adjustment mechanisms are considered: (1) hormone-induced conception bias; (2) sex-differential embryo death from excess glucose metabolism; (3) sex-differential embryo death from embryo–uterine developmental asynchrony; and (4) pregnancy hormone suppression and resource deprivation. All mechanisms could be switched on by the corticoadrenal stress response. A total of 104 female rhinoceroses (Rhinocerotidae), translocated from 1961 to 2004 at different stages of gestation or conceived soon after arrival in captivity, were used to test for a reversal in BSR bias as evidence for the action of multiple sex-allocation mechanisms. Translocation induced a statistically significant BSR reversal between early gestation (86% male births from 0 to 0.19 gestation) and mid-gestation (38% male from 0.2 to 0.79 gestation). Captivity also induced a strongly male-biased (67% male) BSR for conceptions after arrival in captivity. The results indicate the action of at least two sex-allocation mechanisms operating in sequence, confirm the important role of sex-differential embryo death around implantation and of stress in sex allocation, and lend support to suggestions that sex-differential glucose metabolism by the preimplantation embryo likely plays a role in facultative BSR adjustment.

scholarly journals Mate limitation and sex ratio evolution

2018 ◽  
Vol 5 (2) ◽  
pp. 171135 ◽  
Author(s):  
Jussi Lehtonen ◽  
Lisa E. Schwanz
Keyword(s):  
Sex Ratio ◽  
Kin Selection ◽  
Sex Allocation ◽  
Evolutionarily Stable Strategy ◽  
Mathematical Relationship ◽  
Stable Strategy ◽  
Local Mate ◽  
Mate Limitation ◽  
Mating Function ◽  
Evolutionarily Stable

Sex ratio evolution has been one of the most successful areas of evolutionary theory. Pioneered by Düsing and Fisher under panmixia, and later extended by Hamilton to cover local mate competition (LMC), these models often assume, either implicitly or explicitly, that all females are fertilized. Here, we examine the effects of relaxing this assumption, under both panmictic and LMC models with diploid genetics. We revisit the question of the mathematical relationship between sex ratio and probability of fertilization, and use these results to model sex ratio evolution under risk of incomplete fertilization. We find that (i) under panmixia, mate limitation has no effect on the evolutionarily stable strategy (ESS) sex allocation; (ii) under LMC, mate limitation can make sex allocation less female-biased than under complete fertilization; (iii) contrary to what is occasionally stated, a significant fraction of daughters can remain unfertilized at the ESS in LMC with mate limitation; (iv) with a commonly used mating function, the fraction of unfertilized daughters can be quite large, and (v) with more realistic fertilization functions, the deviation becomes smaller. The models are presented in three equivalent forms: individual selection, kin selection and group selection. This serves as an example of the equivalence of the methods, while each approach has their own advantages. We discuss possible extensions of the model to haplodiploidy.

SEX-RATIO BIAS WITH ASYMMETRIC EXCHANGE OF POLLEN BETWEEN DEMES

Evolution ◽  
1995 ◽  
Vol 49 (6) ◽  
pp. 1119-1124
Author(s):  
Peter D. Taylor
Keyword(s):  
Sex Ratio ◽  
Ratio Bias ◽  
Sex Ratio Bias

The Effects of Polygyny and Domicility on Offspring Sex Ratio in Ghana

2007 ◽  
Vol 6 (4) ◽  
pp. 431-456
Author(s):  
Adansi Amankwaa
Keyword(s):  
Sex Ratio ◽  
Family Structure ◽  
Living Arrangements ◽  
Living Arrangement ◽  
Demographic And Health Surveys ◽  
Offspring Sex Ratio ◽  
Ratio Bias ◽  
Sex Ratio Bias ◽  
Offspring Sex ◽  
The Relationship

AbstractThis article explores how family structure and domicility influences offspring sex ratio bias, specifically living arrangements of husband in polygynous unions. Data from three Ghana Demographic and Health Surveys were used to examine the relationship between family structure and offspring sex ratio at birth, something that previous studies have not been able to do. This study estimate models of sex ratio offspring if the wives live together with husband present and wives live in separate dwellings and are visited by husband in turn. The results suggest that within polygynous marriages there are more male births, especially when husbands reside in the same dwelling as wives, than when husbands reside in separate dwellings from their wives. The analyses show that offspring sex ratio is related to the structure of living arrangement of husbands in polygynous unions. Indeed, the findings suggest that living arrangements and family structure among humans are important factors in predicting offspring sex ratio bias.

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