scholarly journals A father effect explains sex-ratio bias

2017 ◽  
Vol 284 (1861) ◽  
pp. 20171159 ◽  
Author(s):  
Aurelio F. Malo ◽  
Felipe Martinez-Pastor ◽  
Francisco Garcia-Gonzalez ◽  
Julián Garde ◽  
Jonathan D. Ballou ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Sex Ratio ◽  
Sex Chromosome ◽  
Sex Ratios ◽  
Sperm Nucleus ◽  
Equal Proportion ◽  
Offspring Sex Ratio ◽  
Ratio Bias ◽  
Sex Ratio Bias ◽  
Offspring Sex

Sex ratio allocation has important fitness consequences, and theory predicts that parents should adjust offspring sex ratio in cases where the fitness returns of producing male and female offspring vary. The ability of fathers to bias offspring sex ratios has traditionally been dismissed given the expectation of an equal proportion of X- and Y-chromosome-bearing sperm (CBS) in ejaculates due to segregation of sex chromosomes at meiosis. This expectation has been recently refuted. Here we used Peromyscus leucopus to demonstrate that sex ratio is explained by an exclusive effect of the father, and suggest a likely mechanism by which male-driven sex-ratio bias is attained. We identified a male sperm morphological marker that is associated with the mechanism leading to sex ratio bias; differences among males in the sperm nucleus area (a proxy for the sex chromosome that the sperm contains) explain 22% variation in litter sex ratio. We further show the role played by the sperm nucleus area as a mediator in the relationship between individual genetic variation and sex-ratio bias. Fathers with high levels of genetic variation had ejaculates with a higher proportion of sperm with small nuclei area. This, in turn, led to siring a higher proportion of sons (25% increase in sons per 0.1 decrease in the inbreeding coefficient). Our results reveal a plausible mechanism underlying unexplored male-driven sex-ratio biases. We also discuss why this pattern of paternal bias can be adaptive. This research puts to rest the idea that father contribution to sex ratio variation should be disregarded in vertebrates, and will stimulate research on evolutionary constraints to sex ratios—for example, whether fathers and mothers have divergent, coinciding, or neutral sex allocation interests. Finally, these results offer a potential explanation for those intriguing cases in which there are sex ratio biases, such as in humans.

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.

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.

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.

scholarly journals Drivers of sex ratio bias in the eastern bongo: lower inbreeding increases the probability of being born male

2019 ◽  
Vol 286 (1902) ◽  
pp. 20190345 ◽  
Author(s):  
Aurelio F. Malo ◽  
Tania C. Gilbert ◽  
Philip Riordan
Keyword(s):  
Sex Ratio ◽  
Inbreeding Depression ◽  
Sex Ratios ◽  
Reproductive Traits ◽  
Genetic Effects ◽  
Equal Proportion ◽  
Paternal Effects ◽  
Offspring Sex Ratio ◽  
Genetic Quality ◽  
Offspring Sex

Parent sex ratio allocation has consequences for individual fitness, population dynamics, and conservation. Theory predicts that parents should adjust offspring sex ratio when the fitness returns of producing male or female offspring varies. Previous studies have assumed that only mothers are capable of biasing offspring sex ratios, but have neglected fathers, given the expectation of an equal proportion of X- and Y-chromosome-bearing (CBS) sperm in ejaculates due to sex chromosome segregation at meiosis. This assumption has been recently refuted and both paternal fertility and paternal genetic quality have been shown to bias sex ratios. Here, we simultaneously test the relative contribution of paternal, maternal, and individual genetic quality, as measured by inbreeding, on the probability of being born a son or a daughter, using pedigree and lifelong offspring sex ratio data for the eastern bongo ( Tragelaphus eurycerus isaaci ). Our models showed first, that surprisingly, as individual inbreeding decreases the probability of being born male increases, second, that paternal genetic effects on sex ratio were stronger than maternal genetic effects (which were absent). Furthermore, paternal effects were opposite in sign to those predicted; father inbreeding increases the probability of having sons. Previous paternal effects have been interpreted as adaptive due to sex-specific inbreeding depression for reproductive traits. We argue that in the eastern bongo, the opposite sign of the paternal effect on sex ratios results from a reversed sex-specific inbreeding depression pattern (present for female but not male reproductive traits). We anticipate that this research will help stimulate research on evolutionary constraints to sex ratios. Finally, the results open a new avenue of research to predict sex ratio allocation in an applied conservation context. Future models of sex ratio allocation should also include the predicted inbreeding level of the offspring and paternal inbreeding levels.

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

Host size-dependent sex allocation behaviour in a parasitoid: implications forCatolaccus grandis(Hymenoptera: Pteromalidae) mass rearing programmes

1998 ◽  
Vol 88 (1) ◽  
pp. 37-45 ◽  
Author(s):  
K.M. Heinz
Keyword(s):  
Biological Control ◽  
Sex Ratio ◽  
Sex Allocation ◽  
Sex Ratios ◽  
Boll Weevil ◽  
Mass Rearing ◽  
Host Size ◽  
Offspring Sex Ratio ◽  
Offspring Sex ◽  
Control Programmes

AbstractAn often encountered problem associated with augmentative and inundative biological control programmes is the high cost of producing sufficient numbers of natural enemies necessary to suppress pest populations within the time constraints imposed by ephemeral agroecosystems. In many arrhenotokous parasitoids, overproduction of males in mass-rearing cultures inflates costs (per female) and thus limits the economic feasibility of these biological control programmes. Within the context of existing production technologies, experiments were conducted to determine if the sex ratio ofCatolaccus grandis(Burks), an ectoparasitoid of the boll weevilAnthonomous grandisBoheman, varied as a function of boll weevil larval size. Results from natural and manipulative experiments demonstrate the following behavioural characteristics associated with C.grandissex allocation behaviour: (i) femaleC. grandisoffspring are produced on large size hosts and male offspring are produced on small hosts; (ii) whether a host is considered large or small depends upon the overall distribution of host sizes encountered by a female parasitoid; and (iii) female parasitoids exhibit a greater rate of increase in body size with host size than do male parasitoids. The observed patterns cannot be explained by sex-specific mortality of immature parasitoids developing on the different host size categories. In subsequent experiments, laboratory cultures ofC. grandisexposed daily to successively larger sizes ofA. grandislarvae produced successively greater female biased offspring sex ratios, cultures exposed daily to successively smaller sizes of host larvae produced successively greater male biased offspring sex ratios, and cultures exposed daily to equivalent host size distributions over time maintained a uniform offspring sex ratio. By increasing the average size ofA. grandislarval hosts exposed toC. grandisby 2.5 mg per day in mass rearing cultures, the percentage of male progeny can be reduced from 33% to 23% over a period of four consecutive exposure days.

scholarly journals Does sex-ratio selection influence nest-site choice in a reptile with temperature-dependent sex determination?

2013 ◽  
Vol 280 (1772) ◽  
pp. 20132460 ◽  
Author(s):  
Timothy S. Mitchell ◽  
Jessica A. Maciel ◽  
Fredric J. Janzen
Keyword(s):  
Sex Ratio ◽  
Sex Determination ◽  
Nest Site ◽  
Sex Ratios ◽  
Temperature Dependent ◽  
Dioecious Species ◽  
Offspring Sex Ratio ◽  
Nest Sites ◽  
Offspring Sex ◽  
Nest Site Choice

Evolutionary theory predicts that dioecious species should produce a balanced primary sex ratio maintained by frequency-dependent selection. Organisms with environmental sex determination, however, are vulnerable to maladaptive sex ratios, because environmental conditions vary spatio-temporally. For reptiles with temperature-dependent sex determination, nest-site choice is a behavioural maternal effect that could respond to sex-ratio selection, as mothers could adjust offspring sex ratios by choosing nest sites that will have particular thermal properties. This theoretical prediction has generated decades of empirical research, yet convincing evidence that sex-ratio selection is influencing nesting behaviours remains absent. Here, we provide the first experimental evidence from nature that sex-ratio selection, rather than only viability selection, is probably an important component of nest-site choice in a reptile with temperature-dependent sex determination. We compare painted turtle ( Chrysemys picta ) neonates from maternally selected nest sites with those from randomly selected nest sites, observing no substantive difference in hatching success or survival, but finding a profound difference in offspring sex ratio in the direction expected based on historical records. Additionally, we leverage long-term data to reconstruct our sex ratio results had the experiment been repeated in multiple years. As predicted by theory, our results suggest that sex-ratio selection has shaped nesting behaviour in ways likely to enhance maternal fitness.

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.

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