Worker Control of Sex Ratios and Selection for Extreme Multiple Mating by Queens

1993 ◽  
Vol 142 (2) ◽  
pp. 346-351 ◽  
Author(s):  
David C. Queller
Keyword(s):  
Multiple Mating ◽  
Sex Ratios ◽  
Selection For

scholarly journals Fisher vs. The Worms: Extraordinary Sex Ratios in Nematodes and the Mechanisms That Produce Them

Cells ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1793
Author(s):  
Justin Van Goor ◽  
Diane C. Shakes ◽  
Eric S. Haag
Keyword(s):  
Sex Ratio ◽  
Sperm Competition ◽  
Sex Chromosomes ◽  
Sex Ratios ◽  
Environmental Sex Determination ◽  
Fitness Advantage ◽  
Selection For ◽  
Facultative Parthenogenesis ◽  
Multicellular Organisms ◽  
Inbred Populations

Parker, Baker, and Smith provided the first robust theory explaining why anisogamy evolves in parallel in multicellular organisms. Anisogamy sets the stage for the emergence of separate sexes, and for another phenomenon with which Parker is associated: sperm competition. In outcrossing taxa with separate sexes, Fisher proposed that the sex ratio will tend towards unity in large, randomly mating populations due to a fitness advantage that accrues in individuals of the rarer sex. This creates a vast excess of sperm over that required to fertilize all available eggs, and intense competition as a result. However, small, inbred populations can experience selection for skewed sex ratios. This is widely appreciated in haplodiploid organisms, in which females can control the sex ratio behaviorally. In this review, we discuss recent research in nematodes that has characterized the mechanisms underlying highly skewed sex ratios in fully diploid systems. These include self-fertile hermaphroditism and the adaptive elimination of sperm competition factors, facultative parthenogenesis, non-Mendelian meiotic oddities involving the sex chromosomes, and environmental sex determination. By connecting sex ratio evolution and sperm biology in surprising ways, these phenomena link two “seminal” contributions of G. A. Parker. 

scholarly journals Polyandry enhances offspring survival in an infanticidal species

2009 ◽  
Vol 6 (1) ◽  
pp. 24-26 ◽  
Author(s):  
Ines Klemme ◽  
Hannu Ylönen
Keyword(s):  
Mating Systems ◽  
Multiple Mating ◽  
Empirical Test ◽  
Myodes Glareolus ◽  
Offspring Survival ◽  
Bank Voles ◽  
Female Counterstrategy ◽  
Fitness Benefits ◽  
Selection For ◽  
Genetic Fitness

The adaptive significance of polyandry is an intensely debated subject in sexual selection. For species with male infanticidal behaviour, it has been hypothesized that polyandry evolved as female counterstrategy to offspring loss: by mating with multiple males, females may conceal paternity and so prevent males from killing putative offspring. Here we present, to our knowledge, the first empirical test of this hypothesis in a combined laboratory and field study, and show that multiple mating seems to reduce the risk of infanticide in female bank voles Myodes glareolus . Our findings thus indicate that females of species with non-resource based mating systems, in which males provide nothing but sperm, but commit infanticide, can gain non-genetic fitness benefits from polyandry.

scholarly journals Evolution of male strategies with sex-ratio–dependent pay-offs: connecting pair bonds with grandmothering

2017 ◽  
Vol 372 (1729) ◽  
pp. 20170041 ◽  
Author(s):  
Sara L. Loo ◽  
Kristen Hawkes ◽  
Peter S. Kim
Keyword(s):  
Life History ◽  
Sex Ratio ◽  
Human Evolution ◽  
Paternal Care ◽  
Multiple Mating ◽  
Sex Ratios ◽  
Mate Guarding ◽  
Equation Model ◽  
Pair Bonding ◽  
Pair Bonds

Men's provisioning of mates and offspring has been central to ideas about human evolution because paternal provisioning is absent in our closest evolutionary cousins, the great apes, and is widely assumed to result in pair bonding, which distinguishes us from them. Yet mathematical modelling has shown that paternal care does not readily spread in populations where competition for multiple mates is the common male strategy. Here we add to models that point to the mating sex ratio as an explanation for pairing as pay-offs to mate guarding rise with a male-biased sex ratio. This is of interest for human evolution because our grandmothering life history shifts the mating sex ratio from female- to male-biased. Using a difference equation model, we explore the relative pay-offs for three competing male strategies (dependant care, multiple mating, mate guarding) in response to changing adult sex ratios. When fertile females are abundant, multiple mating prevails. As they become scarce, mate guarding triumphs. The threshold for this shift depends on guarding efficiency. Combined with mating sex ratios of hunter–gatherer and chimpanzee populations, these results strengthen the hypothesis that the evolution of our grandmothering life history propelled the shift to pair bonding in the human lineage. This article is part of the themed issue ‘Adult sex ratios and reproductive decisions: a critical re-examination of sex differences in human and animal societies’.

Sex Selection and the Charter

1994 ◽  
Vol 7 (1) ◽  
pp. 173-193
Author(s):  
Elisabeth Boetzkes
Keyword(s):  
Policy Making ◽  
Sex Ratios ◽  
Fetal Monitoring ◽  
Reproductive Technologies ◽  
Sex Selection ◽  
Sex Diagnosis ◽  
Women's Equality ◽  
Selection For

One of the most perplexing difficulties for policy-making to emerge from the recent deliberations of Canadians over the new reproductive technologies is how to evaluate and if necessary, justify regulating, the practice of sex selection. Through the increasingly sophisticated reproductive technologies, gynosperm and androsperm may be separated and women artificially inseminated with the sperm most likely to result in a fetus of the favoured sex. Sex diagnosis may be performed on embryos in vitro, and selection for implantation made by reference to sex. And fetal monitoring may determine the sex of developing fetuses during pregnancy, thus allowing abortion of fetuses of the “wrong” sex. Recent Canadian trends in accessing and using sex selection technology, combined with sociological evidence showing a marked transcultural preference for male children, for male firstborns, and for more males than females within families of uneven sex ratios, alert us to the dangers of the practice of sex selection for women’s equality.

scholarly journals Variance-based selection may explain general mating patterns in social insects

2008 ◽  
Vol 4 (3) ◽  
pp. 270-273 ◽  
Author(s):  
Olav Rueppell ◽  
Nels Johnson ◽  
Jan Rychtář
Keyword(s):  
Multiple Mating ◽  
Empirical Support ◽  
Mating Frequency ◽  
Colony Fitness ◽  
Colony Performance ◽  
Single Mating ◽  
Empirical Tests ◽  
Selection For ◽  
Interspecific Comparisons ◽  
Focal Task

Female mating frequency is one of the key parameters of social insect evolution. Several hypotheses have been suggested to explain multiple mating and considerable empirical research has led to conflicting results. Building on several earlier analyses, we present a simple general model that links the number of queen matings to variance in colony performance and this variance to average colony fitness. The model predicts selection for multiple mating if the average colony succeeds in a focal task, and selection for single mating if the average colony fails, irrespective of the proximate mechanism that links genetic diversity to colony fitness. Empirical support comes from interspecific comparisons, e.g. between the bee genera Apis and Bombus, and from data on several ant species, but more comprehensive empirical tests are needed.

scholarly journals A sex allocation cost to polyandry in a parasitoid wasp

2015 ◽  
Vol 11 (6) ◽  
pp. 20150205 ◽  
Author(s):  
Rebecca A. Boulton ◽  
David M. Shuker
Keyword(s):  
Sex Allocation ◽  
Multiple Mating ◽  
Sex Ratios ◽  
Parasitoid Wasp ◽  
Laboratory Culture ◽  
Culture Conditions ◽  
Costs And Benefits ◽  
Offspring Production ◽  
Offspring Sex ◽  
In The Wild

The costs and benefits of polyandry are central to understanding the near-ubiquity of female multiple mating. Here, we present evidence of a novel cost of polyandry: disrupted sex allocation. In Nasonia vitripennis , a species that is monandrous in the wild but engages in polyandry under laboratory culture conditions, sexual harassment during oviposition results in increased production of sons under conditions that favour female-biased sex ratios. In addition, females more likely to re-mate under harassment produce the least female-biased sex ratios, and these females are unable to mitigate this cost by increasing offspring production. Our results therefore argue that polyandry does not serve to mitigate the costs of harassment (convenience polyandry) in Nasonia . Furthermore, because males benefit from female-biased offspring sex ratios, harassment of ovipositing females also creates a novel cost of that harassment for males.

The Effects of Bidirectional Selection for Social Dominance On Agonistic Behavior and Sex Ratios in the Paradise Fish (Macropodus Opercularis)

Behaviour ◽  
1984 ◽  
Vol 90 (1-3) ◽  
pp. 25-44 ◽  
Author(s):  
Richard C. Francis
Keyword(s):  
Sexual Differentiation ◽  
Social Dominance ◽  
Sex Ratios ◽  
The Other ◽  
Response To Selection ◽  
Dominance Status ◽  
Selection For ◽  
Bidirectional Selection ◽  
Paradise Fish ◽  
Brood Fish

AbstractA population of paradise fish (Macropodus opercularis) was subjected to five generations of bidirectional selection for social dominance in order to investigate correlated changes in agonistic behaviors. In addition to the high and low dominance lines (HD and LD respectively), a third dominance line was created through selection for individuals closest to the median in dominance success. The MD line provided standard opponents for members of the other two dominance lines and served as a control for inbreeding effects. The response to selection was asymmetrical. After five generations of selection the LD line had diverged significantly from the MD line, but the HD line had not. None of the three factors known to cause an asymmetrical response to selection (directional gene frequencies, directional allelic dominance and inbreeding depression) can account for the response to selection found here. The divergence of the HD and LD lines with respect to dominance success was not accompanied by any changes in the measures of aggressiveness. The F-5 generation of the HD and LD lines did not differ significantly for any of the measures of aggressiveness used here, indicating that social dominance and aggressiveness are not intimately related. An alteration in the sex ratio of the HD line was an unanticipated byproduct of selection. The F-5 generation of this selection line contained an overwhelming preponderance of males. Interpretation of these results is complicated by the fact that environmental factors such as temperature and the degree of crowding probably influence sexual differentiation in this species. The social crowding factor, in particular, was found to be important and was investigated in a preliminary way. For all three dominance lines it was found that as crowding increased, so did the proportion of females in a brood. Fish raised in physical isolation showed a strong tendency to become males. These results suggest that sexual differentiation is socially mediated. Within a given brood, fish of high dominance status tended to become males and fish of low dominance status tended to become females. The results from the isolation-reared fish indicate that it is not dominance per se that promotes maleness, but rather, the condition of being undominated. Under uncrowded conditions an individual is, on average, dominated by fewer fish than under crowded conditions. Above and beyond this density related trend in the sex ratios, however, there were significant between-the-line differences. The HD line showed a greater proportion of males than the other dominance lines, over all density conditions. It appears that selection for high social dominance constituted selection for maleness. This response to selection indicates a continuum of genetic sex in this species and a polyfactorial mode of inheritance. The alteration in the sex ratios might also explain the asymmetrical response to selection for social dominance, in that the HD line did in fact exhibit a greater proportion of dominant fish, though not a greater proportion of dominant males, than the other two dominance lines. As such, the asymmetrical response to selection would be an artifact of the measuring procedures.

Split sex ratios in ants with multiple mating

1994 ◽  
Vol 9 (4) ◽  
pp. 120-122 ◽  
Author(s):  
A.F.G. Bourke ◽  
G.L. Chan
Keyword(s):  
Multiple Mating ◽  
Sex Ratios
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