scholarly journals No Evidence for Adaptive Differential Sex Allocation in Red Junglefowl (Gallus Gallus)

The Auk ◽  
2005 ◽  
Vol 122 (4) ◽  
pp. 1161-1168
Author(s):  
Timothy H. Parker
Keyword(s):  
Sex Ratio ◽  
Brood Size ◽  
Sex Allocation ◽  
Gallus Gallus ◽  
Ratio Analysis ◽  
Maternal Condition ◽  
Sperm Donor ◽  
Sex Ratio Bias ◽  
Red Junglefowl ◽  
Ratio Data

Abstract In many situations, selection should favor females that bias the sex ratio of their offspring. Two commonly examined factors potentially influencing off- spring sex ratio are paternal ornamentation and maternal condition. Male junglefowl with larger combs are attractive to females. I housed female Red Junglefowl (Gallus gallus) with sterile male consorts and artificially inseminated them with sperm from other males that the females never saw. I found no relationship between either the comb size of the consort or the comb size of the sperm donor and the sex ratio of the offspring. I previously reported a significant sex ratio bias related to maternal mass in Red Junglefowl. However, that analysis was based on sex ratio data not weighted for brood size and assuming a normal distribution. Here, I show that this effect disappears when I conduct a more appropriate analysis weighting sex ratio according to brood size and accounting for the binomial error distribution. I also failed to find evidence that male chicks hatch from larger eggs than female chicks. These results suggest that Red Junglefowl females may not bias the sex ratio of their brood in response to either their own condition or the attractiveness of the males with whom they copulate. Furthermore, these results demonstrate the importance of choosing the correct methods of sex ratio analysis. Falta de Evidencia de Asignación Adaptativa Diferencial entre Sexos en Gallus gallus

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 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 Breeding ecology and bias in offspring sex ratio in little grassbirds (Megalurus gramineus)

2003 ◽  
Vol 51 (5) ◽  
pp. 505 ◽  
Author(s):  
Rebecca R. McIntosh ◽  
Romke Kats ◽  
Mathew Berg ◽  
Jan Komdeur ◽  
Mark A. Elgar
Keyword(s):  
Sex Ratio ◽  
Breeding Season ◽  
Salt Marshes ◽  
Sex Allocation ◽  
Breeding Ecology ◽  
Offspring Sex Ratio ◽  
Reed Beds ◽  
Primary Sex Ratio ◽  
Sex Ratio Bias ◽  
Offspring Sex

Little grassbirds (Megalurus gramineus) are small, sexually monomorphic passerines that live in reed beds, lignum swamps and salt marshes in southern Australia. The breeding biology and patterns of sex allocation of the little grassbird were investigated over a single breeding season. Our observations of this species in the Edithvale Wetland Reserve revealed a highly male-biased population sex ratio, with some breeding territories containing several additional males. Nevertheless, there was little compelling evidence that little grassbirds breed cooperatively. The growth rates of male and female nestlings were similar and, as predicted by theory, there was no overall primary sex ratio bias. However, the primary sex ratio was female-biased early in the breeding season and became increasingly male-biased later in the breeding season.

scholarly journals Male-biased litter sex ratio in the southernmost Iberian population of edible dormouse: a strategy against isolation?

2016 ◽  
Vol 66 (3-4) ◽  
pp. 415-425
Author(s):  
Mariona Ferrandiz-Rovira ◽  
Lídia Freixas ◽  
Ignasi Torre ◽  
Sílvia Míguez ◽  
Antoni Arrizabalaga
Keyword(s):  
Sex Ratio ◽  
Iberian Peninsula ◽  
Sex Allocation ◽  
Resource Competition ◽  
Lifetime Reproductive Success ◽  
Maternal Condition ◽  
Ratio Variation ◽  
Iberian Population ◽  
Isolation Effects ◽  
Edible Dormice

Litter sex ratio is a key component of parental fitness due to its impact on lifetime reproductive success. Multiple causes may lay at the origin of sex ratio variation among species and populations, such as maternal condition, local resource competition, presence of helpers, habitat quality or inbreeding levels. Whereas variation in sex allocation between species is relatively well understood, it is still unclear how and why litter sex allocation differs within species. Here, we present an analysis of litter sex ratio variation in two populations of edible dormice (Glis glis) over nine years of study. Populations are situated in the Montnegre and Montseny massifs in Catalonia (NE Iberian Peninsula). The Montnegre population is nowadays an isolated population located at the southernmost range edge of the species in the Iberian Peninsula. Litter sex ratio was male-biased in Montnegre but balanced in Montseny, whereas both populations showed a balanced adult sex ratio. We suggest that this differential sex allocation investment in Montnegre, may be a strategy to overcome isolation effects in this massif, as males are the dispersing sex in this and other rodent species.

scholarly journals Sex allocation and field population sex ratio of Apanteles taragamae Viereck (Hymenoptera: Braconidae), a larval parasitoid of the cucumber moth Diaphania indica Saunders (Lepidoptera: Crambidae)

2021 ◽  
Vol 6 (1) ◽  
pp. 673-681
Author(s):  
Ihsan Nurkomar ◽  
Azru Azhar ◽  
Damayanti Buchori
Keyword(s):  
Sex Ratio ◽  
Brood Size ◽  
Sex Allocation ◽  
Natural Habitat ◽  
Adult Emergence ◽  
Female Offspring ◽  
Individual Level ◽  
Apanteles Taragamae ◽  
Larval Parasitoid ◽  
Biased Sex Ratio

Abstract Sex ratio is one of the most important biological characteristics of arthropods. In a parasitoid population, sex ratio can influence the suppression of host populations or the stability of host–parasitoid interactions in the field. In this study, a survey was carried out to determine the sex allocation through the sequence of male/female adult emergence and calculate the sex ratio of selected populations of Apanteles taragamae in their natural habitat. Assessment of sex ratio at the population and individual level (brood size per female) was examined. We found no difference in the likelihood that either sex would emerge before the other. Observations of sex ratio at the population and individual level reveal a females biased sex ratio. Analysis of the relationship between brood size and sex ratio of A. taragamae shows that brood size may influence the proportion of male to female offspring yielded. A male-biased sex ratio tends to be found in smaller brood size. However, sex ratio is shifted to female biased in larger brood size.

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
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