Fetal sex ratio in relation to maternal mass and age in reindeer

1997 ◽  
Vol 75 (4) ◽  
pp. 648-650 ◽  
Author(s):  
Eigil Reimers ◽  
Dag Lenvik
Keyword(s):  
Natural Selection ◽  
Sex Ratio ◽  
Parental Investment ◽  
Similar Condition ◽  
Rangifer Tarandus ◽  
Good Condition ◽  
Maternal Condition ◽  
Fetal Sex ◽  
Poor Condition ◽  
Parental Ability

Theory suggests that a male in good condition at the end of the period of parental investment will outproduce a sister in similar condition, while she will outproduce him if both are in poor condition. Accordingly, natural selection should favor parental ability to adjust the sex ratio of offspring produced according to parental ability to invest. As maternal condition declines from good to poor, the fetal sex ratio should decline from a high proportion of males to a high proportion of females. Data from 1525 domestic reindeer (Rangifer tarandus) in six different herds slaughtered during December and January in 1976 through 1979 do not support a relationship between the sex of the fetus and either the condition of the mother or her age.

scholarly journals Fitness Functions Determine Optimal Parental Allocation: Redefining Trivers–Willard Theory

2019 ◽  
Author(s):  
Jibeom Choi ◽  
Hyungmin Roh ◽  
Sang-im Lee ◽  
Hee-Dae Kwon ◽  
Myungjoo Kang ◽  
...  
Keyword(s):  
Parental Investment ◽  
Empirical Data ◽  
Empirical Studies ◽  
Good Condition ◽  
Maternal Condition ◽  
Female Fitness ◽  
Male And Female ◽  
Poor Condition ◽  
Fitness Functions ◽  
Parental Fitness

According to Trivers-Willard theory1, females in a good condition should carry more male offspring to maximize their fitness while should carry more females in a poor condition. Diverse theoretical and empirical studies has been performed to verify the validity of this claim2,3. Some portion of the empirical observations, however, exhibited contrary outcome to Trivers-Willard theory4. To resolve this problem, we computationally and mathematically show in here that reversed Trivers-Willard theory actually could be the outcome of the parental fitness optimization. In our models with identical fitness functions, we found that selective equitable care is optimal, and the number of the cared offspring should monotonically increase with maternal condition (or expendable parental investment). In some of our models with two distinguished male and female fitness functions, optimizations results were congruent with the conventional Trivers-Willard theory. In other models of ours, contrary to Trivers-Willard theory, it was optimal to invest in males when maternal condition was low. The results along with our hypothesis can explain the empirical observations that were previously thought to be the counterexample of Trivers-Willard theory. We propose that Trivers-Willard theory should be interpreted in multidimensional way, and more elaborate empirical data need to be collected to verify such propositions.

scholarly journals Maternal Condition and Nestling Sex Ratio in House Wrens

The Auk ◽  
2002 ◽  
Vol 119 (1) ◽  
pp. 125-131 ◽  
Author(s):  
Linda A. Whittingham ◽  
Stacy M. Valkenaar ◽  
Nicole E. Poirier ◽  
Peter O. Dunn
Keyword(s):  
Sex Ratio ◽  
Good Condition ◽  
Poor Quality ◽  
Maternal Condition ◽  
House Wren ◽  
House Wrens ◽  
Extrapair Mating ◽  
Female Condition ◽  
Nestling Condition ◽  
Fitness Benefits

Abstract Parents are expected to vary the sex ratio of their offspring in relation to the sex-specific fitness benefits. However, benefits of producing sex-biased broods may be dependent on condition of the female. For example, mothers in good condition could achieve greater fitness if they produced high-quality sons, whereas, mothers in poor condition would gain more by producing daughters rather than poor-quality sons. As a consequence, we would expect to see a relationship between female condition and sex ratio of offspring. We examined effect of maternal condition on nestling condition and sex ratio in the House Wren (Troglodytes aedon). Overall sex ratio of nestlings in the population was not biased, but females in better condition produced relatively more sons. Overall positive relationship between female condition and proportion of male offspring was due to second broods, which were significantly male-biased and more likely to be produced by females in good condition. Females in better condition also tended to provision young more often and produced both male and female nestlings in better condition. Polygyny and extrapair mating are common in House Wrens. If males in good condition are more likely to be successful breeders as adults, then it may benefit mothers in good condition to produce more sons.

scholarly journals Maternal condition and previous reproduction interact to affect offspring sex in a wild mammal

2016 ◽  
Vol 12 (8) ◽  
pp. 20160510 ◽  
Author(s):  
Mathieu Douhard ◽  
Marco Festa-Bianchet ◽  
Fanie Pelletier
Keyword(s):  
Sex Ratio ◽  
Empirical Studies ◽  
Good Condition ◽  
Ovis Canadensis ◽  
Maternal Condition ◽  
Paternal Effects ◽  
Offspring Sex Ratio ◽  
Fitness Consequences ◽  
Offspring Sex ◽  
Dimorphic Species

Trivers and Willard proposed that offspring sex ratio should vary with maternal condition when condition, meant as maternal capacity to care, has different fitness consequences for sons and daughters. In polygynous and dimorphic species, mothers in good condition should preferentially produce sons, whereas mothers in poor condition should produce more daughters. Despite its logical appeal, support for this hypothesis has been inconsistent. Sex-ratio variation may be influenced by additional factors, such as environmental conditions and previous reproduction, which are often ignored in empirical studies. We analysed 39 years of data on bighorn sheep ( Ovis canadensis ) that fit all the assumptions of the Trivers–Willard hypothesis. Production of sons increased with maternal condition only for mothers that weaned a son the previous year. This relationship likely reflects a mother's ability to bear the higher reproductive costs of sons. The interaction between maternal condition and previous weaning success on the probability of producing a son was independent of the positive effect of paternal reproductive success. Maternal and paternal effects accounted for similar proportions of the variance in offspring sex. Maternal reproductive history should be considered in addition to current condition in studies of sex allocation.

Natural Selection of Parental Ability to Vary the Sex Ratio of Offspring

Science ◽  
1973 ◽  
Vol 179 (4068) ◽  
pp. 90-92 ◽  
Author(s):  
R. L. Trivers ◽  
D. E. Willard
Keyword(s):  
Natural Selection ◽  
Sex Ratio ◽  
Parental Ability ◽  
Selection Of

Fetal Sex Ratio in the Rhesus (Macaca mulatta)

1979 ◽  
Vol 31 (3) ◽  
pp. 246-250 ◽  
Author(s):  
R.F. DiGiacomo ◽  
P.W. Shaughnessy
Keyword(s):  
Sex Ratio ◽  
Fetal Sex

scholarly journals Diabetic Embryopathy in C57BL/6J Mice: Altered Fetal Sex Ratio and Impact of the Splotch Allele

Diabetes ◽  
2001 ◽  
Vol 50 (5) ◽  
pp. 1193-1199 ◽  
Author(s):  
A. F. Machado ◽  
E. F. Zimmerman ◽  
D. N. Hovland ◽  
R. Weiss ◽  
M. D. Collins
Keyword(s):  
Sex Ratio ◽  
Fetal Sex ◽  
Diabetic Embryopathy

Effects of temperature on growth of north-east Pacific moon jellyfish ephyrae, Aurelia labiata (Cnidaria: Scyphozoa)

2005 ◽  
Vol 85 (3) ◽  
pp. 569-573 ◽  
Author(s):  
Chad L. Widmer
Keyword(s):  
Good Condition ◽  
Bell Diameter ◽  
Optimal Temperature ◽  
Moon Jellyfish ◽  
Poor Condition ◽  
Temperature Range ◽  
North East ◽  
East Pacific ◽  
Optimal Temperature Range ◽  
Effects Of Temperature

The effects of ten different water temperatures on the growth of newly released ephyrae of Aurelia labiata were explored. Ephyrae grown at 21°C showed the greatest growth, increasing in bell diameter from about 4.0 mm to 14.5 mm in 14 days and remained in good condition for the duration of the experiment. Ephyrae subjected to other temperatures grew at different rates. Ephyrae maintained at 8°C gradually decreased in size during the experiment, shrinking in bell diameter from about 4.0 mm to 3.8 mm by day 14, but remained in apparent good condition. Ephyrae reared at 22.5°C and above everted their bells, were in poor condition, and were unable to feed or swim effectively by about day ten. In this study the optimal temperature range for rearing A. labiata ephyrae was 12°C—21°C, which corresponds with the reported range for this species.

Natural Selection and the Sex Ratio

Nature ◽  
1960 ◽  
Vol 188 (4754) ◽  
pp. 960-961 ◽  
Author(s):  
A. W. F. EDWARDS
Keyword(s):  
Natural Selection ◽  
Sex Ratio
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