Seasonal effects on fetal selection related to AB0 blood groups of mother and child.

An association of AB0 blood groups and month of birth was examined in two groups, students and newborns in Tokyo. Among 4919 students born mainly in the 1960s, an apparent seasonal variation was shown in births of blood group B students. Among 3592 newborns at an obstetric clinic in the 1980s seasonal variation was also observed in all four blood groups. The ratio of 0 group to A group newborns (0/A ratio) from 0 mothers was lower than that from A mothers among the 0 and A pairs contrary to the expected effects of 0-A incompatibility. The 0/A ratio was apparently different by season and the 0/A ratio from 0 mothers was significantly lower than that from A mothers among those born during August-January. It is assumed that an association of birth season with AB0 blood group may be caused by some seasonally and secularly changing environmental "infertility factors" such as infectious microorganism which may have some common components with a particular blood group substance respectively and induce a loss of embryos selectively at a particular season.     

Sex ratio in man: an analysis of the relationship with ABO blood groups and placental alkaline phosphatase phenotype.

Secondary sex ratio (SR) in man is influenced by various genetic and environmental factors. It has been observed that SR in subjects of blood group B compatible with their mothers is higher than in other subjects. The analysis of 676 newborns of the Rome population and 1,684 newborns of the New Haven (Connecticut) population have confirmed a higher SR in B group subjects compatible with their mothers. The data also indicate that placental alkaline phosphatase is another genetic factor influencing SR in man and that there is a strong interaction among ABO phenotype, fetomaternal ABO compatible status and PAP phenotype concerning their effects on SR.     

AB0 blood group incompatibility and inbreeding effects: Evidence for an interaction

Summary It is known that consanguinity reduces the chances of maternal-foetal incompatibility but it is not known whether inbreeding influences the expression of the effects of such incompatibility. This paper investigates and finds evidence for an interaction between inbreeding and AB0 blood group incompatibility on the expression of neonatal mortality, sibship precocious mortality, neonatal jaundice, asphyxia, and sex ratio, through screening of 3923 consecutive newborns. Inbreeding and incompatibility individually showed variable effects on the above parameters, but their interaction was such that, in the presence of inbreeding, incompatibility reduced the incidence/relative risk of all the above factors. Such a uniform negative interaction was presumed to be due to homozygosity of some pleiotropic genes caused by inbreeding.     

Sex-specific incompatibility generates locus-specific rates of introgression between species

Disruption of interactions among ensembles of epistatic loci has been shown to contribute to reproductive isolation among various animal and plant species. Under the Bateson-Dobzhansky-Muller model, such interspecific incompatibility arises as a by-product of genetic divergence in each species, and the Orr-Turelli model indicates that the number of loci involved in incompatible interactions may "snowball" over time. We address the combined effect of multiple incompatibility loci on the rate of introgression at neutral marker loci across the genome. Our analysis extends previous work by accommodating sex specificity: differences between the sexes in the expression of incompatibility, in rates of crossing over between neutral markers and incompatibility loci, and in transmission of markers or incompatibility factors. We show that the evolutionary process at neutral markers in a genome subject to incompatibility selection is well approximated by a purely neutral process with migration rates appropriately scaled to reflect the influence of selection targeted to incompatibility factors. We confirm that in the absence of sex specificity and functional epistasis among incompatibility factors, the barrier to introgression induced by multiple incompatibility factors corresponds to the product of the barriers induced by the factors individually. A new finding is that barriers to introgression due to sex-specific incompatibility depart in general from multiplicativity. Our partitioning of variation in relative reproductive rate suggests that such departures derive from associations between sex and incompatibility and between sex and neutral markers. Concordant sex-specific incompatibility (for example, greater impairment of male hybrids or longer map lengths in females) induces lower barriers (higher rates of introgression) than expected under multiplicativity, and discordant sex-specific incompatibility induces higher barriers.     

Variation of sex ratio and ABO blood group composition by month of birth of blood donors in Tokyo

Sex ratio of 17,273 blood donors born during the period between 1925 and 1935 was examined according to their month of birth and ABO blood groups in comparison with 5,810 healthy non-blood donors born in the 1900s to 1930s. The sex ratio of the blood donors and the non-blood donors varied similarly according to their month of birth with a prominent peak in summer births and a trough in winter births. This birth season with a high sex ratio was different from that of the general births during the period between 1921 and 1935, in which a maximum sex ratio was found in November. A possible explanation for the difference is the different rate of male and female infant deaths according to birth month. Variation of the sex ratio according to season of birth was not similar among the four ABO blood groups. Sex ratio of the donors with blood group B showed no elevation among the summer births. Non-blood donors with blood group B, on the contrary, showed a higher sex ratio than the others in the summer births. This difference can not be explained by infant or juvenile deaths. A possibility is that a tendency to become a blood donor is modified by the season of one's birth differently according to gender and ABO blood groups.     

Lack of Sex-Biased Maternal Investment in spite of a Skewed Birth Sex Ratio in White-Headed Langurs (Trachypithecus leucocephalus)

Numerous hypotheses have been developed to explain sex allocation. In male-dispersing, female cooperatively breeding species, the local resource competition model predicts male-biased birth sex ratio, the local resource enhancement model predicts female-biased birth sex ratio, and the population adjustment model predicts that biased birth sex ratio should not be favored if the two sexes are equally costly to rear. The male quality model predicts that, in polygynous species, females in better physical condition will either produce more sons than daughters or invest more heavily in sons than in daughters. White-headed langurs are a female philopatry and female cooperatively breeding species. During a 11-yr study, a total of 133 births were recorded, among which birth sex ratio (M:F = 73:49) was significantly male-biased. This is consistent with the prediction of the local resource competition model. On the other hand, if mothers balanced their investment between the two sexes, according to Fisher's population adjustment model, males should be the less-costly-to-rear sex. However, we found no sex difference for infant mortality (12.3% in males and 12.2% in females), and sons induced slightly longer interbirth interval (son: 26.4 ± 1.1 mo, daughter: 24.1 ± 0.6 mo) and lactational period (son: 20.9 ± 1.0 mo, daughters: 19.6 ± 0.5 mo) for their mothers. Thus, the population adjustment model was not supported by this study. The local resource enhancement model was not supported because birth sex ratio did not bias to females who provided more reproductive assistance. On the individual level, probit regression showed no relation between birth sex ratio and group size. Because the group size was considered to be negatively related to female physical condition, our study did not support the male-quality model. We suggested several possibilities to explain these results.     

Selective interactions among Rh,ABO, and sex ratio of newborns

Summary The hypothesis that the Rh and ABO blood systems behave like the HLA system in relation to mother-conception tolerance-rejection mechanisms was tested in 25,501 mother-infant pairs. According to this hypothesis, heterozygotes carrying a paternal gene that is not present in their mother should be better tolerated than homozygotes. Significantly more BO infants born to AO mothers. AO infants born to BO mothers, Rh(+) heterozygotes born to Rh(-) mothers, and less significantly AO infants born to OO mothers confirm the hypothesis. Fewer homozygotes occurred in Rh(-) infants born to Rh(+) mothers and in O infants born to non-O mothers. Deviations from the Hardy-Weinberg equilibrium found in the ABO system were modified by the Rh and sex of the infant. These data strongly support the hypothesis that at least two feto-maternal systems influence the denstiny of pregnancies: the classical known incompatibility system which operates late in pregnancy and a new one which is based on the induction of maternal tolerance early in pregnancy: maternal tolerance seems to be better elicited by heterozygous eggs or embryos carrying a gene not present in the mother. The data also support the hypothesis that the sex ratio is influenced by feto-maternal tolerance-rejection mechanisms associated with the ABO and Rh systems.     

Great expectations: dominance,breeding success and offspring sex ratios in red deer

Differences in dominance rank among red deer (Cervus elaphus) females (hinds) on Rhum were related to their breeding success as well as to the comparative success of male and female offspring. Males (stags) born to mothers above median rank were more successful than hinds, while hinds born to subordinate mothers were more successful than stags. The ratio of male to female calves produced by dominant mothers was significantly higher than that produced by subordinates. Since dominance rank among hinds is related to their body weight as adults and to their birth weight, these results suggest that the birth sex ratio may be affected by environmental factors operating during a female's early development.     

Reproductive parameters of female orangutans (Pongo pygmaeus wurmbii) 1971–2011, a 40-year study at Tanjung Puting National Park, Central Kalimantan, Indonesia

This study presents reproductive parameter data gathered by direct observation over a 40-year period (1971–2011) of the provisioned free-ranging population of orangutans at Camp Leakey in Tanjung Puting National Park, Central Kalimantan, Indonesia. Age at first reproduction, interbirth interval (IBI), sex ratio at birth, and infant mortality for 19 female orangutans (11 first-generation wild-born ex-captive mothers and 8 second-generation mothers) are included in this analysis. Age at first reproduction among the first-generation mothers was similar to that among wild orangutans, while second-generation mothers had a significantly earlier age at first reproduction. IBIs were similar among first- and second-generation mothers and were significantly shorter than those recorded in studies of wild orangutan populations. There was an expected male-biased sex ratio at birth and a slightly higher than expected rate of infant mortality when compared to wild populations. Infant mortality was primarily seen among second-generation mothers who gave birth before the age of 12, and among first births of some first-generation mothers. These results lend support to the ecological energetics hypothesis, which predicts that increased diet quality leads to a faster rate of reproduction.     

Sexual conflict in action: An antagonistic relationship between maternal and paternal sex allocation in the tammar wallaby,Notamacropus eugenii

Sex ratio biases are often inconsistent, both among and within species and populations. While some of these inconsistencies may be due to experimental design, much of the variation remains inexplicable. Recent research suggests that an exclusive focus on mothers may account for some of the inconsistency, with an increasing number of studies showing variation in sperm sex ratios and seminal fluids. Using fluorescent in‐situ hybridization, we show a significant population‐level Y‐chromosome bias in the spermatozoa of wild tammar wallabies, but with significant intraindividual variation between males. We also show a population‐level birth sex ratio trend in the same direction toward male offspring, but a weaning sex ratio that is significantly female‐biased, indicating that males are disproportionately lost during lactation. We hypothesize that sexual conflict between parents may cause mothers to adjust offspring sex ratios after birth, through abandonment of male pouch young and reactivation of diapaused embryos. Further research is required in a captive, controlled setting to understand what is driving and mechanistically controlling sperm sex ratio and offspring sex ratio biases and to understand the sexually antagonistic relationship between mothers and fathers over offspring sex. These results extend beyond sex allocation, as they question studies of population processes that assume equal input of sex chromosomes from fathers, and will also assist with future reproduction studies for management and conservation of marsupials.     

The evolution of unusual chromosomal systems in sciarid flies: intragenomic conflict and the sex ratio

A model is presented for the evolution of the sciarid chromosomal system. In this model, a driving X chromosome caused female-biased sex ratios. The drive was exploited by maternal autosomes that segregated with the X at spermatogenesis. Genes in mothers converted some of their XX daughters into sons by eliminating a paternal X from the embryonic soma. L chromosomes were derived from X chromosomes and favored male-biased sex ratios. An X' chromosome arose that suppressed the effects of L chromosomes. The 1:1 sex ratio is a stalemate between the X' and X'X mothers causing all-female broods and the L chromosomes in XX mothers causing all-male broods. Any element (such as an L chromosome) that is preferentially transmitted through one sex will be selected to bias the sex ratio towards this sex.     

Sex ratio variation in the cooperatively breeding alpine marmot Marmota marmota

In cooperatively breeding vertebrate species, a clear theoreticalprediction about the direction of sex ratio adjustment can bemade: mothers should bias the sex ratio of their offspring towardsthe helping sex when helpers are absent. A consistent trendin the direction predicted by theory exists in cooperative birds,but theory is still poorly tested in cooperative mammals. Here,multivariate analyses are applied to a long-term data set totest this prediction in two ways in the alpine marmot: (1) acrossfemales in a population and (2) in individual females acrossmultiple years. It was shown that in the alpine marmot offspringsex ratio was biased towards the helping sex (males) when helperswere absent, whereas helped mothers produced unbiased sex ratio.Unhelped mothers did not adjust the litter size but producedmore sons and fewer daughters than helped mothers. These resultssupport the theoretical prediction and explain well the malebias observed among juvenile alpine marmots at the populationlevel. The occurrence of possible sex ratio manipulations incooperatively breeding vertebrates is also discussed.     

Which way to manipulate host reproduction? Wolbachia that cause cytoplasmic incompatibility are easily invaded by sex ratio-distorting mutants

The bacterium Wolbachia manipulates its hosts by inducing cytoplasmic incompatibility (CI), where zygotes formed from crosses between uninfected mothers and infected fathers die. In addition, it distorts the host's sex ratio via male killing, parthenogenesis induction, or feminization. Here, we model transitions between these states, examining the evolution of mutants of CI strains that retain both the ability to induce and resist CI but, in addition, cause sex ratio distortion. The model shows that CI strains are highly susceptible to invasion and subsequent elimination by these mutants. For all three types of sex ratio distortion, there is some parameter space in which the strain showing sex ratio distortion becomes extinct following exclusion of the progenitor CI strain, leaving the population uninfected. Extinction of the new Wolbachia strain is common for the case of male killing but rarer for parthenogenesis induction and feminization. Our models predict that CI strains of Wolbachia will occur most commonly in hosts that are male heterogametic, where there is little interaction between siblings because these hosts are unlikely to favor the spread of male killing, feminization, or parthenogenesis induction. The models raise the question of why CI strains apparently predominate in nature, and it is suggested that this is a result of either fewer restrictions on CI strains spreading through novel host populations or restrictions to the mutability of Wolbachia strains.     

ABO hemolytic disease of the newborn as a selection mechanism at the ABO locus

Data from the period 1951 to 1967 were collected from the records at the Milwaukee Blood Center on 380 cases of ABO hemolytic disease to determine if ABO incompatibility may be regarded as a selection mechanism at the ABO locus. In comparison with infants of ABO compatible parents the affected infants had significantly lower hemoglobin and hematocrit values and higher bilirubin concentrations. Forty-eight percent of the affected showed a positive direct antiglobulin test, 81% showed increased numbers of reticulocytes and 92% had spherocytosis. Since affected infants are considered to be in grave danger when high concentrations of bilirubin are present it is significant that 169 individuals (44%) required exchange transfusions. Compared with the number of live births in Milwaukee for the same period this represents a frequency of one in every 1,654 live births so that ABO incompatibility may be regarded as an important mechanism of natural selection. Since it was found that 98.7% of the mothers of the affected infants are of blood group O, the affected infants are therefore heterozygous (AO or BO) and selection due to ABO incompatibility would have its greatest effect upon the lowest allele frequencies in a population.     

Maternal size and age affect offspring sex ratio in the solitary egg parasitoid Anaphes nitens

In this study, the effects of maternal age, diet, and size on offspring sex ratio were investigated for the solitary egg parasitoid, Anaphes nitens Girault (Hymenoptera: Mymaridae), both outdoors, during the winter, and inside a climatic chamber under favourable constant conditions. During the winter of 2005–2006, each of seven groups containing 40 1‐day‐old females was mated and randomly distributed among two treatments: (treatment 1) a droplet of undiluted honey ad libitum + one fresh egg capsule of the snout beetle Gonipterus scutellatus Gyllenhal (Coleoptera: Curculionidae) as host; (treatment 2) drops of water + one fresh egg capsule of G. scutellatus. We recorded the lifetime fecundity, the daily sex allocation, and the lifetime offspring sex ratio to study the existence of a relationship with maternal characteristics. Moreover, we assessed the effect of location (outdoors vs. indoors) and group (groups are representative of early, mid, and late winter) on sex ratio. The most important factor that biased the sex ratio was maternal body size: larger females of both treatments produced more female offspring. As females of A. nitens could gain more advantage than males from body size, larger mothers have a higher fitness return if they produce more daughters. The effect of the treatment was significant: starved females produced more females. Location and group were not significant. Fecundity and sex ratio were age dependent. Old mothers that received honey (treatment 1) had fewer offspring and a more male‐biased offspring sex ratio, probably due to reproductive senescence and sperm depletion. Starved females (treatment 2) experienced reproductive decline earlier, perhaps because they invested more energy in maintenance rather than in reproduction.     

An analysis of birth sex ratio bias in captive prosimian species

The extent to which sex ratio bias is a common reproductive characteristic of prosimians has not been well established. The present study analyzed reproduction in 13 breeding groups of captive prosimians for evidence of birth sex ratio bias. A substantial male bias was demonstrated in nongregarious, but not gregarious, breeding groups. Analyses of birth sex ratios of individual mothers suggested that the observed bias did not result from the tendency of a few mothers to overproduce males, but rather from a small but reliable excess of male births in general. An examination of infant mortality revealed that male Otolemur garnettii and Microcebus murinus infants were more vulnerable to preweaning mortality, whereas female Eulemur fulvus albifrons infants were more vulnerable. An analysis of birth order by sex found that mothers of one group (O. garnettii) tended to produce males initially and females later. Additionally, a distinct pattern of birth seasonality was noted among Malagasy prosimians that was absent in the African prosimians. Greater length of period of sexual receptivity for nongregarious females as compared to gregarious females is proposed as a possible mechanism of male birth sex ratio bias. © 1996 Wiley-Liss, Inc.     

Simultaneous failure of two sex-allocation invariants: implications for sex-ratio variation within and between populations

Local mate competition (LMC) occurs when male relatives compete for mating opportunities, and this may favour the evolution of female-biased sex allocation. LMC theory is among the most well developed and empirically supported topics in behavioural ecology, clarifies links between kin selection, group selection and game theory, and provides among the best quantitative evidence for Darwinian adaptation in the natural world. Two striking invariants arise from this body of work: the number of sons produced by each female is independent of both female fecundity and also the rate of female dispersal. Both of these invariants have stimulated a great deal of theoretical and empirical research. Here, we show that both of these invariants break down when variation in female fecundity and limited female dispersal are considered in conjunction. Specifically, limited dispersal of females following mating leads to local resource competition (LRC) between female relatives for breeding opportunities, and the daughters of high-fecundity mothers experience such LRC more strongly than do those of low-fecundity mothers. Accordingly, high-fecundity mothers are favoured to invest relatively more in sons, while low-fecundity mothers are favoured to invest relatively more in daughters, and the overall sex ratio of the population sex ratio becomes more female biased as a result.     

Exogenous sex hormone exposure and the risk for VACTERL association

In several studies investigators have suggested that maternal use of exogenous sex hormones during early pregnancy may be associated with various congenital malformations. A group of malformations, the VACTERL (vertebral, anal, cardiac, trachea, esophageal, renal, limb-acronym) association, has been statistically associated with maternal exposure to exogenous sex hormones during the first trimester of pregnancy. The VACTERL association is a nonrandom group of major malformations that occur together more often than would be expected on the basis of chance. To assess this association, we conducted a case-control study of first-trimester exposure to sex hormones among mothers of 34 infants with the VACTERL association and of 1,024 comparison infants with one or more of ten major malformations or Down syndrome. The study subjects were malformed infants born between July 1970 and June 1979 and registered in a population-based birth defects registry. Information concerning the use of exogenous sex hormones during pregnancy was obtained by systematically interviewing the mothers of the malformed infants. Most of the mothers were interviewed within 6 months of their children's births. Each mother was interviewed within a year of her child's birth. We found an odds ratio of 0.98 (90% confidence limits 0.40, 2.38) for the relationship between VACTERL association and use of any sex hormone in the first trimester of pregnancy. Our study had adequate statistical power to detect a true relative risk of 2.8 or greater.     

ABO blood groups and fertility—with special reference to intrauterine selection due to materno-fetal incompatibility

The purpose of the present investigation was to study whether there is differential fertility between different mating types of ABO blood group system. Selective force which is operating through maternal-fetal incompatibility has been observed in the differential fertility between compatible and incompatible mating groups in the present sample of 183 families of Visakhapatnam town of Andhra Pradesh, India. The differences in the mean numbers of pregnancies as well as living children between the two major mating groups, compatible and incompatible are significant. The fertility rates of O fathers and O mothers were significantly higher than those in matings in which neither parents belongs to O. The selection is operating to reduce the gene ratio of A and to increase the gene ratios of O and B in this sample.     

Mothers under stress? Hatching sex ratio in relation to maternal baseline corticosterone in the common tern (Sterna hirundo)

Sex ratio of progeny should be balanced if costs and benefits of rearing sons and daughters are equal. However, shifts in sex ratio have been demonstrated across bird species and it was suggested that females are able to adjust the primary sex ratio. One possible mechanism is the glucocorticoid corticosterone which rises under stressful conditions and can be deposited into egg yolk by mothers. We analysed primary sex ratio of common terns Sterna hirundo from 2006 to 2008 and related it to maternal baseline corticosterone level, laying date and year. Therefore, we took 101 blood samples of 71 breeding females via blood sucking bugs, a method with negligible stress for the birds. Sex ratio did not differ from parity in any of the analysed years, which were characterized by poor food availability and breeding success. Only within 1 year there was a tendency for more females in the last hatched chick. Neither corticosterone level nor laying date or year showed an influence on hatching sex ratio. The negative result concerning primary sex ratio and maternal baseline corticosterone level might suggest conditions to be good enough for mothers to prevent them from depositing high levels of corticosterone into eggs.