Role Of Sex Ratio Research Articles

Analysis of Bos taurus and Sus scrofa X and Y chromosome transcriptome highlights reproductive driver genes.

The biology of sperm, its capability of fertilizing an egg and its role in sex ratio are the major biological questions in reproductive biology. To answer these question we integrated X and Y chromosome transcriptome across different species: Bos taurus and Sus scrofa and identified reproductive driver genes based on Weighted Gene Co-Expression Network Analysis (WGCNA) algorithm. Our strategy resulted in 11007 and 10445 unique genes consisting of 9 and 11 reproductive modules in Bos taurus and Sus scrofa, respectively. The consensus module calculation yields an overall 167 overlapped genes which were mapped to 846 DEGs in Bos taurus to finally get a list of 67 dual feature genes. We develop gene co-expression network of selected 67 genes that consists of 58 nodes (27 down-regulated and 31 up-regulated genes) enriched to 66 GO biological process (BP) including 6 GO annotations related to reproduction and two KEGG pathways. Moreover, we searched significantly related TF (ISRE, AP1FJ, RP58, CREL) and miRNAs (bta-miR-181a, bta-miR-17-5p, bta-miR-146b, bta-miR-146a) which targeted the genes in co-expression network. In addition we performed genetic analysis including phylogenetic, functional domain identification, epigenetic modifications, mutation analysis of the most important reproductive driver genes PRM1, PPP2R2B and PAFAH1B1 and finally performed a protein docking analysis to visualize their therapeutic and gene expression regulation ability.

Role of Sex Ratio and Density on Fertilization Success of Intensively Cultured Endangered Woundfin

Abstract Woundfin Plagopterus argentissimus are a small, endangered cyprinid found solely in the Virgin River across Utah, Arizona, and Nevada. As of now, only three facilities culture Woundfin for conservation propagation purposes, but there is growing concern that current extensive culture protocols are not meeting the conservation recovery goals outlined in the Virgin River Resource Management and Recovery Program. The development of alternative rearing methodology, like effective intensive culture conditions, could help increase production to more effectively meet the conservation propagation needs for this species. Our goal was to assess the effect of different sex ratios and fish densities on reproductive success at indoor facilities. We measured fertilization success at three different sex ratios (1:1, 1:3, 1:5; female:male) and three different fish densities (0.05, 0.21, and 0.47 fish/L) in a laboratory setting. Sex ratio did not significantly affect fertilization success (P = 0.73). Fertilization was completely inhibited at a density of 0.05 fish/L, but there was no difference in fertilization success between the two other density treatments (P = 0.92). Our findings suggest that a density greater than 0.05 fish/L and a sex ratio of 1:1, 1:3, or 1:5 will likely enhance fertilization success. The results and conclusions of this paper provide valuable rearing information for the Virgin River Resource Management and Recovery Program and hatchery managers attempting to increase production of Woundfin in an intensive culture setting.

Evolution of sexual size dimorphism and its relationship with sex ratio in carabid beetles of Genus Ceroglossus Solier

Abstract Although the degree of mate competition, given extreme differences in sex ratio, explains much of the pattern of male-biased size dimorphism among diverse taxa, it fails for some species which have potential for intense male competition for mates and yet exhibit little or no sexual size dimorphism (SSD). This fact suggest that species with low SSD should be express the effect of evolutionary pressure in non-obvious geometrical shape promoted by sex ratio in an evolutionary time scale. To evaluate this hypothesis we used phylogenetic comparative method in a Bayesian framework to investigate the evolution of SSD and the role of sex ratio at inter-specific level in the species of Ceroglossus (Coleoptera: Carabidae). In our results the proportion farthest from 1:1 is associated with more disparate body shape, even though the entire group has minimum variation in sex ratio, which is an intrinsic life history character of this group considering its phylogenetic conservatism or phylogenetic signal. We suggest that the sex ratio has determined the dimorphism degree during evolution of this group, since both traits have increased or decreased together during the species divergence (i.e. positive phylogenetic correlation: r2≈0.85). We suggest that morphological studies of SSD will benefit from using comparative method with Bayesian approaches to assess the effect of phylogenetic history and its uncertainty. Finally, this will be allow to researchers to quantify the uncertainty of specific evolutionary hypotheses accounting for observed sexual dimorphism patterns.

Patch exploitation strategies of parasitoids: The role of sex ratio and forager's interference in structuring metapopulations

We use a mathematical model to explore the effects of parasitoid reproductive strategies and foraging behavior in response to spatio-temporal variations in the patch quality of a host–parasitoid metapopulation system. The variations of patch quality over the landscape were measured by the presence of parasitoid competitors and the density of hosts. The parasitoid responses to patch quality are given by three different foraging behaviors: (i) the decision to remain in or leave the current patch; (ii) the control of progeny's sex ratio and (iii) competitive abilities, measured by changes in the potential to attack hosts due to interference from conspecifics in the exploited patch. We study the dynamics of host and parasitoid populations characterized by different levels of density-dependent sex ratio adjustment and interference competition. Our results show that population stability increases when parasitoid growth is correlated with patch conditions. The effect of sex ratio adjustment alone does not account for qualitative changes to system dynamics or to the distribution patterns of species. In contrast, the degree of competitive interference among the parasitoids plays a crucial role in constraining the parasitoids’ potential to reduce host populations and in determining the species’ distribution in the landscape. We found that high levels of interference competition disrupt the population dynamics within a patch and allows hosts to completely dominate the landscape. This study shows that the inclusion of life history traits and the co-evolutionary aspects of host–parasitoid interaction can help researchers to understand species distribution patterns in the landscape.

Marrying Up: The Role of Sex Ratio in Assortative Matching

We investigate the effect of a change in the sex ratio on assortative matching in the marriage market using a large negative exogenous shock to the French male population due to WWI casualties. We analyze a novel data set that links marriage-level data to both French censuses of population and regional data on military mortality. We instrument the potentially endogenous sex ratio with military mortality, which exhibits exogenous geographic variation. We find that men married women of higher social class than themselves (married up) more in regions that experienced a larger decrease in the sex ratio due to higher military mortality. A decrease in the sex ratio from one man for every woman to 0.90 men for every woman increased the probability that men married up by 8.2 percentage points. These findings shed light on individuals’ preferences for spouses. Rather than preferring to marry spouses with similar characteristics, individuals seem to prefer to marry higher-class spouses, but cannot do so when the sex ratio is balanced.

Marrying Up: The Role of Sex Ratio in Assortative Matching

We test the effect of a change in the sex ratio on marital assortative matching by social class using a large negative exogenous shock to the French male population due to WWI casualties. We analyze a novel data set that links marriage-level data to both French censuses of population and regional data on military mortality. We instrument the sex ratio in a region with military mortality, which exhibits exogenous geographic variation. We find that men married women of higher social class than themselves (married up) more in regions that experienced larger decreases in the sex ratio. A decrease in the sex ratio from one man for every woman to 0.90 men for every woman increased the probability that men married up by 8 percentage points. These findings shed light on individuals’ preferences for spouses. Rather than preferring to marry spouses from the same social class, men seem to prefer to marry higher-class spouses, but cannot do so when the sex ratio is balanced.

Marrying Up: The Role of Sex Ratio in Assortative Matching

We assemble a novel dataset to study the impact of male scarcity on marital assortative matching and other marriage market outcomes using the large shock that WWI caused to the number of French men. Using a difference-in-differences approach, we find that postwar in regions with higher mortality rates: men were less likely to marry women of lower social classes; men were more likely and women less likely to marry; out-of-wedlock births increased; divorce rates decreased; and the age gap decreased. These findings are consistent with men improving their position in the marriage market as they become scarcer. (JEL J12, J16, N34)

The role of sex ratio on spawning performance and on the free and conjugated sex steroids released into the water by common dentex ( Dentex dentex) broodstock

This paper reports the results of an experiment to determine whether sex ratio has any effect on the spawning efficiency of common dentex, Dentex dentex, broodstock. The paper also reports preliminary data on diurnal changes in water concentrations of steroids (measured on two separate occasions) in the same groups of fish. These latter observations were made to determine whether, using a non-invasive procedure, it was possible to relate hormonal changes in the fish to the “success of spawning.” Mature fish were placed in broodstock tanks at three different sex ratios (Group A, 4♀:1♂; Group B, 1♀:1♂; and Group C, 1♀:4♂) and regularly monitored for egg production. At 18 days after the start of spawning, water samples were removed from all three tanks at 130 min intervals over a period of 24 h. At the end of spawning, water samples were removed at 4 h intervals. Free and conjugated steroids were extracted from the water and measured by radioimmunoassay. The highest number of eggs released, percentage of viable eggs, number of spawnings, spawning index, and relative fecundity were observed in Group B (1♀:1♂). The sex steroids testosterone (T), 11-ketotestosterone (11-KT), 17,20β-P, and 17,20β, 21-trihydroxy-pregn-4-en-3-one could be readily detected in water from all tanks. Concentrations of the conjugated forms (sulphate and glucuronide) were higher than those of the free form—with the exception of sulphated T and 11-KT. The concentrations of glucuronidated 17,20β-P, sulphated 17,20β-P, and free T appeared to be associated with the number of females in the tank and glucuronidated 11-KT concentrations with the number of males. In the first set of water samples (taken during the spawning period) there was also evidence for a cycle in steroid release with an acrophase during the afternoon and early evening, a few hours before the actual act of spawning. We were not able to show any association between steroid concentrations and success of spawning. However, since the data were derived from a “snapshot” of just a single day in what was a prolonged spawning period, this was perhaps not surprising. The results from the present study will help us to design experiments that are more able to answer this question.

The Marriage Squeeze Interpretation of Dowry Inflation: A Comment

In a recent paper, Rao (1993) advanced a marriage squeeze explanation to the secular rise in real dowries, so-called dowry inflation, witnessed in India. Arguing that the relevant ages with respect to marriage are 10–19 for women and 20–29 for men, Rao found that the ratio of women to men in those age groups had increased over time. Moreover, this sex ratio was found to have a positive and significant impact on dowry when one controls for differences in traits of brides and grooms. The empirical results presented here suggest that Rao’s findings are not robust. Using the same data, I fail to replicate his main result, that is, that the sex ratio (women 10–19/men 20–29) has a positive impact on dowries. Moreover, Rao’s specification—regressing dowries on differences in spouses’ traits (bride’s minus groom’s)—imposes the restriction that attributes influence dowries in a symmetrical fashion, ignoring compelling evidence against that assumption. I find that regressing dowry on individual traits instead of differences improves the model fit considerably.

Role of sex ratio in the evolution of eusociality in haplodiploid social insects

In his study of a kin selection model for the evolution of workers' behavior in an incipiently social insect, Craig (1979) found that the haplodiploid mode of sex determination, combined with a female-biased sex ratio, cannot accelerate an evolutionary trend toward eusociality. This seems to contradict to Hamilton's (1964) theory. It is my intention to prove that Craig's result is due to the dependence of relative reproductive success in each sex on the sex ratio of a population. The oviposition of unfertilized eggs by workers is indispensable, in primitive stages in the evolution of eusociality, for maintaining the relative reproductive success of a female. Assuming that workers control the sex ratios, we can distinguish the following three evolutionary phases in accordance with the ratio N 2 N 10 (the ratio of the number of the queen's second brood to that of the progeny laid by workers derived from the same nest). During Phase 1 in which N 2 N 10 < 1 2 , the reproductive successes of a male and a female are equal, and Hamilton's rule holds. In Phase 2 in which 1 2 < N 2 N 10 < 3 2 , the queen produces females, and workers oviposit males. As N 2 N 10 increases, the sex ratio in the whole population becomes female-biased and relative reproductive success of a male increases. In Phase 3 in which N 2/ N 10 > 3 2 , the queen lays some male eggs in addition to female eggs. The sociality threshold ( B C ) crit the minimum value of the benefit/cost ratio leading to the evolution of altruism, is 2 3 on Phase 1. It rises threefold as N 2/N 10 increases in Phase 2, and, in Phase 3, it is twice as high as that in a diploid species. The anatomical and physiological characteristics of workers must have been so developed that they are efficient in helping activities after the beginning of eusociality. The evolutionary process before the beginning of helping behavior is also discussed. The egg laying by unmated females, which stay their mother's nest, seems to have been an important preadaptation for the evolution of eusociality in Hymenoptera.