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1,610 results for “ratio”
Data from: Sperm competitive ability evolves in response to experimental alteration of operational sex ratio
In naturally polygamous organisms such as Drosophila, sperm competitive ability is one of the most important components of male fitness and is expected to evolve in response to varying degrees of male–male competition. Several studies have documented the existence of ample genetic variation in sperm competitive ability of males. However, many experimental evolution studies have found sperm competitive ability to be unresponsive to selection. Even direct selection for increased sperm competitive ability has failed to yield any measurable changes. Here we report the evolution of sperm competitive ability (sperm defense-P1, offense-P2) in a set of replicate populations of Drosophila melanogaster subjected to altered levels of male–male competition (generated by varying the operational sex ratio) for 55–60 generations. Males from populations with female-biased operational sex ratio evolved reduced P1 and P2, without any measurable change in the male reproductive behavior. Males in the male-biased regime evolved increased P1, but there was no significant change in P2. Increase in P1 was associated with an increase in copulation duration, possibly indicating greater ejaculate investment by these males. This study is one of the few to provide empirical evidence for the evolution of sperm competitive ability of males under different levels of male–male competition.
Data from: Transmission ratio distortion is frequent in Arabidopsis thaliana controlled crosses
The equal probability of transmission of alleles from either parent during sexual reproduction is a central tenet of genetics and evolutionary biology. Yet, there are many cases where this rule is violated. The preferential transmission of alleles or genotypes is termed transmission ratio distortion (TRD). Examples of TRD have been identified in many species, implying that they are universal, but the resolution of species-wide studies of TRD are limited. We have performed a species-wide screen for TRD in over 500 segregating F2 populations of Arabidopsis thaliana using pooled reduced-representation genome sequencing. TRD was evident in up to a quarter of surveyed populations. Most populations exhibited distortion at only one genomic region, with some regions being repeatedly affected in multiple populations. Our results begin to elucidate the species-level architecture of biased transmission of genetic material in A. thaliana, and serve as a springboard for future studies into the biological basis of TRD in this species.
Data from: Dispersal, niche breadth, and population extinction/colonization ratios predict range size in North American dragonflies
1. Species' range sizes are shaped by fundamental differences in species' ecological and evolutionary characteristics, and understanding the mechanisms determining range size can shed light on the factors responsible for generating and structuring biological diversity. Moreover, because geographic range size is associated with a species' risk of extinction and their ability to respond to global changes in climate and land use, understanding these mechanisms has important conservation implications. 2. Despite hypotheses that dispersal behaviour is a strong determinant of species range areas, few data are available to directly compare the relationship between dispersal behaviour and range size. Here, we overcome this limitation by combining data from a multi-species dispersal experiment with additional species-level trait data that are commonly hypothesized to affect range size (e.g. niche-breadth, local abundance, and body size, etc.). This enables us to examine the relationship between these species-level traits and range size across North America for fifteen dragonfly species. 3. Ten models based on a priori predictions about the relationship between species traits and range size were evaluated and two models were identified as good predictors of species range size. These models indicated that only two species' level traits, dispersal behaviour and niche breadth were strongly related to range size. The evidence from these two models indicated that dragonfly species that disperse more often and further had larger North American ranges. 4. Extinction and colonization dynamics are expected to be a key linkage between dispersal behaviour and range size in dragonflies. To evaluate how extinction and colonization dynamics among dragonflies were related to range size we used an independent data set of extinction and colonization rates for eleven dragonfly species and assessed the relationship between these populations rates and North American range areas for these species. 5. We found a negative relationship between North American range size and species' extinction to colonization ratios. Our results indicate that metapopulation dynamics act to shape the extent of species' continental distributions. These population dynamics are likely to interact with dispersal behaviour, particularly at species range margins, to determine range limits and ultimately species range sizes.
Data from: What is behind the variation in mate quality dependent sex ratio adjustment? – A meta-analysis
Theory predicts that parents adjust the sex ratio of their brood to the sexually selected traits of their mate because the reproductive success of sons may be more dependent on inherited paternal attractiveness than that of daughters. Empirical studies vary in terms of whether they support the theory, and this variation has often been regarded as evidence against sex ratio adjustment or has been ascribed to methodological differences. Applying phylogenetic meta-analyses, we aimed to find biological explanations for the variation observed in songbirds. In particular, we tested the role extra-pair paternity, because infidelity occurs in the majority of these species and may reduce the adaptive value of adjusting brood sex ratio to the phenotype of the social mate. However, we found that the variation in effect sizes was unrelated to the proportion of extra-pair paternity. Thus future studies should consider that mate quality dependent sex ratio adjustment may be driven by direct (material) rather than indirect (genetic) benefits. We also tested if the effect sizes are influenced by whether the focal male trait is indeed under sexual selection as it is assumed by the sex allocation theory. We found that for male traits with proven role in sexual selection, effect sizes significantly differed from the null expectation of random production of sons and daughters. For male traits with only presumed sexual role in sexual selection, the deviation from the null expectation was less convincing, and the effect sizes were significantly smaller. This result indicates that studies that neglect the assumptions of the hypotheses concerned, may lead to the underestimation of the mean effect size and, eventually, false conclusions.
Data from: Grazing pressure affects offspring sex ratio in a socially monogamous passerine on the Tibet Plateau
Livestock grazing can affect habitat structure and availability of arthropod prey for grassland birds, and ultimately determines habitat quality. The habitat quality may affect breeding strategies (e.g. sex ratio adjustment) in bird species, but yet studies investigating grazing intensity on offspring sex ratio are still rare. In this paper, we examined the effect of grazing intensity by livestock on the secondary sex ratio of an alpine-steppe passerine, the Isabelline Wheatear Oenanthe isabellina, on the Tibet Plateau. Offspring sex ratio of Isabelline Wheatears significantly correlated with a quadratic term -- (grazing intensity)2. The wheatears nesting in areas grazed at low intensity by mixed livestocks produced significantly more sons than those in ungrazed area (0.41 vs. 0.58, Z=-2.836, P=0.005), while brood sex ratios from other treatments (ungrazing vs. intensive grazing and low-intensity grazing vs. intensive grazing) did not differ significantly. Variation in offspring sex ratio was not related to other factors such as maternal condition, paternal condition and other two-way interactions. These results suggest that breeding birds of grasslands are sensitive to variation in habitat conditions, and provide additional evidence that grazing intensity affects avian reproduction in cryptic ways that are rarely studied. Our findings suggest that flexible management including timely rotational grazing is needed to optimize bird species reproduction and maintain ecosystem health.
Data from: Genetic mapping a meiotic driver that causes sex ratio distortion in the mosquito Aedes aegypti
An endogenous meiotic driver in the dengue and yellow fever vector mosquito Aedes aegypti can cause highly male-biased sex ratio distortion in crosses from suitable genetic backgrounds. We previously selected a strain that carries a strong meiotic drive gene (D) linked with the male-determining allele (M) on chromosome 1 in A. aegypti. Here we performed segregation analysis of the MD locus among backcross (BC1) progeny from a driver male and drive-sensitive females. Assessment of sex ratios among BC2 progeny showed ~5.2% recombination between the MD locus and the sex determination locus. Multipoint linkage mapping across this region revealed consistent marker orders and recombination frequencies with the existing reference linkage map and placed the MD locus within a 6.5 cM interval defined by the LF159 locus and microsatellite marker 446GAA, which should facilitate future positional cloning efforts.
Data from: Digit ratio (2D:4D) and prosocial behavior in economic games: no direct correlation with generosity, bargaining, or trust-related behaviors
Prenatal exposure to sex hormones exerts organizational effects on the brain which have observable behavioral correlates in adult life. There are reasons to expect that social behaviors—fundamental for the evolutionary success of humans—might be related to biological factors such as prenatal sex hormone exposure. Nevertheless, the existing literature is inconclusive as to whether and how prenatal exposure to testosterone and estrogen, proxied by the second-to-fourth digit ratio (2D:4D), may predict non-selfish behavior. Here, we investigate this question using economic experiments with real monetary stakes and analyze five different dimensions of social behavior in a comparatively large sample of Caucasian participants (n=560). For both males and females, our results show no robust association between right- or left-hand 2D:4D and generosity, bargaining, or trust-related behaviors. Moreover, no differences in behavior were found according to sex. We conclude that there is no direct correlation between 2D:4D and these social behaviors.
Data from: Population structure leads to male-biased population sex ratios under environmental sex determination
Spatial structure has been shown to favor female-biased sex allocation, but current theory fails to explain male biases seen in many taxa, particularly those with environmental sex determination (ESD). We present a theory and accompanying individual-based simulation model that demonstrates how population structure leads to male-biased population sex ratios under ESD. Our simulations agree with earlier work showing that the high productivity of female-producing habitats creates a net influx of sex-determining alleles into male-producing habitats, causing larger sex ratio biases and lower productivity in male-producing environments (Harts et al. 2014). In contrast to previous findings, we show that male-biasing habitats disproportionately impact the global sex ratio, resulting in stable male-biased population sex ratios under ESD. The failure to detect a male bias in earlier work can be attributed to small subpopulation sizes leading to local mate competition, a condition unlikely to be met in most ESD systems. Simulations revealed that consistent male biases are expected over a wide range of population structures, environmental conditions, and genetic architectures of sex determination, with male excesses as large as 30 percent under some conditions. Given the ubiquity of genetic structure in natural populations, we predict that modest, enduring male biased allocation should be common in ESD species, a pattern consistent with reviews of ESD sex ratios.
Data from: Variation in adult sex ratio alters the association between courtship, mating frequency and paternity in the lek-forming fruitfly Ceratitis capitata.
The intensity with which males deliver courtship and the frequency with which they mate are key components of male reproductive success. However, we expect the strength of the relationship between these traits and a male's overall paternity to be strongly context dependent, e.g. to be altered significantly by the extent of post-mating competition. We tested this prediction in a lekking insect, Ceratitis capitata (medfly). We examined the effect of manipulating the sex ratio from male- to female-biased (high and low male competition, respectively) on courtship behaviour, mating frequency and paternity of focal males. Under high male competition, focal males delivered significantly more courtship but gained lower paternity than under lower competition. Paternity was positively associated with mating frequency and small residual testes size. However, the association between mating frequency and paternity was significantly stronger under low competition. We conclude that manipulation of sex ratio significantly altered the predictors of mating success and paternity. The relationship between pre- and post-mating success is therefore plastic and alters according to the prevailing level of competition. The results highlight the importance of post-copulatory processes in lekking species and illuminate selection pressures placed on insects such as medflies that are mass reared for pest control.
Data from: Evolutionarily stable sex ratios and mutation load
Frequency-dependent selection should drive dioecious populations toward a 1:1 sex ratio, but biased sex ratios are widespread, especially among plants with sex chromosomes. Here, we develop population genetic models to investigate the relationships between evolutionarily stable sex ratios, haploid selection, and deleterious mutation load. We confirm that when haploid selection acts only on the relative fitness of X and Y-bearing pollen and the sex ratio is controlled by the maternal genotype, seed sex ratios evolve toward 1:1. When we also consider haploid selection acting on deleterious mutations, however, we find that biased sex ratios can be stably maintained, reflecting a balance between the advantages of purging deleterious mutations via haploid selection, and the disadvantages of haploid selection on the sex ratio. Our results provide a plausible evolutionary explanation for biased sex ratios in dioecious plants, given the extensive gene expression that occurs across plant genomes at the haploid stage.
Data from: Genetics and genomics of an unusual selfish sex ratio distortion in an insect
Diverse selfish genetic elements have evolved the ability to manipulate reproduction to increase their transmission, and this can result in highly distorted sex ratios. Indeed, one of the major explanations for why sex determination systems are so dynamic is because they are shaped by ongoing coevolutionary arms races between sex ratio distorting elements and the rest of the genome. Here, we use genetic crosses and genome analysis to describe an unusual sex ratio distortion with striking consequences on genome organization in a booklouse species, Liposcelis sp. (Insecta: Psocodea), in which two types of females coexist. Distorter females never produce sons but must mate with males (the sons of nondistorting females) to reproduce. Although they are diploid and express the genes inherited from their fathers in somatic tissues, distorter females only ever transmit genes inherited from their mothers. As a result, distorter females have unusual chimeric genomes, with distorter-restricted chromosomes diverging from their nondistorting counterparts and exhibiting features of a giant nonrecombining sex chromosome. The distorter-restricted genome has also acquired a gene from the bacterium Wolbachia, a well-known insect reproductive manipulator; we found that this gene has independently colonized the genomes of two other insect species with unusual reproductive systems suggesting possible roles in sex ratio distortion in this remarkable genetic system.
Data from: Morphological and moisture availability controls of the leaf area-to-sapwood area ratio: analysis of measurements on Australian trees
1. The leaf area-to-sapwood area ratio (LA:SA) is a key plant trait that links photosynthesis to transpiration. The pipe model theory states that the sapwood cross-sectional area of a stem or branch at any point should scale isometrically with the area of leaves distal to that point. Optimization theory further suggests that LA:SA should decrease toward drier climates. Although acclimation of LA:SA to climate has been reported within species, much less is known about the scaling of this trait with climate among species. 2. We compiled LA:SA measurements from 184 species of Australian evergreen angiosperm trees. The pipe model was broadly confirmed, based on measurements on branches and trunks of trees from one to 27 years old. Despite considerable scatter in LA:SA among species, quantile regression showed strong (0.2 < R1 < 0.65) positive relationships between two climatic moisture indices and the lowermost (5%) and uppermost (5–15%) quantiles of log LA:SA, suggesting that moisture availability constrains the envelope of minimum and maximum values of LA:SA typical for any given climate. 3. Interspecific differences in plant hydraulic conductivity are probably responsible for the large scatter of values in the mid-quantile range and may be an important determinant of tree morphology.
POPC @ 310K, varying water-to-lipid ratio. Model by Maciejewski and Rog
<p>Input parameter files and parts of the resulting trajectories for a POPC bilayer simulation with varying water-to-lipid ratios. The used ratios are 50, 25, 20, 15, 10, and 5. The force field is an extension to the OPLS-based force field by the same authors [1]. The same POPC force field has also been employed in [2].</p> <p>––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––</p> <p>Files:</p> <p>XX.tpr – XX waters per lipid; run input file for Gromacs versions 4.5.5 and above. </p> <p>XXWperL_YYns.xtc – The last YY ns of a 100 or 90 ns long simulation (50 ns discarded from the beginning). XX waters per lipid.</p> <p>––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––</p> <p>This data is used in the project "Matching lipid force fields with NMR data", see: http://nmrlipids.blogspot.fi and referred to in the blog as 'MacRog'</p> <p>[1] Maciejewski, A., Pasenkiewicz-Gierula, M., Cramariuc, O., Vattulainen, I., and Rog, T. <strong>Refined OPLS All-Atom Force Field for Saturated Phosphatidylcholine Bilayers at Full Hydration.</strong> The Journal of Physical Chemistry B <strong>118</strong>, 4571–4581 (2014). DOI: 10.1021/jp5016627</p> <p>[2] Kulig, W., Jurkiewicz, P., Olzynska, A., Tynkkynen, J., Javanainen, M., Manna, M., Rog, T., Hof, M., Vattulainen, I. and Jungwirth, P. <strong>Experimental determination and computational interpretation of biophysical properties of lipid bilayers enriched by cholesteryl hemisuccinate.</strong> Biochimica et Biophysica Acta (BBA) - Biomembranes <strong>1848</strong>, 422–432 (2015). DOI: 10.1016/j.bbamem.2014.10.032</p> <p> </p>
Neutrophil/Lymphocyte Ratio has a Prognostic Value for Patients with Terminal Cancer
<p>datasets</p>
Golden Ratio Speech Codec (img)
<p>Original speech signal and Golden ratio speech codec resultant speech signal.</p>
Leaf carbon istope ratio database in China
<p>These data used in revised manuscript (Spatial patterns of leaf δ13C and its relationship with plant functional groups and environmental factors in China, JGR-Biogeosciences, ID:2016JG003529RRR).The leaf carbon isotope(δ13C) dataset in China was extracted from the published figures and tables using GetData Graph Digitizer version 2.24;The climate data derived from 756 meteorological stations between 1992 and 2013 in China by Zhu et al.</p>
Figure 3. Chemical ratio variation diagrams, Tumbarumba corundums. Type 1A in The Tumbarumba Basaltic Gem Field, New South Wales: In Relation to Sapphire-Ruby Deposits of Eastern Australia
Figure 3. Chemical ratio variation diagrams, Tumbarumba corundums. Type 1A (O), Type 1B (Z), Type 2 (+), Type 3 (Δ), Type 4 (•), Type 5 (-). a—Cr 2O3/Ga2O3 against Fe2O3/Cr2O3. b—Cr 2O3/Ga2O3 against Fe2O3/TiO2.
LATEst: Efficient computation of hazard ratios and identification of causal relationships using 'natural experiments' in medical informatics databases
Open the record for dataset details and reuse information.
Catalyst-free MBE growth of Monocrystalline PbSnTe nanowires with tunable aspect ratio
<p>Link to the image analysis software: <a title="https://github.com/mcpim/APIMs" href="https://github.com/mcpim/APIMs">https://github.com/mcpim/APIMs</a></p>
Figure 1 from: Hristov M, Sabit Z, Kirilov T, Bakalov D, Tzoneva R, Apostolova S, Georgieva I, Andreeva-Gateva P (2024) Effects of riboflavin on hyperalgesia and serum glutamine-to-glutamate ratio in rats with painful diabetic neuropathy. Pharmacia 71: 1-7. https://doi.org/10.3897/pharmacia.71.e120921
Figure 1 Effects of riboflavin on changes in pain threshold were investigated using the paw pressure test. Streptozotocin administration significantly induced mechanical hyperalgesia by reducing the mechanical threshold and enhancing paw withdrawal responses, while supplementation with Vitamin B2 effectively mitigated mechanical hyperalgesia. Significant differences compared to the control group (Normal) are denoted as *P < 0.05, while significant differences compared to the diabetic group (Diabetic) are denoted as ##P < 0.01. n=8 animals per group.
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