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233 results for “sex determination”
Data from: Sex-determining chromosomes and sexual dimorphism: insights from genetic mapping of sex expression in a natural hybrid Fragaria × ananassa subsp. cuneifolia
We studied the natural hybrid (Fragaria × ananassa subsp. cuneifolia) between two sexually dimorphic octoploid strawberry species (Fragaria virginiana and Fragaria chiloensis) to gain insight into the dynamics of sex chromosomes and the genesis of sexual dimorphism. Male sterility is dominant in both the parental species and thus will be inherited maternally, but the chromosome that houses the sex-determining region differs. Thus, we asked whether (1) the cytotypic composition of hybrid populations represents one or both maternal species, (2) the sex-determining chromosome of the hybrid reflects the location of male sterility within the maternal donor species and (3) crosses from the hybrid species show less sexual dimorphism than the parental species. We found that F. × ananassa subsp. cuneifolia populations consisted of both parental cytotypes but one predominated within each population. Genetic linkage mapping of two crosses showed dominance of male sterility similar to the parental species, however, the map location of male sterility reflected the maternal donor in one cross, but not the other. Moreover, female function mapped to a single region in the first cross, but to two regions in the second cross. Aside from components of female function (fruit set and seed set), other traits that have been found to be significantly sexually dimorphic in the pure species were either not dimorphic or were dimorphic in the opposite direction to the parental species. These results suggest that hybrids experience some disruption of dimorphism in secondary sexual traits, as well as novel location and number of quantitative trait locus (QTL) affecting sex function.
Data from: Dmrt1 polymorphism covaries with sex-determination patterns in Rana temporaria
Patterns of sex-chromosome differentiation and gonadal development have been shown to vary among populations of Rana temporaria along a latitudinal transect in Sweden. Frogs from the northern-boreal population of Ammarnäs displayed well-differentiated X and Y haplotypes, early gonadal differentiation, and a perfect match between phenotypic and genotypic sex. In contrast, no differentiated Y haplotypes could be detected in the southern population of Tvedöra, where juveniles furthermore showed delayed gonadal differentiation. Here, we show that Dmrt1, a gene that plays a key role in sex determination and sexual development across all metazoans, displays significant sex differentiation in Tvedöra, with a Y-specific haplotype distinct from Ammarnäs. The differential segment is not only much shorter in Tvedöra than in Ammarnäs, it is also less differentiated and associates with both delayed gonadal differentiation and imperfect match between phenotypic and genotypic sex. Whereas Tvedöra juveniles with a local Y haplotype tend to ultimately develop as males, those without it may nevertheless become functional XX males, but with strongly female-biased progeny. Our findings suggest that the variance in patterns of sex determination documented in common frogs might result from a genetic polymorphism within a small genomic region that contains Dmrt1. They also substantiate the view that recurrent convergences of sex determination toward a limited set of chromosome pairs may result from the co-option of small genomic regions that harbor key genes from the sex-determination pathway.
Data from: Individual heterogeneity determines sex differences in mortality in a monogamous bird with reversed sexual dimorphism
Sex differences in mortality are pervasive in vertebrates, and usually result in shorter life spans in the larger sex, although the underlying mechanisms are still unclear. On the other hand, differences in frailty among individuals (i.e. individual heterogeneity), can play a major role in shaping demographic trajectories in wild populations. The link between these two processes has seldom been explored. We used Bayesian survival trajectory analysis to study age-specific mortality trajectories in the Eurasian sparrowhawk (Accipiter nisus), a monogamous raptor with reversed sexual size dimorphism. We tested the effect of individual heterogeneity on age-specific mortality, and the extent by which this heterogeneity was determined by average reproductive output and wing length as measures of an individual's frailty. We found that sex differences in age-specific mortality were primarily driven by the differences in individual heterogeneity between the two sexes. Females were more heterogeneous than males in their level of frailty. Thus, a larger number of females with low frailty are able to survive to older ages than males, with life expectancy for the least frail adult females reaching up to 4·23 years, while for the least frail adult males it was of 2·68 years. We found that 50% of this heterogeneity was determined by average reproductive output and wing length in both sexes. For both, individuals with high average reproductive output had also higher chances to survive. However, the effect of wing length was different between the two sexes. While larger females had higher survival, larger males had lower chances to survive. Our results contribute a novel perspective to the ongoing debate about the mechanisms that drive sex differences in vital rates in vertebrates. Although we found that variables that relate to the cost of reproduction and sexual dimorphism are at least partially involved in determining these sex differences, it is through their effect on the level of frailty that they affect age patterns of mortality. Therefore, our results raise the possibility that observed differences in age-specific demographic rates may in fact be driven by differences in individual heterogeneity.
Data from: Incubation temperature and parental identity determine sex in the Australian agamid lizard Ctenophorus pictus
Sex determination in Australian agamid lizards show a complex framework of different mechanisms, varying even among closely related taxa. It is clear that discrete classification of these species as either having genetic (GSD) or environmental sex determination (ESD) does not agree with empirical data. Although many species in this group show temperature-dependent sex determination (TSD), recent evidence suggests additional genetic or epigenetic effects. A proposed model explaining the adaptive significance and evolution of TSD in short-lived agamids predicts that selection will favor temperature-biased sex ratios in species with intense male-male competition. Here we use experimental incubation at (near) constant temperatures to test whether the sex of Australian painted dragons (Ctenophorus pictus) is influenced by temperature, building on previous research yet to have reached an agreement regarding the role of temperature in this species. In the present study, incubation temperature and parental identity affected hatchling sex suggesting that environment and genetics may work in concert to determine sex in this species. Although our results are consistent with TSD, our data cannot rule out a temperature-by-sex effect on egg or hatchling mortality. However, our findings together with the observed differences of sex determination systems in closely related species within this genus may provide novel opportunities to address fundamental questions in the evolution of sex determination systems.
Climate change, sex reversal, and lability of sex determining systems
Sex reversal at high temperatures during embryonic development (e.g. ZZ females) provides the opportunity for new genotypic crosses (e.g. ZZ male x ZZ female). This raises the alarming possibility that climatic warming could lead to the loss of an entire chromosome – one member of the sex chromosome pair (the Y or W) – and the transition of populations to environmental sex determination (ESD). Here we examine the evolutionary dynamics of sex-determining systems exposed to climatic warming using theoretical models. We found that the loss of sex chromosomes is not an inevitable consequence of sex reversal. A large frequency of ZZ sex reversal (50% reversal from male to female) typically divides the outcome between loss of the ZW genotype and the stable persistence of ZZ males, ZW females, and ZZ females. The amount of warming associated with sex chromosome loss depended on several features of wild populations – environmental fluctuation, immigration, heritable variation in temperature sensitivity, and differential fecundity of sex-reversed individuals. Chromosome loss was partially or completely buffered when sex-reversed individuals suffered a reproductive fitness cost, when immigration occurred, or when heritable variation for temperature sensitivity existed. Thus, under certain circumstances, sex chromosomes may persist cryptically in systems where the environment is the predominant influence on sex.
Data from: Sex determination in the wild: a field application of loop-mediated isothermal amplification successfully determines sex across three raptor species
PCR-based methods are the most common technique for sex determination of birds. Although these methods are fast, easy and accurate, they still require special facilities that preclude their application outdoors. Consequently, there is a time lag between sampling and obtaining results that impedes researchers to take decisions in situ and in real time considering individuals' sex. We present an outdoor technique for sex determination of birds based on the amplification of the duplicated sex-chromosome-specific gene Chromo-Helicase-DNA binding protein using a loop-mediated isothermal amplification (LAMP). We tested our method on Griffon Vulture (Gyps fulvus), Egyptian Vulture (Neophron percnopterus) and Black Kite (Milvus migrans) (family Accipitridae). We introduce the first fieldwork procedure for sex determination of animals in the wild, successfully applied to raptor species of three different subfamilies using the same specific LAMP primers. This molecular technique can be deployed directly in sampling areas because it only needs a voltage inverter to adapt a thermo-block to a car lighter and results can be obtained by the unaided eye based on colour change within the reaction tubes. Primers and reagents are prepared in advance to facilitate their storage at room temperature. We provide detailed guidelines how to implement this procedure, which is simpler (no electrophoresis required), cheaper and faster (results in c. 90 min) than PCR-based laboratory methods. Our successful cross-species application across three different raptor subfamilies posits our set of markers as a promising tool for molecular sexing of other raptor families and our field protocol extensible to all bird species.
Mapping and assembly of the Midas cichlid male-specific region supports molecular parallelism in the evolution of a master sex-determining role for amhr2
<p>The evolution of sex chromosomes and their differentiation from autosomes is a major event during genome evolution that happened many times in several lineages. The repeated evolution and lability of sex-determination mechanisms in fishes makes this a well-suited system to test for general and predictable patterns in evolution. According to current theory, differentiation is triggered by the suppression of recombination following the evolution of a new master-sex determining gene. However, the molecular mechanisms that establish recombination suppression are known from few examples, owing to the intrinsic difficulties of assembling sex determining regions (SDRs). Forward-genetics data and the development of long-read sequencing have generated a wealth of data questioning central aspects of the current theory. Here, we demonstrate that sex in Midas cichlids is determined by an XY system, identify and assemble the SDR by combining forward-genetics, long-read sequencing and optical mapping. We show how long-reads aid in the detection of artifacts in genotype-phenotype mapping that arise from incomplete genome assemblies. The male-specific region is restricted to a 100 kb segment on chromosome 4 that harbors transposable elements and a Y-specific duplicate of the anti-Mullerian receptor 2 locus, a known sex-determining gene. Our data suggests that <em>amhr2Y</em> originated by an interchromosomal translocation from chromosome 20 to 4 predating the split of Midas and Flier cichlids. In the later, it is pseudogenized and translocated to another chromosome. Duplication of anti-Mullerian genes is a common route to establishing new sex determiners, highlighting the role of molecular parallelism in the evolution of sex determination.</p>
Morphometric analysis of the foramen magnum in sex determination: An additional 3DCT study from Nepal on a larger sample
<p><strong>Background</strong>: Determination of sex of the skeletal remains plays a vital part in the identification of an individual. This study is focused on the morphometric measurement of the foramen magnum region and examining the accuracy of sexual dimorphism in the Nepalese population. </p> <p><strong>Methods</strong>: Measurements were obtained from 3D computed tomography (CT) scan of 261 Nepalese adult cranial bases with known age and sex. Length and breadth of the foramen magnum, length and breadth of right and left occipital condyles and maximum and minimum intercondylar distance were measured on the base of the skull CT images.</p> <p><strong>Results</strong>: <span>The mean values for all parameters were higher in males than females except for the maximum intercondylar distance.</span> Sex prediction done with discriminant function scores could classify the skull with an overall accuracy of 70.5%.</p> <p><strong>Conclusions</strong>: It can be concluded from the results that the morphometric study of the foramen magnum is not suitable for sex determination in the Nepalese population.</p>
Fig. 4 in Effectiveness of Morphological Sex Determination in the East Asian Barn Swallow (Hirundo rustica gutturalis) on Spring Migration
Fig. 4. Probability of being males by discriminant score in the East Asian Barn Swallows Hirundo rustica gutturalis.
Fig. 3 in Effectiveness of Morphological Sex Determination in the East Asian Barn Swallow (Hirundo rustica gutturalis) on Spring Migration
Fig. 3. Canonical discriminant scores of each sex calculated for the sex determination of the East Asian Barn Swallow Hirundo rustica gutturalis.
Fig. 2 in Effectiveness of Morphological Sex Determination in the East Asian Barn Swallow (Hirundo rustica gutturalis) on Spring Migration
Fig. 2. Distribution of the streamer length (T6-T5) and white tail patch length of the East Asian Barn Swallow Hirundo rustica gutturalis. Black circles denote females and white circles denote males. Posterior probability of being male, calculated from the discriminant function, is presented as a contour map; isopleths of probability are marked from 0.1 to 0.9.
Fig. 1 in Effectiveness of Morphological Sex Determination in the East Asian Barn Swallow (Hirundo rustica gutturalis) on Spring Migration
Fig. 1. Frequency distribution of (a) streamer lengths (T6-T5) and (b) white patch lengths selected by stepwise discriminant function analysis for the sex determination of the East Asian Barn Swallow Hirundo rustica gutturalis. Black columns denote females and white columns denote males; curved lines are the expected normal distributions of measurements reconstructed for each sex.
Data from: Tree, sex and size: ecological determinants of male versus female fecundity in three Fagus sylvatica stands
Inter-individual variation in fecundities has major consequences on population evolutionary potential, through genetic drift and selection. Using two spatially explicit mating models that analyze the genotypes of seeds and seedlings, we investigated the variation of male and female fecundities within and among three European beech (Fagus sylvatica) stands situated along an elevational gradient. Female and male individual fecundity distributions were both skewed in this monoecious species, and we found a higher variance in female as compared to male fecundities. Both female and male fecundities increased with tree size and decreased with density and competition in the neighborhood, the details of these effects suggesting sex-specific strategies to deal with the impact of limited resource on fecundity. The studied populations were functionally male-biased. Among-individual variations in functional gender were not driven by tree size but by density and competition in the neighborhood, consistently with the expectation of a decreasing femaleness under limited resource availability due to higher cost of female reproduction. Considering the variation of gene flow and genetic drift across elevation, our results suggest that the adaptive potential could be enhanced by low genetic drift at low elevation, and by high pollen-mediated gene flow at high elevation. Finally, this study predicts a more efficient response to selection for traits related to male versus female fitness, for a given selection intensity.
Data from: Population-level consequences of complementary sex determination in a solitary parasitoid
Background: Sex determination mechanisms are known to be evolutionarily labile but the factors driving transitions in sex determination mechanisms are poorly understood. All insects of the Hymenoptera are haplodiploid, with males normally developing from unfertilized haploid eggs. Under complementary sex determination (CSD), diploid males can be produced from fertilized eggs that are homozygous at the sex locus. Diploid males have near-zero fitness and thus represent a genetic load, which is especially severe under inbreeding. Here, we study mating structure and sex determination in the parasitoid Cotesia vestalis to investigate what may have driven the evolution of two complementary sex determination loci in this species. Results: We genotyped Cotesia vestalis females collected from eight fields in four townships in Western Taiwan. 98 SNP markers were developed by aligning Illumina sequence reads of pooled DNA of eight different females against a de novo assembled genome of C. vestalis. This proved to be an efficient method for this non-model species and provides a resource for future use in related species. We found significant genetic differentiation within the sampled population but variation could not be attributed to sampling locations by AMOVA. Non-random mating was detected, with 8.1% of matings between siblings. Diploid males, detected by flow cytometry, were produced at a rate of 1.4% among diploids. Conclusions: We think that the low rate of diploid male production is best explained by a CSD system with two independent sex loci, supporting laboratory findings on the same species. Fitness costs of diploid males in C. vestalis are high because diploid males can mate with females and produce infertile triploid offspring. This severe fitness cost of diploid males combined with non-random mating may have resulted in evolution from single locus CSD to CSD with two independent loci.
Data from: Within-population polymorphism of sex-determination systems in the common frog (Rana temporaria)
In sharp contrast with birds and mammals, the sex chromosomes of ectothermic vertebrates are often undifferentiated, for reasons that remain debated. A linkage map was recently published for Rana temporaria (Linnaeus, 1758) from Fennoscandia (Eastern European lineage), with a proposed sex-determining role for linkage group 2 (LG2). We analysed linkage patterns in lowland and highland populations from Switzerland (Western European lineage), with special focus on LG2. Sibship analyses showed large differences from the Fennoscandian map in terms of recombination rates and loci order, pointing to large-scale inversions or translocations. All linkage groups displayed extreme heterochiasmy (total map length was 12.2 cM in males, versus 869.8 cM in females). Sex determination was polymorphic within populations: a majority of families (with equal sex ratios) showed a strong correlation between offspring phenotypic sex and LG2 paternal haplotypes, whereas other families (some of which with female-biased sex ratios) did not show any correlation. The factors determining sex in the latter could not be identified. This coexistence of several sex-determination systems should induce frequent recombination of X and Y haplotypes, even in the absence of male recombination. Accordingly, we found no sex differences in allelic frequencies on LG2 markers among wild-caught male and female adults, except in one high-altitude population, where nonrecombinant Y haplotypes suggest sex to be entirely determined by LG2. Multifactorial sex determination certainly contributes to the lack of sex-chromosome differentiation in amphibians.
Are evolutionary transitions in sexual size dimorphism related to sex determination in reptiles? - Electronic supplementary material
<p class="western"><span><span><span><span>Sex determination systems are highly variable in vertebrates, although neither the causes nor the implications of this diversity are fully understood. Theory suggests that sex determination is expected to relate to sexual size dimorphism, because environmental sex determination promotes sex-specific developmental bias in embryonic growth rates. Furthermore, selection for larger size in one sex or the other has been proposed to drive the evolution of different genetic sex determination systems. Here we investigate whether sex determination systems relate to adult sexual size dimorphism, using 250 species of reptiles (Squamata, Testudines, Crocodylia) representing 26 families. Using phylogenetically informed analyses, we find that sexual size dimorphism is associated with sex determination: species with TSDIa sex determination (i.e. in which the proportion of female offspring increases with incubation temperature), have more female-biased size dimorphism than species with TSDII (i.e., species in which males are produced at mid temperatures). We also found a trend that species with TSD ancestors had more male-biased size dimorphism in XY sex-chromosome systems than in ZW sex-chromosome systems. Taken together, our results support the prediction that sexual size dimorphism is linked to sex-dependent developmental variations caused by environmental factors and also by sex chromosomes. Since the extent of size dimorphism is related to various behavioural, ecological and life-history differences between sexes, our results imply profound impacts of sex determination systems for vertebrate diversity.</span></span></span></span></p>
Comparative genome anatomy of the male and female silver arowanas provides an improved understanding of sex determination mechanisms in teleosts
<p><span>Silver arowana, <em>Osteoglossum</em> <em>bicirrhosum</em>, is sexually monomorphic, and its sex determination mechanism is poorly understood, which has been a major hurdle in its captive breeding. To this end, we assembled two high-quality chromosome-level genomes for each sex of silver arowana, with chromosome N50 of 10.6 Mb and 10.4 Mb in female and male individuals, respectively. Combing re-sequencing data of 109 individuals, we identified two sex-specific SNPs and confirmed a ZW model of sex-determination in this species. Both sex-specific SNPs are located in about 26Kb upstream of <em>foxl2</em> gene. Since <em>foxl2</em> has been confirmed to be differentially expressed in the gonads of silver arowana, it probably plays an important role in sex determination via the cross-regulation with auxiliary genes significantly correlated to it, such as <em>dmrt1</em>, <em>sox8a</em> and <em>cyp11a1</em>, etc. The sex chromosomes are homomorphic with a potentially recent origin, as linkage disequilibrium analysis showed minor recombination suppression. Overall, we developed accurate molecular markers for sex identification of silver arowana in each developmental stage, subsequently improving the reproductive efficiency and further promoting the industrial development.</span></p>
FIGURES 7–8 in A new possibility of sex determination in alleculine specimens (Coleoptera:Tenebrionidae: Alleculinae) of the Palaearctic and the Oriental genera
FIGURES 7–8. Claws of anterior tarsi. 7 Oracula (Oracula) bicolor Novák, 2019; 8 Pizura barbucha Novák, 2016; A = male, B = female.
Dataset and code for "Magnitude and determinants of excess total, age- and sex-specific all-cause mortality in 24 countries worldwide during 2020 and 2021: results on the impact of the COVID-19 pandemic from the C-MOR project"
<p>Data and statistical codes used for the results presented in the paper "Magnitude and determinants of excess total, age- and sex-specific all-cause mortality in 24 countries worldwide during 2020 and 2021: results on the impact of the COVID-19 pandemic from the C-MOR project"</p>
Sex Determination From Scapula Using 3-D Computed Tomography in Sample of Sohag Governorate Population
ClinicalTrials.gov study NCT04991610. IPD Sharing: YES. Countries: 1. Publications: 3.
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