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At least 19 recordsLinked to original sources

PubMed2026

Discovering common and population-specific QTLs for leaf rust resistance in different Barley populations.

Multi-population GWAS lead to identification of common and population-specific QTLs for leaf rust resistance in barley. Genome-wide association studies (GWAS) are a powerful tool for detecting genetic markers associated with traits of interest. However, these studies are typically restricted to a single population, and transferability of identified marker effects across populations is challenged by population differences in linkage, allele frequencies, epistatic effects, and environmental context. When comparing GWAS results between populations, a lack of overlapping signals is often interpreted as a lack of common quantitative trait loci (QTLs), although such discrepancies may result from differences in statistical power to detect signals. In barley (Hordeum vulgare L.), where genetic leaf rust resistance is rapidly overcome by evolving pathogens, identification of cross-population robust and potentially transferable resistance loci is a key task. Here, we present a mixed model approach for multi-population GWAS that estimates correlated marker effects in multiple populations and use this to test for significant effects across and within populations. Applying this model to four barley breeding populations revealed both common and population-specific QTL effects for leaf rust resistance, including loci colocalizing with known Rph genes and novel regions with plausible candidate genes. Multi-population GWAS increased power, revealing signals not detected by GWAS within populations. We categorized the reported QTLs into three groups based on marker-associated allele effects: (1) consistent effect direction across populations, (2) differing effect direction across populations, and (3) present in a single population. The study highlights the transferability and limitations of leaf rust resistance QTLs across different barley populations and provides a general statistical framework to support robust marker-assisted selection across populations.

Quantitative Trait Loci↗

PubMed2025

Parallel genetic adaptation amid a background of changing effective population sizes in divergent yellow perch (Perca flavescens) populations.

Aquatic ecosystems are highly dynamic environments vulnerable to natural and anthropogenic disturbances. High-economic-value fisheries are one of many ecosystem services affected by these disturbances, and it is critical to accurately characterize the genetic diversity and effective population sizes of valuable fish stocks through time. We used genome-wide data to reconstruct the demographic histories of economically important yellow perch (Perca flavescens) populations. In two isolated and genetically divergent populations, we provide independent evidence for simultaneous increases in effective population sizes over both historic and contemporary time scales including negative genome-wide estimates of Tajima's D, 3.1 times more single nucleotide polymorphisms than adjacent populations, and contemporary effective population sizes that have increased 10- and 47-fold from their minimum, respectively. The excess of segregating sites and negative Tajima's D values probably arose from mutations accompanying historic population expansions with insufficient time for purifying selection, whereas linkage disequilibrium-based estimates of Ne also suggest contemporary increases that may have been driven by reduced fishing pressure or environmental remediation. We also identified parallel, genetic adaptation to reduced visual clarity in the same two habitats. These results suggest that the synchrony of key ecological and evolutionary processes can drive parallel demographic and evolutionary trajectories across independent populations.

Animals↗

PubMed1977

Patterns of death among suicide attempters, a psychiatric population and a general population.

This epidemeological study examines patterns of mortality for a population of suicide attempters, a psychiatric population without suicide attempts, and a general population without psychiatric histories in order to clarify earlier reports of differential risks of death associated with these groups. Mortality patterns were investigated over an 11-year period in terms of demographic characteristics and rates of death by various causes. Suicidal deaths were given special attention to identify variables that may have predictive validity for suicide. The results indicate that the suicide attempter group represents a distinctive demographic and mortality entity from either the psychiatric or general populations, and accounts for much of the increased risk of death previously attributed to the psychiatric population. Further, premature deaths due to suicide are strongly associated with the suicide attempter group. The psychiatric and general populations differ in relatively insignificant ways. These results suggest that a profitable approach to the prevention of suicide would be to focus on individuals who were at high risk within the suicide attempter population. Longer-term follow-up of these individuals is necessary if deaths due to suicide are to be prevented. Difficulties associated with implementation of preventive follow-up programs are also discussed.

Accidents↗

PubMed2026

Idiopathic pulmonary fibrosis risk loci in East Asian populations mirror those of European populations.

RATIONALE: Common and rare variants that are associated with the risk of developing idiopathic pulmonary fibrosis (IPF) have been identified predominantly in European ancestry populations. OBJECTIVES: To better understand the genetic variants that contribute to IPF in individuals with Asian ancestry, we conducted a genome-wide association study of IPF in East Asian populations. METHODS: We included 1026 patients with IPF and compared them to 1723 unaffected controls of Japanese and Korean ancestry. Genome-wide association analysis was conducted in the Japanese and Korean ancestry cohorts separately and combined using meta-analysis. Restricted maximum likelihood was used to estimate the SNP-based heritability and local ancestry of chromosome 11 was inferred for each subject. MEASUREMENTS AND MAIN RESULTS: We identified loci on chromosomes 4 (FAM13A; rs7690839), 5 (TERT; rs7734992), 6 (DSP; rs2076295), and 11 (MUC5B; rs35705950) that were significantly associated with risk of IPF. Importantly, the sentinel variants in each of these loci are the same as, or in strong linkage disequilibrium with, the risk variants that have been observed in studies of European ancestry populations. In aggregate, common variants (not including the MUC5B promoter variant) account for approximately 25% of the risk of developing IPF in these East Asian ancestry cohorts. Moreover, local ancestry analysis indicates that the presence of MUC5B promoter variant in the East Asian population is not a result of admixture with European ancestry populations. CONCLUSIONS: We conclude that the IPF risk loci in East Asian populations are shared with those of European ancestry populations, although their risk allele frequencies and effect sizes differ. These findings indicate shared genetic risk factors of IPF across ancestries.

Aged↗

PubMed2026

Differences in structural color and population genetic structure of Western and Central Palearctic Polyommatus icarus populations.

The blue structural coloration of male Polyommatus icarus butterflies functions as a sexual signaling trait and exhibits remarkable spectral stability within populations despite being generated by highly complex photonic nanoarchitectures. The correlation of the blue sexual signaling color and population genetic variation of the butterflies was investigated across the Western and Central Palearctic regions. Dorsal wing reflectance spectra was measured for 95 male specimens and compared with the population genetic structure revealed in 99 specimens by 18 recently developed microsatellites. Reflectance measurements indicated a clear separation between the European and Central Asian populations, consistent with our previous findings, while the intermediate populations near the Ural Mountains exhibited distinct European spectral characteristics. In contrast, genetic variation showed limited structuring and correlated primarily with geographic distance, as indicated by a significant isolation-by-distance pattern. Thus, although both reflectance and genetic variations are geographically structured, spectral properties are only weakly correlated with genetic differentiation. Populations near the Ural Mountains exhibited genetic ancestry linked to Central Palearctic groups, while displaying distinct Western Palearctic coloration, suggesting that the focal species' sexual signaling is strongly influenced by local factors. These findings suggest that sexual signaling coloration may evolve at least partially independently of the neutral genetic background, offering additional insight into evolutionary divergence across broad geographic scales.

Animals↗

PubMed2025

Pervasive fitness trade-offs revealed by rapid adaptation to shifting population densities in large experimental populations of Drosophila melanogaster.

Trade-offs are an inherent feature of organismal biology that are expected play a fundamental role in the evolution of natural populations. Efforts to quantify trade-offs are largely confined to phenotypic measurements and the identification of negative genetic-correlations among fitness-relevant traits. Here, we use time-series genomic data collected during experimental evolution in large, genetically diverse populations of Drosophila melanogaster to directly measure the manifestation of trade-offs in response to fluctuating selection on ecological timescales. Specifically, we first conducted a lab-based selection experiment to quantify a genome-wide signal of antagonistic pleiotropy elicited in response to shifting population densities and associated with reproduction and stress tolerance selection. In doing so, we identified a putative role of two cosmopolitan inversions in these trade-offs. We then conducted an independent experiment to show that a simple manipulation of increasing population density under controlled lab-based conditions identified loci that are relevant to selection during population expansion and collapse in a complex, semi-natural setting. In concert, our results reveal how adaptation in complex, natural environments can be coarse-grained in such a manner to drive repeatable and predictable patterns of genomic variation, and further add credence to models positing a role of generic fitness trade-offs in the maintenance of variation in natural populations.

Drosophila melanogaster↗

PubMed1977

Experimental population genetics of meiotic drive systems. I. Pseudo-Y chromosomal drive as a means of eliminating cage populations of Drosophila melanogaster.

The experimental population genetics of Y-chromosome drive in Drosophila melanogaster is approximated by studying the behavior of T(Y;2),SD lines. These exhibit "pseudo-Y" drive through the effective coupling of the Y chromosome to the second chromosome meiotic drive locus, Segregation distorter (SD). T(Y;2),SD males consequently produce only male offspring. When such lines are allowed to compete against structurally normal SD(+) flies in population cages, T(Y;2),SD males increase in frequency according to the dynamics of a simple haploid selection model until the cage population is eliminated as a result of a deficiency in the number of adult females. Cage population extinction generally occurs within about seven generations.-Several conclusions can be drawn from these competition cage studies:(1) Fitness estimates for the T(Y;2),SD lines (relative to SD(+ )) are generally in the range of 2-4, and these values are corroborated by independent estimates derived from studies of migration-selection equilibrium. (2) Fitness estimates are unaffected by cage replication, sample time, or the starting frequency of T(Y;2),SD males, indicating that data from diverse cages can be legitimately pooled to give an overall fitness estimate. (3) Partitioning of the T(Y;2),SD fitnesses into components of viability, fertility, and frequency of alternate segregation (Y + SD from X + SD(+)) suggests that most of the T(Y;2),SD advantage derives from the latter two components. Improvements in the system might involve increasing both the viability and the alternate segregation to increase the total fitness. While pseudo-Y drive operates quite effectively against laboratory stocks, it is less successful in eliminating wild-type populations which are already segregating for suppressors of SD action. This observation suggests that further studies into the origin and rate of accumulation of suppressors of meiotic drive are needed before an overall assessment can be made of the potential of Y-chromosome drive as a tool for population control.

Animals↗

PubMed1975

Population cytology of the genus Phaulacridium. IV. Phaulacridium marginale (Walker)--the North Island populations.

Samples of Phaulacridium marginale were taken from the North Island of New Zealand, together with further samples from three South Island populations. Seven of the North Island populations were found to be polymorphic for a small telocentric B chromosome. In only one case was the B chromosome significantly associated with an increase chiasma frequency. All three South Island populations contained B chromosomes. Seven of the nine N.I. populations were also polymorphic for extra segments on the centric end of the S11 chromosome. In six of them this polymorphism co-existed with that for B'S. A new polymorphism was encountered in two populations. This was for a large block of heterochromatic material located at the centric end of one of the smaller medium-sized chromosomes which thus becomes acro- rather than telocentric. Tt would appear that the New Zealand grasshopper, Ph. marginale, is able to tolerate many different polymorphisms for extra heterochromatin. However, this ability is perhaps restricted to central populations. In this context, the high level of occurence of these polymorphisms in the North Island could be due to the better climatological conditions existing there compared to most of the South Island.

Aneuploidy↗

PubMed2024

Population structure and connectivity among coastal and freshwater Kelp Gull (Larus dominicanus) populations from Patagonia.

The genetic identification of evolutionary significant units and information on their connectivity can be used to design effective management and conservation plans for species of concern. Despite having high dispersal capacity, several seabird species show population structure due to both abiotic and biotic barriers to gene flow. The Kelp Gull is the most abundant species of gull in the southern hemisphere. In Argentina it reproduces in both marine and freshwater environments, with more than 100,000 breeding pairs following a metapopulation dynamic across 140 colonies in the Atlantic coast of Patagonia. However, little is known about the demography and connectivity of inland populations. We aim to provide information on the connectivity of the largest freshwater colonies (those from Nahuel Huapi Lake) with the closest Pacific and Atlantic populations to evaluate if these freshwater colonies are receiving immigrants from the larger coastal populations. We sampled three geographic regions (Nahuel Huapi Lake and the Atlantic and Pacific coasts) and employed a reduced-representation genomic approach to genotype individuals for single-nucleotide polymorphisms (SNPs). Using clustering and phylogenetic analyses we found three genetic groups, each corresponding to one of our sampled regions. Individuals from marine environments are more closely related to each other than to those from Nahuel Huapi Lake, indicating that the latter population constitutes the first freshwater Kelp Gull colony to be identified as an evolutionary significant unit in Patagonia.

Humans↗

PubMed1976

Training public school teachers in population dynamics: An evaluation of the urban life-population education workshops in Baltimore.

Nine population education workshops were held for city school teachers in Baltimore, Maryland during the 1972-73 academic year. The original program schedule was modified two times, at the end of the third workshop and the sixth. Each change resulted in fewer formal presentations, more teacher discussions and greater teacher involvement in the workshop program. From the ideas generated by the workshops, curriculum units suitable for elementary and secondary school students were produced. An evaluation of the program showed that teachers' knowledge of selected demographic concepts and facts increased between the pre-workshop period and the post-workshop period. The changes were greater in the later workshops. The changes in knowledge were statistically significant. While there was some regression to pre-test levels, the teachers retained a substantiol portion of the knowledge they received when measured a second time after the workshop. High school teachers showed greater effective changes in knowledge than lower grade teachers. However, interest in population education appears to be wide-spread among all teachers including lower grade teachers. It is suggested that in the future, programs in population education consider conducting separate workshops for teachers of the same or similar grade level.

Curriculum↗

PubMed1975

Population structure, gene flow and natural selection in populations of Euphydryas phaeton.

An examination of seven proteins, presumably encoded by seven structural gene loci, in three local populations of the supposedly sedentary and colonial butterfly, Euphydryas phaeton revealed that three (43 per cent) were polymorphic with three to five alleles each. In addition to this high level of heterozygosity, no statistically significant differences in allele frequencies were found at two of the three polymorphic loci. Since the effective breeding size in each population was estimated to range from as few as 20 to 200 individuals, it appears that some level of gene flow between populations must be invoked to explain the high levels of genetic variability maintained in local populations of this butterfly, despite its apparently colonial nature.

Alleles↗

PubMed1979

The use of restriction endonucleases to measure mitochondrial DNA sequence relatedness in natural populations. I. Population structure and evolution in the genus Peromyscus.

In this study we introduce to natural population analysis a molecular technique that involves the use of restriction endonucleases to compare mitochondrial DNA (mtDNA) sequences. We have examined the fragment patterns produced by six restriction endonucleases acting upon mtDNA isolated from 23 samples of three species of the rodent Peromyscus. Our observations confirm the following conclusions derived from previous experiments with laboratory animals: (1) mtDNA within an individual homogeneous; (2) at least the majority of mtDNA present in an individual is inherited from the female parent. Our experiments demonstrate for the first time that there is detectable heterogeneity in mtDNA sequences within and among natural geographic populations of a species and that this heterogeneity can readily be used to estimate relatedness between individuals and populations. Individuals collected within a single locale show less than 0.5% sequence divergence, while those collected from conspecific populations separated by 50 ti 500 miles differ by approximately 1.5%. The mtDNAs of the closely related sibling species P. polionotus and P. maniculatus differ from each other by 13 to 17%; nonsibling species differ by more than 20%. Qualitative and quantitative approaches to analysis of digestion patterns are suggested. The results indicate that restriction analysis of mtNDA may become the most sensitive and powerful technique yet available for reconstructing evolutionary relationships among conspecific organisms.

Animals↗

PubMed2026

Recovering the precolonial population structure of Khoe-San descendant populations.

San populations from Botswana and Namibia retain exceptional linguistic, cultural, and genetic diversity, but few Khoisan-speaking groups remain south of the Kalahari Desert. However, historically, far southern Africa was home to many San and Khoekhoe groups. Popular opinion often implies that such populations do not contribute to the ancestry of contemporary South Africans. Here, we characterize the genetic ancestry of self-identified South African Coloured groups and reconstruct precolonial and colonial population structures from 620 newly sampled individuals. These groups retain the majority of Khoe-San genetic ancestry (>48%), suggesting the persistence of Khoe-San ancestry to the present day. By isolating the Khoe-San ancestry component, we show that it is intermediate between the ≠Khomani San and Nama and distinct from Kalahari Khoe-San populations. We also find that signatures of the Indian Ocean slave trade can be traced to Indonesian islands such as Sulawesi, Java, and Flores, while the South Asian ancestry is regionally nonspecific.

Humans↗

PubMed1977

[Medico-genetic study of the population of the Samarkand region. II. Population-genetic description of 4 kishlaks of the Urgut district].

This report is a second one in a series of works devoted to the medico-genetical screening of Uzbekistan populations. The paper comprises the results of the analysis of the populational structure of one of the village councils (soviets) of the Urgut District of the Samarkand Region. The main parameters of the population studied were as follows: total number 1529 persons, the average number of inhabitants of one village--328. The proportion of the inhabitants studied--56%, the average number of persons per family--5.22; the average period between subsequent generations--30-35 years, the gametic index--0.8, the inbreeding coefficient inferred from pedigrees--0.018899--0.00781, Fst = 0.03577, the average genetic distanse according to Edwards--0.0231-0.0671. The distribution of Mendelian markers (ABO, Rh, Hp and Ptc) was studied. The observed ratio between a high degree of inbreeding and a relatively low extent of isolation of populations permits to explain satisfactorily the distribution and frequencies of hereditary pathology in the Urgut District of the Samarkand Region pointed out in the previous report.

Adolescent↗

PubMed1978

An estimate of a rare population group: the U.S. Jewish population.

High, middle, and low estimates for a rare population group, the Jewish population of the United States, are presented together with their root mean square errors. These estimates are based upon a national sample whose essential survey design features are outlined. The features indicate that difficult-to-find populations can be sampled in adequate numbers if some sort of a list can be developed with a fair proportion of the population. To this list must be added an integrated area sample.

Housing↗

PubMed1977

[Population surveillance and its importance in the study of the effectiveness of primary and secondary prevention of ischemic heart disease among the population].

The results of epidermiologic surveys conducted in the USSR and in other countries are briefly analysed. It is noted that study of the effectiveness of the elaborated measures for primary and secondary prevention of ischemic heart disease is the principal object of long-term surveys among the population. The author believes the term population surveys to be most justified. The general principles of the organization of population surveys are described. Approaches to the evaluation of the effectiveness of intervention among the population are briefly characterized.

Adult↗

PubMed1979

The genetics of Drosophila subobscura populations. IX. Studies on linkage disequilibrium in four natural populations.

Gametic frequencies were obtained in four natural populations of D. sub-obscura by extracting wild chromosomes and subsequently analyzing them for inversions and allozymes. The genes Lap and Pept-1, both located within the same inversions of chromosome O, were found in striking nonrandom associations with them of the same kind and degree in all populations studied. On the contrary, the gene Acph, also located within the previously mentioned inversions, was found in linkage disequilibrium with them only in two populations and of opposite directions. This is also the case for the genes Est-9 and Hk, both located within chromosome E inversions. While the gene Est-9 was in strong linkage disequilibrium with the inversions, of the same kind and degree in all populations studied, Hk was found to be in linkage equilibrium. Allele frequencies for the 29 genes studied do not show geographical variation except for the genes Lap, Pept-1 and Est-9, the ones found in linkage disequilibria with the geographically varying gene arrangements. Although mechanical or historical explanations for these equilibria cannot be ruled out, these data cannot be explained satisfactorily by the "middle gene explanation," which states that loci displaying such linkage disequilibria are the ones located near the break points of inversions, while the ones displaying linkage equilibria with them are located in the middle of them. There is no evidence for consistent linkage disequilibria between pairs of loci, except for the closely linked genes of the complex locus, Est-9. This would imply, if it is not a peculiarity of the Est-9 complex, that the linkage disequilibria are found only between very closely linked loci or that, for less closely linked genes, the associations are too weak to be detected by the usual samples sizes.

Alleles↗

PubMed1979

Mutation rates, population sizes and amounts of electrophoretic variation of enzyme loci in natural populations.

A method is presented for estimating relative mutation rates or relative effective population sizes, under the hypothesis of adaptively neutral allelic variation. This method was applied to seven surveys of electrophoretic variation. It was observed that electrophoretic mutation rates so obtained follow the gamma distribution and, in Drosophila, are positively correlated with the molecular weights of the enzymes subunits. The variance in mutation rate is larger under the step-wise model of electrophoretic mutation than under the infinite-alleles model. Rates for the most variable loci may exceed rates for less variable loci by a factor of 500. For completely invariant loci, this factor may be as high as 4 X 10(4), an observation suggesting that these loci are subject to purifying selection. In contrast to mutation rates, effective population sizes may vary at the most by a factor of ten. These results support the hypothesis that differences in the amount of electrophoretic variability among polymorphic loci may reflect differences in the rate by which electrophoretically detectable variation is generated in population.

Animals↗