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Results for “genetic drift”

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At least 19 recordsLinked to original sources
PubMed1979

Genetic drift in sex-linked lethal disorders.

A model is considered to calculate effects of genetic drift on the expected proportion of new mutants amongst males affected by a sex-linked recessive lethal. We show how to relate the number of cases of the disorder in males to the expected deviations from the deterministic value of the proportion of new mutants. For small values of alpha (= 3N mu), where N is the size of the female population, and mu is the mutation rate from wild-type to lethal allele, the standard deviation (SD) of the proportion of new mutants is large. However, if alpha more than 50, the potential effect of genetic drift is probably less important than the many other sources of error and bias.

Gene Frequency↗
PubMed1978

Social group fission and the origin of intergroup genetic differentiation among the rhesus monkeys of Cayo Santiago.

The serum transferrin locus is used to investigate the roles of the lineal effect of fission, male migration effect of fission, and genetic drift in causing intergroup genetic differentiation among the rhesus macaques of Cayo Santiago. These three mechanisms prove sufficient to explain the degrees of differentiation between the newly formed social groups A, K, and L as of July 1, 1971. The lineal effect of fission provides a baseline of intergroup differentiation which is altered by forces leading to intragroup genetic change, the male migration effect and genetic drift. The importance of population dynamics for the distribution of alleles among subgroups of a population is recognized.

Animals↗
PubMed2024

Repeated evolution on oceanic islands: comparative genomics reveals species-specific processes in birds.

Understanding the interplay between genetic drift, natural selection, gene flow, and demographic history in driving phenotypic and genomic differentiation of insular populations can help us gain insight into the speciation process. Comparing patterns across different insular taxa subjected to similar selective pressures upon colonizing oceanic islands provides the opportunity to study repeated evolution and identify shared patterns in their genomic landscapes of differentiation. We selected four species of passerine birds (Common Chaffinch Fringilla coelebs/canariensis, Red-billed Chough Pyrrhocorax pyrrhocorax, House Finch  Haemorhous mexicanus and Dark-eyed/island Junco Junco hyemalis/insularis) that have both mainland and insular populations. Changes in body size between island and mainland populations were consistent with the island rule. For each species, we sequenced whole genomes from mainland and insular individuals to infer their demographic history, characterize their genomic differentiation, and identify the factors shaping them. We estimated the relative (Fst) and absolute (dxy) differentiation, nucleotide diversity (π), Tajima's D, gene density and recombination rate. We also searched for selective sweeps and chromosomal inversions along the genome. All species shared a marked reduction in effective population size (Ne) upon island colonization. We found diverse patterns of differentiated genomic regions relative to the genome average in all four species, suggesting the role of selection in island-mainland differentiation, yet the lack of congruence in the location of these regions indicates that each species evolved differently in insular environments. Our results suggest that the genomic mechanisms involved in the divergence upon island colonization-such as chromosomal inversions, and historical factors like recurrent selection-differ in each species, despite the highly conserved structure of avian genomes and the similar selective factors involved. These differences are likely influenced by factors such as genetic drift, the polygenic nature of fitness traits and the action of case-specific selective pressures.

Animals↗
PubMed2026

Ancient DNA and Human Physiology.

Ancient DNA (aDNA) enables the reconstruction of chronologically sampled genomes from ancient humans, animals, plants, pathogens, and microorganisms, as well as environmental DNA, providing a record of biological changes through time. Improvements in short and degraded DNA extraction methods and low-cost sequencing now enable the generation of broad, cross-regional datasets that expand evolutionary analyses from past population demography to biological mechanisms. By tracking temporal shifts of allele frequencies, integrating functional genomics resources (e.g., gene expression, chromatin structure variation), modeling population demography to separate selection from genetic drift, and aligning genetic changes with archaeological, cultural, and climatic data, aDNA has the potential to link sequence variation to physiological function within their temporal and environmental contexts. In this review, we summarize illustrative case studies from aDNA research spanning complex traits, dietary adaptations, and responses to pathogens and other environmental changes, showing how human biology has evolved under multiple selective pressures through time. These dated signals help triage experimental work and expose mechanisms that are rare or absent in living cohorts. Although some challenges remain, such as geographic and temporal sampling disparities, limitations in data resolution and variant detection, and genotype-phenotype uncertainties, rapid methodological progress and stronger ethical frameworks are expanding what can be inferred, making aDNA a promising tool for refining physiological pathways, their timing, and their drivers.

Humans↗
PubMed2026

Genetic Diversity Analysis of Red Fox Populations (Vulpes vulpes L., 1758) in Natural and Anthropogenic Isolation.

This study presents a comparative analysis of the genetic structure and diversity of three red fox (Vulpes vulpes L.) populations representing different microevolutionary scenarios: panmixia (free-ranging Belarusian foxes), geographic isolation (free-ranging Scottish foxes), and anthropogenic selection (farm-bred foxes). Using a validated set of STR markers, multivariate statistical analysis was conducted to assess the genetic structure and the degree of genetic erosion across the studied groups. The wild red fox population in Belarus has been shown to maintain a state close to panmixia (PHWE = 0.090), characterized by a high effective population size (Ne = 694) and high allelic diversity. The island population from Scotland exhibits moderate gene pool depletion (Ne = 75.9) and a pronounced heterozygote deficiency (FIS = 0.18). Critical genetic erosion, which was characterized by a minimal effective population size (Ne = 60.2) and allelic fixation, was detected in the farm-bred group. The genetic distance between farm-bred and wild foxes (FST = 0.279; p = 0.001) reflects both the phylogeographic divergence between the Nearctic ancestors of farmed lineages and Palearctic wild populations, and the consequences of prolonged anthropogenic isolation, genetic drift, and selective breeding. These data indicate that artificial isolation and the impacts of genetic drift and targeted selection lead to a substantial depletion of the species' adaptive potential.

Animals↗
PubMed2025

Combined Evidence Reveals the Origin of a Rapid Range Expansion Despite Retained Genetic Diversity and a Weak Founder Effect.

Many species are currently experiencing range shifts in response to changing environmental conditions with potentially serious genetic consequences. Repeated founder events and strong genetic drift are expected to erode genetic variation at the range front, reducing adaptive potential and slowing or even halting the expansion. However, the severity of these consequences for common and highly mobile species undergoing environment-driven range shifts (c.f. invasions) is less clear. Here, we combined historical observations and contemporary movement data of the common reed warbler (Acrocephalus scirpaceus) with genomic evidence from across its European breeding range to (1) infer the origin and (2) quantify the genetic consequences of a recent and rapid northward range expansion. Although there were no reductions in levels of nucleotide diversity or allelic richness, nor a signal of founder effect in the directionality index (ψ), our combined dataset approach was able to infer an expansion origin from the southwest. Furthermore, we found that private allelic richness retained a slight but significant linear decline along the colonisation route. These results suggest that high dispersal capabilities can allow even philopatric species to avoid the loss of genetic diversity during rapid range expansions. Nevertheless, if multiple lines of evidence enable identification of an expansion pathway, we may still detect genetic signals of expansion.

Founder Effect↗
PubMed2014

Serial founder effects and genetic differentiation during worldwide range expansion of monarch butterflies.

Range expansions can result in founder effects, increasing genetic differentiation between expanding populations and reducing genetic diversity along the expansion front. However, few studies have addressed these effects in long-distance migratory species, for which high dispersal ability might counter the effects of genetic drift. Monarchs (Danaus plexippus) are best known for undertaking a long-distance annual migration in North America, but have also dispersed around the world to form populations that do not migrate or travel only short distances. Here, we used microsatellite markers to assess genetic differentiation among 18 monarch populations and to determine worldwide colonization routes. Our results indicate that North American monarch populations connected by land show limited differentiation, probably because of the monarch's ability to migrate long distances. Conversely, we found high genetic differentiation between populations separated by large bodies of water. Moreover, we show evidence for serial founder effects across the Pacific, suggesting stepwise dispersal from a North American origin. These findings demonstrate that genetic drift played a major role in shaping allele frequencies and created genetic differentiation among newly formed populations. Thus, range expansion can give rise to genetic differentiation and declines in genetic diversity, even in highly mobile species.

Animal Distribution↗
PubMed2026

The Multiple Roles of Genetics on Freshwater Macrophyte Functional Traits in the Interplay With the Environment: A Review.

The study of functional trait variation is increasingly used to understand macrophyte adaptation, as traits reflect organismal performance under different ecosystem conditions. Phenotypic expression results from the interplay of genetic and environmental factors: genetics provides the molecular basis for heritable traits and constrains potential phenotypes, while the environment acts as a selective and modulatory force. However, the genetic insight into traits has rarely been addressed in freshwater macrophyte studies. This review examines the different ways in which the DNA of macrophytes interplays with the environment and contributes to the variation in their functional traits, outlining main approaches, gaps, and future challenges. Only 21 studies explicitly combined genetics with functional traits and environment in the last fifteen years. The most common approach was the use of common garden experiments to explore acclimation and adaptation in a few model species. Current studies mainly focus on morphological and growth traits that best describe macrophytes' economic strategies, with limited attention to other trait categories, while the genetic and DNA traits studied are more variable. Across studies, environmental factors generally explained a larger proportion of functional trait variation, highlighting the dominant role of phenotypic plasticity for macrophyte acclimatation, whereas genetic contribution increased under experimentally manipulated conditions. Genome size and epigenetic variation influenced phenotypic plasticity; however, the effect was different and inconsistent on traits and depended on phylogenetic relationships and geographical environment variation. In field studies of natural populations, life history traits and hydrology had a strong effect on the geographic distribution of genetic diversity and the response to selection, as well as on our ability to distinguish selection from genetic drift. Future research should enhance molecular analyses, adopt multifactorial and long-term experimental designs, develop conceptual frameworks to address the relationships between genomics, environment and functional traits and integrate emerging tools to capture macrophyte adaptation better.

adaptation↗
PubMed2026

Genomic erosion in the assessment of species' extinction risk and recovery potential.

Many species are undergoing rapid population declines and environmental deterioration, leading to genomic erosion. Here we define genomic erosion as the loss of genetic diversity, accumulation of deleterious mutations, maladaptation, and introgression, all of which can undermine individual fitness and long-term population viability. Critically, this process continues even after demographic recovery due to a time-lagged impact of genetic drift, which is known as drift debt. Current conservation assessments, such as the International Union for Conservation of Nature Red List, focus on short-term extinction risk and do not capture the long-term consequences of genomic erosion. Likewise, the longer-term assessments of the International Union for Conservation of Nature Green Status may overestimate population recovery by failing to account for the enduring effects of genomic erosion. As genome sequencing becomes increasingly accessible, there is a growing opportunity to quantify genomic erosion and integrate it into conservation planning. Here, we use genomic simulations to illustrate how different genomic metrics are sensitive to the drift debt. We test how ancestral effective population size (Ne) and bottleneck history influence the tempo and severity of genomic erosion. Furthermore, we demonstrate how these dynamics shape genetic load and additive genetic variation, which are key indicators of long-term evolutionary potential. Finally, we present a proof-of-concept for a Genomic Green Status framework that aligns genomic metrics with conservation impact assessments, laying the foundation for genomics-informed strategies to support species recovery.

Extinction, Biological↗
PubMed2024

Rapid vertebrate speciation via isolation, bottlenecks, and drift.

Speciation is often driven by selective processes like those associated with viability, mate choice, or local adaptation, and "speciation genes" have been identified in many eukaryotic lineages. In contrast, neutral processes are rarely considered as the primary drivers of speciation, especially over short evolutionary timeframes. Here, we describe a rapid vertebrate speciation event driven primarily by genetic drift. The White Sands pupfish (Cyprinodon tularosa) is endemic to New Mexico's Tularosa Basin where the species is currently managed as two Evolutionarily significant units (ESUs) and is of international conservation concern (Endangered). Whole-genome resequencing data from each ESU showed remarkably high and uniform levels of differentiation across the entire genome (global FST ≈ 0.40). Despite inhabiting ecologically dissimilar springs and streams, our whole-genome analysis revealed no discrete islands of divergence indicative of strong selection, even when we focused on an array of candidate genes. Demographic modeling of the joint allele frequency spectrum indicates the two ESUs split only ~4 to 5 kya and that both ESUs have undergone major bottlenecks within the last 2.5 millennia. Our results indicate the genome-wide disparities between the two ESUs are not driven by divergent selection but by neutral drift due to small population sizes, geographic isolation, and repeated bottlenecks. While rapid speciation is often driven by natural or sexual selection, here we show that isolation and drift have led to speciation within a few thousand generations. We discuss these evolutionary insights in light of the conservation management challenges they pose.

Animals↗
PubMed1978

Population structure and genetic heterogeneity in the Upper Markham Valley of New Guinea.

An analysis is presented of the standardized Wahlund's variances (f) in gene frequencies of the ABO, Rh and MNS blood group systems among 19 villages of the Atsera isolate of the upper Markham Valley, Papua New Guinea. In the past, there has been some disagreement over the relative importance of population structure and natural selection in the determination of these variances. The Lewontin-Krakauer test is presented as a means of resolving this disagreement. According to this test, selectively neutral variation in gene frequencies should generate essentially homogeneous values of f for all loci, a homogeneity which can be tested by comparing the value of (formula: see text) to a theoretical (formula: see text) expected when variations in (formula: see text) are due solely to sampling error. The observed value of (formula: see text) for the Atsera isolate is 2.9 x 10(-5), which is not significantly different from the expected values that range from 1.23 x 10(-5) to 2.46 x 10(-5) depending on the constant used in calculating (formula: see text). Therefore it appears that nonselective aspects of population structure such as genetic drift and intervillage migration are responsible for the recorded genetic variation in this isolate.

ABO Blood-Group System↗
PubMed1976

Genetic and anthropological studies in the human adaptability section of the International Biological Programme.

In the U.K. contribution to the H.A. (Human Adaptibility) section of I.B.P., genetic and anthropological studies have focused on three concerns. First, attempts have been made in a number of investigation to gain additional descriptive information about the genetic compostition of the world's populations. Concentrating on blood groups, blood enzymes, serum proteins and other polmorphic markers important gaps have been filled in our knowledge of the geographical paterns of human variation and of the affinities of populations wig and characterizing populations which were being studied for other purposes. For example, it was of critical concern in interpreting results to know in the investigations of climatic physiology and nutrition in Ethiopia and Israel whether the various groups studied in different environments were genetically the same or not. Finally, attention was focused in a number of investigations, especially those in New Guinea, Tristan da Cunha, Tanzania, and the Orkneys, on the factors which determine the genetic structure of populations. In these the effects of such phenomena as inbreeding, genetic drift, founder effects, migration and gene flow and the relation between genetic variety and health were examined and much attention was given to the interaction between demographic forces and genetics.

Adaptation, Physiological↗
PubMed1979

Highland and lowland populations of Lesotho.

It has not been possible to demonstrate significant sero-genetic differences between lowland and highland Sotho populations; the differences which do exist may well be attributable to random genetic drift. The study shows that the Sotho have received an appreciable genetic contribution from the San they have absorbed but their sero-genetic profile remains eminently Negro. A low frequency of the PTC non-taster allele was found (t = 0.142 +/- 0.029) as was the overall frequency for colour blindness (cb = 0.013 +/- 0.009).

Alleles↗
PubMed1978

Applied and theoretical significance of electrohoretic studies in mosquitoes (Diptera: Culicidae).

The more relevant results obtained in the past decade with the use of electrophoretic techniques in studying mosquitoes are reviewed and discussed. These results mainly concern the evaluation of genetic variability of natural and laboratory populations; the study of the role of natural selection and genetic drift in the maintenance and evolution of enzyme polymorphisms; the estimate of genetic differentiation between populations, subspecies and species; the identification of sibling species and of their possible hybrids; the field study of precopulatory isolating mechanisms by the release of electrophoretically recognizable population samples; the elaboration of genetic maps; the study of the phenomenon of multiple insemination; and the evaluation of sexual competitiveness, particularly in connection with the planning of genetic control measures. The importance of this approach in the study of mosquito biology from the applied and theoretical points of view is stressed.

Aedes↗
PubMed1977

Evolutionary drift of the argF and argl genes. Coding for isoenzyme forms of ornithine transcarbamylase in E. coli K12.

Considerable genetic drift has occurred during the evolution of the two genes, argF and argl, which individually code for isoenzyme forms of ornithine transcarbamylase in E. coli K12. The use of the experimental protocol described in this work established that between 25-40% of the base pairs in the genes argF and argl have changed since they diverged from a hypothetical ancestral gene. The extent of divergence of the genes was determined by mRNA-DNA hybridization utilizing arginine transducing DNA as a hybridization probe and mRNA prepared in vivo from appropriate bacterial strains and with mRNA synthesized in vitro using template DNA isolated from the specialized transducing phages gammacI857dargl and phi80dargF.

Coliphages↗
PubMed1979

[Incidence of cystic fibrosis in Brittany (author's transl)].

Incidence of cystic fibrosis has been estimated in three adjacent geographic areas of Brittany: North Finistere, South Finistere and Morbihan. This incidence is respectively 6.0 x 10(-4), 4.8 x 10(-4), 2.9 x 10(-4) in these three areas. A significant difference between North Finistere and Morbihan was found. Without proofs in favor of natural selection, genetic drift seems to be a possible explanation of this variation. Moreover, as in other studies, a genetic heterogeneity of the disease was not shown.

Cystic Fibrosis↗