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At least 343 records · Page 19Linked to original sources
PubMed1990

Quantitative genetics of maximal oxygen consumption in a garter snake.

Broad-sense heritabilities and genetic correlations of maximal oxygen consumption (VO2max), blood hemoglobin levels, and ventricle mass were estimated in a natural population of snakes. Traits were measured for six or fewer presumed full-sibling offspring from each of 45 wild-caught gravid garter snakes (Thamnophis sirtalis). VO2max was highly reproducible between replicate trial days (r = 0.88). In an attempt to reduce maternal effects, correlations of each character with body mass, snout-vent length, age at testing, litter size, dam mass, and dam snout-vent length were removed by computing residuals from multiple-regression equations. These residuals were used in subsequent genetic analyses. Approximate coefficients of variation of residuals were 16% for VO2max, 19% for hemoglobin level, and 13% for ventricle mass. Broad-sense heritabilities were highly significant for all characters [P less than 0.0001; VO2max heritability (h2) = 0.88; hemoglobin level h2 = 0.63; ventricle mass h2 = 0.41], suggesting that they could respond genetically to selection. Phenotypic correlations (rP) among residual characters were significant only between VO2max and ventricle mass (rP = +0.27). VO2max and ventricle mass exhibited a significant (broad-sense) genetic correlation of +0.64; this might facilitate the correlated evolution of these two traits in response to natural or artificial selection. Ventricle mass and hemoglobin level showed a significant environmental correlation of +0.43. Treadmill endurance crawling time (Evolution 42: 335-350, 1988) showed a weak but significantly positive rP with VO2max (rP = +0.17).

Aging↗
PubMed1995

In vitro selection of RNA lectins: using combinatorial chemistry to interpret ribozyme evolution.

BACKGROUND: It has been hypothesized that the fact that both ribosomal RNA and the group I intron can bind to aminoglycoside antibiotics implies that these RNAs are evolutionarily related. This hypothesis requires the assumption that there are relatively few ways for RNA molecules to form aminoglycoside-binding sites. RESULTS: We have used in vitro selection to determine the diversity of aminoglycoside-binding sites that can be formed by RNA molecules. We have generated RNA 'lectins' that can bind aminoglycosides tightly and specifically. Sequence analysis indicates that there are many different ways to form tight and specific aminoglycoside binding sites. These artificially selected binding sites are functionally similar to those that have arisen from natural selection. CONCLUSIONS: Our results suggest that the presence of aminoglycoside-binding sites on RNA molecules may not be a useful trait for determining evolutionary relatedness. Instead, the fact that RNA molecules can bind these 'low molecular-weight effectors' may indicate that natural products such as aminoglycosides have evolved to exploit sequence- and structure-specific recognition of nucleic acids, in much the same way that lexitropsins have been designed by chemists to recognise specific nucleic acid sequences.

Aminoglycosides↗
PubMed2003

Realized heritability of personalities in the great tit (Parus major).

Behaviour under conditions of mild stress shows consistent patterns in all vertebrates: exploratory behaviour, boldness, aggressiveness covary in the same way. The existence of highly consistent individual variation in these behavioural strategies, also referred to as personalities or coping styles, allows us to measure the behaviour under standardized conditions on birds bred in captivity, link the standardized measurements to the behaviour under natural conditions and measure natural selection in the field. We have bred the great tit (Parus major), a classical model species for the study of behaviour under natural conditions, in captivity. Here, we report a realized heritability of 54 +/- 5% for early exploratory behaviour, based on four generations of bi-directional artificial selection. In addition to this, we measured hand-reared juveniles and their wild-caught parents in the laboratory. The heritability found in the mid-offspring-mid-parent regression was significantly different from zero. We have thus established the presence of considerable amounts of genetic variation for personality types in a wild bird.

Aggression↗
PubMed2005

Functional trade-offs in the limb bones of dogs selected for running versus fighting.

The physical demands of rapid and economical running differ from the demands of fighting in ways that may prevent the simultaneous evolution of optimal performance in these two behaviors. Here, we test an hypothesis of functional trade-off in limb bones by measuring mechanical properties of limb bones in two breeds of domestic dog (Canis lupus familiaris L.) that have undergone intense artificial selection for running (greyhound) and fighting (pit bull) performance. The bones were loaded to fracture in three-point static bending. To correct for the effect of shear, we estimated the shear stress in the cross section and added energy due to shear stress to the tensile energy. The proximal limb bones of the pit bulls differed from those of the greyhounds in having relatively larger second moments of area of mid-diaphyseal cross sections and in having more circular cross-sectional shape. The pit bulls exhibited lower stresses at yield, had lower elastic moduli and failed at much higher levels of work. The stiffness of the tissue of the humerus, radius, femur and tibia was 1.5-2.4-fold greater in the greyhounds than in the pit bulls. These bones from the pit bulls absorbed 1.9-2.6-fold more energy before failure than did those of the greyhounds. These differences between breeds were not observed in the long bones of the feet, metacarpals and metatarsals. Nevertheless, the results of this analysis suggest that selection for high-speed running is associated with the evolution of relatively stiff, brittle limb bones, whereas selection for fighting performance leads to the evolution of limb bones with relatively high resistance to failure.

Adaptation, Biological↗
PubMed2003

A physico-chemical approach of polyanion-polycation interactions aimed at better understanding the in vivo behaviour of polyelectrolyte-based drug delivery and gene transfection.

Polyanions and polycations are known to interact electrostatically and form soluble or insoluble polyelectrolyte complexes. Body fluids, blood and cells are composed of many polyelectrolytic systems such as proteins, glycoproteins, poly(glycosamino glycane)s, polynucleotides, etc. under physiological conditions. Nowadays synthetic polyelectrolytes are proposed as carriers of bioactive compounds, such as drugs and genes, and are thus to be injected into body fluids. For the sake of better understanding the complex behaviour of such artificial polyelectrolytic systems in the pool of natural polyelectrolytes forming living systems, interactions of bi- and multi-components mixtures of synthetic polyanions with the same synthetic polycation, namely poly[(dimethylaminoethyl) methacrylate], HCl, were investigated under the conditions imposed by physiological media, namely pH = 7.4, ionic strength mu = 0.15 and T = 37 degrees C. The selected artificial polyanions were the sodium salts of poly(acrylic acid), poly(methacrylic acid), poly(L-lysine citramide) and poly(styrene sulfonic acid) which have different acid strength, charge density and ionogenic group. The influence of ionic strength and pH on complex formation and stability was investigated by turbidimetry at lambda = 520 nm. Phase separation occurred regardless of ionic strength in the case of sodium polystyrene sulfonate. For the other polyanions, redissolution was observed at critical NaCl concentrations much higher than the physiological ionic strength. In the case of mixtures of two or three polyanions with the polycation, the complex formation appeared polyanion-selective at physiological ionic strength. Data are discussed with regard to phenomena that can occur in vivo.

Acrylic Resins↗
PubMed2006

Responses to selection on phenoloxidase activity in yellow dung flies.

Maintaining an immune system is costly. Resource allocation to immunity should therefore trade off against other fitness components. Numerous studies have found phenotypic trade-offs after immune challenge, but few have investigated genetic correlations between immune components and other traits. Furthermore, empirical evidence for the costs of maintaining an innate immune system in the absence of challenges is rare. We examined responses to artificial selection on phenoloxidase (PO) activity, an important part of the insect innate defense against multicellular pathogens, in yellow dung flies, Scathophaga stercoraria (L.). After 15 generations of successful selection on PO activity, we measured reproductive characters: clutch size, egg hatching rates, adult emergence rates, and adult longevity. We found no evidence for negative genetic correlations between PO activity and reproduction. In fact, flies of lines selected for increased PO activity had larger first clutches, and flies of lines selected for decreased PO activity had smaller ones. However, flies from high-PO lines died earlier than did low-PO flies when no food was available; that is, there is a survival cost of running at high PO levels in the absence of challenge. Variation in resource acquisition or use may lead to positive genetic correlations between PO and fertility and fecundity. The negative correlation between PO and longevity under starvation may indicate that variation for resource acquisition is maintained by a cost of acquisition, based on a genotype-environment interaction.

Animals↗
PubMed2002

Daily temporal organization of laying in Japanese quail: variability and heritability.

In birds, many behavioral and physiological processes that occur during reproduction show daily rhythms in response to environmental temporal constraints. In this study, the individual daily organization of laying and its genetic determinant in Japanese quail (Coturnix coturnix japonica) were analyzed. For this purpose, the oviposition time of 102 randomly chosen females, maintained in long-day photoperiodic conditions (LD 14 h:10 h) for 1 mon was observed and extreme phenotypes selected. Laying is characterized by two parameters: oviposition interval and laying hour. The birds showed a specific time of laying during 24 h. All eggs were laid in the afternoon between 6.5 and 14 h after lights on (HALO). Two laying profiles were determined: 20% of females with an oviposition interval greater than 24 h (24.7 +/- 0.2 h) (the "delayed" profile) laid progressively later each day until a pause day. The remaining 80% of the females laid at the same time each day, with few pause days and an oviposition interval close to 24 h (24.0 +/- 0.2 h) (the "stable" profile). Among the females, showing this last profile, an intra-individual stability and an inter-individual variability of laying hour was established. Two extreme laying phenotypes were then determined: the "early" phenotype (E) for females laying on average between 7.5 and 9.5 HALO and the "late" phenotype (L) for females laying between 12.5 and 14HALO. In order to study the genetic basis of the laying hour, three females of each extreme phenotype were selected and crossed with two different males. The E and L females produced 57 F1E and 42 F1L daughters, respectively. F1 females displayed both laying profiles. However, the proportion of females displaying a "delayed" profile was higher in the L line (50%) than in the E line (29.8%). For the "stable" daughters, artificial selection induced an advance in laying hour of 4.7% for the E line and a delay of 4.7% for the L line. Realized heritability was estimated at 0.5. Moreover, the laying hour of the daughters was correlated positively to that of the mothers (N = 61; r = 0.45). These results support the notion of heritability of oviposition time in Japanese quail.

Analysis of Variance↗
PubMed2005

Equilibrium, observability and controllability in selection-mutation models.

In this paper we shortly discuss the problem of the equilibrium in the well-known Fisher type selection-mutation model, also providing a formula for particular three-allele models. The considered continuous-time dynamics is a known extension of the classical model of natural selection given by Fisher. We also extend the existing investigation of the observability of Fisher's model to the case when another evolutionary factor, mutation is also present. Moreover, we prove a result of technical character, which makes it possible to apply the methodology of nonlinear systems with invariant manifold, to models of artificial selection. For an illustration, a class of three-allele systems is presented in which the controllability into equilibrium is guaranteed without any condition on the biological parameters.

Algorithms↗
PubMedDate not supplied

[Influence of selection forms on genetic structure of domestic animals].

Analysis of genetic structure of pure and crossbred sheep and cattle with the use of genetic-biochemical markers was carried out. Data on breed- and locus-specific genetic traits, stable in the time, were obtained. In sheep, breed-specific peculiarities of genetic structure partly related with the belonging of breeds to breed groups with fine-, semi-fine and coarse wool. The preferable influence of artificial selection at the phenotype complex traits in comparison with natural selection and animal origin on the genetic structure of crossbred sheep was revealed. However, the more profound effects of natural selection on the genetic structure of crossbred cattle were observed.

Alleles↗
PubMed1991

Morphometric traits and femoral histomorphometry in mice selected for body conformation.

Skeleton characteristics and femoral histomorphometry were investigated in two lines of mice divergently selected for antagonistic conformations (CBi/C: high body weight-short tail; CBi/L: low body weight-long tail). An unselected control line (CBi) was used. Genotypes were a significant source of variation for almost all traits studied (body size, skeletal measurements, histomorphometry of the femur, number of caudal vertebrae) indicating that eighteen generations of artificial selection were successful in modifying phenotypes. Antagonistic selection revealed an association between the mechanisms that regulate skeleton growth and body conformation. Trunk length seemed to be dependent of the biomass a mouse would attain. Femur length and its morphometric characteristics were conditioned by other factors than body weight. The observed response in caudal vertebrae number could be explained if this character is considered as a threshold one. The selective procedure applied in this research was also useful to study other biological characters such as fat deposition, immune reactions and bone biomechanics.

Animals↗
PubMedDate not supplied

Effect of linkage on the control of inbreeding in selection programmes.

Selection and mating methods for controlling inbreeding in selection programmes are based on relationships obtained from pedigrees. The efficiency of these methods has always been tested by studies using genetic models of independent loci. However, under linkage the rate of inbreeding obtained from pedigrees can be different from the probability of identity by descent of genes. We simulated a quantitative trait under artificial selection controlled by a large number of genes spread on genome regions of different sizes. A method to control inbreeding based on minimising the average coancestry of selected individuals with a restriction in the loss of selection response, and a mating procedure to control inbreeding were applied. These methods, that use coancestry relationships, were not effective in controlling inbreeding when the genome sizes were smaller than five morgans or so. However, for larger genome sizes the methods were sufficiently efficient. For very tight linkage, methods that utilise molecular information from markers should be used. We finally discuss the effects of the selection of individual major genes on the neutral variability of adjacent genome regions.

Journal Article↗
PubMed2005

Microsatellite analysis of royal jelly producing traits of Italian honeybee (Apis mellifera Liguatica).

Genetic variations at 10 microsatellite loci were surveyed to determine the evolutionary relationships and molecular characteristics of three different honeybee (Apis mellifera L.) populations from Italy and China, i. e., native Italian (Ee), Chinese-Italian (Eb) and selected high royal jelly producing bees (Ea). A total of 96 alleles,an average of 9.6 alleles per locus,were scored in Ee,Eb and Ea bees at 10 loci. Out of which 48 (5%) were different. This indicated a high degree of polymorphism and ever, some genetic differentiation among the three populations due to artificial selection and geographical isolation. The polymorphic information contents (PIC) and heterozyosity of the three populations at 10 loci were 0.57, 0.50, 0.57, and 0.60, 0.57, 0.61, for Ee, Eb, Ea populations respectively, neither of which were different. This indicated same gene diversity within the three populations. The genetic distance was shorter between Ee and Eb bees as well as between Eb and Ea bees. Whereas that between Ee and Eb bees was longer. Further analysis indicated that the allele frequency of seven alleles at six loci (159 bp at A29,100 bp and 104 bp at A24; 110 bp at A7; 126 bp at A43, 221 bp at A14 and 221 bp at A113) increased going from Ee to Eb to Ea bees. Paired tests showed significant higher allele frequency between Ea and Eb bees,as well as between Ea and Eb bees. This indicates that these seven alleles are likely molecular markers of the high royal jelly producing bees. In addition,the allele frequency of four alleles at four loci (106 bp at A24,140 bp at A43;215 bp at A113 and 219 bp at A14) decreased going from Ea bees to Eb to Ee. Paired tests indicated significant lower allele frequency between Ea and Ee bees,as well as between Ea and Eb bees. Those four alleles may be the genetic markers for low royal jelly production.

Alleles↗
PubMed2004

Maize selection passes the century mark: a unique resource for 21st century genomics.

The Illinois Long-Term Selection Experiment for grain protein and oil concentration in maize (Zea mays) is the longest continuous genetics experiment in higher plants. A total of 103 cycles of selection have produced nine related populations that exhibit phenotypic extremes for grain composition and a host of correlated traits. The use of functional genomics tools in this unique genetic resource provides exciting opportunities not only to discover the genes that contribute to phenotypic differences but also to investigate issues such as the response of plant genomes to artificial selection, the genetic architecture of quantitative traits and the source of continued genetic variation within domesticated crop genomes.

Genome, Plant↗
PubMed2000

Genetic variance of sexually selected traits in waxmoths: maintenance by genotype x environment interaction.

When traits experience directional selection, such as that imposed by sexual selection, their genetic variance is expected to diminish. Nonetheless, theory and findings from sexual selection predict and demonstrate that male traits favored by female choice retain substantial amounts of additive genetic variance. We explored this dilemma through an ecological genetic approach and focused on the potential contributions of genotype x environment interaction (GEI) to maintenance of additive genetic variance for male signal characters in the lesser waxmoth, Achroia grisella (Lepidoptera: Pyralidae). We artificially selected genetic variants for two male signal characters, signal rate (SR) and peak amplitude (PA), that influence female attraction and then examined the phenotypic plasticity of these variants (high- and low-SR and high- and low-PA lines) under a range of environmental conditions expected in natural populations. Our split-family breeding experiments indicated that two signal characters, SR and PA, and several developmental characters in both high- and low-SR and high- and low-PA lines displayed considerable phenotypic plasticity among the environments tested. Moreover, strong GEIs leading to crossover between high- and low-SR lines were found for SR and developmental period. Therefore, neither high- nor low-SR genetic variants would achieve maximum attractiveness and fitness in every environment, and those variants producing unattractive signals with low SRs under normal conditions may remain in populations provided that gene flow across environments or generation overlap are sufficiently high. We speculate that the phenotypic plasticity for SR and developmental period is adaptive in A. grisella populations experiencing a range of temperature and density conditions. Females mating with attractive (high-SR) males may be assured of obtaining good genes because these males sire offspring that develop more rapidly and a crossover for developmental period may parallel that for SR. Such parallel crossovers may be expected wherever good-genes sexual selection mechanisms operate.

Adaptation, Physiological↗
PubMed1995

Accumulation of mutations affecting body weight in inbred mouse lines.

The variation from spontaneous mutations for 6-week body weight in the mouse was estimated by selection from a cross of two inbred sublines, C57BL/6 and C57BL/10, separated about 50 years previously from the same inbred line. Selection was practised high and low for 12 generations from the F2, followed by one generation of relaxation. The lines diverged by approximately 1.7 g or 0.7 sd. The additive genetic variance was estimated in the F2 by restricted maximum likelihood and from the selection response, and from this variance the mutational heritability hM2 was estimated using the number of generations since divergence. Estimates of hM2 range from 0.08 to 0.10% depending on the method of analysis. These estimates are similar to those found for other species, but lower than other estimates for the mouse. It is concluded that substantial natural and, perhaps, artificial selection operated during the maintenance of the sublines.

Animals↗
PubMed2006

Experimental evolution of phenotypic plasticity: how predictive are cross-environment genetic correlations?

Genetic correlations are often predictive of correlated responses of one trait to selection on another trait. There are examples, however, in which genetic correlations are not predictive of correlated responses. We examine how well a cross-environment genetic correlation predicts correlated responses to selection and the evolution of phenotypic plasticity in the seed beetle Stator limbatus. This beetle exhibits adaptive plasticity in egg size by laying large eggs on a resistant host and small eggs on a high-quality host. From a half-sib analysis, the cross-environment genetic correlation estimate was large and positive (rA=0.99). However, an artificial-selection experiment on egg size found that the realized genetic correlations were positive but asymmetrical; that is, they depended on both the host on which selection was imposed and the direction of selection. The half-sib estimate poorly predicted the evolution of egg size plasticity; plasticity evolved when selection was imposed on one host but did not evolve when selection was imposed on the other host. We use a simple two-locus additive genetic model to explore the conditions that can generate the observed realized genetic correlation and the observed pattern of plasticity evolution. Our model and experimental results indicate that the ability of genetic correlations to predict correlated responses to selection depends on the underlying genetic architecture producing the genetic correlation.

Animals↗
PubMed2004

Realized heritability and repeatability of risk-taking behaviour in relation to avian personalities.

Personalities are general properties of humans and other animals. Different personality traits are phenotypically correlated, and heritabilities of personality traits have been reported in humans and various animals. In great tits, consistent heritable differences have been found in relation to exploration, which is correlated with various other personality traits. In this paper, we investigate whether or not risk-taking behaviour is part of these avian personalities. We found that (i) risk-taking behaviour is repeatable and correlated with exploratory behaviour in wild-caught hand-reared birds, (ii) in a bi-directional selection experiment on 'fast' and 'slow' early exploratory behaviour, bird lines tend to differ in risk-taking behaviour, and (iii) within-nest variation of risk-taking behaviour is smaller than between-nest variation. To show that risk-taking behaviour has a genetic component in a natural bird population, we bred great tits in the laboratory and artificially selected 'high' and 'low' risk-taking behaviour for two generations. Here, we report a realized heritability of 19.3 +/- 3.3% (s.e.m.) for risk-taking behaviour. With these results we show in several ways that risk-taking behaviour is linked to exploratory behaviour, and we therefore have evidence for the existence of avian personalities. Moreover, we prove that there is heritable variation in more than one correlated personality trait in a natural population, which demonstrates the potential for correlated evolution.

Analysis of Variance↗
PubMed2006

Impacts of genetic bottlenecks on soybean genome diversity.

Soybean has undergone several genetic bottlenecks. These include domestication in Asia to produce numerous Asian landraces, introduction of relatively few landraces to North America, and then selective breeding over the past 75 years. It is presumed that these three human-mediated events have reduced genetic diversity. We sequenced 111 fragments from 102 genes in four soybean populations representing the populations before and after genetic bottlenecks. We show that soybean has lost many rare sequence variants and has undergone numerous allele frequency changes throughout its history. Although soybean genetic diversity has been eroded by human selection after domestication, it is notable that modern cultivars have retained 72% of the sequence diversity present in the Asian landraces but lost 79% of rare alleles (frequency </=0.10) found in the Asian landraces. Simulations indicated that the diversity lost through the genetic bottlenecks of introduction and plant breeding was mostly due to the small number of Asian introductions and not the artificial selection subsequently imposed by selective breeding. The bottleneck with the most impact was domestication; when the low sequence diversity present in the wild species was halved, 81% of the rare alleles were lost, and 60% of the genes exhibited evidence of significant allele frequency changes.

Alleles↗