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At least 325 records · Page 18Linked to original sources
PubMed2004

Immunomodulatory function of seminal catecholamines may be an adaptation for reproduction.

Catecholamines are found at high concentrations in seminal fluid. The exact functional significance of seminal catecholamines is unknown. We hypothesize that seminal catecholamines perform important immunomodulatory functions that support reproductive success. Specifically, we propose that catecholamines contribute to a local adaptive shift of T helper (Th) balance to Th2 dominance in the maternal reproductive tract to enable the gametes, and possibly the nascent zygote, to evade immune surveillance of the female. Our hypothesis suggests that the Th2 effects of catecholamines are independent of the direct immunomodulatory effects of seminal cytokines such as prostaglandin E2 and transforming growth factor beta1. Potential immunomodulatory functions of other seminal constituents such as aldosterone, oxytocin, vasopressin, and angiotensin remain unexplored and represents a topic of future interest. Seminal stress hormones may play a role in mating dynamics since alpha males typically live in a state of high hormonal stress, Mating with adrenalized alpha males may represent an adaptive Darwinian strategy by females to maximize their reproductive fitness.

Adaptation, Physiological↗
PubMed2026

Population and landscape genomics provide insights into the adaptive genetic variation and future climate-induced vulnerability of the endangered tree species Phoebe bournei.

Elucidating the genomic underpinnings of adaptive variation is highly important for the conservation, landscape application, and management of ornamental trees against the backdrop of global climate change. However, research on the genetic mechanisms underlying climate adaptation in Phoebe bournei-a near-threatened subtropical tree species endemic to China, which is endowed with exceptionally high ornamental and ecological value-remains scarce. Whole-genome resequencing was conducted on 362 individuals from 27 natural populations across the geographical range of the species. Genome-environment association analyses were employed to identify 1556 climate-associated variants and 167 candidate genes associated with temperature and precipitation variables. Through functional annotation and expression profiling, pivotal genes, including TRX-M4 and FBD1, were identified as integral to drought and heat stress responses, with adaptive alleles displaying distinct geographic frequency distributions and significant phenotypic differentiation. Divergent evolutionary trajectories were deduced among populations, with southeastern populations distinguished by elevated genetic diversity and strong signatures of local adaptation. Nevertheless, projections derived from the Risk of Non-Adaptedness and gradient forest models suggest that these southeastern populations will face substantial genomic offset under future climate scenarios, signaling heightened vulnerability and the need for prioritized conservation and management. This study provides the first genome-wide perspective into the adaptive evolution of P. bournei and offers a robust foundation for its conservation and climate-resilient management.

Journal Article↗
PubMed2001

Evolution of adaptive synapses: robots with fast adaptive behavior in new environments.

This paper is concerned with adaptation capabilities of evolved neural controllers. We propose to evolve mechanisms for parameter self-organization instead of evolving the parameters themselves. The method consists of encoding a set of local adaptation rules that synapses follow while the robot freely moves in the environment. In the experiments presented here, the performance of the robot is measured in environments that are different in significant ways from those used during evolution. The results show that evolutionary adaptive controllers solve the task much faster and better than evolutionary standard fixed-weight controllers, that the method scales up well to large architectures, and that evolutionary adaptive controllers can adapt to environmental changes that involve new sensory characteristics (including transfer from simulation to reality and across different robotic platforms) and new spatial relationships.

Computer Simulation↗
PubMed2002

Genetically based polymorphisms in morphology and life history associated with putative host races of the water lily leaf beetle, Galerucella nymphaeae.

A host race is a population that is partially reproductively isolated from other conspecific populations as a direct consequence of adaptation to a specific host. The initial step in host race formation is the establishment of genetically based polymorphisms in, for example, morphology, preference, or performance. In this study we investigated whether polymorphisms observed in Galerucella nymphaeae have a genetic component. Galerucella nymphaeae, the water lily leaf beetle, is a herbivore which feeds and oviposits on the plant hosts Nuphar lutea and Nymphaea alba (both Nymphaeaceae) and Rumex hydrolapathum and Polygonum amphibium (both Polygonaceae). A full reciprocal crossing scheme (16 crosses, each replicated 10 times) and subsequent transplantation of 1,001 egg clutches revealed a genetic basis for differences in body length and mandibular width. The heritability value of these traits, based on midparent-offspring regression, ranged between 0.53 and 0.83 for the different diets. Offspring from Nymphaeaceae parents were on average 12% larger and had on average 18% larger mandibles than offspring from Polygonaceae parents. Furthermore, highly significant correlations were found between feeding preference of the offspring and the feeding preference of their parents. Finally, two fitness components were measured: development time and survival. Development time was influenced by diet, survival both by cross type and diet, the latter of which suggest adaptation of the beetles. This suggestion is strengthened by a highly significant cross x diet interaction effect for development time as well as for survival, which is generally believed to indicate local adaptation. Although no absolute genetic incompatibility among putative host races was observed, survival of the between-host family offspring, on each diet separately, was lower than the survival of the within-host family offspring on that particular host. Survival of offspring of two Nymphaeaceae parents was about two times higher on Nymphaeaceae than on Polygonaceae, whereas survival of offspring of two Polygonaceae parents was 11 times higher on Polygonaceae than on Nymphaeaceae (based on untransformed data). Based on these results, we conclude that genetically determined polymorphisms in morphology and feeding preference exist in G. nymphaeae, resulting in differential performance. Furthermore, in each diet separately, offspring of between-host family crosses were less fit than offspring of within-host family crosses. These results support the hypothesis that within this species two host races can be distinguished.

Adaptation, Physiological↗
PubMed2004

The genetic basis of adaptive population differentiation: a quantitative trait locus analysis of fitness traits in two wild barley populations from contrasting habitats.

We used a quantitative trait locus (QTL) approach to study the genetic basis of population differentiation in wild barley, Hordeum spontaneum. Several ecotypes are recognized in this model species, and population genetic studies and reciprocal transplant experiments have indicated the role of local adaptation in shaping population differences. We derived a mapping population from a cross between a coastal Mediterranean population and a steppe inland population from Israel and assessed F3 progeny fitness in the natural growing environments of the two parental populations. Dilution of the local gene pool, estimated as the proportion of native alleles at 96 marker loci in the recombinant lines, negatively affected fitness traits at both sites. QTLs for fitness traits tended to differ in the magnitude but not in the direction of their effects across sites, with beneficial alleles generally conferring a greater fitness advantage at their native site. Several QTLs showed fitness effects at one site only, but no opposite selection on individual QTLs was observed across the sites. In a common-garden experiment, we explored the hypothesis that the two populations have adapted to divergent nutrient availabilities. In the different nutrient environments of this experiment, but not under field conditions, fitness of the F3 progeny lines increased with the number of heterozygous marker loci. Comparison of QTL-effects that underlie genotype x nutrient interaction in the common-garden experiment and genotype x site interaction in the field suggested that population differentiation at the field sites may have been driven by divergent nutrient availabilities to a limited extent. Also in this experiment no QTLs were observed with opposite fitness effects in contrasting environments. Our data are consistent with the view that adaptive differentiation can be based on selection on multiple traits changing gradually along ecological gradients. This can occur without QTLs showing opposite fitness effects in the different environments, that is, in the absence of genetic trade-offs in performance between environments.

Adaptation, Biological↗
PubMed2025

Experimental Evolution of Poxviruses.

Experimental evolution is the process of exposing virus populations to defined selective pressures in a laboratory setting to identify adaptive changes. Coupled with deep sequencing, this experimental approach allows for nucleotide-level resolution of poxvirus adaptive strategies over time. Here, we present a general method of poxvirus experimental evolution, Illumina-based deep sequencing, and bioinformatic analyses to identify structural changes (e.g., gene duplication) as well as local adaptive changes (e.g., small indels and single nucleotide polymorphisms).

Poxviridae↗
PubMed1995

Suprathreshold contrast perception across differences in mean luminance: effects of stimulus size, dichoptic presentation, and length of adaptation.

Contrast constancy across changes in mean luminance was reported to hold over a wide range of luminances in a few studies and to be limited to approximately 1 log unit in another. The studies reporting contrast constancy over a wide luminance range used extended grafting stimuli presented dichoptically (bright stimulus to one eye and dim stimulus to the other) with long adaptation periods. The study reporting only limited constancy used narrow (1-octave-wide) Gabor patches presented side by side to both eyes with only a short (up to 5 s) period of adaptation. The current study was designed to determine whether differences in stimulus bandwidth, presentation format, or adaptation time could account for the different results reported. It was found that increasing stimulus size had no effect on the results. Dichoptic presentation with either a filter in front of one eye or calibrated screen luminance could account for the differences between the studies. When dichoptic presentation was combined with short adaptation periods (of a few seconds) an intermediate deviation from constancy was demonstrated. This effect suggests that the deviations from constancy demonstrated under free viewing are due to a lack of fast local adaptation and not to long-distance interactions across the retina.

Adult↗
PubMed1996

Management of venous leg ulcers.

In the management of leg ulcers two aspects should be considered, i.e. the exact underlying condition (main cause and contributing factors) and local conditions. Concomitant peripheral arterial occlusive disease must systematically be excluded. Effective compression therapy (35 mmHg pressure at the distal calf) is the corner-stone in treatment of venous leg ulcers. Superficial venous reflux can be the major cause of chronic venous insufficiency. Careful examination of reflux patterns helps to distinguish between indications for conservative treatment and indications suitable for surgical treatment. To what extent the stripping of varicose veins and/or endoscopic subfascial perforator vein discision really improves the outcome and prevents recurrence still remains to be shown in controlled trials. Local treatment considers ulcer wound bed and border. Modern synthetic wound dressings follow the concept of moist wound healing whilst local application of growth factors is currently under clinical evaluation. Management of eczema includes avoidance of potent or known allergens, patch tests in severe cases with suspicion of contact dermatitis and an adapted local therapy.

Humans↗
PubMed2001

A field cage test of the effects of the endosymbiont Wolbachia on Drosophila melanogaster.

Wolbachia endosymbionts are known to affect the fitness of their hosts, but most of this information is from laboratory studies. In Drosophila melanogaster, Wolbachia frequencies vary clinically in frequency in Australia and may confound climatic adaptation. Here we use field cages in a reciprocal exchange design to test for Wolbachia effects in D. melanogaster in winter at temperate and tropical sites. Infected flies of both populations had a lower fecundity in tropical north Queensland, whilst in temperate southern Victoria Wolbachia effects depended on the nuclear population background. Here infected flies from Victoria were more fecund. Wolbachia also influenced larval/pupal viability in the tropics but this was dependent on population background. In comparisons of the populations, there was no evidence for local adaptation for total fecundity, viability or survival over winter. However, in Victoria, a local population had a higher late-life fecundity than a tropical population from Queensland that had higher early-life fecundity. At a tropical site, local Queensland flies had a higher early fecundity than Victorian flies. In contrast to many laboratory studies, mortality rates in the field cages increased only slightly over time. Both the Wolbachia effects and population differences have not been previously detected in laboratory studies with D. melanogaster and highlight the utility of Drosophila field studies in fitness experiments.

Analysis of Variance↗
PubMed2005

A microcosm test of adaptation and species specific responses to polluted sediments applicable to indigenous chironomids (Diptera).

Chironomids may adapt to pollution stress but data are confined to species that can be reared in the laboratory. A microcosm approach was used to test for adaptation and species differences in heavy metal tolerance. In one experiment, microcosms containing different levels of contaminants were placed in polluted and reference locations. The response of Chironomus februarius to metal contaminants suggested local adaptation: relatively more flies emerged from clean sediment at the reference site and the reverse pattern occurred at the polluted site. However, maternal effects were not specifically ruled out. In another species, Kiefferulus intertinctus, there was no evidence for adaptation. In a second experiment, microcosms with different contaminant levels were placed at two polluted and two unpolluted sites. Species responded differently to contaminants, but there was no evidence for adaptation in the species where this could be tested. Adaptation to heavy metals may be uncommon and species specific, but more sensitive species need to be tested across a range of pollution levels. Factors influencing the likelihood of adaptation are briefly discussed.

Acclimatization↗
PubMed2025

Do Snow-Adapted Prey Facilitate Coexistence of the Sierra Nevada Red Fox With Sympatric Carnivores?

Specialist species in alpine ecosystems may be increasingly threatened by climate-driven habitat loss and encroachment by generalist competitors. Ecological theory predicts that niche differentiation through dietary specialisation can facilitate coexistence with generalist competitors. We quantified dietary overlap between a high-elevation specialist, the Sierra Nevada red fox (SNRF; Vulpes vulpes necator) and a widespread generalist, the coyote (Canis latrans), as well as other sympatric carnivores. We were especially interested in dietary items that were themselves specialised to alpine habitats, as we expected them to be most critical to SNRF. To characterise diet, we used DNA metabarcoding for vertebrate and plant-based food items of 789 carnivore scats collected from the sites of two SNRF populations (Lassen, Sierra Nevada). As expected for potential competitors, SNRFs exhibited substantial dietary overlap with coyotes overall. Dietary niche overlap was lower between SNRF and both bobcats (Lynx rufus) and martens (Martes caurina). Compared to coyotes, however, SNRF more frequently consumed snow-adapted prey, including white-tailed jackrabbits (Lepus townsendii) and American pika (Ochotona princeps) (SIMPER p ≤ 0.005), especially during periods of deep snow. Whitebark pine (Pinus albicaulis; presumably seeds) also appeared more regularly in SNRF winter diets compared to coyotes. These findings support the hypothesis that co-adapted subalpine prey facilitate coexistence between specialist and generalist carnivores by increasing the competitive advantage of specialists under snowier conditions. This environment-mediated shift in competitive dynamics implies that the fates of locally adapted predator and prey may be tightly linked, an important consideration for conservation planning in alpine ecosystems.

Animals↗
PubMed2006

Evidence for geographic isolation and signs of endemism within a protistan morphospecies.

The possible existence of endemism among microorganisms resulting from and preserved by geographic isolation is one of the most controversial topics in microbial ecology. We isolated 31 strains of "Spumella-like" flagellates from remote sampling sites from all continents, including Antarctica. These and another 23 isolates from a former study were characterized morphologically and by small-subunit rRNA gene sequence analysis and tested for the maximum temperature tolerance. Only a minority of the Spumella morpho- and phylotypes from the geographically isolated Antarctic continent follow the worldwide trend of a linear correlation between ambient (air) temperature during strain isolation and heat tolerance of the isolates. A high percentage of the Antarctic isolates, but none of the isolates from locations on all other continents, were obligate psychrophilic, although some of the latter were isolated at low ambient temperatures. The drastic deviation of Antarctic representatives of Spumella from the global trend of temperature adaptation of this morphospecies provides strong evidence for geographic transport restriction of a microorganism; i.e., Antarctic protistan communities are less influenced by transport of protists to and from the Antarctic continent than by local adaptation, a subtle form of endemism.

Acclimatization↗
PubMed2004

Variation in how mothers, health visitors and general practitioners use the personal child health record.

BACKGROUND: In the UK, a national personal child health record (PCHR) with local adaptations is in widespread use. Previous studies report that parents find the PCHR useful and that health visitors use it more than other health professionals. This study was carried out in Nottingham, where the local PCHR is similar to the national PCHR. OBJECTIVES: To explore variation in use of the PCHR made by mothers with differing social characteristics, to compare heath visitors' and general practitioners' (GPs') use of the PCHR, and to compare health visitors' and GPs' perceptions of the PCHR with those of mothers for whose children they provide care. METHODS: Questionnaires to 534 parents registered with 28 general practices and interviews with a health visitor and GP at each practice. A score per mother for perceived usefulness of the PCHR was developed from the questionnaire, and variation in the score was investigated by linear regression adjusted for clustering. RESULTS: Four hundred and one (75%) questionnaires were returned. Three hundred and twenty-five (82%) mothers thought the PCHR was very good or good. Higher scores for usage of the PCHR were significantly associated with teenage and first-time mothers, but no association was found with mother's social class, education or being a single parent. There was no association between variation in the score and practice, health visitor or GP characteristics. Mothers, health visitors and GPs reported that mothers took the PCHR to baby clinic more frequently than when seeing their GP, and that health visitors wrote in the PCHR more frequently than GPs. Eighteen (67%) health visitors and 20 (71%) GPs said they had difficulty recording information in the PCHR. CONCLUSION: The PCHR is used by most mothers and is important for providing health promotion material to all families with young children. It may be particularly useful for first-time and teenage mothers.

Adolescent↗
PubMed1976

Forty years of stress research: principal remaining problems and misconceptions.

An overview of the main problems and misconceptions in the clinical application and theoretic evaluation of the stress concept reveals that the same 10 problems appear to cause the greatest difficulties in its application, irrespective of the specialty in which it is used: (1) the correct definition of stress, stressors and the general adaptation syndrome; (2) the concept of nonspecificity in biology and medicine; (3) the conditioning of stress responses by diverse endogenous (mainly genetically determined) and exogenous (environmental) factors; (4) the relation between the genral and the local adaptation syndromes; (5) the difference between direct and indirect pathogens; (6) the definition of the morbid lesions in whose pathogenesis stress plays a particularly prominent role--the so-called diseases of adaptation; (7) the role of genetics versus that of factors under voluntary self-control in mastering biologic stress; (8) the mode of action of syntoxic and catatoxic hormones, drugs and behavioural attitudes; (9) the so-called first mediator of the stress response, which carries the message that a state of stress exists from the directly affected area to the neurohormonal regulatory centres; and (10) the prophylaxis and treatment of stress-induced damage by pharmacologic and behavioural techniques.

Adaptation, Physiological↗
PubMed1994

Effects of poor forage conditions on the behaviour of grazing ruminants.

This paper shows that the study of animal behaviour is a valuable aid to the improvement of the management of grazing livestock under extensive conditions. The food available to grazing animals in developing countries, and particularly in the dry season in the tropics, is often of very low quality and, in addition, is frequently available at low densities per unit area. Grazing ruminants attempt to adapt to these adverse conditions by increasing the time for which they graze each day and also by dispersing more widely. However, the time for which animals can graze may be limited by solar radiation and fly irritation in the day, and by the confining of the animals in pens at night. The adverse effects of the above limitations may be partially overcome when adapted local breeds are used. Dispersion of animals improves their ability to make use of extensive pasture and in order to encourage it, an understanding of the factors that affect it such as breed differences, social behaviour, adaptation and location of watering points and other unique environmental factors must be achieved. The paper concludes with recommendations of areas worth further research.

Adaptation, Physiological↗
PubMed2003

Host-associated genetic structure of Mexican populations of the cabbage aphid Brevicoryne brassicae L. (Homoptera: Aphididae).

Phytophagous insects can use different host plant species across their geographic distribution. Within a locality, however, their feeding can be restricted to one or two plant species. If host species constitute different selective regimes to herbivorous insects, genetic differentiation and host-associated local adaptation may occur. In this study, we describe the genetic structure of the aphid Brevicoryne brassicae L. associated to Brassica campestris L. and B. oleraceae var. capitata L., two plant species that occur sympatrically in four localities in the highlands of Chiapas, Mexico. The aim was to determine if the aphid populations are genetically structured in relation to the plant host species, and if such differentiation is consistent among localities. The genetic description of populations was made using 11 enzyme loci using cellulose acetate electrophoresis. Aphid genotypes were surveyed in two host plant species-associated populations within each of four localities at seven polymorphic loci (eight subpopulations in total). The genetic structure was assessed at the level of subpopulations, among localities, between hosts, and pairwise comparisons of hosts within locality, using Wright F-statistics. Genetic distance among localities and between host-associated populations within each locality was also estimated. We found that overall genetic differentiation was high (FST=0.22), and that differentiation among localities (FST=0.13) was higher than differentiation between hosts (FST=0.03). All FST estimates were statistically significant. Pairwise comparisons of FST between hosts in each locality suggest high differentiation in two of them, and low but still significant differentiation in two other localities. Given that general environmental conditions are similar within localities, selection on each host species may produce genetic divergence within and among subpopulations of B. brassicae.

Animals↗
PubMed2000

Coevolutionary clines across selection mosaics.

Much of the dynamics of coevolution may be driven by the interplay between geographic variation in reciprocal selection (selection mosaics) and the homogenizing action of gene flow. We develop a genetic model of geographically structured coevolution in which gene flow links coevolving communities that may differ in both the direction and magnitude of reciprocal selection. The results show that geographically structured coevolution may lead to allele-frequency clines within both interacting species when fitnesses are spatially uniform or spatially heterogeneous. Furthermore, the results show that the behavior and shape of clines differ dramatically among different types of coevolutionary interaction. Antagonistic interactions produce dynamic clines that change shape rapidly through time, producing shifting patterns of local adaptation and maladaptation. Unlike antagonistic interactions, mutualisms generate stable equilibrium patterns that lead to fixed spatial patterns of adaptation. Interactions that vary between mutualism and antagonism produce both equilibrium and dynamic clines. Furthermore, the results demonstrate that these interactions may allow mutualisms to persist throughout the geographic range of an interaction, despite pockets of locally antagonistic selection. In all cases, the coevolved spatial patterns of allele frequencies are sensitive to the relative contributions of gene flow, selection, and overall habitat size, indicating that the appropriate scale for studies of geographically structured coevolution depends on the relative contributions of each of these factors.

Alleles↗
PubMed2001

How closely correlated are molecular and quantitative measures of genetic variation? A meta-analysis.

The ability of populations to undergo adaptive evolution depends on the presence of quantitative genetic variation for ecologically important traits. Although molecular measures are widely used as surrogates for quantitative genetic variation, there is controversy about the strength of the relationship between the two. To resolve this issue, we carried out a meta-analysis based on 71 datasets. The mean correlation between molecular and quantitative measures of genetic variation was weak (r = 0.217). Furthermore, there was no significant relationship between the two measures for life-history traits (r = -0.11) or for the quantitative measure generally considered as the best indicator of adaptive potential, heritability (r = -0.08). Consequently, molecular measures of genetic diversity have only a very limited ability to predict quantitative genetic variability. When information about a population's short-term evolutionary potential or estimates of local adaptation and population divergence are required, quantitative genetic variation should be measured directly.

Animals↗