Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “adaptive evolution”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,495 records · Page 83Linked to original sources
PubMed1976

The evolutionary role of gravity.

Analysis of the part played by gravity in development in the organic world shows that this factor has had an impact on evolution. All terrestrial organisms, including man, have adapted themselves to gravity by developing a number of important features of their composition and functions. Variations of gravitational field in any direction bring about numerous changes in organisms, ranging from metabolism to changes in more conservative systems which also include hereditary structures. Gravitational forces determine the form and the size of organisms, the development of skeletal supporting organs, and energetics. The study of the role of gravity in the variability of the organic world will be of great importance for long-term systems of life support and for work on space orbital stations or at bases on the moon and planets where gravitational forces may differ greatly those from on the earth.

Adaptation, Biological↗
PubMed2003

Visual background complexity facilitates the evolution of camouflage.

Cryptic animal coloration or camouflage is an adaptation that decreases the risk of detection. The study of the evolution of camouflage has strongly emphasized the minimization of visual information that predators receive from prey, by means of background matching. However, the evolutionary effects of information processing after its reception have been virtually ignored. I constructed a model that employs an artificial neural network and simulates the evolution of prey coloration in a visually complex and simple habitat. The model suggests: (1) the difficulty of a detection task is related to the visual complexity of the habitat; (2) it is easier to decrease the risk of detection by the means of camouflage in a visually complex habitat; (3) selection on camouflage can exploit limitations in predators information processing; and (4) there are shortcomings in using the degree of background matching as the measure of camouflage.

Adaptation, Physiological↗
PubMed2005

Intra-host evolutionary dynamics of hepatitis C virus E2 in treated patients.

Hepatitis C virus (HCV) displays high genetic diversity. Inter-host sequence variability may mainly reflect a neutral drift evolution. In contrast, intra-host evolution may be driven by an adaptive selection to host responses to infection. Here, HCV E2 intra-host evolution in two patients during the course and follow-up of successive treatments with IFN-alpha and IFN-alpha/ribavirin was investigated. Phylogenetic analyses suggested that adaptive pressures prompt a continuous selection of viral variants derived from the previous ones (intra-lineage evolution) and/or a swapping of viral lineages during the course of the infection (inter-lineage evolution). Selection would act not only on the phenotypic features of hypervariable region 1 (HVR1) but also on those of the flanking regions. The pressures operate mainly at the amino acid level, but they also appeared to act on nucleotide sequences. Moreover, HVR1 heterogeneity seemed to be strongly constrained. This work contributes to the knowledge of HCV intra-host evolution during chronicity.

Antiviral Agents↗
PubMed2006

Geographic structure of pollinator communities, reproductive assurance, and the evolution of self-pollination.

Reproductive assurance is often invoked as an explanation for the evolution of self-fertilization in plants. However, key aspects of this hypothesis have received little empirical support. In this study, I use geographic surveys of pollinator communities along with functional studies of floral trait variation to examine the role of pollination ecology in mating system differentiation among populations and subspecies of the annual plant Clarkia xantiana. A greenhouse experiment involving 30 populations from throughout the species' range indicated that variation in two floral traits, herkogamy and protandry, was closely related to levels of autofertility and that trait variation was partitioned mainly among populations. Emasculation experiments in the field showed that autonomous selfing confers reproductive assurance by elevating fruit and seed production. Surveys of pollinator communities across the geographic range of the species revealed that bee pollinator abundance and community composition differed dramatically between populations of the outcrossing subspecies xantiana and the selfing subspecies parviflora despite their close proximity. Specialist bee pollinators of Clarkia were absent from selfing populations, but they were the most frequent visitors to outcrossing populations. Moreover, within the outcrossing subspecies xantiana, there was a close correspondence between specialist abundance and population differentiation in herkogamy, a key mating system trait. This spatial covariation arose, in part, because geographically peripheral populations had reduced herkogamy, higher autofertility, and lower pollinator abundance compared to central populations of xantiana. Finally, I detected strong spatial structure to bee communities both across the range of the species and within the outcrossing subspecies. In both cases, spatial structure was stronger for specialist bees compared to generalist bees, and pollinator communities varied in parallel with population variation in herkogamy. These results provide evidence that mating system differentiation parallels spatial variation in pollinator abundance and community composition at both broad and more restricted spatial scales, consistent with the hypothesis that pollinator abundance and reproductive assurance are important drivers of plant mating system evolution.

Adaptation, Biological↗
PubMed1997

Paleobiology of the Mesoproterozoic-Neoproterozoic transition: the Sukhaya Tunguska Formation, Turukhansk Uplift, Siberia.

Silicified carbonates of the latest Mesoproterozoic Sukhaya Tunguska Formation, northwestern Siberia, contain abundant and diverse permineralized microfossils. Peritidal environments are dominated by microbial mats built by filamentous cyanobacteria comparable to modern species of Lyngbya and Phormidium. In subtidal to lower intertidal settings, mat-dwelling microbenthos and possible coastal microplankton are abundant. In contrast, densely woven mat populations with few associated taxa characterize more restricted parts of tidal flats; the preservation of vertically oriented sheath bundles and primary fenestrae indicates that in these mats carbonate cementation was commonly penecontemporaneous with mat growth. Eoentophysalis mats are limited to restricted environments where microlaminated carbonate precipitates formed on or just beneath the sediment surface. Most microbenthic populations are cyanobacterial, although eukaryotic microfossils may occur among the simple spheroidal cells interpreted as coastal plankton. Protists are more securely represented by large (up to 320 micrometers in diameter) but poorly preserved acritarchs in basinal facies. The Sukhaya Tunguska assemblage contains 27 species in 18 genera. By virtue of their stratigraphic longevity and their close and predictable association with specific paleoenvironmental conditions, including substrates, Proterozoic cyanobacteria support a model of bacterial evolution in which populations adapt rapidly to novel environments and, thereafter, resist competitive replacement. The resulting evolutionary pattern is one of accumulation and stasis rather than the turnover and replacement characteristic of Phanerozoic plants and animals.

Biological Evolution↗
PubMed1979

The mine--body problem in an evolutionary perspective.

Charles Darwin realized that his theory of evolution, jointly with the psychoneural identity hypothesis, implies the conjecture that behaviour and ideation evolve alongside anatomical and physiological traits. He was therefore the founder of evolutionary psychology. However, this science has not been pursued with vigour: not even its name has attained currency. In fact most psychologists still think in a pre-evolutionary fashion and seldom ask questions about the adaptive value and possible evolution of behavioural and mental traits. One reason for the underdevelopment of evolutionary psychology is that, on the whole, psychology is still separate from biology. In turn, one reason for this estrangement between close relatives is that psychology is still to some extent in the grip of psychoneural dualism, or the prehistoric belief that mind and body are separate entities. This doctrine is bound to block the advance of evolutionary psychology because a dualist must either deny mental evolution or speculate that it proceeds by some mechanism other than genic variation and natural (and social) selection. On the other hand the psychoneural identity hypothesis fits in with biology and, in particular, with evolutionary biology. Moreover, by construing ideation as a brain process, psychoneural monism explains how ideas (via behaviour) can become a motor of evolution as well as an outcome of it. So, it is in the interest of evolutionary psychologists to pay closer attention to the mind-body problem and to adopt the psychoneural identity hypothesis and turn it into a full-fledged scientific theory.

Animals↗
PubMed2001

Evolution of genome-phenome diversity under environmental stress.

The genomic era revolutionized evolutionary biology. The enigma of genotypic-phenotypic diversity and biodiversity evolution of genes, genomes, phenomes, and biomes, reviewed here, was central in the research program of the Institute of Evolution, University of Haifa, since 1975. We explored the following questions. (i) How much of the genomic and phenomic diversity in nature is adaptive and processed by natural selection? (ii) What is the origin and evolution of adaptation and speciation processes under spatiotemporal variables and stressful macrogeographic and microgeographic environments? We advanced ecological genetics into ecological genomics and analyzed globally ecological, demographic, and life history variables in 1,200 diverse species across life, thousands of populations, and tens of thousands of individuals tested mostly for allozyme and partly for DNA diversity. Likewise, we tested thermal, chemical, climatic, and biotic stresses in several model organisms. Recently, we introduced genetic maps and quantitative trait loci to elucidate the genetic basis of adaptation and speciation. The genome-phenome holistic model was deciphered by the global regressive, progressive, and convergent evolution of subterranean mammals. Our results indicate abundant genotypic and phenotypic diversity in nature. The organization and evolution of molecular and organismal diversity in nature at global, regional, and local scales are nonrandom and structured; display regularities across life; and are positively correlated with, and partly predictable by, abiotic and biotic environmental heterogeneity and stress. Biodiversity evolution, even in small isolated populations, is primarily driven by natural selection, including diversifying, balancing, cyclical, and purifying selective regimes, interacting with, but ultimately overriding, the effects of mutation, migration, and stochasticity.

Animals↗
PubMed2004

Adaptive mutation and amplification in Escherichia coli: two pathways of genome adaptation under stress.

The neo-Darwinists suggested that evolution is constant and gradual, and thus that genetic changes that drive evolution should be too. However, more recent understanding of phenomena called adaptive mutation in microbes indicates that mutation rates can be elevated in response to stress, producing beneficial and other mutations. We review evidence that, in Escherichia coli, two separate mechanisms of stress-induced genetic change occur that revert a lac frameshift allele allowing growth on lactose medium. First, compensatory frameshift ("point") mutations occur by a mechanism that includes DNA double-strand breaks and (we have suggested) their error-prone repair. Point mutation requires induction of the RpoS-dependent general stress response, and the SOS DNA damage response leading to upregulation of the error-prone DNA polymerase DinB (Pol IV), and occurs during a transient limitation of post-replicative mismatch repair activity. A second mechanism, adaptive amplification, entails amplification of the leaky lac allele to 20-50 tandem repeats. These provide sufficient beta-galactosidase activity for growth, thereby apparently deflecting cells from the point mutation pathway. Unlike point mutation, amplification neither occurs in hypermutating cells nor requires SOS or DinB, but like point mutation, amplification requires the RpoS-dependent stress response. Similar processes are being found in other bacterial systems and yeast. Stress-induced genetic changes may underlie much of microbial evolution, pathogenesis and antibiotic resistance, and also cancer formation, progression and drug resistance.

Adaptation, Biological↗
PubMed1998

Nonadditivity of mutational effects on the properties of catalase I and its application to efficient directed evolution.

Catalase I of Bacillus stearothermophilus has high catalatic and low peroxidatic activities. The mutant from the first random mutant population, D130N, which has higher peroxidatic and lower catalatic activities than those exhibited by the wild-type enzyme, was subjected to second random mutagenesis in observance of the change in reaction specificity. From the second mutant population, the mutant I108T/D130N/I222T was selected and examined. The reaction specificity of the purified enzymes revealed that catalase I being originally 98% catalase and 2% peroxidase was brought to 58% specificity to peroxidase after two-step adaptive walks. From the statistical analysis of the two random mutant populations, the average degree of nonadditivity of the mutational effects was estimated to be 0.13 irrespective of the properties of the enzyme. It was demonstrated that the distribution pattern of a property of the second mutant population can be predicted well from the data of the first mutant population by taking into consideration the degree of nonadditivity. The strategy for an efficient adaptive walk in directed evolution of enzymes through the prediction of appropriate mutation rate and effective sample size for further mutation and selection was presented and discussed.

Catalase↗
PubMed2000

Comparative analyses for adaptive radiations.

Biologists generally agree that most morphological variation between closely related species is adaptive. The most common method of comparative analysis to test for co-evolved character variation is based on a Brownian-motion model of character evolution. If we are to test for the evolution of character-covariation, and we believe that characters have evolved adaptively to fill niches during an adaptive radiation, then it is appropriate to employ appropriate models for character evolution. We show here that under several models of adaptive character evolution and coevolution during an adaptive radiation, which result in closely related species being more similar to each other than to more distantly related species, cross-species analyses are statistically more appropriate than contrast analyses. If the evolution of some traits fits the Brownian-motion model, while others evolve to fill niches during an adaptive radiation, it might be necessary to identify the number of relevant niche dimensions and the modes of character evolution before deciding on appropriate statistical procedures. Alternatively, maximum-likelihood procedures might be used to determine appropriate transformations of phylogenetic branch lengths that accord with particular models of character evolution.

Adaptation, Physiological↗
PubMed1989

Food, reproduction and longevity: is the extended lifespan of calorie-restricted animals an evolutionary adaptation?

Calorie restriction results in an increased lifespan and reduced fecundity of rodents. In a natural environment the availability of food will vary greatly. It is suggested that Darwinian fitness will be increased if animals cease breeding during periods of food deprivation and invest saved resources in maintenance of the adult body, or soma. This would increase the probability of producing viable offspring during an extended lifespan. The diversion of limited energy resources from breeding to maintenance of the soma is seen as an evolutionary adaptation, fully compatible with the 'disposable soma' theory of the evolution of ageing.

Adaptation, Physiological↗