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Results for “Evolutionary adaptability”

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PubMed2005

Retrieval improvement is induced by water shortage through angiotensin II.

Angiotensin II (ANGII) has an evolutionary preserved role in determining adaptative responses to water-shortages. In addition, it has been shown to modulate diverse phases of memory. Still, it is not clear whether ANGII improves or spoils memory. We demonstrated that endogenous angiotensins enhance consolidation of a long-term associative memory in the crab Chasmagnathus and that water shortage improves memory consolidation through brain ANGII actions. Here, we show that weakly trained crabs, when water-deprived, exhibit enhanced retrieval. Subsequently, memory retention is indistinguishable from that of strongly trained crabs. ANGII, but not angiotensin IV, is a necessary and sufficient condition for such enhancing effect. We conclude that ANGII released due to water shortage leads to enhanced memory retrieval. Thus, it seems that ANGII has an evolutionary preserved role as a multifunction coordinator that enables an adaptative response to water-shortage. The facilitation of memory consolidation and retrieval would be among those coordinated functions.

Adaptation, Physiological↗

PubMed2000

Limits to natural selection.

We review the various factors that limit adaptation by natural selection. Recent discussion of constraints on selection and, conversely, of the factors that enhance "evolvability", have concentrated on the kinds of variation that can be produced. Here, we emphasise that adaptation depends on how the various evolutionary processes shape variation in populations. We survey the limits that population genetics places on adaptive evolution, and discuss the relationship between disparate literatures.

Animals↗

PubMed2005

Testing the adaptive value of circadian systems.

Circadian clocks are thought to enhance reproductive fitness. However, most of the evidence that supports the adaptiveness of clocks is not rigorous and falls into the category of "adaptive storytelling." Approaches that an evolutionary biologist would consider appropriate to address this issue are described along with an analysis of the evidence-past and present-that has been evoked to demonstrate the adaptive value of circadian systems.

Adaptation, Physiological↗

PubMed2001

Predicting the emergence of resistance to antifungal drugs.

The emergence of antifungal drug resistance is inevitable. Here I discuss antibiotic resistance in the context of the adaptive potential of fungi and I propose an approach to predicting the evolution of antifungal resistance using experimental evolution of DNA sequences and microbial populations. Prediction is based on determination of evolutionary potential at two levels, the gene and the genome. At the level of the gene, evolutionary potential depends on the sequence space of candidate resistance genes defined by the fitness effects of all possible mutations in all possible combinations. At the level of the genome, evolutionary potential depends on the adaptive landscape defined by the fitness effects of all possible interactions among alleles constituting the genotype.

Antifungal Agents↗

PubMed2004

Capturing the adaptive mutation in yeast.

An accurate view of adaptive mutations is essential to evolutionary genetics, but their rarity makes them difficult to study. This can be partially overcome using the many tools of yeast genetics and the ability to study very large populations over many generations. Adaptation to laboratory environments has occurred primarily by chromosomal rearrangements, often involving retrotransposons and apparently selected for their effects on gene regulation. Estimated rates of adaptive mutation are on the order of 1 in 10(11) cell divisions. There remains great potential for the genomic study of variation within yeast species to contribute to our understanding of adaptive mutation.

Adaptation, Biological↗

PubMed2005

The effect of disease life history on the evolutionary emergence of novel pathogens.

We present a general analytical result for the probability that a newly introduced pathogen will evolve adaptations that allow it to maintain itself within any novel host population, as a function of disease life-history parameters. We demonstrate that this probability of "evolutionary emergence" depends on two key properties of the disease life history: (i) the basic reproduction number and (ii) the expected duration of an infection. These parameters encapsulate all of the relevant information and can be combined in a very simple expression, with estimates for the rates of adaptive mutation, to predict the probability of emergence for any novel pathogen. In general, diseases that initially have a large reproductive number and/or that cause relatively long infections are the most prone to evolutionary adaptation.

Adaptation, Physiological↗

PubMed2003

Evolution of complement as an effector system in innate and adaptive immunity.

For a long time, the complement system in mammals has been regarded as a biological system that plays an essential role in innate immunity. More recently, it has been recognized that the complement system contributes heavily to the generation and development of an acquired immune response. In fact, this ancient mechanism of defense has evolved from a primitive mechanism of innate immune recognition in invertebrate species to that of an effector system that bridges the innate with the adaptive immune response in vertebrate species. When and how did complement evolve into a shared effector system between innate and adaptive immunity? To answer this question, our group is interested in understanding the role of complement in innate and adaptive immune responses in an evolutionary relevant species: the teleost fish. The attractiveness of this species as an animal model is based on two important facts. First, teleost fish are one of the oldest animal species to have developed an adaptive immune response. Second, the complement system of teleost fish offers a unique feature, which is the structural and functional diversity of its main effector protein, C3, the third component of the complement system.

Animals↗

PubMed2025

Molecular signatures of adaptive introgression and selection in contact zones of closely related pine species (Pinus genus).

BACKGROUND: Natural hybridization plays a key role in shaping genetic diversity, local adaptation, and the dynamics of speciation through interspecific gene flow. Hybrid zones serve as valuable natural systems for studying these processes. In this research, we used genotypic data at thousands of nuclear SNPs to investigate genomic outcomes of hybridization and selection across three contact zones of closely related pine species including Scots pine (Pinus sylvestris L.) and dwarf mountain pine (P. mugo T.). Reference allopatric stands of parental species were used to assess introgression dynamics. RESULTS: Individuals from the hybrid zones showed distinct genetic ancestry patterns and were assigned to groups including putative pure species, first-generation hybrids, and advanced backcrosses. Genotypes of the majority of hybrids were shifted towards P. mugo ancestry. Most outlier loci were shared across all sympatric populations, although some were specific to individual contact zones. The identified outliers were mainly associated with regulatory biological processes related to phosphorylation, proteolysis, and transmembrane transport. Signatures of local adaptation varied in different genetic classes in contact zones and they were strongest in pure P. sylvestris and hybrids with a majority of P. sylvestris ancestry. The pattern suggests that it may be driven by adaptation to peat bog habitats situated outside the species’ core ecological niche. CONCLUSIONS: Our findings indicate strong selective pressure acting on multiple genes in groups of hybrids and pure Pinus sylvestris individuals across all studied hybrid zones. In contrast, the weaker signal of selection observed in individuals with P. mugo ancestry suggests that relict populations of this species, which historically spread across postglacial peat bogs, were pre-adapted to such environments. While several outlier loci were shared across different contact zones, others were unique for one of them, indicating that local environmental pressures and adaptive introgression shape the genomic composition of the populations. These results highlight the role of hybridization in generating adaptive diversity and emphasize the evolutionary significance of hybrid zones in pines.

Hybridization, Genetic↗

PubMed2005

Adaptation of multilocus sequencing for studying variation within a major clone: evolutionary relationships of Salmonella enterica serovar Typhimurium.

Serovar Typhimurium of Salmonella enterica is a model organism for studies of pathogenesis that exhibits phage-type variation and variation in host range and virulence, but in a recent study showed no sequence variation in four genes, indicating the clonal nature of this serovar. We determined the relationships of 46 Typhimurium isolates of nine phage types using mutational changes detected either by matching AFLP (amplified fragment length polymorphism) fragments to computer-modeled LT2 AFLP fragments or by sequencing intergenic regions. Fifty-one polymorphic sites were detected, which gave a single phylogenetic tree. Comparison with genome sequences of five other serovars, Typhi, Paratyphi A, Gallinarum, Enteritidis, and Pullorum, enabled determination of the root of the tree. Only two parallel events were observed, giving high confidence in the tree branching order. The mutation-based tree provided a high level of consistency and a clear lineage for the Typhimurium isolates studied. This enabled us to show that for seven of the nine phage types used, the isolates studied have a single origin, but that two phage types clearly have more than one independent origin. We found that sequencing intergenic regions provides a good strategy for detection of mutational polymorphisms and study of phylogenetic relationships of closely related isolates and would be applicable to many other species.

Clone Cells↗

PubMed2006

No cancer in cancers: evolutionary trade-off between successful viviparity and tumor escape from the adaptive immune system.

Some invertebrate species including the king crab and king squid enjoy relatively long lives of up to 20 years. Nevertheless, there are few reports of malignancies among invertebrate animals while there are many such reports in lower vertebrates such as in fishes, amphibians, and reptiles. Viviparity is characteristic of most mammalian species, although it has been observed in both vertebrate and non-vertebrate species. As adaptive immune responses evolved among the cartilaginous fishes by virtue of gene duplication, all viviparous vertebrates cope with specific immune responses to reject the fetal allograft. The escape mechanisms employed by both human and animal malignancies share common properties, which are also employed by feto-placental units, such as the expression of non-classical major histocompatibility antigens (HLA-E, HLA-F, and HLA-G in humans), accumulation of regulatory T cells, Th2-directed immune responses, Fas/FasL- and/or PD-1/PD-L1-induced apoptosis, and the expression of indoleamine 2, 3 dioxygenase which starves the local tryptophan supply that is indispensable for an effective cytotoxic T cells response. In humans, a single cancer cell requires 1-10 years to develop into a clinically remarkable tumor. For cancer cells, the genes encoding the immunoregulatory mechanisms employed by feto-placental units could be of value for escaping the host immune system. Taken together, these observations support the author's hypothesis that the evolution of viviparity resulted in an evolutionary trade-off that may have increased susceptibility to malignancies.

Adaptation, Physiological↗

PubMed2005

Phylogenetics by likelihood: evolutionary modeling as a tool for understanding the genome.

Molecular evolutionary studies provide a means of investigating how cells function and how organisms adapt to their environment. The products of evolutionary studies provide medically important insights to the source of major diseases, such as HIV, and hold the key to understand the developing immunity of pathogenic bacteria to antibiotics. They have also helped mankind understand its place in nature, casting light on the selective forces and environmental conditions that resulted in modern humans. The use of likelihood as a framework for statistical modeling in phylogenetics has played a fundamental role in studying molecular evolution, enabling rigorous and robust conclusions to be drawn from sequence data. The first half of this article is a general introduction to the likelihood method for inferring phylogenies, the properties of the models used, and how it can be used for statistical testing. The latter half of the article focuses on the emerging new generation of phylogenetic models that describe heterogeneity in the evolutionary process along sequences, including the recoding of protein coding sequence data to amino acids and codons, and various approaches for describing dependencies between sites in a sequence. We conclude with a detailed case study examining how modern modeling approaches have been successfully employed to identify adaptive evolution in proteins.

Animals↗

PubMed1997

The role of immaturity in human development.

The possibility that infants' and young children's immature behaviors and cognitions are sometimes adaptive is explored and interpreted in terms of evolutionary theory. It is argued that developmental immaturity had an adaptive role in evolution and continues to have an adaptive role in human development. The role of developmental retardation in human evolution is discussed, followed by an examination of the relation between humans' extended childhood and brain plasticity. Behavioral neoteny, as exemplified by play, is examined, as are some potentially adaptive aspects of infants' perception and cognition that limit the amount of information they can process. Aspects of immature cognition during early childhood that may have some contemporaneous adaptive value are also discussed. It is proposed that viewing immaturity as sometimes adaptive to the developing child alters how children and their development are viewed.

Adaptation, Psychological↗

PubMed2006

Molecular adaptation during adaptive radiation in the Hawaiian endemic genus Schiedea.

BACKGROUND: "Explosive" adaptive radiations on islands remain one of the most puzzling evolutionary phenomena. The rate of phenotypic and ecological adaptations is extremely fast during such events, suggesting that many genes may be under fairly strong selection. However, no evidence for adaptation at the level of protein coding genes was found, so it has been suggested that selection may work mainly on regulatory elements. Here we report the first evidence that positive selection does operate at the level of protein coding genes during rapid adaptive radiations. We studied molecular adaptation in Hawaiian endemic plant genus Schiedea (Caryophyllaceae), which includes closely related species with a striking range of morphological and ecological forms, varying from rainforest vines to woody shrubs growing in desert-like conditions on cliffs. Given the remarkable difference in photosynthetic performance between Schiedea species from different habitats, we focused on the "photosynthetic" Rubisco enzyme, the efficiency of which is known to be a limiting step in plant photosynthesis. RESULTS: We demonstrate that the chloroplast rbcL gene, encoding the large subunit of Rubisco enzyme, evolved under strong positive selection in Schiedea. Adaptive amino acid changes occurred in functionally important regions of Rubisco that interact with Rubisco activase, a chaperone which promotes and maintains the catalytic activity of Rubisco. Interestingly, positive selection acting on the rbcL might have caused favorable cytotypes to spread across several Schiedea species. SIGNIFICANCE: We report the first evidence for adaptive changes at the DNA and protein sequence level that may have been associated with the evolution of photosynthetic performance and colonization of new habitats during a recent adaptive radiation in an island plant genus. This illustrates how small changes at the molecular level may change ecological species performance and helps us to understand the molecular bases of extremely fast rate of adaptation during island adaptive radiations.

Adaptation, Physiological↗

PubMed2026

Adaptive deletion of functional duplicate genes in Drosophila.

Gene deletion is traditionally viewed as a nonadaptive mechanism that eliminates functional redundancy, yet emerging evidence indicates that it disproportionately affects tissue-specific duplicates with unique functions. Here, we test whether gene deletion preferentially removes weakly constrained, degenerating duplicates or instead eliminates functionally active duplicates through an adaptive process. To identify the evolutionary and functional factors that determine which duplicates are lost, we systematically analyzed 100 gene deletion events in Drosophila by integrating sequence, expression, interaction, and structural data. We uncovered a strong bias toward the loss of younger child copies among functionally unique duplicates, whereas no such bias was observed for redundant duplicates. Contrary to expectations under relaxed constraint, deleted functionally unique genes evolve more slowly, show higher expression, engage in more protein-protein interactions, and do not exhibit elevated structural divergence or intrinsic disorder relative to redundant duplicates. When compared with single-copy genes, deleted functionally unique genes display similar evolutionary rates, slightly lower expression, greater network connectivity, comparable structural divergence, and lower intrinsic disorder. These patterns suggest that deletion frequently affects functionally active rather than degenerate genes. Collectively, our results support the hypothesis that gene deletion in Drosophila can represent an adaptive process acting on transiently functional duplicates, potentially driven by either genome streamlining or context-dependent deleterious effects.

evolution↗

PubMed2006

Geographic biotype and host-associated local adaptation in a polyphagous species, Lambdina fiscellaria (Lepidoptera: Geometridae) feeding on balsam fir on Anticosti Island, Canada.

The debate about mechanisms underlying the evolution of host specialization by herbivorous insects remains open. Natural selection may act locally and lead to different patterns of geographic variation in life history traits of polyphagous herbivores. The hypothesis of genetically-based trade-offs in offspring performance on different hosts has been proposed but this has rarely been demonstrated. Under laboratory conditions, the biological performance of two populations of the hemlock looper Lambdina fiscellaria (Guenée), a highly polyphagous lepidopteran, was compared when reared on three different tree host species: balsam fir, eastern hemlock and sugar maple. One population originated from Anticosti Island, Québec, Canada, where the insect has evolved without having access to two of the three tree species tested, the other being from the mainland where all tree species are present. When reared on balsam fir foliage, which was naturally available to each population, larvae from Anticosti Island underwent four instars compared with five for the mainland population, indicating the existence of geographic biotypes in L. fiscellaria. When reared on the foliage of non-naturally available host trees, larvae from Anticosti Island had a higher incidence of supernumerary instars. This is a unique example where local adaptation to environmental conditions of an insect herbivore is expressed through a differential number of larval instars. Moreover, the Anticosti Island population showed a higher growth related index on the host available to both populations indicating that a fitness trade-off was the evolutionary process underlying the local adaptation of this population on balsam fir.

Abies↗

PubMed2006

The evolutionary neuroscience of tool making.

The appearance of the first intentionally modified stone tools over 2.5 million years ago marked a watershed in human evolutionary history, expanding the human adaptive niche and initiating a trend of technological elaboration that continues to the present day. However, the cognitive foundations of this behavioral revolution remain controversial, as do its implications for the nature and evolution of modern human technological abilities. Here we shed new light on the neural and evolutionary foundations of human tool making skill by presenting functional brain imaging data from six inexperienced subjects learning to make stone tools of the kind found in the earliest archaeological record. Functional imaging of this complex, naturalistic task was accomplished through positron emission tomography with the slowly decaying radiological tracer (18)flouro-2-deoxyglucose. Results show that simple stone tool making is supported by a mosaic of primitive and derived parietofrontal perceptual-motor systems, including recently identified human specializations for representation of the central visual field and perception of three-dimensional form from motion. In the naïve tool makers reported here, no activation was observed in prefrontal executive cortices associated with strategic action planning or in inferior parietal cortex thought to play a role in the representation of everyday tool use skills. We conclude that uniquely human capacities for sensorimotor adaptation and affordance perception, rather than abstract conceptualization and planning, were central factors in the initial stages of human technological evolution.

Adaptation, Psychological↗

PubMed2026

Co-occurrence of biofilm formation, acid tolerance, and antibiotic resistance in environmental Escherichia coli associated with lettuce.

BACKGROUND: Environmental niches represent important reservoirs of Escherichia coli with stress-adaptation traits that support persistence outside the host. Contaminated irrigation water and soils can facilitate transfer to fresh produce, where bacterial survival may reduce the effectiveness of downstream control measures. This study investigated the co-occurrence of biofilm formation, acid tolerance, and antibiotic resistance (AR) in environmental E. coli and their contribution to persistence along the farm-to-produce continuum. RESULTS: Eighteen E. coli isolates recovered from irrigation water, soil, and lettuce were characterized using phenotypic assays and genome-based analyses. Most isolates remained susceptible to the majority of tested antibiotics, with multidrug resistance observed in only 11.1% of isolates. In contrast, moderate-to-strong biofilm formation was widespread (83.3%), and several isolates exhibited reduced susceptibility to acetic acid at concentrations relevant to household washing practices. Genotypic screening revealed a broad distribution of adhesion, iron acquisition, biofilm-associated, and plasmid-borne resistance determinants, indicating substantial functional diversity. Significant positive associations were observed between acid tolerance, biofilm formation, and antibiotic resistance, suggesting co-occurrence of stress-adaptation phenotypes rather than definitive evolutionary convergence. While antibiotic resistance phenotypes showed strong concordance with corresponding resistance genes, biofilm formation and acid tolerance were not associated with specific genetic determinants, supporting a multifactorial basis of these traits. CONCLUSIONS: These findings demonstrate that environmental E. coli can combine multiple stress-adaptation mechanisms that enhance persistence across agricultural and food-associated environments, even in the absence of high-risk resistance profiles. The observed co-occurrence of phenotypic traits highlights the potential for co-selection under environmental pressures and underscores the limitations of relying solely on downstream decontamination strategies. Effective risk mitigation requires integrated, preventive approaches targeting pre-harvest contamination and environmental reservoirs.

Biofilms↗

PubMed2002

Preliminary observations on specific adaptations of exophilic ixodid ticks to forests or open country habitats.

Some features of three-host exophilic ticks important for their survival differ at the generic level in relation to the types of their habitat. Ixodes and Haemaphysalis are typical forest genera. Hyalomma is an open country genus, whereas Dermacentor and Rhipicephalus, having some features of forest ticks, are closer to the ticks of open country. Forest ticks encounter rather stable and favorable temperature, humidity and illumination conditions as compared with open country ticks. A few differences determining every-day survival, hostseeking. and reproduction of ticks are considered. (1) Tolerance to desiccation is very low in forest ticks and much greater in ticks of open country. (2) Lack of eyes in forest ticks (having, however, epithelial photoreceptor cells) and formation of eyes as special morphological structures in ticks of open country. (3) Capability of mating and insemination of unfed specimens both on and off hosts in forest ticks (Ixodes) and insemination of partially engorged females only on hosts by fed males in open country ticks. (4) Reciprocal sexual dimorphism where in forest ticks females have a larger body than males and in open country ticks this correlation is opposite. (5) Linear dependence between female weight and number of eggs laid is established in forest ticks after the female weight becomes higher than 50% of mean engorgement weight whereas in open country ticks linear dependence begins to reveal itself much earlier. (6) In forest ticks the compensatory growth occurs only during adult feeding whereas in open country ticks such a growth occurs both during nymphal and adult feeding. The adaptive nature of the above differences and their evolutionary trends have been hypothesized.

Adaptation, Biological↗