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Results for “Evolutionary adaptability”

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PubMed2004

Refining learning and memory assessment in laboratory rodents. An ethological perspective.

In neuroscientific research, the importance of a multi-level approach in studying behaviour, ranging from the molecular to the behavioural level, has been increasingly recognised. In fact, behaviour represents the ultimate output of the brain, and behavioural phenotyping may provide functional information that may not be detectable using molecular, cellular, or histological evaluations. To correctly exploit the study of behaviour in the field of neuroscience, the principles and strategies of ethology must be carefully considered, so as to design appropriate experiments and accurately interpret data. In particular, ethological-type scoring, which entails both the close observation of the studied behaviour and the taking into account of its possible evolutionary history and adaptive significance, can contribute to standardising experimental protocols, so as to improve the quality of data and the welfare of the experimental animal.

Animals↗

PubMed2005

Origin and rapid diversification of a tropical moss.

Molecular sequences rarely evolve at a constant rate. Yet, even in instances where a clock can be assumed or approximated for a particular set of sequences, fossils or clear patterns of vicariance are rarely available to calibrate the clock. Thus, obtaining absolute timing for diversification of natural lineages can prove difficult. Unfortunately, without absolute time we cannot develop a complete understanding of important evolutionary processes, including adaptive radiations and key innovations. In the present study, the coding sequence of the nuclear gene, glyceraldehyde 3-phosphate dehydrogenase (gpd), extracted from the paleotropical moss, Mitthyridium, was found to exhibit clocklike behavior and used to reconstruct the history of 80 distinct molecular lineages that cover the full geographic range of Mitthyridium. Two separate clades endemic to two geographically distinct oceanic archipelagos were revealed by this phylogenetic analysis. This allowed the use of island age (as derived from potassium-argon dating) as a maximum age of origin of each monophyletic group, providing two independent time anchors for the clock found in gpd, the final piece needed to study absolute time. Based on results from both maximum age calibrations, which separately yielded highly consistent estimates, the ancestor of this moss group arose approximately 8 million years ago, and then diversified at the rapid rate of 0.56 +/- 0.004 new lineages per million years. Such a rate is on par with the highest diversification rates reported in the literature including rapidly radiating insular groups like the Hawaiian silversword alliance, a classic example of an adaptive radiation. Using independent sources of data, it was found that neither the age nor diversification estimates were affected by the use of molecular lineages rather than species as the operational taxonomic units. Identifying the cause for this rapid diversification requires further testing, but it appears to be related to a general shift in reproductive strategy from sexual to asexual, which may be a key innovation for this young group.

Asia, Southeastern↗

PubMed2006

Minimal selfing, few clones, and no among-host genetic structure in a hermaphroditic parasite with asexual larval propagation.

Little is known about actual mating systems in natural populations of parasites or about what constitutes the limits of a parasite deme. These parameters are interesting because they affect levels of genetic diversity, opportunities for local adaptation, and other evolutionary processes. We expect that transmission dynamics and the distribution of parasites among hosts should have a large effect on mating systems and demic structure, but currently we have mostly speculation and very few data. For example, infrapopulations (all the parasites in a single host) should behave as demes if parasite offspring are transmitted as a clump from host to host over several generations. However, if offspring are well mixed, then the parasite component population (all the parasites among a host population) would function as the deme. Similarly, low mean intensities or a high proportion of worms in single infections should increase the selfing rate. For species having an asexual amplification stage, transmission between intermediate and definitive (final) hosts will control the variance in clonal reproductive success, which in turn could have a large influence on effective sizes and rates of inbreeding. We examined demic structure, selfing rates, and the variance in clonal reproductive success in natural populations of Plagioporus shawi, a hermaphroditic trematode that parasitizes salmon. Overall levels of genetic diversity were very high. An a posteriori inference of population structure overwhelmingly supports the component population as the deme, rather than individual infrapopulations. Only a single pair of 597 adult individuals was identified as clones. Thus, the variance in clonal reproductive success was almost zero. Despite being hermaphroditic, P. shawi appears to be almost entirely outcrossing. Genetic estimates of selfing (<5%) were in accordance with the proportion of parasites from single infections. Thus, it appears that individual flukes outcross whenever possible and only resort to selfing when alone. Finally, our data support the hypothesis that aquatic transmission and the use of several intermediate hosts promotes high genetic diversity and well-mixed infrapopulations.

Animals↗

PubMed2006

[Perception independent of interest: a contribution to the relationship between people and animals].

In occidental cultures the relation of humans to animals is determined by the human perception of the outer world. Using motives from evolutionary epistemology it is argued that the evolutionary pressure to adapt increasingly obscures perception, where perception means relating to the outer world in a way that is independent of interests. Therefore, the pressure to adapt and to realise the interest to adapt obscures perception. This results in a reduced self-perception. Two phenomena exemplify this: persons ignoring their own bodies and a reductive perception relating to animals, such as reducing the value of animals to mere human resources. This reductive perception explains the very limited success of the animal rights-debate.

Animal Testing Alternatives↗

PubMed1986

Limits to exercise performance: some ideas from comparative studies.

Examples of exercise performance and metabolic scope in non-human mammalian species are considered from the point of view of problems and questions which may provide insights into evolutionary processes influencing adaptations to muscular activity. Consideration of both aerobic and anaerobic performance is required. Some recent approaches, notably that concerned with the concept of symmorphosis, the integration of design for the accommodation of variations in activity, show promise of new ways for comparative investigations of the adjustments to exercise.

Aerobiosis↗

PubMed1986

[Recording, with piezoelectric sensors, of the activity of the contractile elements in vivo in experimental acute and chronic aortic stenosis].

Mechanic alterations of the left ventricular wall due to an increasing afterload by means of experimentally provoked acute and chronic aortic stenosis, registered by piezoelectric sensors sutured on the surface of the ventricle, are analyzed. Tension or force developed in the ventricular wall or the acceleration of the shortening velocity of the contractile element, under these conditions, show in the piezoelectric sensor curve a new characteristic contractile state depending on the rapidity and time elapsed since the aortic stenosis, making clear the diagnosis, systolic peaks and their evolutionary stage. Different adaptation mechanisms employed by the myocardium, according to the rapidity of the experimental stenosis, showed by means of the variations of the different phases of the cardiac cycle depicted by sensor curves, are also described.

Animals↗

PubMedDate not supplied

Ethological models in research into the neural mechanisms of short-term memory.

Rats are protected against intake of toxic diets by specific evolutionary prepared behavioral adaptations. Intake of potentially dangerous novel food is reduced by neophobia. The taste signal is stored for several hours in a short-term memory file from which it gradually emerges in form of a permanent gustatory engram labeled as safe, when there are no adverse effects of feeding, or as aversive, when visceral symptoms of poisoning appear in the critical post-ingestion interval. The experimental evidence reviewed indicates that positive labeling (manifested by attenuation of neophobia) requires intact higher brain functions whereas the aversive experience (manifested by conditioned taste aversion) is recorded even under deep coma. The biological significance of the different neural mechanisms underlying the above forms of gustatory-visceral associations is discussed.

Animals↗

PubMedDate not supplied

[The sociality syndrome. A comparative study of the behavior of gerbils].

To explain the evolution of sociality the authors propose the hypothesis that every social interaction is based on the contest. The synergetic nature of any interaction determines the permanent involving partners in the contests and leads to increasing social pressure within community. The contestants' interactions inhibit an activity in one of the partners. Two possible evolutionary strategies of adaptation to increasing social density are: 1) an increase in resistance to the activity inhibition; 2) a retaining in memory the results of inhibition, i.e. reducing of ability to restore inhibited activity. Three species of gerbils (Gerbillidae): Mongolian (Meriones unguiculatus), Libyan (M. libycus), and midday gerbil (M. meridianus) were compared. Being similar in their ecology and behavioural repertoire three species differ strongly in extent of sociality: the highest in Mongolian gerbil and the lowest in midday one. The duration of social acts in laboratory groups of gerbils as well as frequency of acts delaying conflicts under natural conditions were assumed to correlate with increase in resistance to social pressure. Both parameters were higher in mongolian and libyan gerbils. The data on dynamics, asymmetry, and stability of social relations indicates more stable retaining in memory the results of interactions in Mongolian and Libyan gerbils than in midday ones but the latter restore inhibited activity more quickly. In the laboratory groups where the available space is compressed the midday gerbils maintain population at a level not lower than Mongolian ones and much higher than M. libycus. Moreover aggression within the group of midday gerbils doesn't result in rapid population decrease as in other two species.

Agonistic Behavior↗

PubMedDate not supplied

Menopause: an evolutionary perspective.

Evolutionary biologists classify theories of menopause as either: 1) adaptive, suggesting that female reproductive cessation results from its selective advantage, in that the increased risk of personal reproduction late in life makes it biologically more advantageous to rechannel reproductive energy into helping existing descendents, or 2) nonadaptive, indicating menopause is an artifact of the relatively recent dramatic increase in human longevity. With the possible exception of pilot whales, no mammals studied to date are known to commonly exhibit reproductive cessation in nature. To demonstrate adaptive menopause, one would need to establish both that the longevity of preagricultural humans commonly allowed them to exhibit menopause, and that postreproductive females could assist their descendents sufficiently to compensate for the loss of personal reproduction. The data on longevity of preagricultural humans with respect to the adaptive menopause hypothesis are mixed. Evolutionary models evaluated with data from modern hunting-gathering or agricultural humans fail to find that humans can assist their descendents sufficiently to offset the evolutionary cost of ceasing reproduction. However, assuming the human body has been physiologically adapted to the conditions extant during the vast majority of human history, it may be well worth pursuing how the signs and symptoms of menopause are affected by dietary, exercise, and reproductive hormone regimes mimicking those of the late Paleolithic era.

Animals↗

PubMed2003

Adaptation in the env gene of HIV-1 and evolutionary theories of disease progression.

The exact mechanisms by which HIV overwhelms the immune system remain poorly understood. Among the several explanations of HIV disease progression, most include adaptation of the viral genome to the host environment as a causal factor. Therefore, quantifying the rate and pattern of adaptive evolution within infected patients is critical to understanding the development of AIDS. Using sequence data from infected individuals sampled at multiple time points, I estimate the within-host adaptation rate of the HIV-1 env gene for viral populations from 50 different patients. I find that, averaging across patients, one adaptive substitution occurs every 3.3 months. Also, one adaptive mutation is driven to a high frequency (>50% but <100%) every 2.5 months. Taken together, such adaptive events occur once every 25 viral generations, which is the fastest adaptation rate ever recorded for a single protein-coding gene. Within the entire env gene, I estimate that a majority ( approximately 55%) of both nonsynonymous substitutions and high-frequency polymorphisms are adaptive. Further, in the C2-V5 region of env, I find that patients with longer asymptomatic periods have virus populations with higher adaptation rates, corroborating the notion that a broad, strong immune response against epitopes in the env gene product leads to longer asymptomatic periods. I conclude by discussing the distribution of nonsynonymous changes over the env gene.

Adult↗

PubMed2005

Physics and evolution of thermophilic adaptation.

Analysis of structures and sequences of several hyperthermostable proteins from various sources reveals two major physical mechanisms of their thermostabilization. The first mechanism is "structure-based," whereby some hyperthermostable proteins are significantly more compact than their mesophilic homologues, while no particular interaction type appears to cause stabilization; rather, a sheer number of interactions is responsible for thermostability. Other hyperthermostable proteins employ an alternative, "sequence-based" mechanism of their thermal stabilization. They do not show pronounced structural differences from mesophilic homologues. Rather, a small number of apparently strong interactions is responsible for high thermal stability of these proteins. High-throughput comparative analysis of structures and complete genomes of several hyperthermophilic archaea and bacteria revealed that organisms develop diverse strategies of thermophilic adaptation by using, to a varying degree, two fundamental physical mechanisms of thermostability. The choice of a particular strategy depends on the evolutionary history of an organism. Proteins from organisms that originated in an extreme environment, such as hyperthermophilic archaea (Pyrococcus furiosus), are significantly more compact and more hydrophobic than their mesophilic counterparts. Alternatively, organisms that evolved as mesophiles but later recolonized a hot environment (Thermotoga maritima) relied in their evolutionary strategy of thermophilic adaptation on "sequence-based" mechanism of thermostability. We propose an evolutionary explanation of these differences based on physical concepts of protein designability.

Acclimatization↗

PubMed2001

The basic depression ratio of the host: the evolution of host resistance to microparasites.

The basic reproduction ratio R0 occupies a central position in the theory of host pathogen interactions. However, this quantity stresses the role of the pathogen. This paper proposes an additional, more host-centred char acterization using the basic depression ratio D0. This quantity is the number of host individuals per infected by which the infected host population is depressed below its uninfected level. This paper shows that a baseline criterion for the evolution of host resistance to microparasites is that resistance evolves to minimize D0. This parallels the result for pathogen virulence where R0 is maximized. The tension between these two criteria is noted. The framework established allows a discussion of trade-offs between aspects of the pathogen-free host biology and the host pathogen interaction. For certain linear and convex trade-offs it is shown that the strain with the lowest transmission parameter beta wins (despite the fact that it has the lowest intrinsic birth rate a). For corresponding concave trade-offs, either the strain with minimum beta and a or the strain with maximum beta and a wins. Finally the connection with the techniques of adaptive dynamics is made. Evolutionary singular points are shown to occur at extrema of D0. The evolutionary attainment of the results is discussed.

Adaptation, Physiological↗

PubMed1978

Atypical Yersinia enterocolitica: clinical and epidemiological parameters.

Infections due to biochemically typical Yersinia enterocolitica usually present as gastroenteritis, mesenteric lymphadenitis, terminal ileitis, and septicemia often with visceral abscesses. In these instances, the isolates have been biochemically typical and of well-established serotypes, namely 0:3 or 0:9 and, in the United States, 0:5 or 0:8. The recovery, recognition, and significance of biochemically and serologically atypical Y. enterocolitica in human infections has proceeded more slowly. From an analysis of the clinical histories of 20 patients infected with 21 such aberrant Y. enterocolitica, it appears that these strains are of restricted pathogenic potential, producing various clinical entities such as localized skin abscesses, conjunctivitis, self-limiting enteritis, and wound and urinary tract infections in hosts with predisposing factors. Epidemiologically, whereas episodic acquisition of atypical strains by hospitalized patients is indicative of nosocomial transmission, in the present series sporadic isolations over a 4-year period, mainly from ambulatory patients, suggest an occult reservoir in the community serviced by The Mount Sinai Hospital. In contrast to typical Y. enterocolitica, which has become well adapted in animal and human hosts, it appears that environmental strains may be in the evolutionary process of becoming adapted to humans.

Abscess↗

PubMed1995

Psychological sex differences. Origins through sexual selection.

Men and women clearly differ in some psychological domains. A. H. Eagly (1995) shows that these differences are not artifactual or unstable. Ideally, the next scientific step is to develop a cogent explanatory framework for understanding why the sexes differ in some psychological domains and not in others and for generating accurate predictions about sex differences as yet undiscovered. This article offers a brief outline of an explanatory framework for psychological sex differences--one that is anchored in the new theoretical paradigm of evolutionary psychology. Men and women differ, in this view, in domains in which they have faced different adaptive problems over human evolutionary history. In all other domains, the sexes are predicted to be psychologically similar. Evolutionary psychology jettisons the false dichotomy between biology and environment and provides a powerful metatheory of why sex differences exist, where they exist, and in what contexts they are expressed (D. M. Buss, 1995).

Adaptation, Psychological↗

PubMed1999

Proximate and evolutionary studies of anxiety, stress and depression: synergy at the interface.

While enormous progress has been made in unraveling the proximate physiological mechanisms that account for anxiety, stress, and low mood, these states continue to give rise to considerable conceptual confusion. This is, in part, because proximate studies have neither been adequately distinguished from, nor integrated with, evolutionary explanations for the adaptive functions of anxiety, stress, and mood. A complete biological explanation that incorporates both proximate and evolutionary explanations will be of great value to better define the border between normal and pathological, to help to explain why pathological anxiety and depression are so common, and to provide a much-needed basis for sensible decisions about when different pharmacological manipulations are likely to be helpful or harmful. Ideally, evolutionary considerations should provide a conceptual framework within which the biological significance of the proximate mechanisms can be better understood, and the proximate findings should provide tests of evolutionary hypotheses. Studies at the interface between evolutionary and proximate explanations will be difficult, but important to better understand individual differences in vulnerability and the etiology of diseases that result from dysregulation of anxiety and mood.

Animals↗

PubMed2003

The influence of cellular physiology on the initiation of mutational pathways in Escherichia coli populations.

The factors affecting the direction of evolutionary pathways and the reproducibility of adaptive responses were investigated under closely related but non-identical conditions. Replicate chemostat cultures of Escherichia coli were compared when adapting to partial or severe glucose limitation. Four independent populations used a reproducible sequence of early mutational changes under both conditions, with rpoS mutations always occurring first before mgl. However, there were interesting differences in the timing of mutational sweeps: rpoS mutations appeared in a clock-like fashion under both partial and severe glucose limitation, while mgl sweeps arose under both conditions but at different times. Interestingly, malT and mlc mutations appeared only under severe limitation. Even though the ancestors were genotypically identical, the semi-differentiated properties of bacteria growing with mild or severe glucose limitation sent the populations in characteristic directions. Mutation supply and the fitness contribution of mutations were estimated and demonstrated to be potential influences in the choice of particular adaptation pathways under severe and mild glucose limitation. Predicting all the mutations fixed in adapting populations is beyond our current understanding of evolutionary processes, but the interplay between ancestor physiology and the initiation of adaptation pathways is demonstrated and definable in bacterial populations.

Adaptation, Physiological↗

PubMed2015

Evolutionary genomics of Culex pipiens: global and local adaptations associated with climate, life-history traits and anthropogenic factors.

We present the first genome-wide study of recent evolution in Culex pipiens species complex focusing on the genomic extent, functional targets and likely causes of global and local adaptations. We resequenced pooled samples of six populations of C. pipiens and two populations of the outgroup Culex torrentium. We used principal component analysis to systematically study differential natural selection across populations and developed a phylogenetic scanning method to analyse admixture without haplotype data. We found evidence for the prominent role of geographical distribution in shaping population structure and specifying patterns of genomic selection. Multiple adaptive events, involving genes implicated with autogeny, diapause and insecticide resistance were limited to specific populations. We estimate that about 5-20% of the genes (including several histone genes) and almost half of the annotated pathways were undergoing selective sweeps in each population. The high occurrence of sweeps in non-genic regions and in chromatin remodelling genes indicated the adaptive importance of gene expression changes. We hypothesize that global adaptive processes in the C. pipiens complex are potentially associated with South to North range expansion, requiring adjustments in chromatin conformation. Strong local signature of adaptation and emergence of hybrid bridge vectors necessitate genomic assessment of populations before specifying control agents.

Adaptation, Biological↗

PubMed1993

Evolutionary origin and radiation of the avian-adapted non-motile salmonellae.

Multilocus enzyme electrophoresis was employed to estimate chromosomal genotypic diversity and relationships among 131 isolates of the non-motile Salmonella biotypes Gallinarum and Pullorum (serotype 1, 9, 12:-:-) that cause fowl typhoid and pullorum disease, respectively. Thirteen electrophoretic types (ETs), marking clones, were distinguished, and construction of a neighbour-joining phylogenetic tree revealed three lineages: one consisted of five ETs of Gallinarum, a second included seven ETs of Pullorum, and a third was represented by a single ET (Ga/Pu 1) that is intermediate between those of the other two lineages in both multilocus enzyme genotype and biochemical properties. Enzyme genotype analysis and comparative nucleotide sequencing of the phase 1 flagellin gene (fliC), the hook-associated protein 1 gene (flgK), and the 6-phosphogluconate dehydrogenase gene (gnd) identified serotype Enteritidis (1, 9, 12:g, m:-) as a close relative of the non-motile salmonellae. In most strains of biotype Gallinarum, the fliC gene is complete, intact and identical in sequence to that of Enteritidis, but isolates of three ETs had a stop codon at position 495. The fliC sequences of the ETs of Pullorum differed from that of Enteritidis in having non-synonymous changes in either two or three codons and a synonymous change in one codon. The sharing of distinctive alleles at three metabolic enzyme loci and a stop codon in flgK indicates that the non-motile salmonellae are monophyletic and that their most recent common ancestor was non-motile. Since diverging from that ancestor, the Pullorum lineage has evolved more rapidly than the Gallinarum and Ga/Pu 1 lineages.

Animals↗