Non-adaptive Changes Research Articles

Natural selection and evolution: evolving concepts.

Many recent studies in evolutionary biology have expanded and refined definitions of biological evolution and natural selection. Current evolutionary models incorporate different adaptive and non-adaptive processes based on molecular genetic changes and how DNA is modified over time in unicellular species, or in germline versus somatic cells in metazoan species. Cogent arguments can be raised for the view that natural selection should be considered a biological law, consistent with quantitative mathematical equations that describe the fitness of individuals, as well as variations within and among populations. Evolution is an overarching framework that incorporates the laws of natural selection and clarifies why phenotypic variation can increase in prevalence and result in species adaptations. The conceptual framework for biological evolution incorporates many cohesive principles that collectively have a predictive value. This framework will continue to evolve with improvements in high-resolution technologies that enable us to examine both adaptive and non-adaptive changes that drive biological phenotypes.

Therapeutic doses of ketamine acutely attenuate the aversive effect of losses during decision-making.

The discovery of rapid-acting antidepressant, ketamine has opened a pathway to a new generation of treatments for depression, and inspired neuroscientific investigation based on a new perspective that non-adaptive changes in the intrinsic excitatory and inhibitory circuitry might underlie the pathophysiology of depression. Nevertheless, it still remains largely unknown how the hypothesized molecular and synaptic levels of changes in the circuitry might mediate behavioral and neuropsychological changes underlying depression, and how ketamine might restore adaptive behavior. Here, we used computational models to analyze behavioral changes induced by therapeutic doses of ketamine, while rhesus macaques were iteratively making decisions based on gains and losses of tokens. When administered intramuscularly or intranasally, ketamine reduced the aversiveness of undesirable outcomes such as losses of tokens without significantly affecting the evaluation of gains, behavioral perseveration, motivation, and other cognitive aspects of learning such as temporal credit assignment and time scales of choice and outcome memory. Ketamine's potentially antidepressant effect was separable from other side effects such as fixation errors, which unlike outcome evaluation, was readily countered with strong motivation to avoid errors. We discuss how the acute effect of ketamine to reduce the initial impact of negative events could potentially mediate longer-term antidepressant effects through mitigating the cumulative effect of those events produced by slowly decaying memory, and how the disruption-resistant affective memory might pose challenges in treating depression. Our study also invites future investigations on ketamine's antidepressant action over diverse mood states and with affective events exerting their impacts at diverse time scales.

Therapeutic doses of ketamine acutely attenuate the aversive effect of losses during decision-making

The discovery of rapid-acting antidepressant, ketamine has opened a pathway to a new generation of treatments for depression, and inspired neuroscientific investigation based on a new perspective that non-adaptive changes in the intrinsic excitatory and inhibitory circuitry might underlie the pathophysiology of depression. Nevertheless, it still remains largely unknown how the hypothesized molecular and synaptic levels of changes in the circuitry might mediate behavioral and neuropsychological changes underlying depression, and how ketamine might restore adaptive behavior. Here, we used computational models to analyze behavioral changes induced by therapeutic doses of ketamine, while rhesus macaques were iteratively making decisions based on gains and losses of tokens. When administered intramuscularly or intranasally, ketamine reduced the aversiveness of undesirable outcomes such as losses of tokens without significantly affecting the evaluation of gains, behavioral perseveration, motivation, and other cognitive aspects of learning such as temporal credit assignment and time scales of choice and outcome memory. Ketamine’s potentially antidepressant effect was separable from other side effects such as fixation errors, which unlike outcome evaluation, was readily countered with strong motivation to avoid errors. We discuss how the acute effect of ketamine to reduce the initial impact of negative events could potentially mediate longer-term antidepressant effects through mitigating the cumulative effect of those events produced by slowly decaying memory, and how the disruption-resistant affective memory might pose challenges in treating depression. Our study also invites future investigations on ketamine’s antidepressant action over diverse mood states and with affective events exerting their impacts at diverse time scales.

Monitoring of asthenic disorders in patients with psychoneurological pathology

24 healthy adults as well as 69 patients with asthenic manifestations (43 patients with chronic ischemia of brain and 26 patients with different types of multiple sclerosis) were examined with using of an original computer modification of tapping. The results of the study showed that parameters of serial motor reactions and their relationship in healthy adults were indicated the stability of the brain functional state and significant influence of cortex regulatory systems on its dynamics according to tasks that are performed. Examination materials of patients indicated the significant reduction of ability of cortex regulatory influences on subcortical non-specific systems under load conditions, reduction of level of interhemispheric interaction as well as availability of non-adaptive changes with reduction of functional state of different types in dynamics of examination. These manifestations were correlated with clinical symptoms severity. The proposed option of tapping has shown its ability to determine of common features and differences of asthenic syndrome in patients with chronic ischemia and multiple sclerosis in connection with the development of pathological conditions and processes of its compensation. This is very important especially in the early stages of the disease and may be used for assessment of the effectiveness of therapy. Key words: chronic ischemia, multiple sclerosis, asthenic manifestations, functional state of brain, tapping

Non-adaptive evolution in codon usage of human-origin monkeypox virus

Monkeypox virus (Mpox) is a zoonotic infectious disease that threatens human and animal health, with a global outbreak of the low-pathogenic Mpox beginning from 2022. In this study, we analyzed the codon usage of Mpox between two clades, Clade-I and Clade-IIb-B, to understand changes in host adaptation. Clade-IIb-B of the Mpox genome underwent non-adaptive evolution making it less adapted to its host than Clade-I. The analysis of individual genes revealed that 48 genes exhibited non-adaptive mutation, while 38 genes underwent adaptive mutations. Genes involved in replication, transcription, and host-modulation exhibited a mix of adaptive and non-adaptive evolutionary patterns. This study also found that the mutations of Mpox led to changes in non-adaptative genes in different organs. Additionally, we found that codon usage of Mpox was less similar to that of up-regulated host genes and more similar to that of down-regulated host genes post-infection, indicating that codon usage affects host gene expression. Overall, the study highlights the non-adaptive changes in codon usage as a potential cause of differences in Mpox virulence and provides insights into the evolutionary and adaptive mechanisms of Mpox and its potential impact on pathogenicity and host adaptation.

Genotypic variation in phenological plasticity: Reciprocal common gardens reveal adaptive responses to warmer springs but not to fall frost.

Species faced with rapidly shifting environments must be able to move, adapt, or acclimate in order to survive. One mechanism to meet this challenge is phenotypic plasticity: altering phenotype in response to environmental change. Here, we investigated the magnitude, direction, and consequences of changes in two key phenology traits (fall bud set and spring bud flush) in a widespread riparian tree species, Populus fremontii. Using replicated genotypes from 16 populations from throughout the species' thermal range, and reciprocal common gardens at hot, warm, and cool sites, we identified four major findings: (a) There are significant genetic (G), environmental (E), and GxE components of variation for both traits across three common gardens; (b) The magnitude of phenotypic plasticity is correlated with provenance climate, where trees from hotter, southern populations exhibited up to four times greater plasticity compared to the northern, frost-adapted populations; (c) Phenological mismatches are correlated with higher mortality as the transfer distances between provenance and garden increase; and (d) The relationship between plasticity and survival depends not only on the magnitude and direction of environmental transfer, but also on the type of environmental stress (i.e., heat or freezing), and how particular traits have evolved in response to that stress. Trees transferred to warmer climates generally showed small to moderate shifts in an adaptive direction, a hopeful result for climate change. Trees experiencing cooler climates exhibited large, non-adaptive changes, suggesting smaller transfer distances for assisted migration. This study is especially important as it deconstructs trait responses to environmental cues that are rapidly changing (e.g., temperature and spring onset) and those that are fixed (photoperiod), and that vary across the species' range. Understanding the magnitude and adaptive nature of phenotypic plasticity of multiple traits responding to multiple environmental cues is key to guiding restoration management decisions as climate continues to change.

Different Evolutionary Paths to Complexity for Small and Large Populations of Digital Organisms.

A major aim of evolutionary biology is to explain the respective roles of adaptive versus non-adaptive changes in the evolution of complexity. While selection is certainly responsible for the spread and maintenance of complex phenotypes, this does not automatically imply that strong selection enhances the chance for the emergence of novel traits, that is, the origination of complexity. Population size is one parameter that alters the relative importance of adaptive and non-adaptive processes: as population size decreases, selection weakens and genetic drift grows in importance. Because of this relationship, many theories invoke a role for population size in the evolution of complexity. Such theories are difficult to test empirically because of the time required for the evolution of complexity in biological populations. Here, we used digital experimental evolution to test whether large or small asexual populations tend to evolve greater complexity. We find that both small and large—but not intermediate-sized—populations are favored to evolve larger genomes, which provides the opportunity for subsequent increases in phenotypic complexity. However, small and large populations followed different evolutionary paths towards these novel traits. Small populations evolved larger genomes by fixing slightly deleterious insertions, while large populations fixed rare beneficial insertions that increased genome size. These results demonstrate that genetic drift can lead to the evolution of complexity in small populations and that purifying selection is not powerful enough to prevent the evolution of complexity in large populations.

The Map and the Territory: Complexity in Biology

In business administration or in economics it is absolutely relevant not to consider indexes like profit growth rate or gross domestic product as exhaustive indexes for economic wealth. Likewise, in biology it is important not to confuse the representation of life with life itself. The most important concepts in biology are information, memory, structure, plasticity, and robustness. Information is the difference that makes the difference. Memories are information registered in an organism. Plasticity is the capacity of a living organism to change its own structure/sets of behaviors for having a competitive advantage. Robustness is the ability of a living organism to resist environmental changes without changing its own structure/sets of behavior, and fragility is when a living organism undergoes changes in its own structure without being able to resist non-adaptive changes.

Divergent Skull Morphology Supports Two Trophic Specializations in Otters (Lutrinae).

Variation in terrestrial mammalian skull morphology is known to constrain feeding performance, which in turn influences dietary habits and ultimately fitness. Among mustelids, otters have evolved two feeding specializations: underwater raptorial capture of prey (mouth-oriented) and capture of prey by hand (hand-oriented), both of which have likely associations with morphology and bite performance. However, feeding biomechanics and performance data for otters are sparse. The first goal of this study was to investigate the relationships between feeding morphology and bite performance among two mouth-oriented piscivores (Pteronura brasiliensis and Lontra canadensis) and two hand-oriented invertebrate specialists (Enhydra lutris and Aonyx cinerea). Since other vertebrate taxa that are mouth-oriented piscivores tend to possess longer skulls and mandibles, with jaws designed for increased velocity at the expense of biting capability, we hypothesized that mouth-oriented otters would also possess long, narrow skulls indicative of high velocity jaws. Conversely, hand-oriented otters were expected to possess short, blunt skulls with adaptations to increase bite force and crushing capability. Concomitant with these skull shapes we hypothesized that sea otters would possess a greater mandibular bluntness index, providing for a greater mechanical advantage compared to other otter species investigated. A second goal was to examine morphological variation at a finer scale by assessing variation in cranial morphology among three sea otter subspecies. Since diet varies among these subspecies, and their populations are isolated, we hypothesized that the magnitude of mandibular bluntness and concomitant mechanical advantage, as well as occlusal surface area would also vary within species according to their primary food source (fish versus hard invertebrates). Functional expectations were met for comparisons among and within species. Among species the phylogeny suggests a deeply rooted transition to alternative foraging types. Yet within foraging types alternative species were also strongly variable, suggesting either selective differences in the extent or nature of realized foraging mode, or an accumulation of non-adaptive changes during the long independent evolutionary history. At the finest scale, variation among subspecies indicates that trophic adaptation occurred rapidly, making it interesting that we happened to find both deeply and shallowly-rooted transformations associated with diet type in otter species and subspecies.

Functional plasticity of the visual system in multiple sclerosis.

OPINION article Front. Neurol., 08 April 2015Sec. Multiple Sclerosis and Neuroimmunology Volume 6 - 2015 | https://doi.org/10.3389/fneur.2015.00079

Anti-predatory behaviour of wild-caught vs captive-bred freshwater angelfish, Pterophyllum scalare

Summary Environments and experiences encountered in early life stages of animals shape their adult behaviour. When environments are maintained for several generations, differential selection forces act upon individuals to select those most fit to the particular conditions. As such, differences in the behaviour of captive bred and wild caught individuals have been observed recurrently. In fish, hatchery raised individuals tend to seek refuge less, making them more vulnerable to predators. We tested the hypothesis that captive breeding induces non-adaptive changes in behaviour of freshwater angelfish, Pterophyllum scalare. Wild-caught and captive-bred fish were exposed to a natural predator and measured for their anti-predator behaviours; no differences were found in behaviour under control conditions. When exposed to a natural predator, wild-caught fish exhibited significantly shorter freezing durations than captive-bred fish, and took significantly shorter time to resume normal behaviour. No differences in the time taken to initiate investigations of the predator were detected. The results demonstrate that captive-bred fish respond differently than their wild counterparts when exposed to a natural predator, and that this domestication has implications for captive rearing programmes.

The role of duplications in the evolution of genomes highlights the need for evolutionary-based approaches in comparative genomics

Understanding the evolutionary plasticity of the genome requires a global, comparative approach in which genetic events are considered both in a phylogenetic framework and with regard to population genetics and environmental variables. In the mechanisms that generate adaptive and non-adaptive changes in genomes, segmental duplications (duplication of individual genes or genomic regions) and polyploidization (whole genome duplications) are well-known driving forces. The probability of fixation and maintenance of duplicates depends on many variables, including population sizes and selection regimes experienced by the corresponding genes: a combination of stochastic and adaptive mechanisms has shaped all genomes. A survey of experimental work shows that the distinction made between fixation and maintenance of duplicates still needs to be conceptualized and mathematically modeled. Here we review the mechanisms that increase or decrease the probability of fixation or maintenance of duplicated genes, and examine the outcome of these events on the adaptation of the organisms.ReviewersThis article was reviewed by Dr. Etienne Joly, Dr. Lutz Walter and Dr. W. Ford Doolittle.

The strain concept in phytoplankton ecology

Laboratory cultures are important tools for investigating the biology of microalgae, allowing experimentation under controlled conditions. This control is critical for comparative studies, such as those often used to investigate intra-specific variation in properties of interest. By holding the environment constant, the experimentalist can gain insight into the genetic basis of phytoplankton phenotypes and by extension, into the adaptive history of those genotypes. In most cases the adaptations of interest are those that the algae have evolved in response to their natural environment. However, here it is argued that such experiments may instead reveal evolutionary adaptations to, and/or non-adaptive changes induced by, the culture conditions under which the alga is maintained. We present a review of the processes of evolution as they pertain to microalgal culture, and illustrate this discussion with examples of in-culture evolution from both within and outside the field of phycology. With these considerations in mind, recommendations are made for experimental practice focusing on comparative physiology, for which the effects of in-culture evolution are particularly confounding. Finally we argue that, although problematic in some contexts, the evolutionary propensities of phytoplankton cultures actually present an important opportunity for experimental evolutionary research with direct environmental significance.

Interruption of a basal ganglia-forebrain circuit prevents plasticity of learned vocalizations.

Birdsong, like speech, is a learned vocal behaviour that relies greatly on hearing; in both songbirds and humans the removal of auditory feedback by deafening leads to a gradual deterioration of adult vocal production. Here we investigate the neural mechanisms that contribute to the processing of auditory feedback during the maintenance of song in adult zebra finches. We show that the deleterious effects on song production that normally follow deafening can be prevented by a second insult to the nervous system--the lesion of a basal ganglia-forebrain circuit. The results suggest that the removal of auditory feedback leads to the generation of an instructive signal that actively drives non-adaptive changes in song; they also suggest that this instructive signal is generated within (or conveyed through) the basal ganglia-forebrain pathway. Our findings provide evidence that cortical-basal ganglia circuits may participate in the evaluation of sensory feedback during calibration of motor performance, and demonstrate that damage to such circuits can have little effect on previously learned behaviour while conspicuously disrupting the capacity to adaptively modify that behaviour.

Inbreeding effects on mating system traits for two species ofLupinus (Leguminosae)

The consequences of inbreeding for reproductive traits were investigated for two closely related annual lupines that differ in their mating system. Lupinus bicolor (Leguminosae) is a primarily selling species while Lupinus nanus outcrosses at intermediate rates. A controlled crossing program was used for each species to produce selfed and outcrossed progeny. These progeny were then grown in a greenhouse and scored for the date of first flower, flower morphology, and autofertility. Selfed progeny of L. bicolor produced significantly smaller flowers but did not differ from outcrossed progeny for the remaining traits. Selfed progeny of L. nanus produced flowers that significantly differed in shape and had fewer ovules than the flowers of outcrossed progeny. Selfed progeny of L. nanus also had significantly lower rates of autofertility in comparison to outcrossed progeny. The significant effects of inbreeding on these mating system traits may indicate the presence of directional dominance at the loci underlying these characters. The consequences of these direct effects of inbreeding on reproductive traits for plants growing in natural populations may include nonadaptive changes in the outcrossing rate between generations.

Age-dependent ventricular response to pressure overload

Success with the arterial switch operation for D-transposition of the great arteries and the concept of left ventricular suitability for systemic work stimulated this literature review of the age-dependent mechanisms in normal cardiac growth and pressure-induced left ventricular hypertrophy. Normal postnatal myocardial growth is markedly influenced by hemodynamic factors. It consists of an early hyperplastic phase of both myocytes and capillaries that is followed by a myocyte hypertrophic phase. Similarly, imposition of a pressure overload induces both myocyte hyperplasia/hypertrophy and increased angiogenesis in neonates, but only myocyte hypertrophy at a later age. The functional consequences of ventricular hypertrophy are the result of adaptive and nonadaptive changes resulting from the overload stimulus, for example, induction of protooncogene expression, myosin isoenzyme shifts, degree of coronary perfusion, responsiveness to beta-adrenergic stimulation, and myocyte capacity to re-accumulate or sequester cytosolic calcium. Strikingly, both the capacity and the rapidity of left ventricular hypertrophy decrease with increasing age. This experimental information supports the current use of primary arterial switching for neonates with D-transposition of the great arteries and the use of "rapid" two-stage arterial switching in infants more than 3 to 4 weeks of age; it raises some concern about the practice of late retraining of the left ventricle in cases of failed atrial inversion operation.

NONADAPTIVE EVOLUTION OF DISEASE RESISTANCE IN AN ANNUAL LEGUME.

Local populations of the plant Amphicarpaea bracteata often contain genetically divergent lineages that differ strongly in disease resistance toward the specialist pathogen Synchytrium decipiens. In one population, lineages with disease resistance were observed to significantly decrease in frequency over a two-year period, despite the continued presence of pathogens. Extensive self-pollination in A. bracteata restricts the opportunity for recombination of alleles affecting separate traits, resulting in strong correlations between disease resistance and other ecologically important characters, including plant morphology, phenology, and patterns of reproductive allocation. Natural selection on these correlated characters may thus cause nonadaptive changes in disease resistance. These results imply that A. bracteata's mating system is a basic constraint interfering with its adaptation to pathogen attack.

Environmental Effects on Fish Gill Morphology

Fish gill morphology and function are intricately related. Adjustments in gill morphology during adaptation of fish to environmental changes are often instrumental in conserving physiological functions. But optimization of one particular gill function by an environmentally induced morphological modification may be detrimental to other gill functions. Moreover, changes in gill morphology in response to a particular environment may not always be beneficial and indeed may contribute to the death of fish in polluted or acidified waters. In this paper we discuss both adaptive and nonadaptive changes in gill morphology when fish encounter changing environments. Emphasis is placed on recent findings concerning environmental oxygen, ionic composition, and xenobiotics. An assimilation of the results of these studies reveal a common response to widely different environmental disturbances (e.g., hyperoxia, hypercapnia, acidification, low [ NaCl], low [ Ca²⁺ ], freshwater-to-seawater transfer), namely branchial chloride cell proliferation. We suggest therefore that the chloride cell is multifunctional and plays a role in Ca²⁺ uptake, acid-base balance, NaCl uptake in freshwater fish, and NaCl excretion in seawater fish.

In vitro rearing of parasitoids: Role of host factors in nutrition

AbstractEvidence for the role of host components in the growth and development of parasitoids is briefly reviewed, and implications concerning the development of in vitro culture media are discussed. In vitro development of the entomophagous parasitoids Eucelatoria bryani Sabrosky (Diptera: Tachinidae) and Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) is dependent on low‐molecular‐weight host chemicals. Asparagine, but not aspartic acid, and several other free amino acids are essential dietary ingredients for E. bryani. From insect hemolymph, small, unidentified polar molecules with characteristics similar to sugars are needed for pupation of T. pretiosum. Both adaptive and nonadaptive changes likely are responsible for the dependence of parasitoids on host factors. The genetic changes have no apparent adverse effect unless the parasitoids are fed artificial media devoid of certain chemicals that are obtained in vivo from host insects. The rearing of at least several species of important entomophages to control pest insects of great economic importance is dependent on the identification of constituents from host insects and inclusion of these chemicals in artifical diets.

Adaptation in Pantothenate-Requiring Neurospora. II. Nuclear Competition During Adaptation

Davis, R. H. (U. Michigan, Ann Arbor.) Adaptation in pantothenate-requiring Neurospora. II. Nuclear competition during adaptation. Amer. Jour. Bot. 47(8) : 648–654. Illus. 1960.—The process of adaptation in pantothenate-requiring Neurospora was studied by the use of heterocaryons constituted of the pan-1 strain and a modified strain, pan-1 m, derived from it. Although pan-1-m homocaryons grow well on a pantothenate concentration on which pan-1 grows little or not at all, pan-1 nuclei often have a selective advantage in pan-1 + pan-1-m heterocaryons grown on the same medium. This results in non-adaptive changes in nuclear ratios and labile growth rates of the heterocaryons. Nuclear competition does not occur when pantothenate is not limiting to the growth of either homocaryon. The results are discussed, and related to past work on adaptation and nuclear ratio changes in Neurospora hetercaryons.