Fluctuating selection: the perpetual renewal of adaptation in variable environments

Darwin insisted that evolutionary change occurs very slowly over long periods of time, and this gradualist view was accepted by his supporters and incorporated into the infinitesimal model of quantitative genetics developed by R. A. Fisher and others. It dominated the first century of evolutionary biology, but has been challenged in more recent years both by field surveys demonstrating strong selection in natural populations and by quantitative trait loci and genomic studies, indicating that adaptation is often attributable to mutations in a few genes. The prevalence of strong selection seems inconsistent, however, with the high heritability often observed in natural populations, and with the claim that the amount of morphological change in contemporary and fossil lineages is independent of elapsed time. I argue that these discrepancies are resolved by realistic accounts of environmental and evolutionary changes. First, the physical and biotic environment varies on all time-scales, leading to an indefinite increase in environmental variance over time. Secondly, the intensity and direction of natural selection are also likely to fluctuate over time, leading to an indefinite increase in phenotypic variance in any given evolving lineage. Finally, detailed long-term studies of selection in natural populations demonstrate that selection often changes in direction. I conclude that the traditional gradualist scheme of weak selection acting on polygenic variation should be supplemented by the view that adaptation is often based on oligogenic variation exposed to commonplace, strong, fluctuating natural selection.

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DEVELOPMENTAL STABILITY OF DROSOPHILA MELANOGASTER UNDER ARTIFICIAL AND NATURAL SELECTION IN CONSTANT AND FLUCTUATING ENVIRONMENTS

Genetics ◽

10.1093/genetics/95.4.1033 ◽

1980 ◽

Vol 95 (4) ◽

pp. 1033-1042

Author(s):

Brian P Bradley

Keyword(s):

Drosophila Melanogaster ◽

Natural Selection ◽

Developmental Stability ◽

Stabilizing Selection ◽

Phenotypic Variance ◽

Environment Interaction ◽

Total Phenotypic Variance ◽

Environmental Variance ◽

Genotype Environment Interaction ◽

Fluctuating Environments

ABSTRACT Populations of Drosophila melanogaster in constant 25λ and fluctuating 20/29λ environments showed increases in developmental stability, indicated by decreases in bilateral asymmetry of sterno-pleural chaeta number. In both environments, rates of decrease in asymmetry were greater under natural selection (control lines) than under artificial stabilizing selection. Overall mean asymmetry was greater in the fluctuating environment.—There was no evidence that decreased asymmetry was due to heterozygosity, and the decline in asymmetry was not explained by the decline in chaeta number in the lines under only natural selection. However, the decline was consistent with changes in total phenotypic variance and environmental variance.— The divergence between lines after 39 generations of selection was seen in differences in asymmetry and also in the genotype-environment interaction expressed in cross-culturing experiments.

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Natural selection on plasticity of thermal traits in a highly seasonal environment

10.1101/191825 ◽

2017 ◽

Cited By ~ 1

Author(s):

Leonardo D. Bacigalupe ◽

Juan D. Gaitan-Espitia ◽

Aura M. Barria ◽

Avia Gonzalez-Mendez ◽

Manuel Ruiz-Aravena ◽

...

Keyword(s):

Natural Selection ◽

Evolutionary Biology ◽

Thermal Sensitivity ◽

Natural Populations ◽

Thermal Acclimation ◽

Directional Selection ◽

Theoretic Approach ◽

Information Theoretic ◽

Peer Community ◽

Information Theoretic Approach

AbstractThis preprint has been reviewed and recommended by Peer Community In Evolutionary Biology (http://dx.doi.org/10.24072/pci.evolbiol.100048). For ectothermic species with broad geographical distributions, latitudinal/altitudinal variation in environmental temperatures (averages and extremes) are expected to shape the evolution of physiological tolerances and the acclimation capacity (i.e., degree of phenotypic plasticity) of natural populations. This can create geographical gradients of selection in which environments with greater thermal variability (e.g., seasonality) tend to favour individuals that maximize performance across a broader range of temperatures compared to more stable environments. Although thermal acclimation capacity plays a fundamental role in this context, it is unknown whether natural selection targets this trait in natural populations. Here we addressed such an important gap in our knowledge by measuring survival, through mark recapture integrated into an information-theoretic approach, as a function of the plasticity of critical thermal limits for activity, behavioural thermal preference and the thermal sensitivity of metabolism in the northernmost population of the four-eyed frogPleurodema thaul. Overall, our results indicate that thermal acclimation in this population is not being targeted by directional selection, although there might be signals of selection on individual traits. According to the most supported models, survival decreased in individuals with less tolerance to cold when cold-acclimated (probably because daily low extremes are frequent during the cooler periods of the year) and increased with body size. However, in both cases, the directional selection estimates were non-significant.

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The natural selection of psychosis

Behavioral and Brain Sciences ◽

10.1017/s0140525x0628909x ◽

2006 ◽

Vol 29 (4) ◽

pp. 410-411 ◽

Cited By ~ 4

Author(s):

Bernard Crespi

Keyword(s):

Natural Selection ◽

Mental Disorders ◽

Evolutionary Biology ◽

Secondary Effects ◽

Strong Selection ◽

Selection For ◽

Selection Of

Diverse evidence from genomics, epidemiology, neurophysiology, psychology, and evolutionary biology converges on simple general mechanisms, based on negative secondary effects of strong selection, for how mental disorders such as psychosis have evolved and how they are sustained.

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Specific features of long-term domestication of australian crayfish Cherax quadricarinatus in conditions of the western part of Russian Federation

Izvestiya TINRO ◽

10.26428/1606-9919-2018-194-188-192 ◽

2018 ◽

Vol 194 ◽

pp. 188-192

Author(s):

D. I. Shokasheva

Keyword(s):

Natural Selection ◽

Russian Federation ◽

Natural Populations ◽

Cherax Quadricarinatus ◽

Local Environments ◽

Local Species ◽

Adaptive Ability

Natural populations of crayfish are in depression in Russia and local species are not cultivated. In this situation, experimental cultivation of allochtonous australian crayfish Cherax quadricarinatus is conducted. This species is distinguished by high reproductive abilities and good consumer properties. It has domesticated in Russia spontaneously and produced 9–10 generations in Astrakhan Region. Certain natural selection in the process of domestication provides adaptive ability of this species to local environments and its capability to reproduce a viable progeny, so there is no doubts in good prospects of its cultivation in industrial conditions.

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The Evolutionary Biology of Species

10.1093/oso/9780198749745.001.0001 ◽

2019 ◽

Cited By ~ 7

Author(s):

Timothy G. Barraclough

Keyword(s):

Evolutionary Biology ◽

Biological Diversity ◽

Distinct Species ◽

Species Boundaries ◽

Central Thesis ◽

Species Accumulation ◽

Multicellular Organisms ◽

Broad Approach ◽

Over Time

‘Species’ are central to understanding the origin and dynamics of biological diversity; explaining why lineages split into multiple distinct species is one of the main goals of evolutionary biology. However, the existence of species is often taken for granted, and precisely what is meant by species and whether they really exist as a pattern of nature has rarely been modelled or critically tested. This novel book presents a synthetic overview of the evolutionary biology of species, describing what species are, how they form, the consequences of species boundaries and diversity for evolution, and patterns of species accumulation over time. The central thesis is that species represent more than just a unit of taxonomy; they are a model of how diversity is structured as well as how groups of related organisms evolve. The author adopts an intentionally broad approach to consider what species constitute, both theoretically and empirically, and how we detect them, drawing on a wealth of examples from microbes to multicellular organisms.

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Inferring Linkage Disequilibrium Between a Polymorphic Marker Locus and a Trait Locus in Natural Populations

Genetics ◽

10.1093/genetics/156.1.457 ◽

2000 ◽

Vol 156 (1) ◽

pp. 457-467 ◽

Cited By ~ 1

Author(s):

Z W Luo ◽

S H Tao ◽

Z-B Zeng

Keyword(s):

Linkage Disequilibrium ◽

Allele Frequency ◽

Random Mating ◽

Natural Populations ◽

Polymorphic Marker ◽

Marker Locus ◽

Model Parameters ◽

Phenotypic Variance ◽

Wide Range ◽

Trait Locus

Abstract Three approaches are proposed in this study for detecting or estimating linkage disequilibrium between a polymorphic marker locus and a locus affecting quantitative genetic variation using the sample from random mating populations. It is shown that the disequilibrium over a wide range of circumstances may be detected with a power of 80% by using phenotypic records and marker genotypes of a few hundred individuals. Comparison of ANOVA and regression methods in this article to the transmission disequilibrium test (TDT) shows that, given the genetic variance explained by the trait locus, the power of TDT depends on the trait allele frequency, whereas the power of ANOVA and regression analyses is relatively independent from the allelic frequency. The TDT method is more powerful when the trait allele frequency is low, but much less powerful when it is high. The likelihood analysis provides reliable estimation of the model parameters when the QTL variance is at least 10% of the phenotypic variance and the sample size of a few hundred is used. Potential use of these estimates in mapping the trait locus is also discussed.

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GENETIC LOAD IN NATURAL POPULATIONS: IS IT COMPATIBLE WITH THE HYPOTHESIS THAT MANY POLYMORPHISMS ARE MAINTAINED BY NATURAL SELECTION?

Genetics ◽

10.1093/genetics/77.3.569 ◽

1974 ◽

Vol 77 (3) ◽

pp. 569-589

Author(s):

Martin L Tracey ◽

Francisco J Ayala

Keyword(s):

Drosophila Melanogaster ◽

Natural Selection ◽

Natural Population ◽

Natural Populations ◽

Genetic Load ◽

Structural Genes ◽

Invertebrate Species ◽

Average Proportion ◽

Mean Fitness ◽

The Mean

ABSTRACT Recent studies of genetically controlled enzyme variation lead to an estimation that at least 30 to 60% of the structural genes are polymorphic in natural populations of many vertebrate and invertebrate species. Some authors have argued that a substantial proportion of these polymorphisms cannot be maintained by natural selection because this would result in an unbearable genetic load. If many polymorphisms are maintained by heterotic natural selection, individuals with much greater than average proportion of homozygous loci should have very low fitness. We have measured in Drosophila melanogaster the fitness of flies homozygous for a complete chromosome relative to normal wild flies. A total of 37 chromosomes from a natural population have been tested using 92 experimental populations. The mean fitness of homozygous flies is 0.12 for second chromosomes, and 0.13 for third chromosomes. These estimates are compatible with the hypothesis that many (more than one thousand) loci are maintained by heterotic selection in natural populations of D. melanogaster.

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Genome size correlates with reproductive fitness in seed beetles

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2015.1421 ◽

2015 ◽

Vol 282 (1815) ◽

pp. 20151421 ◽

Cited By ~ 14

Author(s):

Göran Arnqvist ◽

Ahmed Sayadi ◽

Elina Immonen ◽

Cosima Hotzy ◽

Daniel Rankin ◽

...

Keyword(s):

Life History ◽

Natural Selection ◽

Genome Size ◽

Evolutionary Biology ◽

Large Scale ◽

Life History Traits ◽

Single Species ◽

Reproductive Fitness ◽

Correlated Evolution ◽

Seed Beetles

The ultimate cause of genome size (GS) evolution in eukaryotes remains a major and unresolved puzzle in evolutionary biology. Large-scale comparative studies have failed to find consistent correlations between GS and organismal properties, resulting in the ‘ C -value paradox’. Current hypotheses for the evolution of GS are based either on the balance between mutational events and drift or on natural selection acting upon standing genetic variation in GS. It is, however, currently very difficult to evaluate the role of selection because within-species studies that relate variation in life-history traits to variation in GS are very rare. Here, we report phylogenetic comparative analyses of GS evolution in seed beetles at two distinct taxonomic scales, which combines replicated estimation of GS with experimental assays of life-history traits and reproductive fitness. GS showed rapid and bidirectional evolution across species, but did not show correlated evolution with any of several indices of the relative importance of genetic drift. Within a single species, GS varied by 4–5% across populations and showed positive correlated evolution with independent estimates of male and female reproductive fitness. Collectively, the phylogenetic pattern of GS diversification across and within species in conjunction with the pattern of correlated evolution between GS and fitness provide novel support for the tenet that natural selection plays a key role in shaping GS evolution.

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Heritability of Motor Skill

Acta geneticae medicae et gemellologiae twin research ◽

10.1017/s0001566000008606 ◽

1980 ◽

Vol 29 (2) ◽

pp. 127-136 ◽

Cited By ~ 14

Author(s):

L. R. T. Williams ◽

J. B. Gross

Keyword(s):

Environmental Effects ◽

Motor Skill ◽

Error Variance ◽

Phenotypic Variance ◽

Environmental Variance ◽

Gross Motor ◽

Gross Motor Skills ◽

Early Stages ◽

Balance Task ◽

And Performance

A total of 22 monozygotic (MZ) and 41 dizygotic (DZ) twin pairs were given 72 trials on a stabilometer balance task over six days to study the extent of the genetic contribution to learning and performance of a gross motor skill. The expectations that interindividual differences would be less for the MZ than for the DZ twins and that intraindividual variability would not be different between the two groups were supported. Intraclass correlations were used to provide estimates for the proportions of total phenotypic variance accounted for by heritability (h2), systematic environmental variance (E2), and nonsystematic environmental effects (e2). Heritability was found to be low during the early stages of learning, before it increased to stabilize at approximately 65% for the remaining practice. E2 was highest during these early stages (24%), then declined quickly to stabilize at half that level. Error variance (e2) constituted the remaining variance. Learning profiles of the twin pairs were also analyzed, with a greater intrapair resemblance being found for the MZ twins. The present findings indicate that, for gross motor skills, there is considerable potential for influencing both the levels of performance (and learning) and the differences between individuals by judicious use of systematic environmental effects.

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Dynamics of transposable elements under the selection model

Genetics Research ◽

10.1017/s0016672399003997 ◽

1999 ◽

Vol 74 (2) ◽

pp. 159-164 ◽

Cited By ~ 16

Author(s):

A. TSITRONE ◽

S. CHARLES ◽

C. BIÉMONT

Keyword(s):

Equilibrium Point ◽

Dynamic Characteristics ◽

Time Scale ◽

Copy Number ◽

Stable Equilibrium ◽

Stable Equilibrium Point ◽

Asymptotically Stable ◽

Weak Selection ◽

Strong Selection ◽

Long Time

We examine an analytical model of selection against the deleterious effects of transposable element (TE) insertions in Drosophila, focusing attention on the asymptotic and dynamic characteristics. With strong selection the only asymptotically stable equilibrium point corresponds to extinction of the TEs. With very weak selection a stable and realistic equilibrium point can be obtained. The dynamics of the system is fast for strong selection and slow, on the human time scale, for weak selection. Hence weak selection acts as a force that contributes to the stabilization of mean TE copy number. The consequence is that under weak selection, and ‘out-of-equilibrium’ situation can be maintained for a long time in populations, with mean TE copy number appearing stabilized.

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