DOCSLIB.ORG

The Effects of Stabilizing and Directional Selection on Phenotypic and Genotypic Variation in a Population of RNA Enzymes

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Effects of Stabilizing and Directional Selection on Phenotypic and Genotypic Variation in a Population of RNA Enzymes J Mol Evol (2014) 78:101–108 DOI 10.1007/s00239-013-9604-x ORIGINAL ARTICLE The Effects of Stabilizing and Directional Selection on Phenotypic and Genotypic Variation in a Population of RNA Enzymes Eric J. Hayden • Sinisa Bratulic • Iwo Koenig • Evandro Ferrada • Andreas Wagner Received: 26 September 2013 / Accepted: 23 November 2013 / Published online: 6 December 2013 Ó Springer Science+Business Media New York 2013 Abstract The distribution of variation in a quantitative Introduction trait and its underlying distribution of genotypic diversity can both be shaped by stabilizing and directional selection. A population of organisms or molecules with some quanti- Understanding either distribution is important, because it tative phenotype P, where natural selection favors an determines a population’s response to natural selection. increase or decrease in P, and where the population mean of P Unfortunately, existing theory makes conflicting predictions is consequently changing over time, is said to be under about how selection shapes these distributions, and very little directional selection. This mode of selection typically occurs pertinent experimental evidence exists. Here we study a when a population experiences a new environment and many simple genetic system, an evolving RNA enzyme (ribozyme) individuals find themselves poorly adapted. Over time, such in which a combination of high throughput genotyping and a population would adapt to its environment, and enter a measurement of a biochemical phenotype allow us to address regime of stabilizing selection, during which the population this question. We show that directional selection, compared mean phenotype P no longer changes. Because of its to stabilizing selection, increases the genotypic diversity of importance for understanding Darwinian evolution, the an evolving ribozyme population. In contrast, it leaves the effects of directional and stabilizing selection on phenotypes variance in the phenotypic trait unchanged. have received considerable attention by theorists. One simple question with no straightforward answer Keywords Ribozymes Á Experimental evolution Á regards the effects of directional and stabilizing selection Genotype to phenotype Á Directional selection Á on the phenotypic variance of a population. Because Stabilizing selection Á Sequence space directional selection can favor extreme phenotypes, one might think that it would cause an increase not only in the mean, but also in the phenotypic variance of the popula- E. J. Hayden (&) Department of Biological Science, Boise State University, Boise, tion. However, this is not necessarily the case. Whether it ID, USA does depends on several factors, including the shape— e-mail: [email protected] convex or concave—of the fitness function (Layzer 1978), the distribution of trait values (Bu¨rger 1991; Hansen 1992), S. Bratulic Á A. Wagner Institute of Evolutionary Biology and Environmental Studies, whether a trait optimum fluctuates with time, the presence University of Zurich, Zurich, Switzerland and kind of genotype-by-environment interactions (Her- misson and Wagner 2004), the existence of epistatic S. Bratulic Á A. Wagner interactions among loci (Hansen 2006), and the extent of The Swiss Institute of Bioinformatics, Lausanne, Switzerland phenotypic canalization before the onset of directional I. Koenig selection (de Visser et al. 2003; Hermisson and Wagner Department of Biochemistry, University of Zurich, Zurich, 2004). The change in phenotypic variance caused by Switzerland periods of stabilizing selection is no easier to predict. It E. Ferrada Á A. Wagner depends upon several attributes of genetic architecture, The Santa Fe Institute, Santa Fe, NM, USA which include epistasis (Hermisson et al. 2003), the 123 102 J Mol Evol (2014) 78:101–108 structure of the fitness landscape (Barton and Turelli 1987), individual sequence occupies a discrete point in this space. the number of loci involved in a trait (Turelli and Barton Two sequences have a distance that is defined as the number 1990;Bu¨rger 1991), and the extent of canalization (Wagner of nucleotide changes necessary to change one sequence into et al. 1997). Overall, existing theory does not make any the other. The genotypes of a given population can be viewed simple and general predictions for the change in pheno- as a cloud in genotype space. Here, we describe the effects on typic variance over time. Unfortunately, there is also very this cloud of genotypes as it experiences stabilizing selection little experimental data that speak to this question, with the that is followed by a period of directional selection. exception of the observation that stressful environments We previously conducted evolution experiments where can cause a release of previously hidden phenotypic vari- we exposed the Azoarcus group I ribozyme to two different ation with a genetic basis (Waddington 1959; Scharloo chemical environments (Hayden et al. 2011). The ribozyme 1991; Rutherford and Lindquist 1998; True and Lindquist has the ability to cleave an exogenous RNA substrate 2000; Gibson and Dworkin 2004; Flatt 2005; Hayden et al. because this activity is a component of its catalytic role in 2011). nature as a self-splicing intron (Tanner and Cech 1996). In Directional and stabilizing selection can not only affect the first environment we supplied a ribozyme population the distribution of phenotypes, but also the distribution of with a ‘‘native’’ RNA oligonucleotide. Cleavage of this oli- genotypes, and especially their diversity. Next to no gonucleotide results in the ligation of a portion of the sub- experimental data are available about these effects, and strate to the 30-end of the ribozyme, and we can exploit this mainly for two reasons. First, it has not been feasible until sequence modification to selectively amplify catalytically recently to genotype many individuals in an evolving successful molecules (Beaudry and Joyce 1992; Lehman and population. Second, many phenotypic traits are complex Joyce 1993). Molecules with higher activity are more likely and have unknown genetic components. Next-generation to be replicated. We previously observed that in this chem- sequencing technologies are beginning to allow us to ical environment, the average activity of the population did overcome the first problem (Kvitek and Sherlock 2011; not change significantly over eight rounds of mutation and Ensminger et al. 2012; Traverse et al. 2013; Herron and selection on this native substrate. Further, we did not detect Doebeli 2013; Jime´nez et al. 2013), especially for the rel- any mutations that were increasing in frequency over time, atively simple phenotypic traits of molecules, where the which would indicate a selective advantage for ribozymes second problem is not an issue. For such molecular traits, containing them. We concluded that the population was one can obtain complete genotypic information of many well-adapted to this native substrate. Herein, we refer to the individuals in an evolving population (Hietpas et al. 2011; population from the eighth round of this selection as our Hayden et al. 2011). The purpose of this paper is to study Stabilizing Selection population (SS). the evolution of both phenotypic and genotypic variation in The second chemical environment is one to which the an especially transparent molecular system, a population of ancestral wild-type Azoarcus ribozyme is poorly adapted. evolving RNA enzymes. Specifically, we introduced a chemical modification The phenotypic trait in our study system is the catalytic (phosphorothioate) into the RNA backbone of the substrate, activity of the RNA enzyme (ribozyme) derived from the and exposed a ribozyme population to this modified sub- Azoarcus group I self-splicing intron (Tanner and Cech strate. We mutagenized the members of this SS population, 1996). Ribozymes are nucleic acid sequences with a catalytic and then exerted selection by amplifying molecules that function. Thus, phenotype and genotype are linked to a could cleave this new substrate, performing an additional single molecule in this system. Populations of ribozyme eight ‘‘generations’’ of mutation and selection in this way. genotypes can be enzymatically replicated in the lab. Under this second selection pressure, the population adapted Genotypic and phenotypic diversity is introduced through rapidly to the new substrate. The average activity of the nucleotide mutations made during replication. Selection can population after eight generations was significantly higher be applied to exploit the differences in catalytic activity than it was prior to this selection. This demonstrates direc- caused by these mutations, resulting in Darwinian evolution tional selection exerted by the introduction of the new sub- (Joyce 2004). An important feature of our study system is strate. We will refer to the population from the eighth round that the phenotypes are encoded in very small genotypes of this second selection as the directional selection (DS) (\200 bp). For such genotypes, high throughput sequencing population. These experimentally derived populations technology can be used to analyze many genotypes in facilitate a comparison between the distribution of pheno- evolving RNA populations (Pitt and Ferre-D’Amare 2010; types and genotypes resulting from an equal number of Hayden et al. 2011). In other words, they allow us to study rounds (eight) of each type of selection. Our previous activity empirically how such populations spread through the vast measurements were based on
Load more

Recommended publications
  • An Introgression Analysis of Quantitative Trait Loci That Contribute to a Morphological Difference Between Drosophila Simulans and D
    Copyight 0 1997 by the Genetics Societv of America An Introgression Analysis of Quantitative Trait Loci That Contribute to a Morphological Difference Between Drosophila simulans and D. mauritiana Cathy C. Laurie, John R. True, Jianjun Liu and John M. Mercer Department of Zoology, Duke University, Durham, North Carolina 27708 Manuscript received August 12, 1996 Accepted for publication October 29, 1996 ABSTRACT Drosophila simulans and D. maum'tiana differ markedly in morphology of the posterior lobe, a male- specific genitalic structure. Bothsize and shapeof the lobe can be quantifiedby a morphometric variable, PC1, derived from principal components and Fourier analyses. The genetic architectureof the species difference in PC1 was investigated previously by composite interval mapping, which revealed largely additive inheritance, with a minimum of eight quantitative trait loci (QTL) affecting the trait. This analysis was extended by introgression of marked segments of the maun'tiana third chromosome into a simulans background by repeated backcrossing. Thetwo types of experiment are consistentin suggesting that several QTL on the third chromosome may have effects in the range of 10-15% of the parental difference andthat all or nearly all QTL have effects in the same direction. Since the parental difference is large (30.4 environmental standard deviations), effects of this magnitude can produce alternative homozygotes with little overlap in phenotype. However, these estimates may not reflect the effects of individual loci, since each interval or introgressed segment may contain multiple QTL. The consistent direction of allelic effects suggests a history of directional selection on the posterior lobe. HE genetic analysis of a quantitative trait usually ual genes that affect continuously variable traits.
    [Show full text]
  • Microevolution and the Genetics of Populations ​ ​ Microevolution Refers to Varieties Within a Given Type
    Chapter 8: Evolution Lesson 8.3: Microevolution and the Genetics of Populations ​ ​ Microevolution refers to varieties within a given type. Change happens within a group, but the descendant is clearly of the same type as the ancestor. This might better be called variation, or adaptation, but the changes are "horizontal" in effect, not "vertical." Such changes might be accomplished by "natural selection," in which a trait ​ ​ ​ ​ within the present variety is selected as the best for a given set of conditions, or accomplished by "artificial selection," such as when dog breeders produce a new breed of dog. Lesson Objectives ● Distinguish what is microevolution and how it affects changes in populations. ● Define gene pool, and explain how to calculate allele frequencies. ● State the Hardy-Weinberg theorem ● Identify the five forces of evolution. Vocabulary ● adaptive radiation ● gene pool ● migration ● allele frequency ● genetic drift ● mutation ● artificial selection ● Hardy-Weinberg theorem ● natural selection ● directional selection ● macroevolution ● population genetics ● disruptive selection ● microevolution ● stabilizing selection ● gene flow Introduction Darwin knew that heritable variations are needed for evolution to occur. However, he knew nothing about Mendel’s laws of genetics. Mendel’s laws were rediscovered in the early 1900s. Only then could scientists fully understand the process of evolution. Microevolution is how individual traits within a population change over time. In order for a population to change, some things must be assumed to be true. In other words, there must be some sort of process happening that causes microevolution. The five ways alleles within a population change over time are natural selection, migration (gene flow), mating, mutations, or genetic drift.
    [Show full text]
  • Directional Selection and Variation in Finite Populations
    Copyright 0 1987 by the Genetics Society of America Directional Selection and Variation in Finite Populations Peter D. Keightley and ‘William G. Hill Institute of Animal Genetics, University of Edinburgh, West Mains Road, Edinburgh EH9 3JN, Scotland Manuscript received April 12, 1987 Revised copy accepted July 16, 1987 ABSTRACT Predictions are made of the equilibrium genetic variances and responses in a metric trait under the joint effects of directional selection, mutation and linkage in a finite population. The “infinitesimal model“ is analyzed as the limiting case of many mutants of very small effect, otherwise Monte Carlo simulation is used. If the effects of mutant genes on the trait are symmetrically distributed and they are unlinked, the variance of mutant effects is not an important parameter. If the distribution is skewed, unless effects or the population size is small, the proportion of mutants that have increasing effect is the critical parameter. With linkage the distribution of genotypic values in the population becomes skewed downward and the equilibrium genetic variance and response are smaller as disequilibrium becomes important. Linkage effects are greater when the mutational variance is contributed by many genes of small effect than few of large effect, and are greater when the majority of mutants increase rather than decrease the trait because genes that are of large effect or are deleterious do not segregate for long. The most likely conditions for ‘‘Muller’s ratchet” are investi- gated. N recent years there has been much interest in the is attained more quickly in the presence of selection I production and maintenance of variation in pop- than in its absence, and is highly dependent on popu- ulations by mutation, stimulated by the presence of lation size.
    [Show full text]
  • Patterns and Power of Phenotypic Selection in Nature
    Articles Patterns and Power of Phenotypic Selection in Nature JOEL G. KINGSOLVER AND DAVID W. PFENNIG Phenotypic selection occurs when individuals with certain characteristics produce more surviving offspring than individuals with other characteristics. Although selection is regarded as the chief engine of evolutionary change, scientists have only recently begun to measure its action in the wild. These studies raise numerous questions: How strong is selection, and do different types of traits experience different patterns of selection? Is selection on traits that affect mating success as strong as selection on traits that affect survival? Does selection tend to favor larger body size, and, if so, what are its consequences? We explore these questions and discuss the pitfalls and future prospects of measuring selection in natural populations. Keywords: adaptive landscape, Cope’s rule, natural selection, rapid evolution, sexual selection henotypic selection occurs when individuals with selection on traits that affect survival stronger than on those Pdifferent characteristics (i.e., different phenotypes) that affect only mating success? In this article, we explore these differ in their survival, fecundity, or mating success. The idea and other questions about the patterns and power of phe- of phenotypic selection traces back to Darwin and Wallace notypic selection in nature. (1858), and selection is widely accepted as the primary cause of adaptive evolution within natural populations.Yet Darwin What is selection, and how does it work? never attempted to measure selection in nature, and in the Selection is the nonrandom differential survival or repro- century following the publication of On the Origin of Species duction of phenotypically different individuals.
    [Show full text]
  • Selection and Gene Duplication: a View from the Genome Comment Andreas Wagner
    http://genomebiology.com/2002/3/5/reviews/1012.1 Minireview Selection and gene duplication: a view from the genome comment Andreas Wagner Address: Department of Biology, University of New Mexico, 167A Castetter Hall, Albuquerque, NM 817131-1091, USA. E-mail: [email protected] Published: 15 April 2002 Genome Biology 2002, 3(5):reviews1012.1–1012.3 reviews The electronic version of this article is the complete one and can be found online at http://genomebiology.com/2002/3/5/reviews/1012 © BioMed Central Ltd (Print ISSN 1465-6906; Online ISSN 1465-6914) Abstract reports Immediately after a gene duplication event, the duplicate genes have redundant functions. Is natural selection therefore completely relaxed after duplication? Does one gene evolve more rapidly than the other? Several recent genome-wide studies have suggested that duplicate genes are always under purifying selection and do not always evolve at the same rate. deposited research When a gene duplication event occurs, the duplicate genes synonymous (silent) nucleotide substitutions, Ks, and have redundant functions. Many deleterious mutations may second, of non-synonymous nucleotide substitutions (which then be harmless, because even if one gene suffers a muta- change the encoded amino acid), Ka (see Box 1). The ratio tion, the redundant gene copy can provide a back-up func- Ka/Ks provides a measure of the selection pressure to which tion. Put differently, after gene duplication - which can arise a gene pair is subject. If a duplicate gene pair shows a Ka/Ks through polyploidization (whole-genome duplication), non- ratio of about 1, that is, if amino-acid replacement substitu- homologous recombination, or through the action of retro- tions occur at the same rate as synonymous substitutions, transposons - one or both duplicates should experience then few or no amino-acid replacement substitutions have refereed research relaxed selective constraints that result in elevated rates of been eliminated since the gene duplication.
    [Show full text]
  • Natural Selection One of the Most Important Contributions Made to The
    Natural Selection One of the most important contributions made to the science of evolution by Charles Darwin is the concept of natural selection. The idea that members of a species compete with each other for resources and that individuals that are better adapted to their lifestyle have a better chance of surviving to reproduce revolutionized the field of evolution, though it was not accepted until several decades after Darwin first proposed it. Today, natural selection forms the foundation for our understanding of how species change over time. Natural selection may act to change a trait in many ways. When environmental pressures favor the average form of the trait, selection is said to be stabilizing. Directional selection occurs when selection pressures favor one extreme of the trait distribution. Selection is disruptive when the average form of the trait is selected against while either extreme is unaffected. In addition to natural selection, there are two other types of selection. Sexual selection, which Darwin believed was distinct from natural selection, involves the selection of traits based on their role in courtship and mating. Artificial selection is the selective breeding of species by humans to increase desirable traits, though the traits do not necessarily have to confer greater fitness. Summary of Types of Natural Selection Natural selection can take many forms. To make talking about this easier, we will consider the distribution of traits across a population in using a graph. To the right is a normal curve. For example, if we were talking about height as a trait, we would see that without any selection pressure on this trait, the heights of individuals in a population would vary, with most individuals being of an average height and fewer being extremely short or extremely tall.
    [Show full text]
  • Detecting the Form of Selection from DNA Sequence Data
    Outlook COMMENT Male:female mutation ratio muscular dystrophy, neurofibromatosis and retinoblast- outcome of further investigation, this unique transposition oma), there is a large male excess. So, I believe the evidence event and perhaps others like it are sure to provide impor- is convincing that the male base-substitution rate greatly tant cytogenetic and evolutionary insights. exceeds the female rate. There are a number of reasons why the historical Acknowledgements male:female mutation ratio is likely to be less than the I have profited greatly from discussions with my colleagues current one, the most important being the lower age of B. Dove, B. Engels, C. Denniston and M. Susman. My reproduction in the earliest humans and their ape-like greatest debt is to D. Page for a continuing and very fruitful ancestors. More studies are needed. But whatever the dialog and for providing me with unpublished data. References Nature 406, 622–625 6 Engels, W.R. et al. (1994) Long-range cis preference in DNA 1 Vogel, F. and Motulsky, A. G. (1997) Human Genetics: 4 Shimmin, L.C. et al. (1993) Potential problems in estimating homology search over the length of a Drosophila chromosome. Problems and Approaches. Springer-Verlag the male-to-female mutation rate ratio from DNA sequence Science 263, 1623–1625 2 Crow, J. F. (1997) The high spontaneous mutation rate: is it a data. J. Mol. Evol. 37, 160–166 7 Crow, J.F. (2000) The origins, patterns and implications of health risk? Proc. Natl. Acad. Sci. U. S. A. 94, 8380–8386 5 Richardson, C. et al.
    [Show full text]
  • Supplementary Information for Vyssotski, 2013
    Supplementary Information for Vyssotski, 2013 www.evolocus.com/evolocus/v1/evolocus-01-013-s.pdf Evolocus Supplementary Information for Transgenerational epigenetic compensation and sex u al d imorph ism 1,2,3 Dmitri L. Vyssotski Published 17 May 2013, Evolocus 1, 13-18 (2013): http://www.evolocus.com/evolocus/v1/evolocus-01-013.pdf In natu ral popu lation transgenerational epigenetic compensation is by unknown mechanisms, the mechanisms those were difficult to generated in h omoz y gou s mu tants, mainly in males. It d oes not imagine, and this possibility was abandoned for over 47 years. immed iately affect th e ph enoty pe of h omoz y gou s mu tants, w h ere The higher variability in males can be a result of a not so good it w as generated . Transgenerational epigenetic compensation is canalization of their ontogenesis, and the canalization of localiz ed not in th e same locu s as original mu tation and it is ontogenesis is modulated by sex hormones. Thus, we can d ominant, b ecau se it affects th e ph enoty pe ev en if it is receiv ed imagine that the canalization of ontogenesis in males is from one parent. In fu rth er generations, starting from F 2, it is more artificially decreased in comparison with females by means of ex pressed in females th an in males: it increases fitness of hormonal differences. h omozy gou s mu tant females, d ecreases fitness of w ild ty pe The shift of the female distribution to the right was not females and h as w eak effect on h eterozy gou s females.
    [Show full text]
  • Stabilizing Selection Shapes Variation in Phenotypic Plasticity
    bioRxiv preprint doi: https://doi.org/10.1101/2021.07.29.454146; this version posted July 29, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission. 1 Stabilizing selection shapes variation in phenotypic plasticity 2 3 4 5 Dörthe Becker1,2,*, 6 Karen Barnard-Kubow1,3, 7 Robert Porter1, 8 Austin Edwards1,4, 9 Erin Voss1,5, 10 Andrew P. Beckerman2, 11 Alan O. Bergland1,* 12 13 14 1Department of Biology; University of Virginia, Charlottesville/VA, USA 15 2Department of Animal and Plant Sciences; University of Sheffield, Sheffield, UK 16 3Department of Biology, James Madison University, Harrisonburg/VA, USA 17 4Biological Imaging Development CoLab, University of California San Francisco, 18 San Francisco/CA, USA 19 5Department of Integrative Biology, University of California Berkeley, 20 Berkeley/CA 21 22 * to whom correspondence should be addressed: 23 DB ([email protected]), AOB ([email protected]) 24 25 26 27 Keywords: stabilizing selection; phenotypic plasticity; heritability; Daphnia; 28 defense morphologies 1 bioRxiv preprint doi: https://doi.org/10.1101/2021.07.29.454146; this version posted July 29, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission. 29 Abstract 30 The adaptive nature of phenotypic plasticity is widely documented in natural 31 populations. However, little is known about the evolutionary forces that shape 32 genetic variation in plasticity within populations. Here we empirically address this 33 issue by testing the hypothesis that stabilizing selection shapes genetic variation 34 in the anti-predator developmental plasticity of Daphnia pulex.
    [Show full text]
  • Selection on Breeding Date and Body Size in Colonizing Coho Salmon, Oncorhynchus Kisutch
    Molecular Ecology (2010) 19, 2562–2573 doi: 10.1111/j.1365-294X.2010.04652.x Selection on breeding date and body size in colonizing coho salmon, Oncorhynchus kisutch J. H. ANDERSON,* P. L. FAULDS,† W. I. ATLAS,‡ G. R. PESS§ and T. P. QUINN* *School of Aquatic and Fishery Sciences, University of Washington, Box 355020, Seattle, WA 98195, USA, †Seattle Public Utilities, 700 5th Avenue, Suite 4900, Seattle, WA, 98124, USA, ‡Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6, §National Marine Fisheries Service, Northwest Fisheries Science Center, 2725 Montlake Boulevard East, Seattle, WA 98195, USA Abstract Selection during the colonization of new habitat is critical to the process of local adaptation, but has rarely been studied. We measured the form, direction, and strength of selection on body size and date of arrival to the breeding grounds over the first three cohorts (2003–2005) of a coho salmon (Oncorhynchus kisutch) population colonizing 33 km of habitat made accessible by modification of Landsburg Diversion Dam, on the Cedar River, Washington, USA. Salmon were sampled as they bypassed the dam, parentage was assigned based on genotypes from 10 microsatellite loci, and standardized selection gradients were calculated using the number of returning adult offspring as the fitness metric. Larger fish in both sexes produced more adult offspring, and the magnitude of the effect increased in subsequent years for males, suggesting that low densities attenuated traditional size-biased intrasexual competition. For both sexes, directional selection favoured early breeders in 2003, but stabilizing selection on breeding date was observed in 2004 and 2005.
    [Show full text]
  • The Peppered Moth and Industrial Melanism: Evolution of a Natural Selection Case Study
    Heredity (2013) 110, 207–212 & 2013 Macmillan Publishers Limited All rights reserved 0018-067X/13 www.nature.com/hdy REVIEW The peppered moth and industrial melanism: evolution of a natural selection case study LM Cook1 and IJ Saccheri2 From the outset multiple causes have been suggested for changes in melanic gene frequency in the peppered moth Biston betularia and other industrial melanic moths. These have included higher intrinsic fitness of melanic forms and selective predation for camouflage. The possible existence and origin of heterozygote advantage has been debated. From the 1950s, as a result of experimental evidence, selective predation became the favoured explanation and is undoubtedly the major factor driving the frequency change. However, modelling and monitoring of declining melanic frequencies since the 1970s indicate either that migration rates are much higher than existing direct estimates suggested or else, or in addition, non-visual selection has a role. Recent molecular work on genetics has revealed that the melanic (carbonaria) allele had a single origin in Britain, and that the locus is orthologous to a major wing patterning locus in Heliconius butterflies. New methods of analysis should supply further information on the melanic system and on migration that will complete our understanding of this important example of rapid evolution. Heredity (2013) 110, 207–212; doi:10.1038/hdy.2012.92; published online 5 December 2012 Keywords: Biston betularia; carbonaria gene; mutation; predation; non-visual selection; migration INTRODUCTION EARLY EVIDENCE OF CHANGE The peppered moth Biston betularia (L.) and its melanic mutant will The peppered moth was the most diagrammatic example of the be familiar to readers of Heredity as an example of rapid evolutionary phenomenon of industrial melanism that came to be recognised in change brought about by natural selection in a changing environment, industrial and smoke-blackened parts of England in the mid-nine- evenifthedetailsofthestoryarenot.Infact,thedetailsarelesssimple teenth century.
    [Show full text]
  • Natural Selection in a Contemporary Human Population
    Natural selection in a contemporary human population Sean G. Byarsa, Douglas Ewbankb, Diddahally R. Govindarajuc, and Stephen C. Stearnsa,1 aDepartment of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06520-8102; bPopulation Studies Center, University of Pennsylvania, Philadelphia, PA 19104-6299; and cDepartment of Neurology, Boston University School of Medicine, Boston, MA 02118-2526 Edited by Peter T. Ellison, Harvard University, Cambridge, MA, and approved September 16, 2009 (received for review June 25, 2009) Our aims were to demonstrate that natural selection is operating sity to identify factors that contribute to cardiovascular disease. on contemporary humans, predict future evolutionary change for It is the longest running multigenerational study in medical specific traits with medical significance, and show that for some history. The people originally enrolled in the study were of pre- traits we can make short-term predictions about our future evolu- dominantly European ancestry (20% United Kingdom, 40% tion. To do so, we measured the strength of selection, estimated Ireland, 10% Italy, 10% Quebec). The original cohort (n = genetic variation and covariation, and predicted the response to 5,209) has been examined every 2 years, a total of 29 times selection for women in the Framingham Heart Study, a project of between 1948 and 2008. The offspring cohort (n = 5,124) has the National Heart, Lung, and Blood Institute and Boston Univer- been examined approximately every 4 years, a total of eight times sity that began in 1948. We found that natural selection is acting between 1971 and 2008 (4). There is also a third generation to cause slow, gradual evolutionary change.
    [Show full text]