DOCSLIB.ORG

Pleiotropy, Apparent Stabilizing Selection and Uncovering Fitness Optima

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Pleiotropy, Apparent Stabilizing Selection and Uncovering Fitness Optima Opinion Pleiotropy, apparent stabilizing selection and uncovering fitness optima Katrina McGuigan1, Locke Rowe2 and Mark W. Blows1 1 School of Biological Sciences, University of Queensland, Brisbane 4072, QLD, Australia 2 Ecology and Evolutionary Biology, University of Toronto, Toronto, Canada, M5S 3G5 Evolutionary theory has emphasized that the evolution individuals with high developmental instability [22], low of single traits cannot be understood in isolation when heterozygosity [23] or low condition [15,24] have lower pleiotropy is present. Widespread pleiotropy causes the fitness than do other individuals in the population. Under- appearance of stabilizing selection on metric traits ow- standing of the evolution of focal traits ultimately depends ing to joint effects with fitness, and results in the genetic on their genetic covariation with fitness [25]. Therefore, variation being concentrated in relatively few combina- new, general approaches, that are applicable across a tions of the measured traits. In this review, we show range of empirical systems, are required to characterize how trait combinations with high levels of genetic vari- how traits co-vary genetically with fitness. ation can be used to uncover fitness optima that are Here, we outline the theoretical justification for, and defined by apparent stabilizing selection. Defining fit- empirical application of, a new approach to the study of ness optima in this way could provide one avenue by how traits co-vary with fitness and the subsequent charac- which researchers can overcome the problem posed by terization of fitness optima. Our approach rests on recogniz- measuring the myriad of traits that must influence fit- ing two general consequences of widespread pleiotropy that ness, or by measuring total fitness itself. underlie theoretical explanations of the maintenance of genetic variance [3,4,9,10]. First, pleiotropy causes the ap- Multivariate evolution and the problem of measuring pearance of stabilizing selection on metric traits (see Glos- fitness sary) as a consequence of joint effects on these metric traits A fundamental challenge in evolutionary biology remains and on traits that directly affect fitness [3]. Second, pleiot- the characterization of multivariate phenotypes [1], their ropy restricts genetic variance in traits to a subspace of the underlying genetic basis [2–4] and how selection acts on multivariate phenotype, causing most of the genetic vari- these complex phenotypes [5,6]. Difficulties in measuring ance to be associated with just a few combinations of the complex, high-dimensional multivariate phenotypes and measured traits [10,14]. We argue that these two general in determining their genetic basis, have contributed to an consequences of pleiotropy cause the trait combinations empirical focus on single traits and their bivariate relation- associated with the most multivariate genetic variance to ships. This limited focus has led to incomplete genetic and be informative metrics of how individuals deviate from the evolutionary interpretations of empirical data [7,8], and to fitness optimum. We detail empirical approaches that can be a disconnect between empirical data and theoretical mod- taken to undercover fitness optima through consideration of els of evolution, which explicitly emphasize the importance these trait combinations. of multivariate relationships among traits [3,4,9–12]. Re- cent developments in characterizing multivariate pheno- Glossary types and genetic variation are beginning to equip empiricists with the means to bridge this divide [1,8,13,14]. Apparent stabilizing selection: a measured trait does not directly affect fitness and, therefore, is not directly under selection; however, pleiotropic covariation The need to describe multivariate phenotypes adequate- with traits that do directly affect fitness generates the appearance of selection ly is part of the greater challenge in evolutionary biology on that trait; also referred to as indirect stabilizing selection. posed by the problem of measuring fitness [15,16]. Fitness gmax: the first eigenvector of the additive genetic variance–covariance matrix, G. The coefficients of this vector represent an index of the linear combination is highly complex, with numerous component traits con- of measured traits associated with the greatest genetic variance, and can be tributing to lifetime reproductive success. Measuring the applied to either phenotypic trait values or breeding values to generate fitness of individuals is, and probably will remain, beyond phenotypic or genetic scores. Hidden pleiotropic effects: the pleiotropic relationship between a measured the logistical capability of most empirical systems. Devel- trait and an unmeasured trait, which can generate the appearance of stabilizing opmental instability [17], heterozygosity [18,19] and con- selection on the measured trait even in the absence of any direct effect of the trait on fitness. dition [20,21] have each been suggested as measures that Metric trait: a measured trait that exhibits continuous variation. capture genome-wide aspects of fitness variation, circum- Multivariate phenotype: a phenotype composed of multiple traits. venting the need to measure the fitness of individuals Mutation bias: the propensity of mutations to change the phenotype in a particular direction. directly. However, there is weak or equivocal evidence that Real stabilizing selection: variance-reducing selection acting directly on the measured trait; also referred to as direct stabilizing selection. Corresponding author: McGuigan, K. ([email protected]). 22 0169-5347/$ – see front matter ß 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.tree.2010.10.008 Trends in Ecology and Evolution, January 2011, Vol. 26, No. 1 Opinion Trends in Ecology and Evolution January 2011, Vol. 26, No. 1 Pleiotropy and apparent stabilizing selection acting directly on the focal traits. Owing to the intractability The extent of mutation bias is expected to differ between of measuring large numbers of traits [1], this expectation of metric traits and fitness itself. Mutations will tend to widespread apparent (rather than real) stabilizing selection increase or decrease the value of a metric trait with equal remains largely untested (but see [27]). frequency, but will decrease fitness more often than they The presence of widespread pleiotropy predicts another increase it [26]. When mutations have pleiotropic effects on aspect of selection on multiple traits that is not obvious the focal metric trait and on fitness, the metric trait will from estimates of the strength of selection for each trait in appear to be associated with fitness even when it does not isolation (i.e. the quadratic selection gradients along the make a direct phenotypic contribution to lifetime repro- diagonal of g, Box 1) [4]. Correlational selection between ductive success. The deleterious fitness effects of pleiotro- pairs of traits (the off-diagonal elements of g) indicates that pic mutations thus generate apparent stabilizing selection selection on one trait is not independent of selection on on focal metric traits [3,4,9]. That is, genotypes with ex- another. If real stabilizing selection occurred on all pheno- treme values of the metric trait are likely to carry more typic traits independently, individuals would deviate from mutations, each with deleterious pleiotropic effects on the optimum phenotype for many reasons and, consequent- fitness, resulting in selection for intermediate values of ly, overall fitness (summed across all traits) would be the metric trait. A substantial proportion of the selection unrealistically low [10]. The degree of non-independence observed on a focal metric trait is therefore likely to have of selection on multiple traits is revealed by the eigenvec- been generated through hidden pleiotropic effects on other tors of g [6], which describe the independent linear trait traits under selection and, ultimately, on fitness itself [3,5]. combinations that are under strong (or weak) selection. If all traits could be measured, real (direct) and apparent Such analyses support the expectation that selection can- stabilizing selection could be readily distinguished using not be acting independently on individual traits; stabiliz- multivariate selection analysis (Box 1). However, in the ing selection is stronger on some trait combinations than more general situation where relatively few traits are mea- on others, and much stronger on such multivariate trait sured, selection acting on unmeasured traits that directly combinations than on individual traits [28] (in the example affect fitness, and are correlated with the focal (measured) in Box 1, selection on the major axis of g is 2.5 times greater traits, will be misconstrued as real stabilizing selection than on individual traits). Box 1. Apparent stabilizing selection on metric traits A change in the phenotypic variance of a trait (zi) as a consequence of As an example of apparent stabilizing selection, imagine three traits stabilizing (or disruptive) selection can be measured using the (zi, zj and zk) are all under univariate stabilizing selection, with quadratic selection differential (Equation I) [5]: quadratic selection differentials of 0.05, 0.05 and 0.1, respectively, so that zk experiences twice the amount of stabilizing selection as the 2 2 2 C i ¼ s À s þ s ; [Eqn I] other two traits. All traits have the same phenotypic variance, and are zi zi phenotypically correlated to each other to the same moderate degree correcting the difference
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]
  • 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]
  • 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]
  • 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]
  • An Evolutionary Perspective on Physical Attractiveness
    Evolutionary Anthropology 97 An Evolutionary Perspective on Physical Attractiveness DOUG JONES Everyday experience suggests that physical attractiveness is important in per- to others, and that mate choices based sonal-and especially sexual-relationships. This impression is confirmed by a on these preferences have evolution- large body of social psychological research.’ z2 Cross-cultural surveys and ethno- ary consequences. However, he did graphic accounts show that concern with the attractiveness of potential mates is not take up the question of where pref- also common in non-Westernsocietiesand in tribal and peasant cultures3 However, erences come from in the first place - social psychologists and anthropologists have often had a hard time explaining why e.g., why peahens prefer peacocks attractiveness should count for so much, or why some features rather than others with large and showy trains. In recent should seem particularly attractive. The theoretical difficulties in accounting for work on sexual selection and mate physical attraction are brought out in a Brazilian saying, “Beleza n2o p6e na mesa” choice,6,7 this question occupies a cen- (“Good looks don’t put anything on the table”), which points to the absence of any tral place. This work asks how natural evident practical advantage to choosing an attractive mate. Faced with these diffi- selection might affect mating prefer- culties, a growing number of researchers in biology, psychology, and anthropology ences and why one set of mating pref- have turned to the modern theory of sexual selection, which has been highly suc- erences might lead to greater cessful in explaining nonhuman animals’ attractions to traits of no direct ecological reproductive success than another.
    [Show full text]
  • Uncovering the Genetic Signature of Quantitative Trait Evolution with Replicated Time Series Data
    Heredity (2017) 118, 42–51 & 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved 0018-067X/17 www.nature.com/hdy ORIGINAL ARTICLE Uncovering the genetic signature of quantitative trait evolution with replicated time series data SU Franssen, R Kofler and C Schlötterer The genetic architecture of adaptation in natural populations has not yet been resolved: it is not clear to what extent the spread of beneficial mutations (selective sweeps) or the response of many quantitative trait loci drive adaptation to environmental changes. Although much attention has been given to the genomic footprint of selective sweeps, the importance of selection on quantitative traits is still not well studied, as the associated genomic signature is extremely difficult to detect. We propose ‘Evolve and Resequence’ as a promising tool, to study polygenic adaptation of quantitative traits in evolving populations. Simulating replicated time series data we show that adaptation to a new intermediate trait optimum has three characteristic phases that are reflected on the genomic level: (1) directional frequency changes towards the new trait optimum, (2) plateauing of allele frequencies when the new trait optimum has been reached and (3) subsequent divergence between replicated trajectories ultimately leading to the loss or fixation of alleles while the trait value does not change. We explore these 3 phase characteristics for relevant population genetic parameters to provide expectations for various experimental evolution designs. Remarkably, over a broad range of parameters the trajectories of selected alleles display a pattern across replicates, which differs both from neutrality and directional selection. We conclude that replicated time series data from experimental evolution studies provide a promising framework to study polygenic adaptation from whole-genome population genetics data.
    [Show full text]
  • Biol2007 - Evolution of Quantitative Characters
    1 BIOL2007 - EVOLUTION OF QUANTITATIVE CHARACTERS How do evolutionary biologists measure variation in a typical quantitative character? Let’s use beak size in birds as a typical example. Phenotypic variation (Vp) in a quantitative character Some of the variation in beak size is caused by environmental factors (VE). Some of the variation is caused by genetic factors (VG). If there was no variation in genotype between birds then individuals would differ in beak size only because of different rearing environments. Quantitative geneticists think in terms of how the value of a character in an individual compares to the mean value of the character in the population. The population mean is taken to be a neutral measure and then particular phenotypes are increases or decreases from that value. AT LEVEL OF INDIVIDUAL Phenotype = genotype + environment P = G + E AT LEVEL OF POPULATION Phenotypic variance = genotypic variance + environmental variance VP = VG + VE Genotypic variance is divided into additive, dominance and interaction components VG = VA + VD + V I VA = Additive variance – due to the additive effects of individual alleles (inherited) VD = Dominance variance - reflect the combinations of alleles at each locus (homo- versus (homozygotes versus hetero-zygotes) in any given generation but are not inherited by offspring. An intra-locus effect. VI = Interaction/epistatic variance - reflect epistatic interactions between alleles at different loci. Again not passed onto offspring; they depend on particular combinations of genes in a given generation and are not inherited by offspring. An inter-locus effect. ___________________________________________________________ The following section (italicised) provides the alebgra to backup my assertion that VD and VI are not heritable.
    [Show full text]
  • Directional Selection Can Drive the Evolution of Modularity in Complex Traits
    Directional selection can drive the evolution of modularity in complex traits Diogo Melo1 and Gabriel Marroig Departamento de Genética e Biologia Evolutiva, Instituto de Biociências, Universidade de São Paulo, Sao Paulo, SP 05508-090, Brazil Edited by Stevan J. Arnold, Oregon State University, Corvallis, OR, and accepted by the Editorial Board December 2, 2014 (received for review December 9, 2013) Modularity is a central concept in modern biology, providing a promotes changes in only one trait of a module, the other traits powerful framework for the study of living organisms on many within this module will suffer an indirect selection pressure and organizational levels. Two central and related questions can be change as well, even if this response leads to lower fitness (8). This posed in regard to modularity: How does modularity appear in the indirect response in other traits is due to their genetic correlation first place, and what forces are responsible for keeping and/or with the selected trait. Understanding how traits become associated, changing modular patterns? We approached these questions using or correlated, is therefore a central question in evolutionary biology. a quantitative genetics simulation framework, building on pre- The question of how modular patterns evolve in each level of vious results obtained with bivariate systems and extending them complexity is still open to intense scrutiny (9–11). In morpho- to multivariate systems. We developed an individual-based model logical systems, one condition for the evolution of variational capable of simulating many traits controlled by many loci with pattern is the existence of genetic variation in the association variable pleiotropic relations between them, expressed in pop- between traits in a population.
    [Show full text]
  • Mutational Pleiotropy and the Strength of Stabilizing Selection Within and Between
    Genetics: Early Online, published on February 1, 2018 as 10.1534/genetics.118.300776 1 2 Mutational pleiotropy and the strength of stabilizing selection within and between 3 functional modules of gene expression 4 5 6 7 Julie M. Collet*1, Katrina McGuigan, Scott L. Allen, Stephen F. Chenoweth, Mark W. Blows 8 School of Biological Sciences, The University of Queensland, 4072, Australia 9 1current affiliation: CBGP, INRA, CIRAD, IRD, Montpellier SupAgro, Univ. Montpellier, 10 Montpellier, France 11 12 Data Archival Location: NCBI Gene Expression Omnibus (N lines: GSE49815; S lines: 13 GSE54777). 14 15 1 Copyright 2018. 16 Variational and functional modularity 17 Keywords: modularity, pleiotropy, genotype-phenotype map, Drosophila serrata, gene 18 expression 19 * corresponding author: [email protected] 20 ABSTRACT 21 Variational modules, sets of pleiotropically covarying traits, affect phenotypic evolution, and 22 therefore are predicted to reflect functional modules, such that traits within a variational 23 module also share a common function. Such an alignment of function and pleiotropy is 24 expected to facilitate adaptation by reducing the deleterious effects of mutations, and 25 allowing coordinated evolution of functionally related sets of traits. Here, we adopt a high- 26 dimensional quantitative genetic approach using a large number of gene expression traits in 27 Drosophila serrata to test whether functional grouping, defined by GO terms, predicts 28 variational modules. Mutational or standing genetic covariance was significantly greater 29 than among randomly grouped sets of genes for 38% of our functional groups, indicating 30 that GO terms can predict variational modularity to some extent. We estimated stabilizing 31 selection acting on mutational covariance to test the prediction that functional pleiotropy 32 would result in reduced deleterious effects of mutations within functional modules.
    [Show full text]