The Contemporary Evolution of Fitness

2018 ◽  
Vol 49 (1) ◽  
pp. 457-476 ◽  
Author(s):  
Andrew P. Hendry ◽  
Daniel J. Schoen ◽  
Matthew E. Wolak ◽  
Jane M. Reid
Keyword(s):  
Genetic Variance ◽  
Evolutionary Dynamics ◽  
Additive Genetic Variance ◽  
Deleterious Mutations ◽  
Contemporary Evolution ◽  
Evolutionary Potential ◽  
Empirical Estimates ◽  
Evolutionary Rescue ◽  
Proportional Change ◽  
Mean Fitness

The rate of evolution of population mean fitness informs how selection acting in contemporary populations can counteract environmental change and genetic degradation (mutation, gene flow, drift, recombination). This rate influences population increases (e.g., range expansion), population stability (e.g., cryptic eco-evolutionary dynamics), and population recovery (i.e., evolutionary rescue). We review approaches for estimating such rates, especially in wild populations. We then review empirical estimates derived from two approaches: mutation accumulation (MA) and additive genetic variance in fitness (IAw). MA studies inform how selection counters genetic degradation arising from deleterious mutations, typically generating estimates of <1% per generation. IAw studies provide an integrated prediction of proportional change per generation, nearly always generating estimates of <20% and, more typically, <10%. Overall, considerable, but not unlimited, evolutionary potential exists in populations facing detrimental environmental or genetic change. However, further studies with diverse methods and species are required for more robust and general insights.

scholarly journals Estimation of Deleterious-Mutation Parameters in Natural Populations

Genetics ◽  
1996 ◽  
Vol 144 (1) ◽  
pp. 349-360 ◽  
Author(s):  
Hong-Wen Deng ◽  
Michael Lynch
Keyword(s):  
Genetic Variance ◽  
Deleterious Mutation ◽  
Natural Populations ◽  
Breeding Systems ◽  
Deleterious Mutations ◽  
Empirical Estimates ◽  
Mean Fitness ◽  
The Mean ◽  
New Mutations

Abstract The rate and average effects of spontaneous deleterious mutations are important determinants of the evolution of breeding systems and of the vulnerability of small populations to extinction. Nevertheless, few attempts have been made to estimate the properties of such mutations, and those studies that have been performed have been extremely labor intensive, relying on long-term, laboratory mutation-accumulation experiments. We present an alternative to the latter approach. For populations in which the genetic variance for fitness is a consequence of selection-mutation balance, the mean fitness and genetic variance of fitness in outbred and inbred generations can be expressed as simple functions of the genomic mutation rate, average homozygous effect and average dominance coefficient of new mutations. Using empirical estimates for the mean and genetic variance of fitness, these expressions can then be solved to obtain joint estimates of the deleterious-mutation parameters. We employ computer simulations to evaluate the degree of bias of the estimators and present some general recommendations on the application of the technique. Our procedures provide some hope for obtaining estimates of the properties of deleterious mutations from a wide phylogenetic range of species as well as a mechanism for testing the validity of alternative models for the maintenance of genetic variance for fitness.

scholarly journals Additive genetic variance for lifetime fitness and the capacity for adaptation in an annual plant

2019 ◽  
Author(s):  
Mason W. Kulbaba ◽  
Seema N. Sheth ◽  
Rachel E. Pain ◽  
Vince M. Eckhart ◽  
Ruth G. Shaw
Keyword(s):  
Genetic Variance ◽  
Experimental Approach ◽  
Additive Genetic Variance ◽  
Chamaecrista Fasciculata ◽  
Evolutionary Rescue ◽  
Declining Populations ◽  
In The Wild ◽  
Population Sustainability ◽  
Mean Fitness ◽  
Fisher’S Fundamental Theorem

AbstractThe immediate capacity for adaptation under current environmental conditions is directly proportional to the additive genetic variance for fitness, VA(W). Mean absolute fitness, , is predicted to change at the rate , according to Fisher’s Fundamental Theorem of Natural Selection. Despite ample research evaluating degree of local adaptation, direct assessment of VA(W) and the capacity for ongoing adaptation is exceedingly rare. We estimated VA(W) and in three pedigreed populations of annual Chamaecrista fasciculata, over three years in the wild. Contrasting with common expectations, we found significant VA(W) in all populations and years, predicting increased mean fitness in subsequent generations (0.83 to 6.12 seeds per individual). Further, we detected two cases predicting “evolutionary rescue”, where selection on standing VA(W) was expected to increase fitness of declining populations ( < 1.0) to levels consistent with population sustainability and growth. Within populations, interannual differences in genetic expression of fitness were striking. Significant genotype-by-year interactions reflected modest correlations between breeding values across years (all r < 0.490), indicating temporally variable selection at the genotypic level; that could contribute to maintaining VA(W). By directly estimating VA(W) and total lifetime , our study presents an experimental approach for studies of adaptive capacity in the wild.

scholarly journals A guide to using a multiple-matrix animal model to disentangle genetic and nongenetic causes of phenotypic variance

2018 ◽  
Author(s):  
Caroline E. Thomson ◽  
Isabel S. Winney ◽  
Oceane C. Salles ◽  
Benoit Pujol
Keyword(s):  
Animal Model ◽  
Genetic Variance ◽  
Genetic Relatedness ◽  
Additive Genetic Variance ◽  
Phenotypic Traits ◽  
Phenotypic Variance ◽  
Data Types ◽  
Evolutionary Potential ◽  
Recent Developments

AbstractNon-genetic influences on phenotypic traits can affect our interpretation of genetic variance and the evolutionary potential of populations to respond to selection, with consequences for our ability to predict the outcomes of selection. Long-term population surveys and experiments have shown that quantitative genetic estimates are influenced by nongenetic effects, including shared environmental effects, epigenetic effects, and social interactions. Recent developments to the “animal model” of quantitative genetics can now allow us to calculate precise individual-based measures of non-genetic phenotypic variance. These models can be applied to a much broader range of contexts and data types than used previously, with the potential to greatly expand our understanding of nongenetic effects on evolutionary potential. Here, we provide the first practical guide for researchers interested in distinguishing between genetic and nongenetic causes of phenotypic variation in the animal model. The methods use matrices describing individual similarity in nongenetic effects, analogous to the additive genetic relatedness matrix. In a simulation of various phenotypic traits, accounting for environmental, epigenetic, or cultural resemblance between individuals reduced estimates of additive genetic variance, changing the interpretation of evolutionary potential. These variances were estimable for both direct and parental nongenetic variances. Our tutorial outlines an easy way to account for these effects in both wild and experimental populations. These models have the potential to add to our understanding of the effects of genetic and nongenetic effects on evolutionary potential. This should be of interest both to those studying heritability, and those who wish to understand nongenetic variance.

scholarly journals Deleterious mutations, apparent stabilizing selection and the maintenance of quantitative variation.

Genetics ◽  
1992 ◽  
Vol 132 (2) ◽  
pp. 603-618 ◽  
Author(s):  
A S Kondrashov ◽  
M Turelli
Keyword(s):  
Quantitative Trait ◽  
Genetic Variance ◽  
Additive Genetic Variance ◽  
Pleiotropic Effects ◽  
Direct Selection ◽  
Selection Function ◽  
Stabilizing Selection ◽  
Deleterious Mutations ◽  
Additive Variance ◽  
Deleterious Alleles

Abstract Apparent stabilizing selection on a quantitative trait that is not causally connected to fitness can result from the pleiotropic effects of unconditionally deleterious mutations, because as N. Barton noted, "...individuals with extreme values of the trait will tend to carry more deleterious alleles...." We use a simple model to investigate the dependence of this apparent selection on the genomic deleterious mutation rate, U; the equilibrium distribution of K, the number of deleterious mutations per genome; and the parameters describing directional selection against deleterious mutations. Unlike previous analyses, we allow for epistatic selection against deleterious alleles. For various selection functions and realistic parameter values, the distribution of K, the distribution of breeding values for a pleiotropically affected trait, and the apparent stabilizing selection function are all nearly Gaussian. The additive genetic variance for the quantitative trait is kQa2, where k is the average number of deleterious mutations per genome, Q is the proportion of deleterious mutations that affect the trait, and a2 is the variance of pleiotropic effects for individual mutations that do affect the trait. In contrast, when the trait is measured in units of its additive standard deviation, the apparent fitness function is essentially independent of Q and a2; and beta, the intensity of selection, measured as the ratio of additive genetic variance to the "variance" of the fitness curve, is very close to s = U/k, the selection coefficient against individual deleterious mutations at equilibrium. Therefore, this model predicts appreciable apparent stabilizing selection if s exceeds about 0.03, which is consistent with various data. However, the model also predicts that beta must equal Vm/VG, the ratio of new additive variance for the trait introduced each generation by mutation to the standing additive variance. Most, although not all, estimates of this ratio imply apparent stabilizing selection weaker than generally observed. A qualitative argument suggests that even when direct selection is responsible for most of the selection observed on a character, it may be essentially irrelevant to the maintenance of variation for the character by mutation-selection balance. Simple experiments can indicate the fraction of observed stabilizing selection attributable to the pleiotropic effects of deleterious mutations.

scholarly journals Between migration load and evolutionary rescue: dispersal, adaptation and the response of spatially structured populations to environmental change

2014 ◽  
Vol 281 (1778) ◽  
pp. 20132795 ◽  
Author(s):  
Elizabeth C. Bourne ◽  
Greta Bocedi ◽  
Justin M. J. Travis ◽  
Robin J. Pakeman ◽  
Rob W. Brooker ◽  
...  
Keyword(s):  
Evolutionary Dynamics ◽  
Structured Populations ◽  
Evolutionary Potential ◽  
Beneficial Effects ◽  
Individual Fitness ◽  
Spatially Structured Populations ◽  
Local Selection ◽  
Evolutionary Response ◽  
Evolutionary Rescue ◽  
Opposing Effects

The evolutionary potential of populations is mainly determined by population size and available genetic variance. However, the adaptability of spatially structured populations may also be affected by dispersal: positively by spreading beneficial mutations across sub-populations, but negatively by moving locally adapted alleles between demes. We develop an individual-based, two-patch, allelic model to investigate the balance between these opposing effects on a population's evolutionary response to rapid climate change. Individual fitness is controlled by two polygenic traits coding for local adaptation either to the environment or to climate. Under conditions of selection that favour the evolution of a generalist phenotype (i.e. weak divergent selection between patches) dispersal has an overall positive effect on the persistence of the population. However, when selection favours locally adapted specialists, the beneficial effects of dispersal outweigh the associated increase in maladaptation for a narrow range of parameter space only (intermediate selection strength and low linkage among loci), where the spread of beneficial climate alleles is not strongly hampered by selection against non-specialists. Given that local selection across heterogeneous and fragmented landscapes is common, the complex effect of dispersal that we describe will play an important role in determining the evolutionary dynamics of many species under rapidly changing climate.

VERY LOW ADDITIVE GENETIC VARIANCE AND EVOLUTIONARY POTENTIAL IN MULTIPLE POPULATIONS OF TWO RAINFOREST DROSOPHILA SPECIES

Evolution ◽  
2006 ◽  
Vol 60 (5) ◽  
pp. 1104 ◽  
Author(s):  
Vanessa M. Kellermann ◽  
Belinda van Heerwaarden ◽  
Ary A. Hoffmann ◽  
Carla M. Sgrò
Keyword(s):  
Genetic Variance ◽  
Additive Genetic Variance ◽  
Drosophila Species ◽  
Evolutionary Potential ◽  
Multiple Populations

scholarly journals Introduced populations of ragweed show as much evolutionary potential as native populations

2018 ◽  
Author(s):  
Brechann V. McGoey ◽  
John R. Stinchcombe
Keyword(s):  
Genetic Architecture ◽  
Genetic Variance ◽  
Additive Genetic Variance ◽  
Ambrosia Artemisiifolia ◽  
Empirical Literature ◽  
Ecological Problem ◽  
Adaptive Potential ◽  
Evolutionary Potential ◽  
Introduced Populations ◽  
Native Populations

AbstractInvasive species are a global economic and ecological problem. They also offer an opportunity to understand evolutionary processes in a colonizing context. The impacts of evolutionary factors, such as genetic variation, on the invasion process are increasingly appreciated but there remain gaps in the empirical literature. The adaptive potential of populations can be quantified using genetic variance-covariance matrices (G), which encapsulate the heritable genetic variance in a population. Here, we use a multivariate, Bayesian approach to assess the adaptive potential of introduced populations of ragweed, Ambrosia artemisiifolia, a serious allergen and agricultural weed. We compared several aspects of genetic architecture and the structure of G matrices between three native and three introduced populations, based on data collected in the field in a common garden experiment. We find moderate differences in the quantitative genetic architecture among populations, but we do not find that introduced populations suffer from a limited adaptive potential compared to native populations. Ragweed has an annual life history, is an obligate outcrosser, and produces billions of seeds and pollen grains per. These characteristics, combined with the significant additive genetic variance documented here, suggest ragweed will be able to respond quickly to selection pressures in both its native and introduced ranges.

scholarly journals Linkage and the limits to natural selection.

Genetics ◽  
1995 ◽  
Vol 140 (2) ◽  
pp. 821-841 ◽  
Author(s):  
N H Barton
Keyword(s):  
Genetic Variance ◽  
Additive Genetic Variance ◽  
Large Population ◽  
Substantial Effect ◽  
Relative Fitness ◽  
Fixation Probability ◽  
Deleterious Mutations ◽  
Effective Population ◽  
Probability Of Fixation ◽  
General Method

Abstract The probability of fixation of a favorable mutation is reduced if selection at other loci causes inherited variation in fitness. A general method for calculating the fixation probability of an allele that can find itself in a variety of genetic backgrounds is applied to find the effect of substitutions, fluctuating polymorphisms, and deleterious mutations in a large population. With loose linkage, r, the effects depend on the additive genetic variance in relative fitness, var(W), and act by reducing effective population size by (N/Ne) = 1 + var(W)/2r2. However, tightly linked loci can have a substantial effect not predictable from Ne. Linked deleterious mutations reduce the fixation probability of weakly favored alleles by exp (-2U/R), where U is the total mutation rate and R is the map length in Morgans. Substitutions can cause a greater reduction: an allele with advantage s &lt; scrit = (pi 2/6) loge (S/s) [var(W)/R] is very unlikely to be fixed. (S is the advantage of the substitution impeding fixation.) Fluctuating polymorphisms at many (n) linked loci can also have a substantial effect, reducing fixation probability by exp [square root of 2Kn var(W)/R] [K = -1/E((u-u)2/uv) depending on the frequencies (u,v) at the selected polymorphisms]. Hitchhiking due to all three kinds of selection may substantially impede adaptation that depends on weakly favored alleles.

scholarly journals The genetic structure of natural populations of Drosophila melanogaster. XXIV. Effects of hybrid dysgenesis on the components of genetic variance of variability.

Genetics ◽  
1991 ◽  
Vol 127 (3) ◽  
pp. 545-552
Author(s):  
D S Suh ◽  
T Mukai
Keyword(s):  
Drosophila Melanogaster ◽  
Population Genetic ◽  
Genetic Parameters ◽  
Genetic Variance ◽  
Additive Genetic Variance ◽  
Natural Populations ◽  
Deleterious Mutations ◽  
Degree Of Dominance ◽  
Population Genetic Parameters ◽  
P Type

Abstract Eight hundred second chromosomes were extracted from the Ishigakijima population, one of the southernmost populations of Drosophila melanogaster in Japan. Half of them were extracted in Native cytoplasm (P-type), and half in Foreign cytoplasm (M-type). Various population-genetic parameters, including the frequency of lethal-carrying second chromosomes (Q = 0.235 for the Native; 0.218 for the Foreign), the allelism rate of lethal second chromosome (Ic = 0.0217 for the Native; 0.0134 for the Foreign), the homozygous detrimental and lethal loads (D = 0.179 for the Native; 0.270 for the Foreign; L = 0.262 for the Native; 0.240 for the Foreign), the average degree of dominance of mildly deleterious mutations (ĥE = 0.244 for the Native; 0.208 for the Foreign), and the components of genetic variance for viability [additive (sigma A2) and dominance (sigma D2)](ŝigma A2 = 0.0187 for the Native; 0.0172 for the Foreign; ŝigma D2 = 0.0005 for the Native; 0.0009 for the Foreign) were estimated. The data indicate that D was significantly larger and hE was significantly smaller in the Foreign cytoplasm. However, the estimates of additive and dominance variances were not significantly different between the two cytoplasms. The additive genetic variance for viability in the Ishigakijima population was greater than expected on the basis of mutation-selection balance confirming previous studies on papers of D. melanogaster in warm climates.

Sign in / Sign up

Export Citation Format

Share Document