scholarly journals Characterizing the evolution of genetic variance using genetic covariance tensors

2009 ◽  
Vol 364 (1523) ◽  
pp. 1567-1578 ◽  
Author(s):  
Emma Hine ◽  
Stephen F. Chenoweth ◽  
Howard D. Rundle ◽  
Mark W. Blows
Keyword(s):  
Genetic Variance ◽  
Natural Populations ◽  
Covariance Structure ◽  
Evolutionary Genetics ◽  
Geometric Framework ◽  
Genetic Covariance ◽  
Sexually Selected Traits ◽  
Selected Traits ◽  
Higher Order Tensors ◽  
The Individual

Determining how genetic variance changes under selection in natural populations has proved to be a very resilient problem in evolutionary genetics. In the same way that understanding the availability of genetic variance within populations requires the simultaneous consideration of genetic variance in sets of functionally related traits, determining how genetic variance changes under selection in natural populations will require ascertaining how genetic variance–covariance ( G ) matrices evolve. Here, we develop a geometric framework using higher-order tensors, which enables the empirical characterization of how G matrices have diverged among populations. We then show how divergence among populations in genetic covariance structure can then be associated with divergence in selection acting on those traits using key equations from evolutionary theory. Using estimates of G matrices of eight male sexually selected traits from nine geographical populations of Drosophila serrata , we show that much of the divergence in genetic variance occurred in a single trait combination, a conclusion that could not have been reached by examining variation among the individual elements of the nine G matrices. Divergence in G was primarily in the direction of the major axes of genetic variance within populations, suggesting that genetic drift may be a major cause of divergence in genetic variance among these populations.

The causes and consequences of ornament variation in a natural population

2019 ◽  
Author(s):  
Annabel Ralph ◽  
Terry Burke ◽  
Shinichi Nakagawa ◽  
Alfredo Sánchez-Tójar ◽  
Julia Schroeder
Keyword(s):  
Sexual Selection ◽  
Evolutionary Biology ◽  
Natural Populations ◽  
Size Variation ◽  
Evolutionary Potential ◽  
House Sparrows ◽  
Sexually Selected Traits ◽  
Evolutionary Response ◽  
Significant Heritability ◽  
Selected Traits

The role of sexual selection in natural populations has long been the subject of debate in evolutionary biology. Ornaments are sexually selected traits, which means they should vary within a population, have a genetic basis, and be associated with fitness. Despite evidence of ornaments meeting these criteria, evolutionary responses to sexual selection are rare in nature. This study focuses on two ornaments in a population of house sparrows; the plumage badge has been well-studied but remains poorly understood and the mask has been largely neglected in the literature. Using quantitative genetic techniques, we estimate the heritability of both traits and test for age-dependency of the heritability estimates. We also estimate the strength and direction of any selection acting upon the traits. We found that both ornaments have low, significant heritability, which does not vary with age. Selection only occurs in a small number of years, although when it does it is positive in both ornaments. We also found that early social environment plays a role in badge size variation. The results of this study suggest that an evolutionary response in the ornaments of this population is unlikely, but we highlight the importance of long-term research to improve our understanding of evolution in natural populations. Studies like these will add to our understanding of sexual selection, the causes of trait variation and the evolutionary potential of traits, which could help us to predict how populations will evolve.

scholarly journals Gene-by-Crisis Interaction for Optimism and Meaning in Life: The Effects of the COVID-19 Pandemic

2021 ◽  
Author(s):  
Lianne P. de Vries ◽  
Margot P. van de Weijer ◽  
Dirk H. M. Pelt ◽  
Lannie Ligthart ◽  
Gonneke Willemsen ◽  
...  
Keyword(s):  
Individual Differences ◽  
Meaning In Life ◽  
Virus Disease ◽  
Genetic Correlations ◽  
Covariance Structure ◽  
Well Being ◽  
Specific Response ◽  
Negative Effects ◽  
Genetic Covariance ◽  
The Individual

AbstractThe corona virus disease 2019 (COVID-19) pandemic and the restrictions to reduce the spread of the virus has had a large impact on daily life. We investigated the individual differences in the effect of the COVID-19 pandemic and first lockdown on optimism and meaning in life in a sample from the Netherlands Twin Register. Participants completed surveys before (N = 9964, Mean age: 48.2, SD = 14.4) and during the first months of the pandemic (i.e. April–May 2020, N = 17,464, Mean age: 44.6 SD = 14.8), with a subsample completing both surveys (N = 6461, Mean age T1: 48.8, SD = 14.5). We applied genetic covariance structure models to twin data to investigate changes in the genetic architecture of the outcome traits due to the pandemic and the interaction of genes with the environmental exposure. Although 56% and 35% of the sample was negatively affected by the pandemic in their optimism and meaning in life, many participants were stable (32% and 43%) or even showed increased optimism and meaning in life (11% and 22%). Subgroups, specifically women, higher educated people, and people with poorer health, experienced larger negative effects. During the first months of the pandemic, slightly lower heritability estimates for optimism and meaning in life (respectively 20% and 25%) were obtained compared to pre-pandemic (respectively 26% and 32%), although confidence intervals overlap. The lower than unity genetic correlations across time (.75 and .63) suggest gene-environment interactions, where the expression of genes that influence optimism and meaning in life differs before and during the pandemic. The COVID-19 pandemic is a strong exposure that leads to imbalanced effects on the well-being of individuals. Some people decrease in well-being, while others get more optimistic and consider their lives as more meaningful during the pandemic. These differences are partly explained by individual differences in genetic sensitivity to extreme environmental change. More knowledge on the person-specific response to specific environmental variables underlying these individual differences is urgently needed to prevent further inequality.

Geographical variation in the male intromittent organ of the Trinidadian guppy (Poecilia reticulata)

2000 ◽  
Vol 78 (9) ◽  
pp. 1674-1680 ◽  
Author(s):  
Clint D Kelly ◽  
Jean-Guy J Godin ◽  
Ghada Abdallah
Keyword(s):  
Phenotypic Variation ◽  
Poecilia Reticulata ◽  
Natural Populations ◽  
Fish Predation ◽  
Species Variation ◽  
Body Coloration ◽  
Sexually Selected Traits ◽  
Predation Intensity ◽  
Trinidadian Guppy ◽  
Selected Traits

Sexual selection may favour the evolution of elaborated genital traits in males, particularly when phenotypic variation in such traits results in corresponding variation in reproductive success among males in the population. Compared with insects, very little is known about the natural variation in any male genital trait, and its causes, in vertebrates. Here we report on variation in a male intromittent organ both within and between natural populations of a vertebrate, the Trinidadian guppy (Poecilia reticulata). Male guppies inseminate females using an intromittent organ called the gonopodium. We demonstrate that males from populations that have evolved under high fish-predation intensity have, on average, a relatively longer gonopodium than males originating from populations under low fish-predation intensity. Compared with body coloration, the gonopodium exhibited relatively low phenotypic variation, but nonetheless was within the range of known variation for sexually selected traits. The male gonopodium was positively allometric in general. To our knowledge, this is the first report of within-species variation in an intromittent organ and of a positive allometric relationship between male genitalia and body size in a vertebrate species. Our results suggest that the length of the male intromittent organ in the guppy is under selection, which varies geographically.

scholarly journals Evolutionary rates for multivariate traits: the role of selection and genetic variation

2014 ◽  
Vol 369 (1649) ◽  
pp. 20130252 ◽  
Author(s):  
William Pitchers ◽  
Jason B. Wolf ◽  
Tom Tregenza ◽  
John Hunt ◽  
Ian Dworkin
Keyword(s):  
Evolutionary Biology ◽  
Genetic Architecture ◽  
Genetic Variance ◽  
Evolutionary Rates ◽  
Phenotypic Traits ◽  
Sexually Selected Traits ◽  
Rates Of Evolution ◽  
Selected Traits ◽  
Multivariate Traits

A fundamental question in evolutionary biology is the relative importance of selection and genetic architecture in determining evolutionary rates. Adaptive evolution can be described by the multivariate breeders' equation ( ), which predicts evolutionary change for a suite of phenotypic traits ( ) as a product of directional selection acting on them ( β ) and the genetic variance–covariance matrix for those traits ( G ). Despite being empirically challenging to estimate, there are enough published estimates of G and β to allow for synthesis of general patterns across species. We use published estimates to test the hypotheses that there are systematic differences in the rate of evolution among trait types, and that these differences are, in part, due to genetic architecture. We find some evidence that sexually selected traits exhibit faster rates of evolution compared with life-history or morphological traits. This difference does not appear to be related to stronger selection on sexually selected traits. Using numerous proposed approaches to quantifying the shape, size and structure of G , we examine how these parameters relate to one another, and how they vary among taxonomic and trait groupings. Despite considerable variation, they do not explain the observed differences in evolutionary rates.

Estimation of Deleterious Genomic Mutation Parameters in Natural Populations by Accounting for Variable Mutation Effects Across Loci

Genetics ◽  
2002 ◽  
Vol 162 (3) ◽  
pp. 1487-1500 ◽  
Author(s):  
Hong-Wen Deng ◽  
Guimin Gao ◽  
Jin-Long Li
Keyword(s):  
Statistical Method ◽  
Mutation Rate ◽  
Genetic Variance ◽  
Natural Populations ◽  
Evolutionary Genetics ◽  
Simulation Studies ◽  
Fitness Effects ◽  
Mean Fitness ◽  
The Mean ◽  
Genomic Mutation

Abstract The genomes of all organisms are subject to continuous bombardment of deleterious genomic mutations (DGM). Our ability to accurately estimate various parameters of DGM has profound significance in population and evolutionary genetics. The Deng-Lynch method can estimate the parameters of DGM in natural selfing and outcrossing populations. This method assumes constant fitness effects of DGM and hence is biased under variable fitness effects of DGM. Here, we develop a statistical method to estimate DGM parameters by considering variable mutation effects across loci. Under variable mutation effects, the mean fitness and genetic variance for fitness of parental and progeny generations across selfing/outcrossing in outcrossing/selfing populations and the covariance between mean fitness of parents and that of their progeny are functions of DGM parameters: the genomic mutation rate U, average homozygous effect s, average dominance coefficient h, and covariance of selection and dominance coefficients cov(h, s). The DGM parameters can be estimated by the algorithms we developed herein, which may yield improved estimation of DGM parameters over the Deng-Lynch method as demonstrated by our simulation studies. Importantly, this method is the first one to characterize cov(h, s) for DGM.

scholarly journals Evolutionary rates for multivariate traits: the role of selection and genetic variation

2014 ◽  
Author(s):  
William Pitchers ◽  
Jason B. Wolf ◽  
Tom Tregenza ◽  
John Hunt ◽  
Ian Dworkin
Keyword(s):  
Evolutionary Biology ◽  
Genetic Architecture ◽  
Genetic Variance ◽  
Evolutionary Rates ◽  
Phenotypic Traits ◽  
Sexually Selected Traits ◽  
Rates Of Evolution ◽  
Selected Traits ◽  
Multivariate Traits

A fundamental question in evolutionary biology is the relative importance of selection and genetic architecture in determining evolutionary rates. Adaptive evolution can be described by the multivariate breeders' equation (Δz = Gβ), which predicts evolutionary change for a suite of phenotypic traits (Δz) as a product of directional selection acting on them (β) and the genetic variance-covariance matrix for those traits (G). Despite being empirically challenging to estimate, there are enough published estimates ofGandβto allow for synthesis of general patterns across species. We use published estimates to test the hypotheses that there are systematic differences in the rate of evolution among trait types, and that these differences are in part due to genetic architecture. We find evidence that sexually selected traits exhibit faster rates of evolution compared to life-history or morphological traits. This difference does not appear to be related to stronger selection on sexually selected traits. Using numerous proposed approaches to quantifying the shape, size and structure ofGwe examine how these parameters relate to one another, and how they vary among taxonomic and trait groupings. Despite considerable variation, they do not explain the observed differences in evolutionary rates.

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