scholarly journals Inferring the Joint Demographic History of Multiple Populations: Beyond the Diffusion Approximation

2017 ◽  
Author(s):  
Julien Jouganous ◽  
Will Long ◽  
Simon Gravel
Keyword(s):  
Diffusion Approximation ◽  
Sequence Data ◽  
Demographic History ◽  
Allele Frequencies ◽  
Human Sequence ◽  
Medical Study ◽  
Joint Frequency ◽  
Classical Models ◽  
History Of ◽  
Demographic Inference

AbstractUnderstanding variation in allele frequencies across populations is a central goal of population genetics. Classical models for the distribution of allele frequencies, using forward simulation, coalescent theory, or the diffusion approximation, have been applied extensively for demographic inference, medical study design, and evolutionary studies. Here we propose a tractable model of ordinary differential equations for the evolution of allele frequencies that is closely related to the diffusion approximation but avoids many of its limitations and approximations. We show that the approach is typically faster, more numerically stable, and more easily generalizable than the state-of-the-art software implementation of the diffusion approximation. We present a number of applications to human sequence data, including demographic inference with a five-population joint frequency spectrum and a discussion of the transferability of demographic histories across populations.

scholarly journals Inferring the Demographic History of Inbred Species from Genome-Wide SNP Frequency Data

2020 ◽  
Vol 37 (7) ◽  
pp. 2124-2136
Author(s):  
Paul D Blischak ◽  
Michael S Barker ◽  
Ryan N Gutenkunst
Keyword(s):  
Puma Concolor ◽  
Demographic History ◽  
Random Mating ◽  
Simulated Data ◽  
Conservation Agriculture ◽  
Model Fit ◽  
Parameter Estimates ◽  
History Of ◽  
Demographic Inference ◽  
Inbred Populations

Abstract Demographic inference using the site frequency spectrum (SFS) is a common way to understand historical events affecting genetic variation. However, most methods for estimating demography from the SFS assume random mating within populations, precluding these types of analyses in inbred populations. To address this issue, we developed a model for the expected SFS that includes inbreeding by parameterizing individual genotypes using beta-binomial distributions. We then take the convolution of these genotype probabilities to calculate the expected frequency of biallelic variants in the population. Using simulations, we evaluated the model’s ability to coestimate demography and inbreeding using one- and two-population models across a range of inbreeding levels. We also applied our method to two empirical examples, American pumas (Puma concolor) and domesticated cabbage (Brassica oleracea var. capitata), inferring models both with and without inbreeding to compare parameter estimates and model fit. Our simulations showed that we are able to accurately coestimate demographic parameters and inbreeding even for highly inbred populations (F = 0.9). In contrast, failing to include inbreeding generally resulted in inaccurate parameter estimates in simulated data and led to poor model fit in our empirical analyses. These results show that inbreeding can have a strong effect on demographic inference, a pattern that was especially noticeable for parameters involving changes in population size. Given the importance of these estimates for informing practices in conservation, agriculture, and elsewhere, our method provides an important advancement for accurately estimating the demographic histories of these species.

scholarly journals Measuring the degree of starshape in genealogies – summary statistics and demographic inference

2009 ◽  
Vol 91 (4) ◽  
pp. 281-292 ◽  
Author(s):  
KONRAD LOHSE ◽  
JEROME KELLEHER
Keyword(s):  
Sequence Data ◽  
Simple Algorithm ◽  
Likelihood Estimation ◽  
Likelihood Method ◽  
Summary Statistics ◽  
Full Likelihood ◽  
Tests Of Neutrality ◽  
History Of ◽  
Neutrality Tests ◽  
Demographic Inference

SummaryThe degree of starshape of a genealogy is readily detectable using summary statistics and can be taken as a surrogate for the effect of past demography and other non-neutral forces. Summary statistics such as Tajima's D and related measures are commonly used for this. However, it is well known that because of their neglect of the genealogy underlying a sample such neutrality tests are far from ideal. Here, we investigate the properties of two types of summary statistics that are derived by considering the genealogy: (i) genealogical ratios based on the number of mutations on the rootward branches, which can be inferred from sequence data using a simple algorithm and (ii) summary statistics that use properties of a perfectly star-shaped genealogy. The power of these measures to detect a history of exponential growth is compared with that of standard summary statistics and a likelihood method for the single and multi-locus case. Statistics that depend on pairwise measures such as Tajima's D have comparatively low power, being sensitive to the random topology of the underlying genealogy. When analysing multi-locus data, we find that the genealogical measures are most powerful. Provided reliable outgroup information is available they may constitute a useful alternative to full likelihood estimation and standard tests of neutrality.

scholarly journals The timing of human adaptation from Neanderthal introgression

2020 ◽  
Author(s):  
Sivan Yair ◽  
Kristin M. Lee ◽  
Graham Coop
Keyword(s):  
Demographic History ◽  
Low Frequency ◽  
Modern Human ◽  
Allele Frequencies ◽  
Population Divergence ◽  
Human Populations ◽  
Human Adaptation ◽  
Adaptive Introgression ◽  
History Of ◽  
Spatio Temporal

AbstractAdmixture has the potential to facilitate adaptation by providing alleles that are immediately adaptive in a new environment or by simply increasing the long term reservoir of genetic diversity for future adaptation. A growing number of cases of adaptive introgression are being identified in species across the tree of life, however the timing of selection, and therefore the importance of the different evolutionary roles of admixture, is typically unknown. Here, we investigate the spatio-temporal history of selection favoring Neanderthal-introgressed alleles in modern human populations. Using both ancient and present-day samples of modern humans, we integrate the known demographic history of populations, namely population divergence and migration, with tests for selection. We model how a sweep placed along different branches of an admixture graph acts to modify the variance and covariance in neutral allele frequencies among populations at linked loci. Using a method based on this model of allele frequencies, we study previously identified cases of Neanderthal adaptive introgression. From these, we identify cases in which Neanderthal introgressed alleles were quickly beneficial and other cases in which they persisted at low frequency for some time. For some of the alleles that persisted at low frequency, we show that selection likely independently favored them later on in geographically separated populations. Our work highlights how admixture with ancient hominins has contributed to modern human adaptation, contextualizes observed levels of Neanderthal ancestry in present-day and ancient samples, and identifies cases of temporally varying selection that are sometimes shared across large geographic distances.

scholarly journals Genetic structure of the grey side-gilled sea slug (Pleurobranchaea maculata) in coastal waters of New Zealand

2017 ◽  
Author(s):  
Yeşerin Yıldırım ◽  
Marti J. Anderson ◽  
Selina Patel ◽  
Craig D. Millar ◽  
Paul B. Rainey
Keyword(s):  
New Zealand ◽  
Genetic Structure ◽  
Sequence Data ◽  
Demographic History ◽  
Population Expansion ◽  
Haplotype Network ◽  
Founding Population ◽  
Mtdna Sequence ◽  
Expansion Time ◽  
History Of

AbstractPleurobranchaea maculatais a rarely studied species of the Heterobranchia found throughout the south and western Pacific – and recently recorded in Argentina – whose population genetic structure is unknown. Interest in the species was sparked in New Zealand following a series of dog deaths caused by ingestions of slugs containing high levels of the neurotoxin tetrodotoxin. Here we describe the genetic structure and demographic history ofP. maculatapopulations from five principle locations in New Zealand based on extensive analyses of 12 microsatellite loci and theCOIandCytBregions of mitochondrial DNA (mtDNA). Microsatellite data showed significant differentiation between northern and southern populations with population structure being associated with previously described regional variations in tetrodotoxin concentrations. However, mtDNA sequence data did not support such structure, revealing a star-shaped haplotype network with estimates of expansion time suggesting a population expansion in the Pleistocene era. Inclusion of publicly available mtDNA sequence from Argentinian sea slugs did not alter the star-shaped network. We interpret our data as indicative of a single founding population that fragmented following geographical changes that brought about the present day north-south divide in New Zealand waters. Lack of evidence of cryptic species supports data indicating that differences in toxicity of individuals among regions are a consequence of differences in diet.

scholarly journals Inferring the Joint Demographic History of Multiple Populations: Beyond the Diffusion Approximation

Genetics ◽  
2017 ◽  
Vol 206 (3) ◽  
pp. 1549-1567 ◽  
Author(s):  
Julien Jouganous ◽  
Will Long ◽  
Aaron P. Ragsdale ◽  
Simon Gravel
Keyword(s):  
Diffusion Approximation ◽  
Demographic History ◽  
Multiple Populations ◽  
History Of

scholarly journals Complex patterns of sex-biased demography in canines

2019 ◽  
Vol 286 (1903) ◽  
pp. 20181976 ◽  
Author(s):  
Tanya N. Phung ◽  
Robert K. Wayne ◽  
Melissa A. Wilson ◽  
Kirk E. Lohmueller
Keyword(s):  
Sequence Data ◽  
Demographic History ◽  
Multiple Paternity ◽  
Whole Genome Sequence ◽  
Evolutionary Time ◽  
Genetic Studies ◽  
History Of ◽  
Males And Females ◽  
Dog Domestication ◽  
Number Of Males

The demographic history of dogs is complex, involving multiple bottlenecks, admixture events and artificial selection. However, existing genetic studies have not explored variance in the number of reproducing males and females, and whether it has changed across evolutionary time. While male-biased mating practices, such as male-biased migration and multiple paternity, have been observed in wolves, recent breeding practices could have led to female-biased mating patterns in breed dogs. For example, breed dogs are thought to have experienced a popular sire effect, where a small number of males father many offspring with a large number of females. Here we use genetic variation data to test how widespread sex-biased mating practices in canines are during different evolutionary time points. Using whole-genome sequence data from 33 dogs and wolves, we show that patterns of diversity on the X chromosome and autosomes are consistent with a higher number of reproducing males than females over ancient evolutionary history in both dogs and wolves, suggesting that mating practices did not change during early dog domestication. By contrast, since breed formation, we found evidence for a larger number of reproducing females than males in breed dogs, consistent with the popular sire effect. Our results confirm that canine demography has been complex, with opposing sex-biased processes occurring throughout their history. The signatures observed in genetic data are consistent with documented sex-biased mating practices in both the wild and domesticated populations, suggesting that these mating practices are pervasive.

scholarly journals The timing of human adaptation from Neanderthal introgression

Genetics ◽  
2021 ◽  
Author(s):  
Sivan Yair ◽  
Kristin M Lee ◽  
Graham Coop
Keyword(s):  
Demographic History ◽  
Low Frequency ◽  
Modern Human ◽  
Allele Frequencies ◽  
Population Divergence ◽  
Human Populations ◽  
Human Adaptation ◽  
Adaptive Introgression ◽  
History Of ◽  
Spatio Temporal

Abstract Admixture has the potential to facilitate adaptation by providing alleles that are immediately adaptive in a new environment or by simply increasing the long term reservoir of genetic diversity for future adaptation. A growing number of cases of adaptive introgression are being identified in species across the tree of life, however the timing of selection, and therefore the importance of the different evolutionary roles of admixture, is typically unknown. Here, we investigate the spatio-temporal history of selection favoring Neanderthal-introgressed alleles in modern human populations. Using both ancient and present-day samples of modern humans, we integrate the known demographic history of populations, namely population divergence and migration, with tests for selection. We model how a sweep placed along different branches of an admixture graph acts to modify the variance and covariance in neutral allele frequencies among populations at linked loci. Using a method based on this model of allele frequencies, we study previously identified cases of Neanderthal adaptive introgression. From these, we identify cases in which Neanderthal introgressed alleles were quickly beneficial and other cases in which they persisted at low frequency for some time. For some of the alleles that persisted at low frequency, we show that selection likely independently favored them later on in geographically separated populations. Our work highlights how admixture with ancient hominins has contributed to modern human adaptation and contextualizes observed levels of Neanderthal ancestry in present-day and ancient samples.

Using Genomic Data to Infer Historic Population Dynamics of Nonmodel Organisms

2018 ◽  
Vol 49 (1) ◽  
pp. 433-456 ◽  
Author(s):  
Annabel C. Beichman ◽  
Emilia Huerta-Sanchez ◽  
Kirk E. Lohmueller
Keyword(s):  
Population Dynamics ◽  
Statistical Inference ◽  
Statistical Methods ◽  
Genome Sequence ◽  
Sequence Data ◽  
Demographic History ◽  
Genomic Data ◽  
Underlying Theory ◽  
History Of ◽  
Pros And Cons

Genome sequence data are now being routinely obtained from many nonmodel organisms. These data contain a wealth of information about the demographic history of the populations from which they originate. Many sophisticated statistical inference procedures have been developed to infer the demographic history of populations from this type of genomic data. In this review, we discuss the different statistical methods available for inference of demography, providing an overview of the underlying theory and logic behind each approach. We also discuss the types of data required and the pros and cons of each method. We then discuss how these methods have been applied to a variety of nonmodel organisms. We conclude by presenting some recommendations for researchers looking to use genomic data to infer demographic history.

scholarly journals Inferring the Demographic History of Inbred Species From Genome-Wide SNP Frequency Data

2019 ◽  
Author(s):  
Paul D. Blischak ◽  
Michael S. Barker ◽  
Ryan N. Gutenkunst
Keyword(s):  
Puma Concolor ◽  
Demographic History ◽  
Random Mating ◽  
Simulated Data ◽  
Conservation Agriculture ◽  
Model Fit ◽  
Parameter Estimates ◽  
History Of ◽  
Demographic Inference ◽  
Inbred Populations

AbstractDemographic inference using the site frequency spectrum (SFS) is a common way to understand historical events affecting genetic variation. However, most methods for estimating demography from the SFS assume random mating within populations, precluding these types of analyses in inbred populations. To address this issue, we developed a model for the expected SFS that includes inbreeding by parameterizing individual genotypes using beta-binomial distributions. We then take the convolution of these genotype probabilities to calculate the expected frequency of biallelic variants in the population. Using simulations, we evaluated the model’s ability to co-estimate demography and inbreeding using one- and two-population models across a range of inbreeding levels. We also applied our method to two empirical examples, American pumas (Puma concolor) and domesticated cabbage (Brassica oleracea var. capitata), inferring models both with and without inbreeding to compare parameter estimates and model fit. Our simulations showed that we are able to accurately co-estimate demographic parameters and inbreeding even for highly inbred populations (F = 0.9). In contrast, failing to include inbreeding generally resulted in inaccurate parameter estimates in simulated data and led to poor model fit in our empirical analyses. These results show that inbreeding can have a strong effect on demographic inference, a pattern that was especially noticeable for parameters involving changes in population size. Given the importance of these estimates for informing practices in conservation, agriculture, and elsewhere, our method provides an important advancement for accurately estimating the demographic histories of these species.

scholarly journals An ABC method for whole-genome sequence data: inferring paleolithic and neolithic human expansions

2018 ◽  
Author(s):  
Flora Jay ◽  
Simon Boitard ◽  
Frédéric Austerlitz
Keyword(s):  
Sequence Data ◽  
Demographic History ◽  
Relevant Information ◽  
Whole Genome Sequence ◽  
Sequencing Data ◽  
Human Sequence ◽  
Genome Wide ◽  
Classical Statistics ◽  
Very Large Datasets ◽  
Approximate Bayesian

AbstractSpecies generally undergo a complex demographic history, consisting, in particular, of multiple changes in population size. Genome-wide sequencing data are potentially highly informative for reconstructing this demographic history. A crucial point is to extract the relevant information from these very large datasets. Here we designed an approach for inferring past demographic events from a moderate number of fully sequenced genomes. Our new approach uses Approximate Bayesian Computation (ABC), a simulation-based statistical framework that allows (i) identifying the best demographic scenario among several competing scenarios, and (ii) estimating the best-fitting parameters under the chosen scenario. ABC relies on the computation of summary statistics. Using a cross-validation approach, we showed that statistics such as the lengths of haplotypes shared between individuals, or the decay of linkage disequilibrium with distance, can be combined with classical statistics (eg heterozygosity, Tajima’s D) to accurately infer complex demographic scenarios including bottlenecks and expansion periods. We also demonstrated the importance of simultaneously estimating the genotyping error rate. Applying our method on genome-wide human-sequence databases, we finally showed that a model consisting in a bottleneck followed by a Paleolithic and a Neolithic expansion was the most relevant for Eurasian populations.

Sign in / Sign up

Export Citation Format

Share Document