Inference of Historical Population-Size Changes with Allele-Frequency Data

With up to millions of nearly neutral polymorphisms now being routinely sampled in population-genomic surveys, it is possible to estimate the site-frequency spectrum of such sites with high precision. Each frequency class reflects a mixture of potentially unique demographic histories, which can be revealed using theory for the probability distributions of the starting and ending points of branch segments over all possible coalescence trees. Such distributions are completely independent of past population history, which only influences the segment lengths, providing the basis for estimating average population sizes separating tree-wide coalescence events. The history of population-size change experienced by a sample of polymorphisms can then be dissected in a model-flexible fashion, and extension of this theory allows estimation of the mean and full distribution of long-term effective population sizes and ages of alleles of specific frequencies. Here, we outline the basic theory underlying the conceptual approach, develop and test an efficient statistical procedure for parameter estimation, and apply this to multiple population-genomic datasets for the microcrustacean Daphnia pulex.

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Diversity and Paleodemography of the Addax (Addax nasomaculatus), a Saharan Antelope on the Verge of Extinction

Genes ◽

10.3390/genes12081236 ◽

2021 ◽

Vol 12 (8) ◽

pp. 1236

Author(s):

Elisabeth Hempel ◽

Michael V. Westbury ◽

José H. Grau ◽

Alexandra Trinks ◽

Johanna L. A. Paijmans ◽

...

Keyword(s):

Population Size ◽

Population History ◽

Phylogeographic Structure ◽

Recent Common Ancestor ◽

Mitochondrial Genomes ◽

Effective Population ◽

Mammal Species ◽

Human Disturbances ◽

Most Recent Common Ancestor ◽

History Of

Since the 19th century, the addax (Addax nasomaculatus) has lost approximately 99% of its former range. Along with its close relatives, the blue antelope (Hippotragus leucophaeus) and the scimitar-horned oryx (Oryx dammah), the addax may be the third large African mammal species to go extinct in the wild in recent times. Despite this, the evolutionary history of this critically endangered species remains virtually unknown. To gain insight into the population history of the addax, we used hybridization capture to generate ten complete mitochondrial genomes from historical samples and assembled a nuclear genome. We found that both mitochondrial and nuclear diversity are low compared to other African bovids. Analysis of mitochondrial genomes revealed a most recent common ancestor ~32 kya (95% CI 11–58 kya) and weak phylogeographic structure, indicating that the addax likely existed as a highly mobile, panmictic population across its Sahelo–Saharan range in the past. PSMC analysis revealed a continuous decline in effective population size since ~2 Ma, with short intermediate increases at ~500 and ~44 kya. Our results suggest that the addax went through a major bottleneck in the Late Pleistocene, remaining at low population size prior to the human disturbances of the last few centuries.

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Introgression makes waves in inferred histories of effective population size

10.1101/121483 ◽

2017 ◽

Author(s):

John Hawks

Keyword(s):

Gene Flow ◽

Population Size ◽

Effective Population Size ◽

Population History ◽

Human Populations ◽

Effective Population ◽

History Of ◽

Or Gene ◽

Time Of Origin ◽

Past Population

AbstractHuman populations have a complex history of introgression and of changing population size. Human genetic variation has been affected by both these processes, so that inference of past population size depends upon the pattern of gene flow and introgression among past populations. One remarkable aspect of human population history as inferred from genetics is a consistent “wave” of larger effective population size, prior to the bottlenecks and expansions of the last 100,000 years. Here I carry out a series of simulations to investigate how introgression and gene flow from genetically divergent ancestral populations affect the inference of ancestral effective population size. Both introgression and gene flow from an extinct, genetically divergent population consistently produce a wave in the history of inferred effective population size. The time and amplitude of the wave reflect the time of origin of the genetically divergent ancestral populations and the strength of introgression or gene flow. These results demonstrate that even small fractions of introgression or gene flow from ancient populations may have large effects on the inference of effective population size.

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Recent effective population size in Eastern European plain Russians correlates with the key historical events

Scientific Reports ◽

10.1038/s41598-020-66734-y ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Ural Yunusbaev ◽

Arslan Ionusbaev ◽

Giyoun Han ◽

Hyung Wook Kwon

Keyword(s):

Population Size ◽

Ethnic Group ◽

Effective Population Size ◽

Ural Region ◽

Population History ◽

Eastern European ◽

Effective Population ◽

History Of ◽

Key Events ◽

Volga Ural Region

Abstract Effective population size reflects the history of population growth, contraction, and structuring. When the effect of structuring is negligible, the inferred trajectory of the effective population size can be informative about the key events in the history of a population. We used the IBDNe and DoRIS approaches, which exploit the data on IBD sharing between genomes, to reconstruct the recent effective population size in two population datasets of Russians from Eastern European plain: (1) ethnic Russians sampled from the westernmost part of Russia; (2) ethnic Russians, Bashkirs, and Tatars sampled from the Volga-Ural region. In this way, we examined changes in effective population size among ethnic Russians that reside in their historical area at the West of the plain, and that expanded eastward to come into contact with the indigenous peoples at the East of the plain. We compared the inferred demographic trajectories of each ethnic group to written historical data related to demographic events such as migration, war, colonization, famine, establishment, and collapse of empires. According to IBDNe estimations, 200 generations (~6000 years) ago, the effective size of the ancestral populations of Russians, Bashkirs, and Tatars hovered around 3,000, 30,000, and 8,000 respectively. Then, the ethnic Russians exponentially grew with increasing rates for the last 115 generations and become the largest ethnic group of the plain. Russians do not show any drop in effective population size after the key historical conflicts, including the Mongol invasion. The only exception is a moderate drop in the 17th century, which is well known in Russian history as The Smuta. Our analyses suggest a more eventful recent population history for the two small ethnic groups that came into contact with ethnic Russians in the Volga-Ural region. We found that the effective population size of Bashkirs and Tatars started to decrease during the time of the Mongol invasion. Interestingly, there is an even stronger drop in the effective population size that coincides with the expansion of Russians to the East. Thus, 15–20 generations ago, i.e. in the 16–18th centuries in the trajectories of Bashkirs and Tatars, we observe the bottlenecks of four and twenty thousand, respectively. Our results on the recent effective population size correlate with the key events in the history of populations of the Eastern European plain and have importance for designing biomedical studies in the region.

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Human paternal and maternal demographic histories: insights from high-resolution Y chromosome and mtDNA sequences

10.1101/001792 ◽

2014 ◽

Cited By ~ 1

Author(s):

Sebastian Lippold ◽

Hongyang Xu ◽

Albert Ko ◽

Mingkun Li ◽

Gabriel Renaud ◽

...

Keyword(s):

Population Size ◽

Effective Population Size ◽

Y Chromosome ◽

Global Scale ◽

Human Populations ◽

Effective Population ◽

Population Sizes ◽

History Of ◽

Out Of Africa ◽

Complete Mtdna

To investigate in detail the paternal and maternal demographic histories of humans, we obtained ~500 kb of non-recombining Y chromosome (NRY) sequences and complete mtDNA genome sequences from 623 males from 51 populations in the CEPH Human Genome Diversity Panel (HGDP). Our results: confirm the controversial assertion that genetic differences between human populations on a global scale are bigger for the NRY than for mtDNA; suggest very small ancestral effective population sizes (<100) for the out-of-Africa migration as well as for many human populations; and indicate that the ratio of female effective population size to male effective population size (Nf/Nm) has been greater than one throughout the history of modern humans, and has recently increased due to faster growth in Nf. However, we also find substantial differences in patterns of mtDNA vs. NRY variation in different regional groups; thus, global patterns of variation are not necessarily representative of specific geographic regions.

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EFFECTS OF POPULATION SIZE AND SELECTION INTENSITY ON SHORT-TERM RESPONSE TO SELECTION FOR POSTWEANING GAIN IN MICE

Genetics ◽

10.1093/genetics/73.3.513 ◽

1973 ◽

Vol 73 (3) ◽

pp. 513-530

Author(s):

J P Hanrahan ◽

E J Eisen ◽

J E Legates

Keyword(s):

Population Size ◽

Selection Response ◽

Selection Intensity ◽

Realized Heritability ◽

Family Selection ◽

Effective Population ◽

Population Sizes ◽

Selection For ◽

Selection Intensities ◽

Term Response

ABSTRACT The effects of population size and selection intensity on the mean response was examined after 14 generations of within full-sib family selection for postweaning gain in mice. Population sizes of 1, 2, 4, 8 and 16 pair matings were each evaluated at selection intensities of 100% (control), 50% and 25% in a replicated experiment. Selection response per generation increased as selection intensity increased. Selection response and realized heritability tended to increase with increasing population size. Replicate variability in realized heritability was large at population sizes of 1, 2 and 4 pairs. Genetic drift was implicated as the primary factor causing the reduced response and lowered repeatability at the smaller population sizes. Lines with intended effective population sizes of 62 yielded larger selection responses per unit selection differential than lines with effective population sizes of 30 or less.

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The history of genetic diversity and effective population size of an isolated Microtus oeconomus population on Kis Balaton

Mammalian Biology ◽

10.1007/s42991-021-00199-y ◽

2021 ◽

Author(s):

Veronika Sládkovičová ◽

Dávid Žiak ◽

Peter Miklós ◽

András Gubányi ◽

Győző Horváth

Keyword(s):

Genetic Diversity ◽

Population Size ◽

Effective Population Size ◽

Effective Population ◽

Microtus Oeconomus ◽

History Of

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The Genetic History of France

10.1101/712497 ◽

2019 ◽

Author(s):

Aude Saint Pierre ◽

Joanna Giemza ◽

Matilde Karakachoff ◽

Isabel Alves ◽

Philippe Amouyel ◽

...

Keyword(s):

Genetic Structure ◽

Demographic History ◽

Migration Routes ◽

Effective Population ◽

Genetic Studies ◽

Independent Population ◽

Genome Wide Data ◽

Population Sizes ◽

History Of ◽

Exhaustive Study

ABSTRACTThe study of the genetic structure of different countries within Europe has provided significant insights into their demographic history and their actual stratification. Although France occupies a particular location at the end of the European peninsula and at the crossroads of migration routes, few population genetic studies have been conducted so far with genome-wide data. In this study, we analyzed SNP-chip genetic data from 2 184 individuals born in France who were enrolled in two independent population cohorts. Using FineStructure, six different genetic clusters of individuals were found that were very consistent between the two cohorts. These clusters match extremely well the geography and overlap with historical and linguistic divisions of France. By modeling the relationship between genetics and geography using EEMS software, we were able to detect gene flow barriers that are similar in the two cohorts and corresponds to major French rivers or mountains. Estimations of effective population sizes using IBDNe program also revealed very similar patterns in both cohorts with a rapid increase of effective population sizes over the last 150 generations similar to what was observed in other European countries. A marked bottleneck is also consistently seen in the two datasets starting in the fourteenth century when the Black Death raged in Europe. In conclusion, by performing the first exhaustive study of the genetic structure of France, we fill a gap in the genetic studies in Europe that would be useful to medical geneticists but also historians and archeologists.

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The role of matrilineality in shaping patterns of Y chromosome and mtDNA sequence variation in southwestern Angola

10.1101/349878 ◽

2018 ◽

Author(s):

Sandra Oliveira ◽

Alexander Hübner ◽

Anne-Maria Fehn ◽

Teresa Aço ◽

Fernanda Lages ◽

...

Keyword(s):

Y Chromosome ◽

Sequence Data ◽

Population History ◽

Female Population ◽

Bantu Languages ◽

Mtdna Sequence ◽

Population Sizes ◽

Group Variation ◽

History Of ◽

Previous Demonstration

AbstractSouthwestern Angola is a region characterized by contact between indigenous foragers and incoming food-producers, involving genetic and cultural exchanges between peoples speaking Kx’a, Khoe-Kwadi and Bantu languages. Although present-day Bantu-speakers share a patrilocal residence pattern and matrilineal principle of clan and group membership, a highly stratified social setting divides dominant pastoralists from marginalized groups that subsist on alternative strategies and have previously been though to have pre-Bantu origins. Here, we compare new high-resolution sequence data from 2.3 Mb of the non-recombining Y chromosome (NRY) from 170 individuals with previously reported mitochondrial genomes (mtDNA), to investigate the population history of seven representative southwestern Angolan groups (Himba, Kuvale, Kwisi, Kwepe, Twa, Tjimba, !Xun) and to study the causes and consequences of sex-biased processes in their genetic variation. We found no clear link between the formerly Kwadi-speaking Kwepe and pre-Bantu eastern African migrants, and no pre-Bantu NRY lineages among Bantu-speaking groups, except for small amounts of “Khoisan” introgression. We therefore propose that irrespective of their subsistence strategies, all Bantu-speaking groups of the area share a male Bantu origin. Additionally, we show that in Bantu-speaking groups, the levels of among-group and between-group variation are higher for mtDNA than for NRY. These results, together with our previous demonstration that the matriclanic systems of southwestern Angolan Bantu groups are genealogically consistent, suggest that matrilineality strongly enhances both female population sizes and interpopulation mtDNA variation.

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Genetic diversity, demographic history and neo-sex chromosomes in the Critically Endangered Raso lark

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2019.2613 ◽

2020 ◽

Vol 287 (1922) ◽

pp. 20192613 ◽

Cited By ~ 2

Author(s):

Elisa G. Dierickx ◽

Simon Yung Wa Sin ◽

H. Pieter J. van Veelen ◽

M. de L. Brooke ◽

Yang Liu ◽

...

Keyword(s):

Genetic Diversity ◽

Population Size ◽

Sex Chromosomes ◽

Demographic History ◽

Large Population ◽

Effective Population ◽

Island Species ◽

Population Sizes ◽

Approaches To Study ◽

Genetic Signatures

Small effective population sizes could expose island species to inbreeding and loss of genetic variation. Here, we investigate factors shaping genetic diversity in the Raso lark, which has been restricted to a single islet for approximately 500 years, with a population size of a few hundred. We assembled a reference genome for the related Eurasian skylark and then assessed diversity and demographic history using RAD-seq data (75 samples from Raso larks and two related mainland species). We first identify broad tracts of suppressed recombination in females, indicating enlarged neo-sex chromosomes. We then show that genetic diversity across autosomes in the Raso lark is lower than in its mainland relatives, but inconsistent with long-term persistence at its current population size. Finally, we find that genetic signatures of the recent population contraction are overshadowed by an ancient expansion and persistence of a very large population until the human settlement of Cape Verde. Our findings show how genome-wide approaches to study endangered species can help avoid confounding effects of genome architecture on diversity estimates, and how present-day diversity can be shaped by ancient demographic events.

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