scholarly journals Population history and the differential consequences of inbreeding and outcrossing in a plant metapoplation

2020 ◽  
Author(s):  
Peter D. Fields ◽  
Gretchen Arnold ◽  
Joel M. Kniskern ◽  
Douglas R. Taylor
Keyword(s):  
Gene Flow ◽  
Population Size ◽  
Empirical Studies ◽  
Genetic Load ◽  
Population History ◽  
Silene Latifolia ◽  
Population Genetic Analysis ◽  
Crossing Experiment ◽  
Estimate Gene Flow ◽  
Historical Variation

ABSTRACTThe phenotypic consequences of inbreeding typically result in a fitness decline proportional to the increase in the inbreeding coefficient, F. This basic assumption of a predictable, inverse relationship between fitness and F has been questioned by a number of empirical studies. We explored the relationship between population history and inbreeding in a metapopulation of the plant Silene latifolia, for which long-term data are available for the historical size and spatial distribution of hundreds of local demes. We used a population genetic analysis to estimate gene flow and bi-parental inbreeding (FIS) in demes with different histories of spatial isolation. A controlled crossing experiment examined whether the effect of inbreeding and outcrossing on fitness-related traits varied with different histories of population size and isolation. Historically isolated demes experienced less gene flow and an increase in FIS, as well as significant inbreeding advantage and outbreeding depression for traits expressed early in life. The causes of variation in the F-fitness relationship among populations will include variance in the distribution of deleterious recessive alleles driven by aspects of population history, including population size, founder effects, gene flow, bi-parental inbreeding, and opportunities for the purging of genetic load. Our findings show that isolation and historical variation in population size likely contribute substantial variation in past inbreeding and the consequences of future inbreeding across the metapopulation.

scholarly journals Introgression makes waves in inferred histories of effective population size

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.

scholarly journals Genomic signatures of inbreeding and genetic load in a threatened rattlesnake

2021 ◽  
Author(s):  
Alexander Ochoa ◽  
H. Lisle Gibbs
Keyword(s):  
Threatened Species ◽  
Empirical Studies ◽  
Genetic Load ◽  
Population History ◽  
Deleterious Mutations ◽  
Genetic Rescue ◽  
Isolated Populations ◽  
Genome Wide ◽  
The Impact

Theory predicts that threatened species living in small populations will experience high levels of inbreeding that will increase their negative genetic load but recent work suggests that the impact of load may be minimized by purging resulting from long term population bottlenecks. Empirical studies that examine this idea using genome-wide estimates of inbreeding and genetic load in threatened species are limited. Here we use genome resequencing data to compare levels of inbreeding, levels of genetic load and population history in threatened Eastern massasauga rattlesnakes (Sistrurus catenatus) which exist in small isolated populations and closely-related yet outbred Western massasauga rattlesnakes (S. tergeminus). In terms of inbreeding, S. catenatus genomes had a greater number of ROHs of varying sizes indicating sustained inbreeding through repeated bottlenecks when compared to S. tergeminus. At the species level, outbred S. tergeminus had higher genome-wide levels of genetic load in the form of greater numbers of derived deleterious mutations compared to S. catenatus presumably due to long-term purging of deleterious mutations in S. catenatus. In contrast, mutations that escaped the “drift sieve” and were polymorphic within S. catenatus populations were more abundant and more often found in homozygote genotypes than in S. tergeminus suggesting a reduced efficiency of purifying selection in smaller S. catenatus populations. Our results support an emerging idea that the historical demography of a threatened species has a significant impact on the type of genetic load present which impacts implementation of conservation actions such as genetic rescue.

scholarly journals POPULATION SIZE AND THE NATURE OF GENETIC LOAD IN GENTIANELLA GERMANICA

Evolution ◽  
2003 ◽  
Vol 57 (10) ◽  
pp. 2242-2251 ◽  
Author(s):  
Susanne Paland ◽  
Bernhard Schmid
Keyword(s):  
Population Size ◽  
Genetic Load ◽  
Gentianella Germanica

scholarly journals Linked vs. unlinked markers: multilocus microsatellite haplotype-sharing as a tool to estimate gene flow and introgression

2006 ◽  
Vol 16 (2) ◽  
pp. 243-256 ◽  
Author(s):  
WIM J. M. KOOPMAN ◽  
YINGHUI LI ◽  
ELS COART ◽  
W. ERIC VAN DE WEG ◽  
BEN VOSMAN ◽  
...  
Keyword(s):  
Gene Flow ◽  
Haplotype Sharing ◽  
Microsatellite Haplotype ◽  
Estimate Gene Flow

Positive Check or Chinese Checks?

2002 ◽  
Vol 61 (2) ◽  
pp. 591-607 ◽  
Author(s):  
James Lee ◽  
Cameron Campbell ◽  
Wang Feng
Keyword(s):  
Population Size ◽  
Chinese Population ◽  
European Population ◽  
Population History ◽  
Late Imperial China ◽  
Late Imperial ◽  
Lack Of Information ◽  
Preventive Check ◽  
Demographic Behavior ◽  
English Population

As recently as twenty-five years ago, there were virtually no demographers of China and there was little available data on Chinese demographic behavior. Thus in spite of intense interest in China's population dating back at least to Malthus (1766–1834), his initial understanding, or rather misunderstanding, of Chinese population dynamics remains dominant. While recent research on European population history has confirmed Malthus's observations that European, or at least English, population size was controlled largely by the preventive check, nuptiality, the absence of similar studies of Chinese population history ironically facilitated the persistence of a Malthusian hypothesis that Chinese population size was controlled largely by the positive check, mortality. It is a tribute to the elegance and power of the Malthusian orthodoxy that in spite of the lack of information on Chinese historic demographic behavior and economic performance, many of the most distinguished Western scholars of late imperial China continue to interpret social and economic processes in China during the last three hundred years in Malthusian or neo-Malthusian terms (Elvin 1973; Chao 1986; Huang 1990).

scholarly journals Population structure and demographic history of the chukar partridge Alectoris chukar in China

2013 ◽  
Vol 59 (4) ◽  
pp. 458-474 ◽  
Author(s):  
Sen Song ◽  
Shijie Bao ◽  
Ying Wang ◽  
Xinkang Bao ◽  
Bei An ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Gene Flow ◽  
North America ◽  
Demographic History ◽  
Population Expansion ◽  
Northwest China ◽  
Population History ◽  
Extant Species ◽  
History Of ◽  
Chukar Partridge

Abstract Pleistocene climate fluctuations have shaped the patterns of genetic diversity observed in extant species. Although the effects of recent glacial cycles on genetic diversity have been well studied on species in Europe and North America, genetic legacy of species in the Pleistocene in north and northwest of China where glaciations was not synchronous with the ice sheet development in the Northern Hemisphere or or had little or no ice cover during the glaciations’ period, remains poorly understood. Here we used phylogeographic methods to investigate the genetic structure and population history of the chukar partridge Alec-toris chukar in north and northwest China. A 1,152 – 1,154 bp portion of the mtDNA CR were sequenced for all 279 specimens and a total number of 91 haplotypes were defined by 113 variable sites. High levels of gene flow were found and gene flow estimates were greater than 1 for most population pairs in our study. The AMOVA analysis showed that 81% and 16% of the total genetic variability was found within populations and among populations within groups, respectively. The demographic history of chukar was examined using neutrality tests and mismatch distribution analyses and results indicated Late Pleistocene population expansion. Results revealed that most populations of chukar experienced population expansion during 0.027 ? 0.06 Ma. These results are at odds with the results found in Europe and North America, where population expansions occurred after Last Glacial Maximum (LGM, 0.023 to 0.018 Ma). Our results are not consistent with the results from avian species of Tibetan Plateau, either, where species experienced population expansion following the retreat of the extensive glaciation period (0.5 to 0.175 Ma).

scholarly journals Contrasting Patterns of Population History and Seed-mediated Gene Flow in Two Endemic Costa Rican Oak Species

2018 ◽  
Vol 109 (5) ◽  
pp. 530-542 ◽  
Author(s):  
Hernando Rodríguez-Correa ◽  
Ken Oyama ◽  
Mauricio Quesada ◽  
Eric J Fuchs ◽  
Antonio González-Rodríguez
Keyword(s):  
Gene Flow ◽  
Costa Rican ◽  
Population History ◽  
Seed Mediated

scholarly journals Denisovan ancestry and population history of early East Asians

2020 ◽  
Author(s):  
Diyendo Massilani ◽  
Laurits Skov ◽  
Mateja Hajdinjak ◽  
Byambaa Gunchinsuren ◽  
Damdinsuren Tseveendorj ◽  
...  
Keyword(s):  
Gene Flow ◽  
Human Population ◽  
Modern Human ◽  
Population History ◽  
East Asians ◽  
Aboriginal Australians ◽  
North East ◽  
History Of ◽  
Female Member ◽  
Admixture Event

AbstractWe present analyses of the genome of a ~34,000-year-old hominin skull cap discovered in the Salkhit Valley in North East Mongolia. We show that this individual was a female member of a modern human population that, following the split between East and West Eurasians, experienced substantial gene flow from West Eurasians. Both she and a 40,000-year-old individual from Tianyuan outside Beijing carried genomic segments of Denisovan ancestry. These segments derive from the same Denisovan admixture event(s) that contributed to present-day mainland Asians but are distinct from the Denisovan DNA segments in present-day Papuans and Aboriginal Australians.

scholarly journals Inbreeding depression due to mildly deleterious mutations in finite populations: size does matter

2000 ◽  
Vol 75 (1) ◽  
pp. 75-81 ◽  
Author(s):  
THOMAS BATAILLON ◽  
MARK KIRKPATRICK
Keyword(s):  
Population Size ◽  
Inbreeding Depression ◽  
Deleterious Mutation ◽  
Large Population ◽  
Genetic Load ◽  
Breeding Systems ◽  
Deleterious Mutations ◽  
Single Locus Analysis ◽  
Population Sizes ◽  
Inbreeding Rate

We studied the effects of population size on the inbreeding depression and genetic load caused by deleterious mutations at a single locus. Analysis shows how the inbreeding depression decreases as population size becomes smaller and/or the rate of inbreeding increases. This pattern contrasts with that for the load, which increases as population size becomes smaller but decreases as inbreeding rate goes up. The depression and load both approach asymptotic limits when the population size becomes very large or very small. Numerical results show that the transition between the small and the large population regimes is quite rapid, and occurs largely over a range of population sizes that vary by a factor of 10. The effects of drift on inbreeding depression may bias some estimates of the genomic rate of deleterious mutation. These effects could also be important in the evolution of breeding systems in hermaphroditic organisms and in the conservation of endangered populations.

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