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Heredity (Edinb). 2018 Dec;121(6):548-556. doi: 10.1038/s41437-018-0122-x. Epub 2018 Jul 18.

Consequences of diverse evolutionary processes on american genetic gradients of modern humans.

Branco C1,2,3,4, Velasco M5, Benguigui M5, Currat M6,7, Ray N8,9, Arenas M10,11,12,13.

Author information

1
Department of Biochemistry, Genetics and Immunology, University of Vigo, Vigo, Spain.
2
Institute of Molecular Pathology and Immunology of the University of Porto (IPATIMUP), Porto, Portugal.
3
Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Porto, Portugal.
4
Department of Genetics and Biotechnology, University of Trás-os-Montes and Alto Douro (UTAD), Vila Real, Portugal.
5
Centre for Molecular Biology "Severo Ochoa", Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain.
6
Anthropology, Genetics and Peopling History Lab, Department of Genetics & Evolution -Anthropology Unit, University of Geneva, Geneva, Switzerland.
7
Institute of Genetics and Genomics in Geneva (IGE3), University of Geneva, Geneva, Switzerland.
8
EnviroSPACE Lab, Institute for Environmental Sciences, University of Geneva, Geneva, Switzerland.
9
Institute of Global Health, University of Geneva, Geneva, Switzerland.
10
Department of Biochemistry, Genetics and Immunology, University of Vigo, Vigo, Spain. marenas@uvigo.es.
11
Institute of Molecular Pathology and Immunology of the University of Porto (IPATIMUP), Porto, Portugal. marenas@uvigo.es.
12
Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Porto, Portugal. marenas@uvigo.es.
13
Centre for Molecular Biology "Severo Ochoa", Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain. marenas@uvigo.es.

Abstract

European genetic gradients of modern humans were initially interpreted as a consequence of the demic diffusion of expanding Neolithic farmers. However, recent studies showed that these gradients may also be influenced by other evolutionary processes such as population admixture or range contractions. Genetic gradients were observed in the Americas, although their specific evolutionary causes were not investigated. Here we extended the approach used to study genetic gradients in Europe to analyze the influence of diverse evolutionary scenarios on American genetic gradients. Using extensive computer simulations, we evaluated the impact of (i) admixture between expansion waves of modern humans, (ii) the presence of ice-sheets during the last glacial maximum (LGM) and (iii) long-distance dispersal (LDD) events, on the genetic gradients (detected by principal component analysis) of the entire continent, North America and South America. The specific simulation of North and South America showed that genetic gradients are usually orthogonal to the direction of range expansions-either expansions from Bering or posterior re-expansions to recolonize northern regions after ice sheets melting-and we suggest that they result from allele surfing processes. Conversely, our results on the entire continent show a northwest-southeast gradient obtained with any scenario, which we interpreted as a consequence of isolation by distance along the long length of the continent. These findings suggest that distinct genetic gradients can be detected at different regions of the Americas and that subcontinent regions present gradients more sensible to evolutionary and environmental factors (such as LDD and the LGM) than the whole continent.

PMID:
30022169
PMCID:
PMC6221893
[Available on 2019-12-01]
DOI:
10.1038/s41437-018-0122-x

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