Gene Flow in Natural Populations

Chromosomal forms of Anopheles gambiae, given the informal designations Bamako, Mopti, and Savannah, have been recognized by the presence or absence of four paracentric inversions on chromosome 2. Studies of karyotype frequencies at sites where the forms occur in sympatry have led to the suggestion that these forms represent species. We conducted a study of the genetic structure of populations of An. gambiae from two villages in Mali, west Africa. Populations at each site were composed of the Bamako and Mopti forms and the sibling species, Anopheles arabiensis. Karyotypes were determined for each individual mosquito and genotypes at 21 microsatellite loci determined. A number of the microsatellites have been physically mapped to polytene chromosomes, making it possible to select loci based on their position relative to the inversions used to define forms. We found that the chromosomal forms differ at all loci on chromosome 2, but there were few differences for loci on other chromosomes. Geographic variation was small. Gene f low appears to vary among different regions within the genome, being lowest on chromosome 2, probably due to hitchhiking with the inversions. We conclude that the majority of observed genetic divergence between chromosomal forms can be explained by forces that need not involve reproductive isolation, although reproductive isolation is not ruled out. We found low levels of gene f low between the sibling species Anopheles gambiae and Anopheles arabiensis, similar to estimates based on observed frequencies of hybrid karyotypes in natural populations.

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“…Both studies gave an estimate of N e to be 2,000-6,000, approximately. (31,32). The estimates of N e m between An.…”

Section: Resultsmentioning

confidence: 99%

Complexities in the genetic structure of Anopheles gambiae populations in west Africa as revealed by microsatellite DNA analysis

Lanzaro

Touré

Carnahan

et al. 1998

Proc. Natl. Acad. Sci. U.S.A.

147

149

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“…Gene :flow has the effect of homogenizing the genetic composition of a population and thus can be seen as a constraining evolutionary force (Slarkin, 1985), with an opposite effect to that of diversifying natural selection. Additionally, migration has two main effects: it reduces the between-group differences, and increases variances within demes (Konigsberg, 2000;Hamilton, 2009).…”

Section: Discussionmentioning

confidence: 99%

Facial asymmetry and genetic ancestry inLatinAmerican admixed populations

Quinto‐Sanchez

Adhikari

Acuña-Alonzo

et al. 2015

American J Phys Anthropol

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Fluctuating and directional asymmetry are aspects of morphological variation widely used to infer environmental and genetic factors affecting facial phenotypes. However, the genetic basis and environmental determinants of both asymmetry types is far from being completely known. The analysis of facial asymmetries in admixed individuais can be of help to characterize the impact of a genome's heterozygosity on the deveiopmental basis of both fl.uctuating and directional asymmetries. Here we characterize the association between genetic ancestry and individual asymmetry on a sample of Latin-American admixed populations. To do so, three-dimensional (3D) facial shape attributes were explored on a sample of 4,104 volunteers aged between 18 and 85 years. Individual ancestry and heterozygosity was estimated using more than 730,000 genome-wide markers. Multivariate techniques applied to geometric morphometric data were used to evaluate the magnitude and significance of directional and ftuctuating asymmetry (FA), as well as correiations and multipie regressions aimed to estimate the relationship between facial FA scores and heterozygosity and a set of covariates. Resuits indicate that directional and FA are both signi:ficant, the former being the strongest expression of asymmetry in this sample. In addition, our analyses suggest that there are some specific patterns of facial asymmetries characterizing the different ancestry groups. Finally, we find that more heterozygous individuais exhibit lower leveis of asymmetry. Our results highlight the importance of including ancestry-admixture estimators, especially when the analyses are aimed to compare leveis of asymmetries on groups differing on socioeconomic leveis, as a proxy to estimate developmental noise. Am J Phys Anthropol 000:000--000, 2015.

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“…As previously shown (15,16), it depends on just three parameters: the local deme size N, the age of the expansion T, and the migration rate m between adjacent demes (see below). Note that the current methodology is drastically different from previous approaches, which attempted to estimate migration between sampled populations (22,23), because, instead, we estimate the average number of immigrants in sampled demes (15,16) without needing to sample the population of origin of these migrants.…”

Section: Methodsmentioning

confidence: 99%

Molecular analysis reveals tighter social regulation of immigration in patrilocal populations than in matrilocal populations

Hamilton

Stoneking

Excoffier³

2005

Proc. Natl. Acad. Sci. U.S.A.

103

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Human social organization can deeply affect levels of genetic diversity. This fact implies that genetic information can be used to study social structures, which is the basis of ethnogenetics. Recently, methods have been developed to extract this information from genetic data gathered from subdivided populations that have gone through recent spatial expansions, which is typical of most human populations. Here, we perform a Bayesian analysis of mitochondrial and Y chromosome diversity in three matrilocal and three patrilocal groups from northern Thailand to infer the number of males and females arriving in these populations each generation and to estimate the age of their range expansion. We find that the number of male immigrants is 8 times smaller in patrilocal populations than in matrilocal populations, whereas women move 2.5 times more in patrilocal populations than in matrilocal populations. In addition to providing genetic quantification of sex-specific dispersal rates in human populations, we show that although men and women are exchanged at a similar rate between matrilocal populations, there are far fewer men than women moving into patrilocal populations. This finding is compatible with the hypothesis that men are strictly controlling male immigration and promoting female immigration in patrilocal populations and that immigration is much less regulated in matrilocal populations.ethnogenetics ͉ human evolution ͉ sex-bias dispersal G enetic analyses have supported the existence of sex-biased gene flow in various human populations (1-4). Several studies have shown that women could move among populations at higher rates than men (5-8), potentially explaining lower levels of local differentiation for mtDNA than Y chromosome markers (e.g., 9, 10), even though a recent analysis revealed similar levels of genetic structure at a broader scale (11). Different forms of social organization can impact patterns and levels of genetic diversity (12, 13), and sex differences in postmarital residence choice have been proposed to greatly affect isolation by distance patterns in humans (6). The patterns of gender-specific genetic markers, such as mitochondrial and Y chromosome diversity, were recently found to be deeply affected by postmarital residence choice in six populations of northern Thailand (14). Patrilocal populations, where men remain in their natal village and women move to their husband's village, showed lower levels of Y chromosome diversity than matrilocal populations; the reverse situation was observed for mtDNA diversity. Moreover, genetic distances were found to be lower for mtDNA between patrilocal populations than between matrilocal populations, a situation that was reversed for Y chromosome markers (14). Although these results strongly supported the view that sex-biased dispersal shaped patterns of diversity within and between populations, no attempt was made to quantify and compare the movement of males and females in the two types of societies. Such quantitation may yield additional insights into cult...

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Gene Flow in Natural Populations

Cited by 1,614 publications

References 60 publications

Complexities in the genetic structure of Anopheles gambiae populations in west Africa as revealed by microsatellite DNA analysis

Complexities in the genetic structure of Anopheles gambiae populations in west Africa as revealed by microsatellite DNA analysis

Facial asymmetry and genetic ancestry inLatinAmerican admixed populations

Molecular analysis reveals tighter social regulation of immigration in patrilocal populations than in matrilocal populations

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