Endogamy index and its changes with time in some populations of the Volga-Ural region

Data on several populations of Russia have been used to demonstrate that the change in the endogamy index detected in the second half of the 20th century is not global. Migration activity remains high in populations with relatively low endogamy indices, and their endogamy does not change with time. In regions with medium and high endogamy indices, these values also tend to remain stable. The endogamy indices of urban populations are increasing, and those of rural populations are decreasing.     

Inbreeding and endogamy in Tatarstan

The random inbreeding (F(ST)) and local inbreeding (a) values have been calculated for populations of the district and rural municipality ranks of 16 and 13 raions (administrative districts) of Tatarstan, Russia, respectively. The correlations between all inbreeding values are positive and vary from 0.38 to 0.80. The endogamy index has been calculated for populations of the district rank; it varies from 0.45 in Pestrechinskii raion to 0.74 in Aktanyshskii raion. Cartographic extrapolation of the endogamy indices has been performed.     

Inbreeding and endogamy in Tatarstan

The random inbreeding (F _st) and local inbreeding (a) values have been calculated for populations of the district and rural municipality ranks of 16 and 13 raions (administrative districts) of Tatarstan, Russia, respectively. The correlations between all inbreeding values are positive and vary from 0.38 to 0.80. The endogamy index has been calculated for populations of the district rank; it varies from 0.45 in Pestrechinskii raion to 0.74 in Aktanyshskii raion. Cartographic extrapolation of the endogamy indices has been performed.     

The gene pool of the Belgorod oblast population: changes in the endogamy indices of district populations with time

Changes in the endogamy indices of district populations of the Central Chernozem region of Russia during the past 100 years were studied. The size of an elementary population in this region increased from that of a rural municipality in the mid-20th century to that of an administrative district in the late 20th century.     

The gene pool of the belgorod oblast population: Changes in the endogamy indices of district populations with time

Changes in the endogamy indices of district populations of the Central Chernozem region of Russia during the past 100 years were studied. The size of an elementary population in this region increased from that of a rural municipality in the mid-20th century to that of an administrative district in the late 20th century.     

Ace Alu insertion polymorphism in Croatia and its isolates

Alu elements are a family of interspersed repeats in the genome propagating by retroposition into new chromosomal locations. Alu insertion in Ace gene is known to be polymorphic (presence/absence of Alu element) in worldwide populations and as such serves as marker for population structure analyses. In this study we examined the distribution of genotypes and allele frequencies of this polymorphism in general Croatian population and its two isolates (the island of Hvar and the coastal region of the Middle Dalmatia) and related them to the level of endogamy as an indicator of inbreeding in these populations. Results showed that these three population groups are different with respect to Ace Alu polymorphism. The endogamy was highest on the island of Hvar. With the increase of endogamy a decrease in heterozigosity was observed. The same trend was observed for the frequency of insertion allele. Its frequencies in the village subpopulations of two studied isolates are subject to genetic drift due to small population sizes and high levels of endogamy. This in turn causes genetic differentiation among villages that is observed to be higher on the island of Hvar than in the coastal region. In the worldwide perspective, the Ace Alu insertion allele frequency of 50.6% in the general Croatian population falls within the range of other European populations.     

Marriage-migration characteristics of the urban and rural populations of Udmurtia

Marriage records of six raions (districts) of Udmurtia and the city of Glazov (a total of 10,518 records) have been used to calculate marriage-migration parameters. The endogamy indices of the rural and urban Udmurt populations are 0.59 (from 0.48 to 0.76 in individual districts) and 0.29, respectively, and those of the rural and urban Russian populations are 0.33 and 0.47, respectively. The mean ethnic assortativeness values are 1.05 and 0.89 for the rural and urban Udmurt populations, respectively, and 2.13 and 1.44 for the rural and urban Russian populations, respectively. The parameters of isolation by distance for the rural Udmurt population are the following: sigma = 52.4, a = 0.00035, and b = 0.012; those for the urban Udmurt population are 54.1, 0.00020, and 0.010, respectively.     

Endogamy and variation in blood pressure levels in Croatian island isolates

Blood pressure variation was investigated among populations inhabiting islands and peninsula of Middle Dalmatia, Croatia. The number of previous anthropological studies pointed to isolation and different genetic population structure in this environmentally fairly homogeneous area. Variation in blood pressure (systolic and diastolic) among the populations of the islands of Brac, Hvar, Korcula, and the Peljesac peninsula was assessed at three levels involving village populations, regional (western and eastern) populations and the entire island populations. The blood pressure data were collected from 3834 adult individuals inhabiting 37 rural communities and were adjusted for age and body mass index. Variation in blood pressure levels existed among regions and villages. Due to the history of differential settlement, small village sizes and high levels of reproductive isolation, the observed blood pressure variation could be attributed to founder effect, genetic drift and inbreeding. The involvement of genetic factors was tested by relating blood pressure variation among villages to degree of isolation among them. Blood pressure means and proportions of hypertensives increased with endogamy levels in males. In females, this effect could not be observed. However, in both sexes the highest proportions of hypertensives (more than 40%) were found in villages that are most reproductively closed (endogamy greater than 80%). These populations are considered particularly promising for further genetic epidemiological research.     

Marriage-migration characteristics of the urban and rural populations of Udmurtia

Marriage records of six raions (districts) of Udmurtia and the city of Glazov (a total of 10518 records) have been used to calculate marriage-migration parameters. The endogamy indices of the rural and urban Udmurt populations are 0.59 (from 0.48 to 0.76 in individual districts) and 0.29, respectively, and those of the rural and urban Russian populations are 0.33 and 0.47, respectively. The mean ethnic assortativeness values are 1.05 and 0.89 for the rural and urban Udmurt populations, respectively, and 2.13 and 1.44 for the rural and urban Russian populations, respectively. The parameters of isolation by distance for the rural Udmurt population are the following: σ = 52.4, a = 0.00035, and b = 0.012; those for the urban Udmurt population are 54.1, 0.00020, and 0.010, respectively.     

Genetic differentiation processes among the populations in India

The genetic variability in Indian populations is examined on the basis of the study of Tf, Gc, Gm, and Km polymorphisms. This variability is not associated with fluctuations, but is related to population history (mainly to migrations, hybrydization and caste endogamy). When genetic distances are calculated, Northern, Southern and Western Indian poplations show closer resemblances to Western Asian populations, while Eastern Indian populations are more similar to Mongoloid peoples.     

Contrasting patterns of Y chromosome variation in Ashkenazi Jewish and host non-Jewish European populations

The molecular basis of more than 25 genetic diseases has been described in Ashkenazi Jewish populations. Most of these diseases are characterized by one or two major founder mutations that are present in the Ashkenazi population at elevated frequencies. One explanation for this preponderance of recessive diseases is accentuated genetic drift resulting from a series of dispersals to and within Europe, endogamy, and/or recent rapid population growth. However, a clear picture of the manner in which neutral genetic variation has been affected by such a demographic history has not yet emerged. We have examined a set of 32 binary markers (single nucleotide polymorphisms; SNPs) and 10 microsatellites on the non-recombining portion of the Y chromosome (NRY) to investigate the ways in which patterns of variation differ between Ashkenazi Jewish and their non-Jewish host populations in Europe. This set of SNPs defines a total of 20 NRY haplogroups in these populations, at least four of which are likely to have been part of the ancestral Ashkenazi gene pool in the Near East, and at least three of which may have introgressed to some degree into Ashkenazi populations after their dispersal to Europe. It is striking that whereas Ashkenazi populations are genetically more diverse at both the SNP and STR level compared with their European non-Jewish counterparts, they have greatly reduced within-haplogroup STR variability, especially in those founder haplogroups that migrated from the Near East. This contrasting pattern of diversity in Ashkenazi populations is evidence for a reduction in male effective population size, possibly resulting from a series of founder events and high rates of endogamy within Europe. This reduced effective population size may explain the high incidence of founder disease mutations despite overall high levels of NRY diversity.Electronic Supplementary Material Supplementary material is available in the online version of this article at D.M. Behar and D. Garrigan contributed equally to this workElectronic database information: URLs for the data in this article are as follows:ARLEQUIN,     

Isolation and marriage patterns in four South Tyrolean villages (Italy) during the nineteenth century

No information is currently available on the marriage patterns of German-speaking communities of the South Tyrol area. The aim of this study is to investigate the reproductive isolation of four South Tyrolean mountain villages during the 19th century. Data about 3953 marriages were drawn from existing pedigrees and completed with data from the parish registers of the studied villages to calculate the following indicators: age at marriage, endogamy, inbreeding from dispensations and from isonymy and repeated pairs of surnames among couples. The results show high levels of endogamy (78-87%) and an elevated age at marriage in all the studied villages. The percentages of consanguineous marriages (10-33%) vary considerably but result overall in relatively low inbreeding values (alpha 0.0015-0.0036; Ft 0.0098-0.0138). Levels of endogamy are consistent with the geographic characteristics of the area, while inbreeding values are lower than those observed in previous studies on Alpine communities. This is due to a low frequency of marriages between close relatives, probably related to the peculiar demographic and cultural characteristics of the studied populations that differentiate them from neighbouring Italian-speaking villages.     

Global patterns in human mitochondrial DNA and Y-chromosome variation caused by spatial instability of the local cultural processes

Because of the widespread phenomenon of patrilocality, it is hypothesized that Y-chromosome variants tend to be more localized geographically than those of mitochondrial DNA (mtDNA). Empirical evidence confirmatory to this hypothesis was subsequently provided among certain patrilocal and matrilocal groups of Thailand, which conforms to the isolation by distance mode of gene diffusion. However, we expect intuitively that the patterns of genetic variability may not be consistent with the above hypothesis among populations with different social norms governing the institution of marriage, particularly among those that adhere to strict endogamy rules. We test the universality of this hypothesis by analyzing Y-chromosome and mtDNA data in three different sets of Indian populations that follow endogamy rules to varying degrees. Our analysis of the Indian patrilocal and the matrilocal groups is not confirmatory to the sex-specific variation observed among the tribes of Thailand. Our results indicate spatial instability of the impact of different cultural processes on the genetic variability, resulting in the lack of universality of the hypothesized pattern of greater Y-chromosome variation when compared to that of mtDNA among the patrilocal populations.     

Genetic demographic characteristics of the rural population of the Tuva Republic: marriage structure and inbreeding]

Marriage structure was studied in three rural populations of the Tuva Republic: the Shinaan population and the populations of Todzhinskii and Bai-Taiginskii raions (districts). The Shinaan and Bai-Taiginskii populations had high levels of endogamy (0.6704 and 0.6050, respectively). In the Todzhinskii population, which was characterized by a mixed ethnic composition, endogamy was 0.3779 for the total population and 0.4626 for Tuvinians; interethnic marriages in this population were rare. The values of marriage assortativeness with respect to birthplace were 19.38, 40.75, 75.87, and 41.87% in the Shinaan, Bai-Taiginskii, all the Todzhinskii populations, and Tuvinian monoethnic marriages in the Todzhinskii raion, respectively. High marriage assortativeness with respect to ethnicity was found. Its values (A') were 91.85 and 93.49% in Tuvinians and Russians, respectively. Tuvinian populations were characterized by high inbreeding. The total (F(it)), random (Fst), and nonrandom inbreeding (Fis) estimated by isonymy were 0.004237, 0.002298, and 0.001944 in the Shinaan population, 0.007292, 0.009448, and -0.002177 in the Bai-Taiginskii population, and 0.003846, 0.004152, and -0.000307 in the Todzhinskii population, respectively (in the latter populations, the F(it), Fst, and Fis values for Tuvinian marriages alone were 0.005000, 0.007222, and -0.002238, respectively). The results obtained indicate that individual territorial groups of Tuvinians retain a high degree of genetic isolation from one another.     

Population structure of the Indian people: some microevolutionary aspects

Some aspects of population structure, namely village endogamy, marital distance and consanguinity in India are discussed. These parameters show social and geographic variation. The role of culture is of great importance in determining the mating pattern of a population. In the Indian situation, group endogamy in general does not cause inbreeding. Consanguinity is a cultural phenomenon of long-standing tradition, and so far there is no strong indication of a temporal change.     

Inbreeding as measured by isonymy in two Venezuelan populations and its relationship to other variables

Isonymy is a useful approach to the study of population structure and thus can be utilized to detect deviations from random mating. In this study we give the results of an analysis of inbreeding levels and relate such variables as mean marital distance, surnames repeated in isonymous couples, and percentage of people using only maternal surnames to inbreeding and endogamy in two Venezuelan populations of black ancestry, Birongo and La Sabana. These populations differ in their sociocultural development and degree of isolation. We estimated inbreeding through isonymy and directly from genealogy. The most important findings are that the Ft values are higher than the a's, that the Fn component of Ft is higher than the Fr component, and that there is higher endogamy, inbreeding, and isolation in Birongo than in La Sabana. These results are in agreement with the sociocultural and historical background and development of each population. Nevertheless, both populations show similar temporal trends in almost all the variables analyzed. The use of isonymy as a complementary tool to study population structure is proposed, especially for Ibero-American populations.     

Patterns of genetic variability in central and peripheral populations of <Emphasis Type="Italic">Dipteryx alata</Emphasis> (Fabaceae) in the Brazilian Cerrado

This study tested whether genetic parameters in Dipteryx alata populations, estimated from genomic and chloroplastidial microsatellite markers, were distributed according to a central-peripheral model, inferring which factors drive this spatial distribution of genetic variability within populations. For each of the 23 populations sampled throughout the species’ range, the mean number of alleles per locus, expected heterozygosity and intrapopulation fixation indices were calculated using a rarefaction approach based on 54 alleles from 8 nuclear microsatellites. Explanatory variables were grouped into three subsets: the ecological suitability estimated by combining different techniques of ecological niche modeling, variables expressing human occupation, and a historical variable represented by the first eigenvector from the pairwise F _ST matrix based on cpDNA microsatellites. Each response variable was modeled using first (linear) and second (quadratic) order trend surface analysis (TSA). Multiple regressions were then used to evaluate the relative effects of the explanatory variables, based on AIC multi-model selection. In general, the genetic parameters did not follow a classical central-periphery model. Ecological suitability had a significance influence in all genetic parameters, so more suitable regions have higher genetic diversity and low endogamy. There was also a relationship between fixation indices and human impacts. The high genetic diversity in the southwestern region of Cerrado suggested that recent range expansion (after the Last Glacial Maximum) may also influenced the observed intrapopulation genetic patterns. Thus, complex combinations of both historical and ecological drivers, as well as contemporary human occupation, seem to drive current genetic composition within D. alata populations throughout its geographic range.     

Marriage migration parameters in six rural districts of Bashkortostan Republic

The marriage migration structure of the populations of six districts of Bashkortostan Republic has been studied. The rates of assortative marriages in Bashkirs, Tatars, and Russians are 1.02–2.71, 1.30–5.99, and 2.14–7.50, respectively; the endogamy indices are 0.58–0.97, 0.90, and 0.68, respectively. Malecot’s isolation-by-distance parameters in Bashkirs, Tatars, and Russians, respectively, are the following: σ is 6.7–83.0, 40.3–106.1, and 69.9; a is 0.00012–0.00074, 0.00170–0.0029, and 0.00096; and b is 0.0087–0.0467, 0.0038–0.0208, and 0.0129. Changes in these parameters with time have been traced.     

Is the Central Valley of Costa Rica a genetic isolate?

In the last decade, the Costa Rican Central Valley population (CRCV), has received considerable scientific attention, attributed in part to a particularly interesting population structure. Two different and contradictory explanations have emerged: (1) An European-Amerindian-African admixed population, with some regional genetic heterocigosity and moderate degrees of consanguinity, similar to other Latin-American populations. (2) A genetic isolate, with a recent founder effect of European origin, genetically homogeneous, with a high intermarriage rate, and with a high degree of consanguinity. Extensive civil and religious documentation, since the settlement of the current population, allows wide genealogy and isonymy studies useful in the analysis of both hypotheses. This paper reviews temporal and spatial aspects of endogamy and consanguinity in the CRCV as a key to understand population history. The average inbreeding coefficients (a) between 1860 and 1969 show a general decrease within time. The consanguinity in the CRCV population is not homogeneous, and it is related to a variable geographic pattern. Results indicate that the endogamy frequencies are high but in general it was not correlated with a values. The general tendency shows a consanguinity decrease in time, and from rural to urban communities, repeating the tendencies observed in other countries with the same degree of development, and follows the general Western World tendency. Few human areas or communities in the world can be considered true genetic isolates. As shown, during last century, the CRCV population has had consanguinity values that definitively do not match those of true genetic isolates. A clear knowledge of the Costa Rican population genetic structure is needed to explain the origin of genetic diseases and its implications to the health system.     

Phenotypic plasticity closely linked to climate at origin and resulting in increased mortality under warming and frost stress in a common grass

Phenotypic plasticity is important for species responses to global change and species coexistence. Phenotypic plasticity differs among species and traits and changes across environments. Here, we investigated phenotypic plasticity of the widespread grass Arrhenatherum elatius in response to winter warming and frost stress by comparing phenotypic plasticity of 11 geographically and environmentally distinct populations of this species to phenotypic plasticity of populations of different species originating from a single environment. The variation in phenotypic plasticity was similar for populations of a single species from different locations compared to populations of functionally and taxonomically diverse species from one environment for the studied traits (leaf biomass production and root integrity after frost) across three indices of phenotypic plasticity (RDPI, PIN, slope of reaction norm). Phenotypic plasticity was not associated with neutral genetic diversity but closely linked to the climate of the populations’ origin. Populations originating from warmer and more variable climates showed higher phenotypic plasticity. This indicates that phenotypic plasticity can itself be considered as a trait subject to local adaptation to climate. Finally, our data emphasize that high phenotypic plasticity is not per se positive for adaptation to climate change, as differences in stress responses are resulting in high phenotypic plasticity as expressed by common plasticity indices, which is likely to be related to increased mortality under stress in more plastic populations.