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Surname distribution can be a useful tool for studying the genetic structure of a human population. In South America, the Uruguay population has traditionally been considered to be of European ancestry, despite its trihybrid origin, as proved through genetics. The aim of this study was to investigate the structure of the Uruguayan population, resulting from population movements and surname drift in the country. The distribution of the surnames of 2,501,774 people on the electoral register was studied in the nineteen departments of Uruguay. Multivariate approaches were used to estimate isonymic parameters. Isolation by Distance was measured by correlating isonymic and geographic distances. In the study sample, the most frequent surnames were consistently Spanish, reflecting the fact that the first immigration waves occurred before Uruguayan independence. Only a few surnames of Native origin were recorded. The effective surname number (α) for the entire country was 302, and the average for departments was 235.8 ± 19. Inbreeding estimates were lower in the south-west of the country and in the densely populated Montevideo area. Isonymic distances between departments were significantly correlated with linear geographic distance (p < 0.001) indicating continuously increasing surname distances up to 400 km. Surnames form clusters related to geographic regions affected by different historical processes. The isonymic structure of Uruguay shows a radiation towards the east and north, with short-range migration playing a major role, while the contribution of drift, considering the small variance of α, appears to be minor.

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In Chile, the Hispanic dual surname system is used. To describe the isonymic structure of this country, the distribution of 16,277,255 surnames of 8,178,209 persons was studied in the 15 regions, the 54 provinces, and the 346 communes of the nation. The number of different surnames found was 72,667. Effective surname number (Fisher's α) for the entire country was 309.0, the average for regions was 240.8 ± 17.6, for provinces 209.2 ± 8.9, and for communes 178.7 ± 4.7. These values display a variation of inbreeding between administrative levels in the Chilean population, which can be attributed to the 'Prefecture effect' of Nei and Imaizumi. Matrices of isonymic distances between units within administrative levels were tested for correlation with geographic distance. The correlations were highest for provinces (r = 0.630 ± 0.019 for Euclidean distance) and lowest for communes (r = 0.366 ± 0.009 for Lasker's). The geographical distribution of the first three-dimensions of the Euclidean distance matrix suggests that population diffusion may have taken place from the north of the country toward the center and south. The prevalence of European plus European-Amerindian (95.4%) over Amerindian ethnicity (4.6%, CIA World Factbook) is compatible with diffusion of Caucasian groups over a low-density area populated by indigenous groups. The significant excess of maternal over paternal indigenous surnames indicates some asymmetric mating between nonAmerindian and Amerindian Chileans. The available studies of Y-markers and mt-markers are in agreement with this asymmetry. In the present work, we investigate the Chilean population with the aim of detecting its structure through the study of isonymy (Crow and Mange,1965) in the three administrative levels of the nation, namely 15 regions, 54 provinces, and 346 communes.

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To study the isonymy structure of Texas, we analyzed the surname distributions of 3.6 million telephone users registered for the year 1996 in 232 towns distributed in the 7 regions of the state. The number of different surnames was 235,740. Matrices of isonymy distances between towns and between geographic regions were constructed and tested for correlation with geographic distance. We found that isonymy distances between the seven regions showed borderline or no correlation with geographic distance, with r = 0.089 +/- 0.232, r = 0.492 +/- 0.232, and r = 0.337 +/- 0.232 for Lasker's, Euclidean, and Nei's distances, respectively. Isonymy distances between towns were significantly correlated with geographic distance, with r = 0.249 +/- 0.006 for Lasker's distance, r = 0.338 +/- 0.006 for the Euclidean distance, and r = 0.418 +/- 0.006 for Nei's distance. Two dendrograms, one for the 7 regions and one for the 232 towns, were built from the matrices of Nei's distances. The dendrogram for regions indicates that a main surname differentiation exists between the East and West areas of Texas, with West Texas being predominantly Hispanic and East Texas being predominantly English-speaking. The dendrogram for the towns confirms in detail the differences identified by the matrix of distances between regions. Random inbreeding calculated from isonymy, F(ST), was highest in the west and in the south of the state. It was lowest in the area of Austin and Houston. Average Fisher's alpha for towns was 734, for regions it was 1,047, and for Texas as a whole it was 1,230. The geographic distribution of alpha in the state shows distinctly lower values in the traditionally Hispanic west and higher values in the east and on the Gulf of Mexico.

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Surname distribution may be used as a substitute for quantitative information on the genetic structure of human populations due to panmictic deviations. This study analysed the isonymic structure of the Argentine Northwest (ANW) populations. Surname distribution of 2,576,548 voters (year 2001) in the 117 departments of the region was analysed. Fisher's alpha and coefficient of random relationship by isonymy were estimated. A dendrogram of the 117 departments was constructed from the matrix of Euclidean distances. In general, alpha values found were lower than country averages, while kinship values were higher. Ten clusters were identified showing a spatial distribution closely related to geographic characteristics, means of communication, and location of economic activities of the region. The resulting pattern could be basically characterized by grouping the departments into two large clusters: (a) Those located in the centre of the region, which include the provincial capitals, presented greater diversity of surnames and a lower degree of kinship. (b) Those located in the regional periphery showed greater isolation and kinship. Isonymic parameters estimated agree with the demographic characteristics of populations, historical antecedents of population settlement and ANW geographic features.

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In order to study the isonymic structure of Argentina, the surname distributions of 22.6 million electors registered for the year 2001 were analyzed in the 24 districts (distritos) and 541 municipalities (municipios) of the country. The number of different surnames found was 414,441. Matrices of isonymic distances between districts were constructed and tested for correlation with the geographic distance between the capital towns of the districts. We found that, for the whole of Argentina, Euclidean distance was correlated with the log of geographic distance (r=0.480+/- 0.067). A dendrogram of the 24 regions was built from the matrix of Euclidean distances, using the UPGMA method. The clusters identified by the dendrogram are coincident with conterminous geographical regions of the country. Random inbreeding calculated from isonymy, F(ST), was highest in La Rioja, Corrientes, and Santiago del Estero. It was lowest in the area of Buenos Aires and in the north-central region of Santa Fé. Average Fisher's alpha for municipalities was 358; for districts, it was 422; and for Argentina as a unit, it was 602. The geographical distribution of alpha in 541 municipalities, high in the east and lower in the west of the country, is compatible with the settlement in the 20th century of subsequent waves of immigrants moving from the North Atlantic coast toward the foot of the Andes and toward the south. The present structure of Argentina indicates that migration dominates over drift.

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BACKGROUND: The present Venezuelan population is the admixture product of Amerindians, Europeans and Africans, a process which was not homogeneous over the country. Blood groups, STRs and VNTRs, specifically D1S80, have been used successfully in admixture studies, but few have been made in Venezuela. AIM: This study aims to estimate the admixture components of Churuguara, Venezuela, and to evaluate the genetic relationship of this population with other Venezuelan as well as worldwide populations through principal component analysis and the study of dendrograms based on genetic distances. SUBJECTS AND METHODS: Gene frequencies of blood groups ABO and Rh (only anti D), of STRs VWA, F13A01, FES/FPS and VNTR D1S80 were studied in a sample of 60 individuals born in Churuguara, a Venezuelan town of admixed ancestry in the State of Falc6n. Admixture was estimated with Chakraborty's gene identity method, and Nei's standard genetic distance was used to build two dendrograms with the neighbour-joining approach, one based on the three STRs and the other based only on D1S80. Principal component analyses with the gene frequencies of these markers were also performed. RESULTS: The frequency of allele ABO*O was 0.788, of ABO*A was 0.187 and of RH*D was 0.74. D1S80 showed 16 different alleles with a heterozygosity of 0.880, whilst the three STRs showed only eight different alleles and heterozygosities between 0.733 and 0.797. The estimates of admixture obtained in this analysis were 52.5% for the Spanish parental group, 27.6% for the African and 19.9% for the Amerindian. Comparison of Churuguara with other Latin American populations shows that its African component is not as high as that observed in Colombian Choco, but it is higher than that observed in other samples from Colombia, Chile and Maracaibo (Venezuela). CONCLUSIONS: Results of the admixture analysis are consistent with those obtained with two dendrograms and principal component analyses, suggesting that the strong initial Amerindian component of 500 years ago has been diluted by the continuous flow of European genes, mainly Spanish, to this region.

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Eleven MHC loci haplotypes have been defined among a Carib speaking Amerindian population; the Yucpa, inhabiting the northern section of the Perija Range, on the limits between Colombia and Venezuela. This tribe has been known with the name of "Motilones mansos" and is located close to the Chibcha-Paeze speaking Bari or "Motilones bravos." Seventy-three full blooded Yucpa living at the villages of Aroy, Marewa, and Peraya, were selected using a genealogy previously collected by an anthropologist and tested for Bf-C4AB complement allotypes and by serology, high resolution PCR-SSO and SBT typing for HLA class 1 and class 2 alleles. Combinations of 6 HLA-A, 6 HLA-B, 5 HLA-C, 1 Bf, 3 C4AB, 3 DQA1, 3DQB1 and 2 DPA1 and 2 DPB1 alleles present in this population originate 17 different haplotypes, 3 of which represent 63% of the haplotypic constitution of the tribe. The presence of 13 individuals homozygous for 11-loci haplotypes corroborates the existence of the following allelic combinations: DRB1*0411 DQA1*03011 DQB1*0302 DPA1*01 DPB1*0402 with HLA-A*6801 C*0702 B*3909 BfS C4 32 (f = 0.3372) or with A*0204 C*0702 B*3905 (f = 0.1977) and a third haplotype which differs only in DRB1*0403 and A*2402 (f = 0.0930). The results demonstrate the isolation of the tribe and the existence of high frequencies of a reduced number of "Amerindian" ancestral and novel class 1 and class 2 alleles (B*1522, DRB1*0807) with significant linkage disequilibria. These results will be useful to test the hypothesis that differentiation of Amerindian tribal groups will have to rely on haplotypes and micropolymorphism rather than allelic lineage frequencies due to the uniformity shown thus far by the putative descendants of the original Paleo-Indians.

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Isolation by distance in Switzerland was detected comparing the surname distributions between Cantons. The decay of isonymy with geographic distance between Cantons was consistent with Malecot's exponential decay of kinship. Lasker's distance was defined as the negative value of the logarithm of isonymy between localities, and it was found that it is linearly and significantly correlated with the log of geographic distance, both within and between languages. The peculiar geographic and linguistic structure of the Confederation, where mountain barriers exist at short distances separating different languages, might explain the rapid changes in surname similarity. It was predicted that the frequency of markers linked to the Y chromosome would show a similar association with distance in Switzerland.

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The isonymy structure of Germany was studied using the surname distributions of 5,150,310 private telephone users selected from 39,000,000 users registered in a 1996 commercial CD-ROM, which contains all telephone users in the country. The users were distributed in 106 towns selected on a geographic basis. Germany was subdivided into 50 adjacent rectangles, each 115 x 80 km, and at least the largest town in the rectangle was selected for study; the private telephone users in that district were downloaded from the CD-ROM and included in the analysis. The shortest distance between nearest neighbor towns was 10.7 km (Travemunde and Lübeck), and the largest distance was 69.8 km (Meppen and Osnabruck). The number of different surnames found in the whole analysis was 462,526. Lasker's distance, the negative value of the logarithm of isonymy between localities, was found to be linearly and significantly correlated with geographic distance (r = 0.51 +/- 0.010). A dendrogram was built with the matrix of isonymy distances, using UPGMA. This method separates the German towns into two main clusters, one in the southern half of the country and the other in the northern half. Within each cluster small subclusters with specific geographic distributions could be delimited. The two main clusters correspond fairly well to the north-south division of German sublanguages (Nieder- and Mitteldeutsch in the north vs. Frankisch-Alemannisch in the south). The other clusters are related to minor sublanguages. Comparisons with the results of a previous analysis of Switzerland's structure are given. From the present analysis isolation by distance emerges clearly, although it is less strong than in Switzerland and indicates that Germany has a fairly homogeneous isonymy structure. The random component of inbreeding estimated from isonymy indicates that eastern Germany is on average more inbred than western Germany.

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The genetic structure of Zulia State, Venezuela, was studied through the distribution of surnames from individuals above 40 years of age, obtained from the register of electors. The sample studied consisted in 440, 190 individuals and 10,423 different surnames. For each of the 81 counties of the State, the following estimators were calculated: percentage of the population included in surnames which appear only once (estimator A), percentage of the population included in the seven most frequent surnames (estimator B), the coefficient of consanguinity due to random isonymy phi ii, and Karlin and McGregort's ni (v), an estimator of migration. The correlation between phi ii and B was 0.92, indicating that 85% of the variation observed in the coefficient of consanguinity due to random isonymy is due to the seven most frequent surnames. The correlation between A and ni was 0.93, so that 86% of the variation observed in ni, is due to surnames which appear only once. On the other hand, correlations between A and B, and between phi ii and v were non significant (-0.08 and -0.17 respectively), meaning that they are measuring different features of population structure: B and phi ii, isolation, while A and v, migration. The most isolated counties of Zulia are localized towards the northwestern portion of the State, within the Venezuelan Guajira, although relative isolation is also observed in the southern counties. Isolation by distance is estimated through the correlation between the logarithmic transformations of Euclidean and geographic distances, giving a value of 0.63. This high value might be partially due to the barrier effect of the Lake of Maracaibo. Eight surnames with a focal distribution within Zulia were identified: Almarza, Badell, Bastidas, Bohórquez, Cardozo, Carmona, Espina and Matos. Carriers of these surnames have a high probability of having their origin at the counties where they are localized.

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The isonymy structure of two Venezuelan states, Sucre and Táchira, is described using the surnames of the Register of Electors updated in 1991. The frequency distribution of surnames pooled together by sex was obtained for the 57 counties of Sucre and the 52 counties of Táchira, based on total population sizes of 158,705 and 160,690 individuals, respectively. The coefficient of consanguinity resulting from random isonymy (phi ii), Karlin and McGregor's ni (identical to v), and the proportion of the population included in surnames represented only once (estimator A) and in the seven most frequent surnames (estimator B) were calculated for each county. RST, a measure of microdifferentiation, was estimated for each state. The Euclidean distance between pairs of counties within states was calculated together with the corresponding geographic distances. The correlations between their logarithmic transformations were significant in both cases, indicating differentiation of surnames by distance. Dendrograms based on the Euclidean distance matrix were constructed. From them a first approximation of the effect of internal migration within states was obtained. Ninety-six percent of the coefficient of consanguinity resulting from random isonymy is determined by the proportion of the population included in the seven most frequent surnames, whereas between 72% and 88% of Karlin and McGregor's ni for Sucre and Táchira, respectively, is determined by the proportion of population included in surnames represented only once. Surnames with generalized and with focal distribution were identified for both states, to be used as possible indicators of the geographic origin of their carriers. Our results indicate that Táchira's counties, on average, tend to be more isolated than Sucre's counties, as measured by RST, estimator B, and phi ii. Comparisons with the results obtained for other. Venezuelan states and other non-Venezuelan populations are also given.

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The genetic structure of the State of Guárico, Venezuela, was studied through the distribution of surnames from individuals above 40 years of age, obtained from the register of electors. The sample studied consisted in 109,200 individuals and 14,138 different surnames. For each of the 32 counties of the State, the following estimators were calculated: percentage of the population included in surnames which appear only once (estimator A), percentage of the population included in the seven most frequent surnames (estimator B), the coefficient of consanguinity due to random isonymy (n phi ii), and Karlin and McGregors ni nu, an estimator of migration. The correlation between n phi ii and B was 0.97, indicating that 94% of the variation observed in the coefficient of consanguinity due to random isonymy is due to the seven most frequent surnames. The correlation between A and ni was 0.93, so that 86% of the variation observed in ni, is due to surnames which appear only once. On the other hand, correlations between A and B, and between n phi ii and nu were non significant (0.25 and 0.01 respectively), meaning that they are measuring different features of population structure: B and n phi ii, and v were non significant (0.25 and 0.01 respectively), meaning that they are measuring different features of population structure: B and n phi ii, isolation, and A and nu, migration. The most isolated counties of Guárico, according to n phi ii and B, are Santa Rita, Espino, El Calvario, Ortiz and Santa María de Ipire. Microdifferentiation of the State was studied through the estimation of RST, which gave a value of 0.0008. Comparing this value with those obtained in other Venezuelan States, it is found that Guárico, with Aragua and Yaracuy, are among the least differentiated States, probably because of the absence of important geographical barriers and the nearness to the Capital City of our country.

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Panaquire is a population in Venezuela founded in 1733 by Spaniards from the Canary Islands. In order to define the genetic characteristics of this population the following loci were studied: ABO, RH (Cc, D, Ee), FY, K, JK, HB, ESD, ACP1, HP, TF, CP and ALB. Its sociohistorical features were also investigated. Historic censuses reveal that ethnically Blacks were the most important group in this village during the year 1800 (76%), followed by Amerindians (9%), Mulattoes (5%) and Whites (7%). The results of this analysis show that presently the most important genetic component is of African origin (59%), followed by Amerindian (26%) and Caucasian (15%) contributions. These results suggest that Canarians founded Panaquire, but unfavorable sociopolitical and environmental circumstances, as well as the entrance of former slaves, determined the village's evolution as a Black population. Important gene flow also occurred from Indian settlements, and some admixture with Whites. Our analysis shows once again the importance of handling together genetic and sociocultural variables to have a better interpretation of the evolution of human populations.

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The distribution of surnames in the population of the Comune of Perugia, as it existed in the memory banks of the Municipality Computer in autumn 1991, was studied by age and place of birth. Fisher's alpha and Karlin-McGregor's v were estimated in the total population, in persons born before 1901, and in persons born in the nine decades thereafter, ending with the period 1981-1991, for immigrants and for natives of Perugia, respectively. The wealth of surnames was significantly higher in immigrants than in natives of Perugia, as detected by alpha, v and by the log-log regression of the corresponding distributions. Among residents born in Perugia, Fisher's alpha shows a minimum value during 1921-1930, explained as a consequence of the First World War. The relationship between all possible combinations of cohorts born in the 10 different decades was studied through the Euclidean distance and through Lasker's coefficient of relationship, and a significant correlation between the former and time was revealed, both in immigrants and in natives of Perugia. When compared with the Province of Ferrara, Perugia was far richer in surnames, as measured by Fisher's alpha, for the total population and for each of the 10 decades analysed. Recent immigration, measured by Karlin-McGregor's v, was significantly higher in Perugia until the 1960s, equal in both Provinces during the 1970s, and higher in Ferrara during the 1980s.

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The isonymy structure of four Venezuelan States-Falcón, Mérida, Nueva Esparta and Yaracuy-was studied using the surnames of the Venezuelan register of electors updated in 1984. The surname distributions of 155 counties were obtained and, for each county, estimates of consanguinity due to random isonymy and Fisher's alpha were calculated. It was shown that for large sample sizes the inverse of Fisher's alpha is identical to the unbiased estimate of within-population random isonymy. A three-dimensional isometric surface plot was obtained for each State, based on the counties' random isonymy estimates. The highest estimates of random consanguinity were found in the States of Nueva Esparta and Mérida, while the lowest were found in Yaracuy. Other microdifferentiation indicators from the same data gave similar results, and an interpretation was attempted, based on the particular economic and geographic characteristics of each State. Four different genetic distances between all possible pairs of counties were calculated within States; geographic distance shows the highest correlations with random isonymy and Euclidean distance, with the exception of the State of Nueva Esparta, where there is no correlation between geographic distance and random isonymy. It was possible to group counties in clusters, from dendrograms based on Euclidean distance. Isonymy clustering was also consistent with socioeconomic and geographic characteristics of the counties.

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The genetic structure of the State of Aragua, Venezuela, has been studied through the analysis of surnames obtained from the register of electors. The analysis covered 23 counties and included a total of 99,593 individuals and 6,338 different surnames. Estimators of isolation, consanguinity, microdifferentiation and four measures of genetic distance, were studied. When our results were compared with those obtained in other States of Venezuela studied previously (Falcón, Lara, Mérida, Nueva Esparta and Yaracuy), Aragua appears as the State most open to new migrants, probably due to its nearness to Caracas, Venezuela's capital city. Within Aragua, the counties most isolated are Choronií, Ocumare de la Costa and Tovar, while those less isolated are El Limón, Turmero, La Victoria, San Mateo and Cagua. The correlations between the logarithmic transformations of genetic and geographic distances were all significant, revealing surname differentiation by distance. The dendrogram built with the Euclidean distance matrix shows a first group of counties formed by those localized towards the central portion of the State, to which southern counties are added. Choroní and Ocumare de la Costa form a group which enters the dendrogram just before Tovar, the last county to be included in the analysis. Seven surnames with a focal distribution within the State were identified: Ayala and Calanche in Choroní; Kanzler, Misle and Ruh in Tovar; Lira in San Mateo and Santaella in Barbacoas.

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Genetic distances between all possible pairs of counties (n = 37) in the state of Lara, Venezuela were calculated using surname frequencies and the Euclidean distance as estimator. In general, Euclidean distances were smaller between counties closer together, and the product moment correlation between geographic and Euclidean distances was 0.49 (p < 0.02). The results suggest that, in Lara, geographic distance has been an important determinant of genetic structure, although topography and roadways also have had an important influence upon this structure.

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