RESUMO

In this work, we investigated surname distribution in 4,348,021 Honduran electors with the aim of detecting population structure through the study of isonymy in three administrative levels: the whole nation, the 18 departments, and the 298 municipalities. For each administrative level, we studied the surname effective number, α, the total inbreeding, FIT , the random inbreeding, FST , and the local inbreeding, FIS . Principal components analysis, multidimensional scaling, and cluster analysis were performed on Lasker's distance matrix to detect the direction of surname diffusion and for a graphic representation of the surname relationship between different locations. The values of FIT , FST , and FIS display a variation of random inbreeding between the administrative levels in the Honduras population, which is attributed to the "Prefecture effect." Multivariate analyses of department data identified two main clusters, one south-western and the second north-eastern, with the Bay Islands and the eastern Gracias a Dios out of the main clusters. The results suggest that currently the population structure of this country is the result of the joint action of short-range directional migration and drift, with drift dominating over migration, and that population diffusion may have taken place mainly in the NW-SE direction.

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RESUMO

BACKGROUND: estimating random isonymy is an important tool in assessing the genetic structure of communities since its magnitude is, roughly, four times the inbreeding coefficient FST. The aim was to estimate the isonymy values from 26 Garifuna villages at the Atlantic coast of Honduras. METHODS: surnames from databases of 26 communities obtained from Honduran Electoral Organism were analyzed. Random isonymy within communities and from the total was calculated, as well as associated common parameters. Lasker's genetic distances calculated from isonymy among pairs of communities were assessed. RESULTS: relatively high values of random isonymy when compared to other rural communities in the revised literature were found. Additionally, relatively short pairwise genetic distances among communities, and a positive correlation with geographic distances were found. CONCLUSIONS: results from this and other previously published articles are congruent with historic isolation of the communities and a recent tendency towards homogenization due to high intercommunity migration rates observed in males. We assessed isolation by distance in some extend. Population characteristics of Garifuna communities make them ideal for searching susceptibility genes involved in complex diseases.

Introducción: la estimación de la isonimia es una herramienta importante en la determinación de la estructura genética de las comunidades puesto que su magnitud es aproximadamente igual a cuatro veces el coeficiente de endogamia FST. Métodos: se analizaron los apellidos registrados en la base de datos de 26 comunidades del Tribunal Supremo Electoral de Honduras. Se calculó la isonimia aleatoria dentro de cada comunidad y en el total, así como diversos parámetros comunes asociados. Se determinaron las distancias genéticas de Lasker a partir de la isonimia calculada entre pares de comunidades. Resultados: se encontraron valores relativamente altos de isonimia aleatoria en comparación con otras comunidades rurales. Adicionalmente, se observaron distancias genéticas relativamente cortas y se encontró una correlación positiva con las distancias geográficas. Conclusiones: los resultados son congruentes con el aislamiento histórico de las comunidades y reciente tendencia a la homogenización por las altas tasas de migración masculina intercomunitaria. Las características de la población garífuna la hacen propicia para la realización de estudios destinados a la búsqueda de genes de susceptibilidad relacionados con enfermedades de herencia compleja.

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RESUMO

The human population structure of the Central Provinces of Costa Rica was analyzed through isonymic methods and the use of Electoral Registers (1990 and 2006). Four parameters that define, in a genetic and evolutionary context, this structure were estimated: the consanguinity due to random mating (Morton’s a-priori kinship Fii), the genetic isolation (Fisher’s α), the migration (Karlin-McGregor’s υ), and the degree of subdivision or population differentiation (Fst). The possible geographical distribution of these variables is shown by the use of a Principal Components Analysis (PCA). There is a coincidence between groups of counties obtained by similarity in surname diversity and their geographic location in the territory. Differences were found for the values of the components of consanguinity (F=15.6; p<0.05) and genetic isolation (F=14.38; p<0.05) between different sectors of the Central Provinces. There is an association between population density and the breaking up of genetic isolates and another possible association between the geography of the region, the migration patterns of individuals, and the consequent levels of inbreeding and genetic isolation. The differences in the values of population structure components, inbreeding and genetic isolation, between the different zones of the central region, allow the assumption of the existence of differences in gene frequencies. The migration of blocks of genes from the center to the periphery is also possible and the variation in this sense might be attributed mostly to changes in the components of the population structure: mating patterns, migration and the consequence of the effective population size in the genetic drift process. Rev. Biol. Trop. 57 (Suppl. 1): 371-379. Epub 2009 November 30.

Se analiza la estructura de varias poblaciones humanas de las provincias centrales de Costa Rica mediante métodos isonímicos y utilizando los Padrones Electorales (1990 y 2006). Se estimaron cuatro parámetros que definen, en un contexto genético y evolutivo, esta estructura: la consanguinidad por cruces aleatorios (a-priori Kinship de Morton ii), el aislamiento genético (Fisher), la migración (Karlin-McGregor) y el grado de subdivisión o diferenciación de las poblaciones (Fst). La posible distribución geográfica de estas variables se muestra utilizando un análisis de componentes principales. Existe una coincidencia entre grupos de cantones obtenidos por similitud en diversidad de apellidos y la localización geográfica de los mismos en el territorio. Se encontraron diferencias estadísticamente significativas en los valores obtenidos para los componentes de consanguinidad (F=15.6; p<0.05) y aislamiento genético (F=14.38; p<0.05) entre diferentes sectores de las provincias centrales. Existe una asociación entre la densidad poblacional y la quiebra de aislados genéticos y otra posible asociación entre la geografía de la región y los patrones de migración de individuos y los consecuentes niveles de endocruzamiento y aislamiento genético. Las diferencias en los valores de los componentes de consanguinidad y aislamiento entre diferentes zonas del territorio central permiten suponer la existencia de diferencias en frecuencias génicas. La migración de bloques de genes del centro a la periferia también es posible y la variación en este sentido podría atribuirse principalmente a cambios en los componentes de la estructura poblacional: patrones de cruces, migración y la consecuencia del tamaño efectivo de población en procesos de deriva genética.

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