Kinship by isonymy and by gene frequencies: A comparison of population structures at different hierarchical population levels

A comparison of population structures based on isonymy and on gene frequencies (ABO, Rh, Kell) was conducted for a sample of 28,205 individuals residing in three different provinces (Lucca, Massa Carrara, La Spezia) in northwest Italy, on the basis of both chronological and spatial subgroupings. Relationships between and within population subsamples were measured by means of kinship coefficients. The aim of this study was focused on kinship decay with geographic distance, associated with the great difference in location and variability between isonymic and genetic data. The analysis was carried out by R_st statistics and regression analysis to test the fit of the isolation by distance models. Further, the R matrices were converted into a distance measure, and Mantel's permutation test was used to assess the correlation across isonymy, genetic, and geographic matrices. Whereas estimates of R_st and isolation by distance parameters obtained from genetic and surname data pointed to a roughly comparable basic pattern of spatial differentiation in both chronological periods, the absolute values differ substantially. Both R_st and a isolation by distance parameters estimated from genetic data were higher than those from surnames, indicating greater local isolation by genetic analysis. The standard errors of b obtained from surname data were much smaller than those computed from genetic data, indicating that the kinship by isonymy coefficients fit Malècot's model better than the kinship coefficients estimated by the genetic data. Squared correlation coefficients among geographic, surname, and genetic distance matrices supported the above interpretations. The strong localization of surnames, the different level of variability in surname and gene frequency data, and random variations (due to the number of alleles considered) seem to be the main reasons for the observed differences between the two data sets. © 1996 Wiley-Liss, Inc.     

Barriers to gene flow estimated by surname distribution in Italy

Surname distributions were studied in order to reconstruct human migration patterns. Zones of sharp change in surname frequencies - presumably barriers to gene flow - were detected by the statistical technique of wombling (Barbujani et al. 1989), using data from consanguineous marriages (1910-64) collected from 280 Italian dioceses which we grouped into 80 provinces. The 28 observed surname boundaries were compared with physical (geographical) and cultural (linguistic) barriers, and with boundaries detected from distributions of 57 alleles in the same territorial subdivisions. Genetic and surname boundaries had similar locations, as expected given the analogy in the inheritance mechanism of genes and surnames. Physical barriers seemed to be the main cause of gene flow reduction. However, cultural factors alone (e.g. linguistic ones) also determined barriers that delimited areas of homogeneous gene (and surname) frequency probably due to increased endogamy. The observed similarity between spatial patterns of surnames, genes and languages supports the hypothesis of the co-evolution of genetic and linguistic variation.     

Genetic and population structure of four Sardinian villages

1. Data on microgeographic population structure on four neighbouring villages of Sardinia island (Italy) are presented and discussed.
2. Two villages are located in the lowlands where malaria from Plasmodium falciparum was endemic until the eradication of paludism. The other two villages are located in the highlands and they were malaria-free because of the altitude.
3. Census data, inbreeding, migration matrices and surname distributions have been collected. The genetic differentiation of the four villages, tested for 31 genetic polymorphisms (106 alleles), is only in part compatible with migration rates inferred from demographic data.
4. The possible adaptive nature of some genetic markers with respect to malarial resistance is discussed. Ambiguous results from population genetics quantitative methods do not support definite answers.     

Persistent genetic isolation in outport Newfoundland

The historical development of genetic isolation has been evaluated for three outport Newfoundland study areas. An attempt was made to ascertain all livebirths in each study area, and determine the parentage of each. Data from records of baptism and marriage were used for this, supplemented with other historical and ethnographic information. Parent-offspring migration was used as a measure of genetic exchange between subpopulations within study areas, and gene flow into the study areas. Currently, 1-8% of parents originate outside the study areas; these rates are low compared to earlier periods, and compared to present-day rates for European isolate populations. Average kinship was estimated, to measure genetic relatedness within and between subpopulations of each area and the potential for random inbreeding; these values, which are minimum estimates, are now at historically high levels. Increased migration into the study areas, which would decrease average kinship, is not likely. Thus, any regionally or locally elevated frequencies of deleterious alleles will persist, and must be taken into account in providing genetic counseling and evaluating the utility of local screening programs.     

Selective neutrality of surname,distribution in an immigrant indian community of Houston,Texas

From survey data on surnames in an immigrant community of Indians in Houston, Texas, it is shown that the family size distribution and the distribution of the number of male children per family are independent of the surnames of the parents. This provides a direct test of selective neutrality of surname distributions. A genetic theory of sampling distribution of neutral alleles is employed to estimate the parameter of the surname distribution, and analytical results for the expectation and variance of the frequencies of surnames with a different number of copies in a sample are provided. It is also shown that the surname distribution may indicate presence of mixture in a sample, which can be examined by such theoretical approaches. The transition of surname distributions in two successive generations is shown to follow the pattern predicted by random extinction of surnames.     

The distribution and geographical origin of some French surnames

The geographical distribution of the principal form of a French surname and its close variants (in spelling or pronunciation) has been analysed based on the French births registers, respectively from 1891 to 1915 and from 1916 to 1940, and on telephone directories for 1975. The spatial analysis of the individuals with the principal form of the surname suggests the existence of a positive spatial autocorrelation and three major areas of concentration in central France, the Loire country and Northern France. Within these three main areas of concentration, in 1975 most of the telephone subscribers with the principal surname are listed in rural communes with fewer than 3000 inhabitants, suggesting that the geographical pattern is not recent. Moreover, between the end of the 19th century and 1975 this pattern remains fairly constant. The geographical distribution of the holders of a 'variant' form of the surname shows the existence of a positive correlation between the absolute frequency of the principal surname and that of the variants, but only one area of concentration appears in Loire country. By analogy with the theory of centres of origin in genetics and linguistics, it is suggested that this unique area of concentration could be the region in which the surname originated. If that hypothesis proves to be correct, two main consequences follow: large migration movements occurred before the general rural exodus of the last century, and there has been no major, recent admixture of populations.     

Maternal age specific risk rate estimates for Down syndrome among live births in whites and other races from Ohio and metropolitan Atlanta, 1970-1989.

Our primary objective was to estimate, by one year and five year intervals, maternal age specific risk rates for Down syndrome among whites and among other races from two different populations, metropolitan Atlanta and south west Ohio, using live birth and prenatally diagnosed cases ascertained during 1970-1989. The five year estimates were also calculated separately for each of the five four year periods during these 20 years. Additionally, we compared two different methods of estimating these risk rates by using a third population of whites, and compared two different statistical methods of smoothing the risk rates. The results indicate good agreement between the metropolitan Atlanta and south west Ohio estimates within races, but show a statistically significant difference between the two race categories. Because 86% of live births in the "other races" category in the combined population are to blacks, these data may be seen as the first estimates of maternal age specific risk rates for Down syndrome among blacks calculated by one year intervals. We found excellent agreement in the risk rate estimates among the five four year time periods, between the estimates obtained by using the two different methods of estimation, and between the estimates obtained using the two different methods of statistical smoothing. Our estimated risk rates for white women in their 20s strongly reinforce those from previous studies currently being used for genetic counselling purposes. While we did find somewhat higher rates for women under 20, and increasingly higher rates for those over 30 years of age, these differences are not substantial. Thus, this study in general supports the risk rates estimated from data collected mostly during the 1960s and 1970s.     

Heterogeneity of long-distance migration in studies of genetic structure

One of the assumptions of migration matrix methods of population structure is that long-distance migrants are all sampled from a genetically homogeneous 'outside world'. This assumption has not often been tested. This paper examines migration and surname data from four towns in historical Massachusetts in order to examine this assumption and potential genetic effects of heterogeneous long-distance migration. Analysis of migration data shows that the rate of long-distance migration is significantly different for the four towns. The distributions of source populations for long-distance migrants into each town are significantly different. Surname analysis shows that in spite of the violation of the assumption of long-distance migrant homogeneity, there is little effect on the degree and pattern of within-group and among-group variation for these towns. This lack of effect seems related to genetic homogeneity of the long distance migrants.     

The distribution and geographical origin of some French surnames

Summary. The geographical distribution of the principal form of a French surname and its close variants (in spelling or pronunciation) has been analysed based on the French births registers, respectively from 1891 to 1915 and from 1916 to 1940, and on telephone directories for 1975. The spatial analysis of the individuals with the principal form of the surname suggests the existence of a positive spatial autocorrelation and three major areas of concentration in central France, the Loire country and Northern France. Within these three main areas of concentration, in 1975 most of the telephone subscribers with the principal surname are listed in rural communes with fewer than 3000 inhabitants, suggesting that the geographical pattern is not recent. Moreover, between the end of the 19th century and 1975 this pattern remains fairly constant. The geographical distribution of the holders of a 'variant' form of the surname shows the existence of a positive correlation between the absolute frequency of the principal surname and that of the variants, but only one area of concentration appears in Loire country. By analogy with the theory of centres of origin in genetics and linguistics, it is suggested that this unique area of concentration could be the region in which the surname originated. If that hypothesis proves to be correct, two main consequences follow: large migration movements occurred before the general rural exodus of the last century, and there has been no major, recent admixture of populations.     

Genome-wide comparative analysis of copia retrotransposons in Triticeae, rice, and Arabidopsis reveals conserved ancient evolutionary lineages and distinct dynamics of individual copia families

Although copia retrotransposons are major components of all plant genomes, the evolutionary relationships between individual copia families and between elements from different plant species are only poorly studied. We used 20 copia families from the large-genome plants barley and wheat to identify 46 families of homologous copia elements from rice and 22 from Arabidopsis, two plant species with much smaller genomes. In total, 599 copia elements were analyzed. Phylogenetic analysis showed that copia elements from the four species can be classified into six ancient lineages that existed before the divergence of monocots and dicots. The six lineages show a surprising degree of conservation in sequence organization and other characteristics across species. Additionally, the phylogenetic data suggest at least one case of horizontal gene transfer between the Arabidopsis and rice lineages. Insertion time estimates for 522 high-copy elements showed that retrotransposons from rice were active at different times in waves of activity lasting 0.5-2 million years, depending on the family, whereas elements from wheat and barley had longer periods of activity. We estimated that half of the rice copia elements are truncated or otherwise rearranged after approximately 790,000 yr, which is almost twice the half-life of Arabidopsis elements. In contrast, wheat and barley copia elements appear to have a massively longer half-life, beyond our ability to estimate from the available data. These findings suggest that genome size can be explained by the specific rate of DNA removal from the genome and the length of active periods of retrotransposon families.     

Y-chromosome diversity in Catalan surname samples: insights into surname origin and frequency

The biological behavior of the Y chromosome, which is paternally inherited, implies that males sharing the same surname may also share a similar Y chromosome. However, socio-cultural factors, such as polyphyletism, non-paternity, adoption, or matrilineal surname transmission, may prevent the joint transmission of the surname and the Y chromosome. By genotyping 17 Y-STRs and 68 SNPs in ~2500 male samples that each carried one of the 50 selected Catalan surnames, we could determine sets of descendants of a common ancestor, the population of origin of the common ancestor, and the date when such a common ancestor lived. Haplotype diversity was positively correlated with surname frequency, that is, rarer surnames showed the strongest signals of coancestry. Introgression rates of Y chromosomes into a surname by non-paternity, adoption, and transmission of the maternal surname were estimated at 1.5−2.6% per generation, with some local variation. Average ages for the founders of the surnames were estimated at ~500 years, suggesting a delay between the origin of surnames (twelfth and thirteenth centuries) and the systematization of their paternal transmission. We have found that, in general, a foreign etymology for a surname does not often result in a non-indigenous origin of surname founders; however, bearers of some surnames with an Arabic etymology show an excess of North African haplotypes. Finally, we estimate that surname prediction from a Y-chromosome haplotype, which may have interesting forensic applications, has a ~60% sensitivity but a 17% false discovery rate.     

Estimating inbreeding in large, semi-isolated populations: effects of varying generation lengths and of migration.

The purpose of the study reported here was to investigate two important assumptions used in a recently reported new method of estimating inbreeding in large, relatively isolated populations over historic times. The method, based on modeling the genealogical "paradox," produces values of Pearl's coefficients, Z, a measure of inbreeding or genealogical coalescence, as a function of time. In this study, the effects on inbreeding of two important assumptions made in earlier studies, namely those of using a constant generation length and of ignoring migration, have been investigated for the population of Britain. First, by relating the median age of women at childbirth to the development level of various societies, the variation of the generation lengths for different periods in historic Britain were estimated. Values of Z for two types of varying generation lengths were then calculated and compared with the case of constant generation length. Second, the population curve for Britain used in earlier studies was modified to obtain the subpopulation at any time during the past two millennia that was descended from the pre-Roman British Celts. Values of Z for the case with migration were then calculated and compared with the case for no migration. It is shown that these two assumptions may be taken into account if and when required. Both the effect of a varying generation length and the effect of migration on Z were found to be 20-40%, when no known value of inbreeding was used, and 2-5%, when a known value of inbreeding was used.     

Isonymy in records of births and deaths in Ferrara

Surname distributions were studied in records of male and female births in Ferrara in the period 1982-89, and in records of male and female deaths in the same period. Average year of birth and standard deviation was 1985 +/- 2.3 for the birth series, and 1912 +/- 14.4 for the death series. Then the surname distributions, in two independent samples at an average distance of 73 years, were compared. It was observed that random isonymy within series, which depends on the shape of the distribution, stays fairly constant at three generations of distance, indicating near-equilibrium of surname turnover. The migrational contribution is indicated by the significant decrease of random isonymy between series, measured with the method of Lasker. It was also observed that immigrants to Ferrara have a life-span significantly longer than people born in the town.     

Editorial

The distribution of surnames in 90 distinct regions in France during two successive periods, 1889–1915 and 1916–1940, is analysed from the civil birth registers of the 36,500 administrative units in France. A new approach, called ‘Mobile Site Method’ (MSM), is developed to allow representation of a surname distance matrix by a distorted geographical map. A surname distance matrix between the various regions in France is first calculated, then a distorted geographical map called the ‘surname similarity map' is built up from the surname distances between regions. To interpret this map we draw (a) successive map contours obtained during the step-by-step distortion process, revealing zones of high surname dissimilarity, and (b) maps in grey levels representing the displacement magnitude, and allowing the segmentation of the geographical and surname maps into ‘homogeneous surname zones’. By integrating geography and surname information in the same analysis, and by comparing results obtained for the two successive periods, the MSM approach produces convenient maps showing: (a) ‘regionalism’ of some peripheral populations such as Pays Basque, Alsace, Corsica and Brittany; (b) the presence of preferential axes of communications (Rhodanian corridor, Garonne valley); (c) barriers such as the Central Massif, Vosges; (d) the weak modifications of the distorted maps associated with the two periods studied suggest an extension (but limited) of the tendency of surname uniformity in France. These results are interpreted, in the nineteenth- and twentieth century context, as the consequences of a slow process of local migrations occurring over a long period of time.     

On a cell-growth model for plankton.

The frequency distribution of diatoms (microscopic unicellular alga with silicified cell-walls, found as plankton) is shown to evolve in time as a steady-size distribution with constant shape, scaled by time. This distribution is preserved when the division occurs at a fixed size into two daughter cells of half-size. In cases where the parameters for growth, division frequency, dispersion and mortality are constants, the frequency distributions can be found explicitly and thus provide a benchmark for computations in more complex cases.     

Frequency of recent retrotransposition events in the human factor IX gene

Two germline retrotransposition mutations of recent origin were observed in 727 independent mutations (0.28%) in the human factor IX gene (F9) of patients with hemophilia B: 1) a 279 bp insertion in exon H originating from an Alu family of short interspersed elements not previously known to be active and, 2) a 463 bp insertion in exon E of a LINE1 element originating in the maternal grandmother. If the rates of recent germline mutation in F9 are typical of the genome, a retrotransposition event is estimated to occur somewhere in the genome of about one in every 17 children born. Analysis of other estimates for retrotransposition frequency and overall mutation rates suggests that the actual rate of retrotransposition is likely to be in the range of one in every 2.4 to 28 live births.     

A spatial analysis of 100 surnames in England and Wales.

Spatial patterns are described and analysed for the 84 most common surnames in England and Wales, as well as 16 others selected for various reasons. At least three-quarters of the surname frequencies show spatial structure and are heterogeneous over the area of study. While they do not exhibit clines extending over the entire area of study, they do divide into four characteristics patterns. Spatial autocorrelation, while significant, is relatively low; similarity in surname frequency does not extend much beyond 100 km. Correlograms could be clustered to yield groups of surfaces denoting partial clines, isolation by distance, and differentiation at far distances. A method for detecting zones of rapid change found 21 such zones, mostly near the periphery of the study area. These boundaries do not indicate barriers to gene flow, but appear to be patterns brought about by historical factors. There are diffusion patterns between areas that differ greatly in surname composition, such as Wales and central England. There is little evidence of long-distance movements involving several surnames. At least three characteristic migration patterns, east-west and north-south diffusion and local dispersal, were found.     

Determination of the location and magnitude of synaptic conductance changes in spinal motoneurons by impedance measurements

The relation between impedance change and the location and magnitude of a tonic synaptic conductance was examined in compartmental motoneuron models based on previously published data. The dependency of motoneuron impedance on system time constant (tau), electrotonic length (L), and dendritic-to-somatic conductance ratio (rho) was examined, showing that the relation between impedance phase and rho differed markedly between models with uniform and nonuniform membrane resistivity. Dendritic synaptic conductances decreased impedance magnitude at low frequencies; at higher frequencies, impedance magnitude increased. The frequency at which the change in impedance magnitude reversed from a decrease to an increase-the reversal frequency, F(r)-was a good estimator of electrotonic synaptic location. A measure of the average normalized impedance change at frequencies less than F(r), cuDeltaZ, estimated relative synaptic conductance. F(r) and cuDeltaZ provided useful estimates of synaptic location and conductance in models with nonuniform (step, sigmoidal) and uniform membrane resistivity. F(r) also provided good estimates of spatial synaptic location on the equivalent cable in both step and sigmoidal models. Variability in relations between F(r), cuDeltaZ, and conductance location and magnitude between neurons was reduced by normalization with rho and tau. The effects on F(r) and cuDeltaZ of noise in experimental recordings, different synaptic distributions, and voltage-dependent conductances were also assessed. This study indicates that location and conductance of tonic dendritic conductances can be estimated from F(r), cuDeltaZ, and basic electrotonic motoneuron parameters with the exercise of suitable precautions.     

A Bayesian approach to infer geographical origins of migrants through surnames

BACKGROUND: Surnames are an easy tool to analyse human genetic structure, mobility and evolution. Few studies use surnames to estimate human migration at different geographical level. PRIMARY OBJECTIVE: Here we propose the application of a Bayesian method to estimate the probability of geographical origin (pgo) of migrants in a given area using surnames. METHOD: This method can be applied with data recordings when they are available for at least two successive periods and in the areas which are the potential sources of emigration. The principle is that the new surnames which are arriving during the second period in the area under investigation can provide information on their geographical origins. The probability of the origin of migrants can easily be estimated iteratively from the frequency of surnames by using the Bayes' theorem. RESULTS: This method is exemplified using civil birth registers at different geographical scales. The pgo of migrants, estimated between two periods (1891-1915 and 1916-1940), (i) from French departments to Paris (ii), from these departments to Tarbes, and (iii) from counties surrounding Tarbes to Tarbes, are mapped and discussed.     

Parametric analysis of ON- and OFF- responding for hypothalamic stimulation

Rats were trained to turn on and turn off lateral hypothalamic stimulation. The effects on ON- and OFF-responding of varying (a) the current intensity and (b) the pulse pair interval were assessed using the frequency threshold scaling method. No significant differences were found between the behaviorally determined refractory periods for ON- and OFF-responding. However, differences between the magnitudes of local potential summation effects for the two behaviors were significant. In addition, across-behavior differences in frequency-intensity trade-off functions were obtained. The results suggest that ON- and OFF-responding are mediated by different populations of directly stimulated neurons with different spatial distributions but similar distributions of excitability characteristics.