Interpopulation relationship by isonymy: application to ethnosocial groups and illegitimacy

The application of the isonymic method to establish interpopulation relationships is made difficult by such factors as: (1) a small population size; (2) the subdivision of the population into ethnosocial groups; and (3) the existence of individuals born extramaritally. The present study analyzes the validity of the isonymy method in populations where such difficulties exist. Lasker's R(ij) relationship coefficients were calculated in base to marital records from six Pocho parishes (Argentina) for the period 1766 to 1840. Three endogamous ethnosocial groups were considered-Spanish, American Indians, "Mestizos"--and a fourth group combining mates of the three previous groups. For each ethnosocial category, and taking into account paternal surnames, maternal surnames (both for legitimate and illegitimate mates), and whole surnames merged, R(i) interparish relationship matrices were obtained. All these matrices were correlated by means of the Mantel test. Maternal surnames of illegitimate mates show a similar pattern to the maternal surnames of legitimate mates and to all surnames of each category. Groups with larger sample size in every parish intercorrelate regardless of ethnosocial category. Results suggest the convenience of maximizing the sample size and using maternal surnames in populations with high illegitimacy.     

Coefficients of relationship by isonymy among the parents of Scottish twins: a test of familial aggregation

The ability of the coefficient of relationship by isonymy Ri to detect familial aggregation of conditions suspected of being under a degree of genetic control was tested on groups of fathers and mothers of like-sex twins, fathers and mothers of unlike-sex twins, and fathers and mothers of singleton controls born from 1977 to 1981 in Scotland. No statistically significant difference of within-group or between-group Ri was found, either for all surnames or for rare surnames only. However, the overall pattern of results for rare surnames showed a measure of agreement with what is already known of the genetics of twinning. The relatively high within-group Ri for mothers of unlike-sex twins is consistent with a maternal genetic influence on dizygous twinning, whereas the relatively high between-group Ri for fathers with mothers of unlike-sex twins suggests that paternal as well as maternal genes may be involved. Values of Ri for the parents of like-sex twins raise the possibility of a paternal but not a maternal genetic contribution to monozygous twinning.     

Comparison of two Venezuelan populations using the coefficient of relationship by isonymy

The coefficient of relationship by isonymy Ri is a good indicator of similarities between and within populations by means of identity of surnames. In this study we present the results of an analysis of Ri obtained using two surnames for each person in two small Venezuelan populations of African origin: Birongo and La Sabana. The analyses of six Ri values within each population in two periods and of sixteen Ri values within each population between two periods and within each period between populations show that the higher values of Ri are those that include combinations of maternal surnames compared with any other combination and that in one period the relationship between Birongo and La Sabana was equal to 0, as measured with combinations of paternal surnames. These facts are indicators of a tendency toward matrifocal behavior and show that the use of four surnames for estimating Ri permits detailed comparisons of the relationship between and within groups.     

Inbreeding and population subdivision in Córdoba province, Argentina, at the end of the eighteenth century

Marital isonymy is frequently used to estimate inbreeding and the repeated pairs method is useful to investigate whether the population under examination has subdivisions. These methods can also be applied to registers, such as population censuses, where both spouses' surnames are noted. In this paper, the 1795 census for Córdoba province is analysed. Numerically speaking, Spanish and mixed-race people are the major ethno-social groups in the register. In order to estimate inbreeding, the isonymic method was applied to both groups, at provincial and at parish level. To appreciate to what extent the parishes were genetically isolated, Wright's Fst was also calculated. The repeated pairs method was also used for both groups to assess if population subdivision existed in the units under study. Finally, to evaluate whether the subdivision based on surnames reflected the ethno-social stratification, the same method was used considering the two groups together. At the provincial scale, both groups displayed low inbreeding and micro-differentiation, although the former was higher for the Spanish and the latter for mixed-race groups, which could indicate a more marked conjugal selectivity in the Spanish. At the parish scale, preferences for isonymic spouses were not pronounced either in Spanish or in mixed-race groups; in the Spanish group population subdivision prevailed, with the opposite occurring in the mixed-race group. The estimations from repeated pairs, taking the two groups together, indicated that for the studied populations the surnames do not allow the two groups to be differentiated into isolated reproductive units.     

The names of Spain: a study of the isonymy structure of Spain

In order to estimate the isonymy structure of Spain, we studied surname distribution in 283 Spanish towns based on 3.625 million telephone users selected from 6.328 million users, downloaded from a commercial CD-ROM which contains all 13 million users in the country. Since in Spain the surname is made by the paternal and the maternal surname, it was possible to classify surnames according to parental origin. Two matrices of isonymy distances, one for paternal and one for maternal surnames, were constructed and tested for correlation with geographic distance. For the whole of Spain, Euclidean distance was significantly but weakly correlated with geographic distance both for paternal and maternal surnames, with r = 0.205 +/- 0.013 and r = 0.263 +/- 0.012, respectively. Two dendrograms of the 283 sampled towns were built from the two matrices of Euclidean distance. They are largely colinear. Four main clusters identified by the dendrograms are correlated with geography. Given the surname structure of Spain, we were able to calculate from isonymy and for each town 1). total or expressed inbreeding, 2). random or expected inbreeding, and 3). local inbreeding. Total inbreeding, F(IT), was highest in the North Atlantic regions and lowest along the Mediterranean Coast. The lowest levels were found in Andalusia, Catalunyia, Valencia, and Navarra. Random inbreeding, F(ST), had a similar geographical pattern. Local inbreeding, F(IS), was relatively uniform in the whole of Spain. In towns, random inbreeding dominates over local inbreeding. From the analysis, it emerges that the northwestern area of Spain is the most inbred.     

Cultural factor in the geographic distribution of personal names: pseudogenetic analysis of first names used to estimate the cultural component of coefficients of relationship by isonymy

By applying to given names formulations for analyzing the genetics of surname distributions, under certain assumptions one can separate the genetic components from the cultural components of surname distributions. Geographic distributions of surnames regularly yield larger coefficients of relationship or kinship within local populations than between them: for instance, Ri = 75 x 10(-5) within a local area in England but the Ri of those villages with all of England and Wales is 42 x 10(-5). On the contrary, the first names in an English and Welsh sample give essentially the same pseudocoefficient (based on first names) within registration districts (Ri = 354 x 10(-5) as between districts (Ri = 370 x 10(-5). Thus the decrease with distance of the coefficients based on surnames can be ascribed to the genetic component according to the Malécot principle, assuming that the first names are chosen in the same way as the surnames originated and consequently that the cultural component of surname distributions is no more localized than the distribution of given names (in this sample not at all).     

Different numbers of maternal and paternal siblings of cystic fibrosis patients

Summary When 458 parents of children suffering from cystic fibrosis (CF) from all over the German Democratic Republic were interviewed to determine the number of their siblings, it was found that the maternal families had a total of 1369 children and the paternal, 1220. While the fathers of CF patients tended to originate from families with one or two children, more mothers than fathers came from families with three to twelve children (P=0.01). The average number of children in the maternal families was 2.99; in the paternal families, only 2.66. To rule out any methodological errors, sibs of mothers and fathers of various control groups were studied. We found that the number of siblings in these groups was balanced. The differences in our findings are probably due to CF heterozygosity. The underlying mechanism is unknown.     

Coefficients of relationship by isonymy within and between the regions of Scotland

The distribution of surnames for births, marriages and deaths in 1976 among residents of the 12 Local Government Regions of Scotland was analyzed in terms of the coefficient of relationship by isonymy, Ri. Differences between sexes and events for Ri within Regions were consistent with greater inter-Region mobility among males compared with females and among young adults compared with the elderly. There were near zero correlations of geographical distance with Ri between Regions based on all surnames or common surnames. With Ri based on rare surnames, there was a small though statistically nonsignificant negative correlation. The best-fitting two dimensional relationship derived from Ri values based on rare surnames showed a fair correspondence with the map of Scotland, indicating a degree of genetic isolation between the Regions.     

Coeficient of relationship (RI) within and between four black venezuelan populations

The coefficient of relationship by isonymy R_i was obteined using paternal and maternal surnames of individuals in four black Venezuelan populations. The analysis of eight R_i values obtained from different combinations of surnames within each population and between population in two periods of time (1900–1920 and 1944–1967) show that: 1) Higher values of R_i are those that include combinations of maternal surnames, 2) R_i values of the second period are higher than those shown in the first, 3) No correlation was observed between R_i values and geographic distance. These results indicate that there is a tendency towards matrilocal behavior and show agreement with the degree of isolation of each population. The use of four surnames for estimating the coefficient of relationship by isonymy R_i, permits better comparisons of the relationship between and within groups and gives detailed information of the population structure.     

Namesakes or relatives? Approaches to investigating the relationship between Y chromosomal haplogroups and surnames

Population genetics successfully applies surnames as quasi-genetic markers when estimating similarity between populations and calculating a measure of random inbreeding. These calculations are based on an isonomy coefficient which assumes that every surname is monophyletic: that it originated from single common ancestor and all namesakes are therefore relatives. On the other hand, there is a general opinion that a typical Russian surname is polyphyletic: it originated multiple times and most namesakes are therefore not related to each other. Combined studies of Y chromosomes and surnames now allow us to address this issue. In this study, we discuss approaches for statistical evaluation of Y chromosomal haplogroup frequencies in groups of people bearing the same surname (namesakes). We propose an 'Index of Accumulated Haplogroup Frequency', which allows for errors due to random (artifactual) effects increasing a haplogroup frequency in a group of namesakes by subtracting the population frequency of this haplogroup. This population frequency is calculated as the weighted average of the frequencies of this haplogroup in the populations that the carriers of this surname come from. Fom the total sample (comprising 1244 persons from 13 populations of the historical Russian area) we chose 123 persons carrying 14 surnames which were the most frequent in the total sample. Haplogroup frequencies in these 14 "surname" groups were compared with the respective 14 "population" control groups compiled from the total sample as described above. We found that even these widespread surnames exhibit non-random accumulation of specific Y chromosomal haplogroups. More detailed analyses of the relationships between namesakes could be carried out using Y-STR haplotypes rather than Y-SNP haplogroups, and will be the subject of a future study.     

High ratio of illegitimate visitation by small bees severely weakens the potential function of heteranthery

Aims In heterantherous plants, 'division of labor' among structurally different stamens, i.e. pollinating and feeding functions, has been thought to reduce the evolutionary conflict of relying on pollen both as the carrier of male gametes and as the food for pollinators. The key to successful division of labor among different sets of stamens is the size match between stamens and legitimate pollinators, which results in the precise deposition of pollen onto specific locations on pollinator's body and facilitates cross pollination. However, the potential impact of small illegitimate insects that are ubiquitous during the pollination process on the plant reproduction in heterantherous species has been largely neglected in previous studies and never been demonstrated experimentally.Methods Here, we investigated the functions of three different types of stamens in Commelina communis. The pollinator visitation, pollen removal and deposition were compared among flowers with different types of anthers emasculated at two natural populations. Moreover, the mating systems of C. communis in wild populations were estimated using microsatellite markers.Important findings Our data showed that the main floral visitors for C. communis at the two studied populations were small illegitimate bees rather than legitimate pollinators, accounting for 77.5 and 92.2% of total flower visits, respectively. Flower manipulations in C. communis demonstrated that the two types of brightly yellow stamens separately functioned as 'deceptive attraction' and 'feeding' functions. Although the brown inconspicuous stamens of C. communis with the largest amount of fertile pollen had the potential function in offering pollen for cross pollination, the high ratio of illegitimate visitation by small bees significantly affected the dispersal and deposition of pollen from the pollinating anthers, and subsequently decreased the levels of outcrossing (t m = 0.23–0.32) in wild populations. Our work further confirmed that the size match between pollinators and the floral morphology is the prerequisite to successfully fulfill the functional differentiation among different sets of stamens in heterantherous plants. Local high ratio of illegitimate visitation by size unmatched insects could significantly weaken the potential functions of heteranthery, affecting the dispersal and deposition of functional pollen in heterantherous plants and further the whole mating systems.     

Namesakes or relatives? Approaches to investigating the relationship between Y chromosome haplogroups and surnames

Population genetics successfully applies surnames as quasi-genetic markers when estimating similarity between populations and calculating the level of random inbreeding. These calculations are based on the isonymy coefficient, which assumes that every surname is monophyletic, i.e., it originated from a single common ancestor and all namesakes are therefore relatives. On the other hand, there is a general opinion that a typical Russian surname is polyphyletic: it originated multiple times and most namesakes are, therefore, not related to each other. Combined studies of Y chromosomes and surnames now allow us to address this issue. This study discusses approaches to statistical evaluation of Y chromosome haplogroup frequencies in groups of people bearing the same surname (namesakes). The proposed index of accumulated haplogroup frequency eliminates the artifactual effect of a randomly increased haplogroup frequency in namesakes by subtracting its population (expected) frequency from the observed value, while the expected frequency is calculated as the weighted average of the frequencies of this haplogroup in the populations where the surname carriers come from. From the total sample (comprising 1244 persons from 13 populations of the historical Russian area), 123 individuals carrying 14 most frequent surnames were chosen. A comparison of the haplogroup frequencies in these 14 namesake groups and in 14 respective population control groups compiled from the total sample showed that accumulation of certain Y chromosome haplogroups was nonrandom even in carriers of widespread surnames. An analysis of Y-STR haplotypes rather than Y-SNP haplogroups could provide a better insight into relationships between namesakes and will be the subject of further research.     

Pollen transfer patterns in a distylous plant with overlapping pollen-size distributions

In this study we quantify the relative rates and amounts of between-morph (legitimate) cross-pollination, within-morph (illegitimate) cross-pollination and self-pollination in a natural population of distylous Gaertnera vaginata (Rubiaceae) endemic to the oceanic island of La Réunion in the Indian Ocean. Since pollen size distributions of each morph overlap we develop a method, based on chi-squared comparisons of observed to expected pollen size distributions, to quantify pollen transfer proficiencies. This method, unlike previous methods, does not assume an equal chance of pollen transfer for pollen grains in the region of overlap. The probability that a single pollen grain from a short-styled plant undergoes legitimate pollen transfer to long-styled flowers (4.19×10⁻²) was more than twice that for illegitimate transfer to other short-styled plants (1.56×10⁻²). In contrast, the probability that a single pollen grain from a long-styled flower undergoes legitimate pollen transfer to short-styled flowers (1.65×10⁻²) was no greater than that of illegitimate pollen transfer to other long-styled plants (2.15×10⁻²). The transfer proficiencies of individual pollen grains are thus highly asymmetric. However, because long-styled flowers produce significantly more pollen, the ratio of legitimate to illegitimate pollen on the stigmas of short-styled flowers (1.85) markedly exceeded that for long-styled flowers (1.11). Short-styled flowers incurred significantly higher levels of self-pollination than long-styled plants, emphasizing the importance for self-pollination to be removed before comparing stigmatic pollen loads. The method we propose could be applied to other distylous species with pollen size overlap between morphs and thus allow for a more widespread study of the pollination ecology of heterostylous species.     

DEMONSTRATION OF CRYPTIC INCOMPATIBILITY IN DISTYLOUS AMSINCKIA DOUGLASIANA

Hand pollinations experiments with distylous Amsinckia douglasiana A. DC. (Boraginaceae) revealed that legitimate (intermorph) crosses produce more seed than self-pollinations and that self-pollinations yield more seed than illegitimate (intramorph) crosses. We tested the occurrence of cryptic incompatibility in both style-length morphs by pollinating them with a mixture of legitimate and illegitimate pollen, each homozygous for a different electrophoretically distinguishable allele of phosphoglucose isomerase. The success of intramorph pollen was greatly reduced in mixture; only about 4% of the offspring of both pins and thrums were sired by illegitimate pollen. One pin and one thrum had sufficiently high seed set that the results cannot be attributed to selective abortion of embryos. In those individuals, discrimination against illegitimate pollen must have occurred on the stigma or in the style. Based on our findings, it appears that illegitimate matings are rare in natural populations. The progeny of legitimate crosses was biased toward pins, which suggests some regulation of morph ratios independent of the style-length locus. Prezygotic discrimination against the thrum genotype or selective abortion of embryos with the thrum genotype are both possible, but selective mortality of seedlings with the thrum genotype cannot be ruled out for some families.     

Genetic incompatibility and offspring quality in the tristylous plant Lythrum salicaria (Lythraceae)

The purpose of this study was to determine the incompatibility relationships among the three different morphs of the tristylous plant Lythrum salicaria, and to assess whether there are fitness consequences to breakdown in incompatibility. Twenty-four different types of pollinations were performed using all possible combinations of anthers and stigmas. These can be grouped as legitimate pollinations (pollinations from the appropriate anther level of a compatible morph), illegitimate intermorph pollinations (pollinations from the inappropriate anther level of a compatible morph), intramorph pollinations (pollinations between individuals of the same morph), and self pollinations. Legitimate pollinations produced significantly more seed than illegitimate intermorph pollinations, intramorph pollinations, and self pollinations. The difference between legitimate and illegitimate intermorph pollination success is particularly interesting because pollen for these crosses came from the same genetic individual. Pollination types also differed in offspring quality. In the rare examples where progeny were produced by illegitimate intermorph pollinations, the progeny did not have significantly lower values for seedling growth traits compared to legitimate progeny. Seedlings produced by self pollinations had significantly lower values for four out of six seedling growth traits measured. Comparisons of legitimate and self progeny traits indicate that inbreeding depression for most traits is close to or above 0.5. The finding that some seed were produced from illegitimate pollinations suggests that there is variation among individuals in incompatibility. There was a significant effect of parental morph type on the probability of breakdown in incompatibility with the midstyled maternal parents setting more seed from illegitimate pollinations.     

Introgression of Alectoris chukar genes into a Spanish wild Alectoris rufa population

In order to detect introgression of other Alectoris genus species into wild populations of Spanish Alectoris rufa, we studied a sample of 93 red-legged partridges (supposed to be A. rufa) captured in the island of Majorca. A set of 31 chukar partridges (Alectoris chukar) from Cyprus and 33 red-legged partridges (A. rufa) from one Spanish farm were also studied to provide suitable populations for comparison. Factorial correspondence analysis on microsatellite genotypes supported a clear distinction of birds from Cyprus, whereas partridges from Majorca and the Spanish farm overlapped in a wide area. The existence of A. chukar mitochondrial DNA in 16 individuals from Majorca indicated introgression into their maternal lineage even if their phenotypes were not different from A. rufa. Bayesian inference based on microsatellite analysis indicated a noticeable degree of genetic proximity to A. chukar only for one of these hybrids.     

CTG instability in myotonic dystrophy: molecular genetic analysis of families from south-eastern France with characteristics of intergenerational variation in CGT repeat numbers.

We report clinical, genetical and genealogical findings in 149 French families from the Rh?ne-Alpes area studied over a 5-year period. There was a significant excess of DM females compared to DM males with (CTG) repeat sizes between 1-2 kb. The mean maternal (CTG) repeat size was higher than paternal repeat size. Anticipation phenomenom was significantly higher after maternal than after paternal transmission. A significant correlation between parental (CTG) repeat size and intergenerational variation both in paternal and maternal transmissions was observed. The anticipation phenomenom was more important for sons than daughters particularly after maternal transmission. The mean (CTG) repeat size in mothers of CDM cases was about twice that of mothers of NCDM children. The risk of giving birth to a CDM child increased considerably when the number of maternal (CTG) repeats was over 300 (CTG). A significant excess of DM females was observed. They had on average 24% fewer children than male patients. Paternal transmission (63.6%) of DM occurred more frequently than maternal transmission (52.7%).     

Paternal kin discrimination: the evidence and likely mechanisms

One of the most important assumptions of kin selection theory is that individuals behave differently towards kin than non-kin. In mammals, there is strong evidence that maternal kin are distinguished from non-kin via familiarity. However, little is known about whether or not mammals can also recognize paternal kin as many female mammals, including primates, mate with multiple males near the time of conception, potentially concealing paternal kinship. Genetic data in several mammalian species with a promiscuous mating system and male-biased dispersal reveal a high skew in male reproduction which leads to co-residing paternal half-siblings. In most primates, individuals also form stable bisexual groups creating opportunities for males to interact with their offspring. Here I consider close paternal kin co-resident in the same social group, such as father-offspring and paternal half-siblings (i.e. animals sharing the same father but who were born to different mothers) and review mammalian studies of paternal kin discrimination. Furthermore, I summarize the most likely mechanisms of paternal kin discrimination (familiarity and phenotype matching). When familiarity is the underlying mechanism, mothers and/or the sire could mediate familiarity among paternal half-siblings as well as between fathers and offspring assuming mothers and/or fathers can assess paternity. When animals use phenotype matching, they might use their fathers' template (when the father is present) or self (when the father is absent) to assess paternal kinship in others. Available evidence suggests that familiarity and phenotype matching might be used for paternal kin discrimination and that both mechanisms might apply to a wide range of social mammals characterized by a high skew in male reproduction and co-residence of paternal kin. Among primates, suggested evidence for phenotype matching can often have an alternative explanation, which emphasizes the crucial importance of controlling for familiarity as a potential confounding variable. However, the mechanism/s used to identify paternal kin might differ within a species (as a function of each individual's specific circumstances) as well as among species (depending upon the key sensory modalities of the species considered). Finally, I discuss the possible cues used in paternal kin discrimination and offer suggestions for future studies.     

Twinning in humans: maternal heterogeneity in reproduction and survival

While humans usually give birth to singletons, dizygotic twinning occurs at low rates in all populations worldwide. We evaluate two hypotheses that have differing expectations about the effects of bearing twins on maternal lifetime reproduction and survival. The maternal depletion hypothesis argues that mothers of twins will suffer negative outcomes owing to the higher physiological costs associated with bearing multiples. Alternatively, twinning, while costly, may indicate mothers with a greater capacity to bear that cost. Drawing from the vast natural fertility data in the Utah Population Database, we compared the reproductive and survival events of 4603 mothers who bore twins and 54 183 who had not. These mothers were born between 1807 and 1899, lived at least to the age of 50 years and married once to men who were alive when their wives were 50. Results from proportional hazards and regression analyses are consistent with the second hypothesis. Mothers of twins exhibit lower postmenopausal mortality, shorter average inter-birth intervals, later ages at last birth and higher lifetime fertility than their singleton-only bearing counterparts. From the largest historical sample of twinning mothers yet published, we conclude that bearing twins is more likely for those with a robust phenotype and is a useful index of maternal heterogeneity.