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PubMedDate not supplied

Inbreeding effects on fertility and sterility: a case-control study in Saguenay-Lac-Saint-Jean (Québec, Canada) based on a population registry 1838-1971.

Effects of inbreeding on couples' fertility and primary sterility were investigated in five marriages between uncle and niece, 251 marriages between first-degree cousins, and 358 marriages between first-degree cousins once removed from Saguenay-Lac-Saint-Jean. Three control groups matched on the demographic and socioeconomic characteristics of the consanguineous couples were created. The number of children born to each couple was extracted from a computerized population registry. The level of primary sterility was found to be similar in all consanguineous and non-consanguineous groups. The mean number of children in all three consanguineous groups was not found to be significantly different from that calculated in their respective control groups (p > 0.05). These results are compatible with those obtained in virtually all the studies reported thus far in different populations.

Case-Control Studies↗
PubMedDate not supplied

Inbreeding incidence on biological fitness in an isolated mediterranean population: La Alta Alpujarra Oriental (southeastern Spain).

The incidence of parental inbreeding on biological fitness was analysed in a sample of the Alpujarrenian population. Fitness was estimated as the fertility and offspring viability from conception to reproductive age. The analysed sample represents about 45% of the population from the Alta Alpujarra Oriental in southeastern Spain, and includes 847 families and 2916 pregnancies. The results showed slightly higher reproduction in consanguineous marriages, but the differences observed were not statistically significant. Higher pregnancy numbers are usually interpreted as stemming from greater immunological compatibility of the mother and foetus and may also reflect the significantly higher early foetal viability in this population. According to other authors, the great number of births observed in Alpujarrenian consanguineous marriages is, in part, a reproductive compensation for increased perinatal and neonatal mortality found as a possible negative result of homozygous combinations of deleterious alleles.

Abortion, Spontaneous↗
PubMedDate not supplied

Endogamy and inbreeding since the 17th century in past malarial communities in the Province of Cosenza (Calabria, Southern, Italy).

Many authors stressed the importance of considering mating patterns, migration and consanguinity when analysing micro-geographic differences in the distribution of the frequency of genetic traits (thalassaemia and glucose 6 phosphate dehydrogenase deficiency (G6PD) in populations living in areas of past malarial endemy. Therefore, the present work was aimed at estimating the reproductive isolation of Calabria, an Italian region that experienced endemic malaria until very recently. The research was carried out on 15311 records of marriage from Parish Books of four villages located in the past malarial area, and four situated in the non-malarial region. Endogamy rates were high in every village and decreased only in the present century as a consequence of the breakdown of isolation. In the earlier periods, the rates ranged between 93-84% in non-malarial villages, and between 96-66% in the past malarial area. The rate of consanguineous marriages was low in all villages: in the malarial area it was 2.15% on average, whereas in the non-malarial villages it ranged between 2-16%. Its trend increased with time almost everywhere. Concerning values, differences between past malarial and non-malarial villages in earlier periods are not consistent as they ranged from 0.1 x 10(-3) to 1 x 10(-3). In the present century, however, a was higher in the non-malarial villages. Observed changes of the coefficient a since the 19th century are due to the increased frequency of first cousin marriages. Isonymy rates were lower than 2% in all past malarial towns in all periods, whereas in nonmalarial villages they ranged between 1.2-9.5% and increased with time. Inbreeding coefficients F are always higher than alpha values, but show the same trend with time. They were between 0.0006-0.0045 in past malarial towns, and between 0.0017-0.024 in non-malarial villages. In non-malarial villages Fn displayed noticeable negative values in two situations in the earlier periods. In conclusion, given the above mating patterns and the observed distribution of frequencies of G6PD deficient hemizygous and thalassemic heterozygous in the investigated villages, there is clear evidence in this area for the absence of any specific role of reproductive isolation and consanguinity on the distribution of genetic traits related to past malaria presence.

Consanguinity↗
PubMed2000

Local Competition, Inbreeding, and the Evolution of Sex-Biased Dispersal.

Using game theory, we developed a kin-selection model to investigate the consequences of local competition and inbreeding depression on the evolution of natal dispersal. Mating systems have the potential to favor strong sex biases in dispersal because sex differences in potential reproductive success affect the balance between local resource competition and local mate competition. No bias is expected when local competition equally affects males and females, as happens in monogamous systems and also in polygynous or promiscuous ones as long as female fitness is limited by extrinsic factors (breeding resources). In contrast, a male-biased dispersal is predicted when local mate competition exceeds local resource competition, as happens under polygyny/promiscuity when female fitness is limited by intrinsic factors (maximal rate of processing resources rather than resources themselves). This bias is reinforced by among-sex interactions: female philopatry enhances breeding opportunities for related males, while male dispersal decreases the chances that related females will inbreed. These results meet empirical patterns in mammals: polygynous/promiscuous species usually display a male-biased dispersal, while both sexes disperse in monogamous species. A parallel is drawn with sex-ratio theory, which also predicts biases toward the sex that suffers less from local competition. Optimal sex ratios and optimal sex-specific dispersal show mutual dependence, which argues for the development of coevolution models.

kin selection↗
PubMed1997

Quantitative trait loci differentiating the outbreeding Mimulus guttatus from the inbreeding M. platycalyx.

Theoretical predictions about the evolution of selfing depend on the genetic architecture of loci controlling selfing (monogenic vs. polygenic determination, large vs. small effect of alleles, dominance vs. recessiveness), and studies of such architecture are lacking. We inferred the genetic basis of mating system differences between the outbreeding Mimulus guttatus and the inbreeding M. platycalyx by quantitative trait locus (QTL) mapping using random amplified polymorphic DNA and isozyme markers. One to three QTL were detected for each of five mating system characters, and each QTL explained 7.6-28.6% of the phenotypic variance. Taken together, QTL accounted for up to 38% of the variation in mating system characters, and a large proportion of variation was unaccounted for. Inferred QTL often affected more than one trait, contributing to the genetic correlation between those traits. These results are consistent with the hypothesis that quantitative variation in plant mating system characters is primarily controlled by loci with small effect.

Chromosome Mapping↗
PubMed1988

Current versus historical population sizes in vertebrate species with high gene flow: a comparison based on mitochondrial DNA lineages and inbreeding theory for neutral mutations.

Using inbreeding theory as applied to neutral alleles inherited maternally, we generate expected probability distributions of times to identity by descent for random pairs of mitochondrial genotypes within a population or within an entire species characterized by high gene flow. For comparisons with these expectations, empirical distributions of times to most recent common ancestry were calculated (by conventional mtDNA clock calibrations) from mtDNA haplotype distances observed within each of three vertebrate species--American eels, hardhead catfish, and redwinged blackbirds. These species were chosen for analysis because census population size in each is currently large and because both genetic and life-history data are consistent with the postulate that historical gene flow within these species has been high. The observed molecular distances among mtDNA lineages were two to three orders of magnitude lower than predicted from census sizes of breeding females, suggesting that rate of mtDNA evolution is decelerated in these species and/or that long-term effective population size is vastly smaller than present-day population size. Several considerations point to the latter possibility as most likely. The genetic structure of any species is greatly influenced by historical demography; even for species that are currently abundant, mtDNA gene lineages appear to have been channeled through fairly small numbers of ancestors.

Animals↗
PubMed1986

Inbreeding and schizophrenia.

The unique situation that the Norwegian 1891 census included information on consanguineous relation between spouses and that first admissions to psychiatric hospitals by diagnosis were available for the years 1921-40, formed the basis for the present study. There are similarities between the pattern of inbreeding and admission rates in our rural communities, but we were unable to demonstrate any significant correlation. This is interpreted as due to selective avoidance in the choice of a marriage partner, particularly between near relatives. Good neighbourhood knowledge was an important factor in our sparsely populated communities with a marriage pattern distinguished by extreme geographical proximity of residence of spouses. The considerably lower proportion of first cousin matings than expected among parents of psychiatric in-patients 1926-55, illustrates the lower psychiatric morbidity in offspring of consanguineous parentage. Admissions 1921-40 comprised only functional psychoses with a predominance of schizophrenia (greater than 80%), which today is diagnosed in less than 10%. A decline in incidence rate is not likely, whereas changing diagnostic practice is probably a main factor. The near disappearance of catatonia and hebephrenia could be related to the introduction of psychotropic drugs and the accompanying improvement in hospital treatment. The epidemiology of schizophrenia is unchanged with a significant excess in lower social classes. This could in part be due to schizophrenic phenocopies related to the unchanged social differential in infant mortality and morbidity (including a particular season of birth effect), in part to the prevalence of adverse environment postnatally. The considerably greater male marital differential has probably a social cause, whereas male earlier onset of disease and more severe course of the disease are discussed in relation to the new concept of progressive sexual brain differentiation.

Adolescent↗
PubMed1998

Risk factors for mortality in young children living under various socio-economic conditions in Lahore, Pakistan: with particular reference to inbreeding.

Risk factors such as maternal age, parity, previous siblings' death, inbreeding of parents, birth weight, birth length were examined in a population-based prospective study in four population groups at different levels of urbanization in and round Lahore, Pakistan. From September 1984 to March 1995, 2967 full-term, single born infants were followed from the 5th month of gestation to 12 months of age. Logistic regression analysis showed a significant relative risk (RR) of infant death associated with parents' consanguinity (RR = 1.8), birth weight (RR = 1.8) and elder siblings' death (RR = 1.7). The risk attributed to these factors was 28, 17 and 25%, respectively. The number of lethal equivalents per gamete is about one. The B/A ratio 10.36 suggests that the genetic load is likely to be mutational. In countries like Pakistan, where consanguinity is favourably practiced, a substantial proportion of infant deaths may be prevented by cessation of such marriages. The implications of this finding for the Pakistani community are discussed.

Adolescent↗
PubMed1978

On the computation of inbreeding coefficients.

A method of calculating inbreeding coefficients is described using a recursive algorithm. This has been programmed in ALGOL 68 and in SNOBOL 4. Advantages and disadvantages of this method are discussed, and several examples are given.

Computers↗
PubMed1979

Trends in human reproductive wastage in relation to long-term practice of inbreeding.

The trends in reproductive performance and wastage are studied in relation to consanguinity of marriage and age of women on a population sample of 20,626 women, from the rural and urban areas of North Arcot District in South India. Data were collected by qualified women investigators using intensive interveiw techniques and specially developed questionnaires. Adequate quality control mechanisms were set up to ensure reliability of information gathered. For each marriage, a family pedigree was drawn extending upwards to two early generations on the side of each spouse in order to determine the existence and type of consanguinity married, 80% or more of such between an uncle and a niece or between first cousins. Altogher 70 161 total pregnancies were recorded for the 20,626 women. The differences between consanguineous and non-consanguineous marriages in terms of total foetal loss, perinatal, neonatal, postneonatl and infant mortality rates showed only marginal differences that attain statistical significance only because of the large sample size involved. No consistent relationships were observed between the degree of consanguinity and these reproductive losses. These actual differences were more marked in the older age-groups of women and declined to rather insignificant proportions as the age groups became younger. Taking into consideration the various socio-demographic factors, the narrowing differentials in the reproductive wastage between consanguineous and non-consanguineous marriages from the oldest to the youngest women confirm the tapering effects of continued inbreeding practices on the reproductive wastage. Further studies on these lines are still in progress.

Adult↗
PubMed1999

Inbreeding and cancer incidence in human isolates.

This study investigates the incidence of cancer in isolate populations. Thorough anthropological research over the past 3 decades has established island populations in Middle Dalmatia, Croatia, as outstanding examples of genetic isolates. The number of cancer cases on 5 islands (Brac, Hvar, Korcula, Vis, and Lastovo) over a 20-year period (1971-1990) has been extracted from the data of the Croatian Cancer Registry. The population of coastal Dalmatia, characterized by similar environmental factors but a different population genetic structure, was used as a control population. The leading hypothesis was that, if there were genes or gene complexes (especially with recessive inheritance) responsible for genetic susceptibility to certain types of cancer, then the incidence of those cancer types should be greater in reproductively isolated island populations than in a control population because of increased manifestation of such genes or gene complexes caused by inbreeding. Furthermore, the cancer incidence should increase along with greater reproductive isolation (i.e., greater geographic distance of the islands from the mainland). After adjusting the data for sex and age, I confirmed the hypothesis: Island populations have greater total cancer incidence than the control population for both sexes. The excess incidence on the islands shows an almost linear correlation with geographic distance from the mainland. The cancer sites primarily responsible for the excess incidence are bladder cancer in males, and breast, ovarian, brain, and large bowel cancer in females, predominantly in the younger age groups.

Adult↗
PubMed2000

Inbreeding, outbreeding, and heterosis in the yellow pitcher plant, Sarracenia flava (Sarraceniaceae), in Virginia.

The yellow pitcher plant, Sarracenia flava, is an insectivorous plant restricted to fire-maintained wetland ecosystems in southeastern Virginia. Only four natural sites remain in the state totaling fewer than 100 clumps. Plants from sites located in Dinwiddie, Greensville, Prince George, Sussex counties, and the city of Suffolk were tested for the effects of self-pollination, intrasite outcrossing, and intersite outcrossing on offspring quantity (total seed number and total seed mass) and offspring quality (avarage seed mass, germination, and growth).Self-pollination resulted in significantly lower offspring quantity and quality. Total seed number and total seed mass for self-pollinated capsules were approximately one-fourth that of outcrossed capsules. Germination, survivorship, and growth over 5 yr were also significantly lower for offspring from self-pollinated capsules. Together, these results suggest strong inbreeding depression in this species.Relative to offspring from intrasite crosses, offspring from intersite crosses were significantly larger after 5 yr of growth. This suggests that restoration efforts for Virginia S. flava will be most successful when plants from multiple sites are used.

Journal Article↗
PubMed2002

Inbreeding and nephrolithiasis in Croatian island isolates.

The aim of this study was to investigate a recessive genetic component in susceptibility to nephrolithiasis (NL) by comparing its prevalence in highly inbred, moderately inbred and non-inbred villages of three Croatian islands: Brac, Hvar and Korcula. The average inbreeding coefficient of each village population (F) was estimated in a random sample of 20-30% adults from 14 villages using Wright's path method (based on genealogical information), isonymy data and average deviation from Hardy-Weinberg expectations for MN, Ss and Kk serogenetic polymorphisms. The six villages with the greatest genealogical F value (0.025-0.049; current total population N=1,401), the four with intermediate value (0.012-0.015; N=998) and the four with the smallest value (0.002-0.008; N=1,500) were chosen for this study. Medical records of entire populations were reviewed and the diagnosis of NL was established according to unified criteria, based on the information from the specialists in general hospitals and on the agreement in diagnosis between the investigators and local general practitioners. The variance in environmental and socio-cultural factors between villages was shown to be minimal. Prevalence of NL in each village was standardised by sex and age to the total population of all 14 villages. The standardized prevalence of NL was 1.5% in the group of villages with low F, 2.3% in the group with moderate F (p<0.10), and 5.4% in the group with high F (p<0.001). The correlation factor between F values by villages and the standardized prevalence of NL was 0.45 (p<0.05). The study showed that a large number of predominantly recessive genetic factors might mediate the susceptibility to formation of renal stones in humans.

Consanguinity↗
PubMed1975

[Inbreeding characteristics of thepopulation and the distribution of schizophrenia in one of the rural regions of Azerbaijan].

The investigation was carried out in Pushkin region of Azerbaijan SSR. The coefficient of inbreeding was found to be 0,01142 in 2 typical villages; the frequency of consanguineaous marriage in both villages was 30+. The occurence of consanguineous marriage is explained by a little migration of the population, large families and a stability of marriage traditions. An increased frequency of parental consanguinities of sporadic schizophrenic patients in comparison with the average one was found. This indicates the determination of some cases by rare recessive genes.

Azerbaijan↗
PubMed2006

Class endogamy, inbreeding and migration during the Argentinean colonial period: analysis based on individuals of European ancestry.

During the Spanish colonial period, Córdoba was an important town due to its location suitable for controlling communication throughout a wide region of Argentina. As a typical colonial society, where individuals belonged to a well established social class, marriages among Whites were the result of strict norms and prejudices founded on nets of kinship, friendship and neighbouring. The objective of this paper is to determine, whether the elevated class endogamy among Whites during the colonial period resulted in high consanguinity and whether a process of selection of surnames was present in 1813. In both cases the interaction with the migratory flow was taken into account. It is concluded that (a) Although an endogamy of "class" existed among Whites, there is no evidence of the consequences on the biological structure of the population through preferential mating between relatives, as deduced from the low level of inbreeding from isonymy. (b) There was no differential reproduction reflecting the selection of families carrying certain surnames; therefore surnames followed a "neutral" model. (c) The diversity of surnames and the gene flow deduced from them were of a magnitude similar to present populations; this fact could have balanced the effect of the "class" endogamy. (d) Finally, the congruence between information derived from the population age distribution and historic data and the quantification of migration from surnames allowed the detection of mistakes in the census data file regarding the number of foreigners, thus validating the use of surnames as biological markers of the population structure.

Adolescent↗
PubMed1987

[The structure of the inbreeding coefficient in a rural Asian population].

The population-genetic study of an elementary rural population located in the Urgut district of Samarcand province was carried out. The pedigree for the whole population starting from the founders was evaluated. From 208 marriages presented in the population, 148 (71.2%) were consanguineous. The mean coefficient of inbreeding calculated from the pedigree was 0.028. A new approach to the evaluation of marital assortativity in a rural Uzbek population without tribial differentiation and inherited surnames was proposed. It consists in awarding artificial surnames to the founders of the population. Applying this approach to the population under study gives following values of F-statistics: FIT = 0.031, FIS = 0.01841, FST = 0.01282.

Consanguinity↗
PubMed1982

Inbreeding in a South-American newborn series.

Parental consanguinity was investigated in a series of 16, 137 non-malformed newborn infants, ascertained in 64 hospitals, of 27 cities, in seven South-American countries. Parental consanguinity was detected in 135 (0.84%) newborns, giving a mean inbreeding coefficient (a) of 0.00053. The subsamples for five of the seven countries (Brazil, Chile, Ecuador, Uruguay, Venezuela) showed similar consanguinity rates, of about one per cent, an a ranging from 0.00040 to 0.00070, approximately. One country, Argentina, had a three times lower value for both indicators: consanguinity rate: 0.3%, a: 0.00011. Another country, Peru, could not be individually analyzed because of its small sample size. Considering the whole South-American sample, first cousin represented 60% of all consanguineous matings. Significantly more female than male intermediate ancestors were counted in the specified total of consanguineous matings, suggesting a preferential consanguineous mating pattern for urban South-American populations.

Chromosome Aberrations↗