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PubMed2001

Evaluation of d2, a microsatellite measure of inbreeding and outbreeding, in wolves with a known pedigree.

We have evaluated a microsatellite measure proposed as an indicator of inbreeding and outbreeding using a captive wolf population with known inbreeding levels and founder sources. The measure, which is based on the difference in the repeat number for microsatellite alleles within an individual, was not more predictive of the known inbreeding coefficient than microsatellite heterozygosity (it was actually less predictive). We also found no support that the measure was predictive of the level of outbreeding. However, we could not determine if the measure was predictive of very low levels of inbreeding due to matings between remote relatives. Overall, it appears that the usefulness of this measure to identify individuals on the inbred-outbred continuum beyond that of heterozygosity and identify biologically important associations with fitness-related traits may be limited. We suggest that the measure be examined theoretically to determine when (and how much) the predictive value of the measure is different from that of heterozygosity for inbreeding or outbreeding levels in a variety of different scenarios.

Analysis of Variance↗
PubMed2001

The evolution of trade-offs: effects of inbreeding on fecundity relationships in the cricket Gryllus firmus.

The evolution of traits is modulated by their interrelationships with each other, particularly when those relationships result in a fitness trade-off. In this paper we explore the consequences of genetic architecture on functional relationships between traits. Specifically, we address the consequences of inbreeding on these relationships. We show that the linear regression between two traits will not be affected if there is no dominance genetic variance in either trait, whereas the intercept but not the slope of the regression will change if there is dominance genetic variance in one trait only. We test the latter hypothesis using fecundity relationships in the cricket Gryllus firmus. Data from pedigree analysis and an inbreeding experiment show that there is significant dominance genetic variance in fecundity, but not head width (an index of body size) or dorsal longitudinal muscle (DLM) mass. Fecundity increases with head width, but decreases with DLM mass. As predicted, the intercepts of the regressions of fecundity on these two morphological traits decrease with inbreeding, but there is little or no change in slope. Gryllus firmus is wing dimorphic, with the macropterous (LW) morph having a lower fecundity than the micropterous (SW) morph. We hypothesize that the difference in fecundity arises primarily because of a competition for resources in the LW females between DLM maintenance (i.e., mass) and egg production. As a consequence, we predict that the fecundity within each morph should decline linearly with the inbreeding coefficient at the same rate in both morphs. The result of this will be a change in the relative fitness of the two morphs, that of the SW morph increasing with inbreeding. This prediction is supported. These results indicate that trade-offs will evolve and such changes will affect evolutionary trajectories by altering the pattern of relationships among fitness components.

Animals↗
PubMed2005

Environmental variation influences the magnitude of inbreeding depression in Cucurbita pepo ssp. texana (Cucurbitaceae).

We grew inbred and outcrossed Cucurbita pepo ssp. texana plants and measured inbreeding depression for several male and female fitness traits 4 years in a row in adjacent fields at the same field station under the same cultivation conditions. We found that the magnitude of inbreeding depression varied from 0.16 to 0.53 from year to year and that those traits which were most affected tended to vary with year. We also grew inbred and outcrossed C. pepo ssp. texana plants in two adjacent fields differing only in the presence of nitrogen fertilizer to examine the effect of nutrient limitation as a form of environmental stress on the magnitude of inbreeding depression. We found that inbreeding depression was more severe in the unfertilized field. Overall, this study illustrates the notion that any estimate of inbreeding depression represents a single point in a cluster of possible estimates that can vary (often dramatically) with growing conditions.

Adaptation, Physiological↗
PubMed2006

Inbreeding and reproduction in endangered ungulates: preservation of genetic variation through the Organization of Genetic Resource Banks.

There is a constant increase in the number of species suffering marked reductions in population size. This reduction in size and the lack of genetic flow may lead to a decrease in genetic variability and to matings between close relatives (i.e. inbreeding) with an ensuing reduction in fitness. It is thus important to understand the mechanism underlying the deleterious effects of inbreeding and to develop reproductive biotechnologies that will allow the reduction of inbreeding depression by facilitating gene exchange between populations. The study of three endangered species of gazelles, Cuvier's gazelle (Gazella cuvieri), Mohor gazelle (Gazella dama mhorr) and dorcas gazelle (Gazella dorcas neglecta) has revealed that inbreeding negatively affects several semen parameters (motility, sperm morphology, acrosome integrity). Semen cryopreservation has been achieved in the three species but success varies depending on the diluent employed and the level of inbreeding. Artificial insemination of Mohor gazelles have led to the birth of the first gazelle born using frozen-thawed semen but improvements are needed before this technology can be applied on a routine basis for the genetic management of the populations. Collection of oocytes after ovarian stimulation, followed by in vitro maturation, fertilization and culture has met with some initial success in the Mohor gazelle. These, together with other reproductive technologies, will offer an invaluable help in preserving the maximum of genetic diversity of these and related endangered ungulate species.

Animals↗
PubMed2006

Prediction of genetic gain from quadratic optimisation with constrained rates of inbreeding.

There are selection methods available that allow the optimisation of genetic contributions of selection candidates for maximising the rate of genetic gain while restricting the rate of inbreeding. These methods imply selection on quadratic indices as the selection merit of a particular individual is a quadratic function of its estimated breeding value. This study provides deterministic predictions of genetic gain from selection on quadratic indices for a given set of resources (the number of candidates), heritability, and target rate of inbreeding. The rate of gain was obtained as a function of the accuracy of the Mendelian sampling term at the time of convergence of long-term contributions of selected candidates and the theoretical ideal rate of gain for a given rate of inbreeding after an exact allocation of long-term contributions to Mendelian sampling terms. The expected benefits from quadratic indices over traditional linear indices (i.e. truncation selection), both using BLUP breeding values, were quantified. The results clearly indicate higher gains from quadratic optimisation than from truncation selection. With constant rate of inbreeding and number of candidates, the benefits were generally largest for intermediate heritabilities but evident over the entire range. The advantage of quadratic indices was not highly sensitive to the rate of inbreeding for the constraints considered.

Animals↗
PubMed2006

[The degree of inbreeding in 10 Chinese indigenous pig breeds].

The population inbreeding coefficients of 10 indigenous pig breeds were estimated by microsatellite markers. Results showed that: the inbreeding coefficient of Guizhou miniature pig was the highest (0.1992), and that of Hanzhong black pig the lowest (0.0727) among random mating populations. F test showed no significant difference in inbreeding coefficient among the 8 breeds (P >0.05). The inbreeding coefficient of the Guizhou miniature pig and Bama miniature pig inbreeding lines was 0.5907 and 0.4761, respectively.

Animals↗
PubMed1993

[Inbreeding process and establishment of new inbred lines derived from the Japanese house mouse, Mus musculus molossinus].

Inbreeding of 8 groups in molossinus mouse began in (Miura female x Urawa male) F1 (MU) from the stock captured in the Kanto district of Japan and were accomplished by each primiparous littermates. The animals were kept under a clean conventional condition at 23.5 +/- 2.5 degrees C and 50 +/- 5% in relative humidity. Pellet feed, CRF-1, and tap water were provided ad libitum. The respective number of inbreeding generations of MUA, MUF and MUG now exceeds F21, F20 and F22, respectively. Inbreeding of MUD and MUE have reached to F18 up to now, but the other 3 groups became extinct at F10. Time required for inbreeding from F0 to F20 was 2,280 days for MUA, 2,454 days for MUF and 2,143 days for MUG. Generation time was 114.0 +/- 47.2 days for MUA, 122.7 +/- 54.6 days for MUF and 107.2 +/- 48.5 days for MUG. Though the generation time varied from a minimum of 60 days to a maximum of 258 days from F0 to F10 in the inbreeding process (mean: 150.2 +/- 41.7 days), which were shortened from F10 and the mean was 79.0 +/- 29.1 days. In the breeding of the molossinus mouse, primiparous age was 124.5 +/- 29.7 days from F0 to F9 and 77.8 +/- 9.3 days from F10 to F19. The litter size was 5.1 +/- 1.3 for MUA and 5.0 +/- 1.3 for MUG in offspring, 5.0 +/- 1.2 and 4.9 +/- 1.2 in weanling, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1993

The effect of selection in sublines and crossing on genetic response and inbreeding.

More intense selection in a line gives greater genetic change but also gives a higher rate of inbreeding. Here, continuous selection in one line vs continuous selection in two or more sublines (for the same breeding objective and with the same total number of individuals tested) and crossing the sublines to reduce inbreeding, is studied by stochastic simulation using an infinitesimal model. On crossing, the inbreeding level in the cross, though zero, becomes equivalent to 1/n times that in the sublines, where n is the number of lines in the cross. In general, selecting in sublines and crossing gave less genetic response at the same level of inbreeding than selection in a single line. Use of the best subline generally gave less response than the whole line. It is concluded that selection response at the same level of inbreeding is greatest when all the test facilities and selection are concentrated in a single selection line.

Animals↗
PubMed2006

Inbreeding trends and pedigree analysis of Irish dairy and beef cattle populations.

The objective of this study was to determine the inbreeding levels and to analyze the pedigree of Irish purebred populations of Charolais, Limousin, Hereford, Angus, and Simmental beef cattle, as well as the Holstein-Friesian dairy breed. Pedigree analyses included quantifying the depth of known pedigree, average generation intervals, effective population size, the effective number of founders, ancestors, and founder genomes, as well as identifying the most influential animals within the current population of each breed. The annual rate of increase in inbreeding over the past decade was 0.13% (P < 0.001) in the Hereford, 0.06% (P < 0.001) in the Simmental, and 0.10% (P < 0.001) in the Holstein-Friesian breeds. Inbreeding in the other breeds remained relatively constant over the past decade. Herefords had the greatest mean inbreeding in 2004, at 2.19%, whereas Charolais had the lowest, at 0.54%. Over half of each purebred population in 2004 was inbred to some degree; the population with the greatest proportion of animals inbred was the Hereford breed (85%). All 6 breeds displayed a generation interval of approximately 6 yr in recent years. In the pure-bred females born in 2004, the 3 most influential animals contributed between 11% (Limousin) and 24% (Hereford) of the genes. Effective population size was estimated for the Hereford, Simmental, and Holstein-Friesian only, and was 64, 127, and 75, respectively. The effective number of founders varied from 55 (Simmental) to 357 (Charolais), whereas the effective number of ancestors varied from 35 (Simmental and Hereford) to 82 (Limousin). Thus, despite the majority of animals being inbred, the inbreeding level across breeds is low but rising at a slow rate in the Hereford, Simmental, and Holstein-Friesian.

Animals↗
PubMed2006

Analysis of inbreeding and its relationship with functional longevity in Canadian dairy cattle.

The aim of this study was to assess the level of inbreeding and its relationship to the functional survival of Canadian dairy breeds by using a Weibull proportional hazard model. Data consisted of records from 72,385 cows in 1,505 herds from 2,499 sires for Jerseys, 112,723 cows in 1,482 herds from 2,926 sires for Ayrshires, and 1,977,311 cows in 17,182 herds from 8,261 sires for Holsteins. Longevity was defined as the number of days from first calving to culling, death, or censoring. Inbreeding coefficients (F) were grouped into 7 classes (F = 0, 0 < F < 3.125, 3.125 < or = F < 6.25, 6.25 < or = F <12.5, 12.5 < or = F < 18.25, 18.25 < or = F < 25.0, and F > or = 25.0%). The statistical model included the effects of stage of lactation, season of production, the annual change in herd size, type of milk recording supervision, age at first calving, effects of milk, fat, and protein yields calculated as within herd-year-parity deviations, herd-year-season of calving, inbreeding, and sire. The relative culling rate was calculated for animals in each class after accounting for the above-mentioned effects. A trend toward increased risk of culling among more inbred animals was observed for all breeds. Little difference in survival was observed for cows with 0 < F <12.5%. The relative risk ratios (relative to F = 0) for cows with inbreeding coefficients up to 12.5% were 1.19, 1.16, and 1.14 for Jersey, Ayrshire, and Holstein cows, respectively. Greater effects of inbreeding were seen, however, when F increased beyond 12.5%.

Aging↗
PubMed1983

Inbreeding effects on reproductive traits in the ring-necked pheasant.

Ten inbred lines of Ring-necked pheasants were established in 1978 and mated for four generations using a system of repeated backcrossing of daughters to a common sire. In the event the old sire died, the surviving daughters were mated to a surviving brother or half-brother of the same generation. Only 4 of 10 original inbred lines survived four generations of backcrossing; two involved matings with the original sire and two with brothers or half-brothers of Generations 1 and 3, respectively. Egg production, hatchability, and viability were the three traits most affected by inbreeding depression. For 4 generations of inbreeding, the coefficients of regression for all inbred lines on a 10% increase in inbreeding were -5.89, -.42, -1.73, and -3.04 for egg production, egg weight, fertility, and hatchability, respectively. Inbreeding had less severe effects on reproductive traits in two of the four surviving lines. There is evidence that intense early selection among lines for high performance after one generation of inbreeding F = .250 will enhance the success of establishing highly viable inbred lines of pheasants.

Animals↗
PubMed1975

[Inbreeding in the Samarkand region].

Data on the frequency of inbreeding in some isolated populations of Samarkand region are given. Statistically significant differences were established in the frequency of inbreeding in separate groups and in the general population of the region. Inbreeding marriages were more observed between paralel cousins, occasionally they were made between secon cousins. Strict time dependence of inbreeding frequency was not found, but it was noticed that the level of inbreeding was reduced since 1930 to 1949.

Consanguinity↗
PubMed1975

[Inbreeding in the Samarkand region].

Data on the frequency of inbreeding in some isolated populations of Samarkand region are given. Statistically significant differences were established in the frequency of inbreeding in separate groups and in the general population of the region. Inbreeding marriages were more often observed between paralel cousins, occasionally they were made between second cousins. Strict time dependence of inbreeding frequency was not found, but it was noticed that the level of inbreeding was reduced since 1930 to 1949.

Consanguinity↗
PubMed1997

Effect of excluding sib matings on inbreeding coefficient and effective size of finite diploid populations.

The effects of excluding full-sib matings, half-sib matings, or both under random selection or equal family size selection on the inbreeding coefficient and effective size in finite populations with unequal sex ratio have been studied. Recurrent equations for the inbreeding coefficient and approximate formulas for effective size are derived for different breeding systems. It is shown that avoidance of sib matings results in lower inbreeding coefficients in any generations under random selection. Under equal family size selection, however, excluding sib matings gives rise to lower inbreeding coefficients only in the first few generations and will eventually result in a higher inbreeding in later generations compared with random mating. Exclusion of sib matings increases effective size under random selection while it decreases effective size under equal family size selection. The relative effectiveness on effective size of different sib mating avoidance depends only on sex ratio of the population. The importance of full-sib mating decreases and that of half-sib mating increases with the increment of the value of sex ratio (r). When r = 3, full-sib mating has the same effect on effective size as half-sib mating.

Animals↗
PubMedDate not supplied

Inbreeding and demographic transition in the Orozco Valley (Basque Country, Spain).

Inbreeding in the Orozco Valley (Basque Country, Spain) between the 18th and 20th centuries was investigated on the basis of ecclesiastical dispensations and surname lists. The variations over time are very similar to those observed elsewhere in Europe, with a major increase in the coefficient of inbreeding in the late 19th and early 20th centuries. This is due mainly to an increase in marriages between first cousins. A highly marked decrease in inbreeding is observed during the 20th century. The secular trends described by the coefficient calculated on the basis of dispensations and by that calculated on isonymy are very similar. The nonrandom component of isonymy reveals a selective search for a related spouse during the period of maximum inbreeding. These results are associated with the process of demographic transition which affected European populations as a whole in the 19th century, resulting in a greater availability of kin among potential mates and thus enabling inbreeding to increase to levels far higher than those observed for earlier centuries.

Birth Rate↗
PubMed1999

Kin competition, the cost of inbreeding and the evolution of dispersal

Dispersal is often presented as a mechanism to avoid competition among relatives and inbreeding depression. However, the formal analysis of the effects of both these factors on the evolution of dispersal has only been conducted in few studies with strong restrictive assumptions. In this paper, I first derive the evolutionary stable dispersal rate as a function of three parameters: (1) the cost of dispersal, c, (2) the coefficient of relatedness among randomly chosen offspring, R, and (3) the cost of inbreeding, delta. In a second step, relatedness is used as a dynamical variable for the derivation of the evolutionarily stable dispersal rate. Finally, in a third step, relatedness and the cost of inbreeding are assumed to be dynamical variables. This allows to analyse the more realistic situation where dispersal, relatedness and the cost of inbreeding are coevolving simultaneously. Several subcases are considered depending on the genetic determinism (haploid or diploid), the control of the dispersal strategy (parent or offspring control of dispersal) and the plasticity of dispersal with sexes (with or without sex-specific dispersal rates). This analysis clarifies the role of the cost of inbreeding and kin competition on the evolution of dispersal (in particular on the evolution of sex-biased dispersal rates) and leads to quantitative and testable predictions. Copyright 1999 Academic Press.

Journal Article↗
PubMed1985

AB0 blood group incompatibility and inbreeding effects: evidence for an interaction.

It is known that consanguinity reduces the chances of maternal-foetal incompatibility but it is not known whether inbreeding influences the expression of the effects of such incompatibility. This paper investigates and finds evidence for an interaction between inbreeding and AB0 blood group incompatibility on the expression of neonatal mortality, sibship precocious mortality, neonatal jaundice, asphyxia, and sex ratio, through screening of 3923 consecutive newborns. Inbreeding and incompatibility individually showed variable effects on the above parameters, but their interaction was such that, in the presence of inbreeding, incompatibility reduced the incidence/relative risk of all the above factors. Such a uniform negative interaction was presumed to be due to homozygosity of some pleiotropic genes caused by inbreeding.

ABO Blood-Group System↗
PubMed2004

Measuring inbreeding depression in the wild: the old ways are the best.

Measuring inbreeding depression in normally outbreeding natural populations is an uphill task, because it requires inbreeding coefficients that are calculated from pedigrees. Instead of calculating inbreeding coefficients directly, several studies have reported the use of microsatellite-derived metrics, such as heterozygosity, to infer relative inbreeding among individuals. In two new papers, Slate et al. and Balloux et al. show that these molecular metrics are often only weakly correlated with inbreeding coefficients, and that correlations between heterozygosity and fitness require a new interpretation.

Journal Article↗