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PubMed2005

Effects of inbreeding on ovarian responses and embryo production from superovulated Mantiqueira breed cows.

The objective of the present experiment was to evaluate the effects of different levels of inbreeding on ovarian response and embryo production from superovulated cows. One hundred and thirteen Mantiqueira cows (a medium-size, Bos taurus native dairy cattle breed), with inbreeding coefficients ranging from 0 to 30%, were allocated into five classes of inbreeding and subjected to superovulation treatment. At induced estrus, cows were mated with Mantiqueira bulls (with minimal inbreeding). Six to eight days after mating, the cows were slaughtered, ovarian structures counted and embryos recovered by flushing the uterine horns and oviducts. Sire, season, age, weight, parity and age at first calving of donors did not significantly affect ovarian response or embryo production and quality. There were no effects of inbreeding class on number of total corpora lutea (CL) or number of CL present in the right ovary. However, the number of CL in the left ovary was reduced (P<0.05) in cows with Class 5 (>9%) of inbreeding. The number of transferable, but not the number of non-transferable embryos or the total number of embryos from cows with Class 5 of inbreeding, was lower (P<0.05) than those of cows from Classes 0 to 4 (<9%) of inbreeding. There was a quadratic decrease in the number of transferable embryos as inbreeding coefficient increased (Y=11.077+0.34X-0.0529X(2); R(2)=0.91, P<0.01), but no significant linear or quadratic effect of inbreeding on total number of embryos or number of non-transferable embryos. In conclusion, an inbreeding coefficient>9% reduced the quality of bovine embryos at the initial stage of development.

Aging↗
PubMed2001

Temporal changes in allele frequency, genetic variation and inbreeding depression in small populations of the guppy, Poecilia reticulata.

We established three closed lines of N = 10 for the guppy Poecilia reticulata, to evaluate the relationships among temporal changes in allele frequency, genetic variation and inbreeding depression for a fitness-related trait in small populations. Genetic variation at the allozyme loci, expressed by the proportion of polymorphic loci, number of alleles per locus and heterozygosity, decreased somewhat in two closed lines but it increased in one closed line over six generations. Effective population size (Ne) at each generation was estimated from the standardized variance in the allele frequencies. The average Ne was 24.4, 10.3 and 10.0 in the three closed lines. The inbreeding coefficient calculated from the Ne increased to 0.186, 0.321 and 0.414, respectively. As an index of the amount of inbreeding depression, changes in salinity tolerance were examined, because this trait is strongly sensitive to inbreeding depression and decreases linearly with an increase in inbreeding coefficient. The mean value of the salinity tolerance significantly decreased to 82.5%, 71.7% and 67.6% in the three closed lines during the six generations, suggesting inbreeding depression for salinity tolerance. Although a significant correlation was not observed between the amount of inbreeding depression and the genetic variation, the amount of inbreeding depression correlated with the inbreeding coefficient calculated from Ne. The regression line indicated an 8.4% decrease in the mean per 10% increase in the inbreeding coefficient and was similar to that obtained directly from full-sib matings. These results indicate that the temporal changes in the allele frequencies can provide an estimation of the amount of inbreeding depression during successive generations in small populations.

Adaptation, Physiological↗
PubMed2002

Estimating the prevalence of inbreeding from incomplete pedigrees.

A previous review of inbreeding in natural populations suggested that close inbreeding (inbreeding coefficient f = 0.25) is generally rare in wild birds and mammals. However, the review did not assess rates of moderate inbreeding (f = 0.125), which may make a rather larger contribution to overall inbreeding in a population. Furthermore, previous studies may have underestimated the prevalence of inbreeding in wild populations with incomplete pedigrees. By categorizing inbreeding events by the relationship of the parental pair, we suggest a simple method for estimating rates of close and moderate inbreeding from incomplete pedigree data. We applied this method to three wild populations of ruminants: red deer on Rum, Scotland, Soay sheep on Hirta, Scotland and reintroduced Arabian oryx on the Jiddat-al-Harasis, Oman. Although paternal half-sib pairs were the most common category of inbreeding in all three populations, there was considerable variation among populations in the frequencies of the various categories of inbreeding. This variation may be largely explained by differences in population size and dynamics, in maternal and paternal sibship size and in the overlap of reproductive lifespan of consecutive generations. Close and moderate inbreeding appear to be a routine part of breeding behaviour in these ruminant populations.

Animals↗
PubMed2004

Experimental dissection of inbreeding and its adaptive significance in a flowering plant, Aquilegia canadensis (Ranunculaceae).

Inbreeding is a major component of the mating system in populations of many plants and animals, particularly hermaphroditic species. In flowering plants, inbreeding can occur through self-pollination within flowers (autogamy), self-pollination between flowers on the same plant (geitonogamy), or cross-pollination between closely related individuals (biparental inbreeding). We performed a floral emasculation experiment in 10 populations of Aquilegia canadensis (Ranunculaceae) and used allozyme markers to estimate the relative contribution of each mode of inbreeding to the mating system. We also examined how these modes of inbreeding were influenced by aspects of population structure and floral morphology and display predicted to affect the mating system. All populations engaged in substantial inbreeding. On average, only 25% of seed was produced by outcrossing (range among populations = 9-37%), which correlated positively with both population size (r = +0.61) and density (r = +0.64). Inbreeding occurred through autogamy and biparental inbreeding, and the relative contribution of each was highly variable among populations. Estimates of geitonogamy were not significantly greater than zero in any population. We detected substantial biparental inbreeding (mean = 14% of seeds, range = 4-24%) by estimating apparent selfing in emasculated plants with no opportunity for true selfing. This mode of inbreeding correlated negatively with population size (r = -0.87) and positively with canopy cover (r = +0.90), suggesting that population characteristics that increase outcross pollen transfer reduce biparental inbreeding. Autogamy was the largest component of the mating system in all populations (mean = 58%, range = 37-84%) and, as expected, was lowest in populations with the most herkogamous flowers (r = -0.59). Although autogamy provides reproductive assurance in natural populations of A. canadensis, it discounts ovules from making superior outcrossed seed. Hence, high autogamy in these populations seems disadvantageous, and therefore it is difficult to explain the extensive variation in herkogamy observed both among and especially within populations.

Adaptation, Biological↗
PubMed2006

Interactive effects of environmental stress and inbreeding on reproductive traits in a wild bird population.

1. Conservation biologists are concerned about the interactive effects of environmental stress and inbreeding because such interactions could affect the dynamics and extinction risk of small and isolated populations, but few studies have tested for these interactions in nature. 2. We used data from the long-term population study of song sparrows Melospiza melodia on Mandarte Island to examine the joint effects of inbreeding and environmental stress on four fitness traits that are known to be affected by the inbreeding level of adult birds: hatching success, laying date, male mating success and fledgling survival. 3. We found that inbreeding depression interacted with environmental stress to reduce hatching success in the nests of inbred females during periods of rain. 4. For laying date, we found equivocal support for an interaction between parental inbreeding and environmental stress. In this case, however, inbred females experienced less inbreeding depression in more stressful, cooler years. 5. For two other traits, we found no evidence that the strength of inbreeding depression varied with environmental stress. First, mated males fathered fewer nests per season if inbred or if the ratio of males to females in the population was high, but inbreeding depression did not depend on sex ratio. Second, fledglings survived poorly during rainy periods and if their father was inbred, but the effects of paternal inbreeding and rain did not interact. 6. Thus, even for a single species, interactions between the inbreeding level and environmental stress may not occur in all traits affected by inbreeding depression, and interactions that do occur will not always act synergistically to further decrease fitness.

Animals↗
PubMed2000

Effects of inbreeding on production and survival in Holsteins.

Responses of registered Holstein cows to various levels of inbreeding were examined with pedigree data supplied by the Holstein Association USA and test-day production data from 1970 through 1998 obtained from the Animal Breeding Center at Cornell University. Rate of increase in level of inbreeding has been accelerating over time, making it more difficult for producers to make matings that avoid the potentially deleterious effects of inbreeding. Milk production losses per lactation caused by inbreeding were generally 35 kg per percentage inbreeding level >0.01 but increased to 55 kg per percentage inbreeding level from 0.07 to 0.10. Somatic cell score was not affected by level of inbreeding. Inbreeding had the greatest effect on production at ages <22 mo and early in lactation. Early onset of the deleterious effects of inbreeding resulted in larger net present value losses than when effects of inbreeding occurred later. Losses were likely enhanced due to the need to freshen animals as early as possible to maximize net present value returns. Survival decreased as level of inbreeding increased and was likely to have a greater negative impact on the financial health of the dairy enterprise than production losses.

Age Factors↗
PubMed2005

Multigenerational effects of inbreeding in Cucurbita pepo ssp. texana (Cucurbitaceae).

The shape of the fitness function relating the decline in fitness with coefficient of inbreeding (f) can provide evidence concerning the genetic basis of inbreeding depression, but few studies have examined inbreeding depression across a range of f using noncultivated species. Futhermore, studies have rarely examined the effects of inbreeding depression in the maternal parent on offspring fitness. To estimate the shape of the fitness function, we examined the relationship between f and fitness across a range off from 0.000 to 0.875 for components of both male and female fitness in Cucurbita pepo ssp. texana. Each measure of female fitness declined with f, including pistillate flower number, fruit number, seed number per fruit, seed mass per fruit, and percentage seed germination. Several aspects of male fitness also declined with f, including staminate flower number, pollen number per flower, and the number of days of flowering, although cumulative inbreeding depression was less severe for male (0.34) than for female function (0.39). Fitness tended to decline linearly with f between f = 0.00 and f = 0.75 for most traits and across cumulative lifetime fitness (mean = 0.66), suggesting that individual genes causing inbreeding depression are additive and the result of many alleles of small effect. However, most traits also showed a small reduction in inbreeding depression between f = 0.75 and f = 0.875, and evidence of purging or diminishing epistasis was found for in vitro pollen-tube growth rate. To examine inbreeding depression as a maternal effect, we performed outcross pollinations on f = 0.0 and f = 0.5 mothers and found that depression due to maternal inbreeding was 0.07, compared to 0.10 for offspring produced through one generation of selfing. In at least some families, maternal inbreeding reduced fruit number, seed number and mass, staminate flower number, pollen diameter, and pollen-tube growth rate. Collectively these results suggest that, while the fitness function appears to be largely linear for most traits, maternal effects may compound the effects of inbreeding depression in multigenerational studies, though this may be partially offset by purging or diminishing epistasis.

Analysis of Variance↗
PubMed1999

Effect of inbreeding avoidance on Hardy-Weinberg expectations: examples of neutral and selected loci.

Although all human populations avoid close inbreeding, the effect of inbreeding avoidance on genotype proportions has not been formally considered. This paper examines the expected proportions of genotype frequencies after adjusting the Hardy-Weinberg model for close inbreeding avoidance in an inbred population. This corrected model was used to evaluate genotype distributions for HLA haplotypes and haplotypes created from three microsatellite loci on human chromosome 13 in a sample of 315 married Hutterites. In this sample, there were five individuals who were homozygous for an HLA haplotype and 15 individuals who were homozygous for a chromosome 13 haplotype. The expected numbers of homozygotes were 21 for HLA and 26 for chromosome 13 haplotypes using a model adjusted for overall inbreeding (P = 0.00031 for HLA and P = 0.019 for chromosome 13) and 18 for HLA and 22 chromosome 13 haplotypes using a model adjusted for both overall inbreeding and close inbreeding avoidance (P = 0. 0016 for HLA and P = 0.099 for chromosome 13). The model that takes into account both overall inbreeding and inbreeding avoidance provided a better fit to the observed genotype distributions for chromosome 13 haplotypes (P = 0.099), suggesting that nonrandom aspects of Hutterite mating structure, other than inbreeding and inbreeding avoidance, have small effects on genotype distributions in the population. The fact that significant deficiencies of HLA homozygotes persist after taking into account inbreeding avoidance further suggests that factors related to the HLA haplotype per se influence the genotype proportions at HLA loci in the Hutterites.

Adult↗
PubMed1999

Inbreeding depression and selfing rates in a self-compatible, hermaphroditic species, Schiedea membranacea (Caryophyllaceae).

Inbreeding depression and selfing rates were investigated in Schiedea membranacea (Caryophyllaceae), a hermaphroditic species endemic to the Hawaiian Islands. Most theoretical models predict high inbreeding depression in outcrossing hermaphroditic species and low inbreeding depression in inbreeding species. Although high outcrossing rates and high levels of inbreeding depression are characteristic of many species of Schiedea, self- fertilization is common among relatives of hermaphroditic S. membranacea, and high selfing rates and low levels of inbreeding depression were predicted in this species. Sixteen individuals grown in the greenhouse were used to produce selfed and outcrossed progeny. Inbreeding depression, which was evident throughout the stages measured (percentage viable seeds per capsule, mean seed mass, percentage seed germination, percentage seedling survival, and biomass after 8 mo), averaged 0.70. Inbreeding depression among maternal families varied significantly for all measured traits and ranged from -0.12 to 0.97. Using isozyme analysis, the multilocus selfing rate varied from 0.13 to 0.38 over 4 yr. Contrary to the initial prediction of high selfing and low inbreeding depression based on phylogenetic relationships within Schiedea, low selfing rates and high levels of inbreeding depression were found in S. membranacea. These results indicate that outcrossing is stable in this species and maintained by high levels of inbreeding depression.

Journal Article↗
PubMed2000

[Genogeographic analysis of a subdivided population. II. Geography of random inbreeding (from frequency of surnames in Adygs)].

An important characteristic of the genetic structure of populations, random inbreeding (interpopulation variation), was evaluated on the basis of quasi-genetic markers (surnames). The following methodological issues are considered: estimation of random inbreeding using the coefficient of isonymy fr in a subdivided population; a comparison of inbreeding levels calculated on the basis of surname frequencies using fr and Wright's FST; a comparison of inbreeding estimates obtained on the basis of surnames and genetic markers; inbreeding variation in populations of the same hierarchical rank; and planning of genetic studies of a subdivided population. The population of Adygs (an indigenous ethnic group of Northern Caucasus) was examined as a model subdivided population. The population system of Adygs is hierarchical. Parameters of random inbreeding were examined at each level of the system "ethnic group==>tribe==>geographic group of auls==>aul." Frequencies of surnames were collected subtotally. Data on frequencies of 1340 surnames in 61 auls representing all Adyg tribes were analyzed. In total, 60,000 people were examined. The inbreeding estimates obtained on the basis of Wright's FST and the coefficient of isonymy fr virtually coincided: for Adygs in general, FST x 10(2) = 2.13 and fr x 10(2) = 2.09. At the same time, the inbreeding level exhibited marked differences among tribes: in Shapsugs, these differences were an order of magnitude higher than in Kabardins (fr x 10(2) = 2.53 and 0.25, respectively). The inbreeding estimates for auls differed by two orders of magnitudes: fr x 10(2) = 0.07 and fr x 10(2) = 7.88. An analysis of ten auls yielded fully coinciding inbreeding estimates based on quasi-genetic (fr x 10(2) = 0.60) and classical (FST x 10(2) = 0.69) gene markers. Computer maps of surname distributions in Adygs (1340 maps) were constructed for the first time ever. Based on these maps, the map of random inbreeding in the Adyg population was obtained.

Consanguinity↗
PubMed1994

Inbreeding: one word, several meanings, much confusion.

Because conservation biologists must frequently deal with small populations, inbreeding (a frequent consequence of small population size) has played a central role in many genetic management programs. However, the word "inbreeding" has several, often contradictory meanings, and a failure to distinguish among these meanings has caused much misunderstanding on the role of inbreeding in genetic management. Three different biological meanings of inbreeding are discussed in this paper: (1) inbreeding as a measure of shared ancestry in the paternal and maternal lineages of an individual; (2) inbreeding as a measure of genetic drift in a finite population, and (3) inbreeding as a measure of system of mating in a reproducing population. The distinction and use of these different measures of inbreeding are discussed and illustrated with a worked example, the North American captive population of Speke's gazelle (Gazella spekei). It is shown that these different meanings of the word inbreeding must be kept separated, otherwise erroneous management recommendations and evaluations can occur. On the positive side, the different measures of inbreeding when used jointly can be a powerful management tool precisely because they measure different biological phenomena.

Animals↗
PubMed2004

A comparison of inbreeding rates in India, Japan, Europe and China.

This is a report on an application of a new method for estimating inbreeding rates in large, semi-isolated populations over time. This study is intended to further show the versatility of the method. In a previous study, the method was shown to be useful in analysing the effect of details in a single population curve on inbreeding. In this study, the method is applied to the population curves of India, Japan, Europe and China over the past two millennia, to allow inter-comparisons of the inbreeding within those populations. Anthropologists traditionally concentrate on small isolates within a country for the estimation of inbreeding. Those isolates, however, might not be representative of the country as a whole. The method used in this study attempts to estimate inbreeding over large regions over an extended period of time. The method models the genealogical 'paradox' and yields estimates of the average inbreeding in terms of Pearl's coefficient Z, as a function of time. It is first assumed that the whole population of each country is the adult (breeding) population, corresponding to minimum inbreeding. It is found that the more complex the population curve examined, the greater the precision of the Z curves obtained. The effect of incorporating a single known value of inbreeding into the analyses is also investigated. This procedure produces a more realistic situation where the adult (breeding) population is considerably less than the entire population. It is shown, that if it is assumed that the whole population of the country is the adult (breeding) population, then a present day person from one of the four regions/countries studied is descended from between 72% and 97% of the early medieval population of the particular country. On the other hand, if a known value of inbreeding for Britain is incorporated into the analysis, these values become of the order of 1% for the older-settled regions/countries, and about 16% for Japan. However, that value for Japan is reduced to about 1% when a known value of inbreeding for this country is used. Although some uncertainty in these results remains, the versatility of the method demonstrated here will provide more accurate results, as better input-data become available.

Adult↗
PubMed2005

Possible negative effects of inbreeding on semen quality in Shetland pony stallions.

Inbreeding is widely believed to negatively affect reproductive performance. Indeed, in some species, high levels of inbreeding are thought to be the major cause of poor semen quality. It is, however, not clear whether inbreeding affects fertility in horses. In this study, the relationship between inbreeding and semen quality was examined in 285 immature Shetland pony stallions submitted for breeding soundness examination in March-April of the years 1992-1997. The majority of stallions examined were 3 years old (85%) and their coefficients of inbreeding ranged from 0 to 25% (mean+/-S.D.: 3+/-4.6%). For the purpose of analysis, stallions were divided into six inbreeding classes (0-1, 1-2, 2-5, 5-8, 8-12 and >12%) containing 132, 40, 42, 27, 25 and 19 animals, respectively. The degree of inbreeding significantly affected many aspects of sperm production and quality, based on a standard examination of two ejaculates collected at a 1.5-3h interval. In particular, coefficients of inbreeding above 2% were associated with lower percentages of motile (p<0.01) and morphologically normal sperm (p<0.001). When the data set was used to estimate heritability of semen characteristics, the high values calculated for sperm progressive motility (0.46) and concentration (0.24) suggested that these traits could be improved by phenotypic selection. These findings support the hypothesis that inbreeding has a detrimental effect on semen quality in Shetland ponies, although examination of multiple ejaculates after repeated semen collection to bring the animals to daily sperm output is needed to confirm this conclusion. Nevertheless, the results support previous suggestions that inbreeding is an important cause of reduced semen quality.

Animals↗
PubMed1991

"Runaway" social evolution: reinforcing selection for inbreeding and altruism.

Kin selection theory predicts that altruistic behaviors, those that decrease the fitness of the individual performing the behavior but increase the fitness of the recipient, can increase in frequency if the individuals interacting are closely related. Several studies have shown that inbreeding therefore generally increases the effectiveness of kin selection when fitnesses are linear, additive functions of the number of altruists in the family, although with extreme forms of altruism, inbreeding can actually retard the evolution of altruism. These models assume that a constant proportion of the population mates at random and a constant proportion practices some form of inbreeding. In order to investigate the effect of inbreeding on the evolution of altruistic behavior when the mating structure is allowed to evolve, we examined a two-locus model by computer simulation of a diploid case and illustrated the important qualitative features by mathematical analysis of a haploid case. One locus determines an individual's propensity to perform altruistic social behavior and the second locus determines the probability that an individual will mate within its sibship. We assumed positive selection for altruism and no direct selection at the inbreeding locus. We observed that the altruistic allele and the inbreeding allele become positively associated, even when the initial conditions of the model assume independence between these loci. This linkage disequilibrium becomes established, because the altruistic allele increases more rapidly in the inbreeding segment of the population. This association subsequently results in indirect selection on the inbreeding locus. However, the dynamics of this model go beyond a simple "hitch-hiking" effect, because high levels of altruism lead to increased inbreeding, and high degrees of inbreeding accelerate the rate of change of the altruistic allele in the entire population. Thus, the dynamics of this model are similar to those of "runaway" sexual selection, with gene frequency change at the two loci interactively causing rapid evolutionary change.

Alleles↗
PubMed1998

Inbreeding and reproduction in mice divergently selected for response to a dietary toxin.

This study was conducted to determine whether inbreeding coefficients of selected parents or of progeny differed between lines of mice selected for increased or decreased responsiveness to a nutritional toxicosis. A second objective was to determine whether the influence of inbreeding of parents and/or progeny on reproductive traits differed between those lines. Mice were selected divergently for 8 generations for the effect on post-weaning growth of endophyte-infected fescue seed in their diet. Forty pairs (or in Generation 7, 20 pairs) were selected and mated per generation in each line. Inbreeding increased 0.5 to 0.6% per generation in both lines, a rate close to that predicted from genetic theory. Inbreeding coefficients of selected parents were not higher in the susceptible than in the resistant line. A difference would have been expected if the inbreeding coefficient had been correlated with susceptibility to toxicosis. The magnitudes of inbreeding depression for reproductive traits did not differ significantly between lines. The average inbreeding coefficient of the potential litter tended to be higher in nonfertile than fertile matings (P = 0.10), but inbreeding coefficients of sires and dams did not differ between successful and unsuccessful matings. Inbred litters tended to be born earlier than noninbred litters (P = 0.10). Inbred dams produced smaller litters than noninbred dams (main effect P < 0.05) but only when the litter also was inbred (interaction P < 0.01). Sex ratio was not influenced by inbreeding of sire, dam or litter, but there was a higher proportion of male progeny in the susceptible than in the resistant line (P = 0.01). To avoid reduced reproductive fitness, laboratory animal populations should be managed to minimize inbreeding of progeny and dam.

Animals↗
PubMed1999

The contribution of male-sterility mutations to inbreeding depression in Mimulus guttatus.

The magnitude of inbreeding depression can influence many aspects of a population's ecology and evolution, including the nature of selection acting on the mating system and the chances that the population will go extinct during periods of small population size. If inbreeding depression is caused primarily by recessive mutations of large effect on fitness, such as lethals or steriles, then it is expected to be purged rapidly by selection with moderate amounts of inbreeding. In contrast, inbreeding depression primarily caused by many genes with mild effects on fitness will not be rapidly purged with inbreeding, so it should be a more resilient barrier to the evolution of self-fertilization and a more significant threat to the survival of endangered species. Here I show that recessive male-sterility alleles at individual loci are common in a primarily outcrossing population of the plant Mimulus guttatus. Despite the high frequency of these major mutations, most of the inbreeding depression for male fertility and cumulative measures of lifetime fitness results from more mildly deleterious alleles. Male-sterility alleles contribute to 31% of the inbreeding depression for the fraction of viable pollen grains, and to 26% of the inbreeding depression for total fitness. These results suggest that most of the inbreeding depression for male fertility in this population would not be purged, in the short term, with moderate inbreeding.

Alleles↗
PubMed2003

The effects of parasitism and inbreeding on the competitive ability in Daphnia magna: evidence for synergistic epistasis.

Synergistic epistasis for fitness is often assumed in models of how selection acts on the frequency and distribution of deleterious mutations. Evidence for synergistic epistasis would exist if the logarithm of fitness declines more quickly with number of deleterious mutations, than predicted by a linear decline. This can be studied indirectly by quantifying the effect of different levels of inbreeding on fitness. Here, six sets (different genetic backgrounds) of three increasingly inbred Daphnia magna clones were used to assess their relative fitness according to changes in frequency in a competition experiment against a tester clone. A novelty of the mating procedure was that the inbreeding coefficients (F) of the three clones belonging to each set increased in steps of 0.25 independent of the (unknown) inbreeding coefficient of the common ancestor. The equal increase of the inbreeding coefficients is important, because deviations influence the quantification of inbreeding depression, its variance and the detection of epistasis. In a simple mathematical model we show that when working with a partially inbred population inbreeding depression is underestimated, the variance of fitness is increased, and the detection of epistasis more difficult. Further, to examine whether an interaction between inbreeding and parasitism exists, each inbred clone was tested with and without a microsporidium infection (Octosporea bayeri). We found a nonlinear decrease of the logarithm of fitness across the three levels of inbreeding, indicating synergistic epistasis. The interaction term between parasitism and inbreeding was not significant. Our results suggest that deleterious mutations may be purged effectively once the level of inbreeding is high, but that parasitism seems not to influence this effect.

Animals↗
PubMed2003

Inbreeding avoidance through kin recognition: choosy females boost male dispersal.

Inbreeding avoidance is predicted to induce sex biases in dispersal. But which sex should disperse? In polygynous species, females pay higher costs to inbreeding and thus might be expected to disperse more, but empirical evidence consistently reveals male biases. Here, we show that theoretical expectations change drastically if females are allowed to avoid inbreeding via kin recognition. At high inbreeding loads, females should prefer immigrants over residents, thereby boosting male dispersal. At lower inbreeding loads, by contrast, inclusive fitness benefits should induce females to prefer relatives, thereby promoting male philopatry. This result points to disruptive effects of sexual selection. The inbreeding load that females are ready to accept is surprisingly high. In absence of search costs, females should prefer related partners as long as delta<r/(1+r) where r is relatedness and delta is the fecundity loss relative to an outbred mating. This amounts to fitness losses up to one-fifth for a half-sib mating and one-third for a full-sib mating, which lie in the upper range of inbreeding depression values currently reported in natural populations. The observation of active inbreeding avoidance in a polygynous species thus suggests that inbreeding depression exceeds this threshold in the species under scrutiny or that inbred matings at least partly forfeit other mating opportunities for males. Our model also shows that female choosiness should decline rapidly with search costs, stemming from, for example, reproductive delays. Species under strong time constraints on reproduction should thus be tolerant of inbreeding.

Animals↗