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The expected time to the most recent common ancestor (MRCA) of two alleles in a diploid individual is 4N+2 under random mating with a Poisson progeny distribution, but 8N-2 under maximum avoidance of inbreeding, which entails two progeny per mating pair. (N is the number of mating pairs, hence 2N is the number of individuals, hence 4N is the number of alleles.) The interrelationship of inbreeding constraints and offspring distribution is investigated by varying the level of sib mating: prohibiting sib mating increases the time to MRCA by four generations and decreases the variance of the offspring distribution by 2/N. With two progeny per mating pair, the expected time to the MRCA is 8N-2 under both random mating and sib mating prohibited, as well as under maximum avoidance of inbreeding, but this result does not hold for all mating structures with two progeny per mating pair., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Maintaining genetic diversity is a crucial goal of intensive management of threatened species, particularly for those populations that act as sources for translocation or re-introduction programmes. Most captive genetic management is based on pedigrees and a neutral theory of inheritance, an assumption that may be violated by selective forces operating in captivity. Here, we explore the conservation consequences of early viability selection: differential offspring survival that occurs prior to management or research observations, such as embryo deaths in utero. If early viability selection produces genotypic deviations from Mendelian predictions, it may undermine management strategies intended to minimize inbreeding and maintain genetic diversity. We use empirical examples to demonstrate that straightforward approaches, such as comparing litter sizes of inbred vs. noninbred breeding pairs, can be used to test whether early viability selection likely impacts estimates of inbreeding depression. We also show that comparing multilocus genotype data to pedigree predictions can reveal whether early viability selection drives systematic biases in genetic diversity, patterns that would not be detected using pedigree-based statistics alone. More sophisticated analysis combining genomewide molecular data with pedigree information will enable conservation scientists to test whether early viability selection drives deviations from neutrality across wide stretches of the genome, revealing whether this form of selection biases the pedigree-based statistics and inference upon which intensive management is based., (© 2015 John Wiley & Sons Ltd.)

Although evidence of inbreeding depression in wild populations is well established, the impact of genetic purging in the wild remains controversial. The contrasting effects of inbreeding depression, fixation of deleterious alleles by genetic drift, and the purging of deleterious alleles via natural selection mean that predicting fitness outcomes in populations subjected to prolonged bottlenecks is not straightforward. We report results from a long-term pedigree study of arguably the world's most inbred wild species of bird: the Chatham Island black robin Petroica traversi, in which conditions were ideal for purging to occur. Contrary to expectations, black robins showed a strong, negative relationship between inbreeding and juvenile survival, yielding lethal equivalents (2B) of 6.85. We also determined that the negative relationship between inbreeding and survival did not appear to be mediated by levels of ancestral inbreeding and may be attributed in part to unpurged lethal recessives. Although the black robin demographic history provided ideal conditions for genetic purging, our results show no clear evidence of purging in the major life-history trait of juvenile survival. Our results also show no evidence of fixation of deleterious alleles in juvenile survival, but do confirm that continued high levels of contemporary inbreeding in a historically inbred population could lead to additional severe inbreeding depression., (© 2013 The Author(s). Evolution © 2013 The Society for the Study of Evolution.)

Estimates of the influence of inbreeding on the fitness of wild animals can guide genetic conservation in rare species. Conservation genetics is important in Mexican wolves (Canis lupus baileyi) because the current population descended from 7 founders and mean inbreeding is relatively high. As an endangered subspecies, Mexican wolves are actively managed using select conflict avoidance measures and by placing captive‐born foster pups into wild litters. We obtained data on inbreeding coefficients of wolf pups and adults based on a pedigree dating to 1957 and data on reproduction for wild wolf packs during 1998–2022. We estimated trends in inbreeding coefficients and the associations between dam, sire, and pup inbreeding coefficients and pup recruitment to age 9 months, and assessed 3 components of recruitment: probability of producing a litter, number of pups produced, and recruitment conditional on successful reproduction. We generated estimates using generalized linear mixed models and bootstrapped estimates of confidence intervals. Mean inbreeding coefficients were high (0.227, SD = 0.047) in the wild population, but we detected no significant evidence of an increase during 2010–2022. Overall, the net associations of dam, sire, and pup inbreeding coefficients with our primary fitness metric, pup recruitment to age 9 months, did not differ from zero. While high inbreeding coefficients are a concern for the long‐term recovery of the subspecies, the stable level of inbreeding, lack of evidence for inbreeding depression, high pup production (5.1 pups/litter, SD = 1.64), and rapid population growth (384% increase from 2010–2022) indicate that inbreeding has not prevented rapid progress towards recovery goals under current management practices. [ABSTRACT FROM AUTHOR]

Abstract: DNA mixture evidence pertains to cases where several individuals may have contributed to a biological stain. Statistical methods and software for such problems are available and a large number of cases can be handled adequately. However, one class of mixture problems remains untreated in full generality in the literature, namely when the contributors may be related. Disregarding a plausible close relative of the perpetrator as an alternative contributor (identical twin is the most extreme case) may lead to overestimating the evidence against a suspect. Existing methods only accommodate pairwise relationships such as the case where the suspect and the victim are siblings, for example. In this paper we consider relationships in full generality, conveniently represented by pedigrees. In particular, these pedigrees may involve inbreeding, for instance when the parents of an individual of interest are first cousins. Furthermore our framework handles situations where the opposing parties in a court case (prosecution and defence) propose different family relationships. Consequently, our approach combines classical mixture and kinship problems. The basic idea of this paper is to formulate the problem in a way that allows for the exploitation of currently available methods and software designed originally for linkage applications. We have developed a freely available R package, euroMix based on another package, paramlink, and we illustrate the ideas and methods on real and simulated data. [Copyright &y& Elsevier]

The number of individuals translocated and released as part of a reintroduction is often small, as is the final established population, because the reintroduction site is typically small. Small founder and small resulting populations can result in population bottlenecks, which are associated with increased rates of inbreeding and loss of genetic diversity, both of which can affect the long-term viability of reintroduced populations. I used information derived from pedigrees of four monogamous bird species reintroduced onto two different islands (220 and 259 ha) in New Zealand to compare the pattern of inbreeding and loss of genetic diversity among the reintroduced populations. Although reintroduced populations founded with few individuals had higher levels of inbreeding, as predicted, other factors, including biased sex ratio and skewed breeding success, contributed to high levels of inbreeding and loss of genetic diversity. Of the 10-58 individuals released, 4-25 genetic founders contributed at least one living descendent and yielded approximately 3-11 founder-genome equivalents (number of genetic founders assuming an equal contribution of offspring and no random loss of alleles across generations) after seven breeding seasons. This range is much lower than the 20 founder-genome equivalents recommended for captive-bred populations. Although the level of inbreeding in one reintroduced population initially reached three times that of a closely related species, the long-term estimated rate of inbreeding of this one population was approximately one-third that of the other species due to differences in carrying capacities of the respective reintroduction sites. The increasing number of reintroductions to suitable areas that are smaller than those I examined here suggests that it might be useful to develop long-term strategies and guidelines for reintroduction programs, which would minimize inbreeding and maintain genetic diversity. [ABSTRACT FROM AUTHOR]

Charles Darwin, who was married to his first cousin, Emma Wedgwood, was one of the first experimentalists to demonstrate the adverse effects of inbreeding and to question the consequences of consanguineous mating. He documented the phenomenon of inbreeding depression for numerous plant species, and this caused him to worry about the health of his own children, who were often ill. To determine whether Darwin's fears were justified, we constructed a pedigree of the Darwin/Wedgwood dynasty from the large quantity of genealogical information published on these families. The inbreeding coefficients OF) computed from the pedigree show that Darwin's children were subject to a moderate level of inbreeding (F = 0.0630), and the progeny of related families had still higher inbreeding values (e.g., F = 0.1255 for the progeny of Henry Wedgwood, Emma Wedgwood's brother). The analysis of a sample of 25 Darwin/Wedgwood families belonging to four consecutive generations shows a statistically significant positive association between child mortality (death at or before the age of 10 years) and inbreeding coefficient detected by means of nonparametric tests (τ = 0.309, P = 0.040). Our findings suggest that the high childhood mortality experienced by the Darwin progeny (3 of his 10 children died at age 10 or younger) might be a result of increased homozygosity of deleterious recessive alleles produced by the consanguineous marriages within the Darwin/Wedgwood dynasty. [ABSTRACT FROM AUTHOR]

Offspring born to related parents may show reduced fitness due to inbreeding depression. Although evidence of inbreeding depression has accumulated for a variety of taxa during the past two decades, such analyses remain rare for primate species, probably because of their long generation time. However, inbreeding can have important fitness costs and is likely to shape life-history traits in all living species. As a consequence, selection should have favored inbreeding avoidance via sex-biased dispersal, extra-group paternity, or kin discrimination. In this paper, we review empirical studies on the effects of inbreeding on fitness traits or fitness correlates in primate species. In addition, we report the methods that have been used to detect inbreeding in primate populations, and their development with the improvement of laboratory techniques. We focus particularly on the advantages and disadvantages using microsatellite loci to detect inbreeding. Although the genetic data that are typically available (partial pedigrees, use of microsatellite heterozygosity as an estimate of genomewide inbreeding) tend to impose constraints on analyses, we encourage primatologists to explore the potential effects of inbreeding if they have access to even partial pedigrees or genetic information. Such studies are important because of both the value of basic research in inbreeding depression in the wild and the conservation issues associated with inbreeding, particularly in threatened species, which include more than half of the currently living primate species. Am. J. Primatol. 69:1370–1386, 2007. © 2007 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

An ongoing problem in the genetics clinic is the calculation of inbreeding coefficients and recurrence risks for complex pedigrees, particularly when multiple “loops” are present. Although the Human Genome Project promises information about more of our genes in the foreseeable future, the actual assignment of disease status to specific loci will continue at a slower pace, so that accurate risk calculations are needed. In the past few months several families with consanguinity were referred to us to confirm the calculations performed by the genetic counselor, and we became aware of some confusion in the field. We present here both (a) a clarification of definitions and concepts and (b) a review of how to perform the calculations, for several quantities (coefficient of relationship, coefficient of inbreeding, coefficient of kinship, and recurrence risk), in complex pedigrees. We discuss the availability of computer algorithms to assist in these calculations, and we encourage counselors to call on a reliable computer program for any but the simplest cases. At the same time, we reiterate our belief that computer algorithms do not relieve the counselor of the responsibility of knowing what to calculate and when. [ABSTRACT FROM AUTHOR]