Inbreeding depression

Last updated
Inbreeding depression in Delphinium nelsonii. A. Overall fitness of progeny cohorts and the B. progeny lifespan were all lower when progeny were the result of crosses with pollen taken close to a receptor plant. Inbreeding depression in Delphinium nelsonii.png
Inbreeding depression in Delphinium nelsonii . A. Overall fitness of progeny cohorts and the B. progeny lifespan were all lower when progeny were the result of crosses with pollen taken close to a receptor plant.

Inbreeding depression is the reduced biological fitness that has the potential to result from inbreeding (the breeding of related individuals). The loss of genetic diversity that is seen due to inbreeding, results from small population size. [2] Biological fitness refers to an organism's ability to survive and perpetuate its genetic material. Inbreeding depression is often the result of a population bottleneck. In general, the higher the genetic variation or gene pool within a breeding population, the less likely it is to suffer from inbreeding depression, though inbreeding and outbreeding depression can simultaneously occur.

Contents

Inbreeding depression seems to be present in most groups of organisms, but varies across mating systems. Hermaphroditic species often exhibit lower degrees of inbreeding depression than outcrossing species, as repeated generations of selfing is thought to purge deleterious alleles from populations. For example, the outcrossing nematode (roundworm) Caenorhabditis remanei has been demonstrated to suffer severely from inbreeding depression, unlike its hermaphroditic relative C. elegans , which experiences outbreeding depression. [3]

Mechanisms

Example of inbreeding depression Shetland pony inbred.jpg
Example of inbreeding depression

Inbreeding (i.e., breeding between closely related individuals) results in more recessive traits manifesting themselves, as the genomes of pair-mates are more similar. Recessive traits can only occur in an offspring if present in both parents' genomes. The more genetically similar the parents are, the more often recessive traits appear in their offspring. This normally has a positive effect, as most genes are undergoing purifying selection (the homozygous state is favored). However, for very closely related individuals, there is an increased likelihood of homozygous deleterious genes in the offspring which can result in unfit individuals. [4] For the alleles that confer an advantage in the heterozygous and/or homozygous-dominant state, the fitness of the homozygous-recessive state may even be zero (meaning sterile or unviable offspring).

An example of inbreeding depression is shown in the image. In this case, a is the recessive allele which has negative effects. In order for the a phenotype to become active, the gene must end up as homozygous aa because in the geneotype Aa, the A takes dominance over the a and the a does not have any effect. Some recessive genes result in detrimental phenotypes by causing the organism to be less fit to its natural environment.

Another mechanism responsible for inbreeding depression is the fitness advantage of heterozygosity, which is known as overdominance. This can lead to reduced fitness of a population with many homozygous genotypes, even if they are not deleterious or recessive. Here, even the dominant alleles result in reduced fitness if present homozygously (see also hybrid vigour).

Overdominance is rare in nature. [4] For practical applications, e.g. in livestock breeding, the former is thought to be more significant – it may yield completely unviable offspring (meaning outright failure of a pedigree), while the latter can only result in relatively reduced fitness.

Natural selection

Natural selection cannot effectively remove all deleterious recessive genes from a population for several reasons. First, deleterious genes arise constantly through de novo mutation within a population. Second, most offspring will have some deleterious traits, so few will be more fit for survival than the others. Different deleterious traits are extremely unlikely to equally affect reproduction – an especially disadvantageous recessive trait expressed in a homozygous recessive individual is likely to eliminate itself, naturally limiting the expression of its phenotype. Third, recessive deleterious alleles will be "masked" by heterozygosity, and so in a dominant-recessive trait, heterozygotes will not be selected against.

When recessive deleterious alleles occur in the heterozygous state, where their potentially deleterious expression is masked by the corresponding wild-type allele, this masking phenomenon is referred to as complementation (see complementation (genetics)).

In general, sexual reproduction in eukaryotes has two fundamental aspects: genetic recombination during meiosis, and outcrossing. It has been proposed that these two aspects have two natural selective advantages respectively. A proposed adaptive advantage of meiosis is that it facilitates recombinational repair of DNA damages that are otherwise difficult to repair (see DNA repair as the adaptive advantage of meiosis). A proposed adaptive advantage of outcrossing is complementation, which is the masking of deleterious recessive alleles [5] [6] (see hybrid vigor or heterosis). The selective advantage of complementation may largely account for the avoidance of inbreeding (see kin recognition).

However animals often do not avoid inbreeding. [7] Among animals, inbreeding avoidance is highly variable. [8] Inbreeding avoidance through mate selection appears to evolve only when there is both a risk of inbreeding depression and there also are frequent encounters between sexual partners that are related to each other. [8]

Management

Hybridization as a conservation effort is appropriate if the population has lost "substantial genetic variation through genetic drift and the detrimental effects of inbreeding depression are apparent" and a similar population should be used. [9] [10] Different populations of the same species have different deleterious traits, and therefore their cross breeding is less likely to result in homozygosity at most loci in the offspring. This is known as outbreeding enhancement, which can be performed in extreme cases of severe inbreeding [9] by conservation managers and zoo captive breeders to prevent inbreeding depression.

However, intermixing two different populations can give rise to unfit polygenic traits in outbreeding depression (i.e. yielding offspring which lack the genetic adaptations to specific environmental conditions). These, then, will have a lowered fitness than pure-bred individuals of a particular subspecies that has adapted to its local environment.

In humans

Inbreeding may have both detrimental and beneficial effects. [11] The biological effects of inbreeding depression in humans can on occasion be confounded by socioeconomic and cultural influences on reproductive behavior. [12] Studies in human populations have shown that age at marriage, duration of marriage, illiteracy, contraceptive use, and reproductive compensation are the major determinants of apparent fertility, even amongst populations with a high proportion of consanguinous unions. [13] However, several small effects on increased mortality, [14] longer inter-birth intervals [14] and reduced overall productivity [12] have been noted in certain isolated populations, though other studies show increased fitness of offspring and no effect on lifespan past the 2nd cousin level. [15]

Charles Darwin was one of the first scientists to demonstrate the effects of inbreeding depression, through numerous experiments on plants. Darwin's wife, Emma, was his first cousin, and he was concerned about the impact of inbreeding on his ten children, three of whom died at age ten or younger; three others had childless long-term marriages. [16] [17] [18]

Humans do not seek to completely minimize inbreeding, but rather to maintain an optimal amount of inbreeding vs. outbreeding. Close inbreeding reduces fitness through inbreeding depression, but some inbreeding brings benefits. [19] [20] Indeed, inbreeding "increases the speed of selection of beneficial recessive and co-dominant alleles, e.g. those that protect against diseases." [21]

In wolves

A small isolated highly inbred population of gray wolves in Isle Royale National Park, Michigan, USA, was considered in 2019 to be at imminent risk of extinction. [22] This gray wolf population had been experiencing severe inbreeding depression primarily due to the homozygous expression of strongly deleterious recessive mutations. [22] [23] Defects arising from severe inbreeding among the wolves included reduced survival and reproduction, malformed vertebrae, syndactyly, probable cataracts, an unusual “rope tail” and anomalous fur phenotypes. [22] A separate small inbred population of gray wolves in Scandinavia was also found to suffer from inbreeding depression due to the homozygous expression of deleterious recessive mutations. [24]

Factors reducing inbreeding depression

Whilst inbreeding depression has been found to occur in almost all sufficiently studied species, some taxa, most notably some angiosperms, appear to suffer lower fitness costs than others in inbred populations. [25] Three mechanisms appear to be responsible for this: purging, differences in ploidy, and selection for heterozygosity. [25] It must be cautioned that some studies failing to show an absence of inbreeding depression in certain species can arise from small sample sizes or where the supposedly outbred control group is already suffering inbreeding depression, which frequently occurs in populations that have undergone a recent bottleneck, such as those of the naked mole rat. [25] [26]

Purging selection

Purging selection occurs where the phenotypes of deleterious recessive alleles are exposed through inbreeding, and thus can be selected against. This can lead to such detrimental mutations being removed from the population, and has been demonstrated to occur rapidly where the recessive alleles have a lethal effect. [25] The efficiency of purging will depend on the relationship between the magnitude of the deleterious effect that is unmasked in the homozygotes and the importance of genetic drift, so that purging is weaker for non-lethal than for recessive lethal alleles. [27] For very small populations, drift has a strong influence, which can cause the fixation of sublethal alleles under weak selection. [25] The fixation of a single allele for a specific gene can also reduce fitness where heterozygote advantage was previously present (i.e., where heterozygous individuals have higher fitness than homozygotes of either allele), although this phenomenon seems to make a usually small contribution to inbreeding depression. Although naturally occurring, purging can be important for population survival, deliberately attempting to purge deleterious mutations from a population is not generally recommended as a technique to improve the fitness of captive bred animals. [28] [29] [30] In plants, genetic load can be assessed through a test analogous to an inbreeding depression test called an Autogamy depression test.

Polyploidy

Many angiosperms (flowering plants) can self-fertilise for several generations and suffer little from inbreeding depression. This is very useful for species which disperse widely and can therefore find themselves growing in a novel environment with no conspecifics present. [25] Polyploidy (having more than two paired sets of each chromosome), which is prevalent in angiosperms, ferns and a select few animal taxa, accounts for this. By having several copies of a chromosome, as opposed to two, homozygosity is less likely to occur in inbred offspring. This means that recessive deleterious alleles are not expressed as frequently as with many copies of a chromosome; it is more likely that at least one will contain a functional allele. [25]

Selection for heterozygosity

Selection for heterozygosity is rare, as lost loci undergo purifying selection for homozygous loci. [4] Inbreeding depression has also been found to occur more gradually than predicted in some wild populations, such as in the highly inbred population of Scandinavian wolves. This appears to be due to a selection pressure for more heterozygous individuals, which generally are in better condition and so are more likely to become one of the few animals to breed and produce offspring. [31]

See also

Related Research Articles

<span class="mw-page-title-main">Inbreeding</span> Reproduction by closely related organisms

Inbreeding is the production of offspring from the mating or breeding of individuals or organisms that are closely related genetically. By analogy, the term is used in human reproduction, but more commonly refers to the genetic disorders and other consequences that may arise from expression of deleterious recessive traits resulting from incestuous sexual relationships and consanguinity. Animals avoid inbreeding only rarely.

Small populations can behave differently from larger populations. They are often the result of population bottlenecks from larger populations, leading to loss of heterozygosity and reduced genetic diversity and loss or fixation of alleles and shifts in allele frequencies. A small population is then more susceptible to demographic and genetic stochastic events, which can impact the long-term survival of the population. Therefore, small populations are often considered at risk of endangerment or extinction, and are often of conservation concern.

Inbred strains are individuals of a particular species which are nearly identical to each other in genotype due to long inbreeding. A strain is inbred when it has undergone at least 20 generations of brother x sister or offspring x parent mating, at which point at least 98.6% of the loci in an individual of the strain will be homozygous, and each individual can be treated effectively as clones. Some inbred strains have been bred for over 150 generations, leaving individuals in the population to be isogenic in nature. Inbred strains of animals are frequently used in laboratories for experiments where for the reproducibility of conclusions all the test animals should be as similar as possible. However, for some experiments, genetic diversity in the test population may be desired. Thus outbred strains of most laboratory animals are also available, where an outbred strain is a strain of an organism that is effectively wildtype in nature, where there is as little inbreeding as possible.

Heterosis, hybrid vigor, or outbreeding enhancement is the improved or increased function of any biological quality in a hybrid offspring. An offspring is heterotic if its traits are enhanced as a result of mixing the genetic contributions of its parents. The heterotic offspring often has traits that are more than the simple addition of the parents' traits, and can be explained by Mendelian or non-Mendelian inheritance. Typical heterotic/hybrid traits of interest in agriculture are higher yield, quicker maturity, stability, drought tolerance etc.

A heterozygote advantage describes the case in which the heterozygous genotype has a higher relative fitness than either the homozygous dominant or homozygous recessive genotype. Loci exhibiting heterozygote advantage are a small minority of loci. The specific case of heterozygote advantage due to a single locus is known as overdominance. Overdominance is a rare condition in genetics where the phenotype of the heterozygote lies outside of the phenotypical range of both homozygote parents, and heterozygous individuals have a higher fitness than homozygous individuals.

<span class="mw-page-title-main">Overdominance</span>

Overdominance is a phenomenon in genetics where the phenotype of the heterozygote lies outside the phenotypical range of both homozygous parents. Overdominance can also be described as heterozygote advantage regulated by a single genomic locus, wherein heterozygous individuals have a higher fitness than homozygous individuals. However, not all cases of the heterozygote advantage are considered overdominance, as they may be regulated by multiple genomic regions. Overdominance has been hypothesized as an underlying cause for heterosis.

<span class="mw-page-title-main">Conservation genetics</span> Interdisciplinary study of extinction avoidance

Conservation genetics is an interdisciplinary subfield of population genetics that aims to understand the dynamics of genes in a population for the purpose of natural resource management, conservation of genetic diversity, and the prevention of species extinction. Scientists involved in conservation genetics come from a variety of fields including population genetics, research in natural resource management, molecular ecology, molecular biology, evolutionary biology, and systematics. The genetic diversity within species is one of the three fundamental components of biodiversity, so it is an important consideration in the wider field of conservation biology.

Genetic load is the difference between the fitness of an average genotype in a population and the fitness of some reference genotype, which may be either the best present in a population, or may be the theoretically optimal genotype. The average individual taken from a population with a low genetic load will generally, when grown in the same conditions, have more surviving offspring than the average individual from a population with a high genetic load. Genetic load can also be seen as reduced fitness at the population level compared to what the population would have if all individuals had the reference high-fitness genotype. High genetic load may put a population in danger of extinction.

Genetic viability is the ability of the genes present to allow a cell, organism or population to survive and reproduce. The term is generally used to mean the chance or ability of a population to avoid the problems of inbreeding. Less commonly genetic viability can also be used in respect to a single cell or on an individual level.

<span class="mw-page-title-main">Molecular ecology</span> Subdiscipline of ecology

Molecular ecology is a subdiscipline of ecology that is concerned with applying molecular genetic techniques to ecological questions. It is virtually synonymous with the field of "Ecological Genetics" as pioneered by Theodosius Dobzhansky, E. B. Ford, Godfrey M. Hewitt, and others. Molecular ecology is related to the fields of population genetics and conservation genetics.

In biology, outbreeding depression happens when crosses between two genetically distant groups or populations result in a reduction of fitness. The concept is in contrast to inbreeding depression, although the two effects can occur simultaneously on different traits. Outbreeding depression is a risk that sometimes limits the potential for genetic rescue or augmentations. It is considered postzygotic response because outbreeding depression is noted usually in the performance of the progeny.

Out-crossing or out-breeding is the technique of crossing between different breeds. This is the practice of introducing distantly related genetic material into a breeding line, thereby increasing genetic diversity.

In natural selection, negative selection or purifying selection is the selective removal of alleles that are deleterious. This can result in stabilising selection through the purging of deleterious genetic polymorphisms that arise through random mutations.

<span class="mw-page-title-main">Zygosity</span> Degree of similarity of the alleles in an organism

Zygosity is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism.

<span class="mw-page-title-main">Popular sire effect</span>

The popular sire effect occurs when an animal with desirable attributes is bred repeatedly. In dog breeding, a male dog that wins respected competitions becomes highly sought after, as breeders believe the sire possesses the genes necessary to produce champions. However, the popular sire effect is not just down to wanting to produce a champion. For example, in Staffordshire Bull Terriers there are several popular sires who are used by breeders to produce specific colours that are not favoured in the show ring. The popular sire is often bred extensively with many females. This can cause undetected, undesirable genetic traits in the stud to spread rapidly within the gene pool. It can also reduce genetic diversity by the exclusion of other males.

Genetic purging is the increased pressure of natural selection against deleterious alleles prompted by inbreeding.

Inbreeding avoidance, or the inbreeding avoidance hypothesis, is a concept in evolutionary biology that refers to the prevention of the deleterious effects of inbreeding. Animals only rarely exhibit inbreeding avoidance. The inbreeding avoidance hypothesis posits that certain mechanisms develop within a species, or within a given population of a species, as a result of assortative mating and natural and sexual selection, in order to prevent breeding among related individuals. Although inbreeding may impose certain evolutionary costs, inbreeding avoidance, which limits the number of potential mates for a given individual, can inflict opportunity costs. Therefore, a balance exists between inbreeding and inbreeding avoidance. This balance determines whether inbreeding mechanisms develop and the specific nature of such mechanisms.

Inbreeding in fish is the mating of closely related individuals, leading to an increase in homozygosity. Repeated inbreeding generally leads to morphological abnormalities and a reduction in fitness in the offspring. In the wild, fish have a number of ways to avoid inbreeding, both before and after copulation.

Autogamy or self-fertilization refers to the fusion of two gametes that come from one individual. Autogamy is predominantly observed in the form of self-pollination, a reproductive mechanism employed by many flowering plants. However, species of protists have also been observed using autogamy as a means of reproduction. Flowering plants engage in autogamy regularly, while the protists that engage in autogamy only do so in stressful environments.

This glossary of genetics and evolutionary biology is a list of definitions of terms and concepts used in the study of genetics and evolutionary biology, as well as sub-disciplines and related fields, with an emphasis on classical genetics, quantitative genetics, population biology, phylogenetics, speciation, and systematics. It has been designed as a companion to Glossary of cellular and molecular biology, which contains many overlapping and related terms; other related glossaries include Glossary of biology and Glossary of ecology.

References

  1. ↑ Begon, Michael; Townsend, Colin R.; Harper, John L. (2006). Ecology: from individuals to ecosystems (4th ed.). Blackwell. ISBN   9781405151986. OCLC   63148074.
  2. ↑ Reed, David H.; Lowe, Edwin H.; Briscoe, David A.; Frankham, Richard (2003-05-01). "Inbreeding and extinction: Effects of rate of inbreeding". Conservation Genetics. 4 (3): 405–410. doi:10.1023/A:1024081416729.
  3. ↑ Dolgin, Elie S.; Charlesworth, Brian; Baird, Scott; Cutter, Asher D.; et al. (2007). "Inbreeding and Outbreeding Depression in Caenorhabditis Nematodes". Evolution. 61 (6): 1339–52. doi: 10.1111/j.1558-5646.2007.00118.x . PMID   17542844.
  4. 1 2 3 Charlesworth, Deborah; Willis, John H. (November 2009). "The genetics of inbreeding depression". Nature Reviews Genetics. 10 (11): 783–796. doi:10.1038/nrg2664. PMID   19834483. S2CID   771357.
  5. ↑ Bernstein, H; Byerly, HC; Hopf, FA; Michod, RE (1985). "Genetic damage, mutation, and the evolution of sex". Science. 229 (4719): 1277–81. Bibcode:1985Sci...229.1277B. doi:10.1126/science.3898363. PMID   3898363.
  6. ↑ Michod, R.E. (1996). Eros and Evolution: A Natural Philosophy of Sex. Perseus Books. ISBN   0201442329. OCLC   30625193.
  7. ↑ de Boer, Raïssa A.; Vega-Trejo, Regina; Kotrschal, Alexander; Fitzpatrick, John L. (July 2021). "Meta-analytic evidence that animals rarely avoid inbreeding". Nature Ecology & Evolution. 5 (7): 949–964. Bibcode:2021NatEE...5..949D. doi:10.1038/s41559-021-01453-9. PMID   33941905. S2CID   233718913.
  8. 1 2 Pike VL, Cornwallis CK, Griffin AS (August 2021). "Why don't all animals avoid inbreeding?". Proc Biol Sci. 288 (1956): 20211045. doi:10.1098/rspb.2021.1045. PMC   8334842 . PMID   34344184.
  9. 1 2 Allendorf, Fred W.; Leary, Robb F.; Spruell, Paul; Wenburg, John K. (November 2001). "The problems with hybrids: setting conservation guidelines". Trends in Ecology & Evolution. 16 (11): 613–622. doi:10.1016/S0169-5347(01)02290-X.
  10. ↑ Edmands, Suzanne (2006-11-15). "Between a rock and a hard place: evaluating the relative risks of inbreeding and outbreeding for conservation and management: RELATIVE RISKS OF INBREEDING AND OUTBREEDING". Molecular Ecology. 16 (3): 463–475. doi:10.1111/j.1365-294X.2006.03148.x. PMID   17257106. S2CID   457825.
  11. ↑ Denic, Srdjan; Nicholls, Michael Gary (2007). "Genetic Benefits of Consanguinity Through Selection of Genotypes Protective Against Malaria". Human Biology. 79 (2): 145–158. doi:10.1353/hub.2007.0030. PMID   18027811. S2CID   32818511.
  12. 1 2 Robert, Alexandre; Toupance, Bruno; Tremblay, Marc; Heyer, Evelyne (2009). "Impact of inbreeding on fertility in a pre-industrial population". European Journal of Human Genetics. 17 (5): 673–681. doi:10.1038/ejhg.2008.237. PMC   2986271 . PMID   19092776.
  13. ↑ Bittles, A. H.; Grant, J. C.; Sullivan, S. G.; Hussain, R. (2002). "Does inbreeding lead to decreased human fertility?". Annals of Human Biology. 29 (2): 111–130. doi:10.1080/03014460110075657. PMID   11874619. S2CID   31317976.
  14. 1 2 Ober, C; Hyslop, T; Hauck, WW (January 1999). "Inbreeding effects on fertility in humans: evidence for reproductive compensation". Am. J. Hum. Genet. 64 (1): 225–31. doi:10.1086/302198. PMC   1377721 . PMID   9915962.
  15. ↑ "Third Cousins Have Greatest Number Of Offspring, Data From Iceland Shows". ScienceDaily. Retrieved 2022-07-26.
  16. ↑ Berra, Tim M.; Alvarez, Gonzalo; Ceballos, Francisco C.; et al. (2010). "Was the Darwin/Wedgwood Dynasty Adversely Affected by Consanguinity?". BioScience. 60 (5): 376–383. doi:10.1525/bio.2010.60.5.7. S2CID   35915651.
  17. ↑ "Inbreeding May Have Caused Darwin Family Ills, Study Suggests". Science Daily.
  18. ↑ Clark, R.W. (1984). The Survival of Charles Darwin. Random House. pp. 76, 78. ISBN   039452134X. OCLC   1422025196.
  19. ↑ Berghe, Pierre L. van den (March 1983). "Human inbreeding avoidance: Culture in nature". Behavioral and Brain Sciences. 6 (1): 91–102. doi:10.1017/S0140525X00014850. S2CID   146133244.
  20. ↑ Alvarez, Liliana; Jaffe, Klaus (2004-01-01). "Narcissism Guides Mate Selection: Humans Mate Assortatively, as Revealed by Facial Resemblance, following an Algorithm of "Self Seeking Like"". Evolutionary Psychology. 2 (1): 147470490400200. doi: 10.1177/147470490400200123 . S2CID   16207548.
  21. ↑ Denic, S.; Nagelkerke, N.; Agarwal, M. M. (2011). "On Some Novel Aspects of Consanguineous Marriages". Public Health Genomics. 14 (3): 162–8. doi:10.1159/000321771. PMID   21150168. S2CID   38342159.
  22. 1 2 3 Robinson JA, Räikkönen J, Vucetich LM, Vucetich JA, Peterson RO, Lohmueller KE, Wayne RK (May 2019). "Genomic signatures of extensive inbreeding in Isle Royale wolves, a population on the threshold of extinction". Sci Adv. 5 (5): eaau0757. Bibcode:2019SciA....5..757R. doi:10.1126/sciadv.aau0757. PMC   6541468 . PMID   31149628.
  23. ↑ Kyriazis CC, Wayne RK, Lohmueller KE (February 2021). "Strongly deleterious mutations are a primary determinant of extinction risk due to inbreeding depression". Evol Lett. 5 (1): 33–47. doi:10.1002/evl3.209. PMC   7857301 . PMID   33552534.
  24. ↑ Smeds L, Ellegren H (April 2023). "From high masked to high realized genetic load in inbred Scandinavian wolves". Mol Ecol. 32 (7): 1567–1580. Bibcode:2023MolEc..32.1567S. doi:10.1111/mec.16802. PMID   36458895.
  25. 1 2 3 4 5 6 7 Frankham, Richard; Briscoe, David A.; Ballou, J.D. (2002). Introduction to conservation genetics. Cambridge University Press. doi:10.1017/CBO9780511808999. ISBN   9780511077562. OCLC   57506188.
  26. ↑ Liberg, Paul; Firmin B. (2007). "Role of inbreeding depression and purging in captive breeding and restoration programmes". Molecular Ecology. 17 (1): 334–343. doi: 10.1111/j.1365-294X.2007.03433.x . PMID   18173505. S2CID   28421723.
  27. ↑ García-Dorado, A (2012). "Understanding and predicting the fitness decline of shrunk populations: inbreeding, purging, mutation and standard selection". Genetics. 190 (4): 1461–76. doi:10.1534/genetics.111.135541. PMC   3316656 . PMID   22298709.
  28. ↑ Garcia-Dorado, A (2015). "On the consequences of ignoring purging on genetic recommendations of MVP rules". Heredity. 115 (3): 185–7. doi:10.1038/hdy.2015.28. PMC   4814235 . PMID   25873145.
  29. ↑ Leberg, P. L.; Firmin, B. D. (2008). "Role of inbreeding depression and purging in captive breeding and restoration programmes". Molecular Ecology. 17 (1): 334–343. Bibcode:2008MolEc..17..334L. doi: 10.1111/j.1365-294X.2007.03433.x . PMID   18173505. S2CID   28421723.
  30. ↑ Crnokrak, P; Barrett, SCH (2002). "Purging the genetic load: a review of the experimental evidence". Evolution. 56 (12): 2347–58. doi: 10.1111/j.0014-3820.2002.tb00160.x . PMID   12583575.
  31. ↑ Bensch, Staffan; Andren, Hanson; Pederson, Sand; Sejberg, Wabakken; Akesson, Liberg (2006). "Selection for heterozygosity gives hope to wild wolves". PLOS ONE. 1 (1): e72. doi: 10.1371/journal.pone.0000072 . PMC   1762340 . PMID   17183704.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.