It's well-known that inbreeding is problematic, but scientists say that excessive "outbreeding" also has genetic consequences.
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The Syrian refugee crisis, for example, created vivid images of Muslims surging into Europe, fuelling the fears of those who fret that non-whites are outbreeding whites and will one day "replace" them in their ancestral homelands.
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Outbreeding depression is the reduced biological fitness in the offspring of distantly related parents. The decline in fitness due to outbreeding is attributed to a breakup of coadapted gene complexes or favorable epistatic relationships. Unlike inbreeding depression, outbreeding depression emphasizes interactions between loci rather than within them. Inbreeding and outbreeding depression can occur at the same time.
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For plants, outbreeding depression represents a partial crossing barrier. Unfortunately, outbreeding depression is not understood well in angiosperms. After observing Ipomopsis aggregata over time by crossing plants that were between 10–100m apart, a pattern was noticed that plants that were farther away spatially had a higher likelihood of outbreeding depression. Some general takeaways from this were that spatial patterns of selection on plant genotypes will vary in scale and pattern, and outbreeding depression reflects the genetic constitution of "hybrid" progeny and the environments in which the parents and progeny grow.
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This means that outbreeding depression cannot be predicted in angiosperms yet, but environment has a role.
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Risks of outbreeding depression increase with increased distance between populations. The risk of outbreeding depression during genetic rescue often limits the ability to increase a small or fragmented gene pool's genetic diversity. The spawn of an intermediate of two or more adapted traits can render the adaptation less effective than either of the parental adaptations. Three main mechanisms influence outbreeding depression; genetic drift, population bottlenecking, differentiation of adaptations, and set chromosomal dissimilarities resulting in sterile offspring.
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In 1919, Edward M. East and Donald F. Jones worked together on monographs on experimental biology, including a book on inbreeding and outbreeding and their genetic and sociological significance. This work covers reproduction among plants and animals, the mechanism of reproduction, the mechanism of heredity, mathematical considerations of inbreeding, inbreeding experiments with animals and plants, hybrid vigor or heterosis, conceptions as to the cause of hybrid vigor, sterility and its relations to inbreeding and crossbreeding, the role of inbreeding and outbreeding in evolution, and the value of inbreeding and outbreeding in plant and animal improvement. East and Jones explicitly considered inbreeding and outbreeding in man, their effect on the individual, and the intermingling of races and review the national stamina literature. In Inbreeding and Outbreeding: Their Genetic and Sociological Significance, East proposed the theory that inbreeding in a genetically diverse stock caused increased homozygosity.
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Whereas the second two (F and A) deal with genetic factors such as inbreeding depression and outbreeding depression, genetic drift etc.
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Scientists surmise that the drive in humans, as in many animals, to engage in exogamy (outbreeding) is evolutionarily adaptive, as it reduces the risk of children having genetic defects caused by inbreeding, as a result of inheriting two copies of a recessive gene.Thornhill, N. 1993. The Natural History of Inbreeding and Outbreeding: Theoretical and Empirical Perspectives. The University of Chicago Press, Chicago.
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For the third mechanism, examples include poison dart frogs, anole lizards, and ciclid fish. Selection over genetic drift seems to be the dominant mechanism for outbreeding depression.
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This suggests that the fitness of male D. montana is associated with the frequency of their courtship songs. The frequency of males' songs is also subject to considerable outbreeding depression.
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Not all outcrosses result in heterosis. For example, when a hybrid inherits traits from its parents that are not fully compatible, fitness can be reduced. This is a form of outbreeding depression.
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The different mechanisms of outbreeding depression can operate at the same time. However, determining which mechanism is likely to occur in a particular population can be very difficult. There are three main mechanisms for generating outbreeding depression: # Fixed chromosomal differences resulting in the partial or complete sterility of F1 hybrids. # Adaptive differentiation among populations # Population bottlenecks and genetic drift Some mechanisms may not appear until two or more generations later (F2 or greater), when recombination has undermined vitality of positive epistasis.
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Outbreeding is when organisms mate with unrelated individuals, increasing heterozygosity in a population. Although new diversity is often beneficial, if there a large genetic differences between the two individuals it can result in outbreeding depression. This is a reduction in fitness, similar to that of inbreeding depression, but arises from a number of different mechanisms, including taxonomic issues, chromosomal differences, sexual incompatibility, or adaptive differences between the individuals. A common cause is chromosomal ploidy differences and hybridization between individuals leading to sterility.
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Within the colony, other female workers do not reproduce or mate as their ovaries become inactive in the presence of pheromones produced by the queen. Unlike the eusocial order Hymenoptera, termite colonies inbreed which has been found to increase immunity to pathogens that may be exposed to the colony through introduction of outside members. Outbreeding studies performed with Z. angusticollis and colonies that are genetically dissimilar have resulted in higher mortality rates among the colony. Therefore, Z. angusticollis inbreeding and monogamous behaviors help them to avoid outbreeding depression.
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Keith Spalding, a bird fancier in California. There can be problems if birds of unknown pedigree are released into the wild, as the viability of such hybrids and their offspring is often reduced (see Haldane's Rule and outbreeding depression).
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Workers within the same colony all have one of two maternal alleles, which guarantees relatedness as offspring of the same queen. This species chooses to forms drones in order to encourage outbreeding which increases the fitness of the colony unlike inbreeding.
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Hybridisation in this manner threatens the Otago black stilt and the Chatham Islands' Forbes parakeet and has eliminated the South Island brown teal as a subspecies. Researchers have also identified potential interbreeding as threatening the Māui with hybrid breakdown and outbreeding depression.
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In these he tried to show how the history of man can be at least partially analysed in terms of genetic laws, breeding patterns, founder effects and Darwinian evolution. Darlington's views were an unusual endorsement of the complementary virtues of inbreeding, as well as of outbreeding.
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The first inbred strains were grown in 1908. His first book, Inbreeding and Outbreeding, was on this subject. East played an important role in the development of hybrid corn. His main interest was in the theoretical interpretations from inbreeding leading to reduction and crossbreeding leading to increased growth.
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Hybrid vigor in the first generation can, in some circumstances, be strong enough to mask the effects of outbreeding depression. An example of this is that plant breeders will make F1 hybrids from purebred strains, which will improve the uniformity and vigor of the offspring, however the F2 generation are not used for further breeding because of unpredictable phenotypes in their offspring. Unless there is strong selective pressure, outbreeding depression can increase in further generations as coadapted gene complexes are broken apart without the forging of new coadapted gene complexes to take their place. If the outcrossing is limited and populations are large enough, selective pressure acting on each generation can restore fitness.
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Outbreeding depression involves reduced fitness as a result of random mating, which occurs due to the breakdown of coadapted gene complexes by combining allele that do not cross well with those from a different subpopulation. However, it is important to note that outbreeding depression becomes more detrimental the longer (temporally) that subpopulations have been separated, and that this does hypothesis does not provide an initial mechanism for the evolution of natal philopatry. A second hypothesis explains the evolution of natal philopatry as a method of reducing the high costs of dispersal among offspring. A review of records of natal philopatry among passerine birds found that migrant species showed significantly less site fidelity than sedentary birds.
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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.
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L. hemichalceum displays different mating behaviors for different morphologies. Males who are born with the typical small body morphology mate away from the nest. This contributes to outbreeding and makes the genetic pool much more diverse. However, males that display the macrocephalic body morphology will remain in the nest and mate with females there.
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Landmark mating in this system is advantageous for the promotion of outbreeding. Each lek is composed of related males that capture contiguous territories. One-third of all P. biglumis females will mate with multiple male partners, all of whom will be related. P. biglumis females’ polyandrous activity make them unique among all other paper wasps.
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Non-obese diabetic (NOD) mice exhibit a susceptibility to spontaneous development of autoimmune insulin dependent diabetes mellitus (IDDM). The NOD strain and related strains were developed at Shionogi Research Laboratories in Aburahi, Japan by Makino and colleagues and first reported in 1980. The group developed the NOD strain by an outbreeding of the cataract- prone strain from JcI:ICR mice.
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However, active avoidance of close kin as mates was observed, as indicated by the substantially lower relatedness in actual breeding pairs compared to potential ones expected if there were random mating. This finding, as well as heterozygous excesses in immature lizards from disturbed (as well as undisturbed) habitats indicted that it maintains outbreeding in the face of increased accumulation of relatives.
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In biology, exogamy more generally refers to the mating of individuals who are relatively less related genetically: that is, outbreeding as opposed to inbreeding. This benefits the offspring as it reduces the risk of the offspring inheriting two copies of a defective gene. Increasing the genetic diversity of the offspring is thought to improve their chances of surviving to reproduce themselves.
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Inbreeding is a common phenomenon among naked mole-rats within a colony. Prolonged inbreeding is usually associated with lower fitness. However, the discovery of a disperser role has revealed an outbreeding mechanism in addition to inbreeding avoidance. Dispersers are morphologically, physiologically as well as behaviorally distinct from colony members and actively seek to leave their burrow when an escape opportunity presents itself.
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In other registries, they are part of the Siamese or Oriental Shorthair breeds (and may not be accepted as show and breeding quality, depending on what colors the registry permits in these breeds, and whether they permit any outbreeding in the lineage). Because these cats are a crossbreed, various registries are resistant to accepting either as breeds, or as valid Siamese.
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The Bonneville germplasm was sourced from NW Utah near the Nevada border in USDA plant hardiness zone 6b. However, the Bonneville germplasm was found to be a genetically distinct population and is recommended for use in northwestern Utah. Local germplasms are recommended to prevent outbreeding depression. The three germplasms were made available by the USDA’s Agricultural Research Service for revegetation and restoration efforts.
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Combinations of alleles that have evolved to work well together may not work when recombined with a different suite of coevolved alleles, leading to outbreeding depression. Segregation load is the presence of underdominant heterozygotes (i.e. heterozygotes that are less fit than either homozygote). Recombination load arises through unfavorable combinations across multiple loci that appear when favorable linkage disequilibria are broken down.
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Macrostomum hystrix prefers outbreeding if partners are available because selfing also has costs. The amount of offspring of worms that selfed is reduced, as is the offspring's survival. As a consequence, Macrostomum hystrix only begins selfing in the extended absence of mating partners: delayed selfing represents a conditional reproductive strategy which allows them to deal with periodic conditions of low mate abundance.
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Korean wolves mating in the Tama Zoological Park, Japan Wolves are monogamous, mated pairs usually remaining together for life. Should one of the pair die, another mate is found quickly. With wolves in the wild, inbreeding does not occur where outbreeding is possible. Wolves become mature at the age of two years and sexually mature from the age of three years.
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Most pitcher plant habitats have been destroyed in this critical mid-Atlantic region to the point where less than 100 yellow pitchers plants were left in just two natural sites in southern Virginia by 2007.Sheridan, Philip M. and Karowe, David N. (2000). Inbreeding, outbreeding, and heterosis in the yellow pitcher plant, Sarracenia flava (Sarraceniaceae), in Virginia. American Journal of Botany, 87(11): 1628-1633.
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English naturalist and geologist, Charles Darwin, can offer some observations in regards to why some people might find other races more attractive than their own. Attraction can be viewed as a mechanism for choosing a healthy mate. People's minds have evolved to recognize aspects of other peoples' biology that makes them an appropriate or good mate. This area of theory is called optimal outbreeding hypothesis.
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Genetic diversity has shown to be as important as species diversity for restoring ecosystem processes. Hence ecological restorations are increasingly factoring genetic processes into management practices. Population genetic processes that are important to consider in restored populations include founder effects, inbreeding depression, outbreeding depression, genetic drift, and gene flow. Such processes can predict whether or not a species successfully establishes at a restoration site.
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Time course imaging of two maize inbreds and their F1 hybrid (middle) exhibiting heterosis. 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. These effects can be due to Mendelian or non-Mendelian inheritance.
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Among migratory species, the cost of dispersal is paid either way. If the optimal-inbreeding hypothesis was correct, the benefits of inbreeding should result in philopatry among all species. Inbreeding depression is a phenomenon whereby deleterious alleles become fixed more easily within an inbreeding population. Inbreeding depression is demonstrably costly and accepted by most scientists as a greater cost than those of outbreeding depression.
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Seasonal thermogenesis of southern flying squirrels Glaucomys volans. Journal of Mammalogy. 82(1):51-64. Compared to individuals who nest alone in winter, squirrels in aggregates can save 30 percent more energy. Although southern flying squirrels do show a preference for relatedness, they are tolerant of nonrelated but familiar individuals, possibly because in addition to providing heat energy for the aggregation, outsiders will promote outbreeding.
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If outbreeding is limited and the population is large enough, selective pressure acting on each generation may be able to restore fitness. However, the population is likely to experience a multi-generational decline of overall fitness as selection for traits takes multiple generations. Selection acts on outbred generations using increased diversity to adapt to the environment. This may result in greater fitness among offspring than the original parental type.
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As opposed to outcrossing or outbreeding, inbreeding is the process by which organisms with common descent come together to mate and eventually procreate. An archetype of inbreeding is self-pollination. When a plant has both anthers and a stigma, the process of inbreeding can occur. Another word for this self- fertilization is autogamy, which is when an anther releases pollen to attach to the stigma on the same plant.
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The major beneficial outcome under this hypothesis is the protection of a local gene complex that is finely adapted to the local environment. Another proposed benefit is the reduction the cost of meiosis and recombination events. Under this hypothesis, non-philopatric individuals would be maladapted and over multi-generational time, philopatry within a species could become fixed. Evidence for the optimal-inbreeding hypothesis is found in outbreeding depression.
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Believing with the Drosophila workers that most mutations were recessive and deleterious, East concluded that the increased homozygosity caused by inbreeding should generally be accompanied by detrimental effects. His theory also explained why inbreeding was not necessarily deleterious in all cases. Unless deleterious recessives were present, inbreeding caused no ill effects. Outbreeding of course had the opposite effect of increasing heterozygosity and was often accompanied by heterosis, or hybrid vigor.
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This chemical distinction between virginal and old females allows males to distinguish between the two, thus enabling male choice in sexual partner. They are also capable of discriminating between familiar and unknown queens, and l generally are more attracted to queens of a foreign colony, which likely arose as an outbreeding mating strategy, which increases genetic diversity of the population and decreases the probability that the next generation would be subject to genetic disease.
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In isolated worms, it has been shown that Macrostomum hystrix does not only use hypodermic insemination for outbreeding but also self-fertilization, or "selfing". To achieve this, they inject their sperm into themselves — mainly into their own heads, due to physical constraints. From there, the sperm apparently migrate to the site of fertilization. Worms that were isolated showed significantly more sperm in their heads, compared to worms that had the opportunity to cross-fertilize.
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Agave schottii is a clonal plant, meaning it has the ability to clone itself and produce genetically identical offspring vegetatively. This method of asexual reproduction is not favorable as it produces offspring with low heterozygosity, or low genetic diversity. Experimentation shows that this plant favors outbreeding with an optimal range between 10 and 100 meters (33 feet and 330 feet). The greater the proximity of cross-breeders, the lower the genetic diversity.
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The introduction of genetic material into the gene pool of a population by human intervention can have both positive and negative effects on populations. When genetic material is intentionally introduced to increase the fitness of a population, this is called genetic rescue. When genetic material is unintentionally introduced to a population, this is called genetic pollution and can negatively affect the fitness of a population (primarily through outbreeding depression), introduce other unwanted phenotypes, or theoretically lead to extinction.
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In small populations, as long as children born with inheritable birth defects die (or are killed) before they reproduce, the ultimate effect of inbreeding will be to decrease the frequency of defective genes in the population; over time, the gene pool will be healthier. However, in larger populations, it is more likely that large numbers of carriers will survive and mate, leading to more constant rates of birth defects.Thornhill, Nancy, ed. 1993 The Natural History of Inbreeding and Outbreeding.
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It is often used for populations of species that are at a high risk of extinction. A successful genetic rescue occurs when the addition of new genes effectively introduces genetic diversity that leads to increased population size and growth rate, as well as a greater population fitness. An unsuccessful genetic rescue may occur if the addition of new genes causes outbreeding depression, which decreases their population fitness. Too much gene flow may lead to genetic swamping through extensive hybridization.
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Darwin's speculations on the origin of species convinced him that cross-fertilisation played an important role in keeping specific forms consistent. He rejected the doctrine that the characteristics of a species were static, and was aware from animal husbandry that inbreeding could lead to changes, often deleterious. He thought that natural outbreeding through cross-fertilisation would keep wild species homogenous yet vigorous. Cross-fertilisation would confer an evolutionary advantage by spreading favourable changes throughout a reproductive community.
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From a genetic point of view, aversion to breeding with close relatives results in fewer congenital diseases. If one person has a faulty gene, breeding outside his group increases the chances that his partner will have another functional type gene and their child may not suffer the defect. Outbreeding favours the condition of heterozygosity, that is having two nonidentical copies of a given gene. J. F. McLennan holds that exogamy was due originally to a scarcity of women among small bands.
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Although most Rubiaceae species are hermaphroditic, outbreeding is promoted through proterandry and spatial isolation of the reproductive organs. More complex reproductive strategies include secondary pollen presentation, heterodistyly, and unisexual flowers. Secondary pollen presentation (also known as stylar pollen presentation or ixoroid pollen mechanism) is especially known from the Gardenieae and related tribes. The flowers are proterandrous and the pollen is shed early onto the outside of the stigmas or the upper part of the style, which serve as a 'receptaculum pollinis'.
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Crosses of copepods from different populations of T. californicus have been used to study how reproductive isolation accumulates between diverging population to gain insights into the process of speciation. For crosses between many populations a pattern that has been called hybrid breakdown is observed; this means that first generation hybrids have high survival and reproduction (fitness), while the second generation hybrids have lower and more variable fitness.Edmands, S. 1999. Heterosis and outbreeding depression in interpopulation crosses spanning a wide range of divergence. Evolution 53:1757-1768.
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Wing buds of a nymph Immature termites on the sexual, or reproductive, line are called nymphs and can be distinguished from workers by the presence of wing buds. Under natural conditions, the work that they do in the nest is negligible compared to that done by workers. They can feed themselves, but there is debate over how long (over how many instars) they retain this ability. Alates (from the Latin ālātus, "having wings") are winged, sexually mature adults that are capable of dispersal and outbreeding.
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Risks include increased injury and mortality during dispersal and the possibility of settling in an unfavorable environment. Time spent dispersing is time that often cannot be spent on other activities such as growth and reproduction. Finally dispersal can also lead to outbreeding depression if an individual is better adapted to its natal environment than the one it ends up in. In social animals (such as many birds and mammals) a dispersing individual must find and join a new group, which can lead to loss of social rank.
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Species can live in the same environment, yet show very limited gene flow due to reproductive barriers, fragmentation, specialist pollinators, or limited hybridization or hybridization yielding unfit hybrids. A cryptic species is a species that humans cannot tell is different without the use of genetics. Moreover, gene flow between hybrid and wild populations can result in loss of genetic diversity via genetic pollution, assortative mating and outbreeding. In human populations, genetic differentiation can also result from endogamy, due to differences in caste, ethnicity, customs and religion.
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8\. Sex and Smelly T-shirts : The chapter describes the famous experiment that called for female partners to sniff boxes containing their male partners' T-shirts, which they had worn for two days. There was a slight association between finding the smell sexy and the two partners having different compatibility genes. It could possibly indicate sexual selection for outbreeding, at least in the HLA system. 9\. Connections with the Mind : Davis describes what is known of the role of compatibility genes in the brain. 10\.
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Females can mate with multiple males (with as many as five), but it is not necessarily advantageous, because unnecessary matings waste time and energy. Polyandry may contribute to outbreeding if females preferentially mate with unrelated males. Polyandry can occur if the benefits of mating more than once are greater than the costs. It can also occur if males force female spiders to mate again through infanticide because females can lay multiple clutches, even though mating multiple times is against the female's interests because it generally reduces the female's fitness.
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He includes self-conscious, ironic dance moves and off-mic (often off-stage) singing in his live performances. Four solo albums have been released under his own name, The Complete Guide to Insufficiency (2005), It's in There Somewhere (2007), the studio recorded album Outbreeding (2010) and triple LP Crippling Lack (2016), as well as the EPs Anchovies (2007) and Boating Disasters (2010). In 2007 he collaborated with Leeds chamber music group 7 Hertz to release David Thomas Broughton vs. 7 Hertz, and released a single during the same year with Chris Casati.
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Multiple studies have shown, in double-blind experiments, females prefer the scent of males who are heterozygous at all three MHC loci. The reasons proposed for these findings are speculative; however, it has been argued that heterozygosity at MHC loci results in more alleles to fight against a wider variety of diseases, possibly increasing survival rates against a wider range of infectious diseases. The latter claim has been tested in an experiment, which showed outbreeding mice to exhibit MHC heterozygosity enhanced their health and survival rates against multiple-strain infections.
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The Ukrainian Levkoy is recent man-made breed (2000–2011), originally developed by Elena Biriukova in Ukraine. Created by crossing or by outbreeding hairless Donskoy females with Scottish Fold metis males, the Ukrainian Levkoy has a distinct and unique appearance. Two spontaneous mutations of dominant FD genes of cats with folded ears (that appeared in a simple domestic cat in Scotland) were used, as well as a spontaneous natural dominant mutation of hairlessness or baldness of the domestic cat gene BD in Russia. Both had appeared in the last century in Scotland and in Russia.
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Within a species, there has also been found to be variation in rates of philopatry, with migratory populations exhibiting low levels of philopatry – further suggesting that the ecological cost of dispersal, rather than genetic benefits of either inbreeding or outbreeding, is the driver of natal philopatry. A number of other hypotheses exist. One such is that philopatry is a method, in migratory species, of ensuring that the sexes interact in breeding areas, and that breeding actually occurs. A second is that philopatry provides a much higher chance of breeding success.
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For example, more than 99% of Laysan albatross (Phoebastria immutabilis) in a study returned to exactly the same nest in consecutive years. Such site-specificity can lead to speciation, and has also been observed in the earliest stages of this process. The shy albatross (Thalassarche [cauta] cauta) was shown to have genetic differences in its microsatellites between three breeding colonies located off the coast of Tasmania. The differences are not currently sufficient to propose identifying the populations as distinct species; however divergence is likely to continue without outbreeding.
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The Canadian Cat Association (CCA) has a placeholder page for the breed on their website, but it is empty of content. The PDF version, cited above, includes references to 2004 cut-off dates for outbreeding, as if still in the future. A small breed club, the International York Chocolate Federation (IYCF) was founded in Italy, but seems to have been dormant since 2004. It claims affiliation with Feline Federation Europe (FFE), which since 2004 publishes a York Chocolate standard (missing the color information) and the World Felinological Federation (WFF), a Russian group, which does not recognize this breed.
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Inbreeding can change the frequency of allele distribution in a population, and potentially result in a change to crucial genetic diversity. Additionally, outbreeding depression can occur if a reintroduced population can hybridize with existing populations in the wild, which can result in offspring with reduced fitness, and less adaptation to local conditions. To minimize both, practitioners should source for individuals in a way that captures as much genetic diversity as possible, and attempt to match source site conditions to local site conditions as much as possible. Capturing as much genetic diversity as possible, measured as heterozygosity, is suggested in species reintroductions.
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It is called genetic pollution when it negatively impacts on the fitness of a population, such as through outbreeding depression and the introduction of unwanted phenotypes which can lead to extinction. Conservation biologists and conservationists have used the term to describe gene flow from domestic, feral, and non-native species into wild indigenous species, which they consider undesirable. They promote awareness of the effects of introduced invasive species that may "hybridize with native species, causing genetic pollution". In the fields of agriculture, agroforestry and animal husbandry, genetic pollution is used to describe gene flows between genetically engineered species and wild relatives.
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This strategy is effective against individual flowers fertilising themselves, but does nothing to prevent geitonogamy: fertilisation of flowers by different flowers on the same plant. Because of the way flowers are clustered together in heads, this must be quite common, although whether it results in successful fruit set is another matter: isozyme studies have observed "intense selection against homozygotes", a fairly common outbreeding strategy in plants that set much seed. Assessments of the mating system of this species have found that outcrossing rates vary between populations. Populations in relatively intact bushland have high outcrossing rates, but those in more disturbed environments are both more inbred on average, and more variable.
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No evidence so far indicates the Hector's and Māui dolphins interbreed, but given their close genetic composition, they likely could. Interbreeding may increase the numbers of dolphins in the Māui range and reduce the risk of inbreeding depression, but such interbreeding could eventually result in a hybridisation of the Māui back into the Hector's species and lead to a reclassification of Māui as again the North Island Hector's. Hybridisation in this manner threatens the Otago black stilt and the Chatham Islands' Forbes parakeet and has eliminated the South Island brown teal as a subspecies. Researchers have also identified potential interbreeding as threatening the Māui with hybrid breakdown and outbreeding depression.
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The first mechanism has the greatest effects on fitness for polyploids, an intermediate effect on translocations, and a modest effect on centric fusions and inversions. Generally this mechanism will be more prevalent in the first generation (F1) after the initial outcrossing when most individuals are made up of the intermediate phenotype. An extreme case of this type of outbreeding depression is the sterility and other fitness-reducing effects often seen in interspecific hybrids (such as mules), which involves not only different alleles of the same gene but even different orthologous genes. Examples of the second mechanism include stickleback fish, which developed benthic and lymnetic forms when separated.
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Every known individual of the California condor population has been captured and then bred using research from microsatellite regions in their genome. To found a captive breeding population with adequate genetic diversity, breeders usually select individuals from different source populations—ideally, at least 20-30 individuals. Founding populations for captive breeding programs have often had fewer individuals than ideal because of their threatened state, leaving them more susceptible to challenges such as inbreeding depression. To overcome challenges of captive breeding such as adaptive differences, loss of genetic diversity, inbreeding depression, and outbreeding depression and get desired results, captive breeding programs use many monitoring methods.
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Some of them consisted of small groups of stone structures (talaiots, tumuli), scattered across the island, and frequently serving as boundary stones between the towns. Some of these ceremonial centers consisted of a line of up to seven stone structures across a distance of more than half a kilometer. The abundance of these centers serves as evidence of their importance: most likely they were where frequent disputes were resolved, and where various festivities were celebrated. The centers also served as a seasonal and economic calendar (economic activities such as sowing, harvests, hunting), in which the young of various towns could meet (thus guaranteeing sexual outbreeding).
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However, "dioecy has proven difficult to explain simply as an outbreeding mechanism in plants that lack self-incompatibility". Resource-allocation constraints may be important in the evolution of dioecy, for example, with wind-pollination, separate male flowers arranged in a catkin that vibrates in the wind may provide better pollen dispersal. In climbing plants, rapid upward growth may be essential, and resource allocation to fruit production may be incompatible with rapid growth, thus giving an advantage to delayed production of female flowers. Dioecy has evolved separately in many different lineages, and monoecy in the plant lineage correlates with the evolution of dioecy, suggesting that dioecy can evolve more readily from plants that already produce separate male and female flowers.
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The tree is well suited to intense heat and sunlight and its dense network of lateral roots and its thick, long taproot make it drought-tolerant. The dense shade it provides slows the evaporation of surface water and its root nodules promote nitrogen fixation, a symbiotic process by which gaseous nitrogen (N2) from the air is converted into ammonium (NH4+, a form of nitrogen available to the plant). M. pinnata is also a fresh water flooded forest species as it can survive total submergence in sweet water for few months continuously. M. pinnata tree is common in Tonlesap lake swamp forests in Cambodia Millettia pinnata is an outbreeding diploid legume tree, with a diploid chromosome number of 22.
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Also, the polygynous colonies usually had queens that were related to their male mates, which was not the case in the monogynous colonies, suggesting a difference in dispersal between the two types. Based on this data, polygynous colonies have limited dispersal and will usually mate within the colony, while the monogynous colonies rely on outbreeding and a higher degree of dispersal. The propensity to disperse also varies between males and females, with the main effect of this being that females that are less prone to dispersal will be more likely to stay in the colony and switch it from monogynous to polygynous. The ability of the female to leave the colony is affect by its physiological condition, where larger females with greater fat stores will preferentially disperse but smaller females are more likely to remain.
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When a species has been extirpated from a site where it previously existed, individuals that will comprise the reintroduced population must be sourced from wild or captive populations. When sourcing individuals for reintroduction, it is important to consider local adaptation, adaptation to captivity (for ex situ conservation), the possibility of inbreeding depression and outbreeding depression, and taxonomy, ecology, and genetic diversity of the source population. Reintroduced populations experience increased vulnerability to influences of drift, selection, and gene flow evolutionary processes due to their small sizes, climatic and ecological differences between source and native habitats, and presence of other mating-compatible populations. If the species slated for reintroduction is rare in the wild, it is likely to have unusually low population numbers, and care should be taken to avoid inbreeding and inbreeding depression.
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The album Outbreeding, was released in 2010 on Brainlove Records. Also in 2010 he released Boating Disasters, a four track EP containing, among others, newer versions of the songs "Perfect Louse" and "Ain't Got No Sole" from It's in There Somewhere. Broughton's 2016 release, Crippling Lack, was recorded in France and via email exchange while he was living in Pyongyang, and features contributions from artists such as Aidan Moffat, Beth Orton, Jordan Geiger, Sam Amidon, Luke Drozd, Rachael Dadd and ICHI. The basic tracks were recorded in at Le Noize Maker Studios in France, and after Broughton returned to Korea, French players Timothee Couteau, Olivier Minne and Bastien Loufrani were brought in to add parts, which were approved or adjusted under instruction by Broughton after receiving mixes by email.
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There is evidence of admixture that occurred after domestication that is common within local populations of wolves and dogs. This implies that the genomic diversity found in dogs may represent interbreeding with local wolf populations and not their descent from them, which confounds the ability to infer the dog's origin. The short divergence time between dogs and wolves followed by their continuous admixture has led to 20% of the genome of East Asian wolves and 7–25% of the genome of European and Middle Eastern wolves showing contributions from dogs. Whole genome sequencing indicates that while there has been widespread geneflow from dogs into different wolf populations, the world's dog population forms a homogenous group with little evidence of outbreeding with wolves, apart from deliberate crossings such as the Sarloos wolfdog.
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Following the culture of "C-Fern" in dishes it can be transplanted to a dirt substrate, where it can be further allowed to grow and future generations can be used for subsequent studies. Monilophytes are generally studied far less than other groups of plants and a full genome sequence is not yet available, however due to the development of "C-Fern" research into fern biology has been more prevalent and C. richardii has been used as a model organism to study vascular plant cell walls, alternation of generations (and associated mutations), genetics, population dynamics, and the effects of mitotic disrupter herbicides, among other topics. Despite being genetically identical the inoculated spores can give rise to both hermaphrodites and male gametophytes, depending on the secretion of Antheridiogen; this phenomenon has been used to study plant pheromones and the cascade of events that leads to epigenetic changes in ferns. The ability to switch from bisexual to all male spores may provide an evolutionary advantage by promoting outbreeding.
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In some species of Hemiptera the adults remain with their aggregated immature offspring, sometimes in protective roles. The range of functions is very wide in detail, but among the more important classes of function are security against predators, success in food location, wide range of mate choice, with concomitant increase of outbreeding opportunities, location with other members of the same species (sometimes adherence to separate communities can almost amount to parapatric residence when say, different communities of rats or chimpanzees have violent mutual antipathy). There also are various forms of educational function, such as in some species where the young must learn the correct mate recognition skills, and in highly intelligent species such as crows and elephants, must learn the necessary social skills and the necessary traditional foraging techniques in their region. Aggregation activities are not restricted to the animal kingdom; for one example, a fundamental class of aggregations occurs in the various groups of slime molds, in which separate cells actually aggregate in the process of constructing their reproductive structure.
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