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Hey guys, another one of my threads.
As I always state, this list isn’t going to be perfect, so I always encourage people to make their own top ten-twenty lists with their own research. This is the best I came up with, with my own knowledge and as you know, I am very involved with animals. Please do not take these lists so seriously and just enjoy them for what they are, considering they are just meant to be a bit of fun. With what I’ve studied over the years, I always want to show everyone my own research so it’s all in good nature.
Why do nearly all living things avoid inbreeding? Because in general, it is quite bad for a population or an organism to be inbred. There is a well studied, although only partially understood phenomenon called inbreeding depression. Inbreeding depression is thought to be caused primarily by the collection of a multitude of deleterious mutations, few in themselves fatal, but all diminishing fitness. Normally, in an outbreeding population these alleles would be selected against, hidden, or corrected by the presence of good alleles (versions of genes) in the population. So getting to the point, in many animals, inbreeding will affect the health/fitness of their offspring, and through generations, because of their genes being so close together, will cause visual deformity amongst their young, which in turn is called inbreeding depression.
Many endangered animals which are almost forced to inbreed are at a huge risk of health defects and other medical issues but here’s a list of animals that actually can survive and create somewhat healthy offspring through inbreeding despite low effective population pools.
This list is in no particular order, so they won’t be numbered.
The top 6 animals that can inbreed, that has shown to produce somewhat healthy offspring
Now I’m not saying any of these animals offspring are going to come out perfect all the time, obviously there are going to be birth defects throughout inbreeding, but some of these animals on this list have a much lower risk to inbreeding depression compared to most animals (including us) while others on this list can completely inbreed without incurring inbreeding depression at all.
Black Robin
The Chatham Island black robin is one of the world’s most highly inbred birds. Severe habitat alterations and the introduction of exotic mammalian predators, such as rats and cats, caused the extinction of black robins on most of the Chatham Islands. By the 1960s the only remaining population of black robins survived on Tapuaenuku (Little Mangere Island), a small island that was never inhabited. In 1968, a team from the New Zealand Wildlife Service led by Doug Flack studied the remnant black robin population with the aim to establish a second population. Doug Flack's individual marking of birds by using coloured leg bands, revealed during subsequent years that the black robin population was rapidly declining from 18 in 1972 to only 7 in 1976. In 1976, these remaining 7 robins were moved from Tapuaenuku to Mangere Island, where they could be monitored more easily. In the first few years after translocation, the Black Robin Recovery Team – now led by Don Merton – took a hands-off approach and simply monitored the remaining birds. But without drastic, intervening management this number even further decreased to only 5 individuals (named Old Blue, Old Yellow, Old Green, Old White and Red) by 1980. Knowing that only intensive management might save this species from extinction, Don Merton initiated a cross-fostering routine, whereby any eggs laid by black robin females were cross-fostered to Chatham Island tomtits. Tomtits – acting as foster parents – incubated eggs and raised black robin nestlings successfully. To avoid incorrect sexual imprinting, black robin nestlings were often removed from tomtit nests shortly before fledging, and placed into a black robin nests where they could imprint on black robin parents. This ensured that these nestling chose a black robin partner (and not a tomtit as a mate) once they were old enough to breed. The intensive cross-fostering during 1980-88 was highly successful and it rescued this species from the brink of extinction. By 1990, when Don left the Black Robin Recovery Programme, over 100 black robins were on Mangere and Rangatira. By 1998, the population had increased to approximately 200 black robins on these two islands. However, as it turned out, only offspring of one pair – the female Old Blue and her mate Old Yellow – survived and reproduced. Therefore, all black robins that are alive today are descendents of this pair, making the black robin one of the world’s most inbred birds.
Social Spider
The social spiders, which include the velvet spider, cobweb spider etc. are unusual among cooperatively breeding animals in being highly inbred. In contrast, most other social organisms are outbred owing to inbreeding avoidance mechanisms. The social spiders appear to originate from solitary subsocial ancestors, implying a transition from outbreeding to inbreeding mating systems. In mating experiments, scientists have tested whether inbreeding actually results in lower offspring fitness. Two levels of inbreeding were tested: full sibling versus non-sib matings and matings of individuals within and between naturally occurring patches of spiders. Neither full siblings nor patch mates were discriminated against as mates. Sibling matings had no effect on direct fitness traits such as fecundity, hatching success, time to hatching and survival of the offspring. These results suggest a history of inbreeding which may reduce the frequency of deleterious recessive alleles in the population and promote the evolution of inbreeding tolerance. It is likely that the lack of inbreeding avoidance in subsocial predecessors has facilitated the transition to regular inbreeding social systems.
Mauritius Kestrel
While some apparent inbreeding depression was noted in the captive Kestrel birds, it was certainly lower than might be expected given that the effective population size was maybe 5 individuals during the mid-1970s. It is known that several genetic lineages of Mauritius Kestrels have disappeared entirely during the 20th century population decline. However, the debilitating effects of DDT accumulation on the birds' health, and not inbreeding, are considered to have been the major cause for the failure of Temple's breeding program
As I always state, this list isn’t going to be perfect, so I always encourage people to make their own top ten-twenty lists with their own research. This is the best I came up with, with my own knowledge and as you know, I am very involved with animals. Please do not take these lists so seriously and just enjoy them for what they are, considering they are just meant to be a bit of fun. With what I’ve studied over the years, I always want to show everyone my own research so it’s all in good nature.
Why do nearly all living things avoid inbreeding? Because in general, it is quite bad for a population or an organism to be inbred. There is a well studied, although only partially understood phenomenon called inbreeding depression. Inbreeding depression is thought to be caused primarily by the collection of a multitude of deleterious mutations, few in themselves fatal, but all diminishing fitness. Normally, in an outbreeding population these alleles would be selected against, hidden, or corrected by the presence of good alleles (versions of genes) in the population. So getting to the point, in many animals, inbreeding will affect the health/fitness of their offspring, and through generations, because of their genes being so close together, will cause visual deformity amongst their young, which in turn is called inbreeding depression.
Many endangered animals which are almost forced to inbreed are at a huge risk of health defects and other medical issues but here’s a list of animals that actually can survive and create somewhat healthy offspring through inbreeding despite low effective population pools.
This list is in no particular order, so they won’t be numbered.
The top 6 animals that can inbreed, that has shown to produce somewhat healthy offspring
Now I’m not saying any of these animals offspring are going to come out perfect all the time, obviously there are going to be birth defects throughout inbreeding, but some of these animals on this list have a much lower risk to inbreeding depression compared to most animals (including us) while others on this list can completely inbreed without incurring inbreeding depression at all.
Black Robin
The Chatham Island black robin is one of the world’s most highly inbred birds. Severe habitat alterations and the introduction of exotic mammalian predators, such as rats and cats, caused the extinction of black robins on most of the Chatham Islands. By the 1960s the only remaining population of black robins survived on Tapuaenuku (Little Mangere Island), a small island that was never inhabited. In 1968, a team from the New Zealand Wildlife Service led by Doug Flack studied the remnant black robin population with the aim to establish a second population. Doug Flack's individual marking of birds by using coloured leg bands, revealed during subsequent years that the black robin population was rapidly declining from 18 in 1972 to only 7 in 1976. In 1976, these remaining 7 robins were moved from Tapuaenuku to Mangere Island, where they could be monitored more easily. In the first few years after translocation, the Black Robin Recovery Team – now led by Don Merton – took a hands-off approach and simply monitored the remaining birds. But without drastic, intervening management this number even further decreased to only 5 individuals (named Old Blue, Old Yellow, Old Green, Old White and Red) by 1980. Knowing that only intensive management might save this species from extinction, Don Merton initiated a cross-fostering routine, whereby any eggs laid by black robin females were cross-fostered to Chatham Island tomtits. Tomtits – acting as foster parents – incubated eggs and raised black robin nestlings successfully. To avoid incorrect sexual imprinting, black robin nestlings were often removed from tomtit nests shortly before fledging, and placed into a black robin nests where they could imprint on black robin parents. This ensured that these nestling chose a black robin partner (and not a tomtit as a mate) once they were old enough to breed. The intensive cross-fostering during 1980-88 was highly successful and it rescued this species from the brink of extinction. By 1990, when Don left the Black Robin Recovery Programme, over 100 black robins were on Mangere and Rangatira. By 1998, the population had increased to approximately 200 black robins on these two islands. However, as it turned out, only offspring of one pair – the female Old Blue and her mate Old Yellow – survived and reproduced. Therefore, all black robins that are alive today are descendents of this pair, making the black robin one of the world’s most inbred birds.
Social Spider
The social spiders, which include the velvet spider, cobweb spider etc. are unusual among cooperatively breeding animals in being highly inbred. In contrast, most other social organisms are outbred owing to inbreeding avoidance mechanisms. The social spiders appear to originate from solitary subsocial ancestors, implying a transition from outbreeding to inbreeding mating systems. In mating experiments, scientists have tested whether inbreeding actually results in lower offspring fitness. Two levels of inbreeding were tested: full sibling versus non-sib matings and matings of individuals within and between naturally occurring patches of spiders. Neither full siblings nor patch mates were discriminated against as mates. Sibling matings had no effect on direct fitness traits such as fecundity, hatching success, time to hatching and survival of the offspring. These results suggest a history of inbreeding which may reduce the frequency of deleterious recessive alleles in the population and promote the evolution of inbreeding tolerance. It is likely that the lack of inbreeding avoidance in subsocial predecessors has facilitated the transition to regular inbreeding social systems.
Mauritius Kestrel
While some apparent inbreeding depression was noted in the captive Kestrel birds, it was certainly lower than might be expected given that the effective population size was maybe 5 individuals during the mid-1970s. It is known that several genetic lineages of Mauritius Kestrels have disappeared entirely during the 20th century population decline. However, the debilitating effects of DDT accumulation on the birds' health, and not inbreeding, are considered to have been the major cause for the failure of Temple's breeding program
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