Inbreeding Depression as defined by Wikipedia --"Inbreeding depression is reduced fitness in a given population as a result of breeding of related individuals. Breeding between closely related individuals results in more recessive deleterious traits manifesting themselves. The more closely related the breeding pair is, the more homozygous deleterious genes the offspring may have, resulting in very unfit individuals. In general, populations with more genetic variation do not suffer from inbreeding depression. Inbreeding depression is often the result of a population bottleneck. The phenomenon of inbreeding depression may occur in either plant or animal species."
A specific citation of inbreeding depression in Vipera Berus--
"In a small population, matings between relatives are common. This inbreeding may lower the population’s ability to survive and reproduce, a phenomenon called inbreeding depression. For example, a population of 40 adders (Vipera berus) experienced inbreeding depression when farming activities in Sweden isolated them from other adder populations.1 Higher proportions of stillborn and deformed offspring were born in the isolated population than in the larger populations. When researchers introduced adders from other populations—an example of outbreeding—the isolated population recovered and produced a higher proportion of viable offspring.
The explanation for inbreeding depression lies in the evolutionary history of the population. Over time, natural selection weeds deleterious alleles out of a population—when the dominant deleterious alleles are expressed, they lower the carrier’s fitness, and fewer copies wind up in the next generation. But recessive deleterious alleles are “hidden” from natural selection by their dominant non-deleterious counterparts. An individual carrying a single recessive deleterious allele will be healthy and can easily pass the deleterious allele into the next generation.
When the population is large, this is generally not a problem—the population may carry many recessive deleterious alleles, but they are rarely expressed. However, when the population becomes small, close relatives end up mating with one another, and those relatives likely carry the same recessive deleterious alleles. When the relatives mate, the offspring may inherit two copies of the same recessive deleterious allele and suffer the consequences of expressing the deleterious allele, as shown in the example below. In the case of the Swedish adders, that meant stillborn offspring and deformities.
For Swedish adders, the solution to the inbreeding depression problem was simple—introduce adders from other populations. But if the northern hairy-nosed wombat suffers from inbreeding depression, there are no other populations that can rescue it. Understanding the evolutionary history of a population and the likelihood that it carries recessive deleterious alleles, suggests that we should not allow population sizes to dip too low in our conservation efforts, or inbreeding depression may jeopardize the survival of the species.
1 Madsen, Thomas; Stille, Bo; Shine, Richard. Inbreeding depression in an isolated population of adders Vipera berus. In: Biological Conservation 1996. 75 (2): 113-118. "
This was quoted from :
Relevance of Evolution: Inbreeding Depression p. 1
As the article above stated, outbreeding is important to the prevention of inbreeding depression. In fact outbreeding is essential in diversifying the gene pool.
When breeding for morphs, some degree of inbreeding is necessary as stated here -- "A more common reason for inbreeding is the reproduction of various mutations, such as albinism. Such mutations can represent a large financial investment, as well as being of general interest to many, and there is much incentive to reproduce such individuals. There is absolutely no way to produce additional specimens of these rarities without inbreeding them to some degree. That's simply the reality of it. Each and every albino Burmese Python is in some way related to every other albino Burmese Python. That's just fact."
quoted from
The Learning Center - Inbreeding Discussion
As proven in the study of the adders mentioned above, outbreeding is necessary to prevent the 'weakening' caused by inbreeding depression. Responsible development of morphs SHOULD include introduction of unrelated snakes into the gene pool. An example of this would be this: assume the snake carrying the desired morph gene is a male, Breed him to 2 unrelated females of wildtype. This would create 2 clutches of 'hets'. These hets are then not related thru both mother and father, and are only related thru the father. Frequent outbreeding of the morphed animal(s) to wildtype normal animals would increase the available genetics and give you many different 'hets' to breed from.
"A method of primary importance is to utilize out-crossing wherever practicable. Out-crossing involves taking your cherished albino specimen and breeding it to two unrelated wild specimens. You'll now have two groups of heterozygous for albino specimens which are only half-related to breed together. This is much better than breeding the albino directly to his sister, as many new alleles will have been introduced into the population using this method.
Where possible, breeders should attempt to acquire specimens which are unrelated, or close to it, for use as breeders. The use of large groups of unrelated breeders will allow production of many unrelated or partially related offspring by making different pairings each year. "
quoted from
The Learning Center - Inbreeding Discussion
Proper record keeping is something that should be stressed among breeders and hobbyists alike (similiar to the way the dogs lineage are kept by the AKC). Then a breeder would have the records necessary to determine the 'relatedness' of animals and select the least related ones possible for the project. This is an undertaking that is almost impossible without universal support. But a universal registry has been started with cornsnakes located here
American Cornsnake Registry - Home . This registry is a giant step in the right direction, but it will take lobbying to the breeders from concerned individuals to make this a mandatory requirement.
