A model example of why genetic degradation happens and how organisms can be rescued (temporarily)
https://www.nordgen.org/en/genetic-rescue-norwegian-lundehund/
Excerpt: "Genetic rescue of Norwegian Lundehund
Several wild animal populations have received individuals from closely related populations to increase the probability of survival of threatened populations. Genetic rescue contributes to the conservation of endangered populations both by increasing the number of individuals and the genetic variation for future selection.
An article published in the Finnish Kennel Club’s magazine “Koiramme” (9/2016) describes the history, characteristics and challenges of the highly endangered lundehund population.
Several severe bottlenecks in the history of the Lundehund have resulted in a severe loss of genetic variability in the current lundehund population. Low fertility and high frequency predisposition to intestinal disorder IL (intestinal lymphangiectasia) imply inbreeding depression. The Norwegian Lundehund Club has initiated a cross-breeding project where three foreign breeds are introduced in the population.
The article describes the first experiences of the cross-breeding project and highlights the issues relevant for populations in similar situation:
Several wild animal populations have received individuals from closely related populations to increase the probability of survival of threatened populations. Genetic rescue contributes to the conservation of endangered populations both by increasing the number of individuals and the genetic variation for future selection.
An article published in the Finnish Kennel Club’s magazine “Koiramme” (9/2016) describes the history, characteristics and challenges of the highly endangered lundehund population.
Several severe bottlenecks in the history of the Lundehund have resulted in a severe loss of genetic variability in the current lundehund population. Low fertility and high frequency predisposition to intestinal disorder IL (intestinal lymphangiectasia) imply inbreeding depression. The Norwegian Lundehund Club has initiated a cross-breeding project where three foreign breeds are introduced in the population.
- When is the right time to pursue a genetic rescue via introduction of foreign breeds?
- How should phenotypic characters with possible negative effects on animal welfare be evaluated, and how should they affect breeding decisions?
THE ARTICLE DRAWS FOUR MAIN CONCLUSIONS:
- Cross-breeding gives a second chance for populations which are likely to become extinct; albeit with a cost of changing the genetic and phenotypic expression of the breed.
- Introduction of foreign breed(s) in reasonable time (relative to the amount of genetic variation and accumulation of genetic defects) allows us to reverse the detrimental development and rescue the population with fewer individuals introduced than if we wait until the genetic variation is fully depleted.
- Careful planning of cross-breeding followed by phenotypic selection enables the maintenance of the distinct characteristics of the Lundehund.
- Dog breeding programs should put more emphasis on the interaction between genetics, health and welfare both on the individual and population level."
My comment: Just in 200 years of intensive breeding of dogs has resulted in situation where several dog breeds need genetic rescue. Artificial selection of desired characteristics has led to rapid loss of biological information within dog breeds. At cellular level this means epigenetic amplification/silencing of epigenetic information patterns and it typically leads to strong rate of DNA mutations. This same phenomenon occurs in nature, but only slower.
There are synonyms for the term 'genetic degradation'. These are often used by evolutionary biologists.
There are synonyms for the term 'genetic degradation'. These are often used by evolutionary biologists.
- Population bottleneck
- Inbreeding depression
- Genetic rescue
- Genetic diseases
- Low genetic diversity
Dog breeds suffering from low genetic diversity can only be rescued by cross-breeding. For this to be successful, dog breeds having healthier genome have to be used. But at the level of the whole Canidae kind, the genome will at any case get degraded. That's why evolution is not happening.
