The importance of genetic diversity - Page 4

I think you got it the other way around. The working line dog breeders will be more likely to slit their wrists, before using a SL in their programs. We already have a select few "admitted" SL breeders who have crossed that line.

You are right Beetree....you probably get more resistance from WL people. I think it is because of the depth and breadth of the backmassing in show lines, makes them have a more concentrated influence, then what WL people want for balance. This isnt meant as critical, just a statement of fact.

Just want to clarify that I was using that as an example. I just as easily could have said wl x sl, American line x German, etc. I didn't mean to imply that showline people are more resistant to outcrossing than other breeders. There is resistance in EVERY line to violating what breeders see as the 'purity' of their breed type.

Gustav wrote "But overall, back massing is the most detrimental breeding practice in past 40 years for this breed."

What about the 70 years before that, when it was inevitable?  Discussion after discussion about "genetic diversity" has proven to me that some people will believe what they want, stick with their stance, regardless of the evidence before them.  There is NO scientific evidence that PROVES genetic diversity is critical to the fitness survival of a species.  In fact, "too much" causes genetic drift, or outbreeding depression.

What the heck is genetic drift and outbreeding depression? Sounds like a crock of houey.... these aren't wind pollinators! Junk, I tell you, LOL

That's because everyone just parrots off what's learned in gradeschool, "genetic diversity .... is GOOD, inbreeding is BAAAAD" blah blah.

Crock of houey is all the science you need to know.  Breeding is obviously more politics than science.

daryll has a point, most people repeat what was told in school or read on internet, to give an example, people talk about inbreedingdepression, but most people dont know after how many generations or with what inbreedingpercentage this actually kicks in, these are not actual figures in dogbreeding

Gustav , how many generations you think you can REALLY outcross before you are forced to start doubling up names on your pedigree, even if you dont want

close inbreeding as done by mother earthhttp://www.publish.csiro.au/paper/WR03007.htm 


if Im correct this closed population was based on three male animals without introduction of new blood in about 90 years

Nobody ever seems to discuss the importance of "genetic consistency" do they?  That explains more trouble with the breed than anything else could.  Frequently, the words "importance" and "diversity" are combined, and no one ever seems to get around to describing the HOW or WHY of diversity's "importance".  We're just told that it IS, and that's what we should believe.

This naturally leads to the belief that outcrossing is the solution to improving genetic diversity, which isn't necessarily so.  Outcrossing causes genetic drift, and outbreeding depression.  Fact of the matter is, inbreeding depression, homeostasis, heterosis, and outbreeding depression ALL occur on different traits in EACH individual produced.  And "backmassing" means nothing in scientific terms or in breeding, that I'm aware of.

Genetic drift is the change in allele frequencies due to random sampling (meaning, absent of "selection" pressures).  Breeding for the sake of outcrossing will actually REDUCE the level of genetic diversity in a population.  Genetic drift and selection are two simultaneous occuring forces of evolution.  SELECTION is the single greatest power of the breeder, and it's use determines the CONSISTENCY of his breeding.  If the PRESERVATION of a trait is the focus of a breeding, then selection MUST be the acting force.

Outbreeding depression may arise due to two different mechanisms.  First, outbreeding depression is usually attributed to genotype X environment interactions when populations are adapted to different environmental conditions.  The hybrid population will then contain genotypic combinations of alleles that may be less suited to either environment.

A more complex type of outbreeding depression occurs when different populations have evolved different coadapted gene complexes.  Coadapted gene complexes are groups of loci whose fitness depends on interactions between loci (epistatic interactions). Particular combinations of alleles at different loci are needed to produce favorable effects.  Recombination in hybrid populations produces new combinations of alleles that are deleterious.

if you can read a book and remember it, you can become a professor, but it dont mean you thought about what you have been reading, that you understand it or that it is even the factual truth

so I prefer to listen to those that have hands on experience, long time breeders of dogs , cattle, homing pigions and such  and find that nature is often not listening to the books,  even in my own 25 years of breeding seen things go against what is written by some

many people ,unfortunately only repeat what they heard without any hands on experience to underbuild what they are writing, but all together creating public opinion

people should read and remember a part of darylls previous post that the most important part about breeding is SELECTION, what animals do you choose to continue with, and as long as selection is mainly focussed on podium places instead of health and actual qualities, you are going nowhere, if we are mistaking agression and prey for determination and courage and stability, we are going the wrong way

here are some of mother earths creations, now think about how much genetic diversity they have in the individual animals, and I dare anyone to find me 5 closely related german shepherds that even come close to the similarity these animals have, so really how much more diversity do we want, both in looks and caracter/temperament

That is a good question, Duke. Commenting on the lack of dissimilarity in the zebra herd; they are like a school of fish...one raises his head and they ALL raise their head. Or one wheels and runs, they ALL wheel and run. A herd of zebra is akin to a two thousand legged animal with one brain. But that is perfect for their survival .....a zebra can be counted upon to eat, reproduce, run and fight like a posessed demon. But, even though they are close to horses genetically, there have only been a hand full that could be trained.. They aren't even suitable for domestication because the genetics are not malleable enough. I know what you meant using this pic for analogy, but too tight genetically and versatility is going to be absent, hence, the two thousands legs with one brain. BUT, I also know, from experience, what you mean regarding outcrossing. It can produce no uniformity in the litter and more unwanted physical traits than one would ever experience with line breeding using the same female.