The importance of genetic diversity - Page 5

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.

Daryl, that statement shows HOW LITTLE you know about genetics!  Inbreeding depression has been proven to occur time and time again in plants and animals. The reason why you don't see it so much in small populations in the wild is that Nature is a ruthless selector. Only the fit survive, thus eliminating deleterious genes.

Here's an example of what happens:

Last week my good Canadian friend and were discussing inbreeding problems, etc. She proceeded to tell about a theory she heard from someone called the Happy Theory of something like that. It reminded of a breeding theory my trainer and mentor Anne-Marie and I had talked about; it is called the Determinant Pre- potency Theory. It has been around for a long time and I suppose most breeders have dreamed of it at one point in their career because it involves creating the perfect specimen. How it works is like this:

Somewhere in your breed you find the "Ultimate" stud dog; the one, which has it all in conformation, intelligence, temperament, the works. You then breed Mr. Ultimate to every bitch you can get your hands on and closely study which pairing produce the closest image to Mr. Ultimate, the phenotypes. From that point you take 4 of these combinations and you begin a completely saturated program of in-breeding only on these 4 dogs; father
to daughter, mother to son etc. For 5 generations you do this all the while only picking that which is the epitome of Mr. Ultimate, the phenotype, the rest you cull. Now you have to keep these puppies for at least a year to truly determine their potential and then you cull them. By the 5th generation you have all the good and more mportantly all the bad, you have brought to the surface every genetic defect these dogs carry. Still you continue to breed phenotype to phenotype and cull the rest. In theory, by the 7th generation, I think it is, you should have 2 dogs; a stud and a bitch that are exact replicas of Mr. Ultimate. They are your mutations, your Determinant Pre-potencies. You breed these two together and if the puppies survive at the 9th generation the dogs you produce should produce their exact image of Mr. Ultimate no matter what they are bred to. You have created your perfect line of dogs. The only glitch is that when you get to the 11th or 12th generation of outcrossing the Determinant Pre-potency lines you have to start all over again! It involves culling probably thousands of puppies, which even in theory is not acceptable to me. The years of dedication and money are immense and ultimately you end up right where you started. However, I am a sucker for theories!

Anne-Marie told me that she had heard of old-time breeders who did indeed tried to do this. She never heard of anyone being successful. What I have learned from rummaging around the net for this theory, and I haven't found it related to dogs, only lab mice. Is yep, it has been tried a lot, and by the 6th to 7th generations the mice are all basically phenotypes of Mouse #1, but they are born sterile and when taken out of their little sterile lab nests have little to no immune systems! What was noted prior to complete sterility is a lack of sex drive of both sexes; high incidence of auto immune related diseases, smaller number of mice born, lack of mothering skills, overt cannibalism...
 

I am convinced that the backmassing present in the showline dogs is one of the reasons GSD owners now consider any years after 10 'a gift'! When I got my start in the breed, I was told the average lifespan was about 12 years.
 

 

sunsilver that is  a big BS  hearsay story because that is nowhere close to reality, and if someone tries to breed like that it is just plain stupid, why do people allways make up stupid and over the top theories to prove their point, in wildlife and smart in/linebreeding in dogs there is an outcross every so many generations so the level of inbreeding you are talking about is not even close to reality, also sunsilver writes

By the 5th generation you have all the good and more mportantly all the bad, you have brought to the surface every genetic defect these dogs carry. 

another BS theory,yes, you brought genetic defects to the top, and SELECTED those without it to continue with,  first of all if you start linebreeding, you start with healthy material, and by the time you reached the fifth generation of your program , you had four generations of SELECTION, so you are past 95 % of any problems that were there to begin with

Duke, the theory is BS, that is very, very obvious. It's the part about the mice which is actual fact and the reason for my post. I've gone back and bolded it for those of you who might be having comprehension problems.

Daryl is saying there is NO SCIENTIFIC PROOF of inbreeding depression. And that, my friends, is, as Daryl puts it, 'a crock of hooey!'

BTW, I am not the author of the post I quoted about the Prepotency Theory. I found it elsewhere (don't recall where now) and saved it to my files.

again you prove my point I FOUND IT ELSWHERE, DONT RECALL WHERE

and can you provide the link of the factual reasurch about the mice

There is a TON of info out there on inbreeding depression in mice.

Here's one of the first articles I came across:

http://www.informatics.jax.org/greenbook/frames/frame9.shtml 

Inbreeding depression

The phenomenon of inbreeding depression has been witnessed in laboratory mammals for decades as evidenced by the extensive investigations with guinea pigs by Wright ( 1922). The mean value of characteristics associated with fitness in animals tends to decrease as inbreeding increases. The fitness characters affected by inbreeding in mice include: litter size ( Falconer, 1960b and earlier), body weight ( Falconer, 1960a), disease resistance ( Weir, 1960a), and lifespan ( Chai, 1959). For example, Falconer found that the average size of first litters decreased at a rate of 0.56 animals for each 10 per cent increase in the inbreeding coefficient. A decline was also found in lines where selection was practiced for an increase in litter size. The study demonstrated that part of the decline in litter size was due to inbreeding in the litters and part to the inbreeding of the dam. Subsequent work showed a difference between inbred and noninbred dams in preimplantation losses, but ovulation rate measured as number of corpora lutea was not affected by inbreeding ( Falconer and Roberts, 1960). McCarthy ( 1965) studied the physiological basis of heterosis of litter size in a study of four inbred strains and their crosses. He varied the inbreeding of the offspring and kept the dams inbred. The only significant difference in prenatal characteristics between incrosses and outcrosses was a significantly greater number of early postimplantation deaths (moles) in the incrosses. Inbreeding in this case, therefore, reduces litter size by acting through the dam to increase preimplantation loss and by acting through the embryo to increase early postimplantation mortality.

Decrease of litter size does not always result from increase in inbreeding. Falconer ( 1960b) found a few examples where inbreeding did not depress litter size. Weir and Schlager ( 1962) found no perceptible decrease in litter size in 25 generations of fullsib matings in a study of selection for leukocyte counts. That inbreeding depression is a real phenomenon, however, is emphatically demonstrated by the difficulties associated with the establishment and maintenance of inbred lines. Falconer found that only one line of an original 20 started could be maintained beyond an inbreeding coefficient of 99 per cent; 17 were lost at 76 per cent and two more after 80 per cent. On mathematical grounds Falconer ( 1960a) showed that the changes in gene frequencies during inbreeding are in the direction of increasing the number of recessive alleles being fixed. Generally the most probable cause of inbreeding depression is the fixation of deleterious recessive alleles normally masked and rendered ineffective by dominant alleles in a genetically heterogeneous population. For further discussion see Lerner ( 1954) and Mather ( 1955).  

  

How many more links would you like, Duke? And did you ever take a high school biology course?  You certainly wouldn't have passed the classes I taught!

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1212736/

http://www.informatics.jax.org/silver/chapters/3-2.shtml 

(This one is particularily interesting, as it talks about how inbreeding depression can be overcome by eliminating the deleterious alleles. However, this takes the sort of trial and error breeding that would likely be impossible in the dog world, because so many sick animals would be produced, it would create an ethical and financial problem for the breeder.)

http://www.astraean.com/borderwars/2012/01/those-inbred-lab-mice.html 


http://www.vortex9.org/reprints/inbreeding%20depression%20insular%20central.pdf 

Every single

 

Every single one of the highlighted sections of the above quoted paper provides a live link to another research paper on inbreeding, if you want more information.


Scientists (and farmers) have been aware of inbreeding depression for centuries. Even Charles Darwin wrote papers on it. Where have YOU been that you're not aware of this?

Arrrgh...better get out of here before I say something that will get me in trouble with the mods! I feel like I'm having a battle of wits with and unarmed man!


 

It is also a scientific fact that close inbreeding can lead to mental illnesses, health illnesses, and physical deformities or is that a myth too? @Duke......I would like to ask you what is your explanation for the condition of the SL today?

I also have never commented on the survival of a species or alluded to any breeding practices that affect the survival of a species. I have also made my comments in reference to domestic dogs in which breeding with faulty practices doesn't lead to extinction, but rather leads to an increase in mental , physical, and mental health issues. Therefore, I will butt out of this thread because I have far too little knowledge of the expanded subject matter to be useful.

@ gustav, my explanation is simple,bad selection of breeding material/breeding choices, falsified healthpapers, operated topwinners and so on

think of this Gustav, are the outcross bred showlines in better shape

Sunsilver, for every article you produce, I can present one claiming differently, it would be interesting to meet you in person for a day or two and talk about this, we could mirror my 25 plus years of close linebreeding and results to your schoolbook theories, because I can show for every generation I bred what choices I made, why and what the outcomes where, im setting up my breeding of GSD the same way, but it will take a little more time as my second generation is just 18 months now

nowhere you will find inbreeding for 7 generations or more to produce the depression you are talking about other than test breedings in labs and such, so this dont applie to dogbreeding at all, secondly, ive seen more of those articles, some say 7 generations, some say 12 and some say 20 generations, others speak of minimum of 65 % of inbreeding before depression kicks in, but again these are not realistic to mirror them to any dogbreedingprogram


we once got a dog from the USA who turned out to be affected with PRA, in two generations we bred full litters of PRA free dogs from her, so please tell me where we cannot breed out genetic defects, we did so with other common diseases in our dogs , producing full litters of healthy linebred dogs, tested on all common defects in the breed and all healthy


if you outcross you will only HIDE the genetic defects as much as possible but will NEVER get rid of them, as you dont know if they are there or not, and they will possibly pop up with every new generation you breed,

also will give you something else to think about, if you breed a certain combination, the genetic buildup on each pup/mause/ or whatever animal will be different, this will be so in ever following generation, so the outcome of any testbreedingprogram would be different for every individual pup/combination and can come out very differently ,  which male on which female and so on, so any outcome would be very hard to reflect on any other breeding program