The Need For Genetic Diversity. - Page 3

Pod , you say the concept of a breed wouldnot occur in nature

please tell me what breeds have interracial offspring in nature

man made horse/donkey  , horse/zebra , sheep/goat  combinations , why dont they happen in the wild

man breed milksnakes to elaphe , why dont they happen in the wild

why is any elefant  phenotypical recognizable , as where he comes from , as are boa constrictors recognizable by colour and pattern , where they come from , but still one breed

none of this is underbuilding the outcrossing theory

I can't speak to this on the same level as many of you. The question that keeps nagging at me is this - considering the adversion in this breed to line and inbreeding, how can the breed not be gentically diverse? I'd have to wonder about the statistics presented here and ask exactly how they were generated. Did they only represent the Am lines where linebreeding is generally practiced and where all dogs seem to go back to Lance? The W German working and showlines where it is rarely practiced? Were the Czech dogs included?  The only trend I see that could possibly account for a decrease in genetic diversity is that many showline and workingline breeders use the same stud dog/s. The showlines seem to go for the dogs that do well at the Siegershau or NASS, the working lines for the dogs that score the highest in trials.  When you factor in the low percentage of linebreeding and the number of different "lines" available in this breed, it really puzzles me how there can be little genetic diversity.

Cross species breeding does happen occasionally in the wild but doesn't usually secure any selectional advantage, because the wider genetic difference produces outbreeding depression ie. the resultant offspring have difficulty fitting into either parental niche.  The examples you ask of though, all involve a domesticated species, so not really relevent to wild situations and you are proposing the pairing of two different species.  Very, very different from the breeding of two specific breeds together.   The equivilent of this in a wild situation would be breeding between distict popuations or groups of the same species.  A normal and practical practice for most species as far as I know.

You are right in that wild populations do tend to have rather restricted phenotype and this is down to the strong selection pressure excerted by their environment.  Eg any deviation from the strict regime in camouflage of a snake would be immediately evident to his prey and/or predator species.  He would soon be removed from the gene pool.  But don't be fooled into thinking that restricted phenotype equates to restricted diversity.  The genes controlling the visible qualities of an organism make up just a tiny proportion of the species genome.

The difference in our dog breeds is that they are no longer subject to natural selection and mutations that would spell disaster for a wild canid eg achondroplasia, brachycephalia, merle coat pattern, long coat, etc etc, have been embraced by dog breeders and inbred upon to create some of the modern breeds.

Wild animals too are losing diversity due to shrinking range and habitat.  Smaller populations and interference from man have changed the process of natural selection.     Man is the problem here, in the wild and with our domestic animals.

Just look at man hiself, all the sickness and cancers and defects.    As far as the dogs go we could add to the diversity easily enough if we were not in competition for this or that.    Changing man is the key.

JMO.

Could I ask Blitzen... which statistics you are referring to?

pod , you cannot compare GSD X Mali crossings to lets say wolf X wolf from another group crossing

wolf to wolf from another group is exactly what Im referring to in my first post on this topic

that would be an outcross of two inbred individuals , any breeding of the outcome of this mating , back to sire or dams line will be linebreeding again

this is also how it should be in domesticated breeds , only thats were us humans come in and screw up

inbreeding is not the problem , the selectioncriteria made by man are the problem

in nature , everything thats not sound in mind and body will not survive , and therefore will not reproduce

a limping wolf will not catch food and die

a limping auslese dog will be operated and bred many times

its that simple

Gee, is this starting to sound like American lines Shepherds, or am I imagining it??? 

The last two decades delivered a ‘show’ GSD at the upper limit of height and weight. Together with much criticism of top-line, over-stretched bodies, roached and sloping backs, bad fronts, elbows and cow hocks, unbalanced dogs displaying steep upper arms matched to over-angulated hindquarters. How do they gain top places even at a breed show? Because ‘typey’ dogs with roomy gaits seen side-ways and handled by experts impress!

Quote= pod:  you say the concept of a breed wouldnot occur in nature
please tell me what breeds have interracial offspring in nature

man made horse/donkey  , horse/zebra , sheep/goat  combinations , why dont they happen in the wild

man breed milksnakes to elaphe , why dont they happen in the wild

why is any elefant  phenotypical recognizable , as where he comes from , as are boa constrictors recognizable by colour and pattern , where they come from , but still one breed

none of this is underbuilding the outcrossing theory [/quote]

pod, you are confusing apples with oranges here! You are talking about crossing one species with another. Dogs are all ONE SPECIES. There are different BREEDS of that species. Inbreeding, or selective linebreeding narrows the gene pool yet again to a specific line within a breed. For example, crossing an American showlines Shepherd with a German showlines would be outbreeding. So would crossing a German showlines with a working lines GSD. Some people in the breed are so narrow-minded that they would regard these crosses as 'mongrels'.

Really, I do believe we have narrowed the gene pool too much. Does anyone have access to software where we could determine the coeffcient of inbreeding (COI) of our dogs?

pod , you cannot compare GSD X Mali crossings to lets say wolf X wolf from another group crossing

Any cross between dog breeds equates to outcross breeding in wolves from different populations.  There is obviously going to be various degrees of relatedness but they are breeding within their own species in contrast to the examples  you gave of horse/donkey, sheep/goat etc.  These are different species.

What would be an outcross of two inbred individuals , any breeding of the outcome of this mating , back to sire or dams line will be linebreeding again

Yes that's correct
 

this is also how it should be in domesticated breeds , only thats were us humans come in and screw up
inbreeding is not the problem , the selectioncriteria made by man are the problem

I agree to a certain extent but diminishing the gene pool by using the selection criteria of man is now thought to lead to health problems associated with inbreeding.

in nature , everything thats not sound in mind and body will not survive , and therefore will not reproduce

Absolutely.  And here we have the problem.  Without natural selection, the unfit individuals in dog breeds that would not have survived in the wild, become part of the gene pool in domestication and by inbreeding to these lines, the problems become fixed in the breeds.

pod, you are confusing apples with oranges here! You are talking about crossing one species with another. Dogs are all ONE SPECIES. There are different BREEDS of that species. Inbreeding, or selective linebreeding narrows the gene pool yet again to a specific line within a breed. For example, crossing an American showlines Shepherd with a German showlines would be outbreeding. So would crossing a German showlines with a working lines GSD. Some people in the breed are so narrow-minded that they would regard these crosses as 'mongrels'.

Can't disagree with you here Sunsilver.  It was duke's quote about crossing different species.

Really, I do believe we have narrowed the gene pool too much. Does anyone have access to software where we could determine the coeffcient of inbreeding (COI) of our dogs?

It would be interesting to have COIs going right back to breed foundation but I don't think there is software ready for that yet.