Re: [PyrNet-L] gene pool size (was size)

[Kshoffman@aol.com]

JGentzel@aol.com wrote:

> Mrs. Crane registered over 60 dogs from all over Europe, but all over
> France primarily.  She reportedly imported over a 100 from Europe.
> Small gene pool was never a problem in Pyrs.

On the other hand .... 

magicm@ameritech.net wrote:

> Mary Crane did import a great many dogs, but if you take those dogs back
>  to the french register you will find they are from a very limited gene
>  pool. There are few places on my pedigrees where I can't get them all
>  back to that original register and one is very surprised how limited it
>  can be.

This is an interesting contrast in observations to me.  Joe, if a small gene 
pool was never a problem in the breed here, then I'm curious about something 
that you (or Lisa or perhaps someone else) may be able to answer. Based on my 
own informal observations/analysis of data and also conversations with others 
who've been around longer than I have and are better versed on breed history, 
I was under the impression that the *effective* number of founders (from a 
population genetics standpoint) for the breed in this country amounted to 
less than a dozen dogs, maybe only seven or eight dogs. That said, compared 
to some breeds' founding events, 7-12 founders is ALOT!!!!

I'm aware, Joe, that you have a fairly extensive CompuPed database of Pyrs 
and vast historical knowledge of the breed, so I'm wondering if perhaps you 
can give an accurate statistic or make a fairly educated guess as to the 
*actual* number of unique founders the breed population in this country was 
established from?  Guess I'll pose the same question to Lisa: What is your 
assessment based on the database you have?

I would also assume there was some sort of "genetic bottleneck" in Europe 
(and possibly in the US as well) around the time of WWII. Assuming this is 
correct, can either of you (or anyone else) perhaps give an idea as to the 
effective number of breeding dogs that might be represented at that 
bottleneck?  Possibly there have even been other such "bottlenecks" within 
the breeding population at different times in history -- does any timeframe 
or event in particular come to mind that either of you are aware of that 
would have restricted the gene pool in such a manner that virtually all of 
our current dogs are descended from such an "event" that would have resulted 
in a very limited pool of breeding stock?

Joe, you mentioned "the most talented breeder in the history of the breed in 
North America" and I'm wondering if perhaps the breeding activities during 
that kennel's most successful years may well come close to constituting a 
bottleneck of sorts for the breed???  Right off the top of my head I think of 
a couple of dogs used to establish a successful breeding program in the late 
60's that remained quite prominent throughout the seventies and beyond that I 
would imagine only a tiny percentage of our current gene pool is not 
descended from.

Also, how genetically diverse was the original founding population in the US 
really? (In terms of relatedness versus genetic distance within that pool of 
original foundation stock.)  My recollection from readings is that Mrs. Crane 
took great care to import a very diverse group of specimens from as many 
representative lines as possible and this included both "dogs of the 
mountains" (primarily working dogs of peasant farmers) and dogs of the 
original early "show" lines, but if all these dogs go back to a very small 
number of common founding dogs, were these specimens that Mrs. Crane imported 
indeed a genetically diverse group of distantly related dogs, or were they 
all more or less rather closely related?

Thanks in advance to anyone who cares to offer their opinions on this (or 
solid data would be even better!!!) I would happily do the data analysis and 
number crunching to arrive at the answers to these questions myself if I had 
a more complete database, but my database doesn't go that far back and I 
suspect both yours and Lisa's are much more complete than mine. I'd really 
like to find a way to do an in depth study of our current breeding population 
and get at the answers to these types of questions. The more I read about 
recent scientific studies and research that is the result of advancements in 
molecular biology and genetics in the past few years, the more inclined I am 
to believe that heterosis and genetic distance between mates (as opposed to 
homozygosity and relatedness - the end result of generations of 
"linebreeding") will generally yield healthier longer-lived dogs with a lower 
incidence of genetic health defects.  Because of this, I'm very seriously 
leaning towards a BIG change in the way I breed dogs.  Whereas in the past 
I've pretty much stuck with the tried and true method of "linebreeding" with 
the occasional outcross thrown in to achieve my objectives (as taught to me 
by my mentors and as outlined in most of the classic books on dog breeding 
and animal husbandry), I'm now more inclined to construct breedings between 
mates that are as distantly related and as far removed from each other 
genetically as possible with the lowest inbreeding coefficient I can achieve 
within reason.  This of course would not be my *only* breeding criteria, but 
something I'd like to strive for in addition to considering overall health, 
longevity, temperament, type and structure, as well as whether or not 
proposed mates are phenotypically complimentary to each other.  I have to 
wonder if avoidance of linebreeding on its own merit may well be a key for 
those who wish to increase overall size.  Recent genetic research certainly 
suggests that inbreeding depression is more than just theory and very much a 
reality. Reduced size is often mentioned by geneticists as one of the signs 
of inbreeding depression.

Kelley Hoffman
kshoffman@aol.com