? on the flexibility of genetics - Page 1

trying to make a parrallel with dog breeding;

after the last drought when nearly all the surface water dried up and there were several pig breeding seasons without farm crops the only pigs that survived were small, wild, tough, vicous pigs with huge sharp cutters that could fight and were very aggressive.

this was the surviving gene pool. after the drought we had bumper crop seasons and the hogs got substantially bigger and the tusks got smaller and they became less aggressive.

 

conversely the wild dogs that were mainly fawn cloloured and extremely timid  became darker pigment, completely  less timid, bigger in size and started coming right up to people's houses and killing the pet dogs and eating them, sometimes in front of their hapless owners.

 

a narrowing of the gene pool to a few survivors would i have thought locked in type, apparently not, type rebounded quickly.

 

explanations on genetic grounds in terms of narrowing, bottle-necking etc?

 

your expectations may have been partially met given a stable environment. most simplistically, P = A + D + E + I  (Phenotype, Additive variation, Dominance variation, Environment, Interaction where Genotype = A + D. quantitatively, you can model that with differential equations or even structural equation models.; anecdotally, you can look at it as the genotype provides the building blocks and the environment shaping the observed expression(s) -- all within the constraints imposed by an organism's genetic possibilities. that's also captured in the heritability measures: broad-sense heritability, H²,  expresses the approximated phenotypic variation explained by genetic or other effects and is expressed as H² = V_G/V_P  where V_P is V_A + V_D + V_I + V_E +V_GE ; narrow-sense heritability, h², expresses the the additive genetic variation, A, to the total phenotypic variation, P. that is, h² = V_A/V_P .  have a look at: http://goo.gl/IECZ66, http://goo.gl/1zBIUH and http://goo.gl/T1NmpH as a rough 'n ready proxy for http://goo.gl/JJ2o8c .

Pete, Darwin mentioned something about survival of the fittest, it obvious that's what you witnessed. If the environment remained hostile for many decades or centuries, then the type would likely be 'fixed', much like the b/r gsd has been. In only a couple generations, the other genes are still there, to pop up when appropriate (ie, suitable environment).
Of course, this is just a dumb lay person's take on it, but seems to be the obvious without getting out the biology books.

Any way to tell if the 'wild dogs' (are we talking Dingoes, or something

else ?) that became bigger & darker & more agressive  were from

populations that had already interbred with domestic dogs ?  - or,

conversely, not ?