Pedigree Query

On page 188 of the Finochio hates Phalaris thread under Racing, Diomed linked a very interesting discussion of inbreeding depression and outcrossing depression in salmon. See link below. It brought to mind things I have read referring to the 4th, 5th and 6th generations as the engine room of the thoroughbred pedigree, where it is desirable to duplicate important ancestors. The cited article would seem to support the engine room theory as a means of avoiding both inbreeding and outcrossing depression. I was just wondering what you all thought of the engine room theory in general, whether gender balancing in the engine room is important, and, if the theory has any merit, whether duplications of more than one important ancestor is more or less helpful than multiple duplications of a single ancestor.


http://www.nwfsc.noaa.gov/publications/ ... lynch.html

While the folks who wrote the paper were doing good science, you have to be a bit careful when applying critters as different as horses and salmon.

The reproductive strategies are very different. Salmon lay hundreds of eggs, with low survival. Not that many fry reach the sea from any clutch. The survival rate of hatchery fry seems to be higher, and in fact fish that would have been selected against in the wild may survive to breed. Especially as hatcheries collect eggs and spawn from fish early in the run, not fish that have made the trip from the sea up river and to the mountain streams.

Horses have a very different reproductive strategy. Heavy selection on the male side, both with domestic and feral populations, and the mare producing only one foal at a time with a limited number of foals.

Generational time is also very different.

Thanks for posting the article, very interesting.