As joe said for me the main thing is to keep good records of breeding crosses and all the other information you can get and believe on any group of snakes.
With most of the animals that we work with the approach is pretty simple. Get as large a group of as diverse as you can get that are representative of the animals you know from your experience or study to represent that specific locale of animals.
As far as what makes a locale to us it means a group of animals that are as closely collectted in the original animals as can be, with the deciding factor being that they must have the physical characteristics that make they diferent. For example Pandale Dirt alterna as versus Black Gap. Sometimes that will be a mountain range, sometimes a specfic mountain or canyon, sometimes it will be a county, sometimes it will be a specific road and other times it may be an entire state depending on the physical characteristics we are looking at.
That goes for Mexicana, pituophis or whatever it may be. To use the favorite dodge that the breeding group in the USA is very small and that they are all related in one way or another is a suppostition we don't use as in most cases they are ways around it if you try hard enough.
I have for instance a few of Dan's bloodlines and trust him completely, I also have several other breeders lines that I personally know or knew in the case of a couple that were involved back when the importations were brought in. And yes with thayeri I have a few animals that are from confiscations at the border(ie: The Laredo line we breed) and outright circumvention of the laws from people like Mickey Jacobs that used to bring in reptiles and red leg tarantulas back in the late 70's and early 80's. He was a competitor of mine back in the days of Gulf Coast Reptile & Animal Wholesale. Mickey while an outlaw supplied the hobby with a pretty good group of animals that few people ever talk about as they were not brought in with papers.
Just some thoughts, it does not make it right or even desirable but is just what we believe and try to do.
John Cherry
Cherryville Farms