Cross breeding, need help.

[Stefan-A]

If all the various subspecies of Thamnophis sirtalis are indeed the same species, then there really shouldn't be an issue with breeding (even if it has to be done artificially) say, a s.f. garter with a concinnus or ca red-sided?

Not really, the same problems with keeping track of those hybrids would still exist even if physical problems, such as reduced viability, would be less likely to occur.

I don't try to speak for everybody, but it probably matters to most of us what we have. You don't really see any of us here intentionally breeding animals to each other simply based on species. Most, if not all, seem to want to make sure that their snakes only mate with individuals of the same subspecies. Personally, I wouldn't even consider buying a garter, if I didn't know its subspecies with a some amount of certainty. I've made that mistake in the past and I'm glad those snakes never reproduced. As far as I'm concerned (and I want to stress that this is only an opinion), hybrids, whether they're between species or within a species, are only good as feeders.