Hybrids?

[Tony]

Mixed breeds of dog, and mixed breeds of cat, not cat and dog together!

You are comparing man-made varieties to wild forms that have evolved over many thousands of years or more in response to the unique selective pressures of their environments. It is an apples and oranges argument.

Some folks seem to think that keeping two varieties of D. tinctorious (for example) from different sides of a river seperate, because one has leg stripes and the other has leg spots, has some significance in this life and should be observed at all cost.

If those two forms of tinctorius represent distinct populations in the wild, then they absolutely should be kept separate in captivity. It has nothing to do with the phenotype, some populations are polymorphic but interbreed freely like Bastimentos Island pumilio, and some populations that are widely separated in nature express similar phenotypes like the various green and black auratus. What is important is maintaining the genetic integrity of our captive populations, if they don't interbreed in nature then they should not be interbred in captivity. It doesn't matter if YOU think a particular barrier to gene flow appears significant or not, if that barrier is enough to segregate two distinct wild populations it doesn't matter how small it seems.