This brings up another question. Say you have a pond that is at the edge of the Northern range of CNBG and the edge of the Southern range of Northern BG. Both will perform to their potential in your hypothetical pond. Which one do you stock? Is one more desirable than the other?
I'm going to hedge my bet by stocking northern strain. If the CNBG are at their northernmost limit, then an extended cold spell might spell their demise. The native BG will be fine in warmer water.
Plus, I'm not convinced CNBG will grow any larger than northern BG, given the same conditions.
