This question is about evolution.
So here is the situation, what if with the money and time, we took a species( can be from an ant to an elephant) and placed it in an environment that is best suited for its survival. Alright, now we divide that species in half(group a and group b) group a will be in environment ideal for its survival and group b will be placed into a new environment which will change its genetic makeup and over time become a new sub species. Now lets take group b and place it into an environment that is the same as group a and wait for group b to be just as well adapted as group a is. Now here is the question, will group a and b( now sharing similar genes again) be able to be considered the same species and be able to repopulate?