>>13769520I don't think they're going to be separate species; I think they'll actually just have different stat bases. Yes it's a first, but there's a lot of firsts this gen.
Of course, neither of our theories are confirmed, so we'll have to wait and see, but that's my take.
Also the bulbapedia link in my previous posts has a list of male/female counterpart Pokemon. You can check that for stat distributions; I haven't yet.