I don't mean to be rude, but that makes no sense at all. What you are effectively doing is making it so an ocean native species on an ocean planet can populate less of that planet than they could if they mixed in some arctic dwellers. Surely biome natives would be able to utilise a planet better than a mix of non-natives and natives could?
The ocean-dwellers can't effectively populate the polar ice caps. The arctic dwellers
can. By mixing the two, maximum utilization can take place.
It makes perfect sense, really. If you bring a load of only Kenyans to a new planet, they're going to have a great time in the parts of that new planet which are relatively like Kenya in environment; far to the north and south where it's cold and snowy, though, and they won't be so happy to live there. Buy you bring a boatload of Norwegians, Icelanders and Russians, and they'll have no problem colonizing that part of the world.
As an example (and apologies in advance if you have not played Kotor II), you have the Selkath from Manaan (a full on ocean world from what we see in the game) move to Kamino (another full ocean world). According to your Idea, they would need some wampa (uplifted by the rebel alliance to be used as empire bashers

) to utilise more of the planet. I can't see that working.
I am well acquainted with Selkath and Kamino. And frankly, Selkath would
hate living in the polar regions of Kamino. So would Mon Calamari. Native ice-dwellers, like Talz, would be far better equipped to do so. Thus, if you want to colonize Kamino, and you want to do it
fast, you bring one pop of Talz, one pop of Selkath, and one pop of Mon Calamari. The Selkath and the Mon Cal populate the oceans, and the Talz populate the ice caps. Bring some hyuuumans and maybe Twi'lek to boot, and you'll have the place at pop-cap in no time.