Mixing population types?

[wickedsick]

Let's say your race is O2 breathers, and you capture a population of CO2 breathers.

What happens if you bring the CO2 breathers to an O2 planet?

I thought I read somewhere that this will cause the planet to be domed, but what happens to the facilities then? If you had 20/20 facilities built, wouldn't doming reduce the build space to only 4? So would 16 of your facilities just disappear?