Slitherine

See screenshot, where in my current game I have not researched 'atmospheric dome' but I can build it. Any idea why? Is it a bug?

[later] I see now that my race started the game with the ability to produce the domes. I think that the tech tree should then show that it's already researched.

the race you have chosen has it already, so not needed, once you try later on to add it, it will say already got and researched later on