If you picked Yor as your species, its possible to acquire non Yor citizens through planet invasion. They will demand food. If you can't provide, they will be unhappy. If you can't build farming districts, you might not be able to fix this.

I also found it possible to pick the synthetic trait and yet pick non Yor species as your species. For instance, you pick synthetic and use Mimot as your species. You will not be able to build any food districts, so its probable that your Mimot citizens will be very miserable over food shortages.

Some better population management tools would be nice. The current needs (I can think of at the moment) include the ability for synthetic populations to make food (since they often capture worlds full of hungry citizens), some way to get rid of Festron (even if their tendency to murder other species doesn't do much since they replace them), and some way to get population growth on planets that don't have citizens or is has only citizens that don't breed.