Elaborating on the "jungle skills" idea: how about making it simply "has adapted to terrain X"? This could mean, for example, that such civ gets a +N bonus (preferrably settable in the editor) of food/trade/shields when working tiles of the given terrain.
With this you could create civs like Dwarves (mountains +2 food), Elves (forest +1 food), Nomads (desert/plains), etc. Of course, when the AI plays such civ the "adapted to terrain X" should also mean that X is preferred when placing cities and transforming terrain types.