If by array, you mean this: Then it's just an index of species for players + NPCs. The first thing to do when making a custom race mod is to add that race's keyword to that species selection so the game can reference it, or else you won't get awful far.
Is that so? That's interesting, then-- maybe that necessity was patched out some time ago, because all the race mods that I've taken apart always have their species keyword(s) patched into this array. It could just be a leftover, if so, or some other form of race-related reference that's no longer required..
i haven't done a race mod, so I can only guess. Perhaps that is where it looks to see which races would make comments when looking at things. I've noticed crew members read the descriptions about things while passing, depending on their species. Or maybe it isn't really used anymore. Sometimes I put in something, thinking I'll use it. Then the code goes another direction and i don't use it.
I know that's where they are. But I wasn't sure what causes Starbound to even LOOK for them, per a given species. But my guess is only that. I don't actually know.