That would never happen with Cyclura or Komodos, both of this animals evolved in tropical ecossystems free of large mamalian predators and competitors. And your not separating invasive from non native. Both in no circunstances would become a invasive, they are slow breeding, late maturing animals adapted to live in completly diferent envioroments. Mix them with cougars, bears, coyotes, cold, etc, dead in a matter of weeks, even the biggest lizard alive doesant stand a chance.