When one competitor species eliminates another competitor from the habitat, it is called

When one competitor species eliminates another competitor from the habitat, it is called competitive exclusion.  
There is a principle called the competitive exclusion principle or Gause's law referring to the relationship between two species competing for the same limiting resource which cannot coexist. The minimal advantage of one species will dominate and lead either to the extinction of the weaker competitor or to an evolutionary shift toward a different ecological niche.