Come up with one (1) example of how two (2) sympatric species of Apis bees could potentially be prevented from successfully mating with each other in...

Come up with one (1) example of how two (2) sympatric species of Apis bees could potentially be prevented from successfully mating with each other in the wild. The mechanism could be behavioral, environmental, etc. - just no direct human intervention. Your example can be based on reality or be totally imaginary. Just make sure to explain how your answer would successfully contribute to reproductive isolation.