I would say immigration only.
emigration would theoretically reduce the genetic variation as unique individuals leave, but immigration would bring unique traits into circulation in an ecosystem.
I'm not super great at biogy tho so this might not be right... :)
50%x 4842 because of you in your account number and you are now in 48525
The correct choice is the third movement of continents
THIS TYPE OF RELATIONSHIP IS CALLED "COMMENSALISM"