The importance of isolation is likewise great in preventing, after any physical change in the conditions, such as of climate, elevation of the land, etc., the immigration of better adapted organisms; and thus new places in the natural economy of the district will be left open to be filled up by the modification of the old inhabitants.
Isolamenduaren garrantzia ere era berean handia da hobeto moldaturiko organismoen inmigrazioa ekiditeko, baldintzetan aldaketa fisikoren bat gertatzen denean, hala nola, klimarena, lurraren gorakada, e.a.; eta horrela eskualdeko natur ekonomian leku berriak geratuko dira zabalik lehengo biztanleen eraldaketek bete ditzaten.