Individuals crossing exclusively within the same population produce more progeny than those crossing in both directions and thereby use up some of their gametes for the production of inviable hybrids.
完全在同一种群内进行杂交的个体比以两个方向进行杂交的个体繁殖后代要多,因此了产生无生机的杂种,就要消耗掉一些配子。