Sentence:  In the competition-dependent alternatives of a social insect colony or a lek, the frequency of dominant individuals need only be one to make subordinate alternatives more advantageous, and the frequency of dominant behavior may only vary between one (when the <WSD>superdominant</WSD> position of queen or harem chief is filled) and zero (when the position becomes vacant). 
Meaning of the word marked with <WSD> tags:  Holding a position of absolute dominance.