In the human world, no means no, or at least it should. In the fish world, the female mosquitofish have been able to develop different sized and shaped genital openings when predators are nearby, and, get this, when they want to block male mosquitofish from different populations from trying to mate with them.
“Our lab previously showed that male mosquitofish have more bony and elongated genitalia when living among predators. When predators lurk nearby, male fish must attempt to copulate more frequently – and more hurriedly – with females. So females have evolved a way to make copulation more difficult for unwanted males.”
This evolutionary aspect of the female mosquitofish is what the researchers call the lock and key theory whereby certain males that the females don’t want to copulate with are unable to because the female essentially has different genitalia that the unwanted male cannot penetrate. This avoids such things as “hybridization with maladapted populations or other species.” The scientists say that the genitalia of the female mosquitofish evolves to reduce hybridization.