A minority of the members of the monster races refused the side effects that Crepuscule would create, so the new 'world' was created excluding them. Because of this, the monster population decreased in an instant, and the, mostly pureblood, first generation had to give up the racial purity of their offspring, in order to maintain their numbers in the new world. The majority of them mixed their blood with the other races. The blood of those races became obscured by the vampires' genetically strong blood. Though once distinct, the unique characteristics that every race had, became imperceptible. For this reason, the inhabitants of Crepuscule simply call themselves "vampires".
As the mixed-blood population increased in Crepuscule, the purity of the vampire blood diluted and the vampire powers deteriorated. Due to their peaceful lifestyle mixed-blood vampires became even more sensitive to their weaknesses. Sunlight, silver, flowing sacred water, and garlic have become their biggest fears. Very few families try to maintain their pureblood status nowadays with intermarriages inside their race.
There are many vampires in Crepuscule that can't even distinguish their affiliation.