demographic parasite

demographic parasite (noun) dem· o· graph· ic par· a· site | \ˌde-mə-ˈgra-fik , ˌdē-mə- ˈper-ə-ˌsīt , ˈpa-rə- \

: A person, social group, community, nation, or broad grouping of people having common traditions, institutions, and collective activities and interests that resembles a biological parasite in living off of, being dependent on, or exploiting another social group while giving little or nothing in relation to the dynamic balance of a population especially with regard to density

A community which maintains its level of population without breeding from its inherent genetic stock is a demographic parasite which requires replenishment from other communities to do so.