Alternative geographic models of speciation (Futuyma 1997)

    Geographic models of speciation emphasize the development of reproductive isolation between geographic population components of a species. (A) Allopatric: reproductive isolation develops between populations in physical isolation. (B) Founder Effect: reproductive isolation develops in a small population separated from the main body of the species, in consequence of the biology of small populations. (C) Parapatric: reproductive isolation develops among contiguous components of a population, in consequence of their limited vagility. (D) Sympatric: reproductive isolation develops within the "cruising range" of an existing species, in consequence of special biological properties (e.g., host-parasite specificity).