relating to a species that is limited in its habitat to few, specific environmental conditions, or a parasite or pathogen to a specific host —note the term is usually used in reference to a species that occurs in a wetland or upland habitat; if the species is very likely (> 99 percent frequency) to be found in a wetland, it would be called an obligate wetland species; if the species is very likely (> 99 percent frequency) to be found in an upland, it would be called an obligate upland species —see facultative This definition last updated 07/21/2008