Geography 1301 - Smith, Keith: Physical Geography: Definitions

An exotic species is one that has been introduced to a geographic region and a biological community wherein it never before existed. Such introductions are often due to purposeful or inadvertent transport of species by humans from one continent or island to another. Because exotic species and native species have no prior evolutionary history, exotic predators and diseases can cause population decline and even extinction of native species that lack evolved defences (e.g., smallpox effect on native American populations, effect of pigs on Pacific island bird populations). Exotic species may have no natural enemies in their new environment, and may out-compete similar native species that are limited by natural enemies (e.g., kudzu introduced to the USA). Exotic species may eliminate native species, disrupting ecological relationships (e.g. food webs) and altering natural communities and ecosystems.