Non-native Species 



Overview 



Introduced species evolved 

 elsewhere and have been 

 transported and purposefully or accidentally dis- 

 seminated by humans. Many synonyms are used 

 to describe these species: alien, exotic, non- 

 native, and nonindigenous. The spread of non- 

 native species during the last century has been 

 unprecedented in Earth's history, with the speed 

 and scale of these infestations more rapid than 

 natural invasions. The spread of non-native 

 species in human-disturbed habitats reflects a 

 deterioration of the North American landscape. 



Introduced species disrupt the functioning of 

 native ecosystems upon which humans depend. 

 Many non-native species become pests by 

 rapidly dispersing into communities in which 

 they have not evolved, and by displacing native 

 species because of evolutionary mismatches. 

 For example, non-native species contributed to 

 68% of the fish extinctions in the past 100 

 years, and the decline of 70% of the fish species 

 listed in the Endangered Species Act (Lassuy 

 1994). 



As several articles indicate, the economic 

 cost incuned because of non-native species 

 reaches millions, or even billions, of dollars. 

 Non-native species damage agricultural crops 

 and rangelands. contribute to the decline of 

 commercially important fishes, spread diseases 



that affect domestic animals and humans, and 

 disrupt vital ecosystem functions. 



Some species that have become pests were 

 first introduced to "create" a desired landscape; 

 these non-natives include exotic game animals, 

 fish, and decorative plants. Mack and 

 Thompson (1982). for example, traced the 

 widespread dissemination of 139 weedy, non- 

 native plants in the United States to seed cata- 

 logues and the commercial seed trade of the 

 19th century. Similarly, feral (wild) domestic 

 animals such as mustangs are a major problem 

 on public lands, and sound management of such 

 animals has been impeded by romantic images 

 of America's past. 



Accidental introductions through human 

 travel is a theme repeated in several articles, 

 indicating that cargo traffic (ship. air. land) is a 

 major vector of non-native species and should 

 be monitored as world trade increases. The 

 zebra mussel (Dreissena polymorpha) is the 

 most notorious hitchhiker, but introductions 

 through ballast water are not isolated to the 

 Laurentian Great Lakes. My colleagues and I 

 recently found that 1 1 exotic benthic inverte- 

 brates have become established in Oregon estu- 

 aries. Similarly, dinoflagellates causing red tide 

 toxins have spread into Australian waters 

 through cargo traffic. The importation of raw 



Science Editor 



Hiram W. Li 



National Biological 

 Service 



Oregon Cooperative 

 Fishery Research Unit 

 Oregon State University 



Corvallis, OR 97331 



