Evaluation of hazards posed by alien organisms threatening native plants and communities using paired comparisons based on questionnaires answered by specialists(News)

Abstract

Many alien organisms (plant competitors, herbivorous animals, and host-specific parasites) are hazardous to endangered plants and important plant communities requiring conservation. Therefore, estimations of such hazards based on the biological traits of alien organisms are necessary; however, such information is not yet readily available. Despite technological deficits, we must immediately evaluate the hazards posed by alien organisms to plan countermeasures. Using paired comparisons based on questionnaires answered by specialists, we developed a method to evaluate the hazards of alien organisms that can damage native plants and communities. The knowledge of specific specialists was often limited to certain habitats (e.g., forest or wetland) and climatic zones (e.g., subtropical or boreal). Therefore, we constructed a table of paired comparisons using the answers from all specialists. Due to difficulties comparing the hazards of various alien species in diverse habitats, we first compared the importance of habitat (necessity of countermeasures) and then compared the hazard posed by individual alien species in each habitat. Hazards to native plant species through reproductive interference, hybridization, or host-specific parasitism were evaluated separately. Among habitats, vegetation on oceanic islands was the most important habitat in terms of hazards posed by alien species. Plant communities in aquatic systems and on oligotrophic sand and gravel along riversides were next most important.