The effects of introduced exotic species in natural environments are becoming important issues in conservation biology and natural resource management and recent scientific literature reveals increasing concern regarding the spread of invasive exotic plant species (Allen, 1996; Vitousek et al. 1996; Walker and Smith, 1997). Ecological consequences of these species include increased competition for space, water, and nutrients with native plants (which could result in a decrease in biodiversity), decreased forage quality for native ungulates, and changes in the microenvironments where the establishments took place (Woods, 1997). Sheley et al (1998) list several ecologically and economically detrimental impacts of exotic species. The National Park Service recognizes the need to protect ecosystems from exotic species (National Park Service, 1997) through management based on the ability to predict species distributions and spread, and monitoring in areas that are most susceptible to invasion. Recommended strategies for preventing the spread of exotic species include developing an early warning system to identify and eradicate new infestations of exotic plants in National Parks, and continued inventory and monitoring of exotic plants (National Park Service, 1997). These strategies will be based on assessment of the distribution and spread of exotic plants (National Park Service, 1997) using remote sensing and Geographic Information Systems (GIS) technologies for mapping and monitoring exotic plants, and models to predict the invasiveness and spread of exotic plants. In Grand Teton National Park (GTNP), exotic species are a great concern for park managers (National Park Service, 1997). Of the 1000 species of flowering plants within GTNP, there are also four (possibly five) rare plants that may be threatened as a result of competition with exotics (Wyoming Rare Plant Technical Committee, 1994): Draba borealis (Boreal draba), Epipactis gigantea (Giant helleborine), Lesquerella carinata var. carinata (Keeled bladderpod), Lesquerella paysonni (Payson's bladderpod), and possibly Draba densifolia var. apiculata (Rockcress draba). The continued survival of these sensitive plants in GTNP increases the need for management of exotic plants. GTNP has implemented a classification system for exotic plant species that consists of three priority levels (GTNP, 1997a). Priority 1 species are designated as "noxious" since they are capable of invading natural ecosystems and disrupting or displacing native vegetation. Currently, there are thirteen exotic plant species with a Priority 1 status within GTNP (Table 1 ).
Geographical Analysis of the Distribution and Spread of Exotic Plant Species in Grand Teton National Park, Wyoming
