studied might invade in response to warmer temperatures. Cumutt (2000) used multiple 
discriminant analyses to identify connections between climate variables and plant distributions to 
predict plant invasions. 
Ecological niche models also are used to predict potential species invasions. Several 
assumptions are fundamental to these models: (1) a species’ distribution is limited by its 
ecological niche, and (2) a species can only disperse to an area with similar ecological 
characteristics (Peterson, 2003). One example of an ecological niche model is GARP (Genetic 
Algorithm for Rule-set Production), which can incorporate temperature as one of its 
environmental variables and has been used to predict invasive-species distributions (Kluza and 
McNyset, 2005; Peterson and Vieglais, 2001; Stockwell and Peters, 1999; Stockwell and Noble, 
1992). Since temperature can be included as a predictor of species distributions, GARP can be 
modified to reveal the influences of changing temperature over time. Authors of several studies 
have used GARP to examine the potential effects of climate change on the distribution of 
species, including those of the invasive Argentine ant and Limnopurna fortunei, a freshwater 
mussel native to southeast Asia (Kluza and McNyset, 2005; Roura-Pascual et al., 2004; Peterson 
et al., 2002; Peterson and Vieglais, 2001). Underwood et al. (2004) developed a model using 
GARP to predict the environmental niches of non-native species in Yosemite Valley, California, 
using parameters of elevation, slope, and vegetation structure. Results demonstrate the 
predictive potential of GARP for identifying potential invasion sites. The study concludes that 
similar models can be developed for other national parks and that such models may increase 
efficiency of field work and monitoring and decrease cost to managers (Underwood et al., 2004). 
Mechanistic approaches to modeling fundamental niches will provide additional 
predictive power to current models because these approaches identify how the characteristics that 
allow a species to survive (e.g., reproductive success, thermal tolerances, fitness requirements, 
and mechanisms for acquiring energy) interact with a species’ biophysical environment. By also 
integrating spatial and temporal climate information, these models can provide a better landscape 
view of the elements of a species’ fundamental niche as well as how species distribution and 
niche may change as climate changes. Climatic variables of specific niches may also be 
integrated into GIS maps to allow ecological managers to better visualize issues (Kearney and 
Porter, 2004; Porter et al., 2002). 
The studies discussed above illustrate the potential usefulness of a variety of modeling 
approaches in projecting potential invasive species distributions under climate change. 
Challenges remain in integrating climate-change projections and mechanisms of invasion, 
particularly in aquatic ecosystems and in translating model results into information useful to 
managers and decision-makers. 
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