Table 1.

Effects of failure to include species interactions in models of species potential distributions in an introduced range.

	Model built based on native range 1
Potential introduced range	Interacting species 2
Interacting species	Present; not used as predictors	Absent or excluded from model
Absent	Cell 1. PREDICTED RANGE TOO NARROW [enemy release/empty niche]	Cell 2. ACCURATE PREDICTION
Same or functionally similar to those in native range	Cell 3. ACCURATE PREDICTION	Cell 4. PREDICTED RANGE TOO BROAD [biotic resistance]
Functionally dissimilar to those in native range	Cell 5. PREDICTED RANGE TOO BROAD OR TOO NARROW	Cell 6. PREDICTED RANGE TOO BROAD [biotic resistance]

¹Environmental niche models are assumed to be predictive, correlative models based on conditions in the native range that are used to predict distributions in the introduced range.

²Interacting species (e.g., predators, parasites, competitors) are assumed to constrain the focal species to a realized niche that is narrower than its fundamental (pre-interactive) niche. A similarly structured table could be made assuming interacting species that render the realized niche broader than the fundamental niche (e.g., mutualists, ecosystem engineers); however, deviation of predicted from actual introduced ranges would likely be reversed.