Fig. 1

Summary of basic ideas of ecological niche modeling. An ecological niche defined in two environmental dimensions (for simplicity of illustration) is shown in the lower left panel—gray points represent the broader “background” of environments, while the red rectangle indicates the hypothetical niche (termed A; E. Saupe et al., in preparation). The upper panel shows the global footprint of this niche, corresponding more or less to relatively mesic subtropical deserts. The area that is accessible to the species is termed M and is shown as a broken double line. The inset at the lower right then shows the portion of the broader footprint that is accessible to the species and that makes up its actual geographic distribution (were this to be a real species). Niche modeling would take known occurrences from the geographic distribution of the species, obtain their environmental values, and contrast environmental values of known occurrences with those of the background to produce a “niche model.” The niche model can then be used to probe broader areas, such as the whole world or such as conditions present in another time period, to estimate potential distributional areas