The distribution of a species is controlled by a number of biotic and abiotic factors–but also access to suitable areas for dispersal and/or evolutionary ability to adapt to new conditions. The relative contribution of these vary by species, but their importance may be related to geography.
To be able to assess the spatial variability of abiotic factors, researchers studied the distribution of the world's freshwater fishes, using a novel approach–an instability index–to examine and visualize the varying importance of different predictors. Using GBIF-mediated occurrences combined with several bioclimatic and topograhic variables, the authors modelled the distribution of each species in three progressively widening extents.
In their results, they find temperature and altitude to be the most important predictors at the river basin level. Expanding to the regional level, altitude is replaced by precipitation, which finally becomes the single most important predictor at the global level.
Suggesting that predictors depend on geographical scope, this study presents an important implication to be considered in species distribution modelling.