Delimiting the geographical background in species distribution modelling
Article first published online: 22 JUN 2012
© 2012 Blackwell Publishing Ltd
Journal of Biogeography
Volume 39, Issue 8, pages 1383–1390, August 2012
How to Cite
Acevedo, P., Jiménez-Valverde, A., Lobo, J. M. and Real, R. (2012), Delimiting the geographical background in species distribution modelling. Journal of Biogeography, 39: 1383–1390. doi: 10.1111/j.1365-2699.2012.02713.x
- Issue published online: 18 JUL 2012
- Article first published online: 22 JUN 2012
- environmental potential;
- geographical background;
- historical factors;
- species distribution models;
- trend surface analysis;
- ungulate distributions
Aim The extent of the study area (geographical background, GB) can strongly affect the results of species distribution models (SDMs), but as yet we lack objective and practicable criteria for delimiting the appropriate GB. We propose an approach to this problem using trend surface analysis (TSA) and provide an assessment of the effects of varying GB extent on the performance of SDMs for four species.
Location Mainland Spain.
Methods Using data for four well known wild ungulate species and different GBs delimited with a TSA, we assessed the effects of GB extent on the predictive performance of SDMs: specifically on model calibration (Miller’s statistic) and discrimination (area under the curve of the receiver operating characteristic plot, AUC; sensitivity and specificity), and on the tendency of the models to predict environmental potential when they are projected beyond their training area.
Results In the training area, discrimination significantly increased and calibration decreased as the GB was enlarged. In contrast, as GB was enlarged, both discriminatory power and calibration decreased when assessed in the core area of the species distributions. When models trained using small GBs were projected beyond their training area, they showed a tendency to predict higher environmental potential for the species than those models trained using large GBs.
Main conclusions By restricting GB extent using a geographical criterion, model performance in the core area of the species distribution can be significantly improved. Large GBs make models demonstrate high discriminatory power but are barely informative. By delimiting GB using a geographical criterion, the effect of historical events on model parameterization may be reduced. Thus purely environmental models are obtained that, when projected onto a new scenario, depict the potential distribution of the species. We therefore recommend the use of TSA in geographically delimiting the GB for use in SDMs.