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The Scientific World Journal
Volume 2012, Article ID 428206, 10 pages
Research Article

Applying Fuzzy Logic to Comparative Distribution Modelling: A Case Study with Two Sympatric Amphibians

1Rui Nabeiro Biodiversity Chair, Centro de Investigação em Biodiversidade e Recursos Genéticos (CIBIO), Universidade de Évora, 7004-516 Évora, Portugal
2Division of Ecology and Evolution, Imperial College London, Silwood Park Campus, Ascot SL5 7PY, UK
3Laboratorio de Biogeografía, Diversidad y Conservación, Departamento de Biología Animal, Facultad de Ciencias, Universidad de Málaga, 29071 Málaga, Spain

Received 30 October 2011; Accepted 28 December 2011

Academic Editors: M. Baguette and B. Tóthmérész

Copyright © 2012 A. Márcia Barbosa and Raimundo Real. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We modelled the distributions of two toads (Bufo bufo and Epidalea calamita) in the Iberian Peninsula using the favourability function, which makes predictions directly comparable for different species and allows fuzzy logic operations to relate different models. The fuzzy intersection between individual models, representing favourability for the presence of both species simultaneously, was compared with another favourability model built on the presences shared by both species. The fuzzy union between individual models, representing favourability for the presence of any of the two species, was compared with another favourability model based on the presences of either or both of them. The fuzzy intersections between favourability for each species and the complementary of favourability for the other (corresponding to the logical operation “A and not B”) were compared with models of exclusive presence of one species versus the exclusive presence of the other. The results of modelling combined species data were highly similar to those of fuzzy logic operations between individual models, proving fuzzy logic and the favourability function valuable for comparative distribution modelling. We highlight several advantages of fuzzy logic over other forms of combining distribution models, including the possibility to combine multiple species models for management and conservation planning.