Increasing reality of species distribution models of consumers by including its food resources

Abstract

Species distribution models are not usually calibrated with biotic predictors. Our study question is: does the use of biotic predictors matter in predicting species distribution? We aim to assess the importance of biotic predictors in the output of distribution models of the Brazilian squirrel (Sciurus aestuans) throughout South America based on fruits of Syagrus romanzoffiana – the most consumed food resource. We hypothesized that the distribution model of S. aestuans using its main food resource as a biotic predictor will be more accurate in comparison with the output of the model without the biotic predictor. We built three different distribution models: (i) distribution of S. romanzoffiana; (ii) distribution of S. aestuans without biotic predictor; and (iii) distribution of S. aestuans with biotic predictor. We evaluated performance scores, number of presence pixels and concordance between suitability maps. We found that performance scores may not vary between models with different predictors, but the output map changed significantly. We also found that models with biotic predictors seem to vary less in presence pixels. Furthermore, the main variable in the distribution model was the biotic variable. We conclude that the knowledge of a species’ biology and ecology can make better predictions of species distribution models mainly by avoiding commission errors.