Three important concepts must be kept in mind when modelling species distribution: 1. The distinction between potential and realized distribution 2. The effect of the relative occurrence area of the species on the results of the evaluation of model performance and 3. The general inaccuracy of the predictions of the realized distribution provided by species distribution modelling methods. This paper mentions that different distribution modeling techniques should be used depending on whether the purpose is to determine potential vs realized distribution (Figure 1). Based on previous literature on a variety of species distribution models, the authors ask whether complex models tend to be more accurate then simpler techniques and this question comes into effect when considering a species potential vs. realized distribution (because realized is more context dependent and may require higher resolution data and therefore more complex). Sometimes when determining potential vs. realized distribution, different types of data, such as absence in addition to presence data will be needed, which can help to infer species exclusion because of an interaction with another species. It is also suspected that rarer species models are more accurate because presence data has more specific environmental associations. Thus, data type can also influence whether one thinks that complex provides better results that simpler models. Another issue can arise with the evaluation of model performance which can be biased towards a better performance of complex techniques due to their potential to overfit models of the training data. The performance of the models should be evaluated by examining errors of omission and commission separately and by taking into account the ratio between the extent of occurrence and the whole extent of the region of study. Overall, understanding which models to use requires a clear understanding of the question at hand and the type of data available/feasible to collect in addition to the species biology.
Fig. 1. An overview of suggested models depending on whether potential or realized species distribution is desired.
