Fig. 9.

Block cross-validated log-likelihood and cross-valid AUC for the species E. dives (higher is better). Pooling data from other sources gives a substantial boost to predictive performance when the presence–absence data set is small. Because E. dives occurs in the southwestern part of the study region, where the bias function has a relatively gentle gradient, the sampling bias plays a less vital role. In the right panel, the leftmost blue triangle (‘1 species: PA + PO’ with no PA data), we are fitting the thinned IPP model to PO data alone. This is the regression adjustment strategy discussed in the section Challenges for regression adjustment using presence-only data.