I am trying to model the distribution of some vascular plant species, the species with restricted ranges typically produce models with good (>0.7) AUC scores. Species which are more widespread distribution are giving poor AUC scores, I am not sure whether there is a way to improve this other than increasing the size of the study area so the models will better distinguish presences from background pixels (but this is not biologically significant). Any suggestions on how to evaluate the accuracy on such models or improve their AUC scores.