GAM-NICHE: Shape-Constrained GAMs to build Species Distribution Models under the ecological niche theory

This book provides a tutorial on how to use Shape-Constrained Generalized Additive Models (SC-GAMs) to build Species Distribution Models under the ecological niche theory framework (GAM-NICHE model), based on the development by Citores et al. (2020) Ecological Modelling 418: 108926. https://doi.org/10.1016/j.ecolmodel.2019.108926). SC-GAMs impose monotonicity and concavity constraints in the linear predictor of the Generalized Additive Models and avoid overfitting. SC-GAM is an effective alternative to fitting nonsymmetric parametric response curves, while retaining the unimodality constraint, required by ecological niche theory, for direct variables and limiting factors.