Dehling, D. M.; Lai, H. R.; Stouffer, D. B.

There is currently a dichotomy in the modelling of Grinnellian vs. Eltonian niches. Despite similar underlying data, Grinnellian niches are commonly modelled with species-distribution models (SDMs), Eltonian niches are modelled with ecological-network analysis. This separation stems from the much sparser data on species interactions, which has prevented the application of SDMs to Eltonian niches. Recently developed joint hierarchical niche models (JHNMs), however, overcome sparsity and improve predictions for individual species by considering non-independent relationships among co-occurring species. This unique ability makes JHNMs particularly suited for sparse datasets, such as ecological networks. Here, we propose to apply JHNMs to data on ecological networks, functional traits, and phylogenies to model species\' Eltonian niches and exemplify the approach for frugivorous birds. Moreover, we demonstrate that JHNMs can even be used to predict interactions of species for which no empirical interaction data are available--solely based on their functional traits. This facilitates the prediction of new interactions in communities with altered composition, e.g. following climate-change induced local extinctions or species introductions. The high interpretability of our Eltonian JHNMs will provide unique insights into the mechanisms underlying species interactions and the potential impact of environmental changes and invasive species on species interactions in ecological communities.