Fundamental Interaction Niches: Towards a Functional Understanding of Ecological Networks' Resilience.

Global change will create new species interactions and alter or eliminate existing ones, a process known as interaction rewiring. This rewiring can significantly affect how ecosystems function. To better predict the future structure of ecological networks, assessing their ability to adapt to changes is crucial. Here, we introduce two concepts: 'rewiring capacity' of a single species (the multidimensional trait space of all its potential interaction partners within a region) and 'rewiring potential' of a local community (the total trait space covered by interaction partners of the species at the target trophic level locally). To quantify the rewiring capacity and potential, we apply existing methods for determining species' functional interaction niches in a novel way to assess species' and communities' ability to form new interactions and the functional resilience of interaction networks to global change. To illustrate the applicability of these concepts, we quantified the rewiring capacity and potential of interactions between 1002 flowering plant species and 318 hummingbird species across the Americas. The rewiring capacity and potential metrics offer a new way to understand and quantify network resilience, allowing us to map how ecological networks respond to global change.