Species are the core unit of communities, yet species have a set of characteristics, called traits, that define their life cycle, way of eating, and movement capacity among many others. Traits allow us to look at the functions that species might be doing in habitats. Yet, we have mainly focused on how species presence and abundance shift across landscapes or over time, leaving these functional aspects slightly less studied. Yet, if species change, we should expect that func-tions will change too. We decided to further deepen on these by using species’ traits to under-stand what regional drivers might be relevant for their assembly. For example, while environ-mental conditions might favor species with certain group of traits it can also be that dispersal allows species to spread between sites despite environmental differences.

To explore these questions, we built networks based on how different traits were co-occurring across different lakes and streams from Sweden. This network approach allowed us to study how functional complexity may shift across space and/or over time. To cover these scales we pooled communities following different gradients: 1) geographical distance (i.e., close communities are pooled together), environmental similarity (i.e., similar communities are pooled together), and random. In each addition, we built a new network to see how its density (e.g., nº of links) was changing along the three gradients.

Interestingly, the way in which density was increasing along each gradient differed between habitats. Indeed, when pooling communities following geographical distance or environmental similarity we saw that density increased less than when being pooled randomly. This was the case of lakes, indicating that for these ecosystems these two gradients were structuring functional complexity from local to regional scales. Contrastingly, streams seemed to respond only to geographic distance, meaning that only space was favoring more functionally similar communities. These results show that functional structure is not fixed but reorganizes differently depending on ecosystem type and across scales. Because lakes and streams are shaped by different combinations of spatial and environmental drivers, conservation and restoration strategies should be tailored accordingly.

Equisuany, A., Cunillera‐Montcusí, D., Angeler, D.G., Antón‐Pardo, M., Boix, D., Cañedo‐Argüelles, M., Horváth, Z., Johnson, R.K. & Gascón, S. 2026. Trait co‐occurrence networks reveal changes in community functional structure from local to landscape scales. Funct. Ecol. : 1365-2435.70489. DOI: https://doi.org/10.1111/1365-2435.70489