Metacommunity models and empirical data reveal asymmetric network-constrained fish dispersal

Borthagaray, A. I., Teixeira de Mello, F., & Arim, M. (2025). Inferring riverscape dispersal processes from fish biodiversity patterns. Journal of Animal Ecology. https://doi.org/10.1111/1365-2656.70033. Dispersal is one of the main determinants of biodiversity. Previous studies have pointed out that the diversity and composition of communities depend not only on dispersal rates, but also on the complex spatial networks formed by dispersal paths. However, going beyond this observation to infer a spatially explicit dispersal network for a particular system remains a challenge. Borthagaray et al. (2025) combined metacommunity models and empirical data from 58 fish communities to identify the most likely dispersal network in the large Negro River basin (Uruguay). They assessed the empirical support for alternative combinations of dispersal parameters (sources, (a)symmetry, distance decay, barriers). The best-supported combinations show that fish disperse asymmetrically along river branches; that is, dispersal is stronger downstream than upstream. Yet, the outlet remains an important source of upstream dispersers, even at large distances. Though they could not find evidence of any barrier effects of dams, this might be due to lagged responses to the induced fragmentation. By making the most of metacommunity models and empirical data, this study showcases an elegant way to infer complex dispersal patterns from empirical data, which could be advantageously replicated in other systems.