Despite evidence that seasonal variation can lead to the persistence of competing species, seasonality has only recently become recognized as a main factor of biodiversity and community assembly. By observing changes to temporal species interaction networks, we can gain a better understanding of how seasonality influences the dynamics of species interactions in communities.
Species interactions temporally evolve as a result of two main processes: species turnover (i.e. species being present during different seasons), and interaction rewiring (i.e. different interactions between species over seasons). Identifying which of these processes lead to temporal differences is important as communities dominated by temporal rewiring may be more robust to perturbations that cause changes in species abundances and interactions over those dominated by species turnover.
Unfortunately, due to the dearth of biological data on community compositions, quantifying interaction networks is resource demanding. In addition, many species interaction networks are likely influenced by interactions not amenable to direct observation (e.g. through non-focal intermediate species via cascading effects). Hence, understanding the causes of temporal changes in the topology of interaction network structure requires further study.
Here, we investigated whether changes in network topology was the result of species turnover or interaction rewiring through the reconstruction and comparison of freshwater stream fish interaction networks for Spring and Fall. We applied a recently proposed method of network reconstruction that used species abundances to infer species interactions. Our dataset consisted of fish abundances of 39 species from nine National Ecological Observatory Network sampling locations, collected since 2016 in both Spring and Fall.
Results/Conclusions: We found that the greatest changes between the seasonal networks were the result of interaction rewiring (approx. 80%), compared to species turnover (approx. 20%). Furthermore, we found through a measure of modularity of the networks, that a significant portion of network rewiring was associated with species whose juvenile and adult life stages occurred in the Fall. This has important conservation implications as it suggests that species interaction networks undergo regular seasonal rewiring changes as a result of life history traits, which may make them more robust to future perturbations via the ability for interaction rewiring.