A Trophic and Non-Trophic Seasonal Interaction Network Reveals Potential Management Units and Functionally Important Species

Aim

Understanding the organisation of the wide variety of ecological interactions is crucial to advancing our understanding and management of real ecosystems. We aimed to compile a ‘complete’ network of tetrapod trophic and non-trophic interactions for the entire North American boreal forest biome that could be analysed to gain insights into community organisation and function. In particular, we aimed to identify functionally important units (modules) and species within the boreal network, and to compare how these changed seasonally and with different types of ecological interactions.

Location

Boreal North America.

Time Period

1950–present.

Major Taxa Studied

Tetrapods.

Methods

We compiled published ecological interactions for boreal tetrapods into a food web (trophic interactions) and a network containing trophic and non-trophic interactions (‘inclusive network’). We partitioned interactions by season, creating four networks representing the two network types per season. We examined how the modular structure, composition of modules, assortativity of species' attributes within modules and importance of different species compared across these networks.

Results

We compiled a dataset of 5037 ecological interactions amongst 421 boreal tetrapod species. Most of these interactions (87%) occur in summer. The summer and winter boreal food webs and inclusive networks are modular (i.e., contain subsets of species interacting more with each other than with species outside of the subset). The winter networks have more modules than the summer networks. Several species attributes explain which species assort together into modules, including physical and behavioural traits, taxonomic class and trophic niche. Seven species were functionally important across at least two of three measures: module hubs, centrality or responsible for the greatest network changes, with other species being important within certain seasons or interaction contexts.

Main Conclusions

Potential conservation management units (modules) exist in the boreal network, and module membership likely indicates tighter dynamic coupling in winter than in summer.