The importance of territorial behavior in ecological networks

To eat or to be eaten-  that's not always what matters. The importance of non-trophic interactions, such as territorial behavior, in ecological networks, communities and ecosystem studies is dealt with in the new Early View paper "Territorial ants depress plant growth through cascading non-trophic effects in an alpine meadow" by Chuan Zhao and colleagues. Below, you find a summary of the study:

All species are embedded in ecological networks, which are composed of both trophic and non-trophic interactions.  Trophic interactions are well recognized as a major force structuring ecological communities and regulating ecosystem functions.  Meanwhile, although non-trophic territorial interactions between animals have long fascinated behavioral ecologists, their potentially cascading ecosystem-level effects have been largely overlooked.

In our manuscript, we provide one of the first demonstrations of a cascading effect of territorial interactions and, to our knowledge, the very first within the context of a detritus food web. Specifically, in a Tibetan alpine meadow, we experimentally investigated the non-trophic interaction between territorial ants and members of a dung decomposer community, as well as the ecosystem consequences of this interaction. We discovered that ants significantly decreased the abundance of coprophagous beetles and hence triggered a cascade whereby dung removal rates and soil nitrogen concentrations were reduced, ultimately decreasing aboveground plant biomass.

Our results show that animal territorial behavior, which is pervasive across animal taxa and ecosystems, can have strong cascading effects and therefore should be explicitly considered in models and experiments linking community structure and ecosystem functioning. Moreover, the results reveal a mechanism through which non-trophic interactions can link animals that do not otherwise interact through more widely studied forms (competition, predation or facilitation).