Variation of interspecific interactions at different ecological levels within an assemblage of Arctic marine predators

International audienceHow interspecific interactions change across scales is poorly known. Such knowledge might help us understand how species interact within communities and highlight scale-dependent ecological processes in play among species. Here, I propose to analyze the inter-annual variation of a species assemblage at different ecological levels. For this, I joined a two-stage modeling approach and a spatially explicit multivariate model to analyze the interspecies relationships among six species of pelagic seabirds from 2004 to 2015 in the Barents Sea. The large-scale (~400 km) pattern of interactions revealed by the analyses suggests a change in the composition of the seabird community along the climatic gradient from south to north. At medium-scale (~300 km), the community was split into two areas (i.e., Arctic and sub-Arctic areas) suggesting niche differentiation of Arctic and sub-Arctic species driven by resource partitioning and interference competition. At a small-scale (~40 km), species with different body sizes were positively associated suggesting facilitation for accessing food although the species with the smallest body size was negatively associated with the species involved in the facilitation process suggesting interspecific interference competition. Over the years, the large-scale patterns were persistent, suggesting niche establishment, while small-scale patterns were highly variable suggesting only ephemeral interactions among species. My study demonstrates that interspecific relationships are scale-dependent and play major roles in structuring community. Untangling how species are associated with different ecological levels over time is indispensable to better understand how community structure contributes to ecological system dynamics