Combining competition with predation: drastic effect of Lasius fuliginosus (Latr.) on subordinate ant species at the northern limit of its distribution

During long-term field studies on division of space between the territorial ant species Lasius fuliginosus (Latr.) and Formica polyctena Först, in southern Finland a severe decrease in the abundance of subordinate ant species was observed within L. fuliginosus territory. As part of this study we analyze the extent of changes in subordinate ant species assemblage in the light of already documented cases of L. fuliginosus prédation on colonies of subordinate ants. The results showed that L. fuliginosus had a much stronger negative impact on co-occurring subordinate species, than the neighbouring rival F. polyctena. The hypothesis of hunger-induced myrmecophagy in this species is put forward, and is discussed as a possible competitive mechanism by which L. fuliginosus could shape ant assemblages within its territories.