Lasius fuliginosus (Hymenoptera: Formicidae) shapes local ant assemblages

Interspecific competition is a major structuring force in ant assemblages. The assemblages are organized hierarchically, with territorial species as top competitors. In boreal areas and in the temperate deciduous forest biome common territorials are species of the subgenus Formica s. str. They are well known for their negative impact on lower-ranked ant species. Less is known, though the structuring role of Lasius fuliginosus, another territorial ant species. Some earlier studies have shown or suggested that it may restrictively affect subordinate species (including direct predation toward them) even stronger than wood ants do. In the present study we compared species compositions and nest densities of subordinate ant species within and outside territories of L. filiginosus. The results obtained confirmed that this species visibly impoverishes both qualitatively (reduced species richness, altered dominance structures) and quantitatively (decreased nest densities) ant assemblages within its territories. Furthermore, contrary to what is known in wood ants, there was not detected any noticeable protective effect of L. filliginosus for Formica fusca living within the L. fuliginosus territory against raids of the slave-maker Formica sanguinca. Two colonies of L. fuliginosus living under different environmental conditions were studied - one in Finland, and one in Poland.