Unexpected distribution of subordinates around nests of the wood ants

Abstract

The hierarchical organization of multi-species ant communities can be determined by the colony size and worker density-dependent differences in behaviour, recruitment efficiency, and aggressiveness between colonies of different species. In this study, we compared the competitive effects of two territorial wood ant species, Formica rufa and F. polyctena, on the ant species subordinated to them (encounterers and submissives) that nest close-by their mounds. The nests of subordinates were mapped in 10 m2 plots around the mounds of each of the two wood ant species, situated at a distance of 10, 20 and 30 m in four directions. The most abundant subordinate species were two Myrmica species: M. rubra and M. ruginodis. Interestingly, the nests of subordinates had an even diversity, density and distribution along with the distance from the wood ant mounds. The wood ant presence had a species-specific negative effect on some of the subordinate species, which can be in relation with the smaller mound sizes in F. rufa compared to F. polyctena. Based on our results it seems that subordinate species, due to their adaptability, might tolerate the circumstances close-by the wood ant mounds by changes in their strategies, foraging behaviour, and switching to the use of alternative food sources, like corpses of wood ants present in high abundance. Although these might not allow reaching normal colony size and reproduction, they may allow the colonies to survive while maintaining relatively large nest densities.