Ant communities in taiga clearcuts: habitat effects and species interactions

We surveyed the structure or ant communities in young taiga forests by pitfall trapping in southern Finland. The sampling sites were clearcut and planted with conifers 14–20 yr before the sampling. The results indicated that the structure of the ant communities was largely determined by the top competitors, the territorial species of the wood‐ant group ( Formica aquilonia and F. lugubris ) in the older, and the aggressive slavemaking ant (F. sanguinea) in the younger clearcuts. Species interactions resulted in distinct spatial distributions of individual species depending on the competitive status of the species concerned. Competition and slavemaking were the most important factors on larger spatial scales. The spatial scale of competitive structuring was determined by the territory and colony sizes of the top competitors. On a finer scale, variability in moisture and tree‐canopy shading seemed to have enhanced coexistence of some competing submissive species by alleviating the effects of nest‐site competition and slavemaking. Competition between the wood ants and the slavemaking ant affected indirectly the distribution and abundance of the species subject to slavemaking, F. fusca and F. lemani. Similarly, the top competitors presumably affected the distributions of other interacting subordinate species indirectly through differential competitive effects on them. Overall, species interactions seemed to have induced considerable determinism in ant‐community succession in young forests.