Succession, Forest Fragmentation, and the Distribution of Wood Ants

Abstract

I tested the hypothesis that the distribution of territorial wood-ant species (Formica rufa group) of different colony structure and dispersal strategy relate differently to the dynamics and landscape structure of boreal forests. Monogynous species (colonies have only one queen and inhabit one nest) that disperse through nuptial flight and subsequent temporary nest parasitism, should primarily be found in young forests and in smaller old-forest fragments. These long-distance dispersers can reach these areas where the nests of F. fusca group ants (which the wood-ant queens invade and parasitize) are more common, and these wood-ant colonies can monopolize the small fragments. Polygynous species (colonies have many queens) that disperse mainly through nest budding and may form large colonies of cooperative nests, should primarily be found in old forests and larger old-forest fragments. In such patches these short-distance dispersers have enough space for developing into strong colonies capable of ruling out all other territorial species. I mapped the nests of eight territorial ant species, three of which belonged to the wood-ant group, in fragmented forests of different age in southern Finland. In general, the mapping data supported my hypotheses. The monogynous F. lugubris was more common in young forests and in small old-forest fragments than expected by chance. The polygynous F. aquilonia was more common in old forests and in larger old-forest fragments.