Mass Occurrence and Dominant Behavior of the European Ant Species Formica fuscocinerea (Forel)
Recently, masses of the ant Formica (Serviformica) fuscocinerea (Forel) have been occurring at numerous sites in Southern Germany. Although F. fuscocinerea is native to Southern Germany, these mass occurrences resemble ant invasions in density and dominance. This study aimed to investigate the underlying mechanisms that promote sudden mass occurrence of a previously inconspicuous ant species within its native range. To estimate the competitive dominance of F. fuscocinerea, species occurrence and abundance considering biotic and abiotic parameters were studied in a natural habitat where F. fuscocinerea co-occurred with two other common ant species, Myrmica ruginodis (Nylander) and Lasius niger (Linnaeus). To understand the species’ distribution in the field, laboratory experiments on interspecific competition were conducted. Finally, the colony structure of F. fuscocinerea was investigated with intraspecific aggression tests. Formica fuscocinerea dominated an area that, as indicated by strongly frequented foraging trails on the trees, provided important food sources, e.g. trophobionts, to the ants. Other ant species coexisted only at the periphery of the F. fuscocinerea range. Laboratory experiments revealed F. fuscocinerea as highly dominant species. Additionally, F. fuscocinerea showed a complete lack of intraspecific aggression between ants originating from distances up to 58 km, indicating weak or nonexistent behavioral boundaries among ants of physically separated nests. Since extraordinarily high worker densities, strong interspecific dominance and a lack of colony boundaries within supercolonies are considered to be important traits of several invasive ant species we conclude that the same traits also promote the dominance of F. fuscocinerea.
Publisher URL: https://link.springer.com/article/10.1007/s10905-017-9654-9