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We describe the composition of two colonies of wood ants (FM-1 and FM-2) from southern Finland, identified on the basis of morphological investigations of workers (for FM-1, also of alate gynes and males) as mixed colonies comprising individuals with phenotypes typical of Formica aquilonia Yarr., F. polyctena Först, and F. rufa L. The prevailing species (phenotypes) were F. polyctena in FM-1, and F. rufa in FM-2. Colony FM-1 was observed every year in the period 1996-2006, almost from the moment it was formed. A first tentative investigation in 1999 revealed that it was already a mixed one and was probably also polygynous. Systematic follow-up investigations from 2002 to 2006 demonstrated relative stability of the proportions of individual species (phenotypes). A possible origin of this permanently mixed colony is postulated and discussed.
Species composition, nest densities and ecological profiles of ant communities in three main typical forest habitats of Chełmowa Góra (Chełmowa Mount) in the Świętokrzyski National Park were studied: fertile Carpathian beech forest Dentario glandulosae-Fagetum, subcontinental linden-oak-hornbeam forest Tilio-Carpinetum (marginal zone and interior), continental mixed pine forest Querco roboris-Pinetum (marginal zone and interior). Additionally, a moist rye-grass meadow Arrhenatheretum elatioris adjacent to the mixed pine forest was also surveyed. Nest samples were collected by searching quadrats of different sizes (1 m2, 10 m2, 100 m2). In total, 16 species were found. Ant communities of the studied habitats differed from each other in their composition, abundance and structure. In respect of nest density, Myrmica ruginodis Nyl. dominated in Tilio-Carpinetum (in both forest zones) and in the interior of Querco roboris-Pinetum, Formica polyctena Först. in the marginal zone of Querco roboris-Pinetum and in Dentario glandulosae-Fagetum, and Lasius niger (L.) in the meadow. The results are discussed in the contexts of the former data from this region, and the possible community-forming impact of the local 'supercolony' of F. polyctena
Wood ants, i.e. species of the subgenus Formica s. str., are known to be temporary social parasites of ants of the subgenus Serviformica For. However, not only Serviformica colonies are used by young wood ant queens to start their own colonies. They are also able to take over colonies, at least queenless ones, of related species of the subgenus Formica s. str. This study followed five experimental colonies of wood ants – three of hybrid Formica aquilonia × F. polyctena, one of F. aquilonia-like form, and one of F. polyctena – artificially planted on islands of the Tvärminne archipelago, S Finland. After some years, the species identity of all colonies was F. polyctena, i.e. four of them had been taken over by heterospecific queens, whose offspring gradually replaced the old workers. These findings, together with already documented existence of hybrids in wood ants, partly explain the interspecific and intracolonial, until recently unaccountable, variability in wood ants of the Formica rufa group, frequently observed in southern Finland.
During long-term field studies on division of space between the territorial ant species Lasius fuliginosus (Latr.) and Formica polyctena Först, in southern Finland a severe decrease in the abundance of subordinate ant species was observed within L. fuliginosus territory. As part of this study we analyze the extent of changes in subordinate ant species assemblage in the light of already documented cases of L. fuliginosus prédation on colonies of subordinate ants. The results showed that L. fuliginosus had a much stronger negative impact on co-occurring subordinate species, than the neighbouring rival F. polyctena. The hypothesis of hunger-induced myrmecophagy in this species is put forward, and is discussed as a possible competitive mechanism by which L. fuliginosus could shape ant assemblages within its territories.
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