FACULTATIVE POLYGYNY AND HABITAT SUCCESSION IN BOREAL ANTS

High dispersal risks of ant queens make staying in the natal patch mor e attractive than long range dispersal. These alternative strategies a nd the mode of colony founding determine the average number of queens in the population. Increasing competition and queen predation make ind ependent colony founding increasingly difficult and the only option fo r new queens to reproduce in the habitat patch may be to enter an exis ting colony. The effect of nest-site availability to the number of que ens was studied in successional spruce-dominated taiga forests in facu ltatively polygynous ants Myrmica ruginodis, M. sulcinodis Leptothorax aceruorum, Formica sanguinea and F. truncorum. Decreasing relatedness among worker nestmates supports an association between increasing hab itat age and polygyny to some extent. M. sulcinodis and L. aceruorum p ersist in this type of taiga only for a relatively short period. Relat edness varied only slightly among populations, but lower relatedness e stimated in other studies suggested higher levels of polygyny in older populations. In M. ruginodis there was more variation in relatedness and it was possibly: connected to the relative proportions of the two social forms of the species. In F. sanguinea and F. truncorum the decr ease in relatedness with increasing age of the habitat was dearest. Ot her factors favouring limited dispersal and acceptance of new queens i n the colonies are, however, hard to separate. (C) 1995 The Linnean So ciety of London.