APPARENT DEAR-ENEMY PHENOMENON AND ENVIRONMENT-BASED RECOGNITION CUESIN THE ANT LEPTOTHORAX-NYLANDERI

Inter- and intraspecific competition was investigated in ants of the m yrmicine genus Leptothorax in a deciduous woodland near Wurzburg, Germ any. The most common species, L. (Myrafant) nylanderi, lives in rottin g pine, oak, and elder sticks and may locally reach densities of 10 ne sts per m(2). In the studied sites, only a small fraction of colonies were polydomous, i.e. single colonies typically did not inhabit severa l nest sites. The home ranges of L. nylanderi colonies overlap the ran ges of other conspecific colonies and colonies of other species, espec ially L. (s.stt.) gredleri. Foragers from different colonies encounter ing one another in the field back off without exhibiting strong aggres sion, suggesting that colonies do not defend absolute foraging territo ries. In laboratory experiments, the frequency and severity of agonist ic interactions among workers from different colonies, all living in p ine sticks, increased significantly with the distance between their ne sts. Workers from colonies nesting in different types of wood exhibite d significantly more aggression. Experiments in which we transferred c olonies from pine sticks into artificial pine or oak nests corroborate the hypothesis that nesting material strongly influences colony odour in L. nylanderi The evolutionary significance of this apparent dear-e nemy phenomenon is discussed.