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THE ECOLOGY OF SLAVEMAKING ANTS AND THEIR HOSTS IN NORTH TEMPERATE FORESTS

2002; Wiley; Volume: 83; Issue: 1 Linguagem: Inglês

10.1890/0012-9658(2002)083[0148

1939-9170

Joan M. Herbers, Susanne Foitzik,

Insect and Pesticide Research

Slavemaking ants are of great interest to biologists because of their highly specialized lifestyle. Slavemakers rely on the presence of heterospecific “slaves” to perform routine chores such as foraging and brood care. While we have considerable information on the behavior of these ants, mostly gleaned from laboratory studies, we know very little of their basic ecology. Here we report data collected over 20 yr in three geographic sites on the occurrence, spatial pattern, nest site use, and demography of two slavemaker species and three of the host species they enslave; all are small ants in the tribe Formicoxenini. We found geographic and temporal variation with respect to the interaction between social parasites and their hosts. The slavemaker Protomognathus americanus occurred in each geographic site, and in each its most common host was Leptothorax longispinosus; the other known hosts of this slavemaker, L. curvispinosus and L. ambiguus were less abundant. In a West Virginia site, slavemaker nests were smaller than in New York and Vermont sites. Additional data from West Virginia showed that the slavemaker is strongly constrained by its hosts there, but we found little impact of the parasite on its hosts. By contrast, in the New York site, we found strong evidence that the majority host was affected by the slavemaker: host nests showed important life history shifts between neighborhoods containing slavemakers vs. those that were parasite-free. Furthermore, the slavemaker was able to subjugate large host nests there and had large slave pools. In a third site in Vermont, parasite and host demography reflected their interaction weakly. We discovered a second slavemaking species there, and both parasites were preferentially found in areas of high host density. However, we uncovered no demographic or spatial evidence that slavemakers affected their hosts in Vermont. Likewise, we found no evidence in any site of demographic responses by the minority hosts to the presence of slavemakers. Thus our results imply that host–parasite interactions varied among host species and among geographic locales. The slavemaker system therefore is amenable to analysis in terms of parasite–host coevolution.