|Vander Meer, Robert - Bob|
Submitted to: Behavioral Ecology and Sociobiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/30/2004
Publication Date: 10/7/2004
Citation: Johnson, C.A., Topoff, H., Vander Meer, R.K., Lavine, B. 2004. Do these eggs smell funny to you?: an experimental studey of egg discrimination by hosts of the social parasite Polyergus breviceps (Hymenoptera: Formicidae). Behavioral Ecology and Sociobiology. 57: 245-255. Interpretive Summary: Parasitic ants are ant species that have evolved mechanisms to integrate into their host ant species. The process involves some form of host queen take over by the parasitic ant queen(s) and generally leads to the premature death of the parasitized colony. For the system to work host colony workers must accept and rear eggs laid by the parasitic queen. Understanding this part of the integration process is interesting evolutionarily and may also increase the probability of successfully using parasitic ants in the biological control of pest ant species. Scientists at the Center for Medical, Agricultural, and Veterinary Entomology, USDA, ARS, Gainesville, Florida, The City University of New York, and Clarkson University, Potsdam, New York, determined that acceptance of eggs laid by queens of the slave-maker parasitic ant species, Polyergus breviceps, are not accepted immediately after host colony take over. Instead there appears to be a time-dependent mechanism involved in egg acceptance. Parasite laid eggs were rejected up to about seven months. This is important because it was previously thought that inherent brood odor similarity between parasite and host was responsible for the adoption and rearing of parasite laid eggs. The results reported here may impact the successful implementation of parasitic ants in the biological control of fire ants.
Technical Abstract: The adoption of immatures of the slave-maker ant, Polyergus, by naïve Formica host workers is considered a consequence of their close phylogenetic relationship as brood odors may be retained in the derived species. Pupae have frequently been used in laboratory discrimination tests to examine this problem. Their lengthy association with tending host workers (from eggs on), however, probably subjects them to contamination with host odors. Hence, previous findings demonstrating an increased tendency of host workers to tend Polyergus pupae over other species that have not had contact with host workers may merely reflect a response to conspecific signals acquired by Polyergus pupae through allogrooming. This study reports the findings of acceptance bioassays in which free-living and newly enslaved Formica host species had been offered foreign conspecific eggs, heterospecific Formica eggs, or Polyergus breviceps eggs. In addition, we examined their hydrocarbon profiles. Both Formica gnava and Formica occulta (free-living and newly enslaved) workers adopted and reared many of the conspecific eggs presented to them, and rejected almost all heterospecific Formica and P. breviceps eggs. Eventually, after approximately seven months, the number of P. breviceps eggs that were reared to adulthood increased. These results suggest that some time-dependent mechanism and not inherent brood odor similarity accounts for the eventual rearing of P. breviceps offspring during colony founding, when queens take over nests of adult Formica.