PhD defense: Janni Dolby Clement

Exploitation strategies in social parasites of fungus growing ants

Supervisor:
Dr. David Richard Nash

PhD Committee:
Dr. Jes Søe Pedersen (Chairman, KU)
Prof. Susanne Foitzik (University of Mainz)
Dr. Christian Rabeling (University of Rochester)

Abstract:
One of the most remarkable and complex parasitic interactions is social parasitism, where a parasite exploits a complete society, rather than an individual organism. By integrating into a society the parasite gains protection against predators and diseases, and can redirect resources from the host to increase its own fitness. The host uses a sophisticated recognition system in order to accept nestmates and expel intruders from their societies. However, this defence barrier can be overcome by parasites. Among the most specialized social parasites are the inquilines that exploit social insect colonies. Most inquiline ants have completely lost their sterile worker caste. Exceptions to this are Acromyrmex insinuator and Acromyrmex ameliae, parasites of fungus-growing ants. By still producing a worker caste both species offer a rare opportunity to study adaptive features in parasite worker behaviour. Furthermore closely related inquiline-host combinations can give us an insight into the trade-offs occurring in natural selection.

I will focus on elucidating aspects in parasite behaviour, recognition and queen competition. I have shown that parasite queens prefer to integrate into host colonies already infested with parasites and that they are more easily accepted into these colonies. I have performed a morphological comparison of the olfactory sensory system between the three distinctive castes of host workers and minor parasites workers, and study the recognition abilities of the parasite. I clarify infiltration strategies and chemical profiles of parasite queens, gynes and workers as well as host queens and host workers in parasitized and non-parasitized colonies. Finally I have investigated the reproductive competition between polygynous parasite queens and discuss the potential for hyperparasitism.