Natural and Experimental Coevolution between the Invasive Garden Ant and its Parasites 

CLUSTER: „Experimental evolution and natural variation of Bacillus-invertebrate interactions“

Dr. Sylvia Cremer

Aim of the proposed project is to study spatial and temporal patterns of coevolution in the invasive garden ant, Lasius neglectus, and its fungal and bacterial hosts. When this ant species is introduced into new sites, it experiences a loss of adapted parasites, as it is freed from its natural parasites (“parasite release”) and encounters new parasites native to the introduced range that are not yet adapted to the new host species (“disrupted coevolution”). Each introduction thus sets the starting point of a new coevolutionary arms race by building new combinations of hosts and parasites. We will study the outcome of this arms race in populations differing in their age, size, genetic diversity and dominance of the invasive garden ant in the species community, by isolation of field fungal and bacterial parasites. To determine the “tightness of coevolution” in the different populations, we will then perform infections of the hosts and parasites sampled from the same and different field populations under standardised laboratory conditions, and test for parasite pathogenicity and host individual and collective (social) immune defences. We will test both across populations (spatial aspects) and the same populations for two time points in a distance of two years (temporal aspect). We will also perform an experimental evolution study, in which we determine the speed of adaptation of fungal (Metarhizium anisopliae) and bacterial (Bacillus thuringiensis) parasites to the invasive garden ant depending on the host genetic diversity and its ecological dominance. We will analyse changes in parasite pathogenicity and the corresponding genetic changes over time.