Experimental host-parasite coevolution in a changing environment

Dr. Thomas U. Berendonk

Technische Universität Dresden
Institut für Hydrobiologie
Dresden

Dr. Gisep Rauch

Coevolutionary interactions between hosts and parasites are recognised as main potential forces influencing the life-history of both antagonists. A central prediction of coevolutionary theory is the reciprocal increase in parasite pathogenicity and host defence, acting antagonistically to shape virulence evolution. Virulence is defined as the fitness reduction of the host caused by a parasite and is influenced by both parasitic and host traits. Abiotic environmental conditions such as temperature are known to variably influence virulence in the short-term. However, how coevolutionary dynamics shape virulence evolution in the longterm under changing temperatures is unresolved. Our recent theoretical work predicts, that short-term temperature effects on virulence are reversed in the long-term when evolutionary adaptations are incorporated. To explicitly test these predictions, the current project will use an experimental coevolution approach to study how increasing temperatures influence virulence evolution in the long-term. To answer this question, we will use the ciliate Paramecium tetraurelia infected with Caedibacter taeniospiralis bacteria. Particularly, we will analyse how temperature influences the reciprocal evolutionary increase in parasite pathogenicity and host defence predicted by coevolutionary theory. Further, we will analyse the molecular genetic basis of the temperature dependent host defence evolution using a QTL-mapping approach. The obtained results will be compared with data from natural populations along a temperature gradient. The main goal of this project is to experimentally test for temperature dependent coevolutionary dynamics shaping virulence evolution to better understand how host-parasite interactions change in a highly variable world.