DFG FOR 1078 Natural Selection in Structured Populations

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E1 - The evolution of resistance and virulence in structured populations

Project leaders

Susanne Foitzik
University of Mainz, Evolutionary Biology

Dirk Metzler
LMU Munich, Evolutionary Biology

workerGeographic patterns of resistance and virulence depend on the fitness consequences of these traits and the population structure. Socially parasitic slavemaking ants use allospecific workers –  stolen during raids – to raise their young. Hosts developed defenses to evade parasitism – e.g. a newly found inducible defense – or to mitigate its costs after enslavement like the “slave rebellion” trait: enslaved Temnothorax workers were observed to kill pupae of the slavemaking ant Protomognathus americanus. The ensuing reduced growth of parasite nests leads to fewer and less destructive raids. We analyzed whether brood destruction raises the inclusive fitness of enslaved workers by reducing the raiding risk for related host colonies nearby. Genetic analyses detected weak host structure and host colonies that survived raids, which could directly benefit from rebellion of their slave relatives. A simulation showed that host structure and the costs of defense influence whether the slave rebellion trait can spread. Costs could include the erroneous killing of own brood and killing rates of parasite and host populations co-varied geographically.

We now plan to explore how local structure and the costs / benefits of defenses explain the inter- and intra-population variation in trait expression for various defense traits. With theoretical models we will analyze how metapopulation structure affects the chances of defense or virulence alleles to persist in a population. We will develop computational methods to estimate parameters of host-parasite interactions in a metapopulation context.