Measuring cheating, fitness, and segregation in Dictyostelium discoideum.

Dictyostelium has become a model organism for the study of social evolution because of the stage in its life cycle where thousands of independent amoebae together form a fruiting body. Some individuals die to form a stalk that holds aloft the remaining cells for dispersal to new environments as spores. Different genotypes can aggregate together, creating opportunities for exploitation by cheaters that contribute a smaller proportion of cells to the stalk. Clustering of genotypes into separate fruiting bodies reduces the opportunities for cheating. Some genotypes achieve this by segregating after aggregation. Here we describe techniques for assaying cheating and segregation in D. discoideum. We cover how to grow and maintain cells, fluorescently label genotypes, design experiments for accuracy and precision, calculate fitness and segregation, and interpret the results.