A components study of competition in two cellular slime mold species: Dictyostelium discoideum and Polysphondylium pallidum

The mechanics of a short-term interspecific competitive situation for two species of cellular slime mold, Dictyostelium discoideum and Polysphondylium pallidum, were assessed experimentally, modelled mathematically, and linked together to form a computer model, the predictions of which were tested. Five major components in the model were exploitation, toxic interference, effect of physical factors or external forces, availability of resources, and number of potential competitors engaged in exploitation and interference. The exploitation component depended upon time required for spore germination, rate and form of amoeba colony expansion, time required for fruiting body production, and rate and form of fruiting body colony expansion.Both species interfered with the other's ability to form fruiting bodies. In mixed cultures, D. discoideum amoebae divided and consumed food between 9° and 27 °C but did not produce fruiting bodies above 24 °C. In mixed cultures, P. pallidum amoebae divided and consumed food between 18° and 37 °C but did not produce fruiting bodies below 24 °C. Temperature altered the parameter values of all subcomponents contributing to exploitation and interference. Numbers altered interference ability. A computer model for predicting area occupied by fruiting bodies of both species was used to run 324 simulations and was accurate in 90.1% of the cases.