No evidence of sensitivity to initial population size in a fungus–nematode soil food chain

Population dynamics are modeled by nonlinear differential equations. However, sensitive dependence on initial population size, which is typical of such models, is rarely taken into account by experimentalists. Three microcosm experiments are reported showing that the final population density of a common fungal-feeding nematode is not sensitive to the initial population size. One experiment was conducted in sterilized humus soil in which the fungus–nematode food chain became limited by carbon. Two parallel experiments were conducted in fertilized mineral soil kept nutrient-limited by adding glucose. An initially even distribution of population sizes was converted into a normal or normalizable unimodal distribution in all three experiments. The results support a view that the variation in final population size was due to stochasticity and measurement error rather than dynamic instability.