Food availability effect on population dynamics of the midge Chironomus riparius: a Leslie modeling approach

Chironomus riparius (Diptera: Chironomidae) is a non-biting midge that is widely distributed in the northern hemisphere at temperate latitudes. The larvae, which are collector-gatherer, feed on sediment-deposited detritus. Chironomidae are of clear interest in ecology and in ecotoxicology. By including the food availability in the environment, an extended Leslie matrix model was developed for a laboratory population of C. riparius. Primary non-linear models were used to relate demographic parameters to the daily food input, and to estimate input parameters of the population matrix model. Due to the food amount dependence of the fourth larval stage duration, we dealt with a Leslie matrix of variable dimension. The Leslie matrix could become irreducible but imprimitive, depending on the daily food input, thus leading to a cyclic dynamic. We first characterized the Chironomidae population dynamics under non-limiting growth conditions, in terms of asymptotic growth rate, stable stage distribution and reproductive values. Then, we studied the food availability effect on model outputs, and we underlined the particular role of the fourth larval stage duration. We thus demonstrate the efficacy of a Leslie modeling approach to include secondary models, relating input parameters to the food availability, through a set of experimental data. We conclude with the robustness of Chironomidae to limiting food conditions: the population is still growing even when the daily food input falls in a drastic way. We advocate a posteriori the pertinence of such a modeling approach to predict the future of Chironomidae field populations, and further to include pollutant effect on the population dynamics.