6 - Population Dynamics

Abstract

Populations of insects can change dramatically in size over relatively short periods of time, given their short generation times and high reproductive rates. Predicting the effects of global change has become a major goal of research on population dynamics. Insect populations respond to changes in habitat conditions and resource quality. Their responses to current and historic environmental changes help in anticipating their responses in the future. This chapter addresses temporal patterns of abundance, factors causing or regulating population fluctuation, and models of population dynamics. It briefly discusses the population fluctuation, factors affecting population size, and models of population change. Populations of insects can fluctuate dramatically through time, with varying effects on community and ecosystem patterns and processes, as well as on the degree of crowding among members of the population. The amplitude and frequency of fluctuations distinguish irruptive populations, cyclic populations, and stable populations. Cyclic populations have stimulated the greatest interest among ecologists. The various hypotheses that have been developed to explain cyclic patterns of population fluctuation all include density-dependent regulation with a time lag that generates regular oscillations. In addition, development of population dynamics models has been useful for forecasting changes in insect abundance and effects on crop, range, and forest resources.