Insect populations respond to fluctuating environments

Abstract

Models of populations inhabiting regularly fluctuating environments suggest that the nature of the population fluctuation is determined by the relative sizes of the characteristic response time of the population, T_R, and the period of the environmental variation. For example, May's¹ model of a density-regulated population inhabiting a sinusoidally varying environment showed that when the characteristic response time was long relative to the period of environmental fluctuation, Y, the population averaged out environmental fluctuations, whereas for T_R short relative to Y, the population tended to track environmental variations. Characteristic response time is a measure of how quickly a system returns to equilibrium following a disturbance, and for the logistic model and its immediate relatives, T_R equals the inverse of population growth rate, r. The present study investigated the responses of populations of the flour beetle, Tribolium castaneum, cultured in a series of regularly fluctuating environments. Responses to environmental fluctuations were striking at all periods of environmental fluctuations, but population density declined as environmental period lengthened.