Within-population variation in demography of a herbivorous lady beetle

Abstract

The traditional view of insect population ecology has long assumed that individuals within a population are identical to each other in terms of survival and reproduction, handling populations as homogenized averages. This is, however, a biologically unrealistic assumption, because in any population there is a great variety of individuals of different ages, sizes, and degrees of fitness, thus exhibiting different demography. Recent studies on herbivorous insects have revealed a considerable variation in resource-use tactics within a population (Ohgushi, 1992). Nevertheless, few insect population studies have aimed at illustrating within-population variation in demography, although theoretical studies have recently emphasized individual differences as an essential source in determining population dynamics in natural populations.