Seeing the Wood for the Trees: Detecting Density Dependence from Existing Life-Table Studies

Abstract

The analysis of sixty-three life-table studies involving fifty-eight insect species by Stiling (1988) is re-examined. In particular, we question his conclusion that the apparent absence of density-dependent processes in more than half of the studies meaningfully reflects the prevalence of such processes in natural systems. We show that the proportion of sutides in which density dependence was detected by the original authors increases markedly with the number of generations available for analysis. This pattern is particularly clear from the twenty-eight life-tables available for univoltine insects. That density dependence was detected in a large proportion of the studies lasting for more than a few generations is an encouraging result considering the inadequacies in current methods for detecting the different types of density dependence that can act on insect populations.