Effects of larval density on a natural population of Culex restuans (Diptera: Culicidae): No evidence of compensatory mortality.

Abstract

1. We investigated the effects of strong density-dependence on larval growth, development, and survival of the mosquito Culex restuans (Theobald). We tested the hypothesis that density reduction early in larval development could result in as many or more individuals surviving to adulthood (compensation or overcompensation, respectively), or increased reproductive performance via rapid development and greater adult size. 2. In a field study of a natural population of C. restuans we tested for the effects of a 75% lower density on percent survivorship to adulthood, number of adults, development time, adult size, adult longevity, and size dependent fecundity. 3. We found no evidence for compensation or overcompensation in adult production, nor for effects of lower density on percent survivorship. Low density yielded significant increases in adult size, adult longevity, and size-dependent fecundity, and a decrease in development time. 4. Estimated per capita population growth rate was significantly greater in the low-density treatment than in the high-density treatment. We infer this difference resulted from greater per capita resources increasing female size and fecundity, and reducing development time. Greater per capita population growth could therefore result from early mortality of larvae, meaning that the hydra effect, which predicts greater equilibrium population with, as opposed to without, extrinsic mortality, may be possible for these mosquitoes.