Effect of leaf litter and density on fitness and population performance of the hole mosquito Aedes triseriatus

Abstract.

• 1 We tested the effects of food, in the form of leaf litter, and density on population growth and fitness correlates of the tree hole mosquito Aedes triseriatus. Our field experiment used a 2 x 2 randomized block design, with three holes as blocks. In cages within three holes, we manipulated densities of Aedes triseriatus larvae, and presence of leaf litter. Our laboratory experiment used a 2 x 3 factorial design in which we also manipulated densities of larvae and availability of leaf litter within similar cages (inside, outside, or absent). For both experiments we determined effects on survival, days to and mass at eclosion of both sexes, and a composite index of population performance λ′, that estimates finite rate of increase.
• 2 In the field experiment, we found significant and large effects of leaf litter and of density on the performance of A. triseriatus. The effect of density did not depend on leaf litter availability. We documented significant variation among tree holes for most correlates of fitness. Often, the effects of treatments varied significantly depending on the tree hole tested.
• 3 In the laboratory experiment we found significant effects of density and litter, and that direct browsing on leaf litter is necessary for the effect of litter on performance of A. triseriatus. In the laboratory, the negative effect of increased density was dependent on leaf litter availability.
• 4 Our results demonstrate that leaf litter has important effects on population performance of tree hole mosquitoes in natural tree holes. Direct browsing on the surface of leaf litter is the most likely mechanism by which litter enhances population growth. The impact of litter on populations varies among tree holes.