Conditioning of Leaf Detritus Modulates Density-Dependent Growth of Aedes triseriatus Larvae (Diptera: Culicidae)

Abstract

Ration of food per capita of larval population is widely thought to limit mosquito production from container habitats, directly reflecting resource limitation. In this study, the importance of density-dependent resource limitation on larval Aedes triseriatus (Say) (Diptera: Culicidae) depended on the degree of microbial conditioning of senescent leaf detritus in surrogate tree holes. Density and ration strongly affected emergence, total female mass, and mean female mass of populations grown on leaves that had conditioned for 3 d, but had less impact when larval populations were grown on leaves that had conditioned for 1 mo. Ration per capita was a stronger predictor (50-94% of the variance) of all growth parameters measured for populations grown on leaves conditioned for 3 d compared with 1 mo (2-66% of variance), with the exception of development time. Larvae grew faster and to a larger body size on leaves conditioned for 3 d at low densities of larvae and a higher ration per capita. However, populations grown on leaves conditioned for 1 mo produced equal or more total mass and individuals of higher average mass than when grown on leaves conditioned for 3 d in treatments with low ration per capita. Well-conditioned detritus, representing the degree of microbial colonization of the organic material, must reflect the typical condition in tree holes with unconditioned leaves atypical. Therefore, results of this study suggest that experiments using well-conditioned leaves better estimate growth responses, including moderated density dependence and less importance of ration per capita, than experiments using unconditioned detritus.

Survival-Larval Density Relationships in the Field and Their Implications for Control of Container-Dwelling Aedes Mosquitoes

“…Some general principles for enhanced effectiveness may include: (1) Imposing the maximum possible extrinsic mortality (i.e., ensuring that the “Resulting new density” shown in Figure 1 and Figure 7 is as low as possible); (2) Targeting populations when larval abundances are low, so that negatively density-dependent effects on survival are unlikely (i.e., imposing mortality on populations at the low end of the horizontal axis in Figure 1 and Figure 7 ); (3) Knowing the shape of the survival-density response of the target species at the time and place control will be implemented (i.e., which of the relationships in Figure 1 or Figure 7 is most likely at that time and place). Year to year environmental differences in precipitation frequency and level [ 38 ], seasonal fluctuations [ 39 ], and container and detritus age [ 40 ] could all contribute to the degree of resource competition experienced by Ae. aegypti , Ae.…”