Date of Award
Master of Science (MS)
School of Biological Sciences
Steven A. Juliano
The number of individuals in a competitive environment can affect the growth rate, survival, size, and fecundity of those individuals, which is known as density-dependent effects. Overcompensation may occur if few juveniles survive to adulthood in a high-density environment. Overcompensation arises when density dependent survival interacts with extrinsic sources of mortality, such that more juveniles survive to adulthood than if no extrinsic mortality had occurred.
I tested the hypothesis that density dependent effects are common and strong in the field for three mosquito species: Aedes aegypti, Aedes albopictus, and Aedes triseriatus. I surveyed naturally occurring densities in novel and established field containers, then introduced larvae at similar densities and censused the containers for survivors. The results indicated that either compensation or overcompensation would have been likely to occur at higher densities, for some of the sites and times tested, for each species.
Additionally, I tested the hypothesis that overcompensation will occur when early-acting extrinsic mortality is applied to naturally-occurring densities in the field. Overcompensation did not occur with the application of either early-acting or late-acting extrinsic mortality at the naturally-occurring densities tested.
Finally, I tested the hypothesis that the level of resource competition between larvae would be affected by the synchrony of larval cohorts, such that asynchronous and synchronous cohorts will respond differently to extrinsic mortality. The synchrony of juvenile cohorts could affect the likelihood of overcompensation by influencing the proportion of vulnerable individuals in a population. An agent-based model was developed to explore the effects of environmentally-induced hatching synchrony in a mosquito population. The initial density of individuals, hatch-event time intervals, the extent of juvenile mortality, and the timing of juvenile mortality are factors that were explored with the model. The results of the model indicated that overcompensation in the number of adults was influenced by the interaction between cohort synchrony and the extent of early-acting juvenile mortality.
Evans, Katherine G., "Overcompensation in Aedes Mosquitoes Populations: Field Tests on Likelihood and an Agent-Based Model To Investigate the Influence of Cohort Structure" (2019). Theses and Dissertations. 1194.