Graduation Term

Summer 2026

Degree Name

Doctor of Philosophy (PhD)

Department

School of Biological Sciences

Committee Chair

Steven Juliano

Committee Member

Rachel Bowden

Committee Member

Lise Comte

Committee Member

Halvor Halvorson

Committee Member

William Perry

Committee Member

Benjamin Sadd

Abstract

Populations of adult vector mosquitoes can be controlled by reducing larval mosquito abundances in aquatic habitats. This can be achieved via predation by introduced or naturally-occurring enemies (i.e., biocontrol or conservation control) or by applying pesticides to larval mosquito habitats (i.e., larviciding). The larvicide Bacillus thuringiensis israelensis (Bti) is commonly applied to ephemeral ponds to control populations of Culex pipiens mosquitoes that vector West Nile virus. However, there is concern that Bti may directly or indirectly harm non-target organisms such as dragonfly and damselfly naiads, which provide a natural source of mosquito biocontrol. Bti or predators may also induce positive mortality effects in target mosquito populations by reducing larval abundance prior to the onset of density-dependent resource competition, thereby yielding a greater abundance of adults, with greater fitness, or greater vectorial capacity, than would be expected without early-acting extrinsic mortality. Chapter I (in review, Pest Management Sciences) evaluates the biocontrol potential of odonate naiads (family: Coenagrionidae) against C. pipiens using a functional response experiment testing interactive effects of habitat complexity (characteristic of ephemeral ponds) and larval density on consumption. Chapter II (in review, Ecological Applications) describes a field mesocosm experiment investigating interactive effects of odonate naiad predators (families: Coenagrionidae, Aeshnidae, Libellulidae) and Bti on individual and population-level responses of C. pipiens. Chapter III provides a preliminary assessment of stable isotope analysis as a tool for determining whether Bti indirectly affected odonate naiad diets in the mesocosm experiment described in Chapter II; I report exploratory data and odonate dietary source contributions estimated by a stable isotope mixing model that incorporated empirical trophic discrimination factors. Throughout this dissertation, I discuss the roles of density dependence, sex-specific phenotypic plasticity in larval mosquitoes regulating anti-predator behavior responses, and predator foraging behavior on C. pipiens larval management outcomes.

Access Type

Dissertation-Open Access

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