Degree

Doctor of Philosophy (PhD)

Department

Biological Science

Document Type

Dissertation

Abstract

Dispersal is a fundamental life-history process, influencing population persistence, metacommunity connectivity, system stability, and community structure. The first stage of dispersal, emigration, is highly context dependent, often strongly influenced by conspecific density. Although there is a wealth of theoretical literature exploring interspecific density effects on the density-emigration relationship, it has rarely been tested empirically. In this dissertation, my main objective was to determine how inter- and intraspecific densities may act in tandem to affect the density-emigration relationship, and how patch characteristics may alter these relationships using Tribolium flour beetles and the pathogenic fungus, Beauveria bassiana. In Chapter 2, I examined how competing species influenced each other’s density-emigration relationships while manipulating patch size and permeability, pairing empirical results with theoretical models to predict long-term steady states. Only the inferior competitor, T. confusum, exhibited altered DDE in response to T. castaneum, producing a saddle-shaped relationship, whereas T. castaneum was primarily influenced by patch characteristics. Model predictions aligned closely with observed competitive outcomes - frequent exclusion and extinctions of T. confusum. For my third chapter, prior to determining fungal density effects on movement, I first determined how these two host species differed in their response to B. bassiana using a variety of bioassays. In sum, I found that T. confusum was the less resistant host owing to a lower LD25 value and quicker time to post-mortem sporulation. In Chapter 4, I tested the joint effects of competition and pathogen density on movement and emigration. In an olfactory cue assay, I found that only T. confusum females showed a response, where they preferred uninfected over infected conspecifics. Although both species showed reduced net displacement with increasing fungal density, emigration patterns were more strongly driven by competitor density. When alone, species differed in their response to the fungus, but under competition, both intra- and interspecific competitor densities were the dominant predictors of emigration. Together, this work reinforces the notion that emigration behavior is highly context dependent and demonstrated that interspecific density-emigration relationships are driven by hierarchical ecological processes, with important consequences for population dynamics and species coexistence, which can vary depending on patch characteristics.

Date

4-20-2026

Committee Chair

James T. Cronin

LSU Acknowledgement

1

LSU Accessibility Acknowledgment

1

Download

Available for download on Thursday, April 19, 2029

Share

COinS