Author ORCID Identifier
https://orcid.org/0000-0003-0863-4406
Defense Date
2025
Document Type
Dissertation
Degree Name
Doctor of Philosophy
Department
Integrative Life Sciences
First Advisor
James R. Vonesh, PhD
Abstract
Aquatic plants, macrophytes, are foundational components of freshwater ecosystems, influencing abiotic conditions, providing habitat structure, and shaping biodiversity and community assembly processes. Their role is particularly critical in dynamic systems where disturbance regimes and colonization processes interact to shape community patterns and species distributions. Despite their ecological importance, macrophytes remain underrepresented in theoretical and applied studies of metacommunity dynamics and invasion ecology, especially in natural systems experiencing frequent environmental fluctuations. Here we aim to elucidate how macrophytes influence and respond to spatial and temporal variation in aquatic ecosystems, with a particular focus on colonization-extinction dynamics, invasion success, and community assembly. First, we use a five-year observational dataset from a riverine rock pool network to explore how local patch characteristics mediate the effects of landscape-level flooding on the colonization and extinction dynamics of the invasive macrophyte Hydrilla verticillata. Then we present a factorial field experiment testing how propagule pressure and flooding disturbance interact to shape H. verticillata invasion outcomes in the same rock pool system. Last, we build on insights from these studies to investigate how macrophyte presence, growth form, and biomass influence aquatic community structure, using both field surveys and a controlled mesocosm experiment manipulating H. verticillata and Lemna minor.
Our findings suggest that macrophyte dynamics are strongly shaped by environmental context, and in turn, act as key ecological filters that structure abiotic conditions and community composition in aquatic ecosystems. Specifically, we found that H. verticillata colonization is greater in large, infrequently flooded pools further from the river, while local extinction is greater in small, frequently flooded pools close to the river, highlighting the importance of local context in shaping species distributions. We then show that under stable conditions, propagule number and size both increased H. verticillata growth, but these effects are erased by flooding, demonstrating that disturbance can override propagule-driven invasion success.
Finally, macrophyte identity and biomass were shown to significantly alter abiotic conditions and community structure in both natural and experimental settings, influencing species richness, colonizer composition, and macrophyte biomass. This work demonstrates that macrophytes both respond to and actively structure aquatic environments in context-dependent ways. By integrating long-term observational data, field experiments, and mesocosm studies, this work advances our understanding of how macrophyte identity, disturbance regimes, and colonization dynamics shape freshwater community assembly in an era of rapid global change.
Rights
© The Author
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
11-24-2025