Towards a Movement Ecology: Modeling the Behavioral Response of Invasive Snails to Resources and Competition.

Abstract

The movement of individuals is one of the fundamental components of contemporary ecological problems such as metapopulation theory, epidemic models, competitive coexistence, and invasion dynamics. Advection-diffusion models, sometimes with a reaction term, have been usefully applied to such problems. For this dissertation, I broadened this approach by seeking to understand the effects of certain biotic and abiotic factors on movement ecology, and asking how to incorporate flexible behavioral responses into classical advection-diffusion models. I asked how resources, competitive environment, and habitat structure, interacting with body size or not, affect the movement behaviors of two coexisting invasive snails (Melanoides tuberculata and Tarebia granifera), and whether including the behavioral response to these factors improves advection-diffusion models of movement. I also made natural history observations regarding the snail system to provide a biological context for my empirical work. To address these questions, I conducted replicated experiments and observational studies, extended advection-diffusion models, and arbitrated among candidate models using AIC (Akaike's Information Criterion) model selection. Specific studies included (1) behavioral response to phenotypic and resource heterogeneities, and their interaction, (2) behavioral response to intraspecific and interspecific competition, and (3) behavioral response to spatially uniform versus spatially heterogeneous environments. In summary, this dissertation provides insights into modeling movement behaviors, using two coexisting invasive snails as the model system. I advocate for a behaviorally informed modeling framework that integrates sentient responses of individuals in terms of movement, improving our ability to accurately model ecological processes that depend on movement ecology.