Understanding range expansion using a worldwide invasive snail and theoretical approaches

Factors of demography, evolution, and qualities of the abiotic and biotic communities all interact to determine where a species is found and may influence the ability of a species to expand its range. In the first two chapters, I used mathematical models to understand these forces as well as the mechanisms by which dispersal and migration evolves. In the first chapter, I explored how variation in patch size as well as population regulation modifies the immediate way that genetic structure drives the evolution of dispersal. I provided a mechanistic understanding of the way that genetic structure and variation in carrying capacity are correlated across space can reverse or magnify the effects of genetic structure alone. In chapter two, I described how antagonistic biotic interactions may provide a ubiquitous driving force for the maintenance of migration. Short term dynamics of local adaptation predicted the direction of change in migration rate where local maladaptation favored increased migration. The long term dynamics of strong interactions, in contrast to weak interactions, resulted in a runaway process where increased migration rates were selected for in both the host and parasite. The final two chapters used a worldwide aquatic invasive snail, Potamopyrgus antipodarum, as a natural experiment in range expansion. In chapter three, I characterized the shape of phenotypic plasticity of fitness related traits by comparing invasive and ancestral range lineages. Invasive lineages were opportunistic specialists with increased fitness at higher salinities compared to ancestral range lineages. In the final chapter, I described the worldwide distribution of Potamopyrgus antipodarum to address how differences among lineages may have affected the range and distribution across the globe. Clades that produced successful invasive populations globally were also widespread across the ancestral range showing that they may have general qualities that enable them to expand their range