Causes and consequences of biological invasions: The Argentine ant in southern California

Biological invasions are recognized as a leading threat to biodiversity as well as an increasing economic concern. In the United States, for example, invasive species accompany habitat loss as the leading reason for decline of threatened and endangered species. In the last half of this century, many studies and reviews have been published relating to the introduction of exotic species. Perhaps most notably are the widespread and often severe impacts of introduced species on indigenous species. Exotics can directly compete with, prey upon, parasitize, or otherwise indirectly affect native species. In this dissertation, I examine the direct and indirect effects, pattern of spread, and mechanisms promoting the success of the invasion of Argentine ants into southern California.; This dissertation is organized into five freestanding chapters. In the first chapter, I examine the relationship between Argentine ant invasions and habitat fragmentation in promoting the decline of native ant species. In the second chapter, I investigate differences between native and introduced populations of Argentine ants and suggest mechanisms to explain their success as invaders. I return to the consequences of Argentine ants invasions in the third and fourth chapters where I examine the indirect effects of Argentine ants on coastal homed lizards, a species of special concern in California whose primary prey are the ant species being displaced by Argentine ants. In the fifth and final chapter, I reconstruct the spread of Argentine ants across the United States in order to describe the pattern of invasion for a species whose spread relies heavily on human-mediated jump-dispersal.