Consequences of an inducible defense: the ecological and evolutionary repercussions of temporary colony formation in Chlamydomonas reinhardtii

This dissertation attempts, through four connected experiments, to demonstrate the range of ecological and evolutionary responses to induced anti-predator defenses. The presented works all incorporate the formation of anti-predator colonies by the green alga Chlamydomonas reinhardtii in response to the filter feeding rotifer Brachionus calyciflorus and ciliated protist Euplotes eurystomus. Chapter one demonstrates that while it is an effective defense against micrograzing filter feeders, colony formation allows for opportunistic exploitation of colonies by macrograzers. Chapter two provides evidence that as part of other indirect effects in a simple community, the formation of inducible colony defenses can lead to C. reinhardtii being a superior apparent competitor. Chapter three describes the results of a differential gene expression study comparing C. reinhardtii phenotypes and homologous genes within the multicellular Volvocales. Chapter four considers the evolutionary consequences of colony defense by experimentally manipulating the phenotype to compensate for two distinct modes of predation. Taken together, these results demonstrate the capacity for inducible defenses to have dramatic consequences outside of the predator-prey interaction that induces the defense.Ph.D.Includes bibliographical referencesby Nicholas Loruss