Ecological effects and underlying molecular mechanisms of grazer-induced defenses in Fucus vesiculosus (Phaeophyceae)

Temporal variations in induced anti-herbivory traits and underlying cellular mechanisms have been largely neglected in the study of seaweed-herbivore interactions. Therefore, fluctuations in the induced defense of the brown seaweed Fucus vesiculosus as well as changes in gene expression occurring in response to isopod (Idotea baltica) and periwinkle (Littorina obtusata) attack were assessed and compared. This thesis provides evidence for a finely adjusted response of F. vesiculosus to isopod and periwinkle grazing based upon a temporally variable defense pattern, which is accompanied by extensive transcriptomic changes. The induction of defenses involved a functional reorganization from anabolic to catabolic processes. Furthermore, the expression of several genes with putative defensive functions was increased in response to isopod attack. Moreover, this thesis tested whether F. vesiculosus responds to water-borne cues from grazed neighbors and constitutes strong evidence against defense induction after receiving info-chemicals in North Sea F. vesiculosus and indicates that the ability to communicate may vary among seaweed habitats.