Regulation of anti-herbivore defence by Fucus vesiculosus in response to various cues
Sven Rohde (tel. +49 431 600 4575; fax +49 431 600 1671; e-mail email@example.com).
- 1We examined whether the marine macroalga Fucus vesiculosus induces defences against herbivory and, if so, which factors trigger this induction. In addition, we assessed whether induced defences are reduced after consumption stops.
- 2Induced effects were measured as changes in palatability rather than changes in the chemistry of the algae. We also tested for reductions in growth rate to determine whether induced defence incurs metabolic costs.
- 3We tested whether direct grazing, feeding on neighbouring plants, clipping and presence of a non-grazing herbivore could trigger induction. The isopod Idotea baltica and the gastropod Littorina littorea were used as herbivores.
- 4Both direct feeding of I. baltica and feeding on neighbouring plants induced chemical defence in F. vesiculosus, whereas the snail L. littorea only induced defence by direct grazing. Simulated herbivory (clipping), or the presence of herbivores without grazing, did not lead to defence induction. All induced defences were reversed within 2 weeks of consumption ending.
- 5Thus, F. vesiculosus differentiates between physical damage and natural herbivory. Furthermore, feeding by I. baltica on F. vesiculosus releases signals that trigger neighbouring Fucus individuals to induce defence.
- 6We found no evidence that metabolic costs incurred as a consequence of induced defence were sufficient to lead to growth reduction.
- 7This algal species demonstrates defence plasticity (i.e. induction and reduction of anti-herbivore defences ‘on demand’), with the response depending on both grazer identity and grazing pattern matter.