Inducible and constitutive defenses of valuable seaweed tissues: Consequences for herbivore fitness

• Optimal Defense Theory predicts that plants exposed to herbivory should allocate more resources to produce costly secondary metabolites in tissues with higher fitness values. To increase plant resistance, the secondary metabolites must have a negative impact on the preference and/or performance of herbivores. We tested the hypotheses that induction of secondary metabolites (phlorotannins) in a brown seaweed in response to grazing by herbivorous gastropods will differ between seaweed tissues with different fitness values (basal stipes and annual shoots), and that the subsequent change in food value will affect the fitness (growth and fecundity) of the gastropods. Induction of phlorotannins was significant in both tissue types but was more pronounced in basal stipes, which have a higher fitness value. Basal tissues also had significantly higher constitutive defense levels than did apical tissues. No effects of algal tissue type or grazing history on the growth rate of the gastropods were detected. However, the number of viable eggs was significantly lower for gastropods feeding on basal shoots, and there was a significantly lower proportion of viable eggs produced by gastropods that were offered previously grazed seaweed tissues. The results show that induced resistance, and its variation among different plant parts, call have significant negative effects on herbivore performance that may reduce future herbivore pressure and thus enhance plant fitness.

Ämnesord

NATURVETENSKAP  -- Biologi -- Ekologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Ecology (hsv//eng)

Nyckelord

ascophyllum nodosum

chemical defense

consumption.

egg prodection

fecundity

fitness

groivth

Littorina obtusata

phlorotannins

reproduction

resistance

within-plant variation

PHLOROTANNIN INDUCTION

ASCOPHYLLUM-NODOSUM

LITTORINA-OBTUSATA

BROWN

SEAWEED

RESISTANCE

PATTERNS

FUCALES

PLANTS

GROW

Publikations- och innehållstyp

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