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A non-native macroalga is less attractive for herbivores but more susceptible to light limitation and grazing stress than a comparable native species
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Advisor(s)
Abstract(s)
It has been suggested that non-native species are more tolerant towards abiotic stress than ecologically compara‑
ble native species. Furthermore, non-native marine macroalgae should be under lower grazing pressure than native
seaweeds, because they left their co-evolved enemies behind. As a consequence, they generally need to allocate less
energy to defences and can invest more into compensating the negative effects of abiotic stress or, assuming that
grazing pressure is low but not zero, to defensive reactions following grazer attack. This, in turn, should make them
more stress tolerant and less susceptible to herbivory. However, empirical evidence for both concepts is still scarce
and very little is known about whether enemy release is commonly associated with an enhanced tolerance towards
abiotic or biotic stress. We therefore ran an experimental study that (a) assessed attractiveness for grazers, (b) verified
whether short-term low-light stress impairs growth and (c) investigated whether light limitation and previous grazing
interactively affect the consumption of two macroalgae from Madeira Island, the native brown alga Stypopodium
zonale and the non-native red alga Grateloupia imbricata by the sea urchin Paracentrotus lividus. To come to ecologi‑
cally meaningful low-light stress levels, pilot studies were performed in order to determine the light compensation
point of photosynthesis for each algal species and then we established six light regimes around this point by reduc‑
ing the amount of incoming light. Simultaneously, we let one sea urchin graze on each algal individual to stimulate
a chemical defence in the seaweeds if present. In parallel to this, we kept the same number of algal replicates in the
absence of sea urchins. After 21 days, we compared algal growth in the absence of grazers as well as the attractive‑
ness of previously grazed and non-grazed algal material for P. lividus across all light regimes. Algal attractiveness was
assessed in no-choice feeding assays. The observation that the non-native alga was less consumed by the grazer than
the native species generally confirms the concept of enemy release. However, light limitation reduced growth in the
non-native but not in the native seaweed, while previous grazing reduced consumption of the native but enhanced it
in case of the non-native alga. These findings do not corroborate the assumption that enemy release can, through the
re-allocation of energy, enhance tolerance to abiotic (light limitation) or biotic (grazing) stressors in non-native marine
macroalgae.
Description
Keywords
Bioinvasions Light deficiency Grazing Anti-herbivore defences Grateloupia imbricata Stypopodium zonale Paracentrotus lividus . Faculdade de Ciências da Vida
Citation
Ramalhosa, P., Debus, S. L., Kaufmann, M., & Lenz, M. (2017). A non-native macroalga is less attractive for herbivores but more susceptible to light limitation and grazing stress than a comparable native species. Helgoland Marine Research, 70(1), 1-11. https://doi.org/10.1186/s10152-016-0478-3
Publisher
BMC