Compensation and resistance to herbivory in seagrasses: induced responses to simulated consumption by fish |
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Authors: | Adriana Vergés Marta Pérez Teresa Alcoverro Javier Romero |
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Institution: | 1. Centre d’Estudis Avan?ats de Blanes, CSIC, Accés a la Cala Sant Francesc, 14, 17300, Blanes, Girona, Spain 2. Departament d’Ecologia, Universitat de Barcelona, Avinguda Diagonal 645, 08028, Barcelona, Spain
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Abstract: | Herbivory can induce changes in plant traits that may involve both tolerance mechanisms that compensate for biomass loss and
resistance traits that reduce herbivore preference. Seagrasses are marine vascular plants that possess many attributes that
may favour tolerance and compensatory growth, and they are also defended with mechanisms of resistance such as toughness and
secondary metabolites. We quantified phenotypic changes induced by herbivore damage on the temperate seagrass Posidonia oceanica in order to identify specific compensatory and resistance mechanisms in this plant, and to assess any potential trade-offs
between these two strategies of defence. We simulated three natural levels of fish herbivory by repeatedly clipping seagrass
leaves during the summer period of maximum herbivory. Compensatory responses were determined by measuring shoot-specific growth,
photosynthetic rate, and the concentration of nitrogen and carbon resources in leaves and rhizomes. Induced resistance was
determined by measuring the concentration of phenolic secondary metabolites and by assessing the long-term effects of continued
clipping on herbivore feeding preferences using bioassays. Plants showed a significant ability to compensate for low and moderate
losses of leaf biomass by increasing aboveground growth of damaged shoots, but this was not supported by an increase in photosynthetic
capacity. Low levels of herbivory induced compensatory growth without any measurable effects on stored resources. In contrast,
nitrogen reserves in the rhizomes played a crucial role in the plant’s ability to compensate and survive herbivore damage
under moderate and high levels of herbivory, respectively. We found no evidence of inducibility of long-term resistance traits
in response to herbivory. The concentration of phenolics decreased with increasing compensatory growth despite all treatments
having similar carbon leaf content, suggesting reallocation of these compounds towards primary functions such as cell-wall
construction. |
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Keywords: | Compensatory growth Tolerance Resistance Defence Phenolic compounds Induced responses Plant– herbivore interactions Mediterranean sea |
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