, Volume 166, Issue 2, pp 381–390 | Cite as

Plant defences and the role of epibiosis in mediating within-plant feeding choices of seagrass consumers

  • Adriana Vergés
  • Teresa Alcoverro
  • Javier Romero
Plant-Animal interactions - Original Paper


Within-plant variation in susceptibility to herbivory can significantly influence the ecological and evolutionary consequences of plant–herbivore interactions. Seagrasses are marine angiosperms characterised by substantial intra-individual differences in multiple traits, such as nutrients, chemical and structural defences and epibiotic load, all of which can strongly influence herbivore preferences. We quantified the within-plant feeding choices of the two main consumers of the temperate seagrass Posidonia oceanica––the fish Sarpa salpa and the sea urchin Paracentrotus lividus––and determined the plant traits that explained their foraging strategies. We found strong within-plant heterogeneity in both seagrass susceptibility to herbivory and chemical composition, but different consumers exhibited contrasting feeding choices. S. salpa preferred the most nutritious and chemically defended younger leaves, suggesting a full adaptation to consuming this macrophyte and a greater impact of this herbivore on the plant. In contrast, P. lividus consistently preferred the older leaves covered by epibionts, probably attenuating the relative impact of this consumer and helping to explain the weak effects usually recorded for this echinoid in undisturbed meadows. Artificial diet experiments showed that morphology and fine-scale structural defences were the primary determinant of urchin feeding choices, with nutrient content and chemical defences being of secondary importance. Epibiosis did not strongly influence fish feeding, but it did have a strong ‘shared-doom’ effect on urchin consumption. This effect was driven by a distinct preference towards a mixed diet that included both host tissues and their epibiotic community.


Epibiont-plant-herbivore interactions Phenolics Fouling Dietary mixing Optimal defence theory 



M. Becerro provided much hands-on advice with the artificial diet experiments as well as stimulating discussion and insights on our results. We thank E. Ballesteros and S. Oliver for their help with fieldwork, S. Escartin for assistance with aquaria work and L. Oliver for assistance with the final stages of manuscript preparation. Two anonymous reviewers significantly improved the quality of the final version. CN analyses were performed at the Serveis Científico-Tècnics of the Universitat de Barcelona by P. Fernández. This study was funded by grants CGL2007-66771-C02-01 and CGL2009-12562 from the Spanish Ministry of Science and Innovation.


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Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  • Adriana Vergés
    • 1
    • 2
  • Teresa Alcoverro
    • 2
  • Javier Romero
    • 3
  1. 1.Sydney Institute of Marine Science, Evolution and Ecology Research Centre, School of Biological, Earth and Environmental SciencesUniversity of New South WalesSydneyAustralia
  2. 2.Centre d’Estudis Avançats de Blanes (CSIC)BlanesSpain
  3. 3.Departament d’EcologiaUniversitat de BarcelonaBarcelonaSpain

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