DOI: 10.5061/dryad.sj142jj
title: Data from: Water-borne defense induction of a rockweed in the wild

description: 1. Laboratory-scale studies suggest that water-borne chemical cues
 released in grazing of marine macroalgae act as info-chemicals allowing
 the yet-undamaged conspecifics to increase their resistance before the
 actual herbivore attack. The relevance of this finding in natural
 populations has thus far remained unexplored. 2. We investigated spread of
 water-borne herbivore resistance in a field experiment using the littoral
 foundation species Fucus vesiculosus. We exposed algal genotypes for
 water-borne cues in the distances of 0.5 and 2 meters from the grazed
 cue-emitting genotypes. We measured herbivore resistance with preference
 experiments and recorded changes in the phlorotannin content. We recorded
 changes in biomass and length of the genotypes to test if water-borne
 resistance correlates with the grazing damage on the cue-emitter or incurs
 costs for the genotypes in terms of reduced growth. 3. In two of our four
 experimental blocks, induced resistance via water-borne cues took place
 and spread to undamaged neighbours that were two meters distance apart.
 This provides evidence of water-borne resistance induction in the wild as
 well as of small-scale spatial variation in the spread of induction. The
 undamaged neighbours induced resistance to a lesser extent than the
 directly grazed cue-emitters did, but resistance was consistently
 expressed among all 26 algal genotypes and independent of the amount of
 grazing damage on the cue-emitter. Herbivore resistance correlated
 negatively with the growth in the grazed cue-emitting genotypes while
 water-borne resistance was independent of the variation in growth. 4. Our
 results show, for the first time for marine macroalgae in a natural
 setting, that information about the increased risk of herbivory can be
 carried by water-borne cues and is used to prime or induce defences prior
 to an actual attack. The results we present furthermore indicate that
 water-borne resistance differs quantitatively and qualitatively from the
 resistance triggered by actively feeding herbivores. Ability to induce
 resistance prior the herbivore arrival may greatly influence the ability
 of littoral macroalgae to withstand the generally intense herbivory of
 marine benthic environments.
description: Fucus vesiculosus
 performance measurementsTraits of Fucus
 vesiculosus used for the analyses. Performance of the algae were measured
 before and after three-week field manipulation with direct herbivory and
 with water-borne cues formed in the herbivory. For further details see the
 original publication.F.vesiculosus_performance
 measurements.xlsFucus vesiculosus
 phlorotannin dataPhlorotannin content of
 the algae were measured after three-week manipulation in the field
 conditions with direct herbivory and with water-borne cues formed in the
 herbivory. For further details see the original
 publication.F.vesiculosus phlorotannin
 data.xlsxFucus vesiculosus
 consumption in preference bioassaysFile includes data from
 preference bioassays carried out to measure induced resistance in directly
 grazed genotypes of F. vesiculosus and in genotypes exposed to water-borne
 cues originating from their grazed conspecifics. For further details see
 the original publication.Induced resistance in
 F.vesiculosus_preference_bioassay_data.xlsx