Testing for the induction of anti-herbivory defences in four Portuguese macroalgae by direct and water-borne cues of grazing amphipods

Abstract

Herbivory is a key factor in regulating plant biomass, thereby driving ecosystem performance. Algae have developed multiple adaptations to cope with grazers, including morphological and chemical defences. In a series of experiments we investigated whether several species of macroalgae possess anti-herbivore defences and whether these could be regulated to demand, i.e. grazing events. The potential of direct grazing on defence induction was assessed for two brown (Dictyopteris membranacea, Fucus vesiculosus) and two red seaweeds (Gelidium sesquipedale, Sphaerococcus coronopifolius) from São Rafael and Ria Formosa, Portugal. Bioassays conducted with live algal pieces and agar-based food containing lipophilic algal extracts were used to detect changes in palatability after exposure to amphipod attacks (=treatment phase). Fucus vesiculosus was the only species significantly reducing palatability in response to direct amphipod-attacks. This pattern was observed in live F. vesiculosus pieces and agarbased food containing a lipophilic extract, suggesting that lipophilic compounds produced during the treatment phase were responsible for the repulsion of grazers. Water-borne cues of grazed F. vesiculosus as well as non-grazing amphipods also reduced palatability of neighbouring conspecifics. However, this effect was only observed in live tissues of F. vesiculosus. This study is the first to show that amphipods, like isopods, are capable to induce anti-herbivory defences in F. vesiculosus and that a seasonally variable effectiveness of chemical defences might serve as a dynamic control in alga-herbivore interactions.

Herbivore-induced defence response in the brown seaweedFucus vesiculosus(Phaeophyceae): temporal pattern and gene expression

“…Furthermore, the ability to induce anti-herbivory traits in response to grazing by mesoherbivores has been repeatedly shown for different F. vesiculosus populations (e.g. Hemmi et al, 2004;Rohde et al, 2004;Long et al, 2007;Yun et al, 2007;Yun et al, 2012).…”

Ecology of antifouling resistance in the bladder wrack Fucus vesiculosus: patterns of microfouling and antimicrobial protection

“…However, there is increasing evidence that their contribution to antifeeding or antifouling resistance was overestimated (e.g. Jennings & Steinberg 1997, Toth & Pavia 2002, Deal et al 2003, Jormalainen et al 2003, Kubanek et al 2004, Yun et al 2007). Reports on inhibitory activity of phlorotannins with regard to the proliferation of marine bacteria are rare (Lau & Qian 1997, Iken et al 2009), and we are unaware of any studies investigating how the biofilm formation on a thallus is affected by phlorotannins.…”

Induced resistance in a brown alga: phlorotannins, genotypic variation and fitness costs for the crustacean herbivore

“…Studies on terrestrial plants provide accumulating support for the hypothesis that plants can sense and exploit information from damaged neighbors (reviewed in Dicke et al 2003;Kost and Heil 2006). While plant to plant communication is less studied in the aquatic environment, induced resistance as a response to waterborne cues originating either from a damaged plant or herbivore itself has been found in some Rohde et al 2004, Macaya et al 2005Díaz et al 2006;Yun et al 2007) but not all cases (Sotka et al 2002;Weidner et al 2004;Rohde and Wahl 2008;Macaya and Thiel 2008). The majority of those studies which demonstrated induced resistance as a response to waterborne cues measured algal consumption in preference bioassays, while only a single study measured phlorotannins, finding an induced increase in response to waterborne cues of herbivory .…”

“…Strong temporal variation in grazing pressure suggests that induced resistance may provide a profitable defense strategy for F. vesiculosus. While both herbivorederived and artificial cues have been demonstrated to induce a decrease in the palatability of F. vesiculosus Rohde et al 2004;Yun et al 2007), the role of phlorotannins in induced resistance in F. vesiculosus is still inadequately understood. Firstly, we investigate which cues, i.e., grazing by a natural grazer, grazing of a neighboring alga, the sole presence of a grazer and simulated grazing, trigger induced resistance (measured as decreased palatability) in F. vesiculosus.…”