Seaweed-mediated indirect interaction between two species of meso-herbivores

Abstract

Previous studies on trait-mediated trophic interactions in marine ecosystems were restricted to pair-wise interactions between one species of meso-herbivore and plant, though multigrazer interactions are more common in nature. We investigated whether the feeding of one consumer, either the periwinkle Littorina littorea or the isopod Idotea baltica, affected consumption by the other consumer via anti-herbivory defence induction in the brown seaweed Fucus vesiculosus. To test the generality of our findings, we ran similar experiments with seaweed/grazer populations in the North and Baltic Seas (NE Atlantic). Grazer-specificity in induction strength was assessed by using the same species of grazer for induction and consumption. 'Indirect' induction effects were assessed by using different species of grazers for induction and consumption. Palatability assays were run with live algae and with reconstituted food to distinguish between different mechanisms of resistance. Grazing by herbivores induced a chemical defence in F. vesiculosus. In the North Sea population, the induced defences were only effective against I. baltica, regardless of inducer identity. The sensitive responses of I. baltica to the induced defences were also detected in the reconstituted food assays using Baltic Sea organisms. Thus, marine meso-grazers may be affected by previous feeding through the same or a different species of consumer by modified prey traits, such as induced chemical defences. Furthermore, the magnitude of the effect in the induced defences can be determined by species-specific sensitivity.

Season affects strength and direction of the interactive impacts of ocean warming and biotic stress in a coastal seaweed ecosystem

“…Typically, mesograzers are omnivores exhibiting feeding preferences (Wahl and Hay ; Jormalainen et al ; Jaschinski et al ). Their feeding choice behavior and, thus, the fate of potential prey are influenced by the prey species available (Wahl and Hay ; Jormalainen et al ), their food quality (Hemmi and Jormalainen ), inducible antiherbivore defenses (Hemmi et al ; Rohde et al ; Rohde and Wahl ), and by the identity of other consumers in the system (Yun et al ). All of these interactions are to some extent affected by temperature—and other global change factors such as salinity and nutrients—via shifting species distributions or phenologies (Ayres ), temperature sensitivity of defenses, or concentration of energy reserves affecting food quality (Korpinen et al ; Weinberger et al ; Rothausler et al ).…”

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

“…Due to ambiguous selection of an appropriate error term for posthoc tests involving within-subject by between-subject interactions, no post-hoc tests were computed for time × grazing interactions (Winer et al, 1991). Instead, one-tailed paired ttests (due to experimental confirmation by Yun et al (2010) that I. baltica induces anti-herbivory defences in F. vesiculosus) were performed for each time separately, to reveal indirectly which combination of treatment and time caused significant interactions. Normal distribution of differences in the consumption of previously grazed and non-grazed pieces was confirmed using the Kolmogorov-Smirnov test.…”

Grazer Functional Roles, Induced Defenses, and Indirect Interactions: Implications for Eelgrass Restoration in San Francisco Bay

“…This limited herbivory appears to induce a chemical defensive response in the eelgrass in the form of increased production of phenolic compounds. Such an induction of defenses has precedence in studies of other marine isopods; e.g., herbivory by Idotea baltica was found to induce a defense response in the brown alga Fucus vesiculus, which reduced subsequent herbivory by the isopod [53]. In our study, phenol content ranged from 0.2% to 1.2% dry mass in the controls, and as high as 2.4% in the Idotea treatment.…”

“…Such a trait-mediated indirect interaction between grazers through grazer-induced changes in plant traits has not previously been observed in a seagrass system; however, this phenomenon may be common in competitive interactions between mandibulate insect species on land plants [3,68]. In addition, there are a growing number of examples of plant trait-mediated indirect competitive interactions among grazers in marine systems, including on cordgrass in salt marshes (congeneric planthoppers [69] or gastropods and planthoppers [70]), and on several species of brown algae (gastropods and isopods [53,71], isopods and amphipods [72], and congeneric gastropods [22]). …”