Linking herbivore-induced defenses to population dynamics

I. Van der Stap, M. Vos, W.M. Mooij

Research output: Contribution to journal/periodicalArticleScientificpeer-review


1. Theoretical studies have shown that inducible defences have the potential to affect population stability and persistence in bi- and tritrophic food chains. Experimental studies on such effects of prey defence strategies on the dynamics of predator–prey systems are still rare. We performed replicated population dynamics experiments using the herbivorous rotifer Brachionus calyciflorus and four strains of closely related algae that show different defence responses to this herbivore. 2. We observed herbivore populations to fluctuate at a higher frequency when feeding on small undefended algae. During these fluctuations minimum rotifer densities remained sufficiently high to ensure population persistence in all the replicates. The initial growth of rotifer populations in this treatment coincided with a sharp drop in algal density. Such a suppression of algae by herbivores was not observed in the other treatments, where algae were larger due to induced or permanent defences. I 3. A variety of alternative mechanisms could explain differential herbivore persistence in the different defence treatments. Our analysis showed the density and fraction of highly edible algal particles to better explain herbivore persistence and extinctions than total algal density, the fraction of highly inedible food particles or the accumulation of herbivore waste products or autotoxins. 4. We argue that the rotifers require a minimum fraction and density of edible food particles for maintenance and reproduction. We conjecture that induced defences in algae may thus favour larger zooplankton species such as Daphnia spp. that are less sensitive to shifts in their food size spectrum, relative to smaller zooplankton species, such as rotifers and in this way contributes to the structuring of planktonic communities. [KEYWORDS: consumer–resource interactions ; inducible defences ; phenotypic plasticity ; Scenedesmus ; trait-mediated interactions.]
Original languageEnglish
Pages (from-to)424-434
JournalFreshwater Biology
Issue number3
Publication statusPublished - 2006




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