Interspecific differences in antipredator strategies determine the strength of non‐consumptive predator effects on stream detritivores

Abstract

Animal species diff er considerably in their response to predation risks. Interspecifi c variability in prey behaviour and morphology can alter cascading eff ects of predators on ecosystem structure and functioning. We tested whether speciesspecifi c morphological defenses may aff ect responses of leaf litter consuming invertebrate prey to sit-and-wait predators, the odonate Cordulegaster boltonii larvae, in aquatic food webs. Partly or completely blocking the predator mouthparts (mandibles and/or extensible labium), thus eliminating consumptive (i.e. lethal) predator eff ects, we created a gradient of predator-prey interaction intensities (no predator Ͻ predator -no attack Ͻ predator -non-lethal attacks Ͻ lethal predator). A fi eld experiment was fi rst used to assess both consumptive and non-consumptive predator eff ects on leaf litter decomposition and prey abundances. Laboratory microcosms were then used to examine behavioural responses of armored and non-armored prey to predation risk and their consequences on litter decomposition. Results show that armored and non-armored prey responded to both acute (predator -non-lethal attacks) and chronic (predator -no attack) predation risks. Acute predation risk had stronger eff ects on litter decomposition, prey feeding rate and prey habitat use than predator presence alone (chronic predation risk). Predator presence induced a reduction in feeding activity (i.e. resource consumption) of both prey types but a shift to predator-free habitat patches in non-armored detritivores only. Non-consumptive predator eff ects on prey subsequently decreased litter decomposition rate. Species-specifi c prey morphological defenses and behaviour should thus be considered when studying non-consumptive predator eff ects on prey community structure and ecosystem functioning.

Geographic shifts in the effects of habitat size on trophic structure and decomposition

“…It has recently been shown in a terrestrial trophic cascade that anti-predator behaviour in prey can reverse the sign of the indirect effects between predators and basal resources (Wu et al 2015). Similar studies in aquatic systems have shown that behavioural predator resistance in prey can affect the strength of trophic cascades (Lagrue et al 2015, Ocasio-Torres et al 2015. Although we would predict that physical defences in prey will also affect the strength of trophic cascades, only a few studies have tested this prediction (Van Buskirk and McCollum 2000).…”

Scaling up our understanding of non-consumptive effects in insect systems

“…Shifts in insect prey traits in response to predators include behavioral changes [7][8][9][10][11], life history adjustments [12][13][14], and physiological changes [15][16][17][18][19] (See Table 1 & 2 for behavioral and physiological changes, respectively). The majority of studies to date link NCEs to changes in behavior, including changes in feeding [20][21][22], oviposition [23,24], colonization or dispersal [25][26][27], host-plant preference or habitat use [28][29][30] and increased predator avoidance [31,32]. As a whole, prey tend to respond to predators by modifying their behavior to become less apparent and reduce predator encounters (i.e.…”

The Braveheart amphipod: A review of responses of invasive Dikerogammarus villosus to predation signals

“…In contrast, the reduction in consumption in the presence of Cottus gobio kairomones was noted for another gammarid species -Gammarus pulex (Abjörnsson et al, 2000). According to Lagrue et al (2015), armored detritivore prey did not respond numerically to the presence of predators in contrast to non-armored species. As it was mentioned, D. villosus is more armored than other gammarids (Błońska et al, 2015).…”