Predation promotes survival of beetles with lower resting metabolic rates

The energetic definition of fitness predicts that natural selection will maximize the residual energy available for growth and reproduction suggesting that energy metabolism might be a target of selection. In this experimental study, we investigated whether female and male yellow mealworm beetles, Tenebrio molitor L. (Coleoptera: Tenebrionidae), differ in their hiding behaviour, individual response latency time, and duration of immobility to treatments mimicking an approaching predation threat. We experimentally tested whether consistently repeatable anti‐predatory responses and resting metabolic rates (RMR) correlated with survival rates of individuals exposed to a nocturnal predator, the brown rat, Rattus norvegicus (Berkenhout) (Rodentia: Muridae). Resting metabolic rate was part of a syndrome involving anti‐predator behaviour. Individuals with lower RMR concealed themselves against predators in substrate more successfully than individuals with higher RMR, and hiding was associated with longer periods of immobility. Ultimately, mortality was higher in the high‐RMR beetles compared to the low‐RMR beetles. Our results provide direct evidence of natural selection against mobility, i.e., for reduced RMR in T. molitor beetles.     

Lethal control of an apex predator has unintended cascading effects on forest mammal assemblages

Disruption to species-interaction networks caused by irruptions of herbivores and mesopredators following extirpation of apex predators is a global driver of ecosystem reorganization and biodiversity loss. Most studies of apex predators'' ecological roles focus on effects arising from their interactions with herbivores or mesopredators in isolation, but rarely consider how the effects of herbivores and mesopredators interact. Here, we provide evidence that multiple cascade pathways induced by lethal control of an apex predator, the dingo, drive unintended shifts in forest ecosystem structure. We compared mammal assemblages and understorey structure at seven sites in southern Australia. Each site comprised an area where dingoes were poisoned and an area without control. The effects of dingo control on mammals scaled with body size. Activity of herbivorous macropods, arboreal mammals and a mesopredator, the red fox, were greater, but understorey vegetation sparser and abundances of small mammals lower, where dingoes were controlled. Structural equation modelling suggested that both predation by foxes and depletion of understorey vegetation by macropods were related to small mammal decline at poisoned sites. Our study suggests that apex predators’ suppressive effects on herbivores and mesopredators occur simultaneously and should be considered in tandem in order to appreciate the extent of apex predators’ indirect effects.     

Differential survival of Euselasia apisaon Dahman (lepidoptera: riodinidae) pupae at understorey plants in the Eucalyptus plantations of Belo Oriente, MG, Brazil

Herbivorous insects may attack eucalyptus causing economic losses. One of these pests is the moth Euselasia apisaon Dahman, a key pest in the basin of middle Rio Doce. Here we studied the survival of pupae of this moth in Eucalyptus and in understorey plants and tested the hypotheses: i) live pupae are more abundant in plants of the understorey than in eucalyptus, ii) there is no difference between the abundance of pupae in different plants of the understorey. We sampled three areas cultivated with eucalyptus in Belo Oriente, MG, and samples were taken in five plots each area, getting five branches of each plant and of five eucalyptus trees that bordered the plot. The proportion of live and dead pupae and the mortality rate were estimated. The abundance of live pupae was higher in the understorey and the mortality rate of pupae was the same among different families of plants of the understorey. It is possible the larger available leaf area of understorey plants justify the greater abundance of live pupae in this habitat, however, avoidance of feeding habitat to finish the life cycle is also a possible explanation. Mortality rate in plants of the understorey points to an equal pressure of natural enemies on the pupae. These appointments help us to understand the dynamics of pests in eucalyptus plantations, providing important information to support actions against pests in natural environments.     

Apex predator suppression is linked to restructuring of ecosystems via multiple ecological pathways

Removal of apex predators can drive ecological regime shifts owing to compensatory positive and negative population level responses by organisms at lower trophic levels. Despite evidence that apex predators can influence ecosystems though multiple ecological pathways, most studies investigating apex predators’ effects on ecosystems have considered just one pathway in isolation. Here, we provide evidence that lethal control of an apex predator, the dingo Canis dingo, drives shifts in the structure of Australia's tropical‐savannah ecosystems. We compared mammal assemblages and understorey structure at seven paired‐sites. Each site comprised an area where people poisoned dingoes and an area without dingo control. The effects of dingo control on mammals scaled with body size. Where dingoes were poisoned, we found greater activity of herbivorous macropods and feral cats, a mesopredator, but sparser understorey vegetation and lower abundances of native rodents. Our study suggests that ecological cascades arising from apex predators’ suppressive effects on herbivores and mesopredators occur simultaneously. Concordant effects of dingo removal across tropical‐savannah, forest and desert biomes suggest that dingoes once exerted ubiquitous top–down effects across Australia and provides support for calls that top–down forcing should be considered a fundamental process governing ecosystem structure.     

Role of small mammals in the persistence of Louping-ill virus: field survey and tick co-feeding studies

Louping-ill (LI) is a tick-borne viral disease of red grouse, Lagopus lagopus scoticus Lath. (Tetraonidae: Galliformes), and sheep, Ovis aries L. (Bovidae: Artiodactyla), that causes economic loss to upland farms and sporting estates. Unvaccinated sheep, grouse and mountain hares, Lepus timidus L. (Leporidae: Lagomorpha), are known to transmit LI virus, whereas red deer, Cenrus elaphus L. (Cervidae: Artiodactyla), and rabbits, Oryctolagus cuniculus L. (Leporidae: Lagomorpha), do not. However, the role of small mammals is unknown. Here, we determine the role of small mammals, in particular field voles, Microtus agrestis L. (Muridae: Rodentia), in the persistence of LI virus on upland farms and sporting estates in Scotland, using field sampling and non-viraemic transmission trials. Small mammals were not abundant on the upland sites studied, few ticks were found per animal and none of the caught animals tested seropositive to LI virus. Laboratory trials provided no evidence that small mammals (field voles, bank voles, Clethrionomys glareolus L. (Muridae: Rodentia), and wood mice, Apodemus sylvaticus L. (Muridae: Rodentia), can transmit LI virus between cofeeding ticks and, in the field, LI virus was prevalent only in areas with known LI virus competent hosts (grouse, mountain hares or unvaccinated sheep) and absent elsewhere. In contrast to the case of tick-borne encephalitis (TBE) virus in Europe, it is concluded that small mammals seem to be relatively unimportant in LI virus persistence.     

Ectoparasites of Chevrier's field mouse, Apodemus chevrieri, in a focus of plague in southwest China

Chevrier's field mouse, Apodemus chevrieri Milne-Edwards (Rodentia: Muridae), has been identified as the main wild reservoir of plague in the sylvatic plague focus of Yunnan Province, southwest China. Here, the ectoparasite communities of A. chevrieri and the potential medical and veterinary importance of these ectoparasites are described. A high proportion (66%) of 321 mice were found to be infested with ectoparasites. A total of 81 species of ectoparasite, including 48 species of chigger mite, 25 species of mesostigmatid (gamasid) mite, six species of flea and two species of sucking louse were collected. Most species of ectoparasite were relatively uncommon, but a few were abundant. Within this ectoparasite complex, 16 species have previously been reported to be vectors of human disease agents. Apodemus chevrieri would appear therefore to be a natural reservoir for plague bacilli and epidemic haemorrhagic fever (Korean haemorrhagic fever) viruses.     

The rules of engagement: how to defend against combinations of predators

Studies of inducible defenses have traditionally examined prey responses to one predator at a time. However, prey in nature encounter combinations of predators that should force them to produce phenotypic compromises. We examined how snails (Helisoma trivolvis) alter their phenotype in the presence of three different predator species that were presented alone and in pairwise combinations. When snails were exposed to each predator alone, they formed predator-specific defenses that reflected the differences in each predator’s foraging mode. When snails were exposed to pairwise combinations of predators, their phenotype was dependent on their ability to detect each predator, the risk posed by each predator, and the effectiveness of a given defense against each predator. Consequently, responses to combined predators were typically biased towards one of the predators in the pair. This suggests that prey facing combined predators do not form simple intermediate defenses and, as a result, may experience enhanced mortality risk when they encounter natural predator regimes.     

Predispersal seed-predation by insects in the Venezuelan Central Plain: Overall patterns and traits that influence its biology and taxonomic groups

Predispersal seed predation (PSP) by insects was studied in a plant community of the Venezuelan Central Plain (VCP). The main goal was to examine to what extent vegetation structure and fruit–seed attributes determined the incidence of PSP by insects at the community level. We studied a total of 187 species from 59 families, in five habitat types. The proportion of seed-predated plant species (N=89; 47.6% of the total) was explained by different factors such as the abundance of legume families, plant species richness, fruit dehiscence, seed biomass, and starch content. Coleoptera was the most diverse taxonomic order of insect seed predators, with Bruchidae and Curculionidae showing the largest number of genera and species, followed by Lepidoptera (Pyralidae). Bruchidae and Pyralidae, but not Curculionidae, tended to be separated according to vegetation attributes, such as vegetation structure and flowering and fruiting phenology. In addition, Bruchidae was associated with dehiscent fruits, legumes, epizoochory, and granivory, whereas Curculionidae was more related with indehiscent fruits and endozoochory, and Pyralidae with abiotic seed dispersal. Bruchid larvae tended to prey upon single seeds, whereas larvae of Lycaenidae usually preyed upon more than one seed per fruit; Curculionidae did not show any clear pattern on this. One larva developing in a single seed (Type I) was the most common type of PSP, closely followed by one or more larvae developing outside seeds within the fruit (Type II). Type III (seed predation by adult insects inside the fruit) was the least common. Type I appears to occur most frequently in climbers, in the forest–savanna transition habitat, and in those cases in which insect adults emerged during the rainy season. By contrast, Types II and III tended to be associated with annual herbs, the lowest stratum (0.05–0.6 m), and disturbed areas. Moreover, Type I was usually found in samaras, drupes, and indehiscent fruits, whereas Type II and Type III were more commonly observed in capsules. Type I and Type II seeds differed in their nutritional composition, which in turn appears to affect seed predation specialization. The number of insect seed predator species and plant richness per habitat were positively correlated. The number of seed predator species was associated with the abundance of trees and climbers because more complex plant life forms offer a large variety of resources, woody species frequently had fruits and seeds larger than herbaceous species, and trees and climbers showed the lowest values of host specificity. To our knowledge, this study is the first one that characterizes the community of predispersal seed predators and simultaneously evaluates ecological, morphological, and nutritional factors determining the groups of seed predators and how PSP occurred.     

Gregarious pupation act as a defensive mechanism against cannibalism and intraguild predation

Coccinellid pupae use an array of defensive strategies against their natural enemies. This study aims to assess the efficiency of gregarious pupation as a defensive mechanism against intraguild predators and cannibals in coccinellid. The study was designed specifically (i) to determine the natural occurrence of gregarious pupation in the field for different coccinellid species, and (ii) to evaluate the adaptive value of gregarious pupation as a defensive mechanism against 2 types of predators (i.e., cannibals and intraguild predators). In the field, gregarious pupation consisted of a group of 2–5 pupae. The proportion of gregarious pupation observed varied according to species, the highest rate being observed with Harmonia axyridis Pallas (Coccinellidae; 14.17%). Gregarious pupation had no impact on the probability that intraguild predators and cannibals locate pupae. Intraguild predation occurred more often in site with gregarious pupation, while cannibalism occurred as often in site with gregarious pupation as in site with isolated pupa. However, for a specific pupa, the mortality rate was higher for isolated pupae than for pupae located in a gregarious pupation site both in the presence of intraguild predators and in the presence of cannibals. The spatial location of pupae within the group had no impact on mortality rate. Since it reduces the risk of predation, it is proposed that gregarious pupation act as a defensive mechanism for H. axyridis pupae.     

Partitioning mechanisms of Predator Interference in different Habitats

Prey are often consumed by multiple predator species. Predation rates on shared prey species measured in isolation often do not combine additively due to interference or facilitation among the predator species. Furthermore, the strength of predator interactions and resulting prey mortality may change with habitat type. We experimentally examined predation on amphipods in rock and algal habitats by two species of intertidal crabs, Hemigrapsus sanguineus (top predators) and Carcinus maenas (intermediate predators). Algae provided a safer habitat for amphipods when they were exposed to only a single predator species. When both predator species were present, mortality of amphipods was less than additive in both habitats. However, amphipod mortality was reduced more in rock than algal habitat because intermediate predators were less protected in rock habitat and were increasingly targeted by omnivorous top predators. We found that prey mortality in general was reduced by (1) altered foraging behavior of intermediate predators in the presence of top predators, (2) top predators switching to foraging on intermediate predators rather than shared prey, and (3) density reduction of intermediate predators. The relative importance of these three mechanisms was the same in both habitats; however, the magnitude of each was greater in rock habitat. Our study demonstrates that the strength of specific mechanisms of interference between top and intermediate predators can be quantified but cautions that these results may be habitat specific. An erratum to this article can be found at     

Predators in the plant–soil feedback loop: aboveground plant‐associated predators may alter the outcome of plant–soil interactions

Plant–soil feedback (PSF) can structure plant communities, promoting coexistence (negative PSF) or monodominance (positive PSF). At higher trophic levels, predators can alter plant community structure by re‐allocating resources within habitats. When predator and plant species are spatially associated, predators may alter the outcome of PSF. Here, I explore the influence of plant‐associated predators on PSF using a generalised cellular automaton model that tracks nutrients, plants, herbivores and predators. I explore key contingencies in plant–predator associations such as whether predators associate with live vs. senesced vegetation. Results indicate that plant‐associated predators shift PSF to favour the host plant when predators colonise live vegetation, but the outcome of PSF will depend upon plant dispersal distance when predators colonise dead vegetation. I apply the model to two spider‐associated invasive plants, finding that spider predators should shift PSF dynamics in a way that inhibits invasion by one forest invader, but exacerbates invasion by another.     

Spatially correlated recruitment of a marine predator and its prey shapes the large-scale pattern of density-dependent prey mortality

Patterns of predator dispersal can be critical to the dynamics of prey metapopulations. In marine systems, oceanic currents may shape the dispersal of planktonic larvae of both predators and prey, producing spatial correlations in the recruitment of both species and distinctive geographic patterns of prey mortality. I examined the potential for this phenomenon in two fishes, a wrasse and its grouper predator, at a Caribbean island where the near-shore oceanographic regime produces a temporally consistent spatial pattern of fish recruitment. I found that recruitment and adult abundance of groupers were spatially correlated with recruitment of wrasse prey. Furthermore, the local abundance of predators strongly affected the nature of density-dependent prey mortality. At sites with few predators, wrasse mortality was inversely density-dependent, while mortality was positively density-dependent at sites with higher predator densities. This phenomenon could be important to the dynamics of any metacommunity in which physical forces produce correlated dispersal.     

Overstorey–Understorey Interactions Intensify After Drought-Induced Forest Die-Off: Long-Term Effects for Forest Structure and Composition

Severe drought events increasingly affect forests worldwide, but little is known about their long-term effects at the ecosystem level. Competition between trees and herbs (‘overstorey–understorey competition’) for soil water can reduce tree growth and regeneration success and may thereby alter forest structure and composition. However, these effects are typically ignored in modelling studies. To test the long-term impact of water competition by the herbaceous understorey on forest dynamics, we incorporated this process in the dynamic forest landscape model LandClim. Simulations were performed both with and without understorey under current and future climate scenarios (RCP4.5 and RCP8.5) in a drought-prone inner-Alpine valley in Switzerland. Under current climate, herbaceous understorey reduced tree regeneration biomass by up to 51%, particularly in drought-prone landscape positions (i.e., south-facing, low-elevation slopes), where it also caused a shift in forest composition towards drought-tolerant tree species (for example, Quercus pubescens). For adult trees, the understorey had a minor effect on growth. Under future climate change scenarios, increasing drought frequency and intensity resulted in large-scale mortality of canopy trees, which intensified the competitive interaction between the understorey and tree regeneration. At the driest landscape positions, a complete exclusion of tree regeneration and a shift towards an open, savannah-like vegetation occurred. Overall, our results demonstrate that water competition by the herbaceous understorey can cause long-lasting legacy effects on forest structure and composition across drought-prone landscapes, by affecting the vulnerable recruitment phase. Ignoring herbaceous vegetation may thus lead to a strong underestimation of future drought impacts on forests.     

Effects of Edge Habitat and Nest Characteristics on Depredation of Artificial Nests in Fragmented Australian Tropical Rainforest

Variation in nest predation levels associated with rainforest fragmentation (edge effects) was assessed in Australia's Wet Tropics bioregion. Artificial nests were placed in the forest understorey at seven edge sites where continuous forest adjoined pasture, seven interiors (about 1 km from the edge), and six linear riparian forest remnants (50–100 m wide) that were connected to continuous forest. Four nest types were also compared, representing different combinations of two factors; height (ground, shrub) and shape (open, domed). At each site, four nests of each type, containing one quail egg and two model plasticine eggs, were interspersed about 15 m apart within a 160 m transect during September–October 2001. Predators were identified from marks on the plasticine eggs. The overall depredation rate was 66.5% of 320 nests' contents damaged over a three-day period. Large rodents, especially the rat Uromys caudimaculatus, and birds, especially the spotted catbird Ailuroedus melanotis, were the main predators. Mammals comprised 56.5% and birds 31.0% of predators, with 12.5% of unknown identity. The depredation rate did not vary among site-types, or between open and domed nests, and there were no statistically significant interactions. Nest height strongly affected depredation rates by particular types of predator; depredation rates by mammals were highest at ground nests, whereas attacks by birds were most frequent at shrub nests. These effects counterbalanced so that overall there was little net effect of nest height. Mammals accounted for 78.4% of depredated ground nests and birds for at least 47.4% of shrub nests (and possibly up to 70.1%). The main predators were species characteristic of rainforest, rather than habitat generalists, open-country or edge specialists. For birds that nest in the tropical rainforest understorey of the study region, it is unlikely that edges and linear remnants presently function as ecological population sinks due to mortality associated with increased nest predation.     

How predation by Podisus nigrispinus is influenced by developmental stage and density of its prey Alabama argillacea

The functional response of a predator to the density of its prey is affected by several factors, including the prey's developmental stage. This study evaluated the functional response of Podisus nigrispinus (Dallas) (Hemiptera: Heteroptera: Pentatomidae) females to fourth instars and pupae of Alabama argillacea (Hübner) (Lepidoptera: Noctuidae), an important pest of cotton (Gossypium hirsutum L., Malvaceae) in Brazil. The prey were exposed to the predator for 12 and 24 h, and in densities of 1, 6, 12, 18, 24, and 30 items per predator female. The predation data were subjected to polynomial regression logistic analysis to determine the type of functional response. Holling and Rogers' equations were used to estimate parameters such as attack rate and handling time. Podisus nigrispinus females showed functional response types II and III by preying on larvae and pupae, respectively. The attack rate and handling time did not differ between the 12 and 24 h exposure times. Predation rate was higher at higher larval and pupal densities; predation was highest at a density of 30 prey items per female, and it was similar at 18 and 24 prey per predator. Understanding the interaction of predators and their food resources helps to optimize biological control strategies. It also helps the decision‐making and the improvement of release techniques of P. nigrispinus in the field.     

Effects of Management Intensity and Season on Arboreal Ant Diversity and Abundance in Coffee Agroecosystems

Agricultural intensification decreases arthropod predator diversity, abundance and population stability, and may affect interactions between top predators and their arthropod prey – ultimately affecting ecosystem services. Coffee management intensification (reduction or removal of shade trees) reduces diversity of arthropod predators (ground-foraging ants). Because ants provide ecosystem services by controlling pests, influences of intensification on arboreal, coffee-foraging ant diversity and abundance are important. We here address how coffee intensification affects: (1) coffee-foraging ant diversity and abundance and (2) seasonal fluctuations in ant abundance. In each of four coffee sites of varying management intensity in Chiapas, Mexico, we sampled vegetation and using two methods, sampled ant diversity and abundance over two years. Sites significantly differed in vegetation and management intensity. Coffee-foraging ant diversity generally decreased with increasing management intensity (16–26% fewer species observed in the most intensively-managed site). Ant abundance was higher in the wet season. Management intensity, however, did not influence ant abundance or seasonal fluctuations in abundance. Our results highlight the importance of diverse agricultural systems in maintaining arthropod predator diversity, and point to one model system in which we may effectively test how diversity per se affects ecosystem services.     

Within‐generation consequences of postsettlement mortality for trait composition in wild populations: An experimental test

There is a critical need to understand patterns and causes of intraspecific variation in physiological performance in order to predict the distribution and dynamics of wild populations under natural and human‐induced environmental change. However, the usual explanation for trait differences, local adaptation, fails to account for the small‐scale phenotypic and genetic divergence observed in fishes and other species with dispersive early life stages. We tested the hypothesis that local‐scale variation in the strength of selective mortality in early life mediates the trait composition in later life stages. Through in situ experiments, we manipulated exposure to predators in the coral reef damselfish Dascyllus aruanus and examined consequences for subsequent growth performance under common garden conditions. Groups of 20 recently settled D. aruanus were outplanted to experimental coral colonies in Moorea lagoon and either exposed to natural predation mortality (52% mortality in three days) or protected from predators with cages for three days. After postsettlement mortality, predator‐exposed groups were shorter than predator‐protected ones, while groups with lower survival were in better condition, suggesting that predators removed the longer, thinner individuals. Growth of both treatment groups was subsequently compared under common conditions. We did not detect consequences of predator exposure for subsequent growth performance: Growth over the following 37 days was not affected by the prior predator treatment or survival. Genotyping at 10 microsatellite loci did indicate, however, that predator exposure significantly influenced the genetic composition of groups. We conclude that postsettlement mortality did not have carryover effects on the subsequent growth performance of cohorts in this instance, despite evidence for directional selection during the initial mortality phase.     

Piscivore efficiency and refuging prey: the importance of predator search mode

In predator-prey interactions, the efficiency of the predator is dependent on characteristics of both the predator and the prey, as well as the structure of the environment. In a field enclosure experiment, we tested the effects of a prey refuge on predator search mode, predator efficiency and prey behaviour. Replicated enclosures containing young of the year (0+) and 1-year-old (1+) perch were stocked with 3 differentially sized individuals of either of 2 piscivorous species, perch (Perca fluviatilis), pike (Esox lucius) or no piscivorous predators. Each enclosure contained an open predator area with three small vegetation patches, and a vegetated absolute refuge for the prey. We quantified the behaviour of the predators and the prey simultaneously, and at the end of the experiment the growth of the predators and the mortality and habitat use of the prey were estimated. The activity mode of both predator species was stationary. Perch stayed in pairs in the vegetation patches whereas pike remained solitary and occupied the corners of the enclosure. The largest pike individuals stayed closest to the prey refuge whereas the smallest individuals stayed farthest away from the prey refuge, indicating size-dependent interference among pike. Both size classes of prey showed stronger behavioural responses to pike than to perch with respect to refuge use, distance from refuge and distance to the nearest predator. Prey mortality was higher in the presence of pike than in the presence of perch. Predators decreased in body mass in all treatments, and perch showed a relatively stronger decrease in body mass than pike during the experiment. Growth differences of perch and pike, and mortality differences of prey caused by predation, can be explained by predator morphology, predator attack efficiency and social versus interference behaviour of the predators. These considerations suggest that pike are more efficient piscivores around prey refuges such as the littoral zones of lakes, whereas perch have previously been observed to be more efficient in open areas, such as in the pelagic zones of lakes.     

Effects of habitat fragmentation on the three-way interaction among ants,aphids and larvae of the giant purple emperor, <Emphasis Type="Italic">Sasakia charonda</Emphasis> (Hewitson), a near-threatened butterfly

Survival rates of both early and middle instar larvae of the nymphalid butterfly, Sasakia charonda, were estimated to be lowest on test trees planted in a meadow (site A), intermediate in a small, narrow secondary deciduous broadleaf forest (small patch, site B) and highest in a large secondary deciduous broadleaf forest (large forest, site C). The larval mortality rates due to predation by tree-climbing predators from the ground (tree climbing predator) such as ants and the larvae of carabids were estimated to be greater at sites A and B than those at site C. The number of predatory ants climbing test trees was significantly greater at sites A and B than at site C, and the ants harvested honeydew from aphids living on tree leaves at those two sites. Aphid densities were significantly higher on trees at sites A and B than at site C, and aphid densities and numbers of predatory ants were significantly and positively correlated at sites A and B. In an experiment controlling aphid density per branch on test trees, the numbers of ants and the mortality rates of S. charonda larvae were greater on branches with high aphid densities than on those with low aphid densities at both sites A and B. These results suggest that the aphid density per host tree was higher in the meadow and the small patch than in the large forest; at both sites these higher aphid densities attracted higher numbers of predatory ants to test trees, and as a result, mortality rates of S. charonda larvae were increased.     

The effect of habitat structure on prey mortality depends on predator and prey microhabitat use

Structurally complex habitats provide cover and may hinder the movement of animals. In predator–prey relationships, habitat structure can decrease predation risk when it provides refuges for prey or hinders foraging activity of predators. However, it may also provide shelter, supporting structures and perches for sit-and-wait predators and hence increase their predation rates. We tested the effect of habitat structure on prey mortality in aquatic invertebrates in short-term laboratory predation trials that differed in the presence or absence of artificial vegetation. The effect of habitat structure on prey mortality was context dependent as it changed with predator and prey microhabitat use. Specifically, we observed an ‘anti-refuge’ effect of added vegetation: phytophilous predators that perched on the plants imposed higher predation pressure on planktonic prey, while mortality of benthic prey decreased. Predation by benthic and planktonic predators on either type of prey remained unaffected by the presence of vegetation. Our results show that the effects of habitat structure on predator–prey interactions are more complex than simply providing prey refuges or cover for predators. Such context-specific effects of habitat complexity may alter the coupling of different parts of the ecosystem, such as pelagic and benthic habitats, and ultimately affect food web stability through cascading effects on individual life histories and trophic link strengths.