The effect of prey density and host plant characteristics on oviposition and fertility in Anthocoris confusus (Reuter)

• 1 Anthocoris confusus females show the greatest egg production when fed on eight adult Aulacorthum circumflexus per day. Prey densities below six result in a marked fall off in egg production.
• 2 Low prey densities result in reduced egg fertility and a decrease in oviposition period.
• 3 A.confusus females oviposit on those parts of a broad bean plant which support the highest aphid densities. This increases the probability of survival of the emerging nymphs.
• 4 Females are also able to distinguish between young, fully turgid, plants and older, more flaccid, plants and oviposit preferentially in the younger ones. Thus the eggs develop before the plant dies.

     

Turbidity amplifies the non‐lethal effects of predation and affects the foraging success of characid fish shoals

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Temperature and prey density jointly influence trophic and non‐trophic interactions in multiple predator communities

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The roles of top and intermediate predators in herbivore suppression: contrasting results from the field and laboratory

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The larval diet of three anisopteran (Odonata) species

SUMMARY.

• 1 Comparisons between larval diets of three anisopteran species (Anax imperator, Aeshna cyanea and Libellula depressa) showed that their food intake changed depending on: (1) predator species, (2) time of year, and (3) developmental stage.
• 2 Although this last factor is not so important, the mean size of prey items and the range of prey species eaten by Auax imperator and Aeshna cyanea larvae increased with predator size.
• 3 Comparisons between prey availability and diets indicated differential selectivity by these predators.

     

Juvenile survival of a planktonic insect: effects of food limitation and predation

• 1 An experiment was conducted to investigate potential impacts of food limitation and copepod predation on juvenile survival of Chaoborus purtctipennis. We tested the hypotheses that: (i) juvenile survival of Chaoborus is influenced more by copepod predation than by starvation in a productive environment, and (ii) food limitation and predation interact to affect survival.
• 2 Effects of food concentration (approximately 800, 1400 and 2300 microzooplankton 1-^?1) and predator density (0, 1 and 2 Mesocydops edax 1-^?1) on Chaoborus development and survival were evaluated using a 3 × 3 factorial design. Jars containing lake water, the appropriate food and predator treatments, and two Chaoborus (<12h old) were rotated on a plankton wheel at 25°C. Survival and developmental stage were monitored daily until all individuals had either died or moulted to instar II.
• 3 Predation by Mesocydops was the major source of mortality, causing 87.5% of Chaoborus deaths over all treatments. Chaoborus mortality was significantly higher in treatments with Mesocydops (67–100%) than in predator-free treatment (0–13%).
• 4 Development time was significantly longer in the low-density food treatment than in the highest food treatment.
• 5 No significant interaction between food limitation and predation was detected.
• 6 These results suggest that predation by copepods may limit recruitment of juvenile Chaoborus in productive lakes.

     

Divergent phenotypic responses to predators and cyanobacteria in Daphnia lumholtzi

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Prey: predator ratio dependence in the functional response of a freshwater amphipod

1. First known for their shredding activity, freshwater amphipods also behave as active predators with consequences for prey population regulation and amphipod coexistence in the context of biological invasions. 2. A way to quantify predation is to determine the average consumption rate per predator, also known as its functional response (FR). 3. Although amphipods are gregarious and can display social interactions that can alter per capita consumption rates, previous studies using the FR approach to investigate amphipod predation ignored such potential mutual interference because they did not consider variations in predator density. 4. We investigated the FR of Echinogammarus berilloni feeding on dipteran larvae with joint variations in prey and predator densities. This bivariate experimental design allowed us to estimate interference and to compare the fits of the three main classes of theoretical FR models, in which the predation rate is a function of prey density alone (prey‐dependent models), of both prey and predator densities (predator‐dependent models) or of the prey‐to‐predator ratio (ratio‐dependent models). 5. The Arditi–Ginzburg ratio‐dependent FR model provided the best representation of the FR of E. berilloni, whose predation rate showed a decelerating rise to a horizontal asymptote as prey abundance increased. 6. Ratio dependence means that mutual interference between amphipods leads to prey sharing. Mutual interference is likely to vary between amphipod species, depending on their level of aggressiveness.     

The role of alien fish (the centrarchid Micropterus salmoides) in lake food webs highlighted by stable isotope analysis

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Pests controlling pests: does predator control lead to greater European rabbit abundance in Australasia?

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Searching by Adalia bipunctata (L.) (Coleoptera: Coccinellidae) and escape behaviour of its aphid and cicadellid prey on lime (Tilia×vulgaris Hayne)

• 1 The paper describes the behavioural interactions between searching larvae of Adalia bipunctata and its aphid and cicadellid prey on lime (Tilia×vulgaris Hayne).
• 2 The frequency with which the predator achieves contact with cicadellid nymphs of differing ages is related to direction of predator approach and predator perception by the cicadellid.
• 3 The success of a coccinellid in contacting and capturing its aphid prey is related to the predator's size and direction of approach, the perception of the predator by an aphid and the latter's ability to escape, the effectiveness of which is discussed.

     

The searching behaviour of Anthocoris confusus (Reuter) in relation to prey density and plant surface topography

• 1 The searching behaviour of A.confusus females was investigated in an artificial arena.
• 2 Females showed an increase in the frequency of turning movements following feeding and this concentrated search in a small area. As a result more prey were found in areas where prey distribution was clumped.
• 3 If no prey was encountered within 5–8 min the search track straightened out.
• 4 First and second instar nymphs searching on broad bean plants moved faster on the undersides of leaves which were the sites most likely to support aphid populations. A considerable proportion of available time was wasted in periods of inactivity.
• 5 It was concluded that while plant topography strongly influences search pattern, the underlying trend demonstrated in these experiments was of advantage to predators searching for colonial prey.

     

The facilitation of the native bluegill sunfish by the invasive bighead carp

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Studies on the basic components of the predation ofPhytoseiulus persimilis Athias-Henriot (Acarina: Phytoseiidae)

The basic components of the predation of Phytoseiulus persimilisAthias-Henriot feeding upon eggs of Tetranychus urticaeKoch were studied in an open system where the predator could disperse freely. The type of the functional response of the predator to the density of its prey was the same as that studied so far in a closed system, i.e.,Holling's Type 2. The search rate of the predator, however, was much lower in comparison with the result from a closed system. The oviposition of the predator per day was only weakly related to prey densities higher than 10 per leaf disc. But the emigration rate was inversely dependent upon the initial prey density up to 60 per leaf disc. The searching behaviour of the predator was influenced by both the web density spun by T. urticae and the density of the prey: the predator searched for its prey intensively only after it had contact with web. Mutual interference was observed in prey consumption, but not in the emigration rate. The emigration rate was largely dependent upon the prey density available per predator.     

Increasing conspecific density weakens the ability of intermediate predators to develop induced morphological defences to top predators

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Small stonefly predators affect microbenthic and meiobenthic communities in stream leaf packs

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The influence of moss on grazers in high‐altitude streams: food,refuge or both?

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Dietary complexity and hidden costs of prey switching in a generalist top predator

1. Variation in predator diet is a critical aspect of food web stability, health, and population dynamics of predator/ prey communities. Quantifying diet, particularly among cryptic species, is extremely challenging, however, and differentiation between demographic subsets of populations is often overlooked.
2. We used prey remains and data taken postmortem from otter Lutra lutra to determine the extent to which dietary variation in a top predator was associated with biotic, spatial, and temporal factors.
3. Biotic data (e.g., sex, weight, and length) and stomach contents were taken from 610 otters found dead across England and Wales between 1994 and 2010. Prey remains were identified to species where possible, using published keys and reference materials. Multi‐model inference followed by model prediction was applied to test for and visualize the nature of associations.
4. Evidence for widespread decline in the consumption of eels (Anguilla anguilla) reflected known eel population declines. An association between eel consumption and otter body condition suggested negative consequences for otter nutrition. Consumption of Cottus gobio and stickleback spp. increased, but was unlikely to compensate (there was no association with body condition). More otters with empty stomachs were found over time. Otter sex, body length, and age‐class were important biotic predictors of the prey species found, and season, region, and distance from the coast were important abiotic predictors.
5. Our study is unique in its multivariate nature, broad spatial scale, and long‐term dataset. Inclusion of biotic data allowed us to reveal important differences in costs and benefits of different prey types, and differences between demographic subsets of the population, overlaid on spatial and temporal variation. Such complexities in otter diet are likely to be paralleled in other predators, and detailed characterization of diet should not be overlooked in efforts to conserve wild populations.

     

The Effects of Prey Patchiness, Predator Aggregation, and Mutual Interference on the Functional Response of Phytoseiulus persimilis Feeding on Tetranychus urticae (Acari: Phytoseiidae, Tetranychidae)

The spatial distributions of two-spotted spider mites Tetranychus urticae and their natural enemy, the phytoseiid predator Phytoseiulus persimilis, were studied on six full-grown cucumber plants. Both mite species were very patchily distributed and P. persimilis tended to aggregate on leaves with abundant prey. The effects of non-homogenous distributions and degree of spatial overlap between prey and predators on the per capita predation rate were studied by means of a stage-specific predation model that averages the predation rates over all the local populations inhabiting the individual leaves. The empirical predation rates were compared with predictions assuming random predator search and/or an even distribution of prey. The analysis clearly shows that the ability of the predators to search non-randomly increases their predation rate. On the other hand, the prey may gain if it adopts a more even distribution when its density is low and a more patchy distribution when density increases. Mutual interference between searching predators reduces the predation rate, but the effect is negligible. The stage-specific functional response model was compared with two simpler models without explicit stage structure. Both unstructured models yielded predictions that were quite similar to those of the stage-structured model.     

Higher zooplankton species richness associated with an invertebrate top predator

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