Intraguild predation does not necessarily have negative effects on pest biological control: insights from a multiple consumer–multiple resource food web population model

We develop a food web population dynamical based on an experimental pest biocontrol setup consisting of thrips and aphids (pests) being consumed by two agents Macrolophus pygmaeus and Orius laevigatus, and with O. laevigatus being an intraguild predator of M. pygmaeus. By means of numerical simulations, we show that pest biocontrol disruption can be avoided depending on initial population densities of pests and agents, despite the intraguild predation (IGP) of O. laevigatus upon M. pygmaeus. This possible avoidance of pest biocontrol disruption is in accordance with the referred experimental setup and moreover, the proposed model corroborates the importance of initial densities of pests and agents in the determination of the failure or success of pest biocontrol found in this and other biocontrol experimental setups.

Costs and Benefits of Wax Production in the Larvae of the Ladybeetle Scymnus nubilus

BACKGROUND: Larvae of the minute aphidophagous Scymnus nubilus Mulsant (Coleoptera: Coccinellidae) are common predators in apple orchards, covered by a wax layer that might act as a defense mechanism against natural enemies. However, the costs and benefits of protection conferred by wax remain to be assessed. We tested the following hypothesis: there is a trade-off in wax producing ladybeetles between the protection conferred by wax cover and the physiological or behavioral costs associated with its production. We predict that: (1) wax production is an efficient defensive mechanism (against intraguild predation), (2) wax production is associated with detrimental physiological (growth, reproduction) or behavioral effects (behavioral compensation: increased biomass consumption). RESULTS: Tests were carried out in the laboratory with wax and waxless larvae of S. nubilus, with and without lacewing larvae of Chrysoperla agilis (Neuroptera: Chrysopidae) being used as a potential intraguild predator of the coccinellid. Waxless individuals were more susceptible to intraguild predation by lacewing larvae. Adults originating from waxless larvae were lighter than the ones originating from wax larvae, suggesting a metabolic cost resulting from a constant need of wax production. Body-weight gain and conversion efficiency were lower in waxless larvae. Biomass consumption was similar, showing that waxless larvae did not compensate for the physiological cost by eating more aphid biomass. CONCLUSION: The results indicate the potential existence of a trade-off between growth and protection associated with wax production.

Aphid alarm pheromone alters larval behaviour of the predatory gall midge, Aphidoletes aphidimyza and decreases intraguild predation by anthocorid bug, Orius laevigatus

Intraguild predation is the killing and consuming of a heterospecific competitor that uses similar resources as the prey, and also benefit from preying on each other. We investigated the foraging behaviour of the gallmidge, Aphidoletes aphidimyza, a predator of aphids used for biological control that is also the intraguild prey for most other aphid natural enemies. We focus on how aphid alarm pheromone can alter the behaviour of the gallmidge, and predation by the anthocorid bug Orius laevigatus (O. laevigatus). We hypothesised that gallmidges would respond to the presence of (E)-β-farnesene (EBF) by leaving the host plant. Since feeding by Aphidoletes gallmidge larvae does not induce EBF emission by aphids, this emission indicates the presence of an intraguild predator. We found that gallmidge larvae reduced their foraging activities and left the plant earlier when exposed to EBF, particularly when aphids were also present. Contrastingly, gallmidge females did not change the time visiting plants when exposed to EBF, but lay more eggs on plants that had a higher aphid density. Lastly, EBF reduced the number of attacks of the intraguild predator, O. laevigatus, on gallmidge larvae, potentially because more gallmidges stopped aphid feeding and moved off the plant at which point O. laevigatus predated on aphids. Our work highlights the importance of understanding how intraguild predation can influence the behaviour of potential biological control agents and the impact on pest control services when other natural enemies are also present.

Intraguild predation in three generalist predatory mites of the family Phytoseiidae (Acari: Phytoseiidae)

Background The predatory mites, Neoseiulus californicus (McGregor), N. barkeri (Hughes), and Amblyseius swirskii Athias-Henriot, are important predators attacking many insect and mite pests. They can coexist in the same habitat and engage in intraguild predation (IGP). Main body IGP was assessed among the exotic one N. californicus and the native species N. barkeri and A. swirskii as Intraguild predator (IG-predator)/intraguild prey (IG-prey) in either absence or presence of extra-guild prey Tetranychus urticae Koch (EG-prey). In the laboratory, the physiological parameters, longevity, fecundity, and predation rate of these predatory mites’ females, fed on EG-prey, were evaluated, where phytoseiid larvae are considered as (IG-prey) or combined IG-prey with EG-prey. All predatory species consumed larval stages of each other’s, but in case of N. californicus, females failed to sustain oviposition on N. barkeri larvae. Also, it was noticed that N. californicus females killed 3 times more A. swirskii larvae than N. barkeri larvae, whereas A. swirskii consumed more N. californicus than N. barkeri larvae, respectively. Neoseiulus californicus lived longer on T. urticae and A. swirskii larvae than on N. barkeri, while the latter survived longer on T. urticae only than on the other prey or with combinations with T. urticae. Amblyseius swirskii lived shorter when fed exclusively on T. urticae or IG-prey than on EG-prey combined with IG-prey. In choice experiments, N. californicus showed a higher preference to consume more T. urticae than any of phytoseiid larvae. The comparison between T. urticae and IG-prey diets definite the higher influence of T. urticae on the fecundity in N. californicus and N. barkeri than on IG-prey, whereas in A. swirskii fecundity was as equal on T. urticae as on IG-prey N. californicus larvae. Conclusion A. swirskii seemed to be the strongest IG-predator.

Extraguild prey availability reduced cannibalism and reciprocal intraguild predation of Neoseiulus barkeri (Acari: Phytoseiidae) and Scolothrips takahashii (Thysanoptera: Thripidae)

Cannibalism and intraguild predation (IGP) are two common interactions occurs in animal kingdom which influence their population structure and dynamics. Neoseiulus barkeri (Hughes) and Scolothrips takahashii (Priesner) are important natural enemies of citrus red mite Panonychus citri (McGregor). However, little was known about their interactions and how the availability of extraguild (EG) prey P. citri modulated their interactions. In this study, we determined incidences of cannibalism and intraguild predation of these two predators when different densities of extraguild prey P. citri were available. Our results showed that incidences of both cannibalism and IGP and were significantly reduced in the presence of the extraguild prey. The intraguild predation between N. barkeri and S. takahashii was bidirectional, but N. barkeri was a predominant intraguild predator over S. takahashii. The S. takahashii fed on immobile N. barkeri egg, and N. barkeri fed on inactive prepupa and pupa of S. takahashii, but the conspecifics seldom did. Our results indicated that the interactions of predators decreased significantly when prey was available. The predatory mite N. barkeri was a stronger interspecific competitor. The results of this study may be useful in developing effective biological control strategies against P. citri.

The effect of con/heterospecific diet on predation, oviposition and longevity of Amblyseius swirskii, Neoseiulus californicus and Phytoseiulus persimilis (Acari: Phytoseiidae)

Intraguild predation (IGP) consists of interacting individuals with context dependent roles that compete for food. Information about the predator trophic interactions i.e. cannibalism or feeding on heterospecific juveniles, is a key to understand the real impact of their combinations when introduced in biological control systems. The hypothesis here, assumed that the pairwise introduction of the female predatory mites, N. californicus (predator) + P. persimilis (heterospecific prey) and vice versa, A. swirskii (predator) + P. persimilis (heterospecific prey) and vice versa could exist in the Tetranychus urticae (main prey) scarcity. Three diets consisted of either conspecific or heterospecific six eggs, four eggs + four larvae and four protonymphs were introduced to the guilds. The predation and oviposition rates and the longevity of each female intraguild predator on detached bean leaf disc was recorded every three hours for 12 consecutive days. Neoseiulus californicus predation rate was estimated to be highest on conspecific eggs + larvae (11.35 ± 1.12) and so was on those of P. persimilis (55.7 ± 3.42). No significant difference was observed in N. californicus oviposition rate on three conspecific diets (P > 0.05), while its oviposition rate was highest on P. persimilis eggs + larvae (7.15 ± 0.80). Phytoseiulus persimilis predation rate was estimated to be highest on eggs + larvae both on N. californicus and P. persimilis as prey. Its oviposition rate was estimated to be highest when feeding on conspecific eggs (2.25 ± 0.19) and N. californicus eggs + larvae. Amblyseius swirskii fed on 45 ± 2.79 P. persimilis and 12.90 ± 1.51 A. swirskii eggs + larvae, which was significantly higher than predation rates on other stages (P < 0.01). Amblyseius swirskii oviposition rate was not significantly different on each of the three diets or on A. swirskii or P. persimilis as prey (P > 0.05). The oviposition rate of P. persimilis was the highest on A. swirskii eggs + larvae (1.45 ± 0.19). When N. californicus fed on each of the three diet types, no significant difference was observed in its longevity. The greatest longevity of P. persimilis was recorded when feeding on N. californicus/P. persimilis eggs. Longevity of A. swirskii was the greatest on P. persimilis eggs and protonymphs. Similarly, P. persimilis had the greatest longevity feeding on A. swirskii eggs. We concluded that the predator species were capable of surviving under conditions of scarce prey when heterospecific species are present.

Investigating the Role of the Eurasian Badger (Meles meles) in the Nationwide Distribution of the Western European Hedgehog (Erinaceus europaeus) in England

Biodiversity is declining globally, which calls for effective conservation measures. It is, therefore, important to investigate the drivers behind species presence at large spatial scales. The Western European hedgehog (Erinaceus europaeus) is one of the species facing declines in parts of its range. Yet, drivers of Western European hedgehog distribution at large spatial scales remain largely unknown. At local scales, the Eurasian badger (Meles meles), an intraguild predator of the Western European hedgehog, can affect both the abundance and the distribution of the latter. However, the Western European hedgehog and the Eurasian badger have shown to be able to co-exist at a landscape scale. We investigated whether the Eurasian badger may play a role in the likelihood of the presence of the Western European hedgehog throughout England by using two nationwide citizen science surveys. Although habitat-related factors explained more variation in the likelihood of Western European hedgehog presence, our results suggest that Eurasian badger presence negatively impacts the likelihood of Western European hedgehog presence. Intraguild predation may, therefore, be influencing the nationwide distribution of hedgehogs in England, and further research is needed about how changes in badger densities and intensifying agricultural practices that remove shelters like hedgerows may influence hedgehog presence.