Multi-Stage Improvement of Marine Predators Algorithm and Its Application

The metaheuristic algorithms are widely used in solving the parameters of the optimization problem.The marine predators algorithm(MPA)is a novel population-based intelligent algorithm.Although MPA has shown a talented foraging strategy,it still needs a balance of exploration and exploitation.Therefore,a multi-stage improvement of marine predators algorithm(MSMPA)is proposed in this paper.The algorithm retains the advantage of multistage search and introduces a linear flight strategy in the middle stage to enhance the interaction between predators.Predators further away from the historical optimum are required to move,increasing the exploration capability of the algorithm.In the middle and late stages,the searchmechanism of particle swarmoptimization(PSO)is inserted,which enhances the exploitation capability of the algorithm.This means that the stochasticity is decreased,that is the optimal region where predators jumping out is effectively stifled.At the same time,self-adjusting weight is used to regulate the convergence speed of the algorithm,which can balance the exploration and exploitation capability of the algorithm.The algorithm is applied to different types of CEC2017 benchmark test functions and threemultidimensional nonlinear structure design optimization problems,compared with other recent algorithms.The results show that the convergence speed and accuracy of MSMPA are significantly better than that of the comparison algorithms.

Effects of Transgenic Bt+CpTI Cotton on Field Abundance of Non-Target Pests and Predators in Xinjiang, China

Transgenic insect-resistant cotton is being increasingly planted in Xinjiang cotton-planting regions, where geographical climate conditions and species composition of pests and natural enemies are greatly unique in China. Limited studies have been conducted on the ecological impacts of transgenic insect-resistant cotton, especially for transgenic double genes （Bt＋CpTI） cotton, in this region. In this study, the potential effects of transgenic Bt＋CpTI cotton on the seasonal abundance of non-target pests and predators were assessed from 2009 to 2011 in Korla, Xinjiang. The results showed that species composition and seasonal abundance of 5 groups of pests and 5 groups of predators were not significantly different between transgenic Bt＋CpTI cotton and non-transgenic cotton every year. It suggests that transgenic Bt＋CpTI cotton per se does not affect the population dynamics of non-target pests and predators on this crop in Xinjiang.

Natural predators of polyps of three scyphozoans:Nemopilema nomurai,Aurelia coerulea,and Rhopilema esculentum

Jellyfish blooms have become a hot research topic in recent decades because they pose a serious threat to fisheries,coastal industries,tourism,and the marine ecosystem.The life cycle of scyphozoan jellyfish consists of a pelagic medusa stage and a benthic polyp stage,where asexual reproduction and strobilation of the polyps directly affect the abundance of ephyra and subsequently medusa abundance.The dynamics of polyps are affected by both environmental and biological factors,and predation by natural predators is one of the most important biological factors.Nemopilema nomurai,Aurelia coerulea,and Rhopilema esculentum are three scyphozoan species that are commonly found in Chinese coastal waters,and previous studies reported that the survivorship of polyps differs among the three species when they are exposed to the same benthic community.To identify potential natural predators of polyps of these three species in Chinese coastal waters and to determine whether the predation rates on polyps of the three species differ,we collected 39 species of macrozoobenthos from the Bohai Sea,Yellow Sea,and East China Sea from May 2014 to June 2016 and conducted predation tests and predation rate measurements.We found that the nudibranchs Pleurobranchaea novaezealandiae,Okenia plana,and Chromodoris tinctoria and the sea anemones Paracalliactis sinica,Calliactis japonica,Anthopleura incerta,and Anthopleura midori could prey on the polyps of all three scyphozoan species.The predation rates increased with the body length of the predators.The predations rates were also related to the polyp species,although the different predators showed no consistent preference for a particular species of polyp.Our results indicate that introducing predators to locations inhabited by polyps might be a way to control the benthic polyp populations and prevent subsequent jellyfish blooms.

Hybrid Marine Predators Optimization and Improved Particle Swarm Optimization-Based Optimal Cluster Routing in Wireless Sensor Networks(WSNs)

Wireless Sensor Networks(WSNs)play an indispensable role in the lives of human beings in the fields of environment monitoring,manufacturing,education,agriculture etc.,However,the batteries in the sensor node under deployment in an unattended or remote area cannot be replaced because of their wireless existence.In this context,several researchers have contributed diversified number of cluster-based routing schemes that concentrate on the objective of extending node survival time.However,there still exists a room for improvement in Cluster Head(CH)selection based on the integration of critical parameters.The meta-heuristic methods that concentrate on guaranteeing both CH selection and data transmission for improving optimal network performance are predominant.In this paper,a hybrid Marine Predators Optimization and Improved Particle Swarm Optimizationbased Optimal Cluster Routing(MPO-IPSO-OCR)is proposed for ensuring both efficient CH selection and data transmission.The robust characteristic of MPOA is used in optimized CH selection,while improved PSO is used for determining the optimized route to ensure sink mobility.In specific,a strategy of position update is included in the improved PSO for enhancing the global searching efficiency of MPOA.The high-speed ratio,unit speed rate and low speed rate strategy inherited by MPOA facilitate better exploitation by preventing solution from being struck into local optimality point.The simulation investigation and statistical results confirm that the proposed MPOIPSO-OCR is capable of improving the energy stability by 21.28%,prolonging network lifetime by 18.62%and offering maximum throughput by 16.79%when compared to the benchmarked cluster-based routing schemes.

The Influence of Transgenic cry1Ab/cry1Ac,cry1C and cry2A Rice on Non-Target Planthoppers and Their Main Predators Under Field Conditions

Transgenic Bt rice has been shown to be an effective means of controlling Lepidoptera pests of rice. However, the potential roles of transgenic rice on planthoppers and their predators need to be investigated before its commercialization. Population density, species dominance and population dynamics are important parameters of arthropods populations in field. So the impacts of three transgenic Bt rice strains expressing crylAb/crylAc, crylC and cry2A on population density, species dominance and population dynamics of three species of planthoppers （Nilaparvata lugens, Sogatella furcifera and Laodelphax striatellus） and their three main predators （ Cyrtorhinus lividipennis, Pirata subpiraticus and Theridium octomaculatum） were evaluated at three sites in Hubei Province, China, in the current study. The results showed that among three species of planthoppers, both in transgenic and non-transgenic rice field, the predominant species ofplanthoppers within phytophagous guild was S. furcifera at any site either growing season （46-50%）. Significantly higher population density ofN. lugens was observed in T2A-1 field relative to Minghui 63 field at Wuxue in 2010. The species dominance of predator, P. subpiraticus, in TT51 field was significantly higher than that in T 1 C-19 and T2A-1 fields in 2009 at Xiaogan site. Sampling date significantly influenced six arthropods except for P. subpiraticus in 2010. The interaction between rice strain^sampling date had no significant adverse effects on the population dynamics of three species of planthoppers and their predators, except for several individual species in 2009. The interaction among rice strain^sampling date^sampling site also had no significant effect on six arthropods except for S. furcifera in 2009. The results indicated that transgenic Bt rice expressing crylAb/crylAc, cry2A and crylC had no significant adverse effects on the population dynamics of three planthoppers and their predators in most investigated data and sampling site.

Nest predators, nest-site selection and nest success of the Emei Shan Liocichla(Liocichla omeiensis), a vulnerable babbler endemic to southwestern China

Background: The Emei Shan Liocichla(Liocichla omeiensis) is a globally vulnerable babbler, endemic to southwestern China. We investigated its nest predators, nest-site selection and nest success at the Laojunshan National Nature Reserve in Sichuan, China in order to identify the precise nesting-habitat requirements of the species, and to test whether the nest-site-selection cues, preferred by the Emei Shan Liocichla, are positively associated with nest success.Methods: We used infrared cameras to determine nest predators. We compared the microhabitat attributes between nest and random sites, as well as successful and failed nests. We used Binary Logistic Regression to determine the most important variables affecting nest-site selection of the Emei Shan Liocichla. We used the nest survival analysis in Program MARK to estimate daily nest survival rates(DSR). Nest success was calculated using the Mayfield method.Results: In total 56 nests were found. The DSR for all nests that contained at least one egg was 0.9564 ± 0.0091(95 % CI 0.9346–0.9711)(n = 40), while the total nest success was 27.5 %. We identified four categories of predators in 10 nest predation events, i.e. squirrels(n = 5), snakes(n = 3), raptors(n = 1) and wasps(n = 1). We found that:(1) nest predation was the primary reason for nest failure of the Emei Shan Liocichla,(2) tree cover, bamboo cover, liana abundance and distance to forest edge or gap were the most important variables affecting nest-site selection of this species, and(3) the nest-site-selection variables we measured appeared not to be positively associated with nest success.Conclusions: Our findings suggest that the Emei Shan Liocichla tended to select nest sites near forest edges or gaps with good concealment and that nest-site selection by this species was nonrandom but not necessarily adaptive. Reducing forest-edge development and protecting bamboo stands should be effective for conservation of this species.

Effects of Predators on the Belowground Life Stages (Prepupae and Pupae) of the Western Flower Thrips, <i>Frankliniella occidentalis</i>(Thripidae: Thysanoptera): A Review

Western flower thrips, Frankliniella occidentalis, is a major cosmopolitan insect pest causing direct and indirect damage to greenhouse-grown horticultural crops. The primary way of managing western flower thrips populations is by routinely applying insecticides, which target the aboveground life stages: larvae and adult. However, insecticides are minimally effective against the pupal stages (prepupae and pupae) that reside in the growing medium or soil. Therefore, soil-dwelling biological control agents including: predatory mites [Stratiolaelaps scimitus and Hypoaspis = (Geolaelaps) aculeifer], and a rove beetle, Dalotia coriaria may be a viable option to induce mortality on the pupal stages. These predators will feed on the pupal stages of the western flower thrips and can provide mortality on a life stage that is tolerant of insecticide applications. However, these biological control agents need to be used in conjunction with other plant protection strategies, such as insecticides and/or biological control agents that target the aboveground life stages (larvae and adult) to effectively manage western flower thrips populations in greenhouse production systems.

Investigating how different classes of nest predators respond to the playback of the begging calls of nestling birds

Begging brings benefits and costs for nestling birds:it can indicate their needs to their parents,but it can also be a cue used by predators to find the nest.The costs,like many variables related to nest predation,can be specific to what kinds of predators are present and their auditory capabilities.These costs and benefits could also be affected by human noise,as noise could disrupt communication to parents and eavesdropping by predators,although human-produced noise might be easily ignored if predators can hear high-frequency components of the begging.We studied nest predation on a generalist bird,the Red-whiskered Bulbul(Pycnonotus jocosus),in a tropical forest in which there are many kinds of nest predators,including birds,mammals and reptiles.In 20 natural nests in which artificial eggs were placed,and subsequently in 140 artificial nests,we broadcast recordings of begging nestlings,with and without traffic noise,at two volume levels.We hypothesized that playback would increase predation relative to a silent control,and that mixing in traffic noise with the begging would decrease predation,as the begging signal was masked.However,we hypothesized that some predators,particularly small mammals with sensitive high-frequency hearing,might ignore the traffic noise.We found that predation was lowest for the control treatment,and lower for treatments mixed with traffic noise than for those without it.Small mammals,however,showed an unexpected pattern,displaying less nest predation in the treatments with traffic noise.Our results demonstrate the human-associated noise can disturb nest predators and influence which kinds of predators use begging to locate nests.

Plastering mud around the entrance hole affects the estimation of threat levels from nest predators in Eurasian Nuthatches

Background:For cavity-nesting birds,the nest entrance plays an important role in preventing predators from accessing nests.Several species of nuthatches use mud to narrow the entrance of cavities.In theory,the smaller the entrance hole size,the more effective it is against predators;however,few studies have tested whether narrowing the entrance hole size can affect the estimation of threat levels from nest predators in cavity-nesting birds.Methods:Using dummy experiments,we tested whether Eurasian Nuthatches(Sitta europaea,narrow the entrance hole of cavities)and Cinereous Tits(Parus cinereus,do not narrow the entrance hole,as a control)perform different nest defence behaviours against Common Chipmunks(Tamias sibiricus,small nest predator)and Red Squirrels(Sciurus vulgaris,larger nest predator).Results:Both nuthatches and tits exhibited stronger response behaviours(high dummy response scores)against chipmunks than against squirrels.Compared with tits,nuthatches exhibited more aggressive behaviours to chipmunks,but their responses to squirrels were similar.Conclusions:Nest defence behaviours of nuthatches to chipmunks differed from tits,and the results suggested that nuthatches might estimate threat levels of nest predators according to their narrowed entrance-hole size.

Shift in microhabitat use as a mechanism allowing the coexistence of victim and killer carnivore predators

It has been suggested that spatial heterogeneity is key to the coexistence at local spatial scales of subordinate and dominant predator species by allowing the former to shift to more protective habitats when the risk of intraguild predation exists. Here, we show how the smaller carnivore Egyptian mongoose (Herpestes ichneumon) may coexist on a local scale with its intraguild pre- dator, the Iberian lynx (Lynx pardinus), by using places with different microhabitat character- istics. We expect that mongooses living within lynx home ranges will use denser and more protective habitats when active in order to di- minish their risk of being killed by lynx com- pared to those living in areas similar in vege- tation and prey availability but where lynx are absent. The scrubland cover of points used by mongooses outside lynx areas, and that of points located within lynx areas but not used by mongooses, were significantly lower than, or similar to, cover of points used by mongooses within lynx areas. The probability of finding mon- goose tracks was constant across levels of scrubland cover when lynx were absent, but more mongoose tracks were likely to be found in thicker scrubland within lynx areas, especially if these areas were intensively used by lynx. This result agrees with the hypothesis on shifts in microhabitat use of subordinate carnivores to prevent fatal or risky encounters with dominant ones.

Botanicals, selective insecticides, and predators to control Diaphorina citri （Hemiptera： Liviidae） in citrus orchards

The Asian citrus psyllid （ACP） Diaphorina citri Kuwayama vectors pathogens that cause huanglongbing （HLB） or citrus greening devastating and economically im- portant disease present in most citrus growing regions. Young citrus shoots are required for psyllid reproduction and development. During winter citrus trees produce little or no new growth. Overwintering adults reproduce in spring on newly emerging shoots also attractive to other pests and beneficial insects. Botanicals and relatively selective insecti- cides could help to conserve beneficial insects and reduce pest resistance to insecticides. Sprays of Azadirachtin （Neem）, Tropane （Datura）, Spirotetramat, Spinetoram, and broad- spectrum Imidacloprid were evaluated to control ACP in spring and summer on 10-year-old ＂Kinow＂ Citrus reticulata Blanco trees producing new growth. Psyllid populations were high averaging 5-9 nymphs or adults per sample before treatment application. Nymphs or adults were significantly reduced to 0.5-1.5 per sample in all treatments for 3 weeks, aver- age 61%-83% reduction. No significant reduction in ladybeetles Adalia bipunctata, Ane- glei scardoni, Cheilomenes sexmaculata, and Coccinella septempunctata was observed. Syrphids, spiders and green lacewings were reduced in treated trees except with Tropane. Studies are warranted to assess impact of these predators on ACP and interaction with insecticides. Observed reduction in ACP populations may not be enough considering its reproductive potential and role in the spread of HLB. Follow-up sprays may be required to achieve additional suppression using rotations of different insecticides.

No evidence of predator odor avoidance in a North American bird community

Recent advances in our understanding of avian chemical communication have highlighted the importance of olfaction in many aspects of avian life.Prior studies investigating predator avoidance behaviors in response to predator odor cues have produced mixed results across species and contexts.Here we assess if a community of birds in eastern Pennsylvania displays avoidance behaviors towards predator odor cues in a natural foraging setting.We use clay caterpillars to measure foraging activity by birds in the presence of predator(bobcat)urine,non-predator(rabbit)urine,and water controls in two different environmental contexts(field vs.forest).Although we detected a weak trend for birds to forage less at predator urine-treated sites,we found no significant difference in avian foraging between the site types.We did find that foraging rates between environmental contexts changed significantly over the course of the experiment,with forest sites showing decreasing foraging rates and field sites showing increasing foraging rates.Our results reinforce the published literature that avoidance of predator odors by birds may not be ubiquitous across contexts and species.

Experimental clearance rate and intraguild predation of jellyfish Cyanea nozakii

Cyanea nozakii,a common jellyfish distributed in offshore China,has a complex trophic relationship with other zooplankton groups.However,few studies have reported the predation rates and prey selection patterns of C.nozakii medusae on different prey items.Research is also lacking on the intraguild predation of Aurelia coerulea(another common bloom jellyfish in offshore China)by C.nozakii.To address the knowledge gaps,the clearance rates of C.nozakii for different prey items,including copepods(small<1000μm and large>1000μm),fish larvae,and gelatinous prey(hydromedusae,A.coerulea ephyrae,and chaetognaths),were measured.The influence of predator size on the clearance rate was also determined.Additionally,we examined the intraguild predation of C.nozakii on A.coerulea medusae.The clearance rates of C.nozakii varied widely with prey organisms,being independent of prey concentrations.Gelatinous organisms,except for chaetognaths,were captured with considerably high efficiency,followed by fish larvae and copepods,indicating the preferential prey selection of gelatinous organisms by C.nozakii.The clearance rate increased linearly with the cross-sectional area of C.nozakii.Body size in medusae may,to some extents,underpin their capacity to capture more prey by increasing the encounter rate and capture success through ontogeny.C.nozakii preyed voraciously on A.coerulea in high feeding efficiency,but the clearance rate decreased with increasing A.coerulea(as prey)size.This phenomenon of intraguild predation suggests a speculative hypothesis of potential population regulation of A.coerulea by C.nozakii.The information regarding the feeding ecology of C.nozakii reported in this study is important for understanding plankton dynamics in marine ecosystems with extensive occurrences of this jellyfish.

When Fleeing Matters:Differences in Escape Behaviours of Three Northeast Asian Anurans

Prey species may have their own optimal escape strategy to balance predation risks and the energetic cost of fleeing.Some species have an advantage when maintaining a short fleeing distance,while others may favour an earlier escape based on microhabitat,size,or body condition.Here,we examined the escape behaviour of the three syntopic Northeast Asian anuran species:Mongolian toads(Strauchbufo raddei),Amur brown frogs(Rana amurensis),and Japanese treefrogs(Dryophytes japonicus)in Mongolia,Russia,China and DPR Korea.We examined flight initiation distance(FID;the distance from a potential predator to the point when the individual starts to flee)and distance fled(DF;distance between flight initiation and flight termination points)of each species and the effects of microhabitat,sex,and body size.Strauchbufo raddei and R.amurensis had a longer FID than D.japonicus,and S.raddei also had a longer DF than D.japonicus.These trends remained similar when dividing FID and DF by a size proxy(snout-vent length)for all individuals.This suggests that the treefrog D.japonicus used a strategy to stay immobile even when they were detected,and the toad S.raddei reacted quicker and more sensitively to predators despite the presence of toxin.Female S.raddei had a significantly longer FID than males suggesting that females are more sensitive to predation risk in this species,but body size was not significant for any of the three species.Our results indicate that the three sympatric species have different escaping strategies,likely related to differences in physiology and crypticity.

Encounters with aphid predators or their residues impede searching and oviposition by the aphid parasitoid Aphidius ervi （Hymenoptera： Aphidiinae）

Intraguild predation （IGP） can be an important factor influencing the effective- ness of aphid natural enemies in biological control. In particular, aphid parasitoid foraging could be influenced by the presence of predators. This study investigated the effect of larvae of the predatory hoverfly Episyrphus balteatus DeGeer （Diptera： Syrphidae） and the multicolored Asian ladybird Harmonia axyridis Pallas （Coleoptera： Coccinellidae） on the foraging behavior of the aphid parasitoid, Aphidius ervi Haliday （Hymenoptera： Aphidiidae） in choice experiments using a leaf disc bioassay. Wasp response to chemical tracks left by those predator larvae was also tested. Parasitoid behavior was recorded using the Observer （Noldus Information Technology, version 5.0, Wageningen, the Netherlands）. The experiments were conducted under controlled environmental conditions using leaves of the broad bean plant, Viciafaba L. （Fabaceae） with Myzus persicae Sulzer （Homoptera： Aphididae） as the host complex. A. ervi females avoided aphid patches when larvae of either predator were present. A similar avoidance response was shown by A. ervi to aphid patches with E. balteatus larval tracks, whereas no significant response was observed to tracks left by H. axyridis larvae. It was concluded that IG predator avoidance shown by the aphid parasitoid A. ervi may be a factor affecting their distribution among host patches.

Occurrence,profiles,and ecotoxicity of poly-and perfluoroalkyl substances and their alternatives in global apex predators:A critical review

Certain poly-and perfluoroalkyl substances(PFASs)exhibit significant bioaccumulation/biomagnification behaviors in ecosystems.PFASs,such as perfluorooctane sulfonate(PFOS),perfluorooctanoic acid(PFOA),perfluorohexanesulfonic acid(PFHxS)and related precursors,have elicited attention from both public and national regulatory agencies,which has resulted in worldwide restrictions on their production and use.Apex predators occupy the top trophic positions in ecosystems and are most affected by the biomagnification behavior of PFASs.Meanwhile,the long lifespans of apex predators also lead to the high body burden of PFASs.The high body burden of PFASs might be linked to adverse health effects and even pose a potential threat to their reproduction.As seen in previous reviews of PFASs,knowledge is lacking between the current stage of the PFAS body burden and related effects in apex predators.This review summarized PFAS occurrence in global apex predators,including information on the geographic distribution,levels,profiles,and tissue distribution,and discussed the trophic transfer and ecotoxicity of PFASs.In the case where legacy PFASs were restricted under international convention,the occurrence of novel PFASs,such as 6:2 chlorinated polyfluorinated ether sulfonate(6:2 Cl-PFESA)and perfluoroethylcyclohexane sulfonate(PFECHS),in apex predators arose as an emerging issue.Future studies should develop an effective analytical method and focus on the toxicity and trophic transfer behavior of novel PFASs.

Snakes that Snack on Poison Predators take venom from prey and use it themselves

动物学家发现,虎斑颈槽蛇通过吃一种分泌二烯羟酸内脂毒素的蟾蜍将毒素储存在身体内以抵御捕食者的危害。它会将毒素储存在颈背部,当遇到天敌鹰时通常拱起颈部,如受到威胁便会释放储存的毒素。但目前专家还没有研究出到底虎斑颈槽蛇是如何在不消化毒素的前提下将毒素储存起来并转移到毒腺里的,而毒素在其体内又经过了怎样的化学转变。

Scatterhoarding rodents favor higher predation risks for cache sites:The potential for predators to influence the seed dispersal process

Scatterhoarding rodents often place caches in the open where pilferage rates are reduced,suggesting that they tradeoff higher risks of predation for more secure cache sites.We tested this hypothesis in two study systems by measuring predation risks inferred from measures of giving-up densities(GUDs)at known cache sites and other sites for comparison.Rodent GUDs were measured with small trays containing 3 L of fine sand mixed with sunflower seeds.In the first experiment,we relied on a 2-year seed dispersal study in a natural forest to identify caches of eastern gray squirrels(Sciurus carolinensis)and then measured GUDs at:(i)these caches;(ii)comparable points along logs and rocks where rodent activity was assumed highest;and(iii)a set of random points.We found that GUDs and,presumably,predation risks,were higher at both cache and random points than those with cover.At the second site,we measured GUDs of eastern gray squirrels in an open park system and found that GUDs were consistently lowest at the base of the tree compared to more open sites,where previous studies show caching by squirrels to be highest and pilferage rates by naïve competitors to be lowest.These results confirm that predation risks can influence scatterhoarding decisions but that they are also highly context dependent,and that the landscape of fear,now so well documented in the literature,could potentially shape the temporal and spatial patterns of seedling establishment and forest regeneration in systems where scatterhoarding is common.

Loss of top predators and fragmentation lead to the decline of dominant plants in forests:a balance needed for conservation and management on overabundant large herbivore species

Portela and Dirzo(2020)recently reported a very interesting discovery,showing that forest fragmentation and defaunation resulted in a medium-sized monkey population outbreak,occurring in a predator-free forest fragment,which in turn led to the decline of a dominant plant Euterpe edulis(“palmito”).The scenario for this story is the infamously fragmented Brazilian Atlantic Forest hotspot.The researchers found that a native capuchin monkey(Sapajus nigritus)population has grown rapidly in recent decades,becoming hyper-abundant in fragments,concurrent with the local extinction of its predators,including Harpy eagle(Harpia harpyja).

Effects of grassland management, endophytic fungi and predators on aphid abundance in two distinct regions

Aims Fungal endophytes of cool-season grass species produce alkaloids toxic to herbivores,affecting food webs in agricultural and natural ecosystems.Field studies about the effects of endophytes on herbi-vores are rare and show contradictory results,leading to uncertain conclusions about the nature of endophyte-grass symbiosis.We asked whether the environmental contexts of local and regional scales and predation could modify the effects of endophytes on herbivores.Methods In a full factorial field experiment,we quantified the abundance of the aphid species Rhopalosiphum padi on the potted host grass Lolium perenne,which was either infected or uninfected with the endophytic fungus Neotyphodium lolii.Predators were either excluded or had free access to the pots with the aphids.One hun-dred and sixty grass pots were located in two regions on altogether 40 grassland sites,half of the sites intensively and half extensively managed.We tested the importance of endophyte infection,study region,management intensity of grasslands,predation and all two-way interactions on aphid abundance.Important Findings Endophyte infection reduced aphid abundance significantly in one study region only.In both regions,we found that the impacts of aphidophagous predators and grassland management intensity on aphid abundance were substantially stronger and more consistent than that of endophytes on aphid abundance.Pots excluding preda-tors and pots placed on extensive grasslands contained higher aphid abundance.The impact of predators and management on aphid abundance were not modified by the endophyte.We conclude that the effect of endophytes on herbivores can be weak in field experi-ments and depends on environmental context at a regional scale.Hence,more field research efforts are necessary to detect the rela-tive importance of endophytes and the environmental context on biotic interactions in ecosystems.