Intraguild predation by polyps of three scyphozoan jellyfish:Nemopilema nomurai,Aurelia coerulea,and Rhopilema esculentum

Jellyfish blooms occur worldwide and have resulted in serious problems in tourism,fisheries,coastal industries,and the marine ecosystem.The life cycle of scyphozoan jellyfish consists of a pelagic medusa stage and a benthic polyp stage.Success of asexual reproduction of the polyps determines directly the number of medusae;thus,the polyp stage is the key to understanding the population dynamics of medusae.Nemopilema nomurai,Aurelia coerulea,and Rhopilema esculentum are three scyphozoan jellyfish commonly inhabit in Chinese coastal waters.Polyps of A.coerulea are easily visible,while those of N.nomurai and R.esculentum remain yet to be found in the wild.However,distribution of the medusa indicates that the polyps of all three species may occur together.To evaluate the distribution pattern of polyps of the three species and explore intraguild predation by the polyps,we conducted a laboratory experiment that considered the attachment sequence and size relationship of calyx diameter of the polyps.We found that the polyps of A.coerulea preyed on polyps of the other two species in all treatments,except when polyps of R.esculentum were bigger than those of A.coerulea.The polyps of R.esculentum preyed on the polyps of N.nomurai only when polyps of R.esculentum attached first and were bigger than those of N.nomurai.Colonies of N.nomurai polyps were rarely found in the places inhabited by A.coerulea polyps.In addition,A.coerulea polyps are known to inhabit at depths of less than 20 m in coastal sea,thus,we speculate that N.nomurai polyp colonies might occur at depths of more than 20 m.Therefore,our finding that polyps of A.coerulea aggressively preyed on polyps of other species may help understand other such systems of jellyfish bloom in the world.

Stability and bifurcation analysis of a tri-trophic food chain model with intraguild predation

The dynamics of a three-component model for food web with intraguild predation isconsidered. The model is based on the collection of ordinary differential equations thatdescribe the interactions among prey, intermediate predator and top predator. First,the model without self-limitation of the predators is studied. Boundedness of the systemand existence of non-negative solutions are established. The local stability analysisof the equilibria is carried out to examine the behavior of the system. The possibilityof Hopf bifurcation around non-negative equilibria with consumption rates as bifurcationparameters is studied. Center manifold theorem and the normal form theory areapplied to obtain the formulas for determining the direction of Hopf bifurcation and thestability of bifurcating periodic solutions. Numerical simulations support the analyticalfindings, which show that the extinction of one of the predators can occur under certainrestrictions on the predation rate of the top predator. Subsequently, numerical analysisof the model with self-limitation of the predators is carried out. Simulations reveal thatthe system with intraspecific competition in the predator populations can reproducecoexistence between the three species in resource-rich environment.

Oviposition behavior of the mirid Macrolophus pygmaeus under risk of intraguild predation and cannibalism

Zoophytophagous mirid species,that feed and develop either on prey or plant resources,are often found simultaneously on the same host.Hence,these species can engage in both intraguild predation and cannibalism,which can pose a threat to mirid eggs.Ovipositing females may respond to such risks of predation on their eggs by reducing the number of eggs laid or selecting safer oviposition sites.We tested the oviposition behavior of Macrolophus pygmaeus(Rambur)(Hemiptera:Miridae)females under the risk of cannibalism by M.pygmaeus males and intraguild predation by Nesidiocoris tenuis(Reuter)males(Hemiptera:Miridae)under laboratory conditions.Intraguild predators and cannibals were introduced during or after the oviposition period.The number of eggs laid(using counts of newly hatched nymphs)and their proportion on each part of a tomato plant were both measured.The results reveal that only cannibalism by M.pygmaeus males after the period of oviposition significantly decreased the number of hatched eggs.Cannibalism thus represents a greater risk to mirid eggs than intraguild predation.The M.pygmaeus female responded to the presence of potential intraguild predators(or competitors)by decreasing the nu mber of eggs laid in the upper leaves.The results suggest that M.pygmaeus females avoid competition by N.tenuis,by laying fewer eggs on upper leaves.Cannibalism could regulate zoophytophagous predator populations under prey scarcity conditions and minimize the risk of crop damage associated with those biological control agents.

Traveling wave solutions for a diffusive three-species intraguild predation model

The aim of this work is to investigate the existence and non-existence of traveling wave solutions for a diffusive three-species intraguild predation model which means that one predator can eat its potential resource competitors. The method of upper-lower solution is implemented to show the existence of traveling wave solutions. In order to simplify the construction of an admissible pair of upper lower solution, the scheme of strictly con- tracting rectangle is applied. Finally, the minimal speed c＊ of traveling wave solutions of the model is characterized. If the wave speed is greater than c＊, we show the exis- tence of traveling wave solutions connecting trivial and positive equilibria by combining the upper and lower solutions with the contracting rectangle. On the other hand, if the wave speed is less than c＊, the non-existence of such solutions is also established. Furthermore, to illustrate our theoretical results, some numerical simulations are performed and biological meanings are interpreted.

Interactions between Entomopathogenic Fungi and Entomophagous Insects

Direct treatment of predators with entomopathogenic fungi (EPF) at different concentrations revealed that some species, like Beauveria bassiana and Metarhizium anisopliae, were found to have detrimental effects on all developmental stages of some predator species. Other species, like Numoraea rileyi and Paecilomycis fumosorosius, showed little or no effect on treated predators. Adult predators were found to avoid feeding on fungi-infected prey. EPF could be isolated from hibernating or field-collected coccinellids. Some studies indicated that combining a fungus with a predator could increase the rate of insect control in the field. As for parasitoids, this review indicates that the developmental stages of the egg parasitoids can develop successfully in host eggs treated with fungi. However, fungus-infected hosts negatively impact the development of larval parasitoids inside such hosts and this impact depends on the species and concentration of the fungus as well as the time between infection and parasitism. Some parasitoid females can discriminate between fungus-infected and uninfected hosts and do not parasitize the infected hosts. With appropriate timing, the parasitoids or predators could be combined with fungi for the biological control of insects in the field.

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.

Evolutionary ecology of microsporidia associated with the invasive ladybird Harmonia axyridis

Invasive species are characterized by the rapid growth and spread of their populations after establishing a foothold in new habitats, and there are now many examples of such species negatively affecting biodiversity and the economy. It is unclear why some species can become successful invaders, whereas most （even if closely related） remain noninvasive. We previously proposed a hypothesis that parasites associated with invading species can promote their invasive success if they are harmless toward the invaders but harmful to their competitors and/or predators in the newly colonized habitat. Here we discuss whether microsporidia that have recently been discovered in the invasive ladybird Harmonia axyridis contribute to its invasive success. We show that all H. axyridis beetles sourced from diverse collection sites all over the world carry abundant microsporidia. This suggests that both native and invasive H. axyridis populations are associated with these tolerated parasites, which were likely to have existed in native populations before expansion rather than being acquired in newly colonized areas. We describe the pathogenesis of the microsporidia during different developmental stages of H. axyridis and we address the possibility that the predation of its infected eggs and larvae by competing native ladybird species may lead to their infection and ultimately to their decline. Finally, we discuss our initial hypothesis： microsporidia that are tolerated by an invasive vector insect can be active against susceptible native competitors and/or predator species.

Effects of mummy consumption on fitness and oviposition site selection on Harmonia axyridis

Intraguild predation(IGP)has been commonly reported between predators and parasitoids used as biological control agents as predators consuming parasitoids within their hosts.However,the effect of parasitoid-mummy consumption on the fitness of the predator and subsequent oviposition site selection have not been well studied.In our study,we conducted two laboratory experiments to examine the influence of Aphidius gifuen-sis Ashmead(Hymenoptera:Braconidae)mummies as prey on fitness and subsequently oviposition site selection of Harmonia axyridis(Pallas)(Coleoptera:Coccnellidae).Re-sults indicate that when H.aryridis was reared on A.gifiuensis mummies only,its larval development was prolonged,and body weight of the 4th instar larvae and newly emerged adults,and fecundity decreased.Moreover,H.axyridis did not exhibit oviposition pref-erence on plants infested with unparasitized aphids or aphids parasitized for shorter than 9 days.However,compared with plants with mummies(parasitized≥9 days),H.axryridis laid more eggs on plants with unparasitized aphids.In contrast,H.axryridis previously fed with A.gifuensis mummies did not show a significant oviposition preference between plants with unparasitized aphids and those with mummies(parasitized≥9 days).Overall,our results suggest that mummy consumption reduced the fitness of H.axyridis.Although H.axyridis avoided laying eggs on plants with A.gifuensis mummies,prior feeding ex-perience on A.gifuensis mummies could alter the oviposition site preference.Thus,in biological control practice,prior feeding experience of H.axyridis should be carflly considered for reduction of IGP and increase of fitness of H.axyridis on A.gifuensis.

Optimal harvesting of a prey-predator model with variable carrying capacity

This work deals with a prey-predator model in an environment where the carrying capacities are assumed to be variable with time and one species feeds upon the other. Independent harvesting efforts are applied in either species and asymmetrical intraguild predation occurs. A common resource is consumed by two competing species and at the same time predator also consumes the prey. At first we discuss the model under constant carrying capacity and make the conclusion that no limit cycle exists in this case. Then we discuss the model without intraspecific competition. Our main concern is to cover the above mentioned two cases together, i.e. the model with variable carrying capacity and intraspecific competition. We determine the steady states and examine the dynamical behavior. We also analyze the local and global stability of the interior equilibrium by Routh-Hurwitz criterion and a suitable Lyapunov function respectively. A Hopf bifur- cation occurs with respect to a parameter which is the ratio of predator＇s and prey＇s intrinsic growth rate. The possibility of bionomic equilibrium has been considered. The optimal harvest policy is formulated and solved with Pontryagin＇s maximum principle. Some numerical simulations are given to explain most of the analytical results.

Survival, development and life tables of two congeneric ladybirds in aphidophagous guilds

Two congeneric aphidophagous ladybirds, Coccinella septempunctata and Coccinella transversalis, were reared on three aphid species, Lipaphis erysimi, Myzus persicae and Aphis nerii, to estimate the effect of prey quality and intra- and interspecific interactions on their survival and development of life stages. Mortality of first instar ladybirds of both species was highest feeding on A. nerii. Preimaginal mortafity was lowest when feeding on L. erysimi （C. septempunctata, 1.6% and C. transversalis, 3.2%）, and highest when feeding on A. nerii （ C. septempunctata, 6.2% and C. transversalis, 8.2%）. Comparatively higher weight and larger size of C. septempunctata along with the lower levels of mortality recorded suggested that it is more likely to have acted as an intraguild predator than C. transversalis. High recorded mortality of C. transversalis is attributed to probable intraguild predation on account of its smaller size. The major sources of mortality were probably cannibalism, intraguild predation and other unknown factors. Lower prey quality increased the incidence of cannibalism and intraguild predation, especially in C. transversalis. The investigation suggests an intrinsic competitive advantage for C. septempunctata over C. transversalis in guilds of three aphid species.

Fitness costs of reflex bleeding in the ladybird beetle Harmonia axyridis: the role of parental effects

Reflex bleeding is an important antipredator defense mechanism in Coccinellidae.We examined the costs of reflex bleeding in larval and adult stages of the ladybird beetle Harmonia axyridis on offspring fitness and reproductive performance through the comparisons between bled and control larvae,reciprocal crosses of bled/control beetles,and early and late clutch phenotypes.Beetles bled during their larval stage spent a longer time in development and weighed less than controls.Egg fertility was reduced for crosses where either one or both parents had been bled during the larval or adult stage.Offspring crosses that included a parent bled during the larval stage suffered fitness costs in development and female body mass,while those bled during the adult stage suffered no transgenerational costs.Males that suffered bleeding during their larval stage accelerated progeny development of nonbled females in early clutches,suggesting a positive transgenerational effect of larval bleeding,while males that did not suffer bleeding accelerated progeny development of bled females in later clutches.As the underlying effects of bleeding on females'offspring in the early clutches were diminished in the late ones,suggesting another transgenerational effect.The strengths of maternal and paternal effects on progeny development of parents bled at the larval stage were higher in earlier clutches.This study suggests that H.axyridis adults are less affected than larvae by the frequent use of the defensive secretions in their stressful habitats.

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.

Body temperature,activity patterns and hunting in free-living cheetah:biologging reveals new insights

As one of the few felids that is predominantly diurnal,cheetahs(Acinonyx jubatus)can be exposed to high heat loads in their natural habitat.Little is known about long-term patterns of body temperature and activity(including hunting)in cheetahs because long-term concurrent measurements of body temperature and activity have never been reported for cheetahs,or,indeed,for any free-living felid.We report here body temperature and locomo-tor activity measured with implanted data loggers over 7 months in 5 free-living cheetahs in Namibia.Air tem-perature ranged from a maximum of 39°C in summer to−2°C in winter.Cheetahs had higher(~0.4°C)max-imum 24-h body temperatures,later acrophase(~1 h),with larger fluctuations in the range of the 24-h body temperature rhythm(approximately 0.4°C)during a hot-dry period than during a cool-dry period,but main-tained homeothermy irrespective of the climatic conditions.As ambient temperatures increased,the cheetahs shifted from a diurnal to a crepuscular activity pattern,with reduced activity between 900 and 1500 hours and increased nocturnal activity.The timing of hunts followed the general pattern of activity;the cheetahs hunted when they were on the move.Cheetahs hunted if an opportunity presented itself;on occasion they hunted in the midday heat or in total darkness(new moon).Biologging revealed insights into cheetah biology that are not ac-cessible by traditional observer-based techniques.