Chemical cues from kingsnakes do not cause inducible defenses in house mice

Abstract Many rodents exhibit inducible defenses when exposed to chemical cues from mammalian predators. These responses may include delays in sexual maturation, smaller adult body size and decreases in litter size and pup weight. We exposed the hybrid juvenile offspring of field-caught and lab-descended house mice Mus musculus to the chemical cues of mouse-fed or chick-fed kingsnakes, Lampropeltis getula, for 20 days after weaning, to examine the effects of ophidian predator cues on prey development. We hypothesized that these cues would elicit inducible defenses such as alteration of growth rates, and/or the timing of reproductive development in mice. Once mature, the reproductive effort of the mice might also be impacted by producing smaller litter sizes or lighter pups or not reproducing at all. We found no effect of kingsnake cues on any of the measures. These findings support the hypothesis that inducible defenses may have evolved as a strategy to deal with specific predators.

Preliminary studies on differential defense responses induced during plant communication

We compared the expression patterns of three representative genes in undamaged tomato and tobacco plants in response to exposure to either tomato or tobacco fed on by Helicoverpa armigera (cotton bollworm). When tomato and tobacco, two species of one family, were incubated in the chambers with the tomato plants damaged by the cotton bollworm, the expression of the PR1, BGL2, and PAL genes was up-regulated in leaves of both plants. However, the levels of gene expression were significantly higher in the tomato than that in the tobacco. In addition, the activities of enzymes, peroxidase, polyphenol oxidase, and lipoxygenase were found to be higher in the tomato than those in the tobacco. Similar results were obtained when the damaged plants were replaced by the tobacco.

Alarm cue induces an antipredator morphological defense in juvenile Nicaragua cichlids Hypsophrys nicaraguensis

Olfactory cues that indicate predation risk elicit a number of defensive behaviors in fishes, but whether they are sufficient to also induce morphological defenses has received little attention. Cichlids are characterized by a high level of morphological plasticity during development, and the few species that have been tested do exhibit defensive behaviors when exposed to alarm cues released from the damaged skin of conspecifics. We utilized young juvenile Nicaragua cichlids Hypsophrys nicaraguensis to test if the perception of predation risk from alarm cue （conspecific skin extract） alone induces an increased relative body depth which is a defense against gape-limited predators. After two weeks of exposure, siblings that were exposed to conspecific alarm cue increased their relative body depth nearly double the amount of those exposed to distilled water （control） and zebrafish Danio rerio alarm cue. We repeated our measurements over the last two weeks （12 and 14） of cue exposure when the fish were late-stage juveniles to test if the rate of increase was sustained; there were no differences in final dimensions between the three treatments. Our results show that 1） the Nicaragua cichlid has an innate response to conspecific alarm cue which is not a generalized response to an injured fish, and 2） this innate recognition ultimately results in developing a deeper body at a stage of the life history where predation risk is high [Current Zoology 56 （1）： 36-42, 2010].

The influence of Tetranychus cinnabarinus-induced plant defense responses on Aphis gossypii development

Carmine spider mites （Tetranychus cinnabarinus） and cotton aphids （Aphis gossypii） are both serious pests of cotton, and cause reductions in yields of this key agricultural crop. In order to gain insights into how plant defense responses induced by one herbivore species affect the behavior and performance of another, we examined how infestation with T. cinnabarinus influences the development of A. gossypfi using cotton as a model. In this study, we measured the activities of several important biochemical markers and secondary metabolites in the leaves of cotton seedlings responding to infestation by T. cinnabarinus. Furthermore, the influences of T. cinnabarinus infestation on the development ofA. gossypfi in cotton were also examined. Our data showed that the activities of several key defense enzymes, including phenylalanine ammonia-lyase （PAL）, peroxidase （POD）, lipoxygenase （LOX）, and polyphenol oxidase （PPO）, were substantially increased in cotton seedlings responding to spider mite infestation. Further, the contents of gossypol and condensed tannins, key defensive compounds, were significantly enhanced in leaves of cotton seedlings following T. cinnabarinus infestation. Moreover, the T. cinnabarinus-induced production of defense enzymes and secondary metabolites was correlated with infestation density. The developmental periods of A. gossypii on cotton seedling leaves infested with T. cinnabarinus at densities of 10 and 15 individuals cm-2 were 1.16 and 1.18 times that of control, respectively. Meanwhile, the mean relative growth rates of A. gossypfi on cotton leaves infested with T. cinnabarinus at densities of 8, 10 and 15 individuals cm-2 were significantly reduced. Therefore, these data suggested that the developmental periods of A. gossypfi were significantly lengthened and the mean relative growth rates were markedly reduced when cotton aphids were reared on plants infested with high densities of spider mites. This research sheds light on the role that inducible defense responses played in plant-mediated interspecific interactions between T. cinnabarinus and A. gossypfi.

Jasmonate- and salicylate-induced defenses in wheat affect host preference and probing behavior but not performance of the grain aphid, Sitobion avenae

Jasmonate and salicylatemediated signaling pathways play significant roles in induced plant defenses, but there is no sufficient evidence for their roles in monocots against aphids. We exogenously applied methyl jasmonate （MeJA） and salicylic acid （SA） on wheat seedlings and examined biochemical responses in wheat and effects on the grain aphid, Sitobion avenae （Fab.）. Application of MeJA significantly increased levels of wheat＇s polyphenol oxidase, peroxidase and proteinase inhibitor 1, 2 and 6 days after treatment. In twochoice tests, adult aphids preferred control wheat leaves to MeJA or SA treated leaves. Electrical penetration graph （EPG） recordings of aphid probing behavior revealed that on MeJAtreated plants, the duration of aphid＇s first probe was significantly shorter and number of probes was significantly higher than those on control plants. Also total duration of probing on MeJAtreated plants was significantly shorter than on control plants. Total duration of salivation period on SAtreated plants was significantly longer, while mean phloem ingestion period was significantly shorter than on control plants. However, no significant difference in total duration of phloem sap ingestion period was observed among treatments. The EPG data suggest that MeJAdependent resistance factors might be due to feeding deterrents in mesophyll, whereas the SAmediated resistance may be phloembased. We did not observe any significant difference of MeJA and SA application on aphid development, daily fecundity, intrinsic growth rate and population growth. The results indicate that both MeJA and SAinduced defenses in wheat deterred S. avenae colonization processes and feeding behavior, but had no significant effects on its performance.

The evolutionary strategies of plant defenses have a dynamic impact on the adaptations and interactions of vectors and pathogens

Plants have evolved and diversified to reduce the damages imposed by in- fectious pathogens and herbivorous insects. Living in a sedentary lifestyle, plants are constantly adapting to their environment. They employ various strategies to increase per- formance and fitness. Thus, plants developed cost-effective strategies to defend against specific insects and pathogens. Plant defense, however, imposes selective pressure on in- sects and pathogens. This selective pressure provides incentives for pathogens and insects to diversify and develop strategies to counter plant defense. This results in an evolution- ary arms race among plants, pathogens and insects. The ever-changing adaptations and physiological alterations among these organisms make studying plant-vector-pathogen interactions a challenging and fascinating field. Studying plant defense and plant protec- tion requires knowledge of the relationship among organisms and the adaptive strategies each organism utilize. Therefore, this review focuses on the integral parts of plant-vector- pathogen interactions in order to understand the factors that affect plant defense and disease development. The review addresses plant-vector-pathogen co-evolution, plant defense strategies, specificity of plant defenses and plant-vector pathogen interactions. Improving the comprehension of these factors will provide a multi-dimensional perspective for the future research in pest and disease management.

Survival in spatially variable thermal environments:Consequences of induced thermal defense

As Earth’s climate warms,plants and animals are likely to encounter increased frequency and severity of extreme thermal events,and the ensuing destruction is likely to play an important role in structuring ecological communities.However,accurate prediction of the population-scale consequences of extreme thermal events requires detailed knowledge of the small-scale interaction between individual organisms and their thermal environment.In this study I propose a simple model that allows one to explore how individual-to-individual variation in body temperature and thermal physiology determines what fraction of a population will be killed by an extreme thermal event.The model takes into account the possibility that each individual plant or animal can respond to an event by adjusting its thermal tolerance in proportion to the stress it encounters.When thermal stress is relatively mild,the model shows that a graded physiological response of this sort leads to increased survivorship.However,the model predicts that in more severe events a proportional induced defense can actually reduce survivorship,a counterintuitive possibility that is not predicted by standard theory.The model can easily be tailored to different species and thermal environments to provide an estimate of when,where and how physiology can buffer the effects of climate warming.

The effects of cues from kingsnakes on the reproductive effort of house mice

It is not clear if rodents express inducible defenses in response to reptilian predators such as snakes. We tested the hypothesis that adult house mice Mus musculus decrease aspects of their reproductive effort upon 1 hour of exposure every 48 hours for a 25-day period to the fecal material and shed skins of a euryphagous ophidian predator, the kingsnake Lampropeltis getula, that had been fed mice. We found no significant differences in the total number of offspring born, the number of pups per litter, and the mean weight of pups in litters born to male and female mice that were exposed to predator cues and those mice that were not exposed to such cues. The lack of an inducible response may be associated with the low cost of an effective defense, or the lack of an effective defense against a generalist snake predator [Current Zoology 59 （1）： 135-141, 2013].

Predator-induced physiological responses in tadpoles challenged with herbicide pollution

Predators induce plastic responses in multiple prey taxa, ranging from morphological to behavioral or physiological changes. In amphibians, tadpoles activate plastic responses to reduce predation risk by reducing their activity rate and altering their morphology, specifically tail depth and pigmentation. Furthermore, there is now evidence that tadpoles＇ defenses are modi- fied when predators combine with other stressful factors such as pollutants or competitors, but our knowledge on the physiologi- cal responses underlying these responses is still scarce. Here we study physiological responses in Pelobates cultripes tadpoles exposed to a natural predator （larvae of the aquatic beetle Dytiscus circumflexus）, non-lethal concentrations of herbicide （gly- phosate, 0.5 mg/L and 1.0 mg/L） or both factors combined. We measured corticosterone levels, standard metabolic rate, oxidative damage （TBARS） and activity of antioxidant enzymes, and immune response （via leukocyte count）. Tadpoles reduced their corti- costerone concentration by ca. 24% in the presence of predator cues, whereas corticosterone did not change in the presence of glyphosate. Two enzymes involved in antioxidant response also decreased in the presence of predators （14.7% and 13.2% respec- tively） but not to glyphosate. Herbicide, however, increased the number of neutrophils and reduced that of lymphocytes, and had an interaction effect with predator presence. Standard metabolic rate did not vary across treatments in our experiment. Thus we show a marked physiological response to the presence of predators but little evidence for interaction between predators and low levels of herbicide. Multiple assessment of the physiological state of animals is important to understand the basis and conse- quences ofphenotypic plasticity

Arbuscular mycorrhizal fungi are necessary for the induced response to herbivores by Cucumis sativus

Aims Although ecological interactions are often conceptualized and stud-ied in a pairwise framework,ecologists recognize that the outcomes of these interactions are influenced by other members of the com-munity.Interactions(i)between plants and insect herbivores and(I)between plants and mycorrhizal fungi are ubiquitous in terrestrial ecosystems and may be linked via common host plants.Previous studies suggest that colonization by arbuscular mycorrhizal fungi(AMF)can modifty plants'induced responses to herbivore attack,but these indirect effects of fungal symbionts are poorly understood.I investigated the role of AMF in induced plant response to a gen-eralist herbivore.Methods|manipulated AMF status and herbivory in Cucumis sativus L.(cucumber,Cucurbitaceae)in a greenhouse to investigate induced responses in the presence and absence of the mycorrhi-zal fungus Glomus intraradices(Glomeraceae).Spodoptera exigua Habner(Noctuidae)were used to manipulate prior damage and later as assay caterpillars.I also measured G.intraradices and her-bivory effects on plant N and effects on plant growth.Impor tant Findings AMF status affected the induced response of C.sativus,underscor-ing the importance of incorporating the roles of plant symbionts into plant defense theory.Assay caterpillars ate significantly more leaf tissue only on mycorrhizal plants that had experienced prior damage.Despite more consumption,biomass change in these cat-erpillars did not differ from those feeding on plants with other treat-ment combinations.Leaf N content was reduced by G.intraradices but unaffected by herbivory treatments,suggesting that the observed differences in assay caterpillar feeding were due to changes in defensive chemistry that depended on AMF.

APPLICATION AND DEVELOPMENT OF ‘GREEN’ PREVENTIVE AND CONTROL TECHNOLOGIES IN GUIZHOU TEA PLANTATIONS

The application and development of ‘green’ preventive technologies in teaplantations is an important means of ensuring tea quality and ecologicalsafety. Ecological, agronomic and biological controls are the main preventivemeasures used in Guizhou Province. This paper summarizes the ‘green’preventive technologies being applied in Guizhou tea plantations, including theuse of plant defense inducers to regulate tea plant responses to pathogens,natural enemies to control pest species causing damage to shoots andTrifolium repens to control the main weed species. In addition, it summarizesthe integrated ‘green’ preventive technologies being used in Guizhou andprovides a foundation for the ecological maintenance of tea plantations.

Herbivore-induced rice resistance against rice blast mediated by salicylic acid

In agro-ecosystems,plants are important mediators of interactions between their associated herbivorous insects and microbes,and any change in plants induced by one species may lead to cascading effects on interactions with other species.Often,such effects are regulated by phytohormones such as jasmonic acid(JA)and salicylic acid(SA).Here,we investigated the tripartite interactions among rice plants,three insect herbivores(Chilo suppressalis,Cnaphalocrocis medinalis or Nilapai-vata lugens),and the causal agent of rice blast disease,the fungus Magnaporthe oryzae.We found that pre-infestation of rice by C.suppressalis or N.lugens but not by C.medinalis conferred resistance to M.oryzae.For C.suppressalis and N.lugens,insect infestation without fungal inoculation induced the accumulation of both JA and SA in rice leaves.In contrast,infestation by C.medinalis increased JA levels but reduced SA levels.The exogenous application of SA but not of JA conferred resistance against M.oryzae.These results suggest that preinfestation by C suppressalis or N.lugens conferred resistance against M.oryzae by increasing SA accumulation.These findings enhance our understanding of the interactions among rice plant,insects and pathogens,and provide valuable information for developing an ecologically sound strategy for controlling rice blast.

Vole preference of bilberry along gradients of simulated moose density and site productivity

Browsing by large herbivores might either increase or decrease preference for the plant by other herbivores,depending on the plant response.Using a cafeteria test,we studied the preference by root voles(Microtus oeconomus[Pallas,1776])for bilberry(Vaccinium myrtillus L.)previously subjected to 4 levels of simulated moose(Alces alces[Linnaeus,1758])density.The different levels of moose density were simulated at population densities relevant for Fennoscandian conditions,in exclosures situated along a site productivity gradient.We expected:(i)voles to prefer bilberry from high productivity sites over low productivity sites;(ii)voles to prefer browsed bilberry,if plants allocate resources to compensatory growth or to avoid browsed bilberry if plants allocate resources to defense;(iii)these effects to increase with increasing simulated moose density;and(iv)the concentration of plant chemicals and the plant morphology to explain vole preference.Specifically,we predicted that voles would prefer:(i)plants with high nitrogen content;(ii)plants with low content of defensive substances;and(iii)tall plants with long shoots.Voles preferred bilberry from the high productivity sites compared to the low productivity sites.We also found an interaction between site productivity and simulated moose density,where voles preferred unbrowsed plants at low productivity sites and intermediate levels of browsing at high productivity sites.There was no effect of plant chemistry or morphology on vole preference.We conclude that moose browsing impacts the food preference of voles.With the current high densities of moose in Fennoscandia,this could potentially influence vole food selection and population dynamics over large geographical areas.