Historical and current climates affect the spatial distribution of herbivorous tree insects in China

Historical and current climate impacts reshape the evolutionary trajectory and ecological dynamics of entire vegetative communities,which can drive insect species distribution.Understanding the spatial distribution of insects can enhance forest management effectiveness.The effects of historical and current climates in the spatial distribution of herbivorous tree insects in China were explored.A species distribution model simulated insect spatial distribution based on 596 species and the distribution probability and richness of these species were assessed in forest ecoregions.The explanatory power of the historical climate was stronger than that of the current climate,particularly historical annual precipitation and annual mean temperatures,for the distribution of herbivorous insects.Under both historical and current climatic conditions,herbivorous tree insects were and are mainly distributed in the North China Plain and the middle and lower reaches of the Yangtze River Plain,namely in the Huang He Plain mixed forests,Changjiang Plain evergreen forests,and Sichuan Basin evergreen broadleaf forests.The Yunnan-Guizhou Plateau and northeast China are regions with large impact differences between historical and current climates.The findings of this study provide valuable insights into herbivorous insect responses to sustained climate change and may contribute to long-term biodiversity conservation activities.

Volatile metabolites of willows determining host discrimination by adult Plagiodera versicolora

Plagiodera versicolora Laicharting is a highly damaging leaf beetle foraging on willow leaves.In willow germplasm collections,observation has shown that Salix suchowensis Cheng was severely foraged by this leaf beetle while Salix triandra L.was damage free or only slightly damaged.Results of olfactometer bioassays show that the headspace volatiles from leaves of S.triandra significantly repelled adult beetles,suggesting that this species produces volatile repellents against P.versicolora.S.suchowensis had no effect on the beetles.Gas chromatography-mass spec-trometry was carried out to profile the headspace volatile organic compounds and 23 compounds from leaves of the alternate species in significantly different concentrations were detected.The effects of 20 chemical analogs on host discrimination were examined.Olfactory response to these chemicals showed that o-cymene,a S.suchowensis specific constituent,significantly attracted adult P.versicolora.In contrast,cis-3-hexenyl acetate,a constituent concentrated more in S.triandra than in S.suchowensis,significantly repelled beetles.Mixing o-cymene and cis-3-hexenyl acetate in comparable concentrations as in the volatiles of S.suchowensis demonstrated that the latter could mask the attracting effect of the former,causing a neutral response by adult beetles to leaves of S.suchowensis against clean air.In addition,chemical analogs have the same effect as plants when resembling volatile organic compounds in real samples.Two volatile metabolites were detected triggering host discrimination by one of the most damaging insect pests to host and non-host willows.The two metabolites are of considerable potential for use as olfactory signs in manag-ing the beetles.

Suppression Subtractive Hybridization Reveals Different Responses of Two Varieties of Gossypium arboreum L. Under Apolygus lucorum Stress

Plants reshape their transcriptomes, proteomes and metabolomes in response to insect damage. In this study, we used suppression subtractive hybridization to investigate the transcriptomes of two cotton varieties （CCRI41 and CCRI23） under Apolygus lucorum damage. From the CCRI23 libraries we obtained 92 transcripts and from the CCRI41 libraries we obtained 96 transcripts. 26 and 63 of the transcripts from CCRI23 and CCRI41, respectively, had known functions. Using reverse transcription PCR, we detected expression proifle of genes with known functions. Ultimately, we identiifed eight signiifcantly regulated genes, including one downregulated and four upregulated genes from the CCRI41 libraries, and one downregulated and two upregulated genes from the CCRI23 libraries. Only the gene encoding the polyphenol oxidase （PPO） is involved in plant defense against insect herbivores, and the others are related to improving tolerance to insect damage. Quantitative real-time PCR was used to study changes in expression levels during A. lucorum damage in CCRI23 and CCRI41. Signiifcantly regulated genes from CCRI23 showed a response in CCRI23 but not response in CCRI41. Similarly, signiifcantly regulated genes from CCRI41 showed a response in CCRI41 but not response in CCRI23. The results showed that, among transcriptomes of cotton varieties, there are different responses to A. lucorum damage.

Advances in research of induced resistance to insects in cotton

Any change in a plant that occurs following herbivory or environmental factors is an induced response.These changes include phytochemical induction,increases in physical defenses,emission of volatiles that attract predators and parasitoids of herbivores,and reduction in plant nutritional quality for herbivores,which is termed induced resistance.Induced resistance has been demonstrated ubiquitously in plants.It is one of our goals to review what is known about the induced resistance to herbivorous insects in cotton,including three resistance secondary metabolites(terpenoid,tannin,and flavonoids)that are contained at any significant levels of resistance to herbivorous insects in cotton cultivates.In many cases,the quantities or quality of secondary metabolites in plant are changed after attacked by insects.This review focuses on induced plant resistance as quantitative or qualitative enhancement of defense mechanism against insect pests,especially on the abiotic-elicitors-induced resistance in cotton plants.The abiotic-elicitor of cupric chloride,an exogenous inorganic compound,may induce the secondary metabolites accumulation and is referred to as a copperinducible elicitor(CIE).Finally,we discuss how copperinducible elicitor may be used in the Integrated Pest Management(IPM)system for cotton resistance control.

The evolutionary development of plant-feeding insects and their nutritional endosymbionts

Herbivorous insects have evolved diverse mechanisms enabling them to feed on plants with suboptimal nutrient availability. Low nutrient availability negatively impacts insect herbivore development and fitness. To overcome this obstacle numerous insect lineages have evolved intimate associations with nutritional endosymbionts. This is especially true for insects that specialize on nitrogen-poor substrates, as these insects are highly dependent on intraceUular symbionts to provide nitrogen lacking in their insect host＇s diet. Emerging evidence in these systems suggest that the symbiont＇s and/or the insect＇s biosynthetic pathways are dynamically regulated throughout the insect＇s development to potentially cope with the insect＇s changing nutritional demands. In this review, we evaluate the evolutionary development of symbiotic insect cells （bacteriocytes） by comparing and contrasting genes and mechanisms involved in maintaining and regulating the nutritional symbiosis throughout insect development in a diversity of insect herbivore-endosymbiont associations. With new advances in genome sequencing and functional genomics, we eval- uate to what extent nutritional symbioses are shaped by （i） the regulation of symbiont titer, （ii） the regulation of insect symbiosis genes, and （iii） the regulation of symbiont genes. We discuss how important these mechanisms are for the biosynthesis of essential amino acids and vitamins across insect life stages in divergent insect-symbiont systems. We conclude by suggesting future directions of research to further elucidate the evolutionary development of bacteriocytes and the impact of these nutritional symbioses on insect plant interactions.

Herbivores alleviate the negative effects of extreme drought on plant community by enhancing dominant species

Aims Both extreme drought and insect herbivores can suppress plant growth in grassland communities.However,most studies have examined extreme drought and insects in isolation,and there is reason to believe that insects might alter the ability of grasslands to withstand drought.Unfortunately,few studies have tested the interactive effects of extreme drought and insect herbivores in grassland communities.Methods Here,we tested the drought–herbivore interactions using a manipulative experiment that factorially crossed extreme drought with the exclusion of insect herbivores in a temperate semiarid grassland in Inner Mongolia.Important Findings Our results demonstrated that both extreme drought and insect herbivores separately decreased total plant cover.When combined,insect herbivores reduced the impact of drought on total cover by increasing the relative abundance of drought-resistant dominant species.Our results highlight that the negative effect of extreme drought on total plant cover could be alleviated by maintaining robust insect herbivore communities.

Aboveground herbivory increases soil nematode abundance of an invasive plant

Aims Plant invasions have the potential to affect the community structure of soil nematodes,but little is known about whether such effects are mediated by aboveground herbivores since invasive plants are not completely released from herbivores in the introduced range.In this study,we explored how aboveground insect herbivores mediated the effect of invasive plant Alternanthera philoxeroides on soil nematodes and examined the temporal variations of such an herbivory-elicited effect.Methods We conducted a greenhouse experiment by applying different herbivory treatments(no insect herbivores,specialist Agasicles hygrophila and generalist Cassida piperata)to potted A.philoxeroides,and then measured the community compositions of soil nematodes in corresponding pots on the 1st,10th and 20th day after removal of all herbivores.In addition,the carbon content of roots and root exudate of A.philoxeroides were also measured.Important Findings Our results showed that aboveground herbivory significantly increased the abundance of soil nematodes of A.philoxeroides,likely plant feeder nematodes,after insect herbivores were removed immediately(1st day).However,such impacts waned with time and there was no significant difference at later stages(10th and 20th days).Furthermore,the effects of specialist A.hygrophila and generalist C.piperata herbivory were consistent on the abundance of soil nematodes.Overall,our results suggest that aboveground insect herbivores have the potential to alter the effects of plant invasions on soil nematodes,but such impacts are transient.Furthermore,our study highlighted the importance of integrating the effects of above-and belowground organisms when evaluating the impacts of plant invasions.