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Disparities in nutrient content (nitrogen and phosphorus) between herbivores and their plant resources have lately proven to have major consequences for herbivore success, consumer-driven nutrient cycling, and the fate of primary production in ecosystems. Here we extend these findings by examining patterns of nutrient content between animals at higher trophic levels, specifically between insect herbivores and predators. Using a recently compiled database on insect nutrient content, we found that predators exhibit on average 15% greater nitrogen content than herbivores. This difference persists after accounting four variation from phylogeny and allometry. Among herbivorous insects, we also found evidence that recently derived lineages (e.g., herbivorous Diptera and Lepidoptera) have, on a relative basis, 15-25% less body nitrogen than more ancient herbivore lineages (e.g., herbivorous Orthoptera and Hemiptera). We elaborate several testable hypotheses for the origin of differences in nitrogen content between trophic levels and among phylogenetic lineages. For example, interspecific variation in insect nitrogen content may be 1) directly traceable to differences in dietary nitrogen (including dilution by gut contents), 2) selected for directly in response to the differential scarcity of dietary nitrogen, or 3) an indirect consequence of adaptation to different feeding habits. From some functional perspectives, the magnitude rather than the source of the interspecific differences in nitrogen content may be most critical. These findings have implications for both the trophic complexity of food webs and the evolutionary radiation of herbivorous insects.

The successional dynamics of arthropod diversity in 18 abandoned agricultural fields (age 15-54 years) at Cedar Creek, MN, USA were determined using sweep net sampling (44,833 individuals of 618 species). Total arthropod species richness and equitability (J), but not abundance, increased significantly with field successional age. Herbivore and parasite species richness, but not detritivore and predator speciesrichness, also increased significantly with field age. All of these arthropod variables were significantly positively correlated with plant species richness in the fields. When plant species richness was included as a covariate in regressions, there were no longer any significant effects of field age. These results supported the hypothesis that increases in arthropod diversity with field age are influenced by increases in plant diversity. The additional significant positive dependence of herbivore species richness on predator species richness suggests that predator-prey interactions may also influence the successional dynamics of arthropod diversity. Nine of the ten most common arthropod species decreased in abundance with field age, two of them significantly. The abundances of these two generalist forb-feeding species, Melanoplus femurrubrum (Orthoptera: Acrididae) and Scaphytopius acutus (Homoptera: Cicadellidae), each depended significantly on amount of forbs. The average body size of arthropod species (total and herbivores) decreased significantly with field age. An efficiency vs. specialization hypothesis predicts such a decrease. Because plants in later secondary succession are generally less palatable, a diversity of smaller, potentially more specialized herbivores may have an advantage over larger and more efficient herbivores in later succession. [ABSTRACT FROM AUTHOR]

Biodiversity is increasingly threatened by local extinction under global climate change. This may reflect direct effects of climate on poorly adapted native species or increased impacts of exotic species in these conditions, but their relative importance is poorly understood. By examining global occurrence records of 142 plant species found in the Yangtze River Valley, we found that the climatic niches of exotic species differed from those of natives, mainly reflecting exotics being most common in warmer, drier and more isothermal climates in their native ranges. These differences in climatic niches, especially temperature, predicted invasion intensity in 459 plots along a 1,800-km transect in the Yangtze River Valley. On the basis of this strong match between model predictions and field survey results, we predict that invasions will probably be more intense in future climatic conditions, especially from warming at the coldest sites. The direct negative effect of warming on native diversity was larger than the indirect effects mediated through increased invasions. However, moderate invasion increased communities' overall species diversity. More broadly, our study highlights the role of exotic species in the ecological response of regional biodiversity to global climate change., (© 2024. The Author(s).)

Plants from invasive populations often have higher growth rates than conspecifics from native populations due to better environmental adaptability. However, the roles of improved chlorophyll fluorescence or antioxidant defenses in helping them to grow better under adverse situations are insufficient, even though this is a key physiological question for elucidating mechanisms of plant invasion. Here, we conducted experiments with eight native (China) and eight introduced (USA) populations of Chinese tallow tree ( Triadica sebifera ). We tested how salinity, nutrients (overall amount or N:P in two separate experiments) and their interaction affected T. sebifera aboveground biomass, leaf area, chlorophyll fluorescence and antioxidant defenses. Plants from introduced populations were larger than those from native populations, but salinity and nutrient shortage (low nutrients or high N:P) reduced this advantage, possibly reflecting differences in chlorophyll fluorescence based on their higher PSII maximum photochemical efficiency ( F v / F m ) and PSI maximum photo-oxidizable P700 in higher nutrient conditions. Native population plants had lower F v / F m with saline. Except in high nutrients/N:P with salinity, introduced population plants had lower electron transfer rate and photochemical quantum yield. There were no differences in antioxidant defenses between introduced and native populations except accumulation of hydrogen peroxide (H 2 O 2 ), which was lower for introduced populations. Low nutrients and higher N:P or salinity increased total antioxidant capacity and H 2 O 2 . Our results indicate that nutrients and salinity induce differences in H 2 O 2 contents and chlorophyll fluorescence characteristics between introduced and native populations of an invasive plant, illuminating adaptive mechanisms using photosynthetic physiological descriptors in order to predict invasions., Competing Interests: None declared., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Annals of Botany Company.)

Invasive plants typically escape specialist herbivores but are often attacked by generalist herbivores in their introduced ranges. The shifting defense hypothesis suggests that this will cause invasive plants to evolve lower resistance against specialists, higher resistance against generalists, and greater tolerance to herbivore damage. However, the duration and direction of selective pressures can shape the evolutionary responses of resistance and tolerance for invasive plants. Two critical factors are (1) residence time (length of time that an invasive species has been in its introduced range) and (2) specialist herbivore reassociation (attack by purposely or accidentally introduced specialists). Yet, these two factors have not been considered simultaneously in previous quantitative syntheses. Here, we performed a meta-analysis with 367 effect sizes from 70 studies of 35 invasive plant species from native and invasive populations. We tested how the residence time of invasive plant species and specialist reassociation in their introduced ranges affected evolutionary responses of defenses against specialists and generalists, including herbivore resistance traits (physical barriers, digestibility reducers and toxins), resistance effects (performance of and damage caused by specialists or generalists) and tolerance to damage (from specialists or generalists). We found that residence time and specialist reassociation each significantly altered digestibility reducers, specialist performance, generalist damage, and tolerance to specialist damage. Furthermore, residence time and specialist reassociation strongly altered toxins and generalist performance, respectively. When we restricted consideration to invasive plant species with both longer residence times and no reassociation with specialists, invasive populations had lower resistance to specialists, similar resistance to generalists, and higher tolerance to damage from both herbivore types, compared with native populations. We conclude that the duration and direction of selective pressure shape the evolutionary responses of invasive plants. Under long-term (long residence time) and stable (no specialist reassociation) selective pressure, invasive plants generally decrease resistance to specialists and increase tolerance to generalist damage that provides mixed support for the shifting defense hypothesis., (© 2024 The Ecological Society of America.)

Temporal fluctuation in nutrient availability generally promotes the growth of exotic plant species and has been recognized as an important driver of exotic plant invasions. However, little is known about how the impact of fluctuating nutrients on exotic species is dependent on the availability of other resources, although most ecosystems are experiencing dramatic variations in a wide variety of resources due to global change and human disturbance. Here, we explored how water availability mediates the effect of nutrient pulses on the growth of six exotic and six native plant species. We subjected individual plants of exotic and native species to well watered or water stressed conditions. For each level of water availability, we added equivalent amounts of nutrients at a constant rate, as a single large pulse, or in multiple small pulses. Under well watered conditions, nutrient pulses promoted exotic plant growth relative to nutrients supplied constantly, while they had no significant effect on natives. In contrast, under water stressed conditions, water deficiency inhibited the growth of all exotic and native species. More importantly, nutrient pulses did not increase plant growth relative to nutrients supplied constantly and these phenomena were observed for both exotic and native species. Taken together, our study shows that the impact of fluctuating nutrient availability on the growth of exotic plant species strongly depends on the variation of other resources, and that the positive effect of nutrient pulses under well watered conditions disappears under water stressed conditions. Our findings suggest that the variation in multiple resources may have complex feedback on exotic plant invasions and, therefore, it is critical to encompass multiple resources for the evaluation of fluctuating resource availability effects on exotic plant species. This will allow us to project the invasive trajectory of exotic plant species more accurately under future global change and human disturbance., (© 2022 The Authors. Ecological Applications published by Wiley Periodicals LLC on behalf of The Ecological Society of America.)

Fluctuating resource availability plays a critical role in determining non-native plant invasions through mediating the competitive balance between non-native and native species. However, the impact of fluctuating resource availability on interactions among non-native species remains largely unknown. This represents a barrier to understanding invasion mechanisms, particularly in habitats that harbor multiple non-native species with different responses to fluctuating resource availability. To examine the responses of non-native plant species to nutrient fluctuations, we compared the growth of each of 12 non-native species found to be common in local natural areas to nutrients supplied at a constant rate or supplied as a single large pulse in a pot experiment. We found that seven species produced more biomass with pulsed nutrients compared to constant nutrients (hereafter "benefitting species"), while the other five species did not differ between nutrient enrichment treatments (hereafter "non-benefitting species"). To investigate how nutrient fluctuations influence the interactions among non-native plant species, we established experimental non-native communities in the field with two benefitting and two non-benefitting non-native species. Compared with constant nutrient supply, the single large pulse of nutrient did not influence community biomass, but strongly increased the biomass and cover of the benefitting species and decreased those of the non-benefitting species. Furthermore, the benefitting species had higher leaf N content and greater plant height when nutrients were supplied as a single large pulse than at a constant rate, whereas the non-benefitting species showed no differences in leaf N content and were shorter when nutrients were supplied as a single large pulse than at a constant rate. Our results add to the growing evidence that the individual responses of non-native species to nutrient fluctuation are species-specific. More importantly, benefitting species were favored by nutrients coming in a pulse, while non-benefitting ones were favored by nutrients coming constantly when they grew together. This suggests that nutrient fluctuations can mediate the competitive balance among non-native plants and may thus determine their invasion success in a community harboring multiple non-native plant species., (© 2022 The Authors. Ecological Applications published by Wiley Periodicals LLC on behalf of The Ecological Society of America.)

Plant invasions profoundly impact both natural and managed ecosystems, and removal of the invasive plants addresses only part of the problem of restoring impacted areas. The rehabilitation of diverse communities and their ecosystem functions following removal of invasive plants is an important goal of ecological restoration. Arthropod assemblages and trophic interactions are important indicators of the success of restoration, but they have largely been overlooked in saltmarshes. We determined how arthropod assemblages and trophic interactions changed with the invasion of the exotic plant Spartina alterniflora and with the restoration of the native plant Phragmites australis following Spartina removal in a Chinese saltmarsh. We investigated multiple biotic and abiotic variables to gain insight into the factors underlying the changes in arthropod assemblages and trophic structure. We found that although Spartina invasion had changed arthropod diversity, community structure, feeding-guild composition, and the diets of arthropod natural enemies in the saltmarsh, these changes could be reversed by the restoration of native Phragmites vegetation following removal of the invader. The variation in arthropod assemblages and trophic structure were critically associated with four biotic and abiotic variables (aboveground biomass, plant density, leaf N, and soil salinity). Our findings demonstrate the positive effects of controlling invasive plants on biodiversity and nutrient cycling and provide a foundation for assessing the efficacy of ecological restoration projects in saltmarshes., (© 2022 The Ecological Society of America.)

Invasive plants from their native and introduced ranges differ in their interactions with herbivores but it is not known whether they also vary in their interactions with herbivore natural enemies. Here, we used olfactometer bioassays and cage experiments to investigate how foraging behaviors of 2 parasitoid and 1 hyperparasitoid species depended on plant population origin. Triadica sebifera (Euphorbiaceae) is native to China but invasive in the United States. In China, it is fed on by a specialist noctuid Gadirtha fusca (Lepidoptera: Nolidae), which hosts a parasitoid Apanteles sp. (Hymenoptera: Microgastinae) and hyperparasitoid (Hymenoptera: Eurytomidae) plus a generalist aphid Toxoptera odinae (Homoptera: Aphidiidae) parasitized by Lysiphlebus confusus (Hymenoptera: Aphidiinae). Both parasitoids preferred plants infested by their host over herbivore-free plants in olfactometer bioassays. Apanteles sp. and Eurytomid wasps preferred G. fusca infested plants from China populations over those from US populations in olfactometer bioassays but L. confusus wasps did not discriminate between T. odinae infested plants from China vs. US populations. Similarly, G. fusca caterpillars on China population plants were more likely to be parasitized than ones on US population plants when they were in the same cage but odds of parasitism for T. odinae did not differ for those on China vs. US population plants. These results suggest that populations from the native and introduced ranges may differ in traits that impact higher trophic levels. This may have implications for successful control of invasive plants as biocontrol agents are introduced or herbivores begin to feed on them in their introduced ranges., (© The Author(s) 2023. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Secondary invasions in which nontarget invaders expand following eradication of a target invader commonly occur in habitats with multiple invasive plant species and can prevent recovery of native communities. However, the dynamics and mechanisms of secondary invasion remain unclear. Here, we conducted a common garden experiment to test underlying mechanisms of secondary invasion for 14 nontarget invaders after biological control of Ambrosia artemisiifolia in two consecutive years. We found secondary invasion for all tested nontarget invaders, but secondary invasiveness (change relative to natives) varied with species and time. Specifically, secondary invasiveness depended most strongly on phylogenetic relatedness between the target and nontarget invaders in the first year with closely related nontarget invaders being most invasive. By contrast, secondary invasiveness in the second year was mostly driven by functional traits with taller nontarget invaders or those with higher specific leaf area, or smaller seeds especially invasive. Our study indicates that secondary invasion is likely to occur wherever other invasive plants co-occur with an invasive species targeted for control. Furthermore, the most problematic invaders will initially be species closely related to the target invader but then species with rapid growth and high reproduction are most likely to be more aggressive secondary invaders., (© 2023 The Authors New Phytologist © 2023 New Phytologist Foundation.)

Temperature has a large influence on insect abundances, thus under climate change, identifying major drivers affecting pest insect populations is critical to world food security and agricultural ecosystem health. Here, we conducted a meta-analysis with data obtained from 120 studies across China and Europe from 1970 to 2017 to reveal how climate and agricultural practices affect populations of wheat aphids. Here we showed that aphid loads on wheat had distinct patterns between these two regions, with a significant increase in China but a decrease in Europe over this time period. Although temperature increased over this period in both regions, we found no evidence showing climate warming affected aphid loads. Rather, differences in pesticide use, fertilization, land use, and natural enemies between China and Europe may be key factors accounting for differences in aphid pest populations. These long-term data suggest that agricultural practices impact wheat aphid loads more than climate warming., (© 2022. The Author(s).)

Plants are often exposed to multiple herbivores and densities of these attackers (or corresponding damage intensities) often fluctuate greatly in the field. Plant-mediated interactions vary among herbivore species and with changing feeding intensity, but little is known about how herbivore identity and density interact to determine plant responses and herbivore fitness. Here, we investigated this question using Triadica sebifera (tallow) and two common and abundant specialist insect herbivores, Bikasha collaris (flea beetle) and Heterapoderopsis bicallosicollis (weevil). By manipulating densities of leaf-feeding adults of these two herbivore species, we tested how variations in the intensity of leaf damage caused by flea beetle or weevil adults affected the performance of root-feeding flea beetle larvae and evaluated the potential of induced tallow root traits to predict flea beetle larval performance. We found that weevil adults consistently decreased the survival of flea beetle larvae with increasing leaf damage intensities. In contrast, conspecific flea beetle adults increased their larval survival at low damage then decreased larval survival at high damage, resulting in a unimodal pattern. Chemical analyses showed that increasing leaf damage from weevil adults linearly decreased root carbohydrates and increased root tannin, whereas flea beetle adults had opposite effects as weevil adults at low damage and similar effects as them at high damage. Furthermore, across all feeding treatments, flea beetle larval survival correlated positively with concentrations of carbohydrates and negatively with concentration of tannin, suggesting that root primary and secondary metabolism might underlie the observed effects on flea beetle larvae. Our study demonstrates that herbivore identity and density interact to determine systemic plant responses and plant-mediated effects on herbivores. In particular, effects are species-specific at low densities, but converge at high densities. These findings emphasize the importance of considering herbivore identity and density simultaneously when investigating factors driving plant-mediated interactions between herbivores, which advances our understanding of the structure and composition of herbivore communities and terrestrial food webs., (© 2022 The Authors. Ecology published by Wiley Periodicals LLC on behalf of The Ecological Society of America.)

Climate and plant invasion can shape biotic communities at large spatial scales. Yet, how diverse groups of organisms associated with an invasive plant change simultaneously with latitude and the roles of climate and plant invasion remains unclear. We conducted a field survey of plants (native vs exotic), soil fungi (pathogenic, saprotrophic, arbuscular mycorrhiza fungi (AMF) and ectomycorrhizal (EcM) fungi) and arthropods (herbivores, predators and detritivores) associated with the invasive plant Alternanthera philoxeroides at 49 sites spanning 14 latitudinal degrees in China. Results showed that diversity and composition of these functional groups changed differently with latitude, partially due to their specific responses to climate, invasion of A. philoxeroides and other biotic environments. Moreover, A. philoxeroides invasion and/or composition of other plants, rather than climate, predicted the diversity and richness of major functional groups and partly explained variance in composition of putative fungal pathogens. Our results suggest that climate and plant invasion could affect the diversity and composition of diverse groups of organisms simultaneously and their relative importance might vary among functional groups. Thus, it is necessary to explore latitudinal patterns and underlying drivers of diverse groups of organisms simultaneously to improve our ability to predict and mitigate threats posed by plant invasion and climate change., (© 2021 The Authors New Phytologist © 2021 New Phytologist Foundation.)

Many invasive plants have enhanced mutualistic arbuscular mycorrhizal (AM) fungal associations, however, mechanisms underlying differences in AM fungal associations between introduced and native populations of invasive plants have not been explored. Here we test the hypothesis that variation in root exudate chemicals in invasive populations affects AM fungal colonization and then impacts plant performance. We examined flavonoids (quercetin and quercitrin) in root exudates of native and introduced populations of the invasive plant Triadica sebifera and tested their effects on AM fungi and plant performance. We found that plants from introduced populations had higher concentrations of quercetin in root exudates, greater AM fungal colonization and higher biomass. Applying root exudates more strongly increased AM fungal colonization of target plants and AM fungal spore germination when exudate donors were from introduced populations. The role of root exudate chemicals was further confirmed by decreased AM fungal colonization when activated charcoal was added into soil. Moreover, addition of quercetin into soil increased AM fungal colonization, indicating quercetin might be a key chemical signal stimulating AM fungal associations. Together these results suggest genetic differences in root exudate flavonoids play an important role in enhancing AM fungal associations and invasive plants' performance, thus considering root exudate chemicals is critical to unveiling mechanisms governing shifting plant-soil microbe interactions during plant invasions.

Background: Tri-trophic interactions among plants, insect herbivores and entomopathogens are one of the hot topics in ecology. Although plants have been shown to impact the interactions between herbivores and entomopathogens, it is still unclear how plants affect the cellular immunity of herbivores to entomopathogens., Results: The number of hemocytes and the proportion of two main cell types (granular hemocytes and plasmatocytes), plasmatocyte-spreading rate, apoptosis rate, two Spodoptera exigua caspase (SeCasp-1, SeCasp-5) activities and gene expressions were all higher and the activities and gene expression of S. exigua inhibitor of apoptosis protein (SeIAP) were lower in nucleopolyhedrovirus (NPV)-infected caterpillars fed Ipomoea aquatica than those fed other plants or artificial diet. Scanning electron microscopy images were consistent with molecular patterns of immune responses., Conclusion: This study suggests that host plants affect the immune responses of herbivores to entomopathogens by manipulating the composition, morphology and apoptosis of herbivore hemocytes, which sheds light on the mechanisms that allow host plants to influence multi-trophic interactions. © 2021 Society of Chemical Industry., (© 2021 Society of Chemical Industry.)

Background and Aims: Plant invasions can change soil microbial communities and affect subsequent invasions directly or indirectly via foliar herbivory. It has been proposed that invaders promote uniform biotic communities that displace diverse, spatially variable communities (the biotic homogenization hypothesis), but this has not been experimentally tested for soil microbial communities, so the underlying mechanisms and dynamics are unclear. Here, we compared density-dependent impacts of the invasive plant Alternanthera philoxeroides and its native congener A. sessilis on soil fungal communities, and their feedback effects on plants and a foliar beetle., Methods: We conducted a plant-soil feedback (PSF) experiment and a laboratory bioassay to examine PSFs associated with the native and invasive plants and a beetle feeding on them. We also characterized the soil fungal community using high-throughput sequencing., Key Results: We found locally differentiated soil fungal pathogen assemblages associated with high densities of the native plant A. sessilis but little variation in those associated with the invasive congener A. philoxeroides, regardless of plant density. In contrast, arbuscular mycorrhizal fungal assemblages associated with high densities of the invasive plant were more variable. Soil biota decreased plant shoot mass but their effect was weak for the invasive plant growing in native plant-conditioned soils. PSFs increased the larval biomass of a beetle reared on leaves of the native plant only. Moreover, PSFs on plant shoot and root mass and beetle mass were predicted by different pathogen taxa in a plant species-specific manner., Conclusion: Our results suggest that plant invasions can rapidly increase the similarity of soil pathogen assemblages even at low plant densities, leading to taxonomically and functionally homogeneous soil communities that may limit negative soil effects on invasive plants., (© The Author(s) 2020. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Atmospheric greenhouse gas (GHG) concentration increases are a serious problem impacting global climate. Mitigation of agricultural GHG production is crucial as fertilized soils contribute substantially to changes in GHG atmospheric composition. Biochar derived from agricultural or forestry biowaste has been widely used in agriculture and may help mitigate GHG emissions. While different kinds of biochar and their effects on GHG emissions have been studied, feedstock particle size may interact with pyrolysis temperature to impact biochar effects on GHG emissions, but this has not been investigated. Here, feedstock particle size effects on biochar characteristics and soil nitrous oxide (N 2 O) and carbon dioxide (CO 2 ) emissions were studied using Camellia oleifera fruit shell feedstock with three particle size fractions (0.5-2, 2-5, and 5-10 mm) each pyrolyzed at 300, 450, and 600 °C. Results showed that dissolved organic carbon in biochar increased with particle size when pyrolyzed at 300 °C, but decreased with pyrolysis temperature. The 0.5-2 mm shell-derived biochar was associated with the lowest N 2 O and CO 2 emission rates but the highest net nitrogen mineralization rates compared to 2-5 mm and 5-10 mm shell-derived biochar when pyrolyzed at 300 °C. Overall, shell particle size was more important for soil processes at lower pyrolysis temperatures with less variation among particle sizes at higher pyrolysis temperatures. The results indicated that feedstock particle size may interact with pyrolysis temperature and impact mitigation of soil N 2 O and CO 2 emissions., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Invasive plant environments differ along latitudes and between native and introduced ranges. In response to herbivory and abiotic stresses that vary with latitudes and between ranges, invasive plants may shift their secondary chemicals to facilitate invasion success. However, it remains unclear whether and how invasive plant chemical responses to herbivory and chemical responses to abiotic environments are associated. We conducted large scale field surveys of herbivory on the invasive tallow tree (Triadica sebifera) along latitudes in both its native (China) and introduced ranges (United States) and collected leaf samples for analyses of tannins and flavonoids. We used data on climate and solar radiation to examine these chemical responses to abiotic environments and their variations along these latitudes and between ranges. We also re-analyzed previously published data from multiple common garden experiments on tallow tree to investigate genetic divergence of secondary chemical concentrations between introduced and native populations. We found foliar tannins and herbivory (chewing, sucking) were higher in the native range compared to the invasive range. Allocation to tannins versus flavonoids decreased with latitude in the native range but did not vary in the invasive range. Analyses of previously published common garden experimental data indicated genetic divergence contributes to chemical concentration differences between ranges. Our field data further indicated that the latitudinal patterns were primarily phenotypic responses to herbivory in China while in US they were primarily phenotypic responses to abiotic environments. The variation of tannins may be linked to flavonoids, given tannins and flavonoids share a biosynthesis pathway. Together, our results suggest that invasive plants adjust their secondary metabolism to decrease chemicals that primarily defend against herbivory and increase those that help them to respond to their abiotic environment. These findings deepen our understanding of how invasive plants adapt to biogeographically heterogeneous environments through trade-offs between secondary chemical responses., Competing Interests: Declaration of competing interest All authors declare that they have no competing interests., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Native and introduced plant populations vary in leaf physiology, biochemistry, and biotic interactions. These aboveground traits may help invasive plants in competition for resources with co-occurring native species. Root physiological traits may affect invasive plant performance because of the roles of roots in resource absorption. The aim of this study was to test this prediction, using invasive Chinese tallow tree ( Triadica sebifera ), as a model species. Here we examined carbohydrate (soluble sugar, sucrose, fructose, starch, and cellulose) concentrations and the mass of roots, stems, and leaves, along with root water potential and arbuscular mycorrhizal fungi (AMF) colonization of soil-cultured T. sebifera seedlings from 10 native (China) and 10 introduced (United States) populations in a common garden. Introduced populations had a significantly greater stem and leaf mass than native populations but their root masses did not differ, so they had lower R:S. Introduced populations had higher soluble sugar concentrations but lower starch and cellulose concentrations in their leaves, stems, and roots. Introduced populations had more negative root water potentials and higher AMF colonization. Together, our results indicate that invasive plants shift their carbohydrate allocation, leading to faster growth and a greater aboveground allocation strategy. Higher AMF colonization and more negative water potential in invasive plants likely facilitate more efficient water absorption by the roots. Thus, such physiological variation in root characteristics could play a role in plant invasion success., (Copyright © 2020 Li, Wang, Tian, Ding and Siemann.)

Edible mushroom cultivation is an important industry in intensively managed forest understories. However, proper disposal of spent mushroom substrate (SMS) presents a challenge to its sustainable development. Biochar derived from SMS could be used to improve soil quality while providing a solution for SMS disposal. But SMS biochar pyrolyzed at different temperatures may alter carbon dioxide (CO 2 ) and nitrous oxide (N 2 O) emissions associated with global warming, especially under the context of nitrogen (N) addition and warming. We conducted a factorial incubation study to examine greenhouse gas emissions and N transformations in moso bamboo forest soil amended with SMS-biochar (control vs. pyrolyzed at 300, 450 or 600 °C) in different N-addition (0 or 100 mg N kg -1 soil) and temperature (20, 25 or 30 °C) treatments. Pyrolysis temperature affected pH, C and N of SMS-biochars. N-transformations depended on the interaction of pyrolysis temperature, N-addition, and incubation temperature but were generally lower with 450 °C biochar addition. Soil N 2 O emissions increased with N-addition and they were more sensitive to incubation temperatures without biochar. Soil CO 2 emissions increased with incubation temperature or biochar pyrolyzed at lower temperatures. Pyrolysis temperature might have regulated the effects of SMS-derived biochar on N 2 O emissions via changes in dissolved C, N, pH and associated changes in soil microbial community compositions. Because of the importance of sustainable development of this understory industry, amending soils with biochar produced at higher temperatures may be the best strategy for both the disposal of SMS and the mitigation of greenhouse gas emissions., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Climate change is predicted to increase the frequency and impact of plant invasions, creating a need for new control strategies as part of mitigation planning. The complex interactions between invasive plants and biocontrol agents have created distinct policy and management challenges, including the effectiveness and risk assessment of biocontrol under different climate change scenarios. In this brief review, we synthesize recent studies describing the potential ecological and evolutionary outcomes for biocontrol agents/candidates for plant invaders under climate change. We also discuss potential methodologies that can be used as a framework for predicting ecological and evolutionary responses of plant-natural enemy interactions under climate change, and for refining our understanding of the efficacy and risk of using biocontrol on invasive plants., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: Interactions between herbivorous insects and entomoviruses may depend on host plant, perhaps mediated through changes in herbivore innate immunity., Results: Caterpillars (Spodoptera exigua) fed Glycine max had high viral loads and low melanization rates together with low melanization enzyme [PO, DDC, TH] activities and gene expressions. Caterpillars fed Ipomoea aquatica had low viral loads and high melanization, gene activities and gene expressions while those fed Brassica oleracea or artificial diet had intermediate levels of each. Melanization rates were negatively correlated with viral loads and positively correlated with activity and expression of each of the three enzymes. Some diet effects on enzymes were constitutive because the same diets led to low (G. max) or high (I. aquatica) melanization related gene activities and expressions without infection., Conclusion: Diet influences the interactions between insect herbivores and viruses by shaping the innate immune response both at the onset of infection and afterwards as viral loads accumulate over a period of days. In addition, diets that lead to low viral loads are associated with high activities and gene expressions of a variety of melanization related enzymes suggesting a common causative mechanism. © 2019 Society of Chemical Industry., (© 2019 Society of Chemical Industry.)

Warming and eutrophication can have varying effects on exotic species performance and their interactions. These effects can vary with trophic level, but are rarely investigated simultaneously on exotic species from multiple trophic levels. To address this, we manipulated temperature, nutrients, and plant origin (native vs. exotic) in snail invaded wetland communities. Warming increased exotic apple snail (Pomacea maculata) reproduction (4-fold increase in egg mass) and also number of egg clutches produced while warming slowed exotic snail growth, suggesting a trade-off between reproduction and growth in exotic snails influenced by warming and nutrients. However, exotic snail size varied with warming and nutrients. Additionally, warming reduced native plant mass with no effect on exotic plants while nutrients had greater positive effects on exotic plants biomass. In combination warming and nutrient enrichment will likely increase exotic snail growth, while nutrient enrichment alone will contribute to exotic plant dominance. In conclusion, the individual and interactive effects of warming and eutrophication vary with the trophic level of exotic species with trade-offs in exotic herbivores depending on environmental conditions, making it difficult to predict effects of multiple anthropogenic factors on co-occurring exotic plants and their effects on native communities., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Arbuscular mycorrhizal fungi (AMF) are important mutualistic microbes in soil, which have capacity to form mutualistic associations with most land plants. Arbuscular mycorrhizal fungi play an important role in plant invasions and their interactions with invasive plants have received increasing attention. However, the chemical mechanisms underlying the interactions of AMF and invasive plants are still poorly understood. In this study we aim to test whether root secondary chemicals are related to enhanced AMF colonization and rapid growth in an invasive tree. We conducted a common garden experiment in China with Chinese tallow tree ( Triadica sebifera ) to examine the relationships among AMF colonization and secondary metabolites in roots of plants from introduced (USA) and native (China) populations. We found that AMF colonization rate was higher in introduced populations compared to native populations. Roots of plants from introduced populations had lower levels of phenolics and tannins, but higher levels of flavonoids than those of plants from native populations. Flavonoids were positively correlated with AMF colonization, and this relationship was especially strong for introduced populations. Besides, AMF colonization was positively correlated with plant biomass suggesting that higher root flavonoids and AMF colonization may impact plant performance. This suggests that higher root flavonoids in plants from introduced populations may promote AMF spore germination and/or attract hyphae to their roots, which may subsequently increase plant growth. Overall, our results support a scenario in which invasive plants enhance their AMF association and invasion success via genetic changes in their root flavonoid metabolism. These findings advance our understanding of the mechanisms underlying plant invasion success and the evolutionary interactions between plants and AMF. Understanding such mechanisms of invasive plant success is critical for predicting and managing plant invasions in addition to providing important insights into the chemical mechanism of AMF-plant interactions., (© The Author(s) 2020. Published by Oxford University Press on behalf of the Annals of Botany Company.)

Endosymbiosis is found in all types of ecosystems and it can be sensitive to environmental changes due to the intimate interaction between the endosymbiont and the host. Indeed, global climate change disturbs the local ambient environment and threatens endosymbiotic species, and in some cases leads to local ecosystem collapse. Recent studies have revealed that the endosymbiont can affect holobiont (endosymbiont and host together) stress tolerance as much as the host does, and manipulation of the microbial partners in holobionts may mitigate the impacts of the environmental stress. Here, we first show how the endosymbiont presence affects holobiont stress tolerance by discussing three well-studied endosymbiotic systems, which include plant-fungi, aquatic organism-algae, and insect-bacteria systems. We then review how holobionts are able to alter their stress tolerance via associated endosymbionts by changing their endosymbiont composition, by adaptation of their endosymbionts, or by acclimation of their endosymbionts. Finally, we discuss how different transmission modes (vertical or horizontal transmission) might affect the adaptability of holobionts. We propose that the endosymbiont is a good target for modifying holobiont stress tolerance, which makes it critical to more fully investigate the role of endosymbionts in the adaptive responses of holobionts to stress.

Background and Aims: The strengths of biotic interactions such as herbivory are expected to decrease with increasing latitude for native species. To what extent this applies to invasive species and what the consequences of this variation are for competition among native and invasive species remain unexplored. Here, herbivore impacts on the invasive plant Alternanthera philoxeroides and its competition with the native congener A. sessilis were estimated across latitudes in China., Methods: An common garden experiment spanning ten latitudinal degrees was conducted to test how herbivore impacts on A. philoxeroides and A. sessilis, and competition between them change with latitude. In addition, a field survey was conducted from 21°N to 36.8°N to test whether A. philoxeroides invasiveness changes with latitude in nature as a result of variations in herbivory., Key Results: In the experiment, A. sessilis cover was significantly higher than A. philoxeroides cover when they competed in the absence of herbivores, but otherwise their cover was comparable at low latitude. However, A. philoxeroides cover was always higher on average than A. sessilis cover at middle latitude. At high latitude, only A. sessilis emerged in the second year. Herbivore abundance decreased with latitude and A. philoxeroides emerged earlier than A. sessilis at middle latitude. In the field survey, the ratio of A. philoxeroides to A. sessilis cover was hump shaped with latitude., Conclusion: These results indicate that herbivory may promote A. philoxeroides invasion only at low latitude by altering the outcome of competition in favour of the invader and point to the importance of other factors, such as earlier emergence, in A. philoxeroides invasion at higher latitudes. These results suggest that the key factors promoting plant invasions might change with latitude, highlighting the importance of teasing apart the roles of multiple factors in plant invasions within a biogeographic framework., (© The Author(s) 2019. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)