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1.
Environmental change is anticipated to negatively affect both plant and animal populations. As abiotic factors rapidly change habitat suitability, projections range from altered genetic diversity to wide-spread species loss. Here, we assess the degree to which changes in atmospheric composition associated with environmental change will influence not only the abundance, but also the genotypic/phenotypic diversity, of herbivore populations. Using free-air CO2 and O3 enrichment (FACE) technology, we assess numerical responses of pea aphids (Acyrthosiphon pisum) exhibiting a pink–green genetic polymorphism and an environmentally determined wing polyphenism on broad bean plants (Vicia faba) under enriched CO2 and/or O3 atmospheres, over multiple generations. We show that these two greenhouse gases alter not only aphid population sizes, but also genotypic and phenotypic frequencies. As the green genotype was positively influenced by elevated CO2 levels, but the pink genotype was not, genotypic frequencies (pink morph : green morph) ranged from 1 : 1 to 9 : 1. These two genotypes also displayed marked differences in phenotypic frequencies. The pink genotype exhibited higher levels of wing induction under all atmospheric treatments, however, this polyphenism was negatively influenced by elevated O3 levels. Resultantly, frequencies of winged phenotypes (pink morph : green morph) varied from 10 : 1 to 332 : 1. Thus, atmospheric conditions associated with environmental change may alter not just overall population sizes, but also genotypic and phenotypic frequencies of herbivore populations, thereby influencing community and ecosystem functioning.  相似文献   

2.
  • 1 Trembling aspen Populus tremuloides Michaux is an important forest species in the Great Lakes region and displays tremendous genetic variation in foliar chemistry. Elevated carbon dioxide (CO2) and ozone (O3) may also influence phytochemistry and thereby alter the performance of insect herbivores such as the aspen leaf beetle Chrysomela crotchi Brown.
  • 2 The present study aimed to relate genetic‐ and atmospheric‐based variation in aspen phytochemistry to C. crotchi performance (larval development time, adult mass, survivorship). The experiment was conducted at the Aspen Free‐Air CO2 Enrichment (FACE) site in northern Wisconsin. Beetles were reared on three aspen genotypes under elevated CO2 and/or O3. Leaves were collected to determine chemical characteristics.
  • 3 The foliage exhibited significant variation in nitrogen, condensed tannins and phenolic glycosides among genotypes. CO2 and O3, however, had little effect on phytochemistry. Nonetheless, elevated CO2 decreased beetle performance on one aspen genotype and had inconsistent effects on beetles reared on two other genotypes. Elevated O3 decreased beetle performance, especially for beetles reared on an O3‐sensitive genotype. Regression analyses indicated that phenolic glycosides and nitrogen explain a substantial amount (27–45%) of the variation in herbivore performance.
  • 4 By contrast to the negative effects that are typically observed with generalist herbivores, aspen leaf beetles appear to benefit from phenolic glycosides, chemical components that are largely genetically‐determined in aspen. The results obtained in the present study indicate that host genetic variation and atmospheric concentrations of greenhouse gases will be important factors in the performance of specialist herbivores, such as C. crotchi, in future climates.
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3.
Changes in atmospheric composition affect plant quality and herbivore performance. We used the Aspen Free Air CO2 Enrichment (FACE) facility to investigate the impacts of elevated carbon dioxide (CO2) and ozone (O3) on the performance of the aphid Cepegillettea betulaefoliae Granovsky feeding on paper birch (Betula papyrifera Marsh.). In Year 1, we simultaneously measured individual performance and population growth rates, and in Year 2 we surveyed natural aphid, predator and parasitoid populations throughout the growing season. Aphid growth and development (relative growth rate (RGR), development time, adult weight, embryo number and the birth weight of newborn nymphs) were unaffected by CO2 and O3. Aphid fecundity decreased on trees grown at elevated CO2, O3 and CO2+O3. Neither nymphal performance nor adult size were reliable indicators of future fecundity at elevated CO2 and/or O3. Aphid populations protected from natural enemies were unaffected by elevated CO2, but increased significantly at elevated O3. Individual fecundity in elevated CO2 and O3 atmospheres did not predict population growth rates, probably because of changes in the strength of intraspecific competition or the ability of the aphids to induce nutrient sinks. Natural aphid, predator and parasitoids populations (Year 2) showed few significant responses to CO2 and O3, although CO2 and O3 did affect the timing of aphid and natural enemy peak abundance. Elevated CO2 and O3 affected aphid and natural enemy populations independently: no CO2× O3 interactions were observed. We conclude that: (1) aphid individual performance did not predict population responses to CO2 and O3 and (2) elevated CO2 and O3 atmospheres are unlikely to affect C. betulaefoliae populations in the presence of natural enemy communities.  相似文献   

4.
5.
Rising atmospheric CO2 levels can dilute the nitrogen (N) resource in plant tissue, which is disadvantageous to many herbivorous insects. Aphids appear to be an exception that warrants further study. The effects of elevated CO2 (750 ppm vs. 390 ppm) were evaluated on N assimilation and transamination by two Medicago truncatula genotypes, a N‐fixing‐deficient mutant (dnf1) and its wild‐type control (Jemalong), with and without pea aphid (Acyrthosiphon pisum) infestation. Elevated CO2 increased population abundance and feeding efficiency of aphids fed on Jemalong, but reduced those on dnf1. Without aphid infestation, elevated CO2 increased photosynthetic rate, chlorophyll content, nodule number, biomass, and pod number for Jemalong, but only increased pod number and chlorophyll content for dnf1. Furthermore, aphid infested Jemalong plants had enhanced activities of N assimilation‐related enzymes (glutamine synthetase, Glutamate synthase) and transamination‐related enzymes (glutamate oxalate transaminase, glutamine phenylpyruvate transaminase), which presumably increased amino acid concentration in leaves and phloem sap under elevated CO2. In contrast, aphid infested dnf1 plants had decreased activities of N assimilation‐related enzymes and transmination‐related enzymes and amino acid concentrations under elevated CO2. Furthermore, elevated CO2 up‐regulated expression of genes relevant to amino acid metabolism in bacteriocytes of aphids associated with Jemalong, but down‐regulated those associated with dnf1. Our results suggest that pea aphids actively elicit host responses that promote amino acid metabolism in both the host plant and in its bacteriocytes to favor the population growth of the aphid under elevated CO2.  相似文献   

6.
Elevated concentrations of atmospheric CO2 can alter plant secondary metabolites,which play important roles in the interactions among plants,herbivorous insects and natural enemies.However,few studies have examined the cascading effects of host plant secondary metabolites on tri-trophic interactions under elevated CO2(eCO2).In this study,we determined the effects of eCO2 on the growth and foliar phenolics of Medicago truncatula and the cascading effects on two color genotypes oiAcyrthosiphon pisum(pink vs.green)and their parasitoid Aphidius avenae in the field open-top chambers.Our results showed that eCO2 increased photosynthetic rate,nodule number,yield and the total phenolic content of M.truncatula.eCO2 had contrasting effects on two genotypes of A.pisum;the green genotype demonstrated increased population abundance,fecundity,growth and feeding efficiency,while the pink genotype showed decreased fitness and these were closely associated with the foliar genstein content.Furthermore,eCO2 decreased the parasitic rate of A.avenae independent of aphid genotypes.eCO2 prolonged the emergence time and reduced the emergence rate and percentage of females when associated with the green genotype,but little difference,except for increased percentage of females,was observed in A.avenae under eCO2 when associated with the pink genotype,indicating that parasitoids can perceive and discriminate the qualities of aphid hosts.We concluded that eCO2 altered plant phenolics and thus the performance of aphids and parasitoids.Our results indicate that plant phenolics vary by different abiotic and biotic stimuli and could potentially deliver the cascading effects of eCO2 to the higher trophic levels.Our results also suggest that the green genotype is expected to perform better in future eCO2 because of decreased plant resistance after its infestation and decreased parasitic rate.  相似文献   

7.
  • 1 Natural forest systems constitute a major portion of the world's land area, and are subject to the potentially negative effects of both global climate change and invasion by exotic insects. A suite of invasive weevils has become established in the northern hardwood forests of North America. How these insects will respond to increasing CO2 or O3 is unknown.
  • 2 The present study examined the effects of elevated atmospheric CO2 and O3 on the invasive weevil Polydrusus sericeus Schaller at the Aspen Free Air CO2 Enrichment (FACE) site near Rhinelander, Wisconsin. A performance assay was conducted in the laboratory during the summer of 2007 using mated pairs of P. sericeus fed a combination of aspen, birch and maple foliage. We recorded leaf area consumption, oviposition and adult longevity. We also conducted visual abundance surveys in the field from 2004 to 2007 on aspen and birch at Aspen FACE.
  • 3 Elevated CO2, but not O3, significantly affected P. sericeus performance. Female, but not male, longevity was reduced under elevated CO2. Polydrusus sericeus also produced fewer eggs under elevated CO2 conditions compared with ambient conditions. Adult P. sericeus strongly preferred birch over both aspen and maple, regardless of fumigation treatment.
  • 4 The effects of elevated CO2 on P. sericeus populations at Aspen FACE were minimal, and varied among years and host tree species. Polydrusus sericeus abundance was significantly greater on birch than aspen. Over the long term, elevated CO2 may reduce adult female longevity and fecundity of P. sericeus. Further studies are needed to evaluate how this information may scale to ecosystem impacts.
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8.
Host evaluation behaviour was examined in three species of aphid parasitoids,Aphidius ervi haliday,A. pisivorus Smith, andA. smithi Sharma & Subba Rao (Hymenoptera: Aphidiidae). Parasitoids were provided under laboratory conditions with three kinds of hosts representing two aphid species: (green) pea aphid,Acyrthosiphon pisum (Harris), and green and pink colour morphs of the alfalfa aphid,Macrosiphum creelii Davis. Females of all threeAphidius species distinguished between aphids on the basis of colour, movement, and host species. Patterns of host acceptance by parasitoids were species-specific. InA. ervi, host preference was the same in light and dark conditions: pea aphid>green alfalfa aphid≫pink alfalfa aphid. In contrast,A. pisivorus attacked and accepted pea aphid and green alfalfa aphid equally in the light and preferred both of these over pink alfalfa aphid; however, it made no distinction between pea aphid and pink alfalfa aphid in the dark. Females ofA. smithi attacked all three kinds of hosts (pea aphid>green alfalfa aphid≫pink alfalfa aphid) but apparently laid eggs only in pea aphid. The frequencies of attack and oviposition by all wasps were higher on ‘normal’ pea aphids than on those anaesthetized with CO2. Host recognition is confirmed by chemical cues in the aphid cuticle that are detected during antennation, and host acceptance is dependent on an assessment of host quality during ovipositor probing.  相似文献   

9.
This study examined the effects of carbon dioxide (CO2)-, ozone (O3)-, and genotype-mediated changes in quaking aspen (Populus tremuloides) chemistry on performance of the forest tent caterpillar (Malacosoma disstria) and its dipteran parasitoid (Compsilura concinnata) at the Aspen Free-Air CO2 Enrichment (FACE) site. Parasitized and non-parasitized forest tent caterpillars were reared on two aspen genotypes under elevated levels of CO2 and O3, alone and in combination. Foliage was collected for determination of the chemical composition of leaves fed upon by forest tent caterpillars during the period of endoparasitoid larval development. Elevated CO2 decreased nitrogen levels but had no effect on concentrations of carbon-based compounds. In contrast, elevated O3 decreased nitrogen and phenolic glycoside levels, but increased concentrations of starch and condensed tannins. Foliar chemistry also differed between aspen genotypes. CO2, O3, genotype, and their interactions altered forest tent caterpillar performance, and differentially so between sexes. In general, enriched CO2 had little effect on forest tent caterpillar performance under ambient O3, but reduced performance (for insects on one aspen genotype) under elevated O3. Conversely, elevated O3 improved forest tent caterpillar performance under ambient, but not elevated, CO2. Parasitoid larval survivorship decreased under elevated O3, depending upon levels of CO2 and aspen genotype. Additionally, larval performance and masses of mature female parasitoids differed between aspen genotypes. These results suggest that host-parasitoid interactions in forest systems may be altered by atmospheric conditions anticipated for the future, and that the degree of change may be influenced by plant genotype.  相似文献   

10.
11.
The effects of three different CO2 concentrations (400, 600, and 1000 ppm) on the population parameters and growth of the green peach aphid, Myzus persicae, were examined. Raw life history data from M. persicae were analyzed using an age-stage, two-sex life table to take into account the viable development rate among individuals. The population projections of M. persicae indicate the stage structure and variability of the population growth under different CO2 concentrations based on an age-stage, two-sex life table analysis. Significantly longer oviposition duration and higher fecundity were observed under elevated CO2 (600 and 1000 ppm) than those under ambient CO2 (400 ppm). Furthermore, the M. persicae population reared under elevated CO2 concentrations showed higher intrinsic and finite rates of population increase than under ambient CO2 concentrations. These results indicate that the population parameters and growth of M. persicae were positively influenced in the fecundity by elevated CO2 concentrations relative to the ambient CO2. These findings indicate that it is basically remained to understand the direct effects of CO2 elevation on the host plants, and the interaction between the host plants and M. persicae in the same CO2 concentration for establishing more realistic population growth model systems for M. persicae in the aerial environment rising CO2 concentration level.  相似文献   

12.
Abstract
  • 1 Genetic variation in the phytochemical responses of plants to CO2 enrichment is likely to alter trophic dynamics, and to shift intraspecific selection pressures on plant populations. We evaluated the independent and interactive effects of atmospheric CO2 and quaking aspen (Populus tremuloides Michx.) genotype on chemical composition of foliage and performance of the whitemarked tussock moth (Orgyia leucostigma J. E. Sm.).
  • 2 This research was conducted at the Aspen FACE (Free Air CO2 Enrichment) site in northern Wisconsin, U.S.A. Leaf samples were collected periodically from each of three genetically variable aspen genotypes growing under ambient and elevated CO2, and analysed for levels of primary and secondary metabolites. Tussock moth larvae were reared in situ on experimental trees, and development times and pupal masses were recorded.
  • 3 Foliar chemical composition varied among aspen genotypes and in response to CO2 enrichment. However, chemical responses of trees to elevated CO2 were generally consistent across genotypes.
  • 4 Larval development times varied among host genotypes and increased slightly for insects on high‐CO2 plants. Enriched CO2 tended to reduce insect pupal masses, particularly for females on one of the three aspen genotypes.
  • 5 CO2 × genotype interactions observed for plant chemistry and insect performance in this study with a small number of genotypes are probably too few, and too weak, to shift selection pressures in aspen populations. These results differ, however, from earlier work in which more substantial CO2 × genotype interactions were observed for plant chemistry.
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13.
Atmospheric change and species invasions are arguably two of the most important factors affecting the long‐term sustainability of natural ecosystems. We examined the independent and interactive effects of atmospheric carbon dioxide (CO2) and tropospheric ozone (O3) on the foliar quality of two host species and performance of an invasive folivorous insect. Trembling aspen (Populus tremuloides) and paper birch (Betula papyrifera) were grown at the Aspen FACE research site in northern Wisconsin, USA, under all combinations of ambient and elevated CO2 and O3. We measured the effects of elevated CO2 and O3 on aspen and birch phytochemistry and on the survivorship, development time, growth, and fecundity of the gypsy moth (Lymantria dispar). Elevated CO2 had little effect on, whereas elevated O3 altered, the composite phytochemical profiles of aspen and birch. Nutritional quality in aspen and birch leaves was marginally affected by elevated CO2 and reduced by elevated O3. Both gases increased concentrations of phenolic and structural compounds in aspen and birch. Elevated CO2 offset reduced foliar quality under elevated O3, but only in aspen, and to a greater extent later than earlier in spring. Elevated CO2 generally had beneficial effects on, while elevated O3 detrimentally affected, gypsy moth performance. Elevated CO2 ameliorated most of the reductions in gypsy moth performance under elevated O3. Our findings suggest that atmospheric change can alter foliar quality in gypsy moth hosts sufficiently to influence gypsy moth performance, but that these responses will depend on interactions among CO2, O3, and tree species. Our findings also contrast with those of earlier studies at Aspen FACE, indicating that foliar quality responses to environmental change are likely influenced by tree stand age and longevity of exposure to pollutants to the extent that they affect plant‐herbivore interactions differently over decadal time spans.  相似文献   

14.
The performance of predators of plant pests is mainly driven by their ability to find prey. Recent studies suggest that rising atmospheric carbon dioxide (CO2) concentrations will affect the semiochemistry of plant–insect relationships, possibly altering prey‐finding behaviour. In the present study, we test the hypothesis that higher atmospheric CO2 concentrations affect the oviposition behaviour of an aphidophagous hoverfly and alter the development of its larvae. We also test the hypothesis that volatile compounds released by the plant–aphid association are modified under elevated CO2. Broad bean plants infested with pea aphids are grown under ambient (450 ppm) or elevated CO2 (800 ppm) concentrations. Plants raised under each treatment are then presented to gravid hoverfly females in a dual‐choice bioassay. In addition, emerging Episyrphus balteatus larvae are directly fed with aphids reared under ambient or elevated CO2 conditions and then measured and weighed daily until pupation. Odours emitted by the plant–aphid association are sampled. A larger number of eggs is laid on plants grown under ambient CO2 conditions. However, no significant difference is observed between the two groups of predatory larvae grown under different CO2 concentrations, indicating that the CO2 concentration does not affect the quality of their aphid diet. Although plant volatiles do not differ between the ambient and elevated CO2‐treated plants, we find that the quantity of aphid alarm pheromone is lower on the plant–aphid association raised under the elevated CO2 condition. This suggests that an alteration of semiochemical emissions by elevated CO2 concentrations impacts the oviposition behaviour of aphid predators.  相似文献   

15.
Abstract Effects of CO2 level (ambient vs. elevated) on the interactions among three cotton (Gossypium hirsutum) genotypes, the cotton aphid (Aphis gossypii Glover), and its hymenoptera parasitoid (Lysiphlebia japonica Ashrnead) were quantified. It was hypothesized that aphid‐parasitoid interactions in crop systems may be altered by elevated CO2, and that the degree of change is influenced by plant genotype. The cotton genotypes had high (M9101), medium (HZ401) and low (ZMS13) gossypol contents, and the response to elevated CO2 was genotype‐specific. Elevated CO2 increased the ratio of total non‐structural carbohydrates to nitrogen (TNC: N) in the high‐gossypol genotype and the medium‐gossypol genotype. For all three genotypes, elevated CO2 had no effect on concentrations of gossypol and condensed tannins. A. gossypii fitness declined when aphids were reared on the high‐gossypol genotype versus the low‐gossypol genotype under elevated CO2. Furthermore, elevated CO2 decreased the developmental time of L. japonica associated with the high‐gossypol genotype and the low‐gossypol genotype, but did not affect parasitism or emergence rates. Our study suggests that the abundance of A. gossypii on cotton will not be directly affected by increases in atmospheric CO2. We speculate that A. gossypii may diminish in pest status in elevated CO2 and high‐gossypol genotype environments because of reduced fitness to the high‐gossypol genotype and shorter developmental time of L. japonica.  相似文献   

16.
The aim of this study was to examine the effects of elevated carbon dioxide [CO2] and ozone [O3] and their interaction on wood chemistry and anatomy of five clones of 3‐year‐old trembling aspen (Populus tremuloides Michx.). Wood chemistry was studied also on paper birch (Betula papyrifera Marsh.) and sugar maple (Acer saccharum Marsh.) seedling‐origin saplings of the same age. Material for the study was collected from the Aspen Free‐Air CO2 Enrichment (FACE) experiment in Rhinelander, WI, USA, where the saplings had been exposed to four treatments: control (C; ambient CO2, ambient O3), elevated CO2 (560 ppm during daylight hours), elevated O3 (1.5 × ambient during daylight hours) and their combination (CO2+O3) for three growing seasons (1998–2000). Wood chemistry responses to the elevated CO2 and O3 treatments differed between species. Aspen was most responsive, while maple was the least responsive of the three tree species. Aspen genotype affected the responses of wood chemistry and, to some extent, wood structure to the treatments. The lignin concentration increased under elevated O3 in four clones of aspen and in birch. However, elevated CO2 ameliorated the effect. In two aspen clones, nitrogen in wood samples decreased under combined exposure to CO2 and O3. Soluble sugar concentration in one aspen clone and starch concentration in two clones were increased by elevated CO2. In aspen wood, α‐cellulose concentration changed under elevated CO2, decreasing under ambient O3 and slightly increasing under elevated O3. Hemicellulose concentration in birch was decreased by elevated CO2 and increased by elevated O3. In aspen, elevated O3 induced statistically significant reductions in distance from the pith to the bark and vessel lumen diameter, as well as increased wall thickness and wall percentage, and in one clone, decreased fibre lumen diameter. Our results show that juvenile wood properties of broadleaves, depending on species and genotype, were altered by atmospheric gas concentrations predicted for the year 2050 and that CO2 ameliorates some adverse effects of elevated O3 on wood chemistry.  相似文献   

17.
1 This research was conducted at the Aspen FACE (Free Air CO2 Enrichment) site located in northern Wisconsin, U.S.A. where trembling aspen (Populus tremuloides Michaux) trees were exposed to one of four atmospheric treatments: elevated carbon dioxide (CO2; 560 µL/L), elevated ozone (O3; ambient × 1.5), elevated CO2 and O3, or ambient air. We evaluated the effects of these fumigants on aspen foliar quality and the performance of aspen blotch leafminer (Phyllonorycter tremuloidiella Braun). 2 CO2 and O3 each affected foliar quality, with the major changes consisting of an 11% reduction in nitrogen under elevated CO2 and a 20% reduction in tremulacin under elevated O3. In the CO2 + O3 treatment, nitrogen levels were reduced by 15% and CO2 ameliorated the O3‐mediated reduction in tremulacin levels. 3 Phyllonorycter tremuloidiella were allowed to colonize trees naturally. Elevated CO2 and O3 reduced colonization rates by 42 and 49% relative to ambient CO2 and O3, respectively. The only effect of fumigation treatments on larval performance occurred under elevated O3, where male development time and larval consumption increased by 8 and 28%, respectively, over insects reared under ambient O3. 4 These data demonstrate that the individual and combined effects of CO2 and O3 can alter aspen foliar chemistry and that these alterations in foliar chemistry produce little to no change in larval performance. However, both CO2 and O3 greatly reduced oviposition. In order to ascertain the full effects of CO2 and O3 on insect performance, future studies should address both population‐ and individual‐level characteristics.  相似文献   

18.
The future capacity of forest ecosystems to sequester atmospheric carbon is likely to be influenced by CO2-mediated shifts in nutrient cycling through changes in litter chemistry, and by interactions with pollutants like O3. We evaluated the independent and interactive effects of elevated CO2 (560 μl l−1) and O3 (55 nl l l−1) on leaf litter decomposition in trembling aspen (Populus tremuloides) and paper birch (Betula papyrifera) at the Aspen free air CO2 enrichment (FACE) site (Wisconsin, USA). Fumigation treatments consisted of replicated ambient, +CO2, +O3, and +CO2 + O3 FACE rings. We followed mass loss and litter chemistry over 23 months, using reciprocally transplanted litterbags to separate substrate quality from environment effects. Aspen decayed more slowly than birch across all treatment conditions, and changes in decomposition dynamics of both species were driven by shifts in substrate quality rather than by fumigation environment. Aspen litter produced under elevated CO2 decayed more slowly than litter produced under ambient CO2, and this effect was exacerbated by elevated O3. Similarly, birch litter produced under elevated CO2 also decayed more slowly than litter produced under ambient CO2. In contrast to results for aspen, however, elevated O3 accelerated birch decay under ambient CO2, but decelerated decay under enriched CO2. Changes in decomposition rates (k-values) were due to CO2- and O3-mediated shifts in litter quality, particularly levels of carbohydrates, nitrogen, and tannins. These results suggest that in early-successional forests of the future, elevated concentrations of CO2 will likely reduce leaf litter decomposition, although the magnitude of effect will vary among species and in response to interactions with tropospheric O3.  相似文献   

19.
Elevation in CO2 concentration broadly impacts plant physiological characteristics, which influences herbivores and biotrophic pathogens, which in turn regulate the plant defensive response. In this study, responses of tobacco plants to stress in the form of the green peach aphid, Myzus persicae (Sulzer), or cucumber mosaic virus (CMV), or both aphid and CMV combined were investigated in open‐top chambers under ambient and elevated CO2 concentrations. We measured aboveground biomass and foliar chlorophyll, nitrogen, non‐structural carbohydrates, soluble protein, total amino acid and nicotine content in tobacco plants and also measured aphid population dynamics, body weight, honeydew production and anti‐oxidative enzyme activities in individual aphids. Plants produced more secondary metabolites for defence in both CO2 treatments when treated with aphid and CMV combined than with either alone. Aphid density significantly increased on CMV‐infected tobacco plants (relative to uninfected plants) under ambient CO2 but not under elevated CO2. This suggests that plant defences against virus and aphid would be more efficient under elevated CO2. Plant defence appears to shift from plant virus to aphid under increasing CO2 levels, which highlights the potential influences of multiple biotic stressors on plants under elevated CO2.  相似文献   

20.
Elevated levels of CO2 and O3 affect plant growth and phytochemistry, which in turn can alter physiological performance of associated herbivores. Little is known, however, about how generalist insect herbivores respond behaviorally to CO2‐ and O3‐mediated changes in their host plants. This research examined the effects of elevated CO2 and O3 levels on host plant preferences and consumption of forest tent caterpillar (FTC, Malacosoma disstria Hbn.) larvae. Dual choice feeding assays were performed with foliage from birch (Betula papyrifera Marsh.) and aspen (Populus tremuloides Michx., genotypes 216 and 259). Trees were grown at the Aspen Free Air CO2 Enrichment (FACE) facility near Rhinelander, WI, USA, and had been exposed to ambient or elevated concentrations of CO2 and/or O3. Levels of nutritional and secondary compounds were quantified through phytochemical analyses. The results showed that elevated O3 levels increased FTC larval preferences for birch compared with aspen, whereas elevated CO2 levels had the opposite effect. In assays with the two aspen genotypes, addition of both CO2 and O3 caused a shift in feeding preferences from genotype 259 to genotype 216. Consumption was unaffected by experimental treatments in assays comparing aspen and birch, but were increased for larvae given high O3 foliage in the aspen genotype assays. Elevated levels of CO2 and O3 altered tree phytochemistry, but did not explain shifts in feeding preferences. The results demonstrate that increased levels of CO2 and O3 can alter insect host plant preferences both between and within tree species. Also, consequences of altered host quality (e.g., compensatory consumption) may be buffered by partial host shifts in situations when alternative plant species are available. Environmentally induced changes in host plant preferences may have the potential to alter the distribution of herbivory across plant genotypes and species, as well as competitive interactions among them.  相似文献   

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