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1.
The majority of generalisations concerning plant responses to herbivory are based on studies of natural or simulated defoliation.
However, effects caused by insects feeding on plant sap are likely to differ from the effects of folivory. We assessed the
general patterns and sources of variation in the effects of sap feeding on growth, photosynthesis, and reproduction of woody
plants through a meta-analysis of 272 effect sizes calculated from 52 papers. Sap-feeders significantly reduced growth (−29%),
reproduction (−17%), and photosynthesis (−27%); seedlings suffered more than saplings and mature trees. Deciduous and evergreen
woody plants did not differ in their abilities to tolerate damage imposed by sap-feeders. Different plant parts, in particular
below- and above-ground organs, responded similarly to damage, indicating that sap-feeders did not change the resource allocation
in plants. The strongest effects were caused by mesophyll and phloem feeders, and the weakest by xylem feeders. Generalist
sap-feeders reduced plant performance to a greater extent than did specialists. Methodology substantially influenced the outcomes
of the primary studies; experiments conducted in greenhouses yielded stronger negative effects than field experiments; shorter
(<12 months) experiments showed bigger growth reduction in response to sap feeding than longer experiments; natural levels
of herbivory caused weaker effects than infestation of experimental plants by sap-feeders. Studies conducted at higher temperatures
yielded stronger detrimental effects of sap-feeders on their hosts. We conclude that sap-feeders impose a more severe overall
negative impact on plant performance than do defoliators, mostly due to the lower abilities of woody plants to compensate
for sap-feeders’ damage in terms of both growth and photosynthesis. 相似文献
2.
Summary The effects of endophytic fungi (Tribe Balansiae, Clavicipitaceae, Ascomycetes) of grasses on an insect herbivore were studied by feeding paired groups of larvae of the fall armyworm (Spodoptera frugiperda, Noctuidae, Lepidoptera) leaves from either infected or uninfected individuals. Perennial ryegrass infected by the Lolium endophyte, tall fescue infected by Epichloe typhina, dallisgrass infected by Myriogenospora atramentosa, Texas wintergrass infected by Atkinsonella hypoxylon, and sandbur infected by Balansia obtecta were utilized. The endophytes of ryegrass and fescue previously have been shown to be toxic to mammalian herbivores and to deter feeding of some insect herbivores. In this study we extend the antiherbivore properties of those endophytes to the fall armyworm and demonstrate that fungal endophytes in three other genera have similar antiherbivore properties. For most grasses, survival and weights of fall armyworm larvae fed infected leaves were significantly lower and larval duration was significantly longer compared to larvae fed uninfected leaves. Resistance to herbivores may provide a selective advantage to endophyte-infected grasses in natural populations. 相似文献
3.
To assess the pattern of temperature influencing the effect of allelochemicals on growth of insect herbivores and to examine the potential effect of warmer nights due to global warming, we examined the simultaneous effects of allelochemicals and warmer night-time temperatures on an insect herbivore (Spodoptera exigua; Lepidoptera: Noctuidae). Dietary chlorogenic acid, rutin and tomatine levels reflected those occurring naturally in the leaves of tomato, a hostplant of this herbivore. We compared the effects of four thermal regimes having a daytime temperature of 26 °C , with the night-time temperature increased from 14 to 26 °C by increments of 4 °C . The effect of a particular allelochemical on developmental rate was similar among the four thermal regimes. Chlorogenic acid and tomatine each reduced final larval weight, but there was no effect of night-time temperature. In contrast, rutin had no effect on final weight, whereas final weight declined with increasing night-time temperature. Night-time temperature did not influence amount eaten. Larvae ate less when chlorogenic acid or tomatine was in the diet. For each allelochemical, there were no allelochemical by thermal regime interactions. In addition, we compared the effects of allelochemicals and the thermal regime of 26:14 °C and constant 20 °C , which was the average temperature of the 26:14 °C regime. Developmental rate was lower at the constant 20 °C regime, chlorogenic acid and tomatine each depressed developmental rate, and there were no allelochemical by thermal regime interactions. Thus, regardless of the specific allelochemical or amount, the pattern of response at the fluctuating regime was similar to that at the constant temperature. In contrast, comparison of the thermal regime of 26:22 °C and constant 24 °C , which was the average temperature of the 26:22 °C regime, showed several allelochemical by thermal regime interactions. At the 26:22 °C regime, developmental rate was disproportionatly higher at the maximal rutin concentration compared to that at constant 24 °C . At the constant 24 °C , final larval mass was disproportionately lower at the moderate tomatine concentration compared to that at the 26:22 °C regime. Because these results differ from that of other studies examining another species, it appears that the response to incremental changes in night-time temperature will reflect the allelochemicals and insect species tested. The contrast between the constant 24 °C and 26:22 °C regimes indicates that even small fluctuations (±2 °C ) in temperature over 24 h can yield differences in the response to an allelochemical. 相似文献
4.
5.
天敌是影响害虫种群动态的重要因素。一般认为天敌对害虫作用的方式,主要是通过直接的捕食或寄生。事实上,天敌还可以通过捕食或寄生过程中产生的"威吓"等非直接致死效应(Non-lethal effects)或胁迫作用(Stress),影响着害虫的生长发育、繁殖。有时这种天敌存在的非直接致死效应对害虫产生的负面影响甚至比天敌对害虫的直接捕食作用还强。显然,评价天敌作用时,除了计算天敌对害虫的直接捕食或寄生的效率,还应考虑天敌存在时对害虫的非直接致死效应。本文基于作者及前人的研究,分别论述了捕食性天敌、寄生性天敌对害虫的非直接致死效应,解析了环境变化对天敌非直接致死效应的影响,探讨了这种非直接致死效应的可能机制,提出了未来的研究发展方向。 相似文献
6.
One effect of global warming may be an increase in night-time temperatures with daytime temperatures remaining largely unchanged. We examined this potential effect of global warming on the performance of tobacco hornworm larvae, Manduca sexta (Sphingidae), by manipulating night-time temperature and dietary rutin levels simultaneously under a 12 light:12 dark photoregime. All four thermal regimes (26:14, 26:18, 26:22, and 26:26° C) had a daytime temperature of 26° C, with the night-time temperature increased from 14 to 26° C by increments of 4° C. Dietary rutin levels (0, 10 and 20 moles g–1 fresh weight of diet) reflected those occurring naturally in the leaves of tomato, a preferred host plant of M. sexta. With low night-time temperatures (14 and 18° C), rutin had a negative linear effect on developmental rate, relative growth rate and relative consumption rate of the caterpillars. However, at a night-time temperature of 22° C, rutin had a negative non-linear effect. At a night-time temperature of 26° C, rutin had a negative linear impact but less so than at the other nightime temperatures. Likewise, the negative effect of rutin on molting duration was mitigated as night-time temperature increased. Final larval weight decreased linearly with increased dietary rutin concentrations. Total amount of food ingested was not affected by either rutin or thermal regime. As expected, the caterpillars developed faster under an alternating 26:14° C regime than a constant 20° C regime (the average temperature for the alternating regime), but the effect of rutin depended on the thermal regime. Switching daytime and night-time temperatures had no statistically significant effect on caterpillar performance. Overall, the effect of rutin on rates of larval performance was greater at some levels of warmer nights but damped at another level. These results indicate that the potential effect of warmer nights on insect performance is not a simple function of temperature because there can be interactions between night-time temperature and dietary allelochemicals. 相似文献
7.
Two models for assessing the performance of herbivores on a variety of host plants are developed by combining knowledge of population genetics and population ecology, especially that of the fixation probability of mutant genes. The absolute host performance model precisely assesses host performance for one herbivore population based on parameters of fecundity, larval survivorship, and selection pressure. The relative host performance model compares host performance for one population among different host plant species and for several populations on the same host species. Two herbivore populations, Bemisia tabaci (Gennadius) and Tetranychus truncates Ehara, were used to validate the absolute and relative host performance models. Results indicated that the assessment systems of host performance were reasonable and reliable. These models could be applied to a wide range of herbivore species for assessing their performance on host plants. 相似文献
8.
Arbuscular mycorrhizal (AM) fungi can indirectly affect insect herbivore performance by altering traits in their host plant. Typically, generalist herbivores are negatively affected by AM fungi, whereas specialists are positively affected. This is thought to be caused by differential abilities of specialists and generalists to tolerate and/or exploit plant secondary compounds, the prevalence of which may be related to mycorrhizal colonization. We performed a feeding experiment in which specialist sunflower beetle larvae (Zygogramma exclamationis Fabricius, Chrysomelidae) were fed on mycorrhizal or nonmycorrhizal common annual sunflower plants (Helianthus annuus L., Asteraceae). To determine the indirect effects of AM fungi on the sunflower beetle larvae, we measured insect survival and relative growth rate. We also measured leaf area eaten, which allowed relative growth rate to be broken down into two components: relative consumption rate and efficiency of conversion of ingested food. Contrary to several previous studies, we detected no indirect effects of mycorrhizal fungi on larval survival or on relative growth rate or its components. Small effect sizes suggest that this is nonsignificant biologically, as well as statistically, rather than merely an issue of statistical power. Our results support an emerging view that indirect effects of mycorrhizal fungi on insect herbivores may be complex and idiosyncratic. We suggest that future research should emphasize the effects of mycorrhizal fungi on individual plant traits and how these interact to affect insect performance. 相似文献
9.
This study examined the effects of increased leaf nitrogen in natural host-plants (Plantago spp.) on female oviposition preference, larval performance, and larval chemical defense of the butterfly Junonia coenia. Increased availability of soil nutrients caused the host-plant’s foliar nitrogen to increase and its chemical defense to
decrease. Larval performance did not correlate with increases in foliar nitrogen. Larval growth rate and survival were equivalent
across host-plant treatments. However, larvae raised on fertilized host-plants showed concomitant decreases in chemical defense
as compared to larvae reared on unfertilized host-plants. Since most butterfly larvae cannot move long distances during their
first few instars and are forced to feed upon the plant on which they hatched, J. coenia larval chemical defense is determined, in large part, by female oviposition choice. Female butterflies preferred host-plants
with high nitrogen over host-plants with low nitrogen; however, this preference was also mediated by plant chemical defense.
Female butterflies preferred more chemically defended host-plants when foliar nitrogen was equivalent between host-plants.
J. coenia larvae experience intense predation in the field, especially when larvae are not chemically well defended. Any qualitative
or quantitative variation in plant allelochemical defense has fitness consequences on these larvae. Thus, these results indicate
that females may be making sub-optimal oviposition decisions under a nutrient-enriched regime, when predators are present.
Given the recent increase in fertilizer application and nitrogen deposition on the terrestrial landscape, these interactions
between female preference, larval performance, and larval chemical defense may result in long-term changes in population dynamics
and persistence of specialist insects. 相似文献
10.
Induced herbivore resistance in seaweeds: a meta-analysis 总被引:3,自引:0,他引:3
11.
Susan J. Richardson-Kageler 《Biodiversity and Conservation》2004,13(11):2145-2163
This study examined the effect of different large herbivore species and stocking rates in savanna ecosystems of Zimbabwe on the richness and abundances of woody plant functional groups and woody plant functional attributes. Seven fence-lines with different herbivore species and stocking rates on either side of the fence were sampled. Plots were placed on both sides of each fence at each of 18 randomly selected positions. The size and species of each woody plant was recorded for each plot. It was found that the number of species with different functional attributes of spinescence, leaf longevity, fruit type and dispersal mechanism and in the functional groups of palatability were not different on the different sides of the fence. However, there were differences in plant abundances for 26 out of the 35 tests carried out on plant abundances with different functional attributes and functional groups. It was hypothesised that the time needed to change woody plant species richness is hundreds of years in these systems, whereas the time needed to change woody plant abundances is decades. 相似文献
12.
Endophytic fungal symbionts of grasses are well known for their protective benefit of herbivory reduction. However, the majority
of studies on endophyte–grass symbioses have been conducted on economically important, agricultural species—particularly tall
fescue (Lolium arundinaceum) and perennial ryegrass (Lolium perenne)—raising the hypothesis that strong benefits are the product of artificial selection. We examined whether fungal endophytes
found in natural populations of native grass species deterred insect herbivores. By testing several native grass–endophyte
symbiota, we examined phylogenetic signals in the effects of endophytes on insects and compared the relative importance of
herbivore and symbiotum identity in the outcome of the interactions. Preference was assessed using three herbivore species
[Spodoptera frugiperda (Lepidoptera), Schistocerca americana (Orthoptera), Rhopalosiphum padi (Hemiptera)] and ten native symbiota, which spanned seven grass genera. We also assessed herbivore performance in a no choice
experiment for five native symbiota against S. frugiperda. We compared greenhouse and laboratory trials with natural levels of herbivory measured in experimental field populations.
In all cases, we included the agronomic grass species, L. arundinaceum, to compare with results from the native grasses. Both in the field and in experimental trials, herbivores showed a significant
preference for endophyte-free plant material for the majority of native grasses, with up to three times lower herbivory for
endophyte-symbiotic plants; however, the degree of response depended on the identity of the herbivore species. Endophyte presence
also significantly reduced performance of S. frugiperda for the majority of grass species. In contrast, the endophyte in L. arundinaceum had few significant anti-herbivore effects, except for a reduction in herbivory at one of two field sites. Our results demonstrate
that the mechanisms by which native symbionts deter herbivores are at least as potent as those in model agricultural systems,
despite the absence of artificial selection. 相似文献
13.
Recent studies have suggested that associational resistance (AR) should be more effective in protecting plants from grazing by mammals than by herbivorous insects. We tested this hypothesis in a multiple-herbivore system by comparing herbivory on, and reproductive success of, fireweed plants growing within meadowsweet stands with fireweeds growing outside meadowsweet stands in abandoned fields in Northern Sweden. We showed that meadowsweet mediates AR against shared mammal grazers, but not against shared insect herbivores. The risk of fireweed plants being browsed by mammals when growing in the absence of meadowsweet was at least double (41?% affected) that of plants growing within meadowsweet patches (17.5?% affected). We also showed that whereas mammal browsing had a negative effect on fireweed performance, the effect of insect herbivory was negligible. Our results support the hypothesis that AR is more effective against grazing mammals than against herbivorous insects. 相似文献
14.
Synergistic effects of an extreme weather event and habitat fragmentation on a specialised insect herbivore 总被引:1,自引:0,他引:1
Habitat fragmentation is considered to be one of the main causes of population decline and species extinction worldwide. Furthermore,
habitat fragmentation can decrease the ability of populations to resist and to recover from environmental disturbances such
as extreme weather events, which are expected to occur at an increasing rate as a result of climate change. In this study,
we investigated how calcareous grassland fragmentation affected the impact of the climatically extreme summer of 2003 on egg
deposition rates, population size variation and survival of the blue butterfly Cupido minimus, a specialist herbivore of Anthyllis vulneraria. Immediately after the 2003 summer heat wave, populations of the host plant declined in size; this was paralleled with decreases
in population size of the herbivore and altered egg deposition rates. In 2006 at the end of the monitoring period, however,
most A. vulneraria populations had recovered and only one population went extinct. In contrast, several butterfly populations had gone extinct
between 2003 and 2006. Extinction probability was significantly related to initial population size, with small populations
having a higher risk of extinction than large populations. These results support the prediction that species of higher trophic
levels are more susceptible to extinction due to habitat fragmentation and severe disturbances. 相似文献
15.
A generalist feeding strategy is common among eruptive insect herbivores but the ultimate reasons for a generalist strategy
are not clear. Although generalist insect herbivores are able to complete their life cycle on several species of host plants,
there is wide variation in the performance of individuals grown on different hosts. We examined whether different populations
of Operophtera brumata are adapted to use the host species which is locally most abundant, and how the host plant affects growth and development
of the insect. We reared two allopatric populations (eastern Finland, Prunus padus; south-west Finland, Quercus robur) on four species of host plants (Pr. padus, Populus tremula, Q. robur, Salix phylicifolia) from neonate larvae to the adult stage and measured the growth and development of individuals and the timing of adult hatching.
The performance of both populations was best on Pr. padus, and the south-western population, originally on Q. robur, was well adapted to this host. The host affected the growth of females more than that of males. The host plant had an unexpected
effect on hatching times of the adults. Individuals grown on the original host hatched in normal synchrony, i.e. males 6–7
days before females; but on alternative hosts this synchrony was disturbed. As is common in eruptive, capital-breeding generalist
moths where female fecundity is linked to weight, host quality is critical for the flightless females of O. brumata. We suggest that in a heterogeneous environment the disturbing effect of alternative host plants on adult emergence may decrease
the population density and growth rate compared to the potential maximum in a homogeneous environment.
Received: 8 July 1999 / Accepted: 29 October 1999 相似文献
16.
While soil resource heterogeneity and root herbivory can have significant direct influences on plant growth, soil heterogeneity
may also have indirect effects by influencing the foraging behavior of root herbivores. We used sand-filled greenhouse pots
to assess root herbivore foraging behavior and potential interactions between patch quality, herbivore foraging, and plant
biomass production (yield). Individual pots were divided into four quarters: one fertilized, and three unfertilized, two of
which were planted with tree seedlings. Two treatments were used to create fertilized quarters: high-organic manure fertilizer,
and slow-release mineral fertilizer. Seedlings of red maple (Acer rubrum L.) and Virginia pine (Pinus virginiana L.) were used to create two single-species and one mixed-species treatments. Root-feeding beetle larvae were added to the
pots and allowed to forage freely for ∼8 weeks. At harvest, root herbivores in organic-fertilized pots were strongly attracted
to fertilized quarters despite their relatively low-root biomass. Herbivore distribution was significantly different in mineral
fertilized pots, where larvae were most abundant in planted quarters, which is also where most of the plant roots occurred.
Whole pot plant yield was significantly reduced by larvae; this effect was stronger in the mineral fertilized pots than organic
fertilized pots. While one of the plant species appeared more sensitive to herbivory, root herbivores had a greater influence
on yield in mixed-species pots than in single-species pots. Overall, these results suggest that patch quality influences on
herbivore foraging may indirectly alter yield and plant community composition.
Responsible Editor: Angela Hodge. 相似文献
17.
Advantages of a mixed diet: feeding on several foliar age classes increases the performance of a specialist insect herbivore 总被引:5,自引:0,他引:5
Two field studies were carried out to determine the influence of Abies balsamea foliage age on the preference and performance of larvae of Neodiprion abietis, a specialist Diprionid sawfly. Preference was determined by examining N. abietis defoliation on all age classes of foliage. Performance was estimated using larval survival, cocoon weights and the percentage of adults that were females. Neodiprion abietis preference for, and performance on, current-year foliage was very low, peaked on 2 or 3-year-old foliage, and declined on older foliage. Thus, sawfly feeding preference was adaptive. However, survival and cocoon weight were highest when sawflies were allowed to feed on all age classes of foliage, demonstrating that an insect specialist may perform better when feeding on several age classes of foliage from a single host plant species. These results indicate that either different larval instars have different nutritional requirements, or that food mixing provides the best diet, permitting the herbivore to obtain needed nutrients while avoiding ingestion of toxic doses of secondary metabolites. In addition, our results suggest that limited availability of varied foliage has more negative consequences for N. abietis females than for males, as the percentage of survivors that were females decreased when juvenile mortality was high. Our results emphasize the importance of considering non-linear changes in foliar quality as leaves age on herbivore preference and performance, and demonstrate how a herbivore can use this variability to maximize its fitness. 相似文献
18.
Sáez de Villarreal E Requena B Cronin JB 《Journal of strength and conditioning research / National Strength & Conditioning Association》2012,26(2):575-584
The purpose of this meta-analysis was to attempt to gain a clear picture of the magnitude of sprint performance improvements expected after chronic plyometric training (PT) and to identify specific factors that influence the treatment effects. Studies employing a PT intervention and containing data necessary to calculate effect size (ES) were included in the analysis. A total of 26 studies with a total of 56 ES met the inclusion criterion. Analysis of ES demonstrated that the strategies that seem to maximize the probability of obtaining significantly (p < 0.05) greater improvement in sprint performance included training volume for <10 weeks; a minimum of 15 sessions; and high-intensity programs with >80 combined jumps per session. To optimize sprint enhancement, the combination of different types of plyometrics and the use of training programs that incorporate greater horizontal acceleration (i.e., sprint-specific plyometric exercises, jumps with horizontal displacement) would be recommended, rather than using only one form of jump training (p < 0.05). No extra benefits were found to be gained from doing plyometrics with added weight. The loading parameters identified in this analysis should be considered by the professional sprinters and specialized trainers with regard to the most appropriate dose-response trends PT to optimized sprint performance gains. 相似文献
19.
Demographic models reveal the shape of density dependence for a specialist insect herbivore on variable host plants 总被引:1,自引:0,他引:1
Miller TE 《The Journal of animal ecology》2007,76(4):722-729
1. It is widely accepted that density-dependent processes play an important role in most natural populations. However, persistent challenges in our understanding of density-dependent population dynamics include evaluating the shape of the relationship between density and demographic rates (linear, concave, convex), and identifying extrinsic factors that can mediate this relationship. 2. I studied the population dynamics of the cactus bug Narnia pallidicornis on host plants (Opuntia imbricata) that varied naturally in relative reproductive effort (RRE, the proportion of meristems allocated to reproduction), an important plant quality trait. I manipulated per-plant cactus bug densities, quantified subsequent dynamics, and fit stage-structured models to the experimental data to ask if and how density influences demographic parameters. 3. In the field experiment, I found that populations with variable starting densities quickly converged upon similar growth trajectories. In the model-fitting analyses, the data strongly supported a model that defined the juvenile cactus bug retention parameter (joint probability of surviving and not dispersing) as a nonlinear decreasing function of density. The estimated shape of this relationship shifted from concave to convex with increasing host-plant RRE. 4. The results demonstrate that host-plant traits are critical sources of variation in the strength and shape of density dependence in insects, and highlight the utility of integrated experimental-theoretical approaches for identifying processes underlying patterns of change in natural populations. 相似文献
20.
We tested the hypothesis that avocado idioblast oil cells play a defensive role against herbivorous insects. Toxicities of the intact avocado idioblast oil cells and the extracted idioblast oil were compared for three insect herbivores. Spodoptera exigua (Hübner) larvae are generalists that do not feed on avocados. By contrast, Sabulodes aegrotata (Guenée) and Pseudoplusia includens (Walker) larvae are generalist herbivores that readily feed on avocados. All bioassays were performed at a naturally occurring concentration of idioblast oil cells (2% w/w). Choice experiments showed that S. exigua larvae avoided diet treated with avocado idioblast oil cells and consume more control than treated diet. In contrast, idioblast oil cells had no significant antifeedant effects on the adapted S. aegrotata and P. includens larvae. Subsequent experiments designed to assess resistance mechanisms separated pre-ingestive (behavioral) and post-ingestive (physiological) effects of the avocado idioblast oil cells, and the extracted idioblast oil, on the two adapted herbivores. Post-ingestive adaptation was the mechanism that allows feeding. Because the impact of the avocado idioblast oil cells was greatest on the performance of non-adapted S. exigua, additional experiments determined that larvae fed diet containing the oil cells had higher mortality and reduced larval growth compared to controls. Developmental times were significantly prolonged for the survivors. Thus, increased mortality, reduced developmental rates, and antifeedant activity in the non-adapted insect indicate that defense against non-adapted herbivores may be an important function of idioblast cells in avocados. 相似文献