共查询到20条相似文献，搜索用时 15 毫秒
1.
Laurel J. Haavik Kevin J. Dodds Jeremy D. Allison 《Agricultural and Forest Entomology》2016,18(4):357-366
- Natural controls may not be effective in limiting non‐native species that invade a new environment. Alternatively, factors present in the new environment can prevent an invader from becoming a serious pest.
- We investigated whether existing natural enemies or the availability of susceptible and suitable host plants limited an established, non‐native species Sirex noctilio F. (Siricidae: Hymenoptera).
- Using several pine forests throughout Ontario, we examined the relationships between parasitism and S. noctilio activity, as well as S. noctilio activity and the availability of susceptible and suitable pine. We also evaluated parasitism at two points in time (5–7 years apart).
- We found correlative evidence indicating that the availability of suitable hosts limited the S. noctilio population in Ontario. Sirex noctilio killed more pine when more pine was available, especially suppressed (highly suitable) pine.
- More co‐dominant (healthy) pines were attacked but not killed by S. noctilio at sites with more S. noctilio activity, indicating that higher densities of S. noctilio were needed to overwhelm healthy pines.
- The role of parasitoids was less clear. Parasitism did not vary consistently with the amount of S. noctilio activity at sites. The two groups of parasitoids, Rhyssa and Ibalia, likely responded differently to presence of S. noctilio.
2.
1. Although in recent years there have been a number of studies demonstrating trophic cascades in terrestrial systems, it is still unclear what environmental conditions enable or enhance such cascades, especially among four trophic levels. 2. In this study, the influence of environmental stress (increased soil pore water salinity) on a four trophic level study system in a Florida salt marsh was examined by experimentally increasing soil pore water salinity. Effects of increased salinity on the quality of the host plant, Batis maritima, were assessed, as were resulting effects on the lepidopteran herbivore Ascia monuste, and the primary parasitoids and hyperparasitoids of its caterpillars. 3. Increased salinity altered host‐plant quality, which subsequently affected the consumer species. These effects of altered plant quality cascaded up through the herbivore and primary parasitoid to the hyperparasitoid Hypopteromalus inimicus, influencing its density, sex ratio, body size, and initial egg load. 4. These results demonstrate how heterogeneity in environmental stress can result in effects that cascade up through four trophic levels. We suggest that such strong effects at higher trophic levels may be more likely in systems in which relationships are more specific and intimate such as those among hosts, parasitoids, and hyperparasitoids. 相似文献
3.
1. There is an ongoing debate about the relative importance of top‐down and bottom‐up regulation of herbivore dynamics in the wild. Secondary metabolites, produced by plants, have negative effects on survival and growth of some herbivore species, causing bottom‐up regulation of population dynamics. Herbivore natural enemies may use plant secondary metabolites as cues to find their prey, but their survival and reproduction can also be influenced by the upward cascade of secondary metabolites through the food web. Thus plant chemistry might also affect herbivore populations by mediating top‐down regulation. 2. We investigated the influence of heritable variation in aliphatic glucosinolates, a class of secondary metabolites produced by Brassica plants, on the relative importance of top‐down and bottom‐up regulation of Brevicoryne brassicae (mealy cabbage aphid) colonies in natural Brassica oleracea (wild cabbage) populations. We manipulated natural enemy pressure on plants differing in their glucosinolate profiles, and monitored aphid colony growth and disperser production. 3. Aphid colony sizes were significantly smaller on plants producing sinigrin, compared with plants producing alternative aliphatic glucosinolates. Aphid natural enemy numbers correlated with aphid colony size, but there was no additional effect of the plants' chemical phenotype on natural enemy abundance. Furthermore, experimental reduction of natural enemy pressure had no effect on aphid colony size or production of winged dispersers. 4. Our results provide evidence for glucosinolate‐mediated, bottom‐up regulation of mealy cabbage aphid colonies in natural populations, but we found no indication of top‐down regulation. We emphasise that more studies of these processes should focus on tritrophic interactions in the wild. 相似文献
4.
Many herbivorous animals selectively eat flowers and unripe fruit or seeds. Some preferentially eat new tissues growing from germinating seeds. This behaviour enables access to otherwise limited or unavailable amino acids that are necessary to sustain successful production and growth of young. For the same reason the diet of breeding females and neonates of many presumed strictly herbivorous animals is supplemented with animal protein. However, because these foods are often only eaten for limited periods, and make up only a small proportion of the total diet, they are usually dismissed as unimportant to the animals' nutrition. It is suggested that actively looking for such feeding may well reveal it to be far more common and important to the successful breeding of herbivores than has been thought in the past. 相似文献
5.
Herbivorous insect communities are structured by multiple processes operating locally (e.g. bottom–up effects of plants) and regionally (e.g. dispersal limitation). Although the relative strength of these processes has been well documented, how it varies in time is less understood, especially in relation with the temporal dynamics of plant communities. If temporal turnover of local plant species composition is too rapid for insect community assembly to keep up with, bottom–up effects are expected to be weak. Here, in plant and herbivorous insect communities in Japanese grasslands, we studied how the relative importance of local (bottom–up effects of plants, structures of plant communities and top–down effects of predators) and regional (dispersal limitation) processes varies over the growing season. In addition, we tested the hypothesis that larger temporal turnover of plant species composition is related to the weaker bottom–up effects, that is, the lower explanation power of plant communities for insect communities. We found that, throughout the growing season, the insect species composition was mainly explained by local variables (plant species composition, vegetation height and predator abundance), and their explanation power was higher during later phases of the season (late summer). Furthermore, the variation not explained by plant species composition was correlated with the degree of temporal turnover of plants, suggesting that insect communities failed to track the temporal turnover of plant species. These results were pronounced when we focused on leaf sucker insects, whose host plant range is presumably more limited. We conclude that herbivorous insect communities are mainly regulated by local processes, especially bottom–up effects from plants, while stochasticity may have played a role in early phases of the season. Furthermore, we underscore the importance of considering relative time scale of community assembly and environmental shifts, especially in systems characterized by dynamic changes. 相似文献
6.
1. Stressful abiotic conditions and mycorrhizal fungi have both been shown to influence plant quality significantly, yet the interactive effects of these factors on relationships among plants, herbivores, and natural enemies remain unclear. 2. In this study, the results of a factorial field experiment are reported in which the effects of plant stress and mycorrhizae on density and parasitism of three herbivores of Baccharis halimifolia L. were examined. 3. Plant stress was increased by adding salt to the soil, and association with mycorrhizal fungi was increased by inoculating plant roots. 4. Inoculation with mycorrhizal fungi resulted in increased density of all three herbivore species, but the effects of mycorrhizae on parasitism varied by species and with soil salinity levels. For the gall maker Neolasioptera lathami Gagne, mycorrhizae decreased parasitism regardless of soil salinity levels. For the leaf miners Amauromyza maculosa Malloch and Liriomyza trifolii Burgess, mycorrhizae effectively negated the decrease in parasitism resulting from increased salinity. 5. The results of this study show that the effects of mycorrhizae on parasitism may be context dependent, and can be positive or negative depending upon species and environmental conditions. 相似文献
7.
Selina Våge Gunnar Bratbak Jorun Egge Mikal Heldal Aud Larsen Svein Norland Maria Lund Paulsen Bernadette Pree Ruth‐Anne Sandaa Evy Foss Skjoldal Tatiana M. Tsagaraki Lise Øvreås T. Frede Thingstad 《Ecology letters》2018,21(9):1440-1452
In food webs, interactions between competition and defence control the partitioning of limiting resources. As a result, simple models of these interactions contain links between biogeochemistry, diversity, food web structure and ecosystem function. Working at hierarchical levels, these mechanisms also produce self‐similarity and therefore suggest how complexity can be generated from repeated application of simple underlying principles. Reviewing theoretical and experimental literature relevant to the marine photic zone, we argue that there is a wide spectrum of phenomena, including single cell activity of prokaryotes, microbial biodiversity at different levels of resolution, ecosystem functioning, regional biogeochemical features and evolution at different timescales; that all can be understood as variations over a common principle, summarised in what has been termed the ‘Killing‐the‐Winner’ (KtW) motif. Considering food webs as assemblages of such motifs may thus allow for a more integrated approach to aquatic microbial ecology. 相似文献
8.
Steve M. Redpath John D. C. Linnell Marco Festa‐Bianchet Luigi Boitani Nils Bunnefeld Amy Dickman R. J. Gutiérrez R. J. Irvine Maria Johansson Aleksandra Majić Barry J. McMahon Simon Pooley Camilla Sandström Annelie Sjölander‐Lindqvist Ketil Skogen Jon E. Swenson Arie Trouwborst Juliette Young E. J. Milner‐Gulland 《Biological reviews of the Cambridge Philosophical Society》2017,92(4):2157-2163
Finding effective ways of conserving large carnivores is widely recognised as a priority in conservation. However, there is disagreement about the most effective way to do this, with some favouring top‐down ‘command and control’ approaches and others favouring collaboration. Arguments for coercive top‐down approaches have been presented elsewhere; here we present arguments for collaboration. In many parts of the developed world, flexibility of approach is built into the legislation, so that conservation objectives are balanced with other legitimate goals. In the developing world, limited resources, poverty and weak governance mean that collaborative approaches are likely to play a particularly important part in carnivore conservation. In general, coercive policies may lead to the deterioration of political legitimacy and potentially to non‐compliance issues such as illegal killing, whereas collaborative approaches may lead to psychological ownership, enhanced trust, learning, and better social outcomes. Sustainable hunting/trapping plays a crucial part in the conservation and management of many large carnivores. There are many different models for how to conserve carnivores effectively across the world, research is now required to reduce uncertainty and examine the effectiveness of these approaches in different contexts. 相似文献
9.
Anne‐Violette Lavoir Stéphane Adamowicz Philippe Bearez Eric Wajnberg Nicolas Desneux 《Ecology and evolution》2015,5(23):5468-5477
Omnivorous arthropods make dietary choices according to the environment in which they forage, mainly availability/quality of plant and/or prey resources. Such decisions and their subsequent impacts on life‐history traits may be affected by the availability of nutrients and water to plants, that is, through bottom‐up forces. By setting up arenas for feeding behavior observation as well as glasshouse cages for plant preference assessment, we studied effects of the presence of prey (Lepidoptera eggs) and nitrogen/water availability to host tomato plants on the foraging behavior and life‐history traits in the omnivorous predator Macrolophus pygmaeus (Heteroptera: Miridae). In the absence of prey, the predator fed equally on the plants treated with various levels of nitrogen and water. In the presence of prey, however, the feeding rate on plants decreased when the plant received low water input. The feeding rate on prey was positively correlated with feeding rate on plants; that is, prey feeding increased with plant feeding when the plants received high water input. Moreover, plants receiving high water input attracted more M. pygmaeus adults compared with those receiving low water input. For M. pygmaeus fitness, the presence of prey enhanced its fertility and longevity, but the longevity decreased when plants received low compared with high water input. In conclusion, the omnivorous predator may be obliged to feed on plants to obtain water, and plant water status may be a limiting factor for the foraging behavior and fitness of the omnivorous predator. 相似文献
10.
Geographic ranges and host plants of 10 species of Australian coreid, Gelonus tasmanicus, Acantholybas brunneus, Amorbus alternatus, Am. atomarius, Am. biguttatus, Am. bispinus, Am. obscuricornis, Am. rhombifer, Am. robustus and Am. rubiginosus, were summarized using data from specimen collection labels and sampling. One process (CLIMEX ) and two correlative range‐modelling programs (BIOCLIM and DOMAIN ) were used to infer the bioclimatic profiles of each species. By inference from the maximum range predictions made by CLIMEX , the suggestion that G. tasmanicus, Am. atomarius and Am. obscuricornis are temperate species was supported. Similarly, the suggestions that Ac. brunneus was a subtropical species and Am. biguttatus and Am. rhombifer are predominantly tropical species were supported. That Am. alternatus, Am. robustus and Am. rubiginosus are apparently ubiquitous species was supported. Comparison of the bioclimatic profiles of the habitats of G. tasmanicus and Am. obscuricornis within Tasmania using BIOCLIM supported information available in the published literature, that is, that G. tasmanicus is better suited to sites at higher elevations than Am. obscuricornis. In addition, the suggestion that the regions of high Amorbus species endemism should overlap with regions of high eucalypt species endemism was also supported. This finding is taken as evidence that the evolutionary radiation of Amorbus has followed that of the eucalypts. Using these models we have obtained preliminary insights into the biology of each species and the environmental characteristics of their preferred climatic envelope. This is an achievement that might never have been attained through concentrated study given that these insects can vary from being rare to, at best, locally common in occurrence. 相似文献
11.
Kei W. Matsubayashi Issei Ohshima & Patrik Nosil 《Entomologia Experimentalis et Applicata》2010,134(1):1-27
Divergent natural selection has been shown to promote speciation in a wide range of taxa. For example, adaptation to different ecological environments, via divergent selection, can result in the evolution of reproductive incompatibility between populations. Phytophagous insects have been at the forefront of these investigations of 'ecological speciation' and it is clear that adaptation to different host plants can promote insect speciation. However, much remains unknown. For example, there is abundant variability in the extent to which divergent selection promotes speciation, the sources of divergent selection, the types of reproductive barriers involved, and the genetic basis of divergent adaptation. We review these factors here. Several findings emerge, including the observation that although numerous different sources of divergent selection and reproductive isolation can be involved in insect speciation, their order of evolution and relative importance are poorly understood. Another finding is that the genetic basis of host preference and performance can involve loci of major effect and opposing dominance, factors which might facilitate speciation in the face of gene flow. In addition, we raise a number of other recent issues relating to phytophagous insect speciation, such as alternatives to ecological speciation, the geography of speciation, and the molecular signatures of speciation. Throughout, we aim to both synthesize what is known, as well as highlight areas where future work is especially needed. 相似文献
12.
How two different host species influence the performance of a gregarious parasitoid: host size is not equal to host quality 总被引：3，自引：0，他引：3
1. Hyssopus pallidus Askew (Hymenoptera, Eulophidae) is a gregarious ectoparasitoid of the two tortricid moths species Cydia molesta Busck and C. pomonella L. (Lepidoptera, Tortricidae). It paralyses and parasitizes different larval instars of both species inside the apple fruit, which leads to the death of the caterpillar. 2. We assessed the influence of host species characteristics and host food on the performance of the parasitoid female in terms of clutch size decisions and fitness of the F(1) generation. 3. A comparison of clutch size revealed that female parasitoids deposited similar numbers of eggs on the comparatively smaller C. molesta hosts as on the larger C. pomonella hosts. The number of parasitoid offspring produced per weight unit of host larva was significantly higher in C. molesta than in C. pomonella, which is contrary to the general prediction that smaller hosts yield less parasitoid offspring. However, the sex ratio was not influenced by host species that differed considerably in size. 4. Despite the fact that less host resources were available per parasitoid larva feeding on C. molesta caterpillars, the mean weight of emerging female wasps was higher in the parasitoids reared on C. molesta. Furthermore, longevity of these female wasps was neither influenced by host species nor by the food their host had consumed. In addition we did not find a positive relationship between adult female weight and longevity. 5. Parasitoid females proved to be able to assess accurately the nutritional quality of an encountered host and adjust clutch size accordingly. These findings indicate that host size is not equal to host quality. Thus host size is not the only parameter to explain the nutritional quality of a given host and to predict fitness gain in the subsequent generation. 相似文献
13.
Abstract. 1. A study of host preference of four pairs of populations of the cowpea weevil Callosobruchus maculates was carried out. The pairs had different geographical origins.
2. One population of each pair had been maintained for about 110 generations on cowpea Vigna unguiculata , the other population had been maintained on mung bean V. radiata . Half of the tested females from each population were raised on cowpea and exposed to this host prior to the assay; the other half was raised on mung bean. This design permitted assessment of the relative contributions of geographical origin, recent host use in the laboratory, and individual experience, to variation in host preference.
3. Host preference was assayed by letting the females oviposit on an equal-weight mixture of cowpea and mung seeds; two experiments were performed six generations apart.
4. Both experiments revealed a strong effect of geographical origin: populations originating from Nigeria laid a much greater proportion (68–86%) of their eggs on cowpea than those originating from Uganda and Yemen (30–42%); those from Cameroon were intermediate (56–60%). These preferences were not affected consistently by about 110 generations of laboratory evolution on one or the other host, or by experience of individual females.
5. These results indicate considerable geographical variation in host preference, and suggest that host preference is behaviourally inflexible and evolutionarily conserved. 相似文献
2. One population of each pair had been maintained for about 110 generations on cowpea Vigna unguiculata , the other population had been maintained on mung bean V. radiata . Half of the tested females from each population were raised on cowpea and exposed to this host prior to the assay; the other half was raised on mung bean. This design permitted assessment of the relative contributions of geographical origin, recent host use in the laboratory, and individual experience, to variation in host preference.
3. Host preference was assayed by letting the females oviposit on an equal-weight mixture of cowpea and mung seeds; two experiments were performed six generations apart.
4. Both experiments revealed a strong effect of geographical origin: populations originating from Nigeria laid a much greater proportion (68–86%) of their eggs on cowpea than those originating from Uganda and Yemen (30–42%); those from Cameroon were intermediate (56–60%). These preferences were not affected consistently by about 110 generations of laboratory evolution on one or the other host, or by experience of individual females.
5. These results indicate considerable geographical variation in host preference, and suggest that host preference is behaviourally inflexible and evolutionarily conserved. 相似文献
14.
Katarzyna Izydorczyk Aleksandra Skowron Adrianna Wojtal Tomasz Jurczak 《International Review of Hydrobiology》2008,93(3):257-268
Stream inlets into shallow bays of reservoirs and lakes may be ‘hot‐spots’ for toxic cyanobacterial bloom initiation. These ‘hot‐spots’ may be connected with the permanent inflow of high nutrient concentrations from the catchment, optimal physical conditions (wind protected areas) that occur in shallow areas and/or ineffective top‐down control. Four sampling sites along a transect from stream to reservoir in a shallow bay of Sulejow Reservoir (Poland) were studied to test the above hypothesis, comprising a transition zone between lotic and pelagic habitats. Investigations showed that stream inlet into shallow bay acted as incubator for Microcystis blooms. The nutrient level, especially phosphorus, was identified as the major cause of cyanobacterial bloom growth. The increase of Microcystis biomass strongly correlated with increasing microcystin concentrations, however, a relationship with microcystin content was not observed. Toxicity of bloom demonstrated seasonal variability, reaching its maximum at the initial phase of bloom. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
15.
16.
BANKER PLANT携带天敌防治害虫的理论基础与应用 总被引：1，自引：0，他引：1
滥用农药导致粮食、蔬菜和水果内有毒农药高残留,严重威胁着人民的生命安全;利用生物防治害虫将提供更安全的食品和洁净的环境。Banker植物系统是利用非作物植物饲养及携带天敌的寄主或猎物,再利用天敌的寄主或猎物饲养和释放天敌。这些Banker植物就像是一个‘银行家(Banker)’,连续不断地供应‘货币’(天敌),使天敌从‘银行家’植物上扩散到有害虫的作物上防治害虫,是生物防治发展的一个重要方向。本文系统介绍了利用Banker植物为替代寄主饲养释放天敌防治害虫的最新进展,旨在推动我国更好地开展Banker植物系统及其相关理论与应用的研究。 相似文献
17.
Multiple predators often have effects on their common prey populations that cannot be predicted by summing the effects of each predator at a time. When predators forage on the same vegetation substrate, intraguild interactions might cause emergent outcomes for the plants on which the predators co‐occur. We experimentally evaluated the effects of spiders and ants on herbivory and reproduction in the extrafloral nectary‐bearing tree Qualea multiflora (Vochysiaceae). Plants were divided in four experimental groups, depending on the presence or absence of ants and spiders. We compared the effects of each treatment on richness and abundance of chewing and sucking herbivores and on herbivory (leaf area loss). We also evaluated the impact of predators on the production of buds, fruits and seeds, and weight of the fruits. The presence of ants reduced the abundance and richness of spiders, but spiders did not affect the abundance and richness of ants. Only the removal of ants resulted in a significant increase in the abundance of herbivores and herbivore richness. Herbivory, however, was also affected by spiders. In addition, we found a significant interaction effect of ants and spiders on herbivory, indicating an emergent multiple predator effect. Neither ants nor spiders had an impact on the number of buds produced, number of fruits per bud, and seeds per fruits or fruit weight. This study highlights the importance of evaluating the effect of the predator fauna as a whole and not only one specific group on herbivory. 相似文献
18.
- Top‐down population regulation can influence the success of biological control agents when they are released into the field. Entomopathogenic nematodes (EPNs) are used commonly in biological control programmes, but their efficacy suffers from poor persistence. Although abiotic soil conditions have been shown to reduce EPN persistence, consumption of infected insects by scavengers and of infective juvenile (IJ) nematodes by predators may also regulate these populations. In the present study, the effects of different soil arthropods on EPNs in laboratory conditions were measured. It was hypothesised that arthropods commonly found in soil communities where EPNs are applied would consume cadavers of insects parasitised by the nematodes and the IJs themselves.
- Some species of scavengers consume EPN‐infected insects. Crickets (Gryllus bimaculatus De Geer), American cockroaches [Periplaneta Americana (Linnaeus)], ants [Tetramorium chefketi Forel and Pheidole pallidula (Nylander)], earwigs (Labidura riparia Pallas), mites (Sancassania polyphyllae Zachvatkin), and springtails (Sinella curviseta Brook and Folsomia candida Willem) have different responses to nematode‐killed insects. Results suggested that ants (T. chefketi), cockroaches, mites, and earwigs fed on Steinernema‐killed insects whereas neither crickets nor springtails consumed them.
- In the second part of the study, experiments were conducted to determine whether mites and springtails consumed IJ EPNs. Results showed that S. polyphyllae mites do not consume infective juveniles in soil, whereas both springtail species consumed significant numbers of the IJs.
- Top‐down regulatory processes can be a limiting factor for EPN populations under laboratory conditions. Both host cadavers and IJs are consumed (albeit by different arthropods), so these results may help explain the difficulties associated with the persistence of EPN application to soil.
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20.
Francisco Rivera Vasconcelos Sebastian Diehl Patricia Rodríguez Per Hedstrm Jan Karlsson Pr Bystrm 《Global Change Biology》2019,25(2):504-521
Productivity and trophic structure of aquatic ecosystems result from a complex interplay of bottom‐up and top‐down forces that operate across benthic and pelagic food web compartments. Projected global changes urge the question how this interplay will be affected by browning (increasing input of terrestrial dissolved organic matter), nutrient enrichment and warming. We explored this with a process‐based model of a shallow lake food web consisting of benthic and pelagic components (abiotic resources, primary producers, grazers, carnivores), and compared model expectations with the results of a browning and warming experiment in nutrient‐poor ponds harboring a boreal lake community. Under low nutrient conditions, the model makes three major predictions. (a) Browning reduces light and increases nutrient supply; this decreases benthic and increases pelagic production, gradually shifting productivity from the benthic to the pelagic habitat. (b) Because of active habitat choice, fish exert top‐down control on grazers and benefit primary producers primarily in the more productive of the two habitats. (c) Warming relaxes top‐down control of grazers by fish and decreases primary producer biomass, but effects of warming are generally small compared to effects of browning and nutrient supply. Experimental results were consistent with most model predictions for browning: light penetration, benthic algal production, and zoobenthos biomass decreased, and pelagic nutrients and pelagic algal production increased with browning. Also consistent with expectations, warming had negative effects on benthic and pelagic algal biomass and weak effects on algal production and zoobenthos and zooplankton biomass. Inconsistent with expectations, browning had no effect on zooplankton and warming effects on fish depended on browning. The model is applicable also to nutrient‐rich systems, and we propose that it is a useful tool for the exploration of the consequences of different climate change scenarios for productivity and food web dynamics in shallow lakes, the worldwide most common lake type. 相似文献