scholarly journals Aphid–parasitoid community structure on genetically modified wheat

2011 ◽  
Vol 7 (3) ◽  
pp. 387-391 ◽  
Author(s):  
Simone von Burg ◽  
Frank J. F. van Veen ◽  
Fernando Álvarez-Alfageme ◽  
Jörg Romeis
Keyword(s):  
Community Structure ◽  
Food Webs ◽  
Genetically Modified ◽  
Insect Community ◽  
Food Web Structure ◽  
Wheat Varieties ◽  
Aphid Parasitoid ◽  
Gm Plants ◽  
Wheat Lines ◽  
The Impact

Since the introduction of genetically modified (GM) plants, one of the main concerns has been their potential effect on non-target insects. Many studies have looked at GM plant effects on single non-target herbivore species or on simple herbivore–natural enemy food chains. Agro-ecosystems, however, are characterized by numerous insect species which are involved in complex interactions, forming food webs. In this study, we looked at transgenic disease-resistant wheat ( Triticum aestivum ) and its effect on aphid–parasitoid food webs. We hypothesized that the GM of the wheat lines directly or indirectly affect aphids and that these effects cascade up to change the structure of the associated food webs. Over 2 years, we studied different experimental wheat lines under semi-field conditions. We constructed quantitative food webs to compare their properties on GM lines with the properties on corresponding non-transgenic controls. We found significant effects of the different wheat lines on insect community structure up to the fourth trophic level. However, the observed effects were inconsistent between study years and the variation between wheat varieties was as big as between GM plants and their controls. This suggests that the impact of our powdery mildew-resistant GM wheat plants on food web structure may be negligible and potential ecological effects on non-target insects limited.

scholarly journals Untangling the roles of parasites in food webs with generative network models

2015 ◽  
Author(s):  
Abigail Z. Jacobs ◽  
Jennifer A. Dunne ◽  
Cristopher Moore ◽  
Aaron Clauset
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Statistical Physics ◽  
Network Models ◽  
Food Web Structure ◽  
Free Living ◽  
Web Structure ◽  
Living Species ◽  
Parasitic Interactions ◽  
The Impact

Food webs represent the set of consumer-resource interactions among a set of species that co-occur in a habitat, but most food web studies have omitted parasites and their interactions. Recent studies have provided conflicting evidence on whether including parasites changes food web structure, with some suggesting that parasitic interactions are structurally distinct from those among free-living species while others claim the opposite. Here, we describe a principled method for understanding food web structure that combines an efficient optimization algorithm from statistical physics called parallel tempering with a probabilistic generalization of the empirically well-supported food web niche model. This generative model approach allows us to rigorously estimate the degree to which interactions that involve parasites are statistically distinguishable from interactions among free-living species, whether parasite niches behave similarly to free-living niches, and the degree to which existing hypotheses about food web structure are naturally recovered. We apply this method to the well-studied Flensburg Fjord food web and show that while predation on parasites, concomitant predation of parasites, and parasitic intraguild trophic interactions are largely indistinguishable from free-living predation interactions, parasite-host interactions are different. These results provide a powerful new tool for evaluating the impact of classes of species and interactions on food web structure to shed new light on the roles of parasites in food webs.

Bacterial communities of the rhizosphere and endorhiza associated with field-grown cucumber plants inoculated with a plant growth-promoting rhizobacterium or its genetically modified derivative

1997 ◽  
Vol 43 (4) ◽  
pp. 344-353 ◽  
Author(s):  
W. F. Mahaffee ◽  
J. W. Kloepper
Keyword(s):  
Community Structure ◽  
Bacterial Community ◽  
Bacterial Communities ◽  
Genetically Modified ◽  
Acid Methyl Ester ◽  
Wild Type ◽  
Natural Ecosystems ◽  
Genus Level ◽  
Plant Growth Promoting ◽  
The Impact

The future use of genetically modified microorganisms in the environment will be dependent on the ability to assess potential or theoretical risks associated with their introduction into natural ecosystems. To assess potential risks, several ecological parameters must be examined, including the impact of the introduced genetically modified organism on the microbial communities associated with the environment into which the introduction will occur. A 2-year field study was established to examine whether the indigenous bacterial communities of the rhizosphere and endorhiza (internal root tissues) were affected differently by the introduction of an unaltered wild type and its genetically modified derivative. Treatments consisted of the wild-type strain Pseudomonas fluorescens 89B-27 and a bioluminescent derivative GEM-8 (89B-27::Tn4431). Cucumber root or seed samples were taken 0, 7, 14, 21, 35, and 70 days after planting (DAP) in 1994 and 0, 7, 14, 28, 42, and 70 DAP in 1995. Samples were processed to examine the bacterial communities of both the rhizosphere and endorhiza. Over 7200 bacterial colonies were isolated from the rhizosphere and endorhiza and identified using the Sherlock System (Microbial ID, Inc.) for fatty acid methyl ester analysis. Community structure at the genus level was assessed using genera richness and Hill's diversity numbers, N1 and N2. The aerobic–heterotrophic bacterial community structure at the genus level did not significantly vary between treatments but did differ temporally. The data indicate that the introduction of the genetically modified derivative of 89B-27 did not pose a greater environmental risk than its unaltered wild type with respect to aerobic–heterotrophic bacterial community structure.Key words: diversity, ecology, PGPR, Pseudomonas, root colonizaton, GEM.

scholarly journals Warming shifts top-down and bottom-up control of pond food web structure and function

2012 ◽  
Vol 367 (1605) ◽  
pp. 3008-3017 ◽  
Author(s):  
Jonathan B. Shurin ◽  
Jessica L. Clasen ◽  
Hamish S. Greig ◽  
Pavel Kratina ◽  
Patrick L. Thompson
Keyword(s):  
Food Webs ◽  
Environmental Changes ◽  
Lytic Cycle ◽  
Top Down ◽  
Food Web Structure ◽  
Bottom Up ◽  
Positive Effects ◽  
Freshwater Pond ◽  
Aquatic Food ◽  
The Impact

The effects of global and local environmental changes are transmitted through networks of interacting organisms to shape the structure of communities and the dynamics of ecosystems. We tested the impact of elevated temperature on the top-down and bottom-up forces structuring experimental freshwater pond food webs in western Canada over 16 months. Experimental warming was crossed with treatments manipulating the presence of planktivorous fish and eutrophication through enhanced nutrient supply. We found that higher temperatures produced top-heavy food webs with lower biomass of benthic and pelagic producers, equivalent biomass of zooplankton, zoobenthos and pelagic bacteria, and more pelagic viruses. Eutrophication increased the biomass of all organisms studied, while fish had cascading positive effects on periphyton, phytoplankton and bacteria, and reduced biomass of invertebrates. Surprisingly, virus biomass was reduced in the presence of fish, suggesting the possibility for complex mechanisms of top-down control of the lytic cycle. Warming reduced the effects of eutrophication on periphyton, and magnified the already strong effects of fish on phytoplankton and bacteria. Warming, fish and nutrients all increased whole-system rates of net production despite their distinct impacts on the distribution of biomass between producers and consumers, plankton and benthos, and microbes and macrobes. Our results indicate that warming exerts a host of indirect effects on aquatic food webs mediated through shifts in the magnitudes of top-down and bottom-up forcing.

scholarly journals The perception of genetically modified plants by farmers in Szabolcs-Szatmár-Bereg County, Hungary

2021 ◽  
pp. 73-77
Keyword(s):  
Agricultural Education ◽  
Genetically Modified ◽  
Multiple Choice ◽  
Gm Crops ◽  
Multiple Choice Questions ◽  
Relevant Difference ◽  
Gm Plants ◽  
Gender Education ◽  
The Impact ◽  
Traditional Crops

In this account we report a study that surveyed and quantified the opinion on the acceptability of genetically modified (GM) crops by farmers working in Szabolcs-Szatmár-Bereg County located in North Easter Hungary. Authors answered the question whether there is a difference in perception and reasoning of the county’s agricultural workers regarding GM crops. We evaluated the impact of age, gender, education, and agricultural education of responders on rating GM plants to be more dangerous than traditional crops. Is there a relevant difference when responders are administered multiple choice questions, rather than single choice questions? Can we change farmers’ position on the GM technology by using multiple choice questions?

Nutrient inputs versus piscivore biomass as the primary driver of reservoir food webs

2013 ◽  
Vol 70 (3) ◽  
pp. 367-380 ◽  
Author(s):  
Bryan T. Kinter ◽  
Stuart A. Ludsin
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Striped Bass ◽  
Gizzard Shad ◽  
Hybrid Striped Bass ◽  
Top Predator ◽  
Nutrient Inputs ◽  
Food Web Structure ◽  
Introduced Predators ◽  
The Impact

We used an ecosystem-based modeling approach, Ecopath with Ecosim, to explore the relative importance of a top-down biotic management lever (top predator introduction) versus a bottom-up abiotic management lever (alteration of nutrient inputs) in regulating biomass in reservoir food webs. To do so, we modeled three Ohio reservoirs that varied in ecosystem productivity. For each, we simulated five hybrid striped bass (Morone chrysops × Morone saxatilis) (introduced top predator) biomass levels at three nutrient input levels (n = 15 simulations per reservoir). Nutrient inputs influenced the food web more than introduced predators within each reservoir. Further, across all three reservoirs, the impact of stocked hybrid striped bass on the equilibrium biomass of phytoplankton, prey fish (gizzard shad, Dorosoma cepedianum), and native top predators (e.g., largemouth bass, Micropterus salmoides) was <3%, <14%, and <20%, respectively, of the maximum impact of changes in nutrient inputs on these components. Thus, in mesotrophic to hypereutrophic reservoirs that are dominated by omnivorous gizzard shad, manipulating allochthonous inputs of nutrients offers agencies a more powerful means to regulate food web structure than manipulation of top predator biomass.

scholarly journals Predicting the effects of temperature on food web connectance

2010 ◽  
Vol 365 (1549) ◽  
pp. 2081-2091 ◽  
Author(s):  
Owen L. Petchey ◽  
Ulrich Brose ◽  
Björn C. Rall
Keyword(s):  
Community Structure ◽  
Food Web ◽  
Food Webs ◽  
Temperature Effects ◽  
Diet Breadth ◽  
The Body ◽  
Large Temperature ◽  
Temperature Sensitive ◽  
Food Web Structure ◽  
Resource Item

Few models concern how environmental variables such as temperature affect community structure. Here, we develop a model of how temperature affects food web connectance, a powerful driver of population dynamics and community structure. We use the Arrhenius equation to add temperature dependence of foraging traits to an existing model of food web structure. The model predicts potentially large temperature effects on connectance. Temperature-sensitive food webs exhibit slopes of up to 0.01 units of connectance per 1°C change in temperature. This corresponds to changes in diet breadth of one resource item per 2°C (assuming a food web containing 50 species). Less sensitive food webs exhibit slopes down to 0.0005, which corresponds to about one resource item per 40°C. Relative sizes of the activation energies of attack rate and handling time determine whether warming increases or decreases connectance. Differences in temperature sensitivity are explained by differences between empirical food webs in the body size distributions of organisms. We conclude that models of temperature effects on community structure and dynamics urgently require considerable development, and also more and better empirical data to parameterize and test them.

Current state of genetically modified plant impact on target and non-target fungi

2010 ◽  
Vol 18 (NA) ◽  
pp. 441-475 ◽  
Author(s):  
F. O.P. Stefani ◽  
R. C. Hamelin
Keyword(s):  
Fungal Pathogens ◽  
Genetically Modified ◽  
Gm Crops ◽  
Current State ◽  
Gm Plants ◽  
Gm Trees ◽  
Fungal Populations ◽  
Field Deployment ◽  
Abundance And Diversity ◽  
The Impact

For two decades, genetic engineering has made it possible to develop crops and trees designed for yield improvement and simplified culture management. This, combined with field deployment of monocultures over large areas, can result in environmental stress and unwanted potential side effects. The commercial production of genetically modified (GM) crops and the recent development of GM trees raise concerns about their potential impact on the environment, in general, and on the biodiversity of non-target organisms, in particular. Fungi are spread worldwide and play key roles in ecosystems. They have been closely associated with plants since they emerged from the oceans. This review critically examines research monitoring the potential effects of GM crops and GM trees on target and non-target fungi. Parsing public databases for peer-reviewed publications about GM plant impacts on fungi yielded 149 studies, a relatively modest number considering the diversity of crops and ecosystems studied. Analysis of these publications showed that the effects of GM plants expressing herbicide and insect tolerance on fungi are understudied while they dominate the GM area worldwide. Experiments monitoring the impact of GM crops and GM trees with enhanced antifungal activity towards target fungi showed, for the most part, significant decreases in disease severity caused by fungal pathogens. Significant changes, expressed as an increase or decrease in fungal development, abundance, and diversity of non-target fungi, were observed in 18 out of 60 studies and all of them involved GM plants expressing traits that were unexpected to affect fungi. The remaining 42 studies did not identify a significant impact on fungal populations. Therefore, in spite of the fact that GM plants have been commercialized since 1996, no clear generalized trend can be identified and it appears that a case-by-case approach is the safest.

scholarly journals Food web structure and biocontrol in a four-trophic level system across a landscape complexity gradient

2011 ◽  
Vol 278 (1720) ◽  
pp. 2946-2953 ◽  
Author(s):  
Vesna Gagic ◽  
Teja Tscharntke ◽  
Carsten F. Dormann ◽  
Bernd Gruber ◽  
Anne Wilstermann ◽  
...  
Keyword(s):  
Biological Control ◽  
Food Web ◽  
Food Webs ◽  
Agricultural Landscapes ◽  
Cereal Aphids ◽  
Food Web Structure ◽  
Aphid Parasitoid ◽  
Landscape Complexity ◽  
Food Web Complexity ◽  
Complex Landscapes

Decline in landscape complexity owing to agricultural intensification may affect biodiversity, food web complexity and associated ecological processes such as biological control, but such relationships are poorly understood. Here, we analysed food webs of cereal aphids, their primary parasitoids and hyperparasitoids in 18 agricultural landscapes differing in structural complexity (42–93% arable land). Despite little variation in the richness of each trophic group, we found considerable changes in trophic link properties across the landscape complexity gradient. Unexpectedly, aphid–parasitoid food webs exhibited a lower complexity (lower linkage density, interaction diversity and generality) in structurally complex landscapes, which was related to the dominance of one aphid species in complex landscapes. Nevertheless, primary parasitism, as well as hyperparasitism, was higher in complex landscapes, with primary parasitism reaching levels for potentially successful biological control. In conclusion, landscape complexity appeared to foster higher parasitism rates, but simpler food webs, thereby casting doubt on the general importance of food web complexity for ecosystem functioning.

USING FOOD WEBS TO UNDERSTAND THE EFFECTS OF BIOTIC INVASION ON LATE ORDOVICIAN MARINE COMMUNITY STRUCTURE

2017 ◽  
Author(s):  
Hannah L. Kempf ◽  
◽  
Ian O. Castro ◽  
Carrie L. Tyler ◽  
Ashley A. Dineen ◽  
...  
Keyword(s):  
Community Structure ◽  
Food Webs ◽  
Late Ordovician ◽  
Biotic Invasion ◽  
Marine Community

scholarly journals Response of ocean phytoplankton community structure to climate change over the 21st century: partitioning the effects of nutrients, temperature and light

2010 ◽  
Vol 7 (12) ◽  
pp. 3941-3959 ◽  
Author(s):  
I. Marinov ◽  
S. C. Doney ◽  
I. D. Lima
Keyword(s):  
Climate Change ◽  
Community Structure ◽  
Sea Ice ◽  
Phytoplankton Biomass ◽  
Phytoplankton Community ◽  
Vertical Mixing ◽  
Phytoplankton Community Structure ◽  
Marginal Sea ◽  
Small Phytoplankton ◽  
The Impact

Abstract. The response of ocean phytoplankton community structure to climate change depends, among other factors, upon species competition for nutrients and light, as well as the increase in surface ocean temperature. We propose an analytical framework linking changes in nutrients, temperature and light with changes in phytoplankton growth rates, and we assess our theoretical considerations against model projections (1980–2100) from a global Earth System model. Our proposed "critical nutrient hypothesis" stipulates the existence of a critical nutrient threshold below (above) which a nutrient change will affect small phytoplankton biomass more (less) than diatom biomass, i.e. the phytoplankton with lower half-saturation coefficient K are influenced more strongly in low nutrient environments. This nutrient threshold broadly corresponds to 45° S and 45° N, poleward of which high vertical mixing and inefficient biology maintain higher surface nutrient concentrations and equatorward of which reduced vertical mixing and more efficient biology maintain lower surface nutrients. In the 45° S–45° N low nutrient region, decreases in limiting nutrients – associated with increased stratification under climate change – are predicted analytically to decrease more strongly the specific growth of small phytoplankton than the growth of diatoms. In high latitudes, the impact of nutrient decrease on phytoplankton biomass is more significant for diatoms than small phytoplankton, and contributes to diatom declines in the northern marginal sea ice and subpolar biomes. In the context of our model, climate driven increases in surface temperature and changes in light are predicted to have a stronger impact on small phytoplankton than on diatom biomass in all ocean domains. Our analytical predictions explain reasonably well the shifts in community structure under a modeled climate-warming scenario. Climate driven changes in nutrients, temperature and light have regionally varying and sometimes counterbalancing impacts on phytoplankton biomass and structure, with nutrients and temperature dominant in the 45° S–45° N band and light-temperature effects dominant in the marginal sea-ice and subpolar regions. As predicted, decreases in nutrients inside the 45° S–45° N "critical nutrient" band result in diatom biomass decreasing more than small phytoplankton biomass. Further stratification from global warming could result in geographical shifts in the "critical nutrient" threshold and additional changes in ecology.

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