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Results 201 - 250 of 1047
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Seymour J R - - 2009
Exploitation of microscale (microm-mm) resource patches by planktonic microorganisms may influence oceanic trophodynamics and nutrient cycling. However, examinations of microbial behavior within patchy microhabitats have been precluded by methodological limitations. We developed a microfluidic device to generate microscale resource patches at environmentally realistic spatiotemporal scales, and we examined the exploitation ...
Thelaus Johanna - - 2009
The natural reservoir of Francisella tularensis, the causative agent of tularaemia, is yet to be identified. We investigated the possibility that Francisella persists in natural aquatic ecosystems between outbreaks. It was hypothesized that nutrient-rich environments, with strong protozoan predation, favour the occurrence of the tularaemia bacterium. To investigate the differences ...
Lecomte Nicolas - - 2009
To what extent top predators - carnivores at the top of food chains - drive or just respond to ecosystem dynamics is a central, but partially unresolved, question in ecology. In this report, we highlight how different research approaches employed in aquatic and terrestrial ecology may have a bearing on ...
Vermaat Jan E - - 2009
The covariance among a range of 20 network structural properties of food webs plus net primary productivity was assessed for 14 published food webs using principal components analysis. Three primary components explained 84% of the variability in the data sets, suggesting substantial covariance among the properties employed in the literature. ...
Kr??ger Bj??rn - - 2009
BACKGROUND: During the Ordovician the global diversity increased dramatically at family, genus and species levels. Partially the diversification is explained by an increased nutrient, and phytoplankton availability in the open water. Cephalopods are among the top predators of today's open oceans. Their Ordovician occurrences, diversity evolution and abundance pattern potentially ...
Sirot Etienne - - 2009
Prey living in groups often partly rely on companions to detect predators. Accordingly, individuals having vigilant neighbors could decrease their own vigilance, engendering a certain level of vigilance coordination in the group. However, when a predator attacks, individuals that spot it react quicker than individuals that follow them and have ...
Brook Barry W - - 2009
Climate change impacts are becoming increasingly evident as 1 degree C warming above pre-industrial temperatures is approached. One of the signature biological effects is a shift towards earlier-timed reproduction. If individual species lack sufficient adaptive plasticity to alter phenology, they will have reduced fitness in a hotter world. Yet, a ...
Spivak Amanda C - - 2009
Food web composition and resource levels can influence ecosystem properties such as productivity and elemental cycles. In particular, herbivores occupy a central place in food webs as the species richness and composition of this trophic level may simultaneously influence the transmission of resource and predator effects to higher and lower ...
Byers James E - - 2009
Growing evidence indicates parasite inclusion in food-web analyses is a logical default. Comparisons of food webs including and excluding host-parasite interactions demonstrate the influence of parasites on community dynamics. Although including parasites is undoubtedly informative, the necessary level of detail exists for only a handful of systems. In a recent ...
Casini Michele - - 2009
Fisheries can have a large impact on marine ecosystems, because the effects of removing large predatory fish may cascade down the food web. The implications of these cascading processes on system functioning and resilience remain a source of intense scientific debate. By using field data covering a 30-year period, we ...
Boyd Eric S - - 2009
Microbial mats are a visible and abundant life form inhabiting the extreme environments in Yellowstone National Park (YNP), WY, USA. Little is known of their role in food webs that exist in the Park's geothermal habitats. Eukaryotic green algae associated with a phototrophic green/purple Zygogonium microbial mat community that inhabits ...
McLachlan Athol J - - 2009
Detritus (dead organic matter), largely of terrestrial origin, is superabundant in inland waters but because of its indigestible nature, would appear to be a poor food source for animals. Yet this unpromising material is widely used as food and indeed can be viewed as a defining characteristic of the freshwater ...
Edeline Eric - - 2008
Selection can alter predator-prey interactions. However, whether and how complex food-webs respond to selection remain largely unknown. We show in the field that antagonistic selection from predators and pathogens on prey body-size can be a primary driver of food-web functioning. In Windermere, U.K., pike (Esox lucius, the predator) selected against ...
Prince Emily K - - 2008
Biotic interactions in the plankton can be both complex and dynamic. Competition among phytoplankton is often chemically mediated, but no studies have considered whether allelopathic compounds are modified by biotic interactions. Here, we show that compounds exuded during Karenia brevis blooms were allelopathic to the cosmopolitan diatom Skeletonema costatum, but ...
Chin Karen - - 2008
As the earth faces a warming climate, the rock record reminds us that comparable climatic scenarios have occurred before. In the Late Cretaceous, Arctic marine organisms were not subject to frigid temperatures but still contended with seasonal extremes in photoperiod. Here, we describe an unusual fossil assemblage from Devon Island, ...
Srivastava D S - - 2008
Ecologists have hypothesized that the exponent of species-area power functions (z value) should increase with trophic level. The main explanation for this pattern has been that specialist predators require prior colonization of a patch by their prey, resulting in a compounding of the effects of area up trophic levels. We ...
Gaten Edward - - 2008
Antarctic krill (Euphausia superba) is a keystone species in the southern ocean ecosystem where it is the main consumer of phytoplankton and constitutes the main food item of many higher predators. Both food and predators are most abundant at the surface, thus krill hide in the depth of the ocean ...
Pringle Robert M - - 2008
Understanding food-web dynamics requires knowing whether species assemblages are compartmentalized into distinct energy channels, and, if so, how these channels are structured in space. We used isotopic analyses to reconstruct the food web of a Kenyan wooded grassland. Insect prey were relatively specialized consumers of either C3 (trees and shrubs) ...
Walters Annika W - - 2008
Streams experience frequent natural disturbance and are undergoing considerable anthropogenic disturbance due to dam construction and water diversion. Disturbance is known to impact community structure, but its effect on food chain length is still a matter of considerable debate. Theoretical models show that longer food chains are less resilient to ...
Hall Spencer R - - 2009
Epidemiologists increasingly realize that species interactions (e.g. selective predation) can determine when epidemics start and end. We hypothesize here that resource quality can also strongly influence disease dynamics: epidemics can be inhibited when resource quality for hosts is too poor and too good. In three lakes, resource quality for the ...
Sabat Pablo - - 2009
The urine field osmolality in Zonotrichia capensis along a latitudinal gradient in rainfall and temperature in Chile was examined. We also investigated latitudinal variation in the renal traits that mediate how these birds cope with dehydration. We used the delta15N of this species' tissue to investigate whether the reliance on ...
Chen Celia C Department of Biological Sciences, HB 6044, Dartmouth College, Hanover, NH 03755, USA. - - 2008
The spatial variation of MeHg production, bioaccumulation, and biomagnification in marine food webs is poorly characterized but critical to understanding the links between sources and higher trophic levels, such as fish that are ultimately vectors of human and wildlife exposure. This article discusses both large and local scale processes controlling ...
Brose Ulrich - - 2008
Herbivorous top-down forces and bottom-up competition for nutrients determine the coexistence and relative biomass patterns of producer species. Combining models of predator-prey and producer-nutrient interactions with a structural model of complex food webs, I investigated these two aspects in a dynamic food-web model. While competitive exclusion leads to persistence of ...
O'Gorman Eoin J - - 2008
We manipulated the diversity of top predators in a three trophic level marine food web. The food web included four top benthic marine fish predators (black goby, rock goby, sea scorpion and shore rockling), an intermediate trophic level of small fish, and a lower trophic level of benthic invertebrates. We ...
Kullmann Harald - - 2008
Group living has evolved as an adaptation to predation in many animal species. In a multitude of vertebrates, the tendency to aggregate varies with the risk of predation, but experimental evidence for this is less well known in invertebrates. Here, we examine the tendency to aggregate in the freshwater amphipod ...
Murai Ryota - - 2008
The measurement of organotins in the various biotas of coastal food webs with stable nitrogen isotope ratios (delta(15)N), which increase 3.4 per thousand per trophic level, can provide a biomagnification profile of organotins through food web. In this study, various biological samples were collected from three localities in Western Japan ...
Kondoh Michio - - 2008
Understanding what maintains species and perpetuates their coexistence in a network of feeding relationships (the food web) is of great importance for biodiversity conservation. A food web can be viewed as consisting of a number of simple subunits called trophic modules. Intraguild predation (IGP), in which a prey and its ...
Gérard Claudia - - 2009
Community structure and microcystin accumulation of freshwater molluscs were studied before and after cyanobacterial proliferations, in order to assess the impact of toxic blooms on molluscs and the risk of microcystin transfer in food web. Observed decrease in mollusc abundance and changes in species richness in highly contaminated waters were ...
Gracey Andrew Y - - 2008
The physiological strategies that enable organisms to thrive in habitats where environmental factors vary dramatically on a daily basis are poorly understood. One of the most variable and unpredictable habitats on earth is the marine rocky intertidal zone located at the boundary between the terrestrial and marine environments. Mussels dominate ...
Desneux N - - 2008
Generalist insect predators can significantly impact the dynamics of pest populations; and, using alternative prey, they can rapidly establish in disturbed agroecosystems. However, indirect interactions between prey can occur, leading to either increased or decreased predation on focal prey. The present paper demonstrates how alternative prey can disrupt predation by ...
Ng Carla A - - 2008
The global spread of invasive species is changing the structure of aquatic food webs worldwide. The North American Great Lakes have proved particularly vulnerable to this threat. In nearshore areas, invasive benthic species such as dreissenid mussels and round gobies (Neogobius melanostomus) have gained dominance in recent years. Such species ...
Nauwelaerts Sandra - - 2008
Although the motor control of feeding is presumed to be generally conserved, some fishes are capable of modulating the feeding behaviour in response to prey type and or prey size. This led to the 'feeding modulation hypothesis', which states that rapid suction strikes are pre-programmed stereotyped events that proceed to ...
Forshay Kenneth J - - 2008
When parasitic infections are severe or highly prevalent among prey, a significant component of the predator's diet may consist of parasitized hosts. However, despite the ubiquity of parasites in most food webs, comparisons of the nutritional quality of prey as a function of infection status are largely absent. We measured ...
Trussell Geoffrey C - - 2008
It is well established that predators can scare as well as consume their prey. In many systems, the fear of being eaten causes trait-mediated cascades whose strength can rival or exceed that of more widely recognized density-mediated cascades transmitted by predators that consume their prey. Despite this progress it is ...
Hewitt, Chad L
Marine invasions have been identified in virtually all regions of the world, yet relatively few introductions have been detected in the Tropics. This has been attributed at least in part to an increase in intrinsic native community resistance at lower latitudes resulting from strongly interacting food webs in high(er) diversity ...
Smith, David G
On O'ahu, Wedge-tailed Shearwaters (Puffinus pacifieus) and other seabirds nest primarily on small offshore islets, but fossil evidence shows that many seabirds formerly bred on O'ahu itself. Predation by introduced mammals is suspected to be the primary factor preventing shearwaters and other seabirds from reestablishing large nesting colonies on O'ahu. ...
Whitcraft Christine R - - 2008
Plant invasions of coastal wetlands are rapidly changing the structure and function of these systems globally. Alteration of litter dynamics represents one of the fundamental impacts of an invasive plant on salt marsh ecosystems. Tamarisk species (Tamarix spp.), which extensively invade terrestrial and riparian habitats, have been demonstrated to enter ...
Kojadinovic, Jessica
Stable nitrogen and carbon isotopes were used to investigate trophic ecology in tropical marine bird and fish communities from Reunion Island, western Indian Ocean. Firstly, isotope signatures in the liver of Barau's petrels Pterodroma baraui, Audubon's shearwaters Puffinus lherminieri bailloni, and white-tailed tropicbirds Phaethon lepturus were used to compare their ...
Roessink Ivo - - 2008
Effects of nutrients and toxicants in aquatic ecosystems may interact in several ways. Here, we (a) present an overview of reported mechanisms that may play a role in these interactions, and (b) compare these reported mechanisms against the results of a suite of experiments performed with organic micro-pollutants in outdoor ...
Both Christiaan - - 2009
1. Climate change has been shown to affect the phenology of many organisms, but interestingly these shifts are often unequal across trophic levels, causing a mismatch between the phenology of organisms and their food. 2. We consider two alternative hypotheses: consumers are constrained to adjust sufficiently to the lower trophic ...
Gliwicz Z Maciej - - 2008
Using an individual-based age-structured population model (a combination of O'Brien's apparent-prey-size approach, Eggers's reactive-field-volume model, and Holling's disk equation), we could predict that (1) a Daphnia population could be kept at low density by fish predation irrespective of food level, with greater recruitment at higher food being instantly compensated for ...
Tudorache Christian - - 2008
In fish, fast starts are brief, sudden accelerations during predator-prey encounters. They serve for escape and predation and are therefore ecologically important movements. Fast starts are generated by glycolytic muscle performance and are influenced by many internal and external factors. It is known that ammonia pollution has a major effect ...
Hilker Frank M - - 2008
Parasites are an integral part of virtually all food webs and species communities. Here we consider the invasion of a resident predator-prey system by an infectious disease with frequency-dependent transmission spreading within the predator population. We derive biologically plausible and insightful quantities (demographic and epizootiological reproduction numbers) that allow us ...
Preziosi Damian V - - 2008
Food web analysis can be a critical component of ecological risk assessment, yet it has received relatively little attention among risk assessors. Food web data are currently used in modeling bioaccumulation of toxic chemicals and, to a limited extent, in the determination of the ecological significance of risks. Achieving more ...
Corsolini Simonetta - - 2009
A critical review of the levels and patterns of industrial contaminants in biota from Antarctica and the Southern Ocean revealed that concentrations are low with respect to other regions of the world, although in some specimens/species (e.g. leopard seal, some invertebrates) they are occasionally high and comparable to those found ...
Casini Michele - - 2008
Anthropogenic disturbances intertwined with climatic changes can have a large impact on the upper trophic levels of marine ecosystems, which may cascade down the food web. So far it has been difficult to demonstrate multi-level trophic cascades in pelagic marine environments. Using field data collected during a 33-year period, we ...
Novak Mark - - 2008
Efforts to estimate the strength of species interactions in species-rich, reticulate food webs have been hampered by the multitude of direct and indirect interactions such systems exhibit and have been limited by an assumption that pairwise interactions display linear functional forms. Here we present a new method for directly measuring, ...
Takada Mayura - - 2008
We examined web-building spider species richness and abundance in forests across a deer density gradient to determine the effects of sika deer browsing on spiders among habitats and feeding guilds. Deer decreased the abundance of web-building spiders in understory vegetation but increased their abundance in the litter layer. Deer seemed ...
White T C R - - 2008
More and more studies are demonstrating that populations of animals - from herbivores to top predators, vertebrates and invertebrates - are limited by their food, and that the availability of this food is dictated by the weather. Satellite monitoring is revealing how cyclic and quasi-cyclic climatic patterns, like the El ...
Stallings Christopher D - - 2008
The more ecologists examine the role of trait-mediated indirect interactions (TMIIs), especially in regulating predator-prey interactions, the more we recognize their fundamental role in structuring food webs. However, most empirical evidence for TMIIs comes from studies that are either conducted in laboratory or mesocosm venues or are restricted to simple ...
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