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Results 251 - 300 of 1057
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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 ...
Rooney Neil - - 2008
Ecologists have long searched for structures and processes that impart stability in nature. In particular, food web ecology has held promise in tackling this issue. Empirical patterns in food webs have consistently shown that the distributions of species and interactions in nature are more likely to be stable than randomly ...
Lancaster Jill - - 2008
In classical theory, species are assumed to achieve dominance through competitive exclusion, but if food resources are limiting, cross-habitat trophic subsidies could also underpin dominance. The impact of dominant species on community dynamics may depend on the energy base of population size. We report on an unusual, spatially subsidized population ...
van der Stap Irene - - 2008
Ecologists have long debated the role of predation in mediating the coexistence of prey species. Theory has mainly taken a bitrophic perspective that excludes the effects of inducible defenses at different trophic levels. However, inducible defenses could either limit or enhance the effects of predation on coexistence, by means of ...
Friman Ville-Petri - - 2008
Productivity is predicted to drive the ecological and evolutionary dynamics of predator-prey interaction through changes in resource allocation between different traits. Here we report results of an evolutionary experiment where prey bacteria Serratia marcescens was exposed to predatory protozoa Tetrahymena thermophila in low- and high-resource environments for approximately 2400 prey ...
Lennon Jay T - - 2008
Predation and parasitism often regulate population dynamics, community interactions, and ecosystem functioning. The strength of these top-down pressures is variable, however, and may be influenced by both ecological and evolutionary processes. We conducted a chemostat experiment to assess the direct and indirect effects of viruses on a marine microbial food ...
Kido, Michael H
Diet of rainbow trout, Oncorhynchus mykiss (Walbaum), introduced by the State of Hawai'i into tropical headwater streams of the Waimea River in the Koke'e area of the Hawaiian island of Kaua'i, was examined in this study through gut content analysis. In Wai'alae Stream, rainbow trout were found to be opportunistic ...
Dumas Julie - - 2008
Although nickel and thallium are present at potentially harmful concentrations in some lakes, there is little information on their bioaccumulation and transfer up aquatic food webs. To measure the propensity of animals for accumulating and transferring these contaminants along food chains, we exposed two common types of invertebrates, an insect ...
Trebatická Lenka - - 2008
Indirect interaction between two competing species via a shared predator may be an important determinant of population and community dynamics. We studied the effect of predation risk imposed by the least weasel Mustela nivalis nivalis on space use, foraging and activity of two competing vole species, the grey-sided vole Myodes ...
Fey Karen - - 2008
Ecosystems of three trophic levels may be bottom-up (by food-plant availability) and/or top-down (by predators) limited. Top-down control might be of greater consequence when the predation impact comes from an alien predator. We conducted a replicated two-factor experiment with field voles (Microtus agrestis) during 2004-2005 on small islands of the ...
Nilsson Erika - - 2008
It is important to understand the role that different predators can have to be able to predict how changes in the predator assemblage may affect the prey community and ecosystem attributes. We tested the effects of different stream predators on macroinvertebrates and ecosystem attributes, in terms of benthic algal biomass ...
Navarrete Sergio A - - 2008
Investigating how food supply regulates the behavior and population structure of predators remains a central focus of population and community ecology. These responses will determine the strength of bottom-up processes through the food web, which can potentially lead to coupled top-down regulation of local communities. However, characterizing the bottom-up effects ...
Smith Craig R - - 2008
The abyssal seafloor covers more than 50% of the Earth and is postulated to be both a reservoir of biodiversity and a source of important ecosystem services. We show that ecosystem structure and function in the abyss are strongly modulated by the quantity and quality of detrital food material sinking ...
Asante Kwadwo Ansong - - 2008
Trace elements (22) and stable isotope ratios (delta15N and delta13C) were analyzed in marine organisms from shallow (SW) and deep-water (DW) of the East China Sea to understand biomagnification and prey source of trace elements. In the benthic marine organisms from DW, delta15N values were negatively correlated with Ba, Cu, ...
Faria Lucas Del Bianco Ldel - - 2009
Prey preference of a predator is commonly used in models to analyze the timely issue of the relation among food web structure, diversity and stability. Given the variety of these terms in ecological literature, this work shows that domains of stability and species coexistence in food webs can be significantly ...
Bretagnolle V - - 2008
1. Understanding how density-dependent and independent processes influence demographic parameters, and hence regulate population size, is fundamental within population ecology. We investigated density dependence in growth rate and fecundity in a recovering population of a semicolonial raptor, the osprey Pandion haliaetus [Linnaeus, 1758], using 31 years of count and demographic ...
Beasley Jeannette M - - 2009
To develop and evaluate a pictorial, web-based version of the NCI diet history questionnaire (Web-PDHQ). The Web-PDHQ and paper version of the DHQ (Paper-DHQ) were administered 4 weeks apart with 218 participants randomised to order. Dietary data from the Web-PDHQ and Paper-DHQ were validated using a randomly selected 4 d ...
Brose U - - 2008
1. In natural communities, populations are linked by feeding interactions that make up complex food webs. The stability of these complex networks is critically dependent on the distribution of energy fluxes across these feeding links. 2. In laboratory experiments with predatory beetles and spiders, we studied the allometric scaling (body-mass ...
Ruzicka, James J.
Previously published in California Cooperative Oceanic Fisheries Investigations Progress Report, 2007, Vol.48; access courtesy of publisher and authors.
Ho Chuan-Kai - - 2008
Although omnivory is common in nature, its impact on trophic interactions is variable. Predicting the food web consequences of omnivory is complicated because omnivores can simultaneously produce conflicting direct and indirect effects on the same species or trophic level. We conducted field and laboratory experiments testing the top-down impacts of ...
Greenwood Michelle J - - 2008
Landscape-driven processes impact the magnitude and direction of cross-ecosystem resource subsidies, but they may also control consumers' numerical and functional responses by altering habitat availability. We investigated effects of the interaction between habitat availability and subsidy level on populations of a riparian fishing spider, Dolomedes aquaticus, using a flood disturbance ...
Branson David H - - 2008
The complex interplay between grasshoppers, weather conditions, and plants that cause fluctuations in grasshopper populations remains poorly understood, and little is known about the ecological processes that generate grasshopper outbreaks. Grasshopper populations respond to interacting extrinsic and intrinsic factors, with yearly and decadal weather patterns and the timing of precipitation ...
Jennings Simon - - 2008
Interacting human and environmental pressures influence the structure and dynamics of marine food webs. To describe and predict the effects of these pressures, theoretical advances need to be supported by a capacity to validate the underlying models and assumptions. Here, we review recent applications of nitrogen stable isotope analysis in ...
Geisz Heidi N - - 2008
Persistent organic pollutants reach polar regions by long-range atmospheric transport and biomagnify through the food web accumulating in higher trophic level predators. We analyzed Adélie penguin (Pygoscelis adeliae) samples collected from 2004 to 2006 to evaluate current levels of sigmaDDT (p,p'-DDT + p,p'-DDE) in these birds, which are confined to ...
Lafferty Kevin D - - 2008
Parasitism is the most common consumer strategy among organisms, yet only recently has there been a call for the inclusion of infectious disease agents in food webs. The value of this effort hinges on whether parasites affect food-web properties. Increasing evidence suggests that parasites have the potential to uniquely alter ...
Holbrook R David - - 2008
The unique chemical and physical properties of engineered nanomaterials that make them attractive for numerous applications also contribute to their unexpected behaviour in the environment and biological systems. The potential environmental risks, including their impact on aquatic organisms, have been a central argument for regulating the growth of the nanotechnology ...
Englund G - - 2008
1. The predatory isopod Saduria entomon (L.) and its amphipod prey Monoporeia affinis (Lindström) are key components of the food web in the northern Baltic Sea, together representing 80-90% of the macrobenthic biomass. We use 20 years of stomach content data for Saduria to investigate how diet dynamics affect the ...
Miller Noam Y NY Department of Psychology, University of Toronto at Mississauga, 3359 Mississauga Road North, Mississauga, Toronto, Ontario, L5L 1C6 Canada. - - 2008
In many species, group cohesion may be the result of a compromise between opposing forces (e.g. predator avoidance and competition for food). However, little empirical data exists on the dynamics of group cohesion. We present moment-to-moment positional data on zebrafish shoals and analyze temporal changes in inter-individual distances. We demonstrate ...
Tomy Gregg T - - 2008
The extent of trophic transfer of the three diastereoisomers of hexabromocyclododecane (HBCD) and seven brominated diphenyl ether (BDE) congeners was examined in components of an Arctic marine food web from eastern Canada. Alpha and gamma-HBCD diastereoisomers were detected in all species and total (sigma) HBCD concentrations ranged from 0.6 +/- ...
Bhavsar Satyendra P - - 2008
Biotransformation half-lives (HL) and gut absorption efficiencies (GAE) of PBDE congeners in fish are poorly known and challenging to quantify experimentally. These values are needed in order to accurately assess their food web dynamics, and in turn, for policy development We recently developed a multichemical aquatic food web model, which ...
Peterson Celeste N - - 2008
The community of organisms inhabiting the water-filled leaves of the carnivorous pitcher-plant Sarracenia purpurea includes arthropods, protozoa and bacteria, and serves as a model system for studies of food web dynamics. Despite the wealth of data collected by ecologists and zoologists on this food web, very little is known about ...
Bersier, Louis-Félix
Understanding the processes underlying food-web structure and organization remains one of the major tasks of ecology. While first attempts were mostly based on niche theory, with body size of species imposing a hierarchical structure for consumer species, it has been recently suggested that phylogenetic constraints may be more fundamental to ...
Blanchet S - - 2008
Using semi-natural stream channels, we estimated the effects of competition and predation exerted by juvenile and adult exotic rainbow trout (Oncorhynchus mykiss) on the diel activity pattern of juvenile native Atlantic salmon (Salmo salar), a secondary consumer. We also evaluated the direct and indirect effects of competition, predation and abiotic ...
Kröpelin S - - 2008
Desiccation of the Sahara since the middle Holocene has eradicated all but a few natural archives recording its transition from a "green Sahara" to the present hyperarid desert. Our continuous 6000-year paleoenvironmental reconstruction from northern Chad shows progressive drying of the regional terrestrial ecosystem in response to weakening insolation forcing ...
Laurila Anssi - - 2008
Antipredator defenses are expected to decrease toward higher latitudes because predation rates are predicted to decrease with latitude. However, latitudinal variation in predator avoidance and defense mechanisms has seldom been studied. We studied tadpole antipredator defenses in seven Rana temporaria populations collected along a 1500-km latitudinal gradient across Sweden, along ...
Tyack Peter - - 2008
Sperm and beaked whales dive to feed on squid and deepwater fish. We have attached sound-and-orientation recording tags to study how these whales use echolocation to forage at depth. Tagged whales are usually silent when starting a dive, but start producing echolocation clicks at a few hundred meters depth, shallower ...
Rich C Nelson - - 2008
Little is known about the effects of different prey species on lizard growth. We conducted a 6-week study to determine the relative effects of prey species on growth parameters of hatchling western fence lizards, Sceloporus occidentalis. Lizards were fed house cricket nymphs, Acheta domesticus, or mealworm larvae, Tenebrio molitor. The ...
Ross Tetjana - - 2008
Models and laboratory experiments show that zooplankton may locate food more easily in turbulent waters, but whether plankton seek or avoid turbulence in the ocean is an open question. It is difficult to measure turbulence and plankton simultaneously and with the necessary spatial resolution using traditional methods (nets and airfoil ...
Doi Hideyuki - - 2008
Subsidy between ecosystems has been considered in many natural ecosystems, and should alter food webs and communities in human-impacted ones. We estimated how drifting plankton from a reservoir contribute to downstream food webs and showed that they alter community structures over a 10-km reach below the dam. To estimate the ...
Thorne Richard E - - 2008
High-frequency acoustic surveys over the past 15 years show that the trophic structure in Prince William Sound (PWS), Alaska, functions as a wasp-waist ecosystem. Three dominant biomasses in PWS are: (1) Pacific herring (2) walleye pollock and (3) the large-bodied copepods (Neocalanus spps.) that dominate the spring zooplankton assemblage. The ...
Marczak Laurie B - - 2008
Rapid growth in response to increased prey abundance may be induced by environmental variability associated with resource subsidies. Spiders living in riparian areas are subject to frequent, episodic bursts of aquatic prey (subsidies). These periods of high resource abundance may occur at different points in recipient consumers' development through variation ...
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