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Results 751 - 800 of 1050
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Danner Bradford J - - 2003
In response to increased exposure to predators when searching for food, many prey increase the frequency of antipredator behaviors, potentially reducing foraging rate and food intake. Such direct, nonlethal interactions between predators and prey resulting in reduced food intake can indirectly influence lifecycle development through effects on growth, developmental rate, ...
Southall E J - - 2003
Dermal denticles are unique tooth-like structures embedded in the skin of sharks and rays that protect them from predators and ectoparasites, reduce mechanical abrasion and possibly minimize swimming-induced drag. Here, we show that juvenile lesser spotted dogfish (Scyliorhinus canicula) also use this body armour to anchor food items near their ...
Noelle Beckman
Although the importance of omnivory in food webs has been established, the community niche of generalist arthropod predators such as praying mantids is usually assumed to be at most bitrophic, feeding on herbivores and other carnivores. As with most predators, mantids often are food limited in nature. Flowering plants in ...
Bergman Daniel A - - 2003
Agonistic behavior is a fundamental aspect of ecological theories on resource acquisition and sexual selection. Crustaceans are exemplary models for agonistic behavior within the laboratory, but agonistic behavior in natural habitats is often neglected. Laboratory studies do not achieve the same ecological realism as field studies. In an attempt to ...
Turner R Eugene - - 2003
Nutrient limitation of phytoplankton growth in aquatic systems is moving towards a higher incidence of P and Si limitation as a result of increased nitrogen loading, a N:P fertilizer use of 26:1 (molar basis), population growth, and relatively stable silicate loading. This result will likely alter phytoplankton community composition, and ...
Skirvin D J - - 2003
The effect of plant architecture, in terms of leaf hairiness, and prey spatial arrangement, on predation rate of eggs of the spider mite, Tetranychus urticae Koch, by the predatory mite Phytoseiulus persimilis Athias-Henriot was examined on cut stems of chrysanthemums. Three levels of leaf hairiness (trichome density) were obtained using ...
Jennings Simon - - 2003
Maximum food-chain length has been correlated with resource availability, ecosystem size, environmental stability and colonization history. Some of these correlations may result from environmental effects on predator-prey body size ratios. We investigate relationships between maximum food-chain length, predator-prey mass ratios, primary production and environmental stability in marine food webs with ...
Weis Judith S - - 2003
Studies of effects of the invasive brackish marsh plant Phragmites australis (common reed) on estuarine biota are reviewed. With few exceptions, most field studies indicate that these P. australis-dominated marshes have diverse and abundant benthic biota, and are utilized by nekton, comparable to Spartina alterniflora marshes. However, larval mummichogs, Fundulus ...
Nyström Per - - 2003
The influence of predatory fish on the structure of stream food webs may be altered by the presence of forest canopy cover, and consequent differences in allochthonous inputs and primary production. Eight sites containing introduced brown trout ( Salmo trutta) and eight sites that did not were sampled in the ...
von Elert Eric - - 2003
A key process in freshwater plankton food webs is the regulation of the efficiency of energy and material transfer. Cyanobacterial carbon (C) in particular is transferred very inefficiently to herbivorous zooplankton, which leads to a decoupling of primary and secondary production and the accumulation of cyanobacterial biomass, which is associated ...
Leah M. Laurich
Wetlands in the Prairie Pothole Region of North America are harsh environments for fish, and only two planktivorous species are common in these ecosystems: fathead minnows (Pimephales promelas) and brook sticklebacks (Culaea inconstans). Given their similarities, competition between these species may be high, especially for food resources. We assessed potential ...
Candaten Matteo - - 2003
We show in this paper that the chaotic regimes of many food chain models often enjoy a very peculiar property, known as peak-to-peak dynamics. This means that the maximum (peak) density of the populations of any trophic level can be easily forecasted provided the last two peaks of the same ...
Laurence John A - - 2003
Research aimed at understanding the response of plants to ozone has been conducted for over four decades but little of it has addressed intact natural systems. Even so, there is sufficient scientific information at this time to support air quality standards that will protect natural terrestrial ecosystems from ozone. What ...
Werner D - - 2003
Haematophagous female blackflies (Diptera: Simuliidae) are serious biting pests and obligate vectors of vertebrate pathogens, namely filarial Dirofilaria, Mansonella, Onchocerca and protozoal Leucocytozoon. Immature stages of Simuliidae inhabit lotic waterways, the sessile larvae filter-feeding and often forming a large proportion of the benthic biomass, usually aggregated in well-oxygenated sections of ...
Stafford Jennifer M - - 2003
Past evaluations of pesticide exposure have been conducted with substantial uncertainty regarding avian consumption of contaminated food items. One question is whether birds consume invertebrates that are killed by a chemical application and that may present an increasing chemical concentration as they desiccate. We addressed the research question in two ...
Garlaschelli Diego - - 2003
The structure of ecological communities is usually represented by food webs. In these webs, we describe species by means of vertices connected by links representing the predations. We can therefore study different webs by considering the shape (topology) of these networks. Comparing food webs by searching for regularities is of ...
Zanette Liana - - 2003
The behaviour literature is full of studies showing that animals in every taxon balance the probability of acquiring food with the risk of being preyed upon. While interactions between food and predators clearly operate at an individual scale, population-scale studies have tended to focus on only one factor at a ...
Reigada R - - 2003
Plankton play an important role in the ecology of the ocean and the climate because of their participation in the global carbon cycle at the base of the food chain. However, damaging plankton blooms can sometimes occur and are initially characterized by sudden transient increases in the phytoplankton population. They ...
A dynamic systems approach to evolutionary branching and its development in an artificial food web is presented. Predator-prey interaction among trophic species with two traits generates a variety of evolutionary branching patterns, depending on interaction strengths and mutation rates. Studying branching patterns in a phenotypic space reveals three branching patterns: ...
Xin-she Yang
A multispecies artificial ecosystem is formulated using cellular automata with species interactions and food chain hierarchy. The constructed finite state automaton can simulate the complexity and self-organized characteristics of the evolving multispecies living ecosystems.
Ruxton Graeme D - - 2003
Arguments on whether Tyrannosaurus rex was likely to have been an active predator or a scavenger have been based on evidence from jaw morphology and/or dentition. Here, we adopt an entirely novel approach, using energetic arguments to estimate the minimum productivity that would be required for an ecosystem to support ...
James G. March
Tropical stream food webs are thought to be based primarily on terrestrial resources (leaf litter) in small forested headwater streams and algal resources in larger, wider streams. In tropical island streams, the dominant consumers are often omnivorous freshwater shrimps that consume algae, leaf litter, insects, and other shrimps. We used ...
Godfrey C. Akani
The food habits of the snake Psammophis phillipsi were studied in the rain-forest region of southeastern Nigeria, where this is the most common snake species of the area. A total of 120 prey items were recorded from 327 specimens (73 juveniles; 55 gravid females); many gravid females contained prey. Lizards ...
Kondoh Michio - - 2003
Ecological theory suggests that complex food webs should not persist because of their inherent instability. "Real" ecosystems often support a large number of interacting species. A mathematical model shows that fluctuating short-term selection on trophic links, arising from a consumer's adaptive food choice, is a key to the long-term stability ...
den Dulk Paul - - 2003
The evolutionary justification by LeDoux (1996) for his dual-route model of fear processing was analyzed computationally by applying genetic algorithms to artificial neural networks. The evolution was simulated of a neural network controlling an agent that gathered food in an artificial world and that was occasionally menaced by a predator. ...
Nichols David S - - 2003
The investigation of prokaryotes in aquatic ecology is often limited to their role in nutrient cycling and the degradation of organic matter. While this aspect of the microbial loop is undoubtedly important, further aspects of bacterial roles in marine food webs exist which have not been fully considered in light ...
Mougeot F - - 2003
A central issue in ecology lies in identifying the importance of resources, natural enemies and behaviour in the regulation of animal populations. Much of the debate on this subject has focused on animals that show cyclic fluctuations in abundance. However, there is still disagreement about the role of extrinsic (food, ...
Luczkovich Joseph J - - 2003
We present a graph theoretic model of analysing food web structure called regular equivalence. Regular equivalence is a method for partitioning the species in a food web into "isotrophic classes" that play the same structural roles, even if they are not directly consuming the same prey or if they do ...
Gnanvossou Désiré - - 2003
Carnivorous arthropods exhibit complex intraspecific and interspecific behaviour among themselves when they share the same niche or habitat and food resources. They should simultaneously search for adequate food for themselves and their offspring and in the meantime avoid becoming food for other organisms. This behaviour is of great ecological interest ...
Cohen Joel E - - 2003
Measuring the numerical abundance and average body size of individuals of each species in an ecological community's food web reveals new patterns and illuminates old ones. This approach is illustrated using data from the pelagic community of a small lake: Tuesday Lake, Michigan, United States. Body mass varies almost 12 ...
Stapp Paul - - 2003
Inputs of energy and nutrients from one ecosystem may subsidize consumers in adjacent ones, with significant consequences for local communities and food webs. We used stable isotope and faecal pellet analysis to quantify use of ocean-derived resources by small mammals on islands in the Gulf of California, Mexico. Rodents were ...
Kopp, Michael
Trophic polyphenisms are examples of phenotypic plasticity where two or more morphs within a species exploit different food niches. In this context, induced traits that enhance feeding ability on certain prey types have been termed inducible offenses. Here, we describe a prey-induced continuous size polyphenism in the predatory ciliate Lembadion ...
Heldal Hilde Elise - - 2003
Knowledge and documentation of the levels of radioactive contamination in fish stocks important to Norwegian fisheries is of major importance to Norwegian consumers and fish export industry. In the present study, the bioaccumulation of caesium-137 ((137)Cs) has been investigated in marine food webs in the Barents and Norwegian Seas. The ...
Nomikou Maria - - 2003
Two phytoseiid species, Euseius scutalis (Athias-Henriot) and Typhlodromips swirskii (Athias-Henriot), are able to suppress whitefly populations on single plants and are candidate biological control agents for whiteflies such as Bemisia tabaci (Gennadius). These species can feed on pollen and insect-produced honeydew and these food sources are likely to be available ...
Onzo Alexis - - 2003
To determine the impact of an acarine predator guild on the abundance of a shared herbivorous prey and its principal exotic predator, a series of surveys were conducted in ca. 200 cassava fields in swamp and non-swamp areas in southwestern Benin, West Africa. For each field, the surveys provided data ...
Hoekstra P F - - 2003
Stable isotope values (13C, 15N) and concentrations of persistent organochlorine contaminants (OCs) were determined to evaluate the near-shore marine trophic status of biota and biomagnification of OCs from the southern Beaufort-Chukchi Seas (1999-2000) near Barrow, AK. The biota examined included zooplankton (Calanus spp.), fish species such as arctic cod (Boreogadus ...
Lima Mauricio - - 2002
Understanding the role of interactions between intrinsic feedback loops and external climatic forces is one of the central challenges within the field of population ecology. For rodent dynamics, the seasonal structure of the environment necessitates changes between two stages: reproductive and non-reproductive. Nevertheless, the interactions between seasonality, climate, density dependence ...
Sanzone D M - - 2003
Adult aquatic insects emerging from streams may be a significant source of energy for terrestrial predators inhabiting riparian zones. In this study, we use natural abundance delta(13)C and delta(15)N values and an isotopic (15)N tracer addition to quantify the flow of carbon and nitrogen from aquatic to terrestrial food webs ...
Katsuhiko Yoshida
Living fossils are taxonomic groups surviving for a long time without any remarkable morphological change. Most of them retain low taxonomic diversities. Although some of them have survived in refuges to avoid predators and competitors, not all living fossils live in refuges. The survival of these groups, therefore, should be ...
Lucas Eric - - 2002
In northeast Spain, the most common predators found in tomato fields and greenhouses are the mirids Macrolophus caliginosus Wagner and Dicyphus tamaninii Wagner. Natural colonization occurs during the growing season and both species prey on whiteflies. Because D. tamaninii can damage tomato fruits during periods of prey scarcity, a semifield ...
Oyeka C A - - 2002
A total of 100 young adults (67 males and 33 females) participated in the study. Clinical evaluation showed that only 10 of the volunteers showed some scaling, fissuring and peeling of the toe webs. Four of these complained of occasional itching. Fourteen different genera of fungi were recovered from 78 ...
Remes Vladimír - - 2002
The reasons why growth and developmental rates vary widely among species have remained unclear. Previous examinations of possible environmental influences on growth rates of birds yielded few correlations, leading to suggestions that young may be growing at maximum rates allowed within physiological constraints. However, estimations of growth rates can be ...
Mara B. Boveri,O Quirs
Introduction Planktivorous fish directly suppress some prey species and indirectly affect species that interact with these prey (HRBACEK 1962, BROOKS & DODSON 1965, HALL et al. 1970, DRENNER et al. 1986). Visually feeding zooplanktivorous fish are size-selective predators, directly suppressing large zooplankton, and indirectly temporarily enhancing small zooplankton and phytoplankton ...
Lindström Torsten - - 2002
In this paper we derive and analyze a discrete version of Rosenzweig's (Am. Nat. 1973) food-chain model. We provide substantial analytical and numerical evidence for the general dynamical patterns of food chains predicted by De Feo and Rinaldi (Am. Nat. 1997) remaining largely unaffected by this discretization. Our theoretical analysis ...
Ruus Anders - - 2002
The accumulation of polychlorinated biphenyls (PCBs), DDTs (p,p'-DDT [1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane], o,p'-DDT [1,1,1-trichloro-2-(2-chlorophenyl)-2-(4-chlorophenyl)ethane], p,p'-DDD [1,1,-dichloro-2,2-bis(4-chlorophenyl)ethane], o.p'-DDD [1,1-dichloro-2-(2-chlorophenyl)-2-(4-chlorophenyl)ethane], and p,p'-DDE [1,1-dichloro-2,2-bis(4-chlorophenyl)ethene]), chlordanes (trans-chlordane, cis-chlordane, trans-nonachlor, cis-nonachlor and oxychlordane), hexachlorocyclohexanes (alpha-, beta-, and gamma-isomers), hexachlorobenzene, and mirex was investigated in a marine food web from southeastern Norway. The food web consisted of the polychaete ...
Dostálková Iva - - 2002
Mathematical models of predator-prey population dynamics are widely used for predicting the effect of predators as biocontrol agents, but the assumptions of the models are more relevant to parasite-host systems. Predator-prey systems, at least in insects, substantially differ from what is assumed by these models. The main differences are: (i) ...
Punzo F - - 2002
The purpose of this study was to determine if environmental chemical cues associated with prey can affect subsequent prey choice in wolf spiderlings (Hogna carolinensis). After emergence from the egg sac, three groups of 10 spiderlings were each fed for one-week on one of three naturally-occurring prey species: group 1 ...
Lohse David P - - 2002
Previous workers have demonstrated that sessile filter feeders compete for food and space, but little is known about the relative strengths of these two processes. To determine this, the density and position of barnacles (Balanus improvisus) in a unidirectional current were manipulated to alter the amount of competition for space ...
Weissburg Marc J - - 2002
To locate food, mobile consumers in aquatic habitats perceive and move towards sources of attractive chemicals. There has been much progress in understanding how consumers use chemicals to identify and locate prey despite the elusive identity of odor signals and the complex effects of turbulence on chemical dispersion. This review ...
Luesch H - - 2002
It is increasingly evident that the true biological origin of many metabolites originally isolated from certain marine macroorganisms is cyanobacterial. For example, several dolastatins, potent cytotoxic compounds originally derived from the sea hare Dolabella auricularia, have now been isolated from marine cyanobacteria of the genera Lyngbya and Symploca. This review ...
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