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Results 301 - 350 of 1057
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Dunne Jennifer A - - 2008
A rich body of empirically grounded theory has developed about food webs--the networks of feeding relationships among species within habitats. However, detailed food-web data and analyses are lacking for ancient ecosystems, largely because of the low resolution of taxa coupled with uncertain and incomplete information about feeding interactions. These impediments ...
Tobler Michael - - 2008
Male-biased predation has been described from several epigean species, and in many cases, intrinsic differences between the sexes (such as male ornaments) have been suggested as an explanation. Here we report on male-biased predation of a cave fish (Poecilia mexicana) by an aquatic insect (Belostoma sp.) in a Mexican sulfur ...
Schneider Johanna S - - 2008
Close to 30 forms of gonadotropin releasing hormone (GnRH) and at least five GnRH receptors have been identified in a wide variety of vertebrates and some invertebrates. One form, now called GnRH II, has the broadest distribution and the most ancient and conserved phylogeny. The distribution of the neurons that ...
Mintenbeck, Katja
Knowledge about food web structure and trophic relationships is essential for the identification of bottlenecks and vulnerable compartments to estimate ecosystem response to environmental alterations and its impact on overall ecosystem functioning. Fish take a central position in the Southern Ocean food web as they provide a major trophic link ...
Nfon Erick - - 2008
The trophic transfer of organic pollutants with varying physical chemical properties was determined in both a pelagic and benthic food chain using delta 15N as a continuous variable for assessing trophic levels. The trophic transfer of organic pollutants through the entire food chain in terms of food chain magnification factors ...
Child Travis - - 2008
A mechanistic understanding of factors influencing the dispersal behavior of metamorph cane toads (Bufo marinus) has direct conservation relevance in Australia. These invasive anurans are toxic to native predators, and if we can predict their distribution across the landscape, we can also predict (and perhaps, manage) the scale of their ...
Butler Jessica L - - 2008
Linkages between detritus-based ("brown") food webs and producer-based ("green") food webs are critical components of ecosystem functionality, but these linkages are hard to study because it is difficult to measure release of nutrients by brown food webs and their subsequent uptake by plants. In a three-month greenhouse experiment, we examined ...
Wiese Francis K - - 2008
Predator-prey relationships are often altered as a result of human activities. Where prey are legally protected, conservation action may include lethal predator control. In the Columbia River basin (Pacific Northwest, USA and Canada), piscivorous predators have been implicated in contributing to a lack of recovery of several endangered anadromous salmonids ...
Ruhl Henry A - - 2008
Research capable of differentiating resource-related community-level change from random ecological drift in natural systems has been limited. Evidence for nonrandom, resource-driven change is presented here for an epibenthic megafauna community in the abyssal northeast Pacific Ocean from 1989 to 2004. The sinking particulate organic carbon food supply is linked not ...
Frederiksen Morten - - 2008
Fisheries management across the world is moving toward an ecosystem-based approach, implying that fishery effects on nontarget species should be taken into account. However, such effects are often not well understood, partly because, they can be difficult to distinguish from impacts of environmental fluctuations. We evaluated the effects of an ...
Hebert Craig E - - 2008
Ecosystem change often affects the structure of aquatic communities thereby regulating how much and by what pathways energy and critical nutrients flow through food webs. The availability of energy and essential nutrients to top predators such as seabirds that rely on resources near the water's surface will be affected by ...
Alvy Lisa M - - 2008
In 2006 the Institute of Medicine (IOM) concluded that food marketing was a contributor to childhood obesity in the United States. One recommendation of the IOM committee was for research on newer marketing venues, such as Internet Web sites. The purpose of this cross-sectional study was to answer the IOM's ...
Sandeman L R - - 2008
1. Relative body condition (the quantity of stored energy) is an important tool in understanding demographic variation and the ability of a population to respond to environmental stressors, varying food availability and competition. 2. A high-resolution database was used to examine causes of variation in the condition of north-east Arctic ...
Stenroth Patrik - - 2008
Omnivory is common in many food webs. Omnivores in different habitats can potentially change their feeding behaviour and alter their trophic position and role according to habitat conditions. Here we examine the trophic level and diet of the omnivorous signal crayfish (Pacifastacus leniusculus) in gradients of trophic status and lake ...
Schreiber Sebastian - - 2008
Ecosystems are often indirectly connected through consumers with complex life cycles (CLC), in which different life stages inhabit different ecosystems. Using a structured consumer resource model that accounts for the independent effects of two resources on consumer growth and reproductive rates, we show that such indirect connections between ecosystems can ...
Lugo Carlos A - - 2008
We explore the consequences of modifying the way in which species are defined in an evolutionary food web model. In the original version of the model, the species were defined in terms of a fixed number of features, chosen from a large number of possibilities. These features represented phenotypic and ...
Kuwae Tomohiro - - 2008
We show that a higher vertebrate can graze surficial intertidal biofilm, previously only considered a food source for rasping invertebrates and a few specialized fish. Using evidence from video recordings, stomach contents, and stable isotopes, we describe for the first time the grazing behavior of Western Sandpipers (Calidris mauri) and ...
Nowlin Weston H - - 2008
Resource pulses affect productivity and dynamics in a diversity of ecosystems, including islands, forests, streams, and lakes. Terrestrial and aquatic systems differ in food web structure and biogeochemistry; thus they may also differ in their responses to resource pulses. However, there has been a limited attempt to compare responses across ...
Pekalski Andrzej - - 2008
We investigate in detail the model of a trophic web proposed by Amaral and Meyer [Phys. Rev. Lett. 82, 652 (1999)]. We focus on small-size systems that are relevant for real biological food webs and for which the fluctuations play an important role. We show, using Monte Carlo simulations, that ...
Bluhm Bodil A - - 2008
This review provides an overview of prey preferences of seven core Arctic marine mammal species (AMM) and four non-core species on a pan-Arctic scale with regional examples. Arctic marine mammal species exploit prey resources close to the sea ice, in the water column, and at the sea floor, including lipid-rich ...
Berger Kim Murray - - 2008
The traditional trophic cascades model is based on consumer resource interactions at each link in a food chain. However, trophic-level interactions, such as mesocarnivore release resulting from intraguild predation, may also be important mediators of cascades. From September 2001 to August 2004, we used spatial and seasonal heterogeneity in wolf ...
Hernandez Alexander D - - 2008
Relatively few published food webs have included parasites, and in this study we examined the animal community in a stream across eight contiguous seasons to test how inclusion of helminth parasites alters the topology or structure of the food web. Food webs constructed for each season and analyzed using common ...
Pruzzo Carla - - 2008
The interaction of Vibrio cholerae with chitin exemplifies for microbial ecology a successful bacteria-substrate interaction with complex and significant influence on the lifestyle of the bacterium. Chitin is one of the most abundant polymers on earth and possibly the most abundant in the aquatic environment, where its association with V. ...
Clarke Andrew - - 2008
Antarctic krill (Euphausia superba) is a large euphausiid, widely distributed within the Southern Ocean [1], and a key species in the Antarctic food web [2]. The Discovery Investigations in the early 20(th) century, coupled with subsequent work with both nets and echosounders, indicated that the bulk of the population of ...
Jiwyam Wirat - - 2008
Participating farms in the Muang district of Nong Khai Province, were selected for the investigation of management practices and yields of marble goby, Oxyeleotris marmoratus, in integrated culture with Nile tilapia (Oreochromis niloticus). The research took place from February to May, 2007. The observed production of O. marmoratus in integrated ...
Wan Yi - - 2008
Polybrominated diphenyl ethers (PBDEs) are of great environmental concern due to the exponential increase of the concentrations in the environment, especially in high trophic level organisms, and the trophodynamics of these chemicals in aquatic food webs is an important criterion for assessing their ecological risk. This study analyzed 13 PBDEs ...
Montserrat Marta - - 2008
1. When intraguild (IG)-prey are superior to IG-predators in competing for a shared resource, theory predicts coexistence of the IG-prey or the IG-predator with the resource depending on the productivity level: (a) resource and IG prey coexist when productivity is low; (b) IG-predator and resource coexist at high productivity; (c) ...
Benincà Elisa - - 2008
Mathematical models predict that species interactions such as competition and predation can generate chaos. However, experimental demonstrations of chaos in ecology are scarce, and have been limited to simple laboratory systems with a short duration and artificial species combinations. Here, we present the first experimental demonstration of chaos in a ...
Statzner Bernhard - - 2008
Is there a relationship between the abundance of organisms and particular biological attributes? To assess this old, yet still acutely debated key question of ecology, we have used large databases on 312 stream macroinvertebrate genera (from 27 orders) that describe (1) invertebrate abundance at 527 least human-impacted European stream sites, ...
Le Bohec Céline - - 2008
Seabirds are sensitive indicators of changes in marine ecosystems and might integrate and/or amplify the effects of climate forcing on lower levels in food chains. Current knowledge on the impact of climate changes on penguins is primarily based on Antarctic birds identified by using flipper bands. Although flipper bands have ...
Bukovinszky Tibor - - 2008
The diversity and complexity of food webs (the networks of feeding relationships within an ecological community) are considered to be important factors determining ecosystem function and stability. However, the biological processes driving these factors are poorly understood. Resource quality affects species interactions by limiting energy transfer to consumers and their ...
Hannon, B.
We developed an input-output model of the Southern North Sea ecosystem in order to determine the relationships between 10 biotic and abiotic stock levels and to investigate how their direct and indirect dependency changed through the typical year. Ecologists now examine stomach contents of top carnivores, for example, to evaluate ...
MOUILLOT, D
The number of links in webs of species interactions, which lies at the heart of the biodiversity-stability debate, has given rise to controversy during the last 20 yr. Studies exploring these web properties have mainly focused on symmetric webs where each species can potentially feed on any other species; asymmetric ...
Griffin John N - - 2008
The link between biodiversity and ecosystem functioning is now well established, but the challenge remains to develop a mechanistic understanding of observed effects. Predator-prey interactions provide an opportunity to examine the role of resource partitioning, thought to be a principal mediator of biodiversity-function relationships. To date, interactions between multiple predators ...
Moore Jonathan W - - 2008
Understanding how abundance regulates the effects of organisms on their ecosystems remains a critical goal of ecology, especially for understanding inter-ecosystem transfers of energy and nutrients. Here we examined how territoriality and nest-digging by anadromous salmon mediate trophic subsidies to stream fishes. Salmon eggs become available for consumption primarily by ...
Handel Stephen - - 2008
The physical properties that signify objects differ dramatically, so that the organization of sensory systems must reflect those differences. Although all senses may encode peripheral sensory information using across-fiber firing distributions, an economical coding system for each sense will necessarily differ. An economical code must maximize information about objects, whether ...
Higgins J E JE - - 2008
Like that of most scyphozoans, the ontogeny of Cyanea capillata medusae involves substantive alterations in feeding structures and mechanics. We used video and optical microscopy approaches to quantify these ontogenetic changes in morphology, flow, and feeding of C. capillata medusae. We found that alterations in gross morphology and nematocyst distributions ...
Philpott S M - - 2008
1. Ants are important predators in agricultural systems, and have complex and often strong effects on lower trophic levels. Agricultural intensification reduces habitat complexity, food web diversity and structure, and affects predator communities. Theory predicts that strong top-down cascades are less likely to occur as habitat and food web complexity ...
Ross Robert M - - 2008
We compared naturally alkaline streams with limestone lithology to freestone streams with and without acid mine drainage (AMD) to predict benthic macroinvertebrate community recovery from AMD in limestone-treated watersheds. Surrogate-recovered (limestone) and, in many cases, freestone systems had significantly higher macroinvertebrate densities; diversity; taxa richness; Ephemeroptera, Plecoptera, and Trichoptera (EPT) ...
Kriwet Jürgen - - 2008
We describe the first known occurrence of a Permian shark specimen preserving two temnospondyl amphibians in its digestive tract as well as the remains of an acanthodian fish, which was ingested by one of the temnospondyls. This exceptional find provides for the first time direct evidence of a vertebrate three-level ...
Kumagai Naoki H - - 2008
Small marine invertebrates often use sessile organisms as microhabitats, which can provide food sources and/or serve as refugees from predators. Because of the availability of external food items such as epibionts and detritus in the marine environment, these invertebrates may not depend on the sessile organisms as sole food sources. ...
Tinker M Tim - - 2008
Dietary diversity often varies inversely with prey resource abundance. This pattern, although typically measured at the population level, is usually assumed to also characterize the behavior of individual animals within the population. However, the pattern might also be produced by changes in the degree of variation among individuals. Here we ...
Ims Rolf A - - 2008
During the past two decades population cycles in voles, grouse and insects have been fading out in Europe. Here, we discuss the cause and implication of these changes. Several lines of evidence now point to climate forcing as the general underlying cause. However, how climate interacts with demography to induce ...
Martínez-Padilla Jesús - - 2008
Predation has received considerable theoretical and empirical support in population regulation. The effect of predators, however, could be achieved in direct (killing) or indirect effects (such as displacement). In this paper, we explored the relationship between Eurasian kestrels Falco tinnunculus and skylarks Alauda arvensis in Mediterranean grasslands. First, we analysed ...
Tzilkowski, Caleb J
Introduced trout have had direct and indirect effects on native fishes, amphibians, and invertebrates that have in some cases, induced detrimental community- and ecosystem-level effects. Recently, some North American agencies have invested substantial time, effort, and resources to eradicate exotic salmonids due to their documented or presumed negative effects on ...
Walsh Matthew R - - 2008
The ecological impacts of the indirect effects of predators are well established, but the evolutionary consequences are unknown. Predators often decrease prey density, which indirectly increases the resources available to surviving prey. This ecological effect could provide a link to evolution because it is generally assumed that resource availability influences ...
McLeod, Rebecca Jane
The secondary productivity of communities is inherently influenced by the availability and quality of food resources. Movement of organic matter (OM) across landscapes can connect adjacent systems by providing subsidies of carbon and nutrients, implying that alterations of environments from their natural state may affect the productivity of neighboring food ...
Greig, Hamish Stuart
Ecological communities along gradients of environmental stress are thought to be structured by trade-offs between resisting biotic interactions in physically benign habitats and successfully exploiting physically stressful habitats. However, these trade-offs are likely to be affected by the predictability of abiotic stressors, and variation in the strength of biotic interactions. ...
Liebhold Andrew M - - 2008
During the establishment phase of a biological invasion, population dynamics are strongly influenced by Allee effects and stochastic dynamics, both of which may lead to extinction of low-density populations. Allee effects refer to a decline in population growth rate with a decline in abundance and can arise from various mechanisms. ...
Moline Mark A - - 2008
Polar regions have experienced significant warming in recent decades. Warming has been most pronounced across the Arctic Ocean Basin and along the Antarctic Peninsula, with significant decreases in the extent and seasonal duration of sea ice. Rapid retreat of glaciers and disintegration of ice sheets have also been documented. The ...
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