			Home About us Contact

Individual Responses (individual + response)

Distribution by Scientific Domains

Life Sciences	51%
Medical Sciences	14%
Humanities and Social Sciences	9%
Psychology	7%
Earth and Environmental Science	7%
Business, Economics, Finance and Accounting	4%
2 Other Domains	8%

Selected Abstracts

Individual response of growing pigs to lysine intake

JOURNAL OF ANIMAL PHYSIOLOGY AND NUTRITION, Issue 5 2009
J. Heger
Summary Nitrogen (N) balance experiment was carried out to study the individual and group response of growing pigs to lysine (Lys) intake. A series of 15 purified diets limiting in Lys were fed sequentially to nine pigs (initial body weight, 39 kg) during a 15-day experiment. Lysine concentration ranged from 50% to 140% of its assumed requirement. N retention in individual pigs was related to Lys intake using linear-plateau (LP) and quadratic-plateau (QP) models. No difference in the closeness of fit between the models was found (p = 0.72). There were significant differences between the slopes of individual regression lines in the LP model (p = 0.018) and between the individual plateau values in both models (p < 0.0001). The breakpoint values in the QP model were greater than those of the LP model (p = 0.027), while the plateau values estimated by both models were similar (p = 0.32). In the LP model, no relationship was found between the slopes and plateau values (p = 0.67, r = 0.17) or between the slopes and breakpoint values (p = 0.55, r = ,0.23), thus suggesting that pigs with higher protein deposition rate do not utilize lysine more efficiently. However, there was a close positive correlation between breakpoint and plateau values (p = 0.0005, r = 0.92). Based on LP and QP models, the mean daily requirement of Lys for a 47-kg gilt was estimated to be 20.8 and 24.2 g (0.79 and 0.92 g/MJ metabolizable energy), respectively, with coefficients of variation of approximately 10%. Marginal efficiency of Lys utilization derived from the LP model was 0.67 and was dependent on the range of input data selected. Lysine disappearance was a curvilinear function of Lys intake, indicating that Lys catabolism is not directly related to Lys intake. The closeness of fit of exponential, saturation kinetics or four-parameter logistic models applied to data set of all pigs was similar to that of LP or QP models. [source]

Individual response of growing pigs to sulphur amino acid intake

JOURNAL OF ANIMAL PHYSIOLOGY AND NUTRITION, Issue 1 2008
J. Heger
Summary Two N balance experiments were conducted to study the individual response of growing pigs to limiting amino acid (AA) intake. Series of fifteen diets with increasing concentration of sulphur amino acids (SAA, Expt 1) or methionine in the presence of excess cystine (Expt 2) were fed sequentially to nine pigs during a 15-day experimental period. The concentration of the AA under test ranged from 50% to 140% of the requirement while other essential AA were given in a 25% excess relative to the limiting AA. N retention was related to the limiting AA intake using rectilinear and curvilinear models. In Expt 1, the quadratic-plateau model fitted the individual data significantly better (p = 0.01) than the linear-plateau model. No difference was found between the two models in Expt. 2, presumably due to the sparing effect of excess cystine on methionine utilization. Exponential, saturation kinetics or four-parameter logistic models fitted to data for all pigs showed that their goodness of fit was similar to those of quadratic-plateau or linear-plateau models. Significant differences (p < 0.05) were found between individual plateau values for N retention within each experiment while the slopes of the regression lines did not significantly differ either in Expt 1 (p = 0.07) or Expt 2 (p = 0.45). There was a positive correlation between the slope and plateau values of the linear-plateau model in Expt 1 (r = 0.74, p = 0.02) but no significant correlation was found in Expt 2 (r = ,0.48, p = 0.13). Marginal efficiencies of SAA and methionine utilization derived from the linear-plateau model were 0.43 and 0.65 respectively. Based on linear-plateau and quadratic-plateau models, daily requirements of SAA and methionine for a 50 kg pig were estimated to be 13.0 and 5.9 g and 14.3 and 6.1 g respectively. [source]

A longitudinal study over 5 to 10 years of clinical outcomes in women with idiopathic detrusor overactivity

BJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 2 2008
AR Morris
Objective, To evaluate the long-term clinical outcome in women with idiopathic detrusor overactivity (IDO) and to identify significant prognostic factors. Design, Longitudinal study incorporating retrospective case note review and a postal questionnaire. Setting, Tertiary referral urogynaecology clinic in Australia. Population, Women with a sole urodynamic diagnosis of IDO. Methods, Audit of urodynamic records and case notes. Postal questionnaire incorporating validated disease-specific quality-of-life (QoL) instruments. Main outcome measure, Subjective assessment of overall improvement on a 4-point scale followed by scoring of short forms of the urogenital distress inventory and incontinence impact questionnaire. Results, One hundred and thirty two women were identified following examination of 1975 consecutive records with 76 (67%) returning questionnaires. Median follow up was 8 years (6,9), and the duration of symptoms was 13 years (9,18). Improvement was achieved in 25 (35%) women. Disease symptoms fluctuated in severity and QoL were worse in nonresponders to therapy (P < 0.0001). Urge incontinence at presentation was associated with treatment failure (P= 0.001) as was nocturia (P= 0.04), but urodynamic variables were not associated with outcome. Only 3 of 46 (6.5%) women not responding to therapy thought that their symptoms would improve with time. Conclusions, IDO seldom resolves and fluctuates in severity. Individual response is unpredictable, although the presence of urge incontinence is associated with a significantly worse prognosis. [source]

Individual responses of seabirds to commercial fisheries revealed using GPS tracking, stable isotopes and vessel monitoring systems

JOURNAL OF APPLIED ECOLOGY, Issue 2 2010
Stephen C. Votier
Summary 1.,The large amount of discards produced by commercial fisheries can have major impacts on marine predator populations: this abundant food may increase populations of some scavengers or decrease others via accidental bycatch. Yet, despite the conservation implications of discard practices, the ecology of individual scavengers is poorly understood. 2.,Here, we assess the influence of commercial fisheries' activity on the foraging behaviour of individual breeding northern gannets Morus bassanus. Using recent developments in stable isotope mixing models (Stable Isotope Analysis in R or SIAR) we estimate individual discard consumption. Using GPS tracking and the Vessel Monitoring System (VMS), we investigate behavioural responses to trawlers. 3.,Analysis of conventional diet samples, as well as stable isotope ratios of carbon and nitrogen in blood (plasma and cells), highlight marked individual differences in the proportion of fishery discards in the diet. Individual differences in foraging behaviour revealed by stable isotopes show evidence of both short-term consistency and behavioural flexibility. 4.,At-sea path tortuosity of 25 gannets (tracked using GPS loggers) revealed scale-dependent adjustments in response to VMS-derived fishing vessel locations, as well as to sea surface temperature, chlorophyll a concentration and copepod abundance. The results also indicate individual variability in behavioural response to trawlers. 5.,Individual differences in the amount of discards estimated from SIAR were negatively correlated with differences in foraging trip length and body condition, indicating potential fitness consequences. 6.,Synthesis and applications. The management of commercial fisheries and apex predators is a daunting task. Ultimately, reducing bycatch and removing dependency on discards remain key conservation priorities, but managers should also ensure that scavenging species have sufficient alternative food to meet their energetic needs, to ameliorate potential unforeseen knock-on consequences. The results of Stable Isotope Analysis (SIAR) reveal intra-population differences in discard consumption by gannets; differences that have impacts on foraging effort and body condition. The use of GPS tracking and Vessel Monitoring Systems (VMS) reveal that gannet at-sea behaviour is influenced by fishing vessels, although this also varies among individuals. A combination of SIAR, GPS tracking and VMS can be used to study fishery/scavenger interactions in detail at the individual level, to answer fundamental questions about scavenging behaviour. [source]

Chimpanzee responses to researchers in a disturbed forest,farm mosaic at Bulindi, western Uganda

AMERICAN JOURNAL OF PRIMATOLOGY, Issue 10 2010
Matthew R. McLennan
Abstract We describe the behavior of a previously unstudied community of wild chimpanzees during opportunistic encounters with researchers in an unprotected forest,farm mosaic at Bulindi, Uganda. Data were collected during 115 encounters between May 2006 and January 2008. Individual responses were recorded during the first minute of visual contact. The most common responses were "ignore" for arboreal chimpanzees and "monitor" for terrestrial individuals. Chimpanzees rarely responded with "flight". Adult males were seen disproportionately often relative to adult females, and accounted for 90% of individual responses recorded for terrestrial animals. Entire encounters were also categorized based on the predominant response of the chimpanzee party to researcher proximity. The most frequent encounter type was "ignore" (36%), followed by "monitor" (21%), "intimidation" (18%) and "stealthy retreat" (18%). "Intimidation" encounters occurred when chimpanzees were contacted in dense forest where visibility was low, provoking intense alarm and agitation. Adult males occasionally acted together to repel researchers through aggressive mobbing and pursuit. Chimpanzee behavior during encounters reflects the familiar yet frequently agonistic relationship between apes and local people at Bulindi. The chimpanzees are not hunted but experience high levels of harassment from villagers. Human-directed aggression by chimpanzees may represent a strategy to accommodate regular disruptions to foraging effort arising from competitive encounters with people both in and outside forest. Average encounter duration and proportion of encounters categorized as "ignore" increased over time, whereas "intimidation" encounters decreased, indicating some habituation occurred during the study. Ecotourism aimed at promoting tolerance of wildlife through local revenue generation is one possible strategy for conserving great apes on public or private land. However, the data imply that habituating chimpanzees for viewing-based ecotourism in heavily human-dominated landscapes, such as Bulindi, is ill-advised since a loss of fear of humans could lead to increased negative interactions with local people. Am. J. Primatol. Am. J. Primatol. 72:907,918, 2010. © 2010 Wiley-Liss, Inc. [source]

In situ substrate conversion and assimilation by nitrifying bacteria in a model biofilm

ENVIRONMENTAL MICROBIOLOGY, Issue 9 2005
Armin Gieseke
Summary Local nitrification and carbon assimilation activities were studied in situ in a model biofilm to investigate carbon yields and contribution of distinct populations to these activities. Immobilized microcolonies (related to Nitrosomonas europaea/eutropha, Nitrosomonas oligotropha, Nitrospira sp., and to other Bacteria) were incubated with [14C]-bicarbonate under different experimental conditions. Nitrifying activity was measured concomitantly with microsensors (oxygen, ammonium, nitrite, nitrate). Biofilm thin sections were subjected to fluorescence in situ hybridization (FISH), microautoradiography (MAR), and local quantification of [14C]-bicarbonate uptake (beta microimaging). Nitrifying activity and tracer assimilation were restricted to a surface layer of different thickness in the various experiments (substrate or oxygen limitation). Excess oxygen uptake under all conditions revealed heterotrophic activity fuelled by decay or excretion products during active nitrification. Depth limits and intensity of tracer incorporation profiles were in agreement with ammonia-oxidation activity (measured with microsensors), and distribution of incorporated tracer (detected with MAR). Microautoradiography revealed a sharp individual response of distinct populations in terms of in-/activity depending on the (local) environmental conditions within the biofilm. Net in situ carbon yields on N, expressed as e, equivalent ratios, varied between 0.005 and 0.018, and, thus, were in the lower range of data reported for pure cultures of nitrifiers. [source]

Individual response of growing pigs to sulphur amino acid intake

Evaluation of window flight traps for effectiveness at monitoring dead wood-associated beetles: the effect of ethanol lure under contrasting environmental conditions

AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 2 2009
C. Bouget
Abstract 1,Subsequent to the diversity of saproxylic beetles being proposed as a management tool in forestry, more explicit knowledge about the efficiency and selective properties of beetle sampling methods is needed. 2,We compared saproxylic beetle assemblages caught by alcohol-baited or unbaited window traps in different forest contexts. Considering that trap attractiveness depends on kairomone concentrations, we appraised whether the trap efficiency was influenced by trap environment (openness and local supply of fresh dead wood). 3,Saproxylic beetles were sampled using 48 cross-vane window flight traps, arranged in paired designs (alcohol-baited/unbaited), in eight ancient and eight recent gaps (open stands), and eight closed-canopy control stands in an upland beech forest in the French Pyrenees. 4,Baited traps were more efficient than unbaited traps in terms of abundance and richness in our deciduous forests. The ethanol lure did not have any repellent effect on the individual response of saproxylic taxa. 5,The influence of local environmental conditions on trap attractiveness was observed. Openness had a significant moderate effect on species richness. Trap attractiveness was slightly reduced in the alcohol-saturated environment of recent gaps probably due to a disruption by local fresh dead-wood concentrations of the kairomonal response of saproxylic beetles to baited traps (,alcohol disruption'). 6,Because the ethanol lure enhanced the probability of species detection, it may be useful in early-warning surveillance, monitoring and control of wood borers, despite slight influences of local conditions on baited trap efficiency. [source]

European Federation of Neurological Societies/Peripheral Nerve Society Guideline, on management of multifocal motor neuropathy.

JOURNAL OF THE PERIPHERAL NERVOUS SYSTEM, Issue 1 2006
Report of a joint task force of the European Federation of Neurological Societies, the Peripheral Nerve Society
Abstract Background: Several diagnostic criteria for multifocal motor neuropathy (MMN) have been proposed in recent years, and a beneficial effect of intravenous immunoglobulin (IVIg) and various other immunomodulatory drugs has been suggested in several trials and uncontrolled studies. Objectives: The aim of this guideline was to prepare consensus guidelines on the definition, investigation, and treatment of MMN. Methods: Disease experts and a representative of patients considered references retrieved from MEDLINE and the Cochrane Library in July 2004 and prepared statements that were agreed in an iterative fashion. Recommendations: The Task Force agreed on good practice points to define clinical and electrophysiological diagnostic criteria for MMN and investigations to be considered. The principal recommendations and good practice points were as follows: (1) IVIg (2 g/kg given over 2,5 days) should be considered as the first line of treatment (level A recommendation) when disability is sufficiently severe to warrant treatment; (2) corticosteroids are not recommended (good practice point); (3) if initial treatment with IVIg is effective, repeated IVIg treatment should be considered (level C recommendation). The frequency of IVIg maintenance therapy should be guided by the individual response (good practice point). Typical treatment regimens are 1 g/kg every 2,4 weeks or 2 g/kg every 4,8 weeks (good practice point); (4) if IVIg is not (or not sufficiently) effective, then immunosuppressive treatment may be considered. Cyclophosphamide, cyclosporine, azathioprine, interferon-,1a, or rituximab are possible agents (good practice point); and (5) toxicity makes cyclophosphamide a less desirable option (good practice point). [source]

Density-dependent reproduction in the European rabbit: a consequence of individual response and age-dependent reproductive performance

OIKOS, Issue 3 2004
Heiko G. Rödel
Density dependence of reproduction has generally been proposed to be caused by habitat heterogeneity and by the individual response of reproductive output. However, a further mechanism might generate density dependence of average reproductive rates. High density situations might be associated with a high proportion of first-season breeders which often show a principally lower reproductive performance. We tested for the existence of the latter mechanism as well as for density-dependent individual changes of reproductive effort in a population of European rabbits living in a homogeneous grassland habitat. The study was conducted over a period of eleven years. Overall, a strong relationship between mean reproductive rates and the breeding density of females was apparent. All necessary conditions for the presence of a density-dependent effect caused by age-dependent reproduction were fulfilled: Fluctuations of breeding density were paralleled by variations in the proportion of one-year-old females. These one-year-old, first-season breeders showed a consistently lower reproductive performance than older females, which might be caused by their lower body mass and their lower social rank. However, we also found strong evidence for density-dependent response of individual reproductive effort: Individual changes in fecundity over successive years were explained by changes in the breeding density of females. The results suggest that density dependence of reproduction in European rabbits is due to an interaction of age-dependent reproductive performance together with short-term fluctuations in breeding density, and a density-dependent, individual based response of reproductive rates. We further conclude that the lower reproductive performance of first-season breeders in age-structured animal populations may contribute substantially to interannual, and under particular circumstances to density-dependent variations of mean reproductive rates. [source]

Experience with topiramate monotherapy in elderly patients with recent-onset epilepsy

ACTA NEUROLOGICA SCANDINAVICA, Issue 3 2005
J. Gro
Objectives,,, To evaluate the effect of topiramate in elderly patients with onset of epilepsy after the age of 60, treatment-naive or non-responding to an initial antiepileptic drug. Methods,,, Analysis of patients with epilepsy diagnosed in the preceding 5 years, aged ,65 years (n = 43), enrolled in a larger open-label trial (n = 692). After titration to topiramate 100 mg/day over 4 weeks, the dose was adjusted according to individual response (maximum 400 mg/day). Patients were followed up for at least 7 months. Results,,, After 7 months, 79% of patients remained in the study. Seizure frequency decreased significantly vs baseline (P < 0.001); ,50% reduction in seizure frequency was achieved in 87% of patients, 64% remained seizure-free. Both previously treated and naive patients responded. Fourteen per cent dropped out because of insufficient tolerability. No unexpected or unusual adverse events were observed. Conclusions,,, The results indicate that elderly patients respond well to topiramate monotherapy. The high patient retention rate reflects a favourable tolerability profile in this population. [source]

Using fractional exhaled nitric oxide to guide asthma therapy: design and methodological issues for ASthma TReatment ALgorithm studies

CLINICAL & EXPERIMENTAL ALLERGY, Issue 4 2009
P. G. Gibson Prof.
Summary Background Current asthma guidelines recommend treatment based on the assessment of asthma control using symptoms and lung function. Noninvasive markers are an attractive way to modify therapy since they offer improvedselection of active treatment(s) based on individual response, and improvedtitration of treatment using markers that are better related to treatment outcomes. Aims: To review the methodological and design features of noninvasive marker studies in asthma. Methods Systematic assessment of published randomized trials of asthma therapy guided by fraction of exhaled nitric oxide(FENO). Results FENO has appeal as a marker to adjust asthma therapy since it is readily measured, gives reproducible results, and is responsive to changes in inhaled corticosteroid doses. However, the five randomised trials of FENO guided therapy have had mixed results. This may be because there are specific design and methodological issues that need to be addressed in the conduct of ASthma TReatment ALgorithm(ASTRAL) studies. There needs to be a clear dose response relationship for the active drugs used and the outcomes measured. The algorithm decision points should be based on outcomes in the population of interest rather than the range of values in healthy people, and the algorithm used needs to provide a sufficiently different result to clinical decision making in order for there to be any discernible benefit. A new metric is required to assess the algorithm performance, and the discordance:concordance(DC) ratio can assist with this. Conclusion Incorporating these design features into future FENO studies should improve the study performance and aid in obtaining a better estimate of the value of FENO guided asthma therapy. [source]

Immunological response to cytomegalovirus in congenitally infected neonates

CLINICAL & EXPERIMENTAL IMMUNOLOGY, Issue 3 2007
J. Hassan
Summary Cytomegalovirus (CMV) is the most common cause of congenital infection worldwide and occurs as a result of transplacental transmission of the virus. The human neonate is highly susceptible to infection due to a combination of immaturity of the immune system and antigenic inexperience. This study uses the in vivo model of congenital CMV to examine both the humoral and cell-mediated immune responses in vertically infected neonates and their mothers. Ten pairs of matched neonates and their mothers were evaluated for specific IgM responses to three immunodominant CMV antigens: pp38 (pUL80a), pp52 (pUL44) and pp150 (pUL32). In contrast to conventional enzyme immunoassay (EIA) testing for CMV-specific IgM, which found five of the mothers and four of the neonates to be positive, Western immunoblotting showed all 10 adults and nine newborns to be positive. Eight mothers and nine newborns had serological evidence of primary infection. All neonates showed a response to pp38, an assembly protein, nine responded to the pp52 immediate early antigen but only four had reactivity to the pp150 tegument associated protein. Of the mothers, eight had pp38 reactivity, 10 showed a response to the pp52 antigen and seven to the pp150 antigen. T cell-mediated immunity was assessed by measuring cytokines using a multiplex microarray assay. Levels of interferon (IFN)-, were high in both groups [mean ± standard error of the mean (s.e.m.): neonates = 657 ± 238 pg/ml, mothers = 1072 ± 677 pg/ml, pNS]; however, neonates had significantly higher levels of interleukin (IL)-8 (316 ± 136 pg/ml versus 48 ± 28 pg/ml, P < 0·005). Similar levels of IL-2, IL-7, IL-10 and IL-12 were measured in both groups, but levels of IL-1,, IL-1,, IL-4, IL-6 and tumour necrosis factor (TNF)-, were either absent or low. In response to CMV, neonates and adults mount a predominant T helper 1 (Th1) response, as evidenced by the presence of IL-2, IL-8, IL-12 and IFN-, with concomitant lack of IL-4. These findings suggest that the neonate, when presented with infection in utero, is capable of mounting an individual response; however, the lower IFN-, and higher IL-8 levels suggest reduced immune responsiveness when compared to their adult counterparts. [source]

Access to Land, Rural Development and Public Action: The When and the How

DEVELOPMENT POLICY REVIEW, Issue 1 2009
Pablo Bandeira
After being marginalised in the 1980s, land-reform policies came back to national and international development agendas during the 1990s, resulting in a revival of academic research on the subject. This article reviews the empirical literature on access to land, rural development and public action for evidence on when and how the state should intervene in the allocation of rural land. The review suggests that positive impacts are obtained if, and only if, public actions on the allocation of land are carried out under certain conditions and in a certain way. The article ends by highlighting the need to elaborate empirical models that take into consideration opportunity costs and interactions, and that integrate individual responses with aggregate effects. [source]

Physiological requirement for the glutamate transporter dEAAT1 at the adult Drosophila neuromuscular junction

DEVELOPMENTAL NEUROBIOLOGY, Issue 10 2006
Thomas Rival
Abstract L -Glutamate is the major excitatory neurotransmitter in the mammalian brain. Specific proteins, the Na+/K+ -dependent high affinity excitatory amino acid transporters (EAATs), are involved in the extracellular clearance and recycling of this amino acid. Type I synapses of the Drosophila neuromuscular junction (NMJ) similarly use L -glutamate as an excitatory transmitter. However, the localization and function of the only high-affinity glutamate reuptake transporter in Drosophila, dEAAT1, at the NMJ was unknown. Using a specific antibody and transgenic strains, we observed that dEAAT1 is present at the adult, but surprisingly not at embryonic and larval NMJ, suggesting a physiological maturation of the junction during metamorphosis. We found that dEAAT1 is not localized in motor neurons but in glial extensions that closely follow motor axons to the adult NMJ. Inactivation of the dEAAT1 gene by RNA interference generated viable adult flies that were able to walk but were flight-defective. Electrophysiological recordings of the thoracic dorso-lateral NMJ were performed in adult dEAAT1-deficient flies. The lack of dEAAT1 prolonged the duration of the individual responses to motor nerve stimulation and this effect was progressively increased during physiological trains of stimulations. Therefore, glutamate reuptake by glial cells is required to ensure normal activity of the Drosophila NMJ, but only in adult flies. © 2006 Wiley Periodicals, Inc. J Neurobiol, 2006 [source]

Liquidity in Asset Markets With Search Frictions

ECONOMETRICA, Issue 2 2009
Ricardo Lagos
We develop a search-theoretic model of financial intermediation in an over-the-counter market and study how trading frictions affect the distribution of asset holdings and standard measures of liquidity. A distinctive feature of our theory is that it allows for unrestricted asset holdings, so market participants can accommodate trading frictions by adjusting their asset positions. We show that these individual responses of asset demands constitute a fundamental feature of illiquid markets: they are a key determinant of trade volume, bid,ask spreads, and trading delays,the dimensions of market liquidity that search-based theories seek to explain. [source]

The extrapolation problem and how population modeling can help,

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2008
Valery E. Forbes
Abstract We argue that population modeling can add value to ecological risk assessment by reducing uncertainty when extrapolating from ecotoxicological observations to relevant ecological effects. We review other methods of extrapolation, ranging from application factors to species sensitivity distributions to suborganismal (biomarker and "-omics") responses to quantitative structure,activity relationships and model ecosystems, drawing attention to the limitations of each. We suggest a simple classification of population models and critically examine each model in an extrapolation context. We conclude that population models have the potential for adding value to ecological risk assessment by incorporating better understanding of the links between individual responses and population size and structure and by incorporating greater levels of ecological complexity. A number of issues, however, need to be addressed before such models are likely to become more widely used. In a science context, these involve challenges in parameterization, questions about appropriate levels of complexity, issues concerning how specific or general the models need to be, and the extent to which interactions through competition and trophic relationships can be easily incorporated. [source]

Field assessments in conjunction with whole effluent toxicity testing

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2000
Thomas W. La Point
Abstract Whole effluent toxicity (WET) tests are widely used to assess potential effects of wastewater discharges on aquatic life. This paper represents a summary of chapters in a 1996 Society of Environmental Toxicology and Chemistry,sponsored workshop and a literature review concerning linkages between WET testing and associated field biomonitoring. Most published studies thus far focus primarily on benthic macroinvertebrates and on effluent-dominated stream systems in which effluents demonstrate little or no significant acute toxicity. Fewer studies examine WET test predictability in other aquatic ecosystems (e.g., wetlands, estuaries, large rivers) or deal with instream biota such as fish and primary producers. Published results indicate that standards for the usual WET freshwater test species, Ceriodaphnia dubia and Pimephales promelas, may not always protect most of the species inhabiting a receiving stream. Although WET tests are useful in predicting aquatic individual responses, they are not meant to directly measure natural population or community responses. Further, they do not address bioconcentration or bioaccumulation of hydrophobic compounds; do not assess eutrophication effects in receiving systems; and lastly, do not reflect genotoxic effects or function to test for endocrine-disrupting chemicals. Consequently, a more direct evaluation of ecosystem health, using bioassessment techniques, may be needed to properly evaluate aquatic systems affected by wastewater discharges. [source]

Behavioral Syndromes in Stable Social Groups: An Artifact of External Constraints?

ETHOLOGY, Issue 12 2008
Ximena J. Nelson
Individuals of many species differ consistently in their behavioral reactions toward different stimuli, such as predators, rivals, and potential mates. These typical reactions, described as ,behavioral syndromes' or ,personalities,' appear to be heritable and therefore subject to selection. We studied behavioral syndromes in 36 male fowl living in 12 social groups and found that individuals behaved consistently over time. Furthermore, responses to different contexts (anti-predator, foraging, and territorial) were inter-correlated, suggesting that males exhibited comparable behavioral traits in these functionally distinct situations. We subsequently isolated the same roosters and conducted tests in a ,virtual environment,' using high-resolution digital video sequences to simulate the anti-predator, foraging, and territorial contexts that they had experienced outdoors. Under these controlled conditions, repeatability persisted but individual responses to the three classes of stimuli failed to predict one another. These were instead context-specific. In particular, production of each type of vocal signal was independent, implying that calls in the repertoire are controlled by distinct mechanisms. Our results show that extrinsic factors, such as social position, can be responsible for the appearance of traits that could readily be mistaken for the product of endogenous characters. [source]

Evolutionary ecology, sexual conflict, and behavioral differentiation among baboon populations

EVOLUTIONARY ANTHROPOLOGY, Issue 5 2003
Peter Henzi
Abstract A central assumption of baboon socio-ecological models is that all populations have the same capacity to react to different environments. The burden of our argument is that this assumption needs to be reconsidered. Data suggest not only that hamadryas, but chacma as well, differ in interesting ways from the stock baboon model that has been derived, in the main, from earlier work on anubis and cynocephalus. Although environmental factors are behind these differences, much of their influence is a consequence of their effect on restricted ancestral populations, where selection for appropriate responses to the social challenges set by local conditions now constrains the nature of individual responses to contemporary environments. Available genetic evidence suggess a southern African origin for Papio at a time when climatic conditions were certainly no better than they are now and when temperatures, if nothing else, were probably lower. In light of this, a reconstruction of how climate has structured the sexual conflict between males and female charcma, which itself hinges on infanticide, can help explain not only the East African pattern, but also how the apparently anomalous hamadryas pattern has been derived. [source]

Sex-dependent use of information on conspecific feeding activities in an amphibian urodelian

FUNCTIONAL ECOLOGY, Issue 2 2009
Pedro Aragón
Summary 1Animals can make decisions by observing the behaviour of others. Their decisions vary depending on whether the benefits of using such information exceed the costs. Thus, it is worthwhile to explore the potential costs associated with different sources of information to understand the consequences of sociality. Previous studies focused mainly on the costs inherent to information gathering, whereas sex differences with regard to the costs arising from information use have received less attention. 2To explore this further I performed two complementary experiments. The first experiment aimed to examine individual responses to different combinations of information types that are likely to appear in nature, to test whether there is a sex-dependent response in the Bosca's newt, Lissotriton boscai. I tested the time needed for individuals to eat food items by trial-and-error tactics (personal information), and when a conspecific, which was eating or not, was added to the food cue. The second experiment aimed to evoke social interactions that are likely to arise after the choice of using information on conspecific feeding activities is made. I examined the potential costs associated with direct competition between same-sex pairs in food-limited conditions. 3Results of experiment 1 revealed that in both sexes the latency to eat food items was shorter in the presence of non-feeding conspecifics, but only females took advantage when information related to feeding activities where added to the food cue. Results of experiment 2 showed that when faced with a limited resource of food, females were more prone to engage in costly interactions. 4This study suggests that the balance between costs and benefits associated with the short-term use of information on conspecific feeding behaviour in combination with food cues may differ between sexes. Differential information uses by sexes might have profound consequences in intraspecific relationships and in the evolution of vertebrates' social systems. [source]

Transient climate simulation forced by natural and anthropogenic climate forcings

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 6 2002
Cédric Bertrand
Abstract Numerical experiments have been carried out with a two-dimensional sector-averaged global climate model coupled to a diffusive ocean in order to assess the potential impact of four hypothesized mechanisms of decadal to century-scale climate variability, both natural and anthropogenically induced: (1) solar variability; (2) variability in volcanic aerosol loading of the atmosphere; (3) anthropogenic increase of sulphate aerosols' concentration; (4) anthropogenic increase of greenhouse gas concentrations. Our results suggest that neither the individual responses nor the combined natural or anthropogenic forcings allow one to reproduce all of the recorded major temperature fluctuations since the latter half of the 19th century. They show that these temperature variations are the result of both naturally driven climate fluctuations and the effects of industrialization. By contrast, the dominant cause of decade-to-century-scale variability of the 21st century is likely to be changes in atmospheric trace-gas concentrations. Indeed, when the solar, volcanic, and tropospheric aerosols forcings used in our experiments are extended into the future, they are unable to counter the expected greenhouse warming. Copyright © 2002 Royal Meteorological Society. [source]

No experimental evidence for local competition in the nestling phase as a driving force for density-dependent avian clutch size

JOURNAL OF ANIMAL ECOLOGY, Issue 4 2009
Marion Nicolaus
Summary 1In birds, local competition for food between pairs during the nestling phase may affect nestling growth and survival. A decrease in clutch size with an increase in breeding density could be an adaptive response to this competition. To investigate whether breeding density causally affected the clutch size of great tits (Parus major), we manipulated breeding density in three out of eight study plots by increasing nest-box densities. We expected clutch size in these plots to be reduced compared to that in control plots. 2We analysed both the effects of variation in annual mean density (between-year comparisons) and experimental density (within-year comparison between plots) on clutch size variation, the occurrence of second broods and nestling growth. We examined within-female variation in clutch size to determine whether individual responses explain the variation over years. 3Over the 11 years, population breeding density increased (from 0·33 to 0·50 pairs ha,1) while clutch size and the occurrence of second broods decreased (respectively from 10·0 to 8·5 eggs and from 0·39 to 0·05), consistent with a negative density-dependent effect for the whole population. Nestling growth showed a declining but nonsignificant trend over years. 4The decline in population clutch size over years was primarily explained by changes occurring within individuals rather than selective disappearance of individuals laying large clutches. 5Within years, breeding density differed significantly between manipulated plots (0·16 pairs ha,1 vs. 0·77 pairs ha,1) but clutch size, occurrence of second broods and nestling growth were not affected by the experimental treatment, resulting in a discrepancy between the effects of experimental and annual variation in density on reproduction. 6We discuss two hypotheses that could explain this discrepancy: (i) the decline in breeding performance over time was not due to density, but resulted from other, unknown factors. (ii) Density did cause the decline in breeding performance, but this was not due to local competition in the nestling phase. Instead, we suggest that competition acting in a different phase (e.g. before egg laying or after fledgling) was responsible for the density effect on clutch size among years. [source]

Timing is everything: flexible phenology and shifting selection in a colonial seabird

JOURNAL OF ANIMAL ECOLOGY, Issue 2 2009
Thomas E. Reed
Summary 1In order to reproduce successfully in a temporally varying environment, iteroparous animals must exhibit considerable behavioural flexibility across their lifetimes. By adjusting timing of breeding each year, parents can ensure optimal overlap between the energy intensive period of offspring production and the seasonal peak in favourable environmental conditions, thereby increasing their chances of successfully rearing young. 2Few studies investigate variation among individuals in how they respond to fluctuating conditions, or how selection acts on these individual differences, but this information is essential for understanding how populations will cope with rapid environmental change. 3We explored inter-annual trends in breeding time and individual responses to environmental variability in common guillemots Uria aalge, an important marine top predator in the highly variable California Current System. Complex, nonlinear relationships between phenology and oceanic and climate variables were found at the population level. Using a novel application of a statistical technique called random regression, we showed that individual females responded in a nonlinear fashion to environmental variability, and that reaction norm shape differed among females. 4The pattern and strength of selection varied substantially over a 34-year period, but in general, earlier laying was favoured. Females deviating significantly from the population mean laying date each year also suffered reduced breeding success, with the strength of nonlinear selection varying in relation to environmental conditions. 5We discuss our results in the wider context of an emerging literature on the evolutionary ecology of individual-level plasticity in the wild. Better understanding of how species-specific factors and local habitat features affect the timing and success of breeding will improve our ability to predict how populations will respond to climate change. [source]

Do community-level models describe community variation effectively?

JOURNAL OF BIOGEOGRAPHY, Issue 10 2010
Andrés Baselga
Abstract Aim, The aim of community-level modelling is to improve the performance of species distributional models by taking patterns of co-occurrence among species into account. Here, we test this expectation by examining how well three community-level modelling strategies (,assemble first, predict later', ,predict first, assemble later', and ,assemble and predict together') spatially project the observed composition of species assemblages. Location, Europe. Methods, Variation in the composition of European tree assemblages and its spatial and environmental correlates were examined with cluster analysis and constrained analysis of principal coordinates. Results were used to benchmark spatial projections from three community-based strategies: (1) assemble first, predict later (cluster analysis first, then generalized linear models, GLMs); (2) predict first, assemble later (GLMs first, then cluster analysis); and (3) assemble and predict together (constrained quadratic ordination). Results, None of the community-level modelling strategies was able to accurately model the observed distribution of tree assemblages in Europe. Uncertainty was particularly high in southern Europe, where modelled assemblages were markedly different from observed ones. Assembling first and predicting later led to distribution models with the simultaneous occurrence of several types of assemblages in southern Europe that do not co-occur, and the remaining strategies yielded models with the presence of non-analogue assemblages that presently do not exist and that are much more strongly correlated with environmental gradients than with the real assemblages. Main conclusions, Community-level models were unable to characterize the distribution of European tree assemblages effectively. Models accounting for co-occurrence patterns along environmental gradients did not outperform methods that assume individual responses of species to climate. Unrealistic assemblages were generated because of the models' inability to capture fundamental processes causing patterns of covariation among species. The usefulness of these forms of community-based models thus remains uncertain and further research is required to demonstrate their utility. [source]

A scalar analysis of landscape connectivity

OIKOS, Issue 2 2003
Article first published online: 4 JUL 200
Landscape connectivity is critical to the maintenance of spatially-structured populations and consists of both a structural component, which describes the shape, size and location of landscape features; and a biological component, which consists of both the response of individuals to landscape features, and the patterns of gene flow that result from those individual responses. Traditional studies of landscape connectivity have attempted to discern individual behavioral responses to landscape features, but this methodology is intractable for many species. This paper is an attempt to relate the components of landscape connectivity through the explicit treatment of their spatial and temporal scales. Traditional measures of structural and biological components of connectivity are reviewed and more recently developed methods for the analysis of scale for each are introduced. I then present a framework for the comparison of scalar phenomena based on Watt's unit pattern, describe the potential outcomes of the comparison and discuss the implications of each. Several testable hypotheses emerge from the analysis that may serve as a useful framework for the investigation of landscape connectivity in the future. [source]

Influence of plant quality on pine sawfly population dynamics

OIKOS, Issue 3 2000
Stig Larsson
The contribution of plant quality to the population dynamics of herbivorous insects has been an issue of much controversy. Many studies have documented how variable plant quality differentially influences the survival and fecundity of insect individuals. Whether or not such effects can be translated to the level of insect populations is, however, not clear. In order to test this hypothesis one needs to combine processes at both the level of the individual and the population. This is difficult with an empirical approach, but could be achieved by means of modeling given that appropriate data exist for both levels of organization. In this paper we report on a model developed to analyze whether altered Scots pine (Pinus sylvestris) quality can contribute to the build-up of populations of the European pine sawfly (Neodiprion sertifer). Experimental data on responses of sawfly larvae to variable plant quality, i.e. needle concentrations of resin acids, were used to parameterize the model. Larval survival and sawfly fecundity are reduced at high resin acid concentrations. However, high resin acid concentrations are, at the same time, beneficial because larval defense against predators is enhanced. In the model, data on individual responses were combined with literature data at the population level; a type III functional response related to cocoon predation was presumed to be the density-dependent process regulating sawfly populations. The analysis showed that the risk for an outbreak is high when needle resin acid concentration (r) or larval predation pressure (p) is low. When r or p is high there is no risk. By analyzing different scenarios it was found that small changes in r and p can result in the sawfly population moving from low to high outbreak risk. Changes of the same, or larger, magnitude in r have been observed in empirical studies. The role of tritrophic interactions was also considered. This was done by removing the positive effects of resin acids on larval performance in the model. It was found that the anti-predator defense of N.sertifer makes it prone to outbreak under wider combinations of r and p than an insect without the defense. We conclude that small changes in a density-independent factor, such as needle chemistry, can have significant effects on herbivore population dynamics because increased fecundity and survival caused by needle quality may allow the population to escape the control of density-dependent factors, such as cocoon predation. [source]

Terrorists and Democrats: Individual Reactions to International Attacks

POLITICAL PSYCHOLOGY, Issue 3 2002
Alice F. Healy
Three experiments conducted in 1997 and 1998 explored individual responses to reported fictitious international conflict involving the United States and other nations. Participants escalated the conflictual level of their responses to repeated attacks. In Experiment 1, escalation of conflict was greater in response to terrorist attacks than to military ones. In Experiment 2, after the initial attacks, men were more conflictual in responding to terrorist attacks by a democratic nation than by a nondemocratic nation, whereas the opposite pattern was found for women. In Experiment 3, participants responded with a higher level of conflict to terrorist attacks on military targets than to attacks on cultural/educational targets. Participants with greater personality dominance showed steeper escalation of conflict in their responses across successive attacks. These results are interpreted within the framework of an image theory of international relations and an expansion of the democratic peace hypothesis. [source]

Summary to the symposium issue: Primate fallback strategies as adaptive phenotypic plasticity,Scale, pattern, and process

AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 4 2009
Joanna E. Lambert
Abstract In this discussion, I evaluate our understanding of fallback foods in primate and hominin ecology and evolution with reference to the challenges of nomenclature, scale, and of linking individual responses to food availability and properties (process) to species traits (pattern). I use these challenges to form the framework of my discussion and ultimately conclude that we situate the discussion of primate fallback strategy into a broader, "synthetic" framework of animal form and the evolutionary significance of phenotypic plasticity. Am J Phys Anthropol 140:759,766, 2009. © 2009 Wiley-Liss, Inc. [source]

Comparing methods for the multi-response design problem

QUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 5 2001
John F. Kros
Abstract One approach to solving multiple response engineering problems is to combine the individual responses into one unifying objective. In tility theory, several characteristics are used to compare and contrast multiple objective techniques. These are risk aversion, marginal rates of substitution, and the relationship of the responses in the combined function. Perhaps unknown to the user, multiple response techniques carry strong assumptions regarding these characteristics. This paper investigates four commonly-used multiple objective techniques and demonstrates that each method contains assumptions about these characteristics which are not intuitively evident to a user. Copyright © 2001 John Wiley & Sons, Ltd [source]