bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance of DNAPL Source Depletion Technologies at 59 Chlorinated Solvent‐Impacted Sites
Authors: McGuire Travis M. , McDade James M. , Newell Charles J.
Published: February 2006

Performance and rebound of intensive source depletion technologies were evaluated at 59 chlorinated solvent sites where remediation targeted dense non–aqueous phase liquid (DNAPL) source zones. The four technologies included in the study are chemical oxidation, enhanced bioremediation, thermal treatment, and surfactant/cosolvent flushing. Performance was evaluated by examining temporal ground water concentration data before and after source remediation was performed. Results indicated that all four technologies have median concentration reductions of 88% or greater for the parent chlorinated volatile organic compound (CVOC). Approximately 75% of the source depletion projects were able to achieve a 70% reduction in parent compound concentrations. A median reduction in total CVOC concentrations (parent plus daughter compounds) of 72% was observed at 12 chemical oxidation sites and 62% at 21 enhanced bioremediation sites. Rebound was assessed at sites having at least 1 year of posttreatment data. Rebound occurrence was most prevalent at sites implementing chemical oxidation. At chemical oxidation sites where rebound was evaluated (n= 7), the median parent CVOC concentration reduction was 90% immediately following treatment compared to 78% at the end of posttreatment monitoring (i.e., 1 to 5 years after treatment). For enhanced bioremediation sites where rebound was evaluated (n= 10), median parent CVOC concentration reduction changed from 77% to 96% over the posttreatment monitoring period. Minimal concentration change was observed over the posttreatment monitoring period at surfactant/cosolvent sites (n= 2) and thermal treatment sites (n= 1) evaluated for rebound. Based on current data, none of the 59 source depletion projects was able to meet maximum contaminant levels throughout the treatment zone for all CVOCs.
Low‐Temperature MTBE Biodegradation in Aquifer Sediments with a History of Low, Seasonal Ground Water Temperatures
Authors: Bradley P.M. , Landmeyer J.E.
Published: February 2006

Sediments from two shallow, methyl tert‐butyl ether (MTBE)–contaminated aquifers, with mean ground water temperatures ∼10°C, demonstrated significant mineralization of [U‐14C] MTBE to 14CO2 at incubation temperatures as low as 4°C. These results indicate that microbial degradation can continue to contribute to the attenuation of MTBE in ground water under wintertime, low‐temperature conditions.
Measured Gene-Environment Interactions in Psychopathology
Authors: Moffitt Terrie E. , Caspi Avshalom , Rutter Michael
Published: February 2006

There is much curiosity about interactions between genes and environmental risk factors for psychopathology, but this interest is accompanied by uncertainty. This article aims to address this uncertainty. First, we explain what is and is not meant by gene-environment interaction. Second, we discuss reasons why such interactions were thought to be rare in psychopathology, and argue instead that they ought to be common. Third, we summarize emerging evidence about gene-environment interactions in mental disorders. Fourth, we argue that research on gene-environment interactions should be hypothesis driven, and we put forward strategies to guide future studies. Fifth, we describe potential benefits of studying measured gene-environment interactions for basic neuroscience, gene hunting, intervention, and public understanding of genetics. We suggest that information about nurture might be harnessed to make new discoveries about the nature of psychopathology.
A pilot plant evaluation of the Magnetic Ion EXchange® process for the removal of dissolved organic carbon at Draycote water treatment works
Authors: Shorrock Katie , Drage Brian
Published: February 2006

Natural organic matter (NOM) in water sources is undesirable for customers because it reacts with chlorine to form trihalomethanes (THMs), which can be harmful to health, and other organochlorine compounds that can cause taste complaints. A new Magnetic Ion EXchange process (MIEX® DOC) has been reported as being successful in removing NOM from raw water. The aim of this research was (a) to evaluate the performance of the MIEX® process in removing NOM from hard, lowland water on a pilot plant scale and (b) to compare the performance of the MIEX® process with low pH coagulation DAF, in particular, with respect to reducing THM levels. A 45 and 40% reduction in the amount of NOM and in the levels of THMs, respectively, in chlorine‐dosed water was achieved when the MIEX® process was used with dissolved air flotation (DAF).
Experimental investigations of air and liquid injection by venturi tubes
Authors: Ozkan Fahri , Ozturk Mualla , Baylar Ahmet
Published: February 2006

The venturi system creates a pressure differential that forms a vacuum. As water flows through the tapered venturi orifice, a rapid change in velocity occurs. This velocity change creates a reduced pressure (vacuum), which draws air and liquid to be injected into the system. The air and liquid injection rates vary with the pressure differential across the venturi. Typical applications of venturi tubes are for injecting fertilizers, chemicals, ozone gas, air or oxygen into pressurized water systems. In this paper, experimental studies were conducted to investigate the effects of inlet and throat diameters of the venturi tube, pipe length downstream of the venturi tube, diameter of the suction pipe at the throat portion of the venturi tube, angle of the pipe downstream of the venturi tube, flow velocity at the inlet portion of the venturi tube and density and viscosity of the liquid injected into the venturi tube on air and liquid injection rate. It was observed from the results that venturi tubes had high air and liquid injection efficiencies.
Preliminary laboratory investigation of disinfection by‐product precursor removal using an advanced oxidation process
Authors: Murray Christine A. , Parsons Simon A.
Published: February 2006

Natural organic matter (NOM) is ubiquitous in surface and ground waters throughout the world. During drinking water treatment, the NOM that remains in treated water can react with chlorine to form disinfection by‐products. It has been shown that titanium dioxide photocatalysis can achieve over 96% reduction in ultraviolet (UV)254 absorbing species such as hydrophobic NOM and over 81% reduction in dissolved organic carbon (DOC). However, an additional filtration stage is required to recover the suspended catalyst before it is suitable for municipal drinking water application. To overcome this problem, we have used immobilised catalysts prepared using chemical sol–gels, and their performance has been assessed during bench‐scale experiments. An immobilised catalyst enables in situ regeneration using UV light and subsequent reuse of the catalyst. In this research, titanium dioxide sol–gels have been used to coat substrates at a laboratory scale. Results showed that the various coatings prepared had different removal efficiencies for both DOC and UV254 absorbance. Maximum removals were 1.336 g/m2 and 89%, respectively.
A decision support system for identifying the habitat quality and rehabilitation potential of urban rivers
Authors: Boitsidis A. J. , Gurnell A. M. , Scott M. , Petts G. E. , Armitage P. D.
Published: February 2006

Few habitat survey, classification or assessment methodologies have been developed specifically for urban or heavily engineered rivers, and yet these rivers need careful assessment if management options are to be considered and prioritised in an economically and environmentally effective way. This paper presents a refinement of a previously proposed urban river survey (URS), which is a modification of the Environment Agency's River Habitat Survey. It then describes indices and classifications that have been developed from URS data and that provide a link between the type of engineering applied to a stretch of urban river and its habitat characteristics. Finally, some simple decision trees and scenario‐modelling tools are presented that allow (i) newly surveyed urban stretches to be classified and (ii) some simple scenarios of channel management change to be assessed in order to prioritise management options for stretches of urban river across urban catchments.
Monitoring a flood event in a densely instrumented catchment, the Upper Eden, Cumbria, UK
Authors: Mayes W.M. , Walsh C.L. , Bathurst J.C. , Kilsby C.G. , Quinn P.F. , Wilkinson M.E. , Daugherty A.J. , O'Connell P.E.
Published: February 2006

Multi‐day rainfall events appear to be an important cause of recent flooding in the UK. Hydrological data from an extensive, nested hydrometric network in the unregulated, predominantly rural Upper Eden catchment in northern England are presented for one such flood event. These highlight antecedent catchment conditions and the propagation of the multi‐day flood event during February 2004. An assessment of flood response is provided over varying scales and land use between the upland Gais Gill catchment (1.1 km2) and the larger Upper Eden catchment (616 km2). Large spatial variations in rainfall totals are identified from a dense raingauge network during the flood event and are principally related to catchment elevation. High cumulative rainfall totals for the 6‐day event, particularly at upland sites appear to be the exceptional feature of the flood event with return periods in the order of 100 years at some upland gauges. Resultant patterns of flood attenuation and translation are quantified in different areas of the catchment, highlighting the flashy response of the headwater catchments and the attenuated downstream response in the lowland environment. The study forms part of the national Catchment Hydrology And Sustainable Management (CHASM) programme.
Pesticides in groundwater: some observations on temporal and spatial trends
Authors: Lapworth D.J. , Gooddy D.C. , Stuart M.E. , Chilton P.J. , Cachandt G. , Knapp M. , Bishop S.
Published: February 2006

Following a monitoring programme of private shallow boreholes a total of 22 different pesticides were detected in 14 shallow boreholes in the Triassic Sherwood Sandstone aquifer of south Yorkshire, UK between January 2002 and November 2003. Of the 294 positive detections made, 34% were detected in excess of the permitted concentration value (PCV) (drinking water standard) for individual pesticides. Pesticides were detected in 11 (78%) of the boreholes, and in eight (57%) at concentrations exceeding the PCV on at least one occasion. These findings were complemented by data from deeper boreholes in which concentrations exceeding the PCV were also detected. Pesticide occurrence could be related to landuse; mecoprop and isoproturon were frequently detected at several locations reflecting the arable landuse, dicamba at a golf course, and atrazine, propazine and terbutryn near a railway. Temporal variations have emerged at individual sites and across the study area as the result of extended and frequent monitoring.
An examination of the surface characteristics of activated sludge in relation to bulking during the treatment of paper mill wastewater
Authors: Agridiotis V. , Forster C. F. , Balavoine C. , Wolter C. , Carliell‐Marquet C.
Published: February 2006

The addition of mineral talc, Aquatal®(Toulouse, France), to activated sludge treating paper mill effluents and its effect on settlement characteristics has been investigated. One laboratory study and a full‐scale investigation on a large waste water treatment plant (WWTP) with a capacity of 500.000 population equivalent (p.e.) have been carried out using this mineral. The sludge in the full‐scale plant was filamentous and had specific sludge volume index (SSVI) values in excess of 250. The talc dosing which was adapted to sludge settleability reduced SSVI values by 38%, improved the total suspended solids' concentrations by 86% and reduced the specific sludge load by 34%. In the laboratory‐scale plant, the sludge had SSVI values of 200–260 before treatment and was hydrophilic. The use of Aquatal® at a dose of 0.7 g/g mixed liquor suspended solids (MLSS) took 2 weeks to reduce the SSVI to 78. It also increased the hydrophobicity to a balanced 50%. The use of mineral converted the somewhat diffuse flocs into a compact structure.
JFLOW: a multiscale two‐dimensional dynamic flood model
Authors: Bradbrook Kate
Published: February 2006

A multiscale two‐dimensional (2D) dynamic flood model, known as JFLOW, has been developed by JBA Consulting for simulation of overland flooding. This paper first describes the background to the model development before explaining its technical basis. The model is based on a 2D diffusion wave equation and the computational engine has been linked with a geographic information system interface to provide a stand‐alone product. It has been applied on a variety of different scales which are illustrated in a number of example applications.
Biodegradation of domestic wastewater under the simulated conditions of Thailand
Authors: Giri R. R. , Takeuchi J. , Ozaki H.
Published: February 2006

Serious concerns have been raised about the sustainability of conventional mechanized linear wastewater treatment systems in the developing world. Bangkok in Thailand is no exception to these concerns, and merits closer examination. This paper is aimed at unveiling the fundamental facts and characteristics relating to the organic degradation potentials of domestic wastewater in Bangkok. It is supported by evidence from simple laboratory experiments in which existing local conditions were simulated. The results showed that greywater‐like qualities of domestic wastewater do predominate in Bangkok, most probably as a result of three main factors: (1) continued use of leaching septic tanks, (2) the tradition of using water after defecation, instead of toilet paper, and (3) high organic degradation potentials under tropical monsoon conditions. Considering the small organic content, coupled with high organic degradation rates of the freshly collected greywater‐based sewage in Bangkok, low‐cost and decentralized natural treatment systems could be far more suitable for environmental sustainability in such tropical monsoon areas than the implementation of large‐scale sewage works.
Complex interactions on fig trees: ants capturing parasitic wasps as possible indirect mutualists of the fig–fig wasp interaction
Authors: Schatz Bertrand , Proffit Magali , Rakhi B. V. , Borges Renee M. , Hossaert‐McKey Martine
Published: February 2006

Like other mutualisms, pollination mutualisms attract parasites, as well as opportunistic and specialist predators of the pollinators and parasites. These associated species influence the evolutionary dynamics of pairwise mutualisms. Predatory ants are frequent associates of pollination mutualisms, but their effects on the complex interactions between plants, pollinators and parasites have not yet been clearly established, even in the case of the well‐described obligate interaction between figs and fig wasps. We attempted to quantify such effects for ants associated with three fig species, two dioecious (Ficus condensa[Bruneï],F.carica[France]) and one monoecious (F.racemosa[India]). In all these cases, ant presence on a fig tree strongly reduced the number of parasitic wasps on the figs. Experimental exclusion of ants resulted in an increase in the number of non‐pollinating fig wasps onF.condensaandF.racemosa. Experimental ant supplementation led to a decrease in the number of non‐pollinating fig wasps onF.carica. Moreover, onF.condensa, the level of reduction of the number of parasitic wasps depended on the number and identity of the ants. OnF.carica, non‐pollinating fig wasps even avoided trees occupied by the dominant predatory ant. The consistency of the effect of ants in these three cases, representing a geographically, ecologically, and taxonomically broad sample of figs, argues for the generality of the effect we observed. Because reduction of parasitism benefits the pollinator, ants may be considered as indirect mutualists of plants and pollinators in the network of complex interactions supported by fig trees.
Why are small seeds dispersed through animal guts: large numbers or seed size per se?
Authors: Henrik Bruun Hans , Poschlod Peter
Published: February 2006

Long‐distance dispersal of seeds is an important process in metapopulation dynamics and in plant migrations, but at the same time extremely difficult to observe or quantify directly. If seed dispersal ability were related to attributes of seeds or motherplants, long‐distance seed dispersal would be predictable by indirect approximation using easy‐to‐measure traits. Seed size has been suggested to be such a key trait in seed dispersal ability. However, having smaller seeds also implies having more numerous seeds per plant individual (given equal reproductive effort), and consequently increases the probability of seeds being ingested accidentally. The question is whether small‐seeded species are more abundant in herbivore dung because smaller seed size increases survival rate during gut passage or because they are produced (and ingested) in greater numbers than larger seeds. We investigated endozoochorous seed dispersal via cattle grazing a meadow, and related seed abundance in dung samples to seed attributes. We found that seeds were ingested and passed through the bovine intestinal tract in proportion to the numbers produced per unit area in the grazed vegetation. In contrast, no relationship could be found between endozoochorous dispersal potential (measured as abundance of seeds in dung samples corrected for seed output in the grazed vegetation) and seed attributes such as seed mass, seed shape (roundness), and thickness of the seed coat. This finding underlines the importance of seed number in plant dispersal ability. In addition, it shows that grazing mammals may constitute an important dispersal vector for many plant species conventionally classified as ‘unspecialised’.
Functional group diversity, resource preemption and the genesis of invasion resistance in a community of marine algae
Authors: H. Britton‐Simmons Kevin
Published: February 2006

Although many studies have investigated how community characteristics such as diversity and disturbance relate to invasibility, the mechanisms underlying biotic resistance to introduced species are not well understood. I manipulated the functional group composition of native algal communities and invaded them with the introduced, Japanese seaweed Sargassum muticum to understand how individual functional groups contributed to overall invasion resistance. The results suggested that space preemption by crustose and turfy algae inhibited S. muticum recruitment and that light preemption by canopy and understory algae reduced S. muticum survivorship. However, other mechanisms I did not investigate could have contributed to these two results. In this marine community the sequential preemption of key resources by different functional groups in different stages of the invasion generated resistance to invasion by S. muticum. Rather than acting collectively on a single resource the functional groups in this system were important for preempting either space or light, but not both resources. My experiment has important implications for diversity–invasibility studies, which typically look for an effect of diversity on individual resources. Overall invasion resistance will be due to the additive effects of individual functional groups (or species) summed over an invader's life cycle. Therefore, the cumulative effect of multiple functional groups (or species) acting on multiple resources is an alternative mechanism that could generate negative relationships between diversity and invasibility in a variety of biological systems.
Two‐phase self‐thinning in stream‐living juveniles of lake‐migratory brown trout Salmo trutta L. Compatibility between linear and non‐linear patterns across populations?
Authors: Lobón‐Cerviá Javier , Mortensen Erik
Published: February 2006

The self‐thinning rule establishes that, in resource limited populations, increased per‐capita requirements by individuals with indeterminate growth may limit density. This invariant rule relating log‐log linear declines of cohort density with increased body mass has been well established in sessile organisms. However, few studies have assessed the occurrence of self‐thinning in mobile organisms and still fewer have demonstrated its operation in natural situations. In Bisballe Baeck, where brown trout individuals experienced the simultaneous operation of density‐dependence on growth and mortality, increased body mass explained 89.0–98.4% of the variations in density. However, relative to the invariant linear line, the decline in density with increased body mass described distinctly nonlinear, two‐phase trajectories. An initial phase of variable slopes continued until body mass attained ≈10.2 g, at which the direction of the trajectory switched to a second phase of substantially steeper slopes or severe declines of density per mass unit increment. As inferred by the highly significant relationships between these two sets of slopes and annual recruitment, the two phases were consistent with a major assumption of self‐thinning: the rate at which density declined with increased body mass increased with the intensity of intraspecific competition. The results of this study provide prima facie evidence for the occurrence of self‐thinning in a mobile species based on observational data. A further comparison among density–body mass relationships described for resident, anadromous and lake‐migratory brown trout suggests consistent two‐phase self‐thinning patterns across populations.
Trunk cutting initiates bottom‐up cascades in a tri‐trophic system: sprouting increases biodiversity of herbivorous and predaceous arthropods on willows
Authors: Nakamura Masahiro , Kagata Hideki , Ohgushi Takayuki
Published: February 2006

We examined the effects of trunk cutting on the regrowth responses of two dominant willow species, Salix eriocarpa and S. gilgiana, and the subsequent effects on the community structure (abundance and species richness) of herbivorous and predaceous arthropods. We studied ten randomly selected pairs of cut and uncut (control) trees of each willow species. Field observations showed that when the trunks were cut, shoots sprouted from the base and developed rapidly. These shoots continued to grow until July, producing lateral shoots and leaves, whereas current‐year shoots on uncut trees essentially stopped growing by April. In July, the upper leaves of cut trees were less tough and had a greater water and nitrogen content than leaves of uncut trees. Leaf consumption and abundance and species richness of both herbivorous and predaceous arthropods were significantly greater on cut trees than on uncut trees in both willow species. Overall, trunk cutting resulted in at least a two‐fold increase in both relative abundance and species richness within the arthropod community on the willow species. We concluded that the severe physical damage caused by trunk cutting greatly increased the biodiversity of herbivorous and predaceous arthropods through bottom‐up cascading effects.
Underlying effects of spatial aggregation (clumping) in relationships between plant diversity and resource uptake
Authors: De Boeck Hans J. , Nijs Ivan , Lemmens Catherine M. H. M. , Ceulemans Reinhart
Published: February 2006

In the debate on the influence of declining plant diversity on ecosystem functioning, spatial aggregation has received little attention, in spite of the fact that the local distribution of species determines interaction. Using a simple conceptual model, we visualize the effect that clumping has on below ground resource uptake (RU). Two general conclusions can be drawn from the model: (1) clumping results in a loss of RU, and does so to a larger extent when species differ more in rooting depth and when plant density increases; (2) the current view on complementarity may be flawed, as we find that neighborhood species richness only promotes spatial complementarity directly at the transition from monocultures to higher species richness levels, but not at transitions between higher richness levels. The number of species in a community does, however, affect the probability of the occurrence of clumping. In randomly assembled communities, clumps are statistically larger when the number of species is lower, leading to reduced overall below ground complementarity. Complementarity, and thus also RU, will therefore increase indirectly with increasing species richness. As a result of our findings, we propose that clumping could have a number of ‘hidden’ consequences, for example on invasibility of a community and on competition between species. Clumping could also prove to be a new and important explanatory factor in diversity studies, as it extends the definition of complementarity effects to include the effect of spatial heterogeneity of plant positions within the community.
Antagonism between bacteria and fungi: substrate competition and a possible tradeoff between fungal growth and tolerance towards bacteria
Authors: Mille‐Lindblom Cecilia , Fischer Helmut , J. Tranvik Lars
Published: February 2006

Bacteria and fungi often share a common substrate, and their spatial proximity in many environments has lead to either synergistic or antagonistic interactions. In this paper, the interaction of bacterial and fungal decomposers from an aquatic environment was studied. We found indications of a tradeoff between fungal growth and tolerance towards bacteria. Fungal strains growing best in absence of bacteria were most severely affected by bacterial presence, while those less suppressed during co‐existence with bacteria had lower maximal growth rates in bacterial absence. Additionally, we show that the antagonism between bacteria and fungi is connected to competition for substrate, but that this competition can be drastically altered if fungi are given an opportunity to establish before inoculation of bacteria. Established fungi out‐competed bacteria, and gained higher biomass than in simultaneously inoculated treatments with higher substrate concentrations.
An analysis of the analysis of herbivore population dynamics
Authors: Månsson Lena , Lundberg Per
Published: February 2006

Time series analysis of herbivore data with weather included as covariate is commonly used as a mean to shed light on the state and ecology of the studied population. Conclusions about the herbivore population are drawn from statistical parameter values and presence/absence in the most parsimonious model. However, this procedure is only reliable if the statistical parameters have general interpretations regardless of system characteristics. Here we investigated the extent to which this is true by deriving six different vegetation–herbivore‐systems and analyzing their respective statistical parameters. The analysis was done in both continuous and discrete time. It turned out that both density parameters (a1 and a2) and rainfall coefficients change with biological interactions and amount of average rainfall, and they do so in different ways in different systems. This means that there is no valid general interpretation of them and, most important, the probability of detecting density dependence and effects of rainfall vary between systems. Hence, you can not make inference about the biological processes from statistical analysis without knowing the system that you study and what model best describes the interactions within it.
Is the composition of phytophagous insects and parasitic fungi among trees predictable?
Authors: Brändle Martin , Brandl Roland
Published: February 2006

We explore the relationship between the pairwise similarity of assemblages of exploiters (phytophagous insects and parasitic fungi) and pairwise genetic distance, range overlap, niche overlap as well as habitat overlap of host trees. Presence of exploiters was extracted from published literature for 23 tree genera occurring in central Europe (6164 host records of phytophagous insects and 860 host records of parasitic fungi). Across all pairs of tree genera, we found a strong negative correlation between the pairwise similarity of assemblages and genetic distances of hosts. This close correlation is due to deep differences in the composition of assemblages on coniferous and deciduous tree genera. Range, niche and habitat overlap were always of much less importance than genetic distance to explain the variation of pairwise similarity of assemblages of exploiters, although some correlations were significant. Therefore in general host switches of exploiters between related hosts are more important that host switches between hosts co‐occurring in the same habitat. We found a robust relationship of the pairwise similarity of assemblages of insects and the pairwise similarity of assemblages of fungi which points to the possibility that insects are vectors for parasitic fungi which promotes correlated switches of insects and fungi.
Environmental influence and cohort effects in a sexual ornament in the house sparrow,Passer domesticus
Authors: Jensen Henrik , Svorkmo‐Lundberg Torkild , Harald Ringsby Thor , Sæther Bernt‐Erik
Published: February 2006

Presence of phenotypic variation is necessary for selection to occur, yet processes affecting variation in sexually selected characters in natural populations are poorly understood. Here we examine whether variation in a sexual ornament (badge size) of male house sparrows (Passer domesticus) is dependent on individual variation in the conditions during early ontogenetic stages, and whether this variation and the population‐wide effects of external variables such as weather or population size jointly will generate consistent differences among cohorts later in life. Variation in badge size was independent of adult body size, whereas heavier fledglings and fledglings in good body condition developed smaller visible badges as adults. Furthermore, strong cohort‐effects were present, caused by a combined effect of density‐dependence and weather during the early development in the moulting period and autumn after hatching. Thus, badge size is an environmentally‐dependent trait in house sparrows, and likely to be under the influence of both natural and sexual selection.
Tropical rodents change rapidly germinating seeds into long‐term food supplies
Authors: Jansen Patrick A. , Bongers Frans , H. T. Prins Herbert
Published: February 2006

Seed‐hoarding vertebrates may survive yearly periods of food scarcity by storing seeds during the preceding fruiting season. It is poorly understood why rodents creating long‐term reserves, especially those in the tropics, incorporate seeds from plant species that germinate rapidly and hence seem unsuitable for long‐term storage. We carried out a series of experiments to understand why red acouchies (Myoprocta exilis) scatter‐hoardCarapa procera(Meliaceae) seeds, which lack dormancy and germinate rapidly. Hypotheses tested were: (1) even germinated seeds are still significant long‐term energy reserves for acouchies, (2) acouchies use the seeds only as short‐term supplies, and (3) acouchies manipulate the seeds to slow down germination. The first two hypotheses were not supported; seed reserves were rapidly depleted during experimental planting, and acouchies did use seeds for long‐term storage. We did find support for the third hypothesis. Acouchies intervened in germination by removing the protruding radicle and epicotyl after which they re‐cached seeds. Pruning stopped further seedling development, yet the pruned seeds did not decay. The cotyledons apparently stayed alive and physiologically active as “zombie seeds” that only formed undifferentiated calli. Pruned seeds were suitable for long‐term storage, with negligible loss of endosperm over time. Pruning was most effective after sprouting of the epicotyl, and germinating seeds were most susceptible to pruning during two weeks upon emergence. Acouchies actively managed their food supplies and must continuously survey for germinating seeds to timely intervene in seed reserve depletion, within the brief period of seedling emergence. We suggest that the trees use the rodents to achieve seed dispersal, and gain from imperfect intervention in germination by the rodents. Because scatter‐hoarding rodents and large‐seeded plant species with similar germination co‐occur in tropical forests world‐wide, it is plausible that the phenomenon of seed pruning to preserve seeds is more general than currently appreciated.
Species abundance models and patterns in dragonfly communities: effects of fish predators
Authors: Johansson Frank , Englund Göran , Brodin Tomas , Gardfjell Hans
Published: February 2006

We investigated if dragonfly larvae community composition and species abundance curves are sensitive to variation in predation intensity, and whether the fit to a particular niche partitioning model could be used to make inferences about mechanisms structuring communities. The approach taken was to compare communities in lakes either having or lacking fish predation. Dragonfly species classified as active, strongly dominated the dragonfly communities in fishless lakes, and low active species dominated fishless lakes. As activity level is known to correlate with susceptibility to fish predation this indicates that these communities are structured by fish predation. Fitting relative abundance data to five niche partitioning models showed that the same model fitted data from both types of habitats (fish/no fish). This means that the observed differences in relative abundances were substitutive, i.e. the relative abundance of a rank stayed constant, even though the identity of the species having this rank changed. The best fit to data from both types of lakes was found for the random assortment model, which is usually interpreted as an indication that the community is not structured by within‐guild interactions. This interpretation for fishless lakes did not seem to agree with other community measures (i.e. lowered diversity and evenness and no relationship between species richness and dragonfly biomass), which indicate that the community is structured by within‐guild interactions. Moreover, a detail in the fitting procedure, the number of species included in the analysis, affected which model that fitted data best. Thus, we question if fitting niche partitioning models to data can provide mechanistic understanding of how resources are partitioned in natural communities.
Landscape structure and phenotypic plasticity in flight morphology in the butterflyPararge aegeria
Authors: Merckx Thomas , Van Dyck Hans
Published: February 2006

In evolutionary time, varying environments may lead to different morphs as a result of genetic adaptation and divergence or phenotypic plasticity. Landscapes that differ in the extent of habitat fragmentation may provide different selection regimes for dispersal, but also for other ecological functions. Several studies on flying insects have shown differences in flight morphology between landscapes, but whether such differences result from plastic responses have rarely been tested. We did a reciprocal transplant experiment with offspring of speckled wood butterfly females (Parargeaegeria) from three types of landscape differing in fragmentation: woodland landscape, landscape with woodland fragments and agricultural landscape with only hedgerows. Young caterpillars were allowed to grow individually on potted host grasses in small enclosures under the three landscape conditions (split‐brood design). Mortality in caterpillars was much higher in agricultural landscape compared to the other landscapes. Additive to the effect of landscape of development, landscape of origin also affected mortality rate in a similar way. Flight morphology of the adults resulting from the experiment differed significantly with landscape. Independent of the landscape of origin, males and females that developed in agricultural landscape were the heaviest and had the greatest wing loadings. Females that developed in agricultural landscape had higher relative thorax mass (i.e. greater flight muscle allocation) in line with adaptive predictions on altered dispersal behaviour with type of landscape. In males, relative thorax mass did not respond significantly relative to landscape of development, but males originating from landscape with woodland fragments allocated more into their thorax compared to males from the other types. We found significant G×E interactions for total dry mass and wing loading. Our results suggest the existence of phenotypic plasticity in butterfly flight morphology associated with landscape structure.
Effects of enrichment on protist abundances and bacterial composition in simple microbial communities
Authors: Liess Antonia , Diehl Sebastian
Published: February 2006

We experimentally investigated effects of nutrient enrichment and trophic structure in a microbial food web consisting of mixed bacteria, two bacterivorous ciliates (Tetrahymena sp. and Colpidium sp.) and an omnivorous ciliate (Blepharisma sp.) feeding on both trophic levels. We assembled all possible food webs including one or more of the ciliate species and cross‐classified them with four levels of enrichment of the bacterial medium. The qualitative outcome of food web interactions was independent of enrichment and always the same: Tetrahymena strongly depressed or excluded Colpidium, and Blepharisma strongly depressed or excluded both bacterivores. Consequently, in all sub‐webs only the dominant ciliate species responded positively to enrichment. The total density of bacteria increased with enrichment irrespective of food web composition. In contrast, the response of single‐celled bacteria to enrichment depended on food web composition and was only weakly positive in most food webs with the omnivore. Enrichment had a positive effect on the relative success of (presumably more defended) bacterial aggregates. The outcome of interspecific interactions among ciliates could not be predicted from monoculture experiments and deviated from earlier experiments in which each bacterivore coexisted separately with the omnivore. As a potential explanation we suggest that changes in experimental protocol reduced spatial heterogeneity and increased attack rates. A simple, dynamical model shows that increased attack rates can indeed greatly decrease the upper limit and range of enrichment over which intermediate consumers can coexist with omnivores.
Non‐neutral community dynamics: empirical predictions for ecosystem function and diversity from linearized consumer–resource interactions
Authors: Wilson William G. , Lundberg Per
Published: February 2006

A general model of linearized species interactions, essentially Lotka–Volterra theory, applied to questions of biodiversity has previously been shown to be a powerful tool for understanding local species–abundance patterns and community responses to environmental change for a single trophic level. Here this approach is extended to predict community composition and responses to environmental changes in trophically structured systems. We show how resource and consumer species richness and their relative abundances vary with the means and variances in enrichment level and strengths of intra‐ and interspecific interactions. Also demonstrated are the responses of local resource and consumer species richness to the global species pools at both trophic levels, as well as the covariation with net resource productivity. These predictions for resource and consumer specific responses to changes in environmental enrichment and global biodiversity are directly testable.
Consequences of varying regional heterogeneity in source–sink metacommunities
Authors: Mouquet N. , E. Miller T. , Daufresne T. , M. Kneitel J.
Published: February 2006

Although the influence of dispersal on coexistence mechanisms in metacommunities has received great emphasis, few studies have addressed how such influence is affected varying regional heterogeneity. We present a mechanistic model of resource competition in a metacommunity based on classical models of plant competition for limiting resources. We defined regional heterogeneity as the differences in resource supply rates (or resource availabilities) across local communities. As suggested by previous work, the highest diversify occurred at intermediate levels of dispersal among local communities. However our model shows how the effects of dispersal depend on the amount of heterogeneity among local communities and vice versa. Both regional and local species richness were the highest when heterogeneity was intermediate. We suggest that empirical studies that found no evidence for source–sink or mass effects at the community level may have examined communities with limited ranges of dispersal and regional heterogeneity. This model of species coexistence contributes to a broader understanding of patterns in real communities.
Condition‐dependent virulence in a horizontally and vertically transmitted bacterial parasite
Authors: Restif Olivier , Kaltz Oliver
Published: February 2006

Virulence is a key component of parasite fitness. Its expression and selective value may not only depend on the features of the parasite's life cycle, but also on host genotype or environmental conditions. Using the freshwater ciliate Paramecium caudatum and its endonuclear bacterial parasite Holospora undulata, we measured variation in virulence (reduction in host division and survival), parasite load and fidelity of vertical transmission for (i) different stages of infection (associated with different opportunities for vertical and horizontal transmission), (ii) different host clones, and (iii) two food conditions. Later stages of infection dedicated to horizontal transmission were more virulent than earlier stages which rely on vertical transmission only. Besides, investment in horizontal transmission decreased the efficacy of vertical transmission, indicating a tradeoff between the two pathways. This may explain the phenotypic plasticity of transmission mode of this parasite. To some extent, virulence, parasite load and transmission fidelity varied with host clone identity and food treatment (higher virulence at low food). These results suggest that virulence is not a constant property of the parasite, and that a single (and simple) relationship between virulence and transmission does not exist.
Genetic consequences of a demographic bottleneck in the Scandinavian arctic fox
Authors: Nyström V. , Angerbjörn A. , Dalén L.
Published: February 2006

Demographic bottlenecks can result in a loss of genetic variation due to the bottleneck effect and subsequent genetic drift. The arctic fox population in Scandinavia went through a severe demographic bottleneck in the early 20th century, and is today classified as critically endangered. In this study, we investigated the pre‐bottleneck genetic variation in Scandinavia and compared it to modern samples from Scandinavia and North Russia. Variation in the mtDNA control region and five microsatellite loci was examined through ancient DNA analysis on museum specimens. The microsatellite data from the museum specimens was further used to simulate the expected effect of the bottleneck. The arctic foxes in Scandinavia have lost approximately 25% of the microsatellite alleles and four out of seven mtDNA haplotypes. The results also suggest that the genetic differentiation between North Russia and Scandinavia has doubled over the last 100 years. However, the level of heterozygosity was significantly higher than expected from the simulations. This highlights both the advantage of using museum specimens and the importance of generating specific predictions in conservation genetics.
The partitioning of density‐dependent dispersal, growth and survival throughout ontogeny in a highly fecund organism
Authors: Einum Sigurd , Sundt‐Hansen Line , H. Nislow Keith
Published: February 2006

The way in which density‐dependent effects are partitioned amongst survival, growth and dispersal are key in determining the temporal and spatial dynamics of populations. Here we propose a mechanistic approach to understanding how the relative importance of these sources of density dependence can change over ontogeny through changes in dispersal abilities, energy stores and mortality risks. Whereas the potential for active dispersal typically increases over ontogeny as a function of body size, susceptibility to starvation and predation decreases. The joint effect of these mechanisms suggests a general model for the ontogenetic sequence of how density dependence is manifested, with density dependence early in ontogeny being primarily expressed as mortality on local spatial scales, whereas later stages respond to local density in terms of dispersal and potentially growth. Here we test this model by manipulating the densities of juvenile Atlantic salmon (Salmo salarL.) at two life‐history stages in the wild. Density‐dependent mortality during the early juvenile stage (i.e. fry at onset of exogenous feeding) was accompanied by no effects on body size and weak effects on dispersal. In contrast, dispersal of older juveniles (i.e. parr 2–3 months after onset of feeding) was strongly density‐dependent, with more individuals emigrating from high‐density release sites, and with no effect of initial density on mortality. This dispersal, however, appeared insufficient to produce an ideal free distribution within the study stream, as indicated by the effect of spatial variation in density on body size by the end of the first growth season. These results demonstrate that the way density‐dependent effects are partitioned amongst survival, growth and dispersal changes throughout ontogeny. Furthermore, these changes occur in correlation with changes in individual mortality risks and dispersal abilities, and suggest a general paradigm for the way in which juvenile density‐dependence is manifest in spatially structured populations of highly fecund organisms.
Reproductive Social Behavior: Cooperative Games to Replace Sexual Selection
Authors: Roughgarden Joan , Oishi Meeko , Akçay Erol
Published: February 2006

Theories about sexual selection can be traced back to Darwin in 1871. He proposed that males fertilize as many females as possible with inexpensive sperm, whereas females, with a limited supply of large eggs, select the genetically highest quality males to endow their offspring with superior capabilities. Since its proposal, problems with this narrative have continued to accumulate, and it is our view that sexual selection theory needs to be replaced. We suggest an approach that relies on the exchange of direct ecological benefits among cooperating animals without reference to genetic benefits. This approach can be expressed mathematically in a branch of game theory that pertains to bargaining and side payments.
Role of Noradrenergic Signaling by the Nucleus Tractus Solitarius in Mediating Opiate Reward
Authors: Olson Valerie G. , Heusner Carrie L. , Bland Ross J. , During Matthew J. , Weinshenker David , Palmiter Richard D.
Published: February 2006

Norepinephrine (NE) is widely implicated in opiate withdrawal, but much less is known about its role in opiate-induced locomotion and reward. In mice lacking dopamine β-hydroxylase (DBH), an enzyme critical for NE synthesis, we found that NE was necessary for morphine-induced conditioned place preference (CPP; a measure of reward) and locomotion. These deficits were rescued by systemic NE restoration. Viral restoration of DBH expression in the nucleus tractus solitarius, but not in the locus coeruleus, restored CPP for morphine. Morphine-induced locomotion was partially restored by DBH expression in either brain region. These data suggest that NE signaling by the nucleus tractus solitarius is necessary for morphine reward.