bluuebunny/crossref_metadata_2025 huggingface dataset:
Two‐component system VraSR positively modulates the regulation of cell‐wall biosynthesis pathway in Staphylococcus aureus
Authors: Kuroda Makoto , Kuroda Hiroko , Oshima Taku , Takeuchi Fumihiko , Mori Hirotada , Hiramatsu Keiichi
Published: July 2003

DNA microarray covering the whole genome of Staphylococcus aureus strain N315 was prepared to investigate transcription profiles. The microarray analyses revealed that vancomycin induces transcription of 139 genes. Forty‐six genes among them failed to be induced in the vraSR null mutant KVR. Part of the genes regulated by VraSR system is associated with cell‐wall biosynthesis, such as PBP2, SgtB and MurZ. Other cell‐wall synthesis inhibitors also induced VraSR, suggesting that the sensor kinase VraS responds to the damage of cell‐wall structure or inhibition of cell‐wall biosynthesis. Additionally, the vraSR null mutants derived from hetero‐ and homo‐methicillin‐resistant S. aureus showed significant decrease of resistance against teicoplanin, β‐lactam, bacitracin and fosfomycin but not of d‐cycloserine and levofloxacin. The observation strongly indicates that VraSR constitutes a positive regulator of cell‐wall peptidoglycan synthesis, and that is deeply involved in the expression of β‐lactam and glycopeptide resistance in S. aureus.
Genetic characterization of pilin glycosylation and phase variation in Neisseria meningitidis
Authors: Power P. M. , Roddam L. F. , Rutter K. , Fitzpatrick S. Z. , Srikhanta Y. N. , Jennings M. P.
Published: July 2003

Pili of Neisseria meningitidis are a key virulence factor, being the major adhesin of this capsulate organism and contributing to specificity for the human host. Pili are post‐translationally modified by addition of either an O‐linked trisaccharide, Gal (β1‐4) Gal (α1‐3) 2,4‐diacetamido‐2,4,6‐trideoxyhexose or an O‐linked disaccharide Gal (α1,3) GlcNAc. The role of these structures in meningococcal pathogenesis has not been resolved. In previous studies we identified two separate genetic loci, pglA and pglBCD, involved in pilin glycosylation. Putative functions have been allocated to these genes; however, there are not enough genes to account for the complete biosynthesis of the described structures, suggesting additional genes remain to be identified. In addition, it is not known why some strains express the trisaccharide structure and some the disaccharide structure. In order to find additional genes involved in the biosynthesis of these structures, we used the recently published group A strain Z2491 and group B strain MC58 Neisseria meningitidis genomes and the unfinished Neisseria meningitidis group C strain FAM18 and Neisseria gonorrhoeae strain FA1090 genomes to identify novel genes involved in pilin glycosylation, based on homology to known oligosaccharide biosynthetic genes. We identified a new gene involved in pilin glycosylation designated pglE and examined four additional genes pglB/B2, pglF, pglG and pglH. A strain survey revealed that pglE and pglF were present in each strain examined. The pglG, pglH and pglB2 polymorphisms were not found in strain C311♯3 but were present in a large number of clinical isolates. Insertional mutations were constructed in pglE and pglF in N. meningitidis strain C311♯3, a strain with well‐defined lipopolysaccharide (LPS) and pilin‐linked glycan structures. Increased gel migration of the pilin subunit molecules of pglE and pglF mutants was observed by Western analysis, indicating truncation of the trisaccharide structure. Antisera specific for the C311♯3 trisaccharide failed to react with pilin from these pglE and pglF mutants. GC‐MS analysis of the sugar composition of the pglE mutant showed a reduction in galactose compared with C311♯3 wild type. Analysis of amino acid sequence homologies has suggested specific roles for pglE and pglF in the biosynthesis of the trisaccharide structure. Further, we present evidence that pglE, which contains heptanucleotide repeats, is responsible for the phase variation between trisaccharide and disaccharide structures in strain C311♯3 and other strains. We also present evidence that pglG, pglH and pglB2 are potentially phase variable.
Experimental evidence for alternative stable equilibria in a benthic pond food web
Authors: Chase Jonathan M.
Published: July 2003

Both local and initial conditions have been implicated in causing variation in the strengths of predator effects among natural communities. In this study, I performed a controlled mesocosm experiment using two common snails, Physella gyrina and Helisoma trivolvis, and their insect predator, Belostoma flumineum, to explicitly quantify and understand the causes of previously observed variation in food web interactions in natural ecosystems. The results from a controlled mesocosm experiment showed that: (1) at low productivity, snails were dominated by small‐vulnerable species (P. gyrina), predator effects were strong and predator effects caused a trophic cascade extending to producers; (2) at high productivity, snails were dominated by large‐invulnerable species (H. trivolvis), predator effects were weak and there was no trophic cascade to producers; (3) at intermediate productivity, alternative stable equilibria were implicated, such that depending on initial conditions, snails were dominated by either small‐vulnerable or large‐invulnerable species and predator effects were either strong or weak. Thus, this study represents one of the first to quantify how variation in food web structure can result from the local environment, initial conditions and their interaction.
Reciprocal phenotypic plasticity in a predator–prey system: inducible offences against inducible defences?
Authors: Kopp Michael , Tollrian Ralph
Published: July 2003

We describe one of the first examples of reciprocal phenotypic plasticity in a predator–prey system: the interaction between an inducible defence and an inducible offence. When confronted with the predatory ciliate Lembadion bullinum, the hypotrichous ciliate Euplotes octocarinatus develops protective lateral wings, which inhibit ingestion by the predator. We show that L. bullinum reacts to this inducible defence by expressing an inducible offence – a plastic increase in cell size and gape size. This counteraction reduced the effect of the defence, but did not completely neutralize it. Therefore, the defence remained beneficial for E. octocarinatus. From L. bullinum's point of view, the increase in feeding rate because of the offence was not larger than the increase in mean cell volume and apparently, did not increase the predator's fitness. Therefore, the inducible offence of L. bullinum does not seem to be an effective counter‐adaptation to the inducible defence of E. octocarinatus.
Ecological and evolutionary significance of dispersal by freshwater invertebrates
Authors: Bohonak Andrew J. , Jenkins David G.
Published: July 2003

Traditional expectations for how widely and how often freshwater invertebrates disperse differ from empirical data. Freshwater invertebrates have been characterized as frequent, widespread dispersers, particularly those that are transported passively. Our review finds that this characterization may describe thepotentialfor dispersal in some taxa, but it is not an accurate generalization foractualdispersal rates. High variance among habitats and taxonomic groups is a consistent theme. Advances in population genetics may help resolve these issues, but underlying assumptions should be carefully tested. Further, even unbiased estimates of gene flow may not equate with individual movement, because not all dispersers survive and reproduce. Some freshwater invertebrates may exist in classic Levins metapopulations. However, other species fit into a broader metapopulation definition, where temporal dispersal via diapause is functionally equivalent to spatial dispersal. In the latter case, local extinctions and rescue effects may be rare or absent. Finally, limited dispersal rates in many taxa suggest that theories of freshwater community assembly and structure can be made more robust by integrating dispersal and local processes as joint, contingent regulators. Recent research on freshwater invertebrate dispersal has substantially advanced our basic and applied understanding of freshwaters, as well as evolutionary ecology in general.
Does Mother Nature really prefer rare species or are log‐left‐skewed SADs a sampling artefact?
Authors: McGill Brian J.
Published: July 2003

Intensively sampled species abundance distributions (SADs) show left‐skew on a log scale. That is, there are too many rare species to fit a lognormal distribution. I propose that this log‐left‐skew might be a sampling artefact. Monte Carlo simulations show that taking progressively larger samples from a log‐unskewed distribution (such as the lognormal) causes log‐skew to decrease asymptotically (move towards −∞) until it reaches the level of the underlying distribution (zero in this case). In contrast, accumulating certain types of repeated small samples results in a log‐skew that becomes progressively more log‐left‐skewed to a level well beyond the underlying distribution. These repeated samples correspond to samples from the same site over many years or from many sites in 1 year. Data from empirical datasets show that log‐skew generally goes from positive (right‐skewed) to negative (left‐skewed) as the number of temporally or spatially replicated samples increases. This suggests caution when interpreting log‐left‐skew as a pattern that needs biological interpretation.
Biological vs. social, economic and political priority‐setting in conservation
Authors: O'Connor Casey , Marvier Michelle , Kareiva Peter
Published: July 2003

The most influential conservation priority‐setting approaches emphasize biodiversity and threats when deciding where to focus investment. However, socio‐economic and political attributes of nations influence the effectiveness of conservation actions. A combination of biological and sociological variables in the context of a ‘return on investment’ framework for establishing conservation priorities was explored. While there was some overlap between megadiversity nations and return on investment priorities, only a few countries emerged as high priorities irrespective of which factors were included in the analysis. Conversely, some countries that ranked highly as priorities for conservation when focusing solely on biological metrics, did not rank highly when governance, population pressure, economic costs and conservation needs were considered (e.g. Colombia, Ecuador, Indonesia and Venezuela). No priority‐setting scheme is a priori superior to alternative approaches. However, the analyses suggest that attention to governance and return on investment may alter biocentric assessments of ideal conservation investments.
Strontium isotopic characterization of the Palmottu hydrosystem (Finland): water–rock interaction and geochemistry of groundwaters
Authors: Negrel Philippe , Casanova Joël , Blomqvist Runar , Kaija Juha , Frape Shaun
Published: July 2003

The Palmottu hydrosystem is located in a granitic host rock in southern Finland. Along well‐defined pathways in the fractured crystalline rock, strontium isotopes are used to trace the degree of water–rock interaction (WRI) and mixing processes in groundwaters.

The87Sr/86Sr ratios range between 0.716910 and 0.735606 in the surface waters and between 0.719991 and 0.750787 in the groundwaters, but are between 0.720 and 0.735 in most of the samples. Moreover, the results show a lack of correlation between the water chemistries determining the classification into different water‐types (Na–Cl, Na–SO4, etc.) and the results of the strontium (Sr) contents and Sr isotopic ratios. From a WRI standpoint, this implies that the Sr behaviour is independent of the water chemistry; the occurrence of large87Sr/86Sr variations is site specific and mainly dependent on the lithology. A model to determine the87Sr/86Sr ratio of water after interaction with granite was developed. This model is based on the assumption that Sr was derived from three minerals: plagioclase, K‐feldspar and biotite. The results of the calculation indicate that around half of the water analysed within the Palmottu hydrosystem can be explained by the weathering of the granites. However, clearly lower87Sr/86Sr are observed in waters when compared to the calculated87Sr/86Sr and other sources of Sr, with low87Sr/86Sr, rather than the calculated granite–water interaction, which may be suspected.

When comparing the87Sr/86Sr and ion ratios (Ca/Na, Mg/Na, Sr/Na, Cl/Na), the scattering of the data can be explained by the presence of four end‐members: a brine component (low87Sr/86Sr and Ca/Na ratios…), a deep granitic component (high87Sr/86Sr ratios and low Ca/Na ratios…), a subsurface component (intermediate87Sr/86Sr ratios associated with high Ca/Na ratios…) and a surface end‐member:snow and river drainage (low87Sr/86Sr and low Ca/Na ratios…). These extreme end‐members define a series of WRI‐mixing line within a rather complex hydrosystem.
Impaired fast axonal transport in neurons of the sciatic nerves from dystonia musculorum mice
Authors: De Repentigny Yves , Deschênes‐Furry Julie , Jasmin Bernard J. , Kothary Rashmi
Published: July 2003

Dystonia musculorum (dt) mice suffer from a severe sensory neuropathy caused by mutations in the gene encoding the cytoskeletal cross‐linker protein dystonin/bullous pemphigoid antigen 1 (Bpag1). Loss of function of dystonin/Bpag1 within neurons leads to a loss in the maintenance of cytoskeletal organization and to the development of focal axonal swellings prior to death of the neuron. In the present study, we demonstrate that neurons within the sciatic nerves of dt27J mice undergo axonal degeneration as has been previously reported for the dorsal roots. Furthermore, ultrastructural studies reveal a perturbed organization of the neurofilament and microtubule networks within the axons of sciatic nerves in dt27J mice. The disrupted cytoskeletal organization suggested that axonal transport is affected in dt mice. To address this, we assessed fast axonal transport by measuring the rate of accumulation of acetylcholinesterase (AChE) proximal and distal to a surgically introduced ligature on the sciatic nerves of normal and dt27J mice. Our findings demonstrate that axonal transport of AChE in both orthograde and retrograde directions is markedly affected, and allow us to conclude that axonal transport defects do exist in the sciatic nerves of dt27J mice.
Perspectives on the metabolic management of epilepsy through dietary reduction of glucose and elevation of ketone bodies
Authors: Greene Amanda E. , Todorova Mariana T. , Seyfried Thomas N.
Published: July 2003

Brain cells are metabolically flexible because they can derive energy from both glucose and ketone bodies (acetoacetate and β‐hydroxybutyrate). Metabolic control theory applies principles of bioenergetics and genome flexibility to the management of complex phenotypic traits. Epilepsy is a complex brain disorder involving excessive, synchronous, abnormal electrical firing patterns of neurons. We propose that many epilepsies with varied etiologies may ultimately involve disruptions of brain energy homeostasis and are potentially manageable through principles of metabolic control theory. This control involves moderate shifts in the availability of brain energy metabolites (glucose and ketone bodies) that alter energy metabolism through glycolysis and the tricarboxylic acid cycle, respectively. These shifts produce adjustments in gene‐linked metabolic networks that manage or control the seizure disorder despite the continued presence of the inherited or acquired factors responsible for the epilepsy. This hypothesis is supported by information on the management of seizures with diets including fasting, the ketogenic diet and caloric restriction. A better understanding of the compensatory genetic and neurochemical networks of brain energy metabolism may produce novel antiepileptic therapies that are more effective and biologically friendly than those currently available.
Brain levels of CDK5 activator p25 are not increased in Alzheimer's or other neurodegenerative diseases with neurofibrillary tangles
Authors: Tandon Anurag , Yu Haung , Wang Linda , Rogaeva Ekaterina , Sato Christine , Chishti M. Azhar , Kawarai Toshitaka , Hasegawa Hiroshi , Chen Fusheng , Davies Peter , Fraser Paul E. , Westaway David , St George‐Hyslop Peter H.
Published: July 2003

Elevated levels of p25 and constitutive activation of CDK5 have been observed in AD brains. This has led to the hypothesis that increased p25 levels could promote neurofibrillary tangles (NFT) through CDK5‐mediated hyperphosphorylation of tau, the principal component of NFTs. We examined p25 immunoreactivity in brains from sporadic and familial AD cases, as well as other neurologic diseases that exhibit NFT, such as Down's syndrome (DS), Pick's disease (Pick), corticobasal degeneration (CBD), progressive supranuclear palsy (PSP), frontotemporal dementia (FTD). Neither the p25 immunoreactivity nor the p25/p35 ratio was elevated in the AD brains or in the other tauopathies (n = 34) compared with controls (n = 11). Although Aβ peptides have been suggested to activate calpain‐mediated cleavage of p35 to p25 in cultured neurons, p25 levels in brains of TgCRND8 mice, which express high levels of brain Aβ peptides, were similar to those of non‐Tg littermates. Our data suggest that high Aβ levels in brain do not activate p35 proteolysis, and p25 is unlikely to be a causative agent for NFT formation in AD or other tauopathies.
Cytosolic and mitochondrial isoforms of NADP+‐dependent isocitrate dehydrogenases are expressed in cultured rat neurons, astrocytes, oligodendrocytes and microglial cells
Authors: Minich Tobias , Yokota Sadaki , Dringen Ralf
Published: July 2003

NADP+‐dependent isocitrate dehydrogenases (ICDHs) are enzymes that reduce NADP+ to NADPH using isocitrate as electron donor. Cytosolic and mitochondrial isoforms of ICDH have been described. Little is known on the expression of ICDHs in brain cells. We have cloned the rat mitochondrial ICDH (mICDH) in order to obtain the sequence information necessary to study the expression of ICDHs in brain cells by RT‐PCR. The cDNA sequence of rat mICDH was highly homologous to that of mICDH cDNAs from other species. By RT‐PCR the presence of mRNAs for both the cytosolic and the mitochondrial ICDHs was demonstrated for cultured rat neurons, astrocytes, oligodendrocytes and microglia. The expression of both ICDH isoenzymes was confirmed by western blot analysis using ICDH‐isoenzyme specific antibodies as well as by determination of ICDH activities in cytosolic and mitochondrial fractions of the neural cell cultures. In astroglial and microglial cultures, the total ICDH activity was almost equally distributed between cytosolic and mitochondrial fractions. In contrast, in cultures of neurons and oligodendrocytes about 75% of total ICDH activity was present in the cytosolic fractions. Putative functions of ICDHs in cytosol and mitochondria of brain cells are discussed.
Molecular and functional characterization of an octopamine receptor from honeybee (Apis mellifera) brain
Authors: Grohmann Lore , Blenau Wolfgang , Erber Joachim , Ebert Paul R. , Strünker Timo , Baumann Arnd
Published: July 2003

Biogenic amines and their receptors regulate and modulate many physiological and behavioural processes in animals. In vertebrates, octopamine is only found in trace amounts and its function as a true neurotransmitter is unclear. In protostomes, however, octopamine can act as neurotransmitter, neuromodulator and neurohormone. In the honeybee, octopamine acts as a neuromodulator and is involved in learning and memory formation. The identification of potential octopamine receptors is decisive for an understanding of the cellular pathways involved in mediating the effects of octopamine. Here we report the cloning and functional characterization of the first octopamine receptor from the honeybee, Apis mellifera. The gene was isolated from a brain‐specific cDNA library. It encodes a protein most closely related to octopamine receptors from Drosophila melanogaster and Lymnea stagnalis. Signalling properties of the cloned receptor were studied in transiently transfected human embryonic kidney (HEK) 293 cells. Nanomolar to micromolar concentrations of octopamine induced oscillatory increases in the intracellular Ca2+ concentration. In contrast to octopamine, tyramine only elicited Ca2+ responses at micromolar concentrations. The gene is abundantly expressed in many somata of the honeybee brain, suggesting that this octopamine receptor is involved in the processing of sensory inputs, antennal motor outputs and higher‐order brain functions.
Neuronal HuD gene encoding a mRNA stability regulator is transcriptionally repressed by thyroid hormone
Authors: Cuadrado Ana , Navarro‐Yubero Cristina , Furneaux Henry , Muñoz Alberto
Published: July 2003

Many genes governed by thyroid hormone (T3) lack binding sites for its receptor (TR) and are thought to be post‐transcriptionally regulated by T3. Here we demonstrate that the HuD gene, which encodes a neurone‐specific protein that binds to mRNA and modulates its stability, is regulated by T3. HuD RNA and protein expression were strongly up‐regulated in specific areas of the hypothyroid rat brain, and reduced by T3 in rat PC12 and mouse N2a cells containing appropriate TR levels. Furthermore, T3 inhibited the transcription of HuD in run‐on assays. Finally, HuD protein bound with high affinity to two sequences in acetylcholinesterase mRNA, and ectopic HuD expression increased its abundance in N2a cells. This is the first report of a gene encoding an mRNA stability regulator that is under T3 control. The results suggest that HuD may mediate some T3 effects by altering the half‐life of mRNAs for acetylcholinesterase and other genes.
Hyperphosphorylation and aggregation of tau in mice expressing normal human tau isoforms
Authors: Andorfer Cathy , Kress Yvonne , Espinoza Marisol , De Silva Rohan , Tucker Kerry L. , Barde Yves‐Alain , Duff Karen , Davies Peter
Published: July 2003

Neurofibrillary tangles are composed of insoluble aggregates of the microtubule‐associated protein tau. In Alzheimer's disease the accumulation of neurofibrillary tangles occurs in the absence of tau mutations. Here we present mice that develop pathology from non‐mutant human tau, in the absence of other exogenous factors, including β‐amyloid. The pathology in these mice is Alzheimer‐like, with hyperphosphorylated tau accumulating as aggregated paired helical filaments. This pathologic tau accumulates in the cell bodies and dendrites of neurons in a spatiotemporally relevant distribution.
Relationship between myelin production and dopamine synthesis in the PKU mouse brain
Authors: Joseph Bernadin , Dyer Charissa A.
Published: July 2003

Phenylketonuria is caused by specific mutations in the phenylalanine hydroxylase gene and is characterized by elevated blood phenylalanine levels, hypomyelination in forebrain structures, reduced dopamine levels, and cognitive difficulties. To determine whether brain tyrosine levels and/or myelination play a role in the up‐regulation of dopamine, phenylketonuric mice were placed on a low phenylalanine diet for 4 weeks and as blood phenylalanine levels dropped to normal, the relationships between phenylalanine, tyrosine, dopamine, myelin proteins, and axonal proteins in frontal cortex and striatum were determined using gas chromatography mass spectrometry, histology, and western blotting techniques. Blood phenylalanine rapidly decreased from an eight‐fold elevation to near control levels, and blood tyrosine gradually rose from about 50% to near normal values. In frontal cortex and striatum, phenylalanine levels dropped to 2‐ and 1.5‐fold elevations above control, respectively, and tyrosine levels increased but remained less than 70% of control in both structures. In frontal cortex, increases in dopamine and myelin basic protein occurred in a similar biphasic pattern, reaching near normal levels by week 4. In striatum, dopamine and MBP dramatically increased to near normal levels in the first week. Myelination was confirmed histologically and by western blot quantification of phosphorylated neurofilaments. In summary, our results showed: (i) an increase in dopamine despite low brain tyrosine levels and (ii) similar recovery patterns for myelination and dopamine. Since myelin/axonal interactions trigger signaling pathways that result in axonal maturation, we speculate that this interaction also may trigger signals that up‐regulate neurotransmitter synthesis.
Death and Taxes: the Case of the Depletion of Pearl Oyster Beds in Sixteenth‐Century Venezuela
Authors: Romero Aldemaro
Published: July 2003

Abstract: Interdisciplinary approaches have been used not only to interpret past patterns of natural resource utilization but also to provide useful tools for conservation biology and resource management. I report here the depletion of the pearl oyster (  Pinctada imbricata ) beds off the coast of Cubagua, Venezuela, in the sixteenth century and the replacement of the oyster by the turkey‐wing mussel ( Arca zebra ). I used historical tax data to conclude that the rapid depletion of this resource was the result not only of overexploitation in a short period of time but also of the ecology of the place used by humans to carry out such activity. Under conditions of ecological stress generated by overexpoloitation, the turkey‐wing mussel outcompeted the pearl oyster, thus preventing its recovery. Finally, I propose that the exploitation of the pearl oyster beds directly influenced the demographic, social, and cultural conditions of the indigenous human populations in the Caribbean and, to a certain extent, in Africa.
Science and Management in a Conservation Crisis: a Case Study with Rhinoceros
Authors: Linklater Wayne L.
Published: July 2003

Abstract:I suggest that a conservation crisis is a predictable sequence of five stages: population decline, crisis management, stabilization, precarious recovery, and sustained recovery. Each stage has different research priorities, constraints, and opportunities that cause a mismatch between conservation needs and research practice. The conservation crisis over the rhinoceros was characterized by rapid decline due to illegal hunting and trade in rhinoceros horn. I conducted a literature review ( 1980–2000 ) on rhinoceros during this crisis to illustrate the five stages. I also examined the bibliographies of the African and Asian conservation action plans to illustrate literature availability and use. I sought to determine whether a retrospective understanding of trends in the scientific literature during conservation crises could help us better target research efforts and meet the challenge of conserving rare species. The scientific literature on rhinoceros increased during the crisis but became dominated by ex situ laboratory‐based studies, whereas the number of in situ ecological studies remained low, although the conservation action plans identified in situ and ecological studies as conservation priorities. Moreover, the bibliographies of the conservation action plans were dominated by unpublished material ( 56% ), and only 25% of citations came from scientific journals, although peer review and critique contributes to maintaining and improving the quality of conservation science. Thus, I suggest that research matched conservation needs poorly. However, the predictability of the crisis sequence means that it should be possible to preempt conservation research needs. The effect of a conservation crisis on research may be ameliorated by abandoning the dualism of applied and basic research and better targeting research effort by identifying when research is relatively unimportant, exploiting opportunities for science by management, establishing collaborative publishing relationships between managers and researchers, and prioritizing in situ ecological research.
Reliability of Relative Predictions in Population Viability Analysis
Authors: McCarthy Michael A. , Andelman Sandy J. , Possingham Hugh P.
Published: July 2003

Abstract: Despite numerous claims that population viability analysis ( PVA ) makes reliable predictions of the relative risks of extinction, there is little evidence to support this assertion. To assess the veracity of the claim, we investigated uncertainty in the relative predictions of a PVA model with simulation experiments. We used a stochastic Ricker model to investigate the reliability of predicted changes in risks of decline in response to changes in parameters, the reliability of ranking species in terms of their relative threat, and the reliability of choosing the better of two management decisions. The predicted changes in risks of decline within 100 years were more reliable than absolute predictions. We made useful predictions of relative risks using only 10 years of data. Across 160 different parameter combinations, the rank correlation between the true risks of extinction within 100 years and predicted risks was 0.59 with 10 years of data, increasing to 0.89 with 100 years of data. We identified the better of two management strategies 67–74% of the time using 10 years of data, increasing to 92–93% of the time with 100 years of data. Our results demonstrate that, despite considerable uncertainty in the predicted risks of decline, PVA may reliably contribute to the management of threatened species.
Translocation Causes Extinction of a Local Population of the Freshwater Shrimp Paratya australiensis
Authors: Hughes Jane , Goudkamp Katrina , Hurwood David , Hancock Martyn , Bunn Stuart
Published: July 2003

Abstract: In 1993, as part of another study, we translocated freshwater shrimp (  Paratya australiensis ) between pools from two different subcatchments within the same drainage system in southeast Queensland, Australia. Subsequent analysis of the mitochondrial COI locus revealed that populations in the two subcatchments represented monophyletic lineages that were 6% divergent. Thus, we decided to determine the effects of the translocation on resident populations. After only 7 years, representing seven generations, the resident genotype was extinct at one of the sites. Evidence from analysis of nuclear genes ( allozymes ) and mitochondrial genes ( COI ) suggests that this extreme result may be explained by a mating preference of all females ( resident and translocated ) for translocated males and a low viability of crosses between resident females and translocated males. There is no obvious morphological or behavioral reason for a mating preference. The results of our study provide evidence that deliberate translocations and interbasin water transfers should be treated with caution.
Spatial Variation in Species Diversity and Composition of Forest Lepidoptera in Eastern Deciduous Forests of North America
Authors: Summerville Keith S. , Boulware Michael J. , Veech Joseph A. , Crist Thomas O.
Published: July 2003

Abstract: The primary emphasis of conservation biology has moved away from attempting to manage single species within a given habitat to the preservation of entire communities within ecoregions, requiring that greater attention be paid to how biodiversity and species composition vary across spatial scales. Using a nested sampling design, we examined spatial variation in the biodiversity of forest Lepidoptera across three hierarchical levels: 20 forest stands, five sites, and three ecoregions. We used blacklight traps to sample the moth communities of each forest stand every week in June and August of 2000. Lepidopteran community composition was most significantly influenced by ecoregional differences, whereas patterns of α and β diversity across scales differed depending on how diversity was measured. Diversity partitioning models demonstrated that turnover in species richness occurred equally across all spatial scales because numerically rare species were continually encountered. In contrast, within‐stand effects disproportionately influenced Simpson and Shannon diversity ( relative to outcomes from randomization tests ), suggesting that local factors determined species dominance. Because most Lepidoptera in forests appear to be rare ( >50% ), it will be impossible for conservation biologists to design management plans to account for every species. We suggest that a more meaningful strategy would be to identify species that attain a reasonable abundance within a community ( 5–10% of all the individuals in a sample ) and that are unique to particular spatial levels. This strategy should produce two desirable outcomes: the conservation of species that render ecoregions distinct and the maintenance of functionally dominant species within forests.
Recovery of Native Earthworms in Abandoned Tropical Pastures
Authors: Leon Yaniria Sanchez‐De , Zou Xiaoming , Borges Sonia , Ruan Honghua
Published: July 2003

Abstract:Regeneration of secondary forests is recognized as an important means for the recovery of native species biodiversity in human‐disturbed tropical lands. Native earthworms are often replaced with exotic species after deforestation. We studied changes in earthworm diversity and community structure along a chronosequence of abandoned tropical pastures in the Cayey Mountains of Puerto Rico. This chronosequence consisted of active pastures, young secondary forests 25–40 years old, and mature secondary forests>77 years old. Earthworm diversity increased along successional stages. The exotic soil‐feeding earthwormPontoscolex corethrurusdominated the pastures and young secondary forests. Five native earthworm species (  litter feedersBorgesia sedecimsetae,Estherellasp.,Onychochaeta borincana,Neotrigaster rufa, andTrigaster longissimus ) were found in the mature forests, together withP. corethrurus. Earthworm density was highest in the active pastures ( 273 individuals/m2 ), decreased as forest regeneration proceeded, and was lowest in the mature forests ( 88 individuals/m2 ). Our results suggest that regeneration of mature secondary forests, and the consequent increase in litter biomass on the forest floor, can promote the recovery of earthworm diversity and native species of earthworms in old tropical pastures.
Invasion of Exotic Plant Species in Tallgrass Prairie Fragments
Authors: Cully Anne C. , Cully Jack F. , Hiebert Ronald D.
Published: July 2003

Abstract: The tallgrass prairie is one of the most severely affected ecosystems in North America. As a result of extensive conversion to agriculture during the last century, as little as 1% of the original tallgrass prairie remains. The remaining fragments of tallgrass prairie communities have conservation significance, but questions remain about their viability and importance to conservation. We investigated the effects of fragment size, native plant species diversity, and location on invasion by exotic plant species at 25 tallgrass prairie sites in central North America at various geographic scales. We used exotic species richness and relative cover as measures of invasion. Exotic species richness and cover were not related to area for all sites considered together. There were no significant relationships between native species richness and exotic species richness at the cluster and regional scale or for all sites considered together. At the local scale, exotic species richness was positively related to native species richness at four sites and negatively related at one. The 10 most frequently occurring and abundant exotic plant species in the prairie fragments were cool‐season, or C3, species, in contrast to the native plant community, which was dominated by warm‐season, or C4, species. This suggests that timing is important to the success of exotic species in the tallgrass prairie. Our study indicates that some small fragments of tallgrass prairie are relatively intact and should not be overlooked as long‐term refuges for prairie species, sources of genetic variability, and material for restoration.
Comparative Permeability of Roads, Rivers, and Meadows to Songbirds in Banff National Park
Authors: Clair Colleen Cassady St.
Published: July 2003

Abstract:Roads exert a variety of negative effects on wildlife and one of the most severe may be that they form barriers to animal movement. However, the role of roads as barriers has seldom been compared to that of natural barriers. I examined the permeability of roads, rivers, and meadows to songbirds in Banff National Park, Alberta, Canada, where a four‐lane highway dissects a wide montane valley. An audio recording of a chickadee (  Poecile atricapillus ) mobbing call was played to lure birds to travel either parallel or perpendicular to the three barrier types over a range of distances. Relative to parallel trials, forest‐dependent birds were reluctant to cross rivers but not roads or meadows, and they crossed barriers less often when the barriers were noisy. Across all gap and barrier combinations, responses declined as trial distance increased, and kinglets were less likely to respond than other families, which included chickadees, nuthatches, warblers, and corvids. The responses of sparrows and thrushes—both forest generalists—showed a weak interaction between barrier type and family, indicating that robins were slightly less likely to respond to trials associated with meadows, and sparrows were less likely to respond in association with rivers. These associations occurred irrespective of gap configuration. Together, these results suggest that the response to barriers by montane birds is strongly dependent on their degree of forest dependence. The surprising result that forest birds were less likely to cross rivers than either roads or meadows may stem from evolutionary history and suggests that birds do not perceive the risk of mortality posed by road traffic.
European Starlings and Their Effect on Native Cavity‐Nesting Birds
Authors: Koenig Walter D.
Published: July 2003

Abstract: European Starlings ( Sturnus vulgaris ) were introduced to New York City in 1890 and have since become one of North America's most common species. Starlings are aggressive competitors and commonly usurp cavities of other hole‐nesting species. These characters make it a clear choice for a species whose invasion is likely to have significantly affected native cavity‐nesting birds. Using Christmas Bird Counts and Breeding Bird Surveys, I compared the mean densities of 27 native cavity‐nesting species before and after invasion of sites by starlings. Contrary to expectations, only 10 of the species exhibited significant effects potentially attributable to starlings, and only half of these were in part negative. However, in 2 of the 5 species that showed negative effects, evidence for a decline in one analysis was countered by an increase in the other, whereas in 2 others declines were likely due to factors other than starling competition. Only sapsuckers (  Sphyrapicus spp. ) exhibited declines potentially attributable to starlings that were not countered by other data. Although declines may still occur if starlings continue to increase, the results of this study fail to support the hypothesis that starlings have had a severe impact on populations of native birds. These results highlight the difficulties of predicting the impacts of invasive species. Native hole‐nesting birds have thus far apparently held their own against the starling invasion, despite the latter's abundance and aggressive usurpation of often limited cavities.
Nest Predation and Population Declines in Illinois Songbirds: a Case for Mesopredator Effects
Authors: Schmidt Kenneth A.
Published: July 2003

Abstract: Mesopredator release has typically been examined at small spatial scales; however, processes such as habitat fragmentation, suppression of top predators, and changes in land use that lead to higher mesopredator densities typically occur at large spatial scales. In Illinois, raccoon (   Procyon lotor ) numbers have increased since the early 1980s, with unknown consequences for breeding songbirds. I examined population trends between 1979 and 2001 for songbirds inhabiting woodland and scrub‐successional habitats within Illinois by using data from the North American Breeding Bird Survey ( BBS ). I assigned species a priori into two groups: ( 1 ) raccoon‐vulnerable species that nest low and thus are highly vulnerable to nest predation by raccoons and ( 2 ) raccoon‐invulnerable species that nest high and largely escape nest predation by raccoons. The mean number of raccoon‐vulnerable species per Illinois BBS route declined by approximately 10%, whereas the number of raccoon‐invulnerable species increased approximately 15% through the early 1990s. Population trends of the two groups also diverged. Raccoon‐vulnerable species had predominantly negative population trends from 1980 to 2001, whereas raccoon‐invulnerable species show roughly equal numbers of positive and negative trends. In contrast, population trends prior to 1980 did not show this divergence. A survey of studies from Illinois that report nesting success connects these divergent patterns between the two groups to substantially higher nest‐predation rates for raccoon‐vulnerable species. Taken together, results of these studies and mine suggest that large‐scale changes in the abundance of raccoons have had demonstrable consequences for songbird populations and communities in Illinois.
As Unconscious and Gay as a Trout in a Stream?: Turning the Trope of the Australian Girl
Authors: Dalziell Tanya
Published: July 2003

The instability of colonial representational economies, identities and tropes is the subject of analysis in this paper. I take as my starting point the anxieties that were generated during the late 19th century in relation to what I nominate the fictitiousness of settler subjects in colonial Australia. In order to examine these historical concerns and their explicitly gendered representations, I consider in detail one text, Rosa Campbell Praed's Fugitive Anne: A Romance of the Unexplored Bush (1902). This text was published in 1902 and was one of a number of romance novels this author produced for readerships in both colonial Australia and England. This adventure romance features the trope of the Australian Girl and also engages in varying degrees with discourses of colonial ethnography that, to my knowledge, have not been examined in relation to the ideological production and effects of this figure.
‘Infidelity to an Impossible Task’: Postmodernism, Feminism and Lyn Hejinian's ‘My Life’
Authors: Marsh Nicky
Published: July 2003

This paper locates the work and critical reception of the experimental poet Lyn Hejinian within the emerging debates of ‘third-wave’ feminist critique. It centrally argues that Hejinian's writing at once illuminates and undermines the apparent tensions between a feminist and an anti-foundationalist critical position. It specifically focuses on Hejinian's use of autobiography, as at once gesturing to the limitations of the theoretically naive self-knowing subject, steeped in the discredited assumptions of modernity, and the continuing cultural validity of and desire for narrative, identification, self-expression and referentiality. The paper argues that Hejinian's writing makes sense of this equivocation, not through its use of feminized tropes assumed to subvert the linear assumptions of the genre and render the reader ‘active’, but through an attention to the ironical complexities of her own cultural positioning. Hejinian's writing demonstrates how the representation of the postmodern feminist subject involves an attention to authoriality, to the possibilities of textual experimentation and to the cultural sites that legitimize the production of meaning for these things. Hejinian demonstrates not simply that feminism can reconcile a need for agency with a critique of agency, and that such an act needs to consider its collective implications, but that these kinds of claims actually require an engagement with the varied contexts that continue to make feminist's attention to literature meaningful.
Three-dimensional instability of isolated vortices
Authors: Gallaire F. , Chomaz J.-M.
Published: July 2003

We study the three-dimensional stability of the family of vortices introduced by Carton and McWilliams [Mesoscale/Synoptic Coherent Structures in Geophysical Turbulence, edited by Nikhoul and Jamart (Elsevier, New York, 1989)] describing isolated vortices. For these vortices, the circulation vanishes outside their core over a distance depending on a single parameter, the steepness α. We proceed to the direct numerical simulation of the linear impulse response to obtain both temporal and spatio-temporal instability results. In the temporal instability framework, growth rates are calculated as a function of the axial wavenumber k and the azimuthal wavenumber m. The stability analysis is performed at a Reynolds number of Re=667. It is shown that the most unstable mode is the axisymmetric mode m=0, regardless of the steepness parameter in the investigated range. When the steepness α is increased the band of unstable azimuthal modes widens, i.e., larger m are destabilized. The study of the spatio-temporal spreading of the wave packet shows that the m=2 mode is always the fastest traveling mode, for all studied values of the steepness parameter.
Linear compensator control of a pointsource induced perturbation in a Falkner–Skan–Cooke boundary layer
Authors: Högberg Markus , Chevalier Mattias , Henningson Dan S.
Published: July 2003

We focus on the problem of controlling pointsource induced perturbations on an infinite swept wing using linear control theory. Based on wall measurements in a spatial simulation of localized disturbances in Falkner–Skan–Cooke boundary layers, an extended Kalman filter is used to estimate the full three-dimensional wave packet. The estimated field is in turn used to calculate a feedback control which changes the growth of the disturbance into decay. This is the first time that optimal control and estimation concepts are successfully applied to construct a dynamic output feedback compensator which is used to control disturbances in spatially developing boundary layers.
Velocity-scalar filtered density function for large eddy simulation of turbulent flows
Authors: Sheikhi M. R. H. , Drozda T. G. , Givi P. , Pope S. B.
Published: July 2003

A methodology termed the “velocity-scalar filtered density function” (VSFDF) is developed and implemented for large eddy simulation (LES) of turbulent flows. In this methodology, the effects of the unresolved subgrid scales (SGS) are taken into account by considering the joint probability density function (PDF) of the velocity and scalar fields. An exact transport equation is derived for the VSFDF in which the effects of the SGS convection and chemical reaction are closed. The unclosed terms in this equation are modeled in a fashion similar to that typically used in Reynolds-averaged simulation procedures. A system of stochastic differential equations (SDEs) which yields statistically equivalent results to the modeled VSFDF transport equation is constructed. These SDEs are solved numerically by a Lagrangian Monte Carlo procedure in which the Itô–Gikhman character of the SDEs is preserved. The consistency of the proposed SDEs and the convergence of the Monte Carlo solution are assessed by comparison with results obtained by a finite difference LES procedure in which the corresponding transport equations for the first two SGS moments are solved. The VSFDF results are compared with those obtained by the Smagorinsky model, and all the results are assessed via comparison with data obtained by direct numerical simulation of a temporally developing mixing layer involving transport of a passive scalar. It is shown that the values of both the SGS and the resolved components of all second order moments including the scalar fluxes are predicted well by VSFDF. The sensitivity of the calculations to the model’s (empirical) constants are assessed and it is shown that the magnitudes of these constants are in the same range as those employed in PDF methods.