bluuebunny/crossref_metadata_2025 huggingface dataset:
Humoral immune response in relation to senescence, sex and sexual ornamentation in the barn swallow (Hirundo rustica)
Authors: Saino N. , Ferrari R. P. , Romano M. , Rubolini D. , Møller A. P.
Published: October 2003

Performance of animals may decline with age. The effects of senescence, however, may differ between the sexes because of differences in physiology and behaviour. Acquired immunity provides hosts with efficient mechanisms of anti-parasite defence, but the effect of senescence on immunocompetence has never been studied in natural populations. In the barn swallow (Hirundo rustica), primary antibody response to an antigen during one breeding season declined with age in females, while secondary response during the following breeding season declined with age in both sexes. Parasite-mediated sexual selection theory posits that male secondary sexual characters reveal resistance to parasites. Males with large tail ornaments had stronger primary response, retained larger antibody levels until the following year, but did not differ in secondary response compared with short-tailed males, as predicted if ornamentation reflects resistance to parasites. This is the first study showing that immunocompetence declines with age in any vertebrate under natural conditions.
Evidence for bimodal hybrid zones between two species of char (Pisces: Salvelinus) in northwestern North America
Authors: Redenbach Z. , Taylor E. B.
Published: October 2003

Dolly Varden (Salvelinus malma, Pisces: Salmonidae) and bull trout (Salvelinus confluentus) have widely overlapping, but largely parapatric ranges in watersheds in northwestern North America from Washington State to northern British Columbia. Genetic analysis of natural populations using diagnostic molecular markers revealed widespread local sympatry and hybridization with hybrids comprising 0–25% of the local samples. In a detailed analysis of hybridization using four nuclear DNA markers and mitochondrial DNA within the Thutade Lake watershed, northcentral British Columbia, hybrid genotypes constituted up to 9% of the population of juvenile char. There were significant deviations from Hardy–Weinberg, gametic, and cytonuclear equilibria, and local samples showed bimodal frequency distributions of genotypes. Pure parental and inferred backcross genotypes were most common, and F1 and Fn hybrids were comparatively rare. Interspecific hybridization was asymmetrical, with most F1 hybrids (five of six) bearing S. confluentus mtDNA. The introgression of nuclear and mitochondrial alleles was asymmetrical, with S. confluentus mtDNA and Growth Hormone 2 introgressing into S. malma significantly more than either introgression of the three other nuclear loci, or introgression of S. malma alleles into S. confluentus. Substantial prezygotic isolation between the species likely depends on the large body size difference between them in sympatry: S. malma have small bodies and a stream resident life history (12–21 cm adult fork length at maturity), while S. confluentus are larger and adfluvial, i.e., they migrate to Thutade Lake where they grow to maturity before returning to tributary streams to spawn (40–90 cm at maturity). These traits may limit interspecific pairings because of size assortative pairing and size-dependent reproductive habitat use.
Sex choice in plants: facultative adjustment of the sex ratio in the perennial herb Begonia gracilis
Authors: López S. , Domínguez C. A.
Published: October 2003

Sex allocation theory predicts that reproducing individuals will increase their fitness by facultatively adjusting their relative investment towards the rarer sex in response to population shifts in operational sex ratio (OSR). The evolution of facultative manipulation of sex ratio depends on the ability of the parents to track the conditions favouring skewed sex allocation and on the mechanism controlling sex allocation. In animals, which have well-developed sensorial mechanisms, facultative adjustment of sex ratios has been demonstrated on many occasions. In this paper, we show that plants have mechanisms that allow them to evaluate the population OSR. We simulated three different conditions of population OSR by manipulating the amount of pollen received by the female flowers of a monoecious herb, and examined the effect of this treatment on the allocation to male vs. female flowers. A shortage of pollen on the stigmas resulted in a more male-skewed sex allocation, whereas plants that experienced a relatively pollen rich environment tended to produce a more female-skewed sex allocation pattern. Our results for Begonia gracilis demonstrate that the individuals of this species are able to respond to the levels of pollination intensity experienced by their female flowers and adjust their patterns of sex allocation in accordance to the expectations of sex allocation theory.
Flexible mating: cross-pollination affects sex-expression in a marine clonal plant
Authors: Hämmerli A. , Reusch T. B. H.
Published: October 2003

Many functionally hermaphroditic plants have evolved mechanisms to reduce interference between the sex functions and to optimize reproductive output. In addition to physical mechanisms such as the spatial (herkogamy) and temporal (dichogamy) separation of male and female functions, plasticity in sex expression by means of mate-recognition (flexible mating) could be important in plants with variable access to cross-pollen. This applies particularly to clonal plants because of their modular growth form. We experimentally tested for the effects of pollen source and vegetative neighbourhood on instantaneous sex ratio and seed production in the self-compatible clonal marine angiosperm Zostera marina L. To this end, we exposed the (monoecious) flowering shoots to self and cross-pollen and to neighbourhoods of their own and a mix of foreign vegetative shoots. Flowering shoots that had been exposed to cross-pollen showed (1) a significantly lower female/male ratio at peak flowering, evidence for mate-recognition, and (2) a significantly higher seed set by the end of the season. Both effects were independent of the genetic composition of their vegetative neighbourhood. The results suggest that Z. marina maintains a cryptic self-incompatibility system not previously described for angiosperms with sub-aqueous pollination. In Z. marina, and possibly other self-compatible clonal plant species, mate-recognition could be a means of increasing the out-crossing probability for flowering shoots with central positions within their clone.
Environment-dependent inbreeding depression in a hermaphroditic freshwater snail
Authors: Henry P.-Y. , Pradel R. , Jarne P.
Published: October 2003

Inbreeding depression was simultaneously studied under contrasted environments, laboratory and natural conditions, using individuals originating from 14 families of the freshwater snail Physa acuta. Both survival and growth of juveniles showed inbreeding depression under laboratory conditions. The same fitness components were monitored with mature snails either kept under laboratory conditions or released at a natural site and analysed using capture-mark-recapture models. Genetic composition of both samples was similar. Inbreeding depression on survival was highest in the laboratory while strong outbreeding depression was revealed in the field. Thus inbreeding depression may not be always higher under natural conditions, at the opposite of what is commonly assumed. We suggest that inbreeding depression is dependent on metabolic requirements imposed by the environment. Other evidences showing that inbreeding depression is environment-dependent are reviewed. We conclude that genetic models should include both genetic and environmental variance in inbreeding depression for studying mating system evolution.
Diagnostic testing and discharge coding for whooping cough in a children's hospital
Authors: Bonacruz‐Kazzi G , McIntyre P , Hanlon M , Menzies R
Published: October 2003

Objective:  To evaluate the diagnostic pathways for whooping cough in a large urban paediatric hospital to inform assessment of the relative merits of notification and hospitalization data for measuring pertussis disease burden in Australian children.

Methods:  All laboratory requests for Bordetella pertussis (BP) culture or serology between 30 June 1997 and 30 June 1999 were reviewed and cross‐checked against discharge diagnoses with International Classification of Disease (ICD) codes A37.0, 033.0 (whooping cough due to BP) or 37.9, 033.9 (whooping cough due to unspecified organisms). Culture‐positive (CP) cases were defined as a positive culture or polymerase chain reaction for BP. Culture‐negative (CN) cases either fulfilled the current Australian clinical case definition (≥14 days of cough with one or more of paroxysms, whoop, post‐tussive vomiting), or had a cough illness with either positive BP serology or documented contact with an individual coughing for >14 days. In infants <6‐months‐old, a coughing illness with apnoea and negative investigations for other causes was also accepted. Culture positive and CN cases were cross‐referenced with notification data.

Results:  During the study period, laboratory tests for BP were performed in 677 children, of whom 230 were hospitalized and 71 (31%) had an eligible ICD code at discharge; 29 were CP, 40 CN, and two (3%) were misclassified. A further 14 CP children were not admitted. Although 61 hospitalized cases (88%) fulfilled notification criteria, including 32 (80%) of CN cases, only 26 (90%) of CP and eight (20%) of CN cases were notified.

Conclusions:  Notifications substantially under‐enumerate hospitalized infant cases, especially those without positive laboratory tests. Hospital discharge data add significantly to surveillance for pertussis, particularly in infancy where most severe cases occur.
Petrositis and cerebellar abscess complicating chronic otitis media
Authors: Trimis G , Mostrou G , Lourida A , Prodromou F , Syriopoulou V , Theodoridou M
Published: October 2003

Abstract:  A 12‐year‐old girl with chronic otitis media complicated by petrositis and cerebellar abscess is presented. Early surgical intervention, in combination with broad‐spectrum antibiotics, provided a good outcome. Life‐threatening complications of otitis media, although rare, still occur in developed countries.
Systemic aspects of interstitial cystitis, immunology and linkage with autoimmune disorders
Authors: VAN DE MERWE JOOP P. , YAMADA TETSUO , SAKAMOTO YASUKI
Published: October 2003

Abstract It is recognized that interstitial cystitis (IC) is often associated with a number of diseases such as allergies, irritable bowel syndrome, fibromyalgia, inflammatory bowel disease (Crohn's disease and ulcerative colitis), systemic lupus erythematosus, and Sjögren's syndrome.

The prevalence of allergies in IC is reported to be between 40 and 80% of patients. The background of the association is not known and does not seem to be the result of a generalized allergic constitution. Some report that treatment of allergy sometimes has a beneficial effect on bladder symptoms.

An increased expression of certain growth factors (PD‐ECGF, FGF, and VEGF) has been found in the bladder of IC patients. In addition, the expression of CD44 was significantly higher in ulcer type IC than in non‐ulcer type. In general, these growth factors are soluble and diffusible under normal conditions but proteoglycans such as CD44 could bind to these growth factors. This may promote the accumulation of growth factors at the sites of inflammation. CD44 expression in ulcer type IC could explain the prolonged and stronger expression of GAG‐binding growth factors that promote inflammation.

In the Rotterdam study, a strong association between IC and Sjögren's syndrome is recognized. In this study, 28% of IC patients have definite or probable Sjögren's syndrome. This association is much stronger than is generally recognized. This could be due to difficulties in diagnosing Sjögren's syndrome since a diagnosis usually requires a high index of suspicion.
The basics behind bladder pain: A review of data on lower urinary tract sensations
Authors: WYNDAELE J. J. , DE WACHTER STEFAN
Published: October 2003

Abstract Interstitial cystitis is a syndrome consisting of frequency, urgency, and bladder pain that increases with bladder filling and improves temporarily after voiding.

The exact cause or causes are not as yet fully understood. This leads to uncertainty in diagnosis and treatment. There is need for more knowledge, and to acquire this for more research.

The fact that the condition causes pain, a pathologic stimulation of sensory fibres, makes understanding the basic sensory mechanisms in the lower urinary tract in normal and pathologic conditions mandatory.

In this article we review the data on bladder sensation from the last 25 years and the possible relation with painful bladder syndrome.
Interstitial cystitis, gynecologic pelvic pain, prostatitis, and their epidemiology
Authors: DIOKNO ANANIAS C. , HOMMA YUKIO , SEKIGUCHI YUKI , SUZUKI YASUYUKI
Published: October 2003

Abstract Aim: To determine a uniform definition of interstitial cystitis (IC) and to develop a strategy on how to study its epidemiology.

Methods: Initially, the committee reviewed the literature regarding the definition of IC currently being used and information regarding its epidemiology. The committee held three 1‐hour hearings and discussions on the opinions of invited IC specialists. The issues were presented and discussed. Consensus was sought when possible. The committee members met and summarized the gist of the three sessions.

Results: A consensus emerged as to what constitutes IC. Interstitial cystitis must have the elements of chronic pelvic pain and urinary frequency and/or urgency. It was also the recommendation that the term IC be retained followed by chronic pelvic pain syndrome represented by the acronym IC/CPPS. A strategy on the epidemiologic study of IC/CPPS was also recommended.

Conclusions: A consensus from this workshop has emerged in terms of defining the component of IC, the preferred terminology, and the strategy to study its epidemiology.
Prevention of RCF damage in curved track through development of the INFRA‐STAR two‐material rail
Authors: HIENSCH E. J. M. , FRANKLIN F. J. , NIELSEN J. C. O. , RINGSBERG J. W. , WEEDA G. J. , KAPOOR A. , JOSEFSON B. L.
Published: October 2003

Results from the European 5th frame research project ‘INFRA‐STAR’ are presented. The goal of the project is to prevent rolling contact fatigue (RCF) and to reduce squeal noise in curves by applying an additional surface layer material on the top of the railhead, resulting in a two‐material rail. In INFRA‐STAR, a dynamic train–track interaction model is used to provide the contact forces. Wheel‐rail profiles, wheel‐rail friction, vehicle data, track data and operating conditions are included to calculate the wheel‐rail contact forces and spin moments, contact positions and load distributions in the contact patch. The contact pressure, friction coefficient, coating thickness, material properties of the coating and the rail material are used in finite element calculations and shakedown theory to calculate shakedown limits, which are then used to predict the RCF performance of the system. The paper details the work on theoretical modelling, twin disc testing, metallurgical research and field testing completed to date (August 2002, the project just passed midterm). The development of the surface layer application methods that are used, and the further objectives of the INFRA‐STAR project, are discussed.
Rail integrity management by means of ultrasonic testing
Authors: MARAIS J. J. , MISTRY K. C.
Published: October 2003

This paper discusses the monitoring of the condition of the OREX ore export line rails in South Africa. Ultrasonic testing is widely used to monitor defect development and growth as well as to plan and manage programs to ensure a high level of rail integrity. An overview of the performance and history of the line is given in terms of rail defect levels and derailments due to rail failures in relation to traffic volumes. Some of the inherent characteristics of the rails are discussed and related to the defect development. From the available data it is clear that the rails are degrading in a ‘wear‐out mode’, with increasing defect rates. The use of high technology ultrasonic testing equipment has enhanced the level of knowledge of the condition of the rails tremendously and has led to programs that actually improved the overall condition of the line and eliminated derailments due to rail defects.
The blending of theory and practice in modern rail grinding
Authors: MAGEL E. , RONEY M. , KALOUSEK J. , SROBA P.
Published: October 2003

Modern rail grinding practices have developed largely through a combination of field experience and intuitive speculation. Many theories related to crack initiation and growth have been proposed through the decades, and those concepts have been cleverly extended to the field of rail grinding to form the basis of the practice known as ‘preventive grinding’. But only recently have practical models emerged from the laboratory and theoretical environment and been applied to the process of rail grinding. These models are substantiating the past practices and providing a pathway towards the development of improved predictive tools for rail fatigue and profile deterioration.
Development of bainitic rail steels with potential resistance to rolling contact fatigue
Authors: SAWLEY K. , KRISTAN J.
Published: October 2003

Rails are a major capital and maintenance cost for railways in North America. While manufacturers produce clean steels with high quality, most rails made today retain the basic carbon–manganese chemistry of traditional pearlitic rails. This paper describes the development of a bainitic rail steel with potential additional resistance to rolling contact fatigue damage. It is shown that rails can be produced in bainitic steel without the need for complex heat treatments after rolling, and that bainitic rails can have higher hardness and fracture toughness than pearlitic rails. Although small‐ and full‐scale tests indicate that the wear performance of bainitic steel depends considerably on test conditions, the indication is that bainitic steel rails can have significantly better rolling contact fatigue performance compared to pearlitic rails. Reasons for the superior fatigue performance are not fully understood, although a number of hypotheses exist. A conclusion is that continued research would be useful to understand quantitatively the physics and metallurgy of wheel/rail contact.
Shakedown limit of rail surfaces including material hardening and thermal stresses
Authors: BÖHMER A. , ERTZ M. , KNOTHE K.
Published: October 2003

Sliding friction between railway wheels and rails results in elevated contact temperatures and gives rise to severe thermal stresses at the wheel and rail surfaces. The thermal stresses have to be superimposed on the mechanical contact stresses. Due to the distribution of stresses, the rail surface is generally subjected to higher stresses than the wheel surface. The elastic limit is reduced and yield begins at lower mechanical loads. During the first cycles of plastic deformation, the material hardens and residual stresses build up. The residual stresses provide the structure to shake down to pure elastic behaviour in subsequent load cycles up to a shakedown limit. The kind of hardening observed for rail steel has a considerable influence on the shakedown limit. The shakedown limit is dropped to lower mechanical loads due to the thermal stresses in the rail surface as well. This might cause structural changes in the rail material and rail damage.
Rail defects: an overview
Authors: CANNON D. F. , EDEL K.‐O. , GRASSIE S. L. , SAWLEY K.
Published: October 2003

For about 150 years, the steel rail has been at the very heart of the world's railway systems. The rail works in a harsh environment and, as part of the track structure, it has little redundancy; thus, its failure may lead to catastrophic derailment of vehicles, the consequences of which can include death, injury, costs and loss of public confidence. These can have devastating and long‐lasting effects on the industry. Despite the advances being made in railway permanent way engineering, inspection and rail‐making technology, continually increasing service demands have resulted in rail failure continuing to be a substantial economic burden and a threat to the safe operation of virtually every railway in the world. This paper presents an overview of rail defects and their consequences from the earliest days of railways to the present day.
Image analysis to reveal crack development using a computer simulation of wear and rolling contact fatigue
Authors: FLETCHER D. I. , FRANKLIN F. J. , KAPOOR A.
Published: October 2003

Plastic flow of near‐surface rail material under contact loading is a feature of rail–wheel contact, and severe flow typically leads to both wear, and the initiation and development of small surface‐breaking cracks. This paper presents results from a ratcheting based computer simulation, which has been developed to allow the simultaneous investigation of wear, crack initiation and early crack propagation. To identify repeatably small crack‐like flaws, image analysis is applied to the visual representation of the wearing surface generated by the model. This representation shows a good similarity to traditional micrographs taken from sections of worn surfaces. The model clearly reveals the interaction of wear with crack development, processes which are linked because wear truncates surface‐breaking cracks, and can completely remove small surface‐breaking cracks.
Rolling contact in railways: modelling, simulation and damage prediction
Authors: VAN K. DANG , MAITOURNAM M. H.
Published: October 2003

Various kinds of defects are induced by rolling contact on the rail track: kidney‐shaped cracking, shelling and nowadays squat and head checking, which are studied under the sponsorship of the French national railways company SNCF. Modelling of such defects requires the development of specific computational tools in order to evaluate, in the vicinity of the wheel–rail contact zone, the mechanical state (stress, plastic strain cycle and residual stress pattern), which is at the origin of the damages. Moreover, since the loadings induce multiaxial stress and strain states, it is necessary to use a multiaxial criterion to predict the occurrence of fatigue cracks. This review paper is devoted to the presentation of the main results of this research.
On the temperature in the wheel–rail rolling contact*
Authors: FISCHER F. D. , DAVES W. , WERNER E. A.
Published: October 2003

The flash temperature in an asperity of the rail due the wheel–rail rolling contact is investigated. First the contact configuration and the total heat produced are explained. Then approaches to heat partitioning between the two contacting bodies are discussed. A new heat partitioning factor is derived for the case of frictional heating and heating due to plastic deformation, thereby taking into account the roughness of the contacting surfaces by a contact intensity factor distribution as well as the local pressure intensification by individual asperities. Several roughness distributions are studied. Finally, an explicit calculation is outlined of the asperity flash temperature at the end of the contact, expressed by two temperatures and two factors contributing to the partitioning of heat between the contacting bodies.
The wheel–rail interface—some recent accidents
Authors: SMITH R. A.
Published: October 2003

The importance of the wheel–rail interface to the safe operation of railways is discussed. Some aspects of the history of rails and wheels are introduced. Several recent accidents involving the wheel–rail interface are described. The great importance of operating both vehicles and track as a system is emphasized, together with the necessity of maintaining both in good condition.
The current status of theory and practice on rail integrity in Japanese railways—rolling contact fatigue and corrugations
Authors: ISHIDA M. , AKAMA M. , KASHIWAYA K. , KAPOOR A.
Published: October 2003

The paper describes the Japanese understanding and practice with regard to wheel rail interface problems and their management. Rolling contact fatigue, especially squat defects, grinding, corrugations and lubrication, have been considered. The understanding has been developed through a combination of theoretical modeling, laboratory‐based experiments and field trials. Measures have been introduced to mitigate the detrimental effects of these problems and are resulting in benefits to the Japanese railway companies. However, more work is required to better understand wheel rail interface problems and to provide effective solutions.
Resource dispersion and consumer dominance: scavenging at wolf‐ and hunter‐killed carcasses in Greater Yellowstone, USA
Authors: Wilmers Christopher C. , Stahler Daniel R. , Crabtree Robert L. , Smith Douglas W. , Getz Wayne M.
Published: October 2003

The Greater Yellowstone Ecosystem in the northern Rocky Mountains provides the context for a natural experiment to investigate the response of consumers to resources with differing spatial and temporal dispersion regimes. Grey wolves (Canis lupus) and human hunters both provide resource subsidies to scavengers by provisioning them with the remains of their kills. Carrion from hunter kills is highly aggregated in time and space whereas carrion from wolf kills is more dispersed in both time and space. We estimated the total amount of carrion consumed by each scavenger species at both wolf and hunter kills over 4 years. Species with large feeding radii [bald eagles (Haliaeetus leucocephalus) and ravens (Corvus corax)], defined as the area over which a consumer can efficiently locate and integrate resources, dominated consumption at the highly aggregated hunter kills whereas competitively dominant species [coyotes (Canis latrans)] dominated at the more dispersed wolf kills. In addition, species diversity and the evenness of carrion consumption between scavengers was greater at wolf kills than at hunter kills while the total number of scavengers at hunter kills exceeded those at wolf kills. From a community perspective, the top–down effect of predation is likely to be stronger in the vicinity of highly aggregated resource pulses as species with large feeding radii switch to feeding on alternative prey once the resource pulse subsides.
The evolutionary and ecological role of heat shock proteins
Authors: Sørensen Jesper Givskov , Kristensen Torsten Nygaard , Loeschcke Volker
Published: October 2003

Most heat shock proteins (Hsp) function as molecular chaperones that help organisms to cope with stress of both an internal and external nature. Here, we review the recent evidence of the relationship between stress resistance and inducible Hsp expression, including a characterization of factors that induce the heat shock response and a discussion of the associated costs. We report on studies of stress resistance including mild stress, effects of high larval densities, inbreeding and age on Hsp expression, as well as on natural variation in the expression of Hsps. The relationship between Hsps and life history traits is discussed with special emphasis on the ecological and evolutionary relevance of Hsps. It is known that up‐regulation of the Hsps is a common cellular response to increased levels of non‐native proteins that facilitates correct protein folding/refolding or degradation of non‐functional proteins. However, we also suggest that the expression level of Hsp in each species and population is a balance between benefits and costs, i.e. a negative impact on growth, development rate and fertility as a result of overexpression of Hsps. To date, investigations have focused primarily on the Hsp70 family. There is evidence that representatives of this Hsp family and other molecular chaperones play significant roles in relation to stress resistance. Future studies including genomic and proteonomic analyses will increase our understanding of molecular chaperones in stress research.
Abundance–body mass relationships in size‐structured food webs
Authors: Jennings Simon , Mackinson Steve
Published: October 2003

In communities sharing a common energy source, the energetic equivalence hypothesis predicts that numerical abundance (N) scales with body mass (M) asM−0.75. However, in size‐structured food webs all individuals do not share a common energy source, and the energy available (E) to larger individuals is constrained by inefficient energy transfer through the food chains that support them. This is expected to lead to steeper scalings ofNwithM. Here, we formalize and test an existing model for predicting abundance–body mass scaling, where the decline inEwithMis calculated from the mean predator–prey body mass ratio (from size‐based nitrogen stable isotope analysis) and trophic transfer efficiency. We show that the steep predicted scalings of abundance and body mass (Nscales asM−1.2,Bscales asM−0.2) in a marine food web are consistent with empirical estimates and can be attributed to the small predator–prey body mass ratio (106 : 1). As a previous study has shown that environmental stability may favour low predator–prey mass ratios and long food chains, we predict that steeper abundance–body mass relationships will be found in more stable environments.
Population mixing accelerates coevolution
Authors: Brockhurst Michael A. , Morgan Andrew D. , Rainey Paul B. , Buckling Angus
Published: October 2003

Theory predicts that mixing in spatially structured populations of hosts and parasites can increase the rate of antagonistic coevolution. We experimentally tested this prediction by allowing populations of bacteria (Pseudomonas fluorescens) and parasitic bacteriophage to coevolve in mixed and unmixed microcosms. Coevolution proceeded at approximately twice the rate in mixed populations compared with unmixed populations and caused the evolution of more resistant hosts and more infective parasites.
Phylogeny and the evolution of acoustic communication in extant Ensifera (Insecta, Orthoptera)
Authors: Desutter‐Grandcolas Laure
Published: October 2003

Ensifera present an appropriate and interesting model for the study of acoustic communication, because of their diverse signal and communication modalities, and due to their accessibility for field and laboratory studies. Several hypotheses have been proposed to explain the acoustic evolution of Ensifera, but they were elaborated without any reference to a falsifiable phylogeny, and were consequently highly speculative. Similarly, phylogenetic relationships between ensiferan clades have not hitherto been studied using modern standard methodology, and the sole cladistic analysis by Gwynne in 1995 was methodologically flawed. No sound hypothesis therefore currently exists for ensiferan phylogeny, which precludes historical analysis of their communication modalities. In the present paper, the phylogeny is established on the basis of morpho‐anatomical characters and used to analyse the evolution of acoustic communication in this clade by mapping the characters related to auditory and stridulatory structures onto the resultant trees. Cladistic analyses resulted in two equi‐parsimonious cladograms (length 154, C 64, CI 58, RI 61) with the following topologies: (1) [(Grylloidea–Gryllotalpidae) (Rhaphidophoridae (Schizodactylidae (Gryllacrididae ((Stenopelmatidae–Cooloola) (Anostostomatidae (Prophalangopsis(Cyphoderris(Tettigoniidae–Lezina))))))))] (2) [(Grylloidea–Gryllotalpidae)(Rhaphidophoridae (Schizodactylidae (Gryllacrididae–Cooloola–(Stenopelmatidae (Anostostomatidae (Prophalangopsis(Cyphoderris(Tettigoniidae–Lezina))))))))]. According to these topologies, Ensifera were ancestrally devoid of acoustic and hearing systems. An acoustic (tegminal or femoro‐abdominal) apparatus appeared a number of times independently with convergent structures. Similarly, tibial tympana developed several times independently. Moreover, four hypotheses (each according to a definite pattern of character transformation) can be proposed to explain the evolution of acoustic communication in the different ensiferan clades and relate it to a definite communicatory context. These hypotheses do not apply equally to ensiferan subclades. Grylloidea and Gryllotalpoidea could have experienced convergently a direct development of an intraspecific acoustic communication. Acoustic communication in Tettigoniidea has evolved more ambiguously, and may either have resulted from a direct evolution analogous to that having occurred in Gryllidea, or have developed in a completely different behavioural context. Future studies of acoustic communication in the different ensiferan clades will have to take into account the fact that the involved structures most often are not homologous and that their evolution may not have taken place in similar conditions. Different hypotheses of acoustic communication evolution may apply to different clades, and there may be no single explanation for acoustic communication in Ensifera.
The bioclimatic model: a method of palaeoclimatic qualitative inference based on mammal associations
Authors: Fernández Manuel Hernández , Peláez‐Campomanes Pablo
Published: October 2003

Aim  The bioclimatic model is a new method for palaeoclimatic reconstruction built on the assumption of a significant correlation between climate and mammal community composition. The goal of this approach is to infer past climatic conditions using mammal fossil associations as source data.

Location  The study used mammal faunas from all over the world to develop the bioclimatic model. As an example of the potential of the model, we have applied it to Quaternary faunas from Eurasia.

Methods  The proposed model was constructed by applying multivariate discriminant analysis to modern mammal faunas and climates from throughout the world. The model was validated with a different set of modern faunas than those used in the discriminant analysis, including some from transitional zones between different climates (ecotones). To test the reliability of the method in the Pleistocene, the results have been compared to those obtained with data from other disciplines, such as palaeobotany.

Results  The results obtained in the validation of the model show that more than 90% of the localities have been classified correctly. Comparisons of results in the late Pleistocene‐Holocene of Barová between a palaeobotanical study and the bioclimatic analysis show the latter to be highly accurate. The results for early Pleistocene faunas show somewhat drier and more open climatic conditions for Europe than the present day, with larger areas of steppe environments.

Main Conclusions  The bioclimatic model could be used to infer climatic conditions from mammal faunas. The results presented in this work provide a preliminary example of the potential that bioclimatic analysis has as a tool for palaeoclimatic inference. Finally, this method offers the opportunity to standardize data coming from vertebrate palaeontology for use in the construction and evaluation of climatic models.
Does climate determine broad‐scale patterns of species richness? A test of the causal link by natural experiment
Authors: H‐Acevedo Dagoberto , Currie David J.
Published: October 2003

Aim Broad‐scale spatial patterns of species richness are very strongly correlated with climatic variables. If there is a causal link, i.e. if climate directly or indirectly determines patterns of richness, then when the climatic variables change, richness should change in the manner that spatial correlations between richness and climate would predict. The present study tests this prediction using seasonal changes in climatic variables and bird richness.

Location We used a grid of equal area quadrats (37 000 km2) covering North and Central America as far south as Nicaragua.

Methods Summer and winter bird distribution data were drawn from monographs and field guides. Climatic data came from published sources. We also used remotely sensed NDVI (normalized difference vegetation index — a measure of greenness).

Results Bird species richness changes temporally (between summer and winter) in a manner that is close to, but statistically distinguishable from, the change one would predict from models relating the spatial variation in richness at a single time to climatic variables. If one further takes into account the seasonal changes in NDVI and within‐season variability of temperature and precipitation, then winter and summer richness follow congruent, statistically indistinguishable patterns.

Main conclusions Our results are consistent with the hypothesis that climatic variables (temperature and precipitation) and vegetation cover directly or indirectly influence patterns of bird species richness.
Relative influences of current and historical factors on mammal and bird diversity patterns in deglaciated North America
Authors: Hawkins Bradford A. , Porter Eric E.
Published: October 2003

Aim   To investigate the relative contributions of current vs. historical factors in explaining broad‐scale diversity gradients using a combination of contemporary factors and a quantitative estimate of the temporal accessibility of areas for recolonization created by glacial retreat following the most recent Ice Age.

Location   The part of the Nearctic region of North America that was covered by ice sheets during the glacial maximum 20 000 BP.

Methods   We used range maps to estimate the species richness of mammals and terrestrial birds in 48 400 km2 cells. Current conditions in each cell were quantified using seven climatic and topographical variables. Historical conditions were estimated using the number of years before present when an area became exposed as the ice sheets retreated during the post‐Pleistocene climate warming. We attempted to tease apart contemporary and historical effects using multiple regression, partial regression and spatial autocorrelation analysis.

Results   A measure of current energy inputs, potential evapotranspiration, explained 76–82% of the variance in species richness, but time since deglaciation explained an additional 8–13% of the variance, primarily due to effects operating at large spatial scales. Because of spatial covariation between the historical climates influencing the melting of the ice sheet and current climates, it was not possible to partition their effects fully, but of the independent effects that could be identified, current climate explained two to seven times more variance in richness patterns than age.

Main Conclusions   Factors acting in the present appear to have the strongest influence on the diversity gradient, but an historical signal persisting at least 13 000 years is still detectable. This has implications for modelling changes in diversity patterns in response to future global warming.
Six types of species‐area curves
Authors: Scheiner Samuel M.
Published: October 2003

Macroecological studies infer ecological processes based on observed patterns. An often used measure of pattern is the species‐area curve. Insufficient attention has been paid to the variety of methods used to construct those curves. There are six different methods based on different combinations of: (1) the pattern of quadrats or areas sampled (nested, contiguous, noncontiguous, or island); (2) whether successively larger areas are constructed in a spatially explicit fashion or not; and (3) whether the curve is constructed from single values or mean values. The resulting six types of curves differ in their shapes, how diversity is encapsulated, and the scales encompassed. Inventory diversity (α) can either represent a single value or a mean value, creating a difference in the focus of the measure. Differentiation diversity (β) can vary in the extent encompassed, and thus the spatial scale, depending on the pattern of quadrat placement. Species‐area curves are used for a variety of purposes: extrapolation, setting a common grain, and hypothesis testing. The six types of curves differ in how they are used or interpreted in these contexts. A failure to recognize these differences can result in improper conclusions. Further work is needed to understand the sampling and measurement properties of the different types of species‐area curves.
Environmental variability and biogeography: the relationship between bathymetric distribution and geographical range size in marine algae and gastropods
Authors: Harley Christopher D. G. , Smith Katherine F. , Moore Vicki L.
Published: October 2003

Aims  Gradients of environmental variability have been proposed to explain spatial variation in patterns of geographical range size. We explore this relationship in NE Pacific algae and NW Atlantic gastropods by using the characteristics of species’ bathymetric distributions as a proxy for tolerance of environmental variability.

Location  NE Pacific and NW Atlantic.

Methods  Data on species bathymetric and geographical distributions were compiled from the literature.

Results  For both algae and gastropods, species that inhabit highly seasonal, shallow depth zones have broader latitudinal ranges, and occupy more biogeographical provinces, than species that live in more temporally stable, deeper zones. Furthermore, species that tolerate spatial variability along the bathymetric axis, i.e. those that occur in multiple depth zones, have broader geographical ranges than species restricted to fewer depth zones.

Main conclusions  Within‐range environmental variability, through both space and time, is predictive of large geographical ranges for marine algae and gastropods. Analysis of species distributions across perpendicular gradients (e.g. depth and latitude) is a powerful approach to discerning the mechanisms that govern biogeographical patterns, and provides easily obtainable broad‐brush predictions regarding the biogeographical outcomes of global change.
The physiology of circadian rhythms in plants
Authors: Webb Alex A. R.
Published: October 2003

Circadian rhythms regulate many aspects of plant physiology including leaf, organ and stomatal movements, growth and signalling. The genetic identity of some of the components of the core circadian oscillator has recently become known. Similarly, the photoperception and phototransduction pathways that entrain the oscillator to the day and night cycle are being determined. Less clear are the pathways by which the circadian oscillator regulates cellular physiology. Circadian oscillations in cytosolic free calcium might act to transduce the temporal outputs of the circadian oscillator. This hypothesis requires rigorous testing using novel noninvasive technologies. Plants might gain advantage from the circadian clock by being able to predict changes in the environment and coordinate physiological processes, presumably increasing survival and hence, reproductive fitness. Technical advances coupled with cell‐specific measurement techniques will allow the advantages of the circadian regulation of physiology to be quantified.

Contents

Summary
281

I.
Introduction
282

II.
The circadian clock
283

III.
The regulation of cellular physiology by circadian oscillations in cytosolic free Ca2+
286

IV.
The circadian regulation of physiology
292

V.
The benefits of the circadian regulation of physiology
298

VI.
Future prospects
299

VIII.
Conclusions
300

Acknowledgements
300

References
300
Diversity of ammonia monooxygenase (amoA) genes across environmental gradients in Chesapeake Bay sediments
Authors: Francis Chris A. , O'Mullan Gregory D. , Ward Bess B.
Published: October 2003

Chesapeake Bay, the largest estuary in North America, encompasses a wide range of nutrient loading and trophic levels from the rivers and upper Bay to the sea, providing an ideal natural environment in which to explore relationships between functional diversity, physical/chemical complexity and ecosystem function (e.g. nitrification). In this study, amoA gene fragments (encoding subunit A of the key nitrification enzyme, ammonia monooxygenase) were PCR‐amplified from DNA extracted from sediment cores collected at five stations spanning gradients of salinity, ammonium, nitrate, oxygen and organic carbon along the Bay and Choptank River, a subestuary of the Bay. Phylogenetic analysis of ∼30 amoA clones from each station revealed extensive diversity within the β‐Proteobacteria group of ammonia‐oxidizing bacteria (AOB), with the vast majority of sequences falling into coherent phylogenetic clusters distinct from sequences of cultivated AOB. Over 70% of the clones fell into two major phylogenetic clusters that appear to represent novel groups of Nitrosomonas‐like and Nitrosospira‐like amoA sequences that may be specific to estuarine and marine environments. Rarefaction analysis, estimators of genetic variation and dissimilarity indices all revealed differences in the relative amoA‐based diversity and/or richness among most of the stations, with the highest diversity at the North Bay station and the lowest at the mesohaline stations. Although salinity appears to play a role, no single physical or chemical parameter entirely explains the pattern of diversity along the estuary, suggesting that a complex combination of environmental factors may shape the overall level of AOB diversity in this dynamic environment.
Recent ecological and biogeochemical changes in alpine lakes of Rocky Mountain National Park (Colorado, USA): a response to anthropogenic nitrogen deposition
Authors: Wolfe Alexander P. , Van Gorp Alison C. , Baron Jill S.
Published: October 2003

Dated sediment cores from five alpine lakes (>3200 m asl) in Rocky Mountain National Park (Colorado Front Range, USA) record near‐synchronous stratigraphic changes that are believed to reflect ecological and biogeochemical responses to enhanced nitrogen deposition from anthropogenic sources. Changes in sediment proxies include progressive increases in the frequencies of mesotrophic planktonic diatom taxa and diatom concentrations, coupled with depletions of sediment δ15N and C : N values. These trends are especially pronounced since approximately 1950. The most conspicuous diatoms to expand in recent decades are Asterionella formosa and Fragilaria crotonensis. Down‐core species changes are corroborated by a year‐long sediment trap experiment from one of the lakes, which reveals high frequencies of these two taxa during autumn and winter months, the interval of peak annual limnetic []. Although all lakes record recent changes, the amplitude of stratigraphic shifts is greater in lakes east of the Continental Divide relative to those on the western slope, implying that most nitrogen enrichment originates from urban, industrial and agricultural sources east of the Rocky Mountains. Deviations from natural trajectories of lake ontogeny are illustrated by canonical correspondence analysis, which constrains the diatom record as a response to changes in nitrogen biogeochemistry. These results indicate that modest rates of anthropogenic nitrogen deposition are fully capable of inducing directional biological and biogeochemical shifts in relatively pristine ecosystems.