bluuebunny/crossref_metadata_2025_split huggingface dataset:
Host introductions and the geography of parasite taxonomic diversity
Authors: Poulin Robert , Mouillot David 
Published: May 2003

AbstractAim  Geographical variation in parasite diversity is examined among populations of fish in their original heartland and in areas where they have been introduced. The diversity in heartland and introduced populations is contrasted, and also compared with the expectations of a null model.Location  Data on the parasite communities of two salmonid fish species were obtained: the rainbow trout Oncorhynchus mykiss in its British Columbia heartland and in introduced populations in North America, Great Britain, South America and New Zealand; and the brown trout Salmo trutta in heartland populations from Great Britain, and in introduced populations in North America, South America and New Zealand.Methods  The average taxonomic distinctness and its variance were computed for each parasite community, and used as measures of the taxonomic diversity of parasite species in each fish population. Observed values of taxonomic distinctness were also compared with those expected if each community was a random selection from the world list of parasite species known for each of the two host species.Results  Few parasite communities departed from the expectations of the null model, i.e. few had a taxonomic diversity of parasites greater or lower than that expected from a random selection of parasite species. However, these departures were not more or less likely among heartland fish populations than among introduced ones. In both fish species, parasite communities in introduced populations tended to be a little more taxonomically diverse than in the heartland populations.Main conclusions  Overall, the results suggest that the accumulation of parasite species in introduced hosts over short (ecological) periods of time can result in parasite assemblages that are just as, or even more, taxonomically diverse than those developed over much longer (evolutionary) time frames in the host species geographical heartland. This finding highlights the importance of ecological factors in parasite biodiversity in addition to coevolutionary processes.
Relative importance of environment, human activity and spatial situation in determining the distribution of terrestrial mammal diversity in Argentina
Authors: Real Raimundo , Márcia Barbosa A. , Porras Daniela , Kin Marta S. , Márquez Ana L. , Guerrero José C. , Javier Palomo L. , Justo Enrique R. , Mario Vargas J. 
Published: May 2003

AbstractAim The partition of the geographical variation in Argentinian terrestrial mammal species richness (SR) into environmentally, human and spatially induced variation.Location Argentina, using the twenty‐three administrative provinces as the geographical units.Methods We recorded the number of terrestrial mammal species in each Argentinian province, and the number of species belonging to particular groups (Marsupialia, Placentaria, and among the latter, Xenarthra, Carnivora, Ungulates and Rodentia). We performed multiple regressions of each group's SR on environmental, human and spatial variables, to determine the amounts of variation explained by these factors. We then used a variance partitioning procedure to specify which proportion of the variation in SR is explained by each of the three factors exclusively and which proportions are attributable to interactions between factors.Results  For marsupials, human activity explains the greatest part of the variation in SR. The purely environmental and purely human influences on all mammal SR explain a similarly high proportion of the variation in SR, whereas the purely spatial influence accounts for a smaller proportion of it. The exclusive interaction between human activity and space is negative in carnivores and rodents. For rodents, the interaction between environment and spatial situation is also negative. In the remaining placental groups, pure spatial autocorrelation explains a small proportion of the variation in SR.Main conclusions  Environmental factors explain most of the variation in placental SR, while Marsupials seem to be mainly affected by human activity. However, for edentates, carnivores, and ungulates the pure human influence is more important than the pure spatial and environmental influences. Besides, human activity disrupts the spatial structure caused by the history and population dynamics of rodents and, to a lesser extent, of carnivores. The historical events and population dynamics on the one hand, and the environment on the other, cause rodent SR to vary in divergent directions. In the remaining placental groups the autocorrelation in SR is mainly the result of autocorrelation in the environmental and human variables.
Shapes and functions of species–area curves: a review of possible models
Authors: Tjørve Even 
Published: May 2003

AbstractAim  This paper reviews possible candidate models that may be used in theoretical modelling and empirical studies of species–area relationships (SARs). The SAR is an important and well‐proven tool in ecology. The power and the exponential functions are by far the models that are best known and most frequently applied to species–area data, but they might not be the most appropriate. Recent work indicates that the shape of species–area curves in arithmetic space is often not convex but sigmoid and also has an upper asymptote.Methods  Characteristics of six convex and eight sigmoid models are discussed and interpretations of different parameters summarized. The convex models include the power, exponential, Monod, negative exponential, asymptotic regression and rational functions, and the sigmoid models include the logistic, Gompertz, extreme value, Morgan–Mercer–Flodin, Hill, Michaelis–Menten, Lomolino and Chapman–Richards functions plus the cumulative Weibull and beta‐P distributions.Conclusions  There are two main types of species–area curves: sample curves that are inherently convex and isolate curves, which are sigmoid. Both types may have an upper asymptote. A few have attempted to fit convex asymptotic and/or sigmoid models to species–area data instead of the power or exponential models. Some of these or other models reviewed in this paper should be useful, especially if species–area models are to be based more on biological processes and patterns in nature than mere curve fitting. The negative exponential function is an example of a convex model and the cumulative Weibull distribution an example of a sigmoid model that should prove useful. A location parameter may be added to these two and some of the other models to simulate absolute minimum area requirements.
How does landscape context contribute to effects of habitat fragmentation on diversity and population density of butterflies?
Authors: Krauss Jochen , Steffan‐Dewenter Ingolf , Tscharntke Teja 
Published: May 2003

AbstractAim Studies on habitat fragmentation of insect communities mostly ignore the impact of the surrounding landscape matrix and treat all species equally. In our study, on habitat fragmentation and the importance of landscape context, we expected that habitat specialists are more affected by area and isolation, and habitat generalists more by landscape context.Location and methods The study was conducted in the vicinity of the city of Göttingen in Germany in the year 2000. We analysed butterfly communities by transect counts on thirty‐two calcareous grasslands differing in size (0.03–5.14 ha), isolation index (2100–86,000/edge‐to‐edge distance 55–1894 m), and landscape diversity (Shannon–Wiener: 0.09–1.56), which is correlated to percentage grassland in the landscape.Results A total of 15,185 butterfly specimens belonging to fifty‐four species are recorded. In multiple regression analysis, the number of habitat specialist (n = 20) and habitat generalist (n = 34) butterfly species increased with habitat area, butz‐values (slopes) of the species–area relationships for specialists (z = 0.399) were significantly steeper compared with generalists (z = 0.096). Generalists, but not specialists, showed a marginally significant increase with landscape diversity. Effects of landscape diversity were scale‐dependent and significant only at the smallest scale (landscape context within a 250 m radius around the habitat). Habitat isolation was not related to specialist and generalist species numbers. In multiple regression analysis the density of specialists increased significantly with habitat area, whereas generalist density increased only marginally. Habitat isolation and landscape diversity did not show any effects.Main conclusions Habitat area was the most important predictor of butterfly community structure and influenced habitat specialists more than habitat generalists. In contrast to our expectations, habitat isolation had no effect as most butterflies could cope with the degree of isolation in our study region. Landscape diversity appeared to be important for generalist butterflies only.
Regional and local variation of spider assemblages (Araneae) from coastal grey dunes along the North Sea
Authors: Bonte D. , Criel P. , Van Thournout I. , Maelfait J.‐P. 
Published: May 2003

AbstractAim This study aims to determine the underlying causes of local and regional patterns of variation in community structure of spiders in coastal grey dunes, and especially whether ecological time constrains the species composition in young and isolated grey dune habitats.Location The study was conducted in coastal dunes from northern France (Boulonnais, Nord‐Pas‐de‐Calais), Belgium (Flemish coastal dunes) and the Netherlands [Amsterdam Water Supply (AWD) dunes and Dunes from the Provincial Water Company North‐Holland].Methods Spiders were collected with pitfall traps in twenty‐eight grey dune patches in the four areas under investigation. Species composition and environmental parameters (vegetation structure, distance to the sea and the patch‐edge, eolic dynamics and lime richness) were determined. Assemblage composition was related to the regional and local environmental factors with the Primer software package to determine the assemblage‐determining parameters. Differences in species presence were analysed as a function of their habitat preference and distribution range.Results Differences in grey dune spider assemblage structure can mainly be attributed to differences in local sand dynamics and the region. Species from dynamic dunes are mainly present in grey dunes from Belgium and France, while species from non‐dunal xerothermic habitats (chalk grasslands and heathland) occur in both the Boulonnais and the north Holland dune region. These species are absent from geologically young or other xerotherm habitat isolated Flemish coastal dunes.Main conclusion The data show that regional variation in spider assemblage composition results from local landscape characteristics (dynamics in the dune area), the latitude and the connectivity to non‐dunal xerothermic habitats. The strong and moderate geological isolation of dune areas from the Flemish coast and the AWD dunes, respectively, results in the absence of (at least some) species that are primarily bound to heathland and/or chalk grassland. This indicates the importance of ecological time for the assemblage structure. The limited dispersal capacity of the heathland and/or chalk grassland species is probably the main reason for their absence.
Morphological variability and developmental instability in subpopulations of the Eurasian badger (Meles meles) in Denmark
Authors: Pertoldi Cino , Bach Lars A. , Madsen Aksel Bo , Randi Ettore , Loeschcke Volker 
Published: May 2003

AbstractAim Local populations from different geographical regions may differ in the selection regimes to which they are exposed. Differences in environmental factors and population density may affect the relative importance of different selective forces (e.g. natural vs. sexual selection). We suggest a direction of investigation concerned with the developmental instability of morphological traits. The goal is to disclose putative small‐scale geographical differences in the evolutionary forces, which may be hard to detect.Location Craniometrical investigations were carried out on ninety‐eight skulls and teeth of the Eurasian badger (Meles meles) collected during the period 1995–97 from three different populations in Denmark. One of these thrives at low population density, whereas the two others are characterized by high local density.Methods The skulls were investigated for developmental instability (DI) using fluctuating asymmetry (FA) as its estimator. FA was measured on canines, molars, premolar teeth and other skull and mandible traits. For the statistical analyses, we applied nonparametric permutation tests.Results Evidence was found suggesting differentiation among populations in mean degree of FA, and the FA values measured on canines were higher in the high‐density populations. FA of the canines was significantly higher in males than females, in contrast to FA of the other traits. Evidence of a negative relationship between canine size and their FA was found, whereas no significant correlations were found between the molar and premolar teeth measures and their FA.Main conclusions Our results suggest that canines could be under directional selection stemming from intrasexual competition, which may be stronger in high‐density zones. The other teeth investigated seem to be under a stabilizing regime hence their FA is mainly affected by environmental stresses. The negative relationship between canine size and FA found in males suggests the capacity of badgers to respond in an evolutionary way to environmental changes, despite the low genetic variability previously found at the molecular level.
Island biogeography of temporary wetland carabid beetle communities
Authors: Brose Ulrich 
Published: May 2003

AbstractAim  The study tests if island biogeography is applicable to invertebrate communities of habitat islands in the agricultural landscape that are not fragments of formerly larger habitats.Location  Thirty temporary wetlands in the agricultural landscape of northeast Germany.Methods  The composition and species richness of carabid beetle communities was analysed. Habitat area, isolation, the density of temporary wetlands in the landscape, land‐use intensity and the maximum duration of flooding were recorded as independent variables. Overall species richness and wetland species richness were studied in independent regression analyses. The community composition was analysed by means of a Canonical Correspondence Analysis (CCA). A partial CCA was used to analyse the effect of the distance to the edge of the field after removing impacts of other independent variables.Results  The area of the habitats and various measures of isolation (mean distances = 81–240 m) did not influence species richness or wetland species richness. The community composition was mainly determined by the land‐use intensity, habitat area did not have significant effects, and the distance to the edge of the field was the only effective isolation parameter. Short‐winged species were more often affected by the distance to the edge of the field than full‐winged species.Main conclusion  There is evidence that the distances between the wetlands do not provide an effective barrier to the species dispersal and, therefore, metapopulation structures including subpopulations of multiple temporary wetlands might counteract local area effects on subpopulations. Short‐winged species, however, might be more affected by isolation than full‐winged species. As carabid beetle community structure in most early successional habitats is similar, these results may be representative of many agricultural landscape habitats. Nature conservancy concepts that aim to increase habitat area and habitat connectivity have successfully been applied to fragmented late‐successional habitats. The present study indicates that such concepts do not necessarily result in higher diversity or larger populations in early successional habitats.
The limits to biogeographical distributions: insights from the northward range extension of the marine snail, Kelletia kelletii (Forbes, 1852)
Authors: Zacherl Danielle , Gaines Steven D. , Lonhart Steve I. 
Published: May 2003

AbstractAim The development of accurate models predicting species range shifts in response to climate change requires studies on the population biology of species whose distributional limits are in the process of shifting. We examine the population biology of an example system using the recent northward range expansion of the marine neogastropod Kelletia kelletii (Forbes, 1852).Location This is a marine coastal shelf neogastropod species whose range extends from Isla Asuncion (Baja California, Mexico) to Monterey (CA, USA). Research sites spanned the extent of the range.Methods We examine abundance distributions and size frequency distributions of K. kelletii for evidence of factors determining historic and contemporary distributional patterns. Population studies were supplemented by historic and contemporary hydrographic data, including seawater temperature data from California Cooperative Oceanic Fisheries Investigations (CalCOFI ) and National Data Buoy Center (NDBC), and seawater circulation data.Results The structure of recently established populations varied dramatically from that of historic populations. Markedly low densities and irregular size frequency distributions characterized recently established populations and suggested only occasionally successful recruitment. The point of transition between historic and recently established populations also corresponded to the location of a gradient in seawater temperature and the confluence of two major oceanic currents. The accumulated data suggest that temperature and/or barriers to dispersal could have set both contemporary patterns in population structure as well as the former northern range limit.Main conclusions Early life stages play a critical role in determining distributional patterns of K. kelletii. Dispersal barriers and temperature limitation are two plausible mechanisms that could determine both contemporary and historic distributional patterns. Future studies on this species should attempt to tease apart the relative importance of these factors in maintaining the populations at the northern edge of the range.
Non‐linearity in clinical practice
Authors: Petros Peter 
Published: June 2003

AbstractThe whole spectrum of medicine consists of complex non‐linear systems that are balanced and interact with each other. How non‐linearity confers stability on a system and explains variation and uncertainty in clinical medicine is discussed. A major theme is that a small alteration in initial conditions may have a major effect on the end result. In the context of non‐linearity, it is argued that ‘evidence‐based medicine’ (EBM) as it exists today can only ever be relevant to a small fraction of the domain of medicine, that the ‘art of medicine’ consists of an intuitive ‘tuning in’ to these complex systems and as such is not so much an art as an expression of non‐linear science. The main cause of iatrogenic disease is interpreted as a failure to understand the complexity of the systems being treated. Case study examples are given and analysed in non‐linear terms. It is concluded that good medicine concerns individualized treatment of an individual patient whose body functions are governed by non‐linear processes. EBM as it exists today paints with a broad and limited brush, but it does promise a fresh new direction. In this context, we need to expand the spectrum of scientific medicine to include non‐linearity, and to look upon the ‘art of medicine’ as a historical (but unstated) legacy in this domain.
Achieving change in health care practice
Authors: Redfern Sally , Christian Sara 
Published: June 2003

AbstractThis study evaluated a practice development programme consisting of nine projects together known as STEP (South Thames Evidence‐Based Practice Project). The aim of STEP was to establish and assess evidence‐based practice in nursing and other health care practice areas. Objectives of the independent evaluation were to identify and assess outcomes from the process of change and investigate the association between these intermediate outcomes and patient outcomes. Outcomes were measured before and after the changes were introduced. Data collection methods included interviews with the change agents and other stakeholders, and a questionnaire to staff in each centre. Patient outcome data were collected from each centre. The findings revealed ‘dissemination’ of information to staff and ‘adherence’ by staff to new practice guidelines to be important intermediate outcomes in the process of change. The need emerged for a supportive organizational culture and commitment, recognition of the importance of change and a credible change agent. There was some evidence of linearity in the process of change in that a logical route appeared from dissemination of information to staff through adherence to the change guidelines to improvement in patient outcome in six of the nine centres. Linearity was less apparent in the other three centres, where the process of change seemed more dynamic and chaotic. These three centres were affected more than the others by organizational barriers to change. Our conclusions support the view that the linear model of change can work in settings with high levels of certainty but complexity theory is more likely to underpin the process of change in organizations characterized by uncertainty.
A critical appraisal of evidence‐based medicine: some ethical considerations
Authors: Gupta M. 
Published: June 2003

AbstractEvidence‐based medicine (EBM) is a concept that has grown to dominate the medical literature over the last decade. EBM has provoked a variety of criticisms, scientific, philosophical and sociological. However, while its basic conclusion – that we should practise EBM – is ethical, there has been limited ethical analysis of EBM. This paper aims to provide an analysis of EBM from an ethical perspective and identify some of EBM's potential ethical implications. Following a description of what constitutes EBM, this paper will identify and assess some of the basic values and epistemological assumptions of EBM that provide support for the moral duty to practise EBM. It will then examine potential ethical implications that could arise from practising EBM, given the challenges that have been made of EBM's assumptions and claims to authority. This paper will conclude by arguing that practitioners could strengthen the ethics of EBM by embracing a broader definition of evidence and including ethical criteria in the critical appraisal of research studies.