bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interactions between habitat heterogeneity and food affect reproductive output in a top predator
Authors: BYHOLM PATRIK , NIKULA ARI , KENTTA JUSSI , TAIVALMÄKI JUKKA‐PEKKA 
Published: February 2007

Summary

Habitat heterogeneity has important repercussions for species abundance, demography and life‐history patterns. While habitat effects have been more thoroughly studied in top‐down situations (e.g. in association with predation), their role in bottom‐up situations (e.g. in association with food abundance) has been less explored and the underlying mechanism(s) behind the ecological patterns have not commonly been identified.
With material from 1993 to 2003, we test the hypothesis that the reproduction of Finnish northern goshawks Accipiter gentilis (L.) is bottom‐up limited by habitat composition, especially in situations where the density of their main prey (grouse) is low. Special emphasis was placed on identifying the mechanism(s) behind potential habitat effects.
While laying date and large‐scale variation in the main prey density (but not habitat composition) were related to the number of eggs goshawks laid, small‐scale differences in alternative prey density between different territories later influenced how many young were fledged via the mechanism of habitat‐dependent partial‐brood loss. As a result of this mechanism, a difference in nestling condition also arose between goshawk territories with differing habitat compositions.
As the relative proportions of different landscape elements in a given landscape is a function of large‐scale differences in geomorphology and land use, this means that the reproductive performance of goshawks as averaged over larger scales can be understood correctly only in respect to the fact that habitat gradients differ across landscapes.
In addition to being one of the first papers identifying the mechanism of partial brood loss as being primarily responsible for the habitat‐specific differences in the production of young, this study further illustrates the need to identify small‐scale mechanisms to correctly understand the large‐scale patterns of reproductive performance in territorial species. The repercussions of the observed habitat effect for local population development are discussed.
Miocene hominoid biogeography: pulses of dispersal and differentiation
Authors: Folinsbee Kaila E. , Brooks Daniel R. 
Published: February 2007

AbstractAim To test the hypothesis that the ancestor of the hominines (African apes and humans) had an African origin by comparing the historical biogeographical patterns of hominoids with those of two other large land mammal clades, namely the hyaenids and proboscideans.Location Global, primarily the Old World over the last 25 Myr (Miocene to present).Methods Creation of a general area cladogram usingpact, a new method for generating area cladograms, and interpretation of general and clade‐specific speciation events involving hominoids, proboscideans and hyaenids.Results The analysis of the areas usingpactreveals both general patterns and clade‐specific exceptions to these patterns. All three groups share a general episode of species formation in Africa in the early Miocene, followed by ‘out of Africa’ expansion into Europe, Asia and North America, and a second general episode of species formation in Asia in the mid‐Miocene, followed by ‘out of Asia’ expansion into Africa, Europe and North America. Finally, there were two additional ‘out of Africa’ events during the late Miocene and into the Pliocene, the last one setting the stage for the emergence and spread ofHomo. In addition to these shared episodes of vicariance and dispersal, each group exhibits clade‐specific within‐area and peripatric speciation events.Main conclusions The complex history of dispersal and speciation over large areas exhibited by hominoids is part of a more general history of biotic diversification by taxon pulses. Refining this scenario will require the integration of additional clades from the same areas and times, as well as more detailed palaeoclimatological, palaeoenvironmental and geological evidence.
Plant strategy theories: a comment on Craine (2005)
Authors: GRIME J. PHILIP 
Published: February 2007

Summary

It is suggested that arguments concerning the nature of primary plant strategies could have been resolved more rapidly by reference to older literature relating to the behaviour of solutes in the rhizosphere and by more active programmes of plant trait screening.
The critique of CSR theory in Craine (2005) is rejected largely on the basis that it misunderstands the role of fundamental and proximal controls on vegetation composition (sensu Welden & Slauson 1986).
The ‘way forward’ advocated in Craine (2005) is flawed in its exclusive reliance on competition experiments. Recent progress in community and ecosystem ecology is strongly related to an increasing recognition of the declining importance of competition in unproductive or heavily disturbed environments.
Resource competition and plant traits: a response to Craine et al. 2005
Authors: TILMAN DAVID 
Published: February 2007

Summary

Resource competition theory incorporates the mechanisms that underlie consumer–resource interactions and the trade‐offs that constrain these mechanisms. Contrary to assertions by Craine, the concept of R* as the measure of resource reduction and the predictor of resource competition has not changed since it was proposed more than two decades ago.
Resource reduction, as summarized in R*, is readily observed. Soil concentrations of nitrate and water are decreased by plant uptake, and are lowered to different levels by different species. Tests have shown R* theory to correctly predict competitive outcomes for a variety of organisms and ecosystems.
Consumer‐resource mechanisms are a building block for theories that incorporate other trade‐offs faced by plants, such as those between competitive ability and dispersal.
Numerous plant traits interactively determine R* in a manner predictable from trait‐based resource competition theory. The same traits shown by comparative research to be associated with plant dominance in low‐nutrient habitats give lower R* values, greater predicted competitive ability and greater predicted abundances in nutrient‐limited habitats.
Plant ecology needs closer links between analytical theory, observations and experiments. Simple verbal theories can generate novel ideas but the logical implications of such scenarios are best explored using the rigorous logic of mathematics. Predictions of theory can then be tested via experiments and comparative studies.
Plant strategy theories: replies to Grime and Tilman
Authors: CRAINE JOSEPH M. 
Published: February 2007

Summary

In response to my essay review that attempted to reconcile the plant strategy theories of Grime and Tilman, Grime rejects five tenets that I had identified in his theories that were incomplete, inconsistent, or incorrect.
Grime fails to adequately address three of these concerns. Regarding the other concerns, it is clear that the concept of relative importance needs to be developed further. For example, if both competition and the stress of low nutrient supplies can remove species from a given environment, then neither can be elevated over the other without being tautological.
With regards to Tilman's response, it is clear that it will be important to be explicit about the relationship between data and models. At times, Tilman is neither evaluating individual models with a Popperian approach nor comparing contrasting models in a Bayesian fashion. As it stands, it is unclear what is required for Tilman to reject R* as the mechanism of competition, or whether it passes some undetermined threshold of acceptability.
Comparing concentration reduction to supply pre‐emption as the mechanism of competition recommends supply pre‐emption on many fronts. Supply pre‐emption better represents the movement of nutrients in soil solution. Assuming well‐mixed soil solutions can theoretically lead to improper prediction of competitive outcomes. Empirically, there are examples where R* does not predict outcomes for competition for nutrients, and supply pre‐emption appears to generate metrics (root length density) that are equivalent if not better than concentration reduction (R*) at explaining these outcomes.
The next plant strategies paradigm will not be a result of choosing either Grime's or Tilman's theories, but represent a synthesis of the two sets of theories while also incorporating novel concepts and research. I agree with Tilman that more research is needed in understanding mechanisms of coexistence, but there still remains large gaps in our understanding of plant traits and growth that limit our understanding of competition for nutrients and will likely constrain our understanding of coexistence even more.
Measuring the components of competition along productivity gradients
Authors: WILSON MARK V. 
Published: February 2007

Summary

Controversy surrounds the measurement of competition intensity. Moreover, when biomass varies systematically along productivity and other environmental gradients, common indices of competitive outcome mask important ecological interactions.
This study presents two indices derived from how neighbours interact with target plants. The first, relative crowding, increases directly with the abundance of neighbours present and decreases inversely with the potential size and vigour of the target plant itself. The second, interaction strength, is the integral of suppression of the target by neighbours over the range of neighbour abundance. Relative crowding and interaction strength are derived independently, but when multiplied produce the commonly used relative competitive index, showing the biological underpinnings of the relative competition index in terms of crowding and strength of interaction. Since the new indices of relative crowding and interaction strength explicitly account for the amount of neighbour biomass, they serve as a valid method to track the effects of changing habitat conditions on the components of competition.
The new indices are applied to three published data sets. In each case, relative crowding increased with standing crop. In one case competition was reported as unchanged along a productivity gradient, whereas the new indices show that relative crowding and interaction strength both had significant patterns, but their effects were counteracting. These results do not fit current theories of competition. Further empirical studies are needed to see if competition theory needs revision.
Separating the mechanisms of competition into relative crowding and strength of interaction reveals previously hidden patterns that help bring to light underlying processes of competition along productivity gradients.
Obestatin – a ghrelin‐associated peptide that does not hold its promise to suppress food intake and motility
Authors: Gourcerol G. , Taché Y. 
Published: February 2007

Abstract  Ghrelin is a gut peptide well established to induce prokinetic and appetite stimulatory actions. Obestatin is a novel 23‐amino acid peptide derived from the processing of the ghrelin gene. The peptide name was in keeping with its initially reported actions to suppress food intake and digestive motility and to antagonize ghrelin's stimulatory effect through interaction with the orphan GPR‐39 receptor. However, subsequently, these findings have been questioned because obestatin actions to reduce food intake and to inhibit gastrointestinal (GI) motility in vivo and in vitro have not been reproduced by several groups. Furthermore, while GPR‐39 appears to be involved in gut motor functions, convergent reports showed that obestatin is not the cognate ligand for this receptor. In light of recent controversy over the effects of obestatin, the present findings from De Smet et al. provides additional evidence that obestatin does not influence food intake and GI motility in vivo and in vitro. Taken together, existing reports curtail the initial promise that obestatin is a new regulator of appetite and digestive motility. Therefore, it is proposed to rename obestatin as ghrelin‐associated peptide.
Effect of maternal asthma on birthweight and neonatal outcome in a British inner‐city population
Authors: Clark Julia M. , Hulme Emma , Devendrakumar Vijaya , Turner Mark A. , Baker Philip N. , Sibley Colin P. , D’Souza Stephen W. 
Published: February 2007

SummaryDuring pregnancy, asthma‐related alterations in placental function and the maternal immune system, and reduced growth affecting female but not male fetuses have been reported in a study of selected Australian women. The objective of this study was to evaluate the effect of asthma management, declared during pregnancy, on birthweight and neonatal outcome at an inner‐city hospital in England. Between June 2001 and December 2003, women at antenatal clinics were questioned about asthma (n = 10 983). Women with asthma and singleton uncomplicated pregnancies ending at term were selected (n = 718), with non‐asthmatic controls (n = 718).Among asthmatic women using inhaled steroids and bronchodilators (n = 170), 43% of the newborn boys had birthweights <10th centile, compared with 27% of controls (P = 0.011; OR 2.51 [95% CI: 1.52, 4.14]). For girls, the proportions were 28% and 27%. In women using bronchodilators only (n = 178) or those declaring no treatment (n = 370), birthweights were not significantly reduced. Taking account of smoking, ethnicity, gestational age and parity, there was a mean birthweight reduction with inhaled steroids and bronchodilators of 118 g [95% CI 36.0, 199.0 g] compared with the control group. There was no interaction between the effect of asthma treatment and infant gender. Infants of asthmatic women in the three subgroups who required intensive care were more likely to exhibit transient tachypnoea of the newborn than infants of control women (P < 0.005). In our population‐based sample, the risk of low birthweight among asthmatic women did not depend on infant gender, while neonatal respiratory morbidity remains a significant health issue in boys and girls.
Rates of caesarean section: analysis of global, regional and national estimates
Authors: Betrán Ana P. , Merialdi Mario , Lauer Jeremy A. , Bing‐Shun Wang , Thomas Jane , Van Look Paul , Wagner Marsden 
Published: February 2007

SummaryRates of caesarean section are of concern in both developed and developing countries. We set out to estimate the proportion of births by caesarean section (CS) at national, regional and global levels, describe regional and subregional patterns and correlate rates with other reproductive health indicators. We analysed nationally representative data available from surveys or vital registration systems on the proportion of births by CS. We used local non‐parametric regression techniques to correlate CS with maternal mortality ratio, infant and neonatal mortality rates, and the proportion of births attended by skilled health personnel. Although very unevenly distributed, 15% of births worldwide occur by CS. Latin America and the Caribbean show the highest rate (29.2%), and Africa shows the lowest (3.5%). In developed countries, the proportion of caesarean births is 21.1% whereas in least developed countries only 2% of deliveries are by CS. The analysis suggests a strong inverse association between CS rates and maternal, infant and neonatal mortality in countries with high mortality levels. There is some suggestion of a direct positive association at lower levels of mortality. CS levels may respond primarily to economic determinants.
A continuous‐scale measure of child development for population‐based epidemiological surveys: a preliminary study using Item Response Theory for the Denver Test
Authors: Drachler Maria de Lourdes , Marshall Tom , De Carvalho Leite José Carlos 
Published: February 2007

SummaryA method for translating research data from the Denver Test into individual scores of developmental status measured in a continuous scale is presented. It was devised using the Denver Developmental Screening Test (DDST) but can be used for Denver II. The DDST was applied in a community‐based survey of 3389 under‐5‐year‐olds in Porto Alegre, Brazil. The items of success were standardised by logistic regression on log chronological age. Each child’s ability age was then estimated by maximum likelihood as the age in this reference population corresponding to the child’s success and failures in the test. The score of developmental status is the natural logarithm of this ability age divided by chronological age and thus measures the delay or advance in the child’s ability age compared with chronological age. This method estimates development status using both difficulty and discriminating power of each item in the reference population, an advantage over scores based on total number of items correctly performed or failed, which depend on difficulty only. The score corresponds with maternal opinion of child developmental status and with the 3‐category scale of the DDST. It shows good construct validity, indicated by symmetrical and homogeneous variability from 3 months upwards, and reasonable results in describing gender differences in development by age, the mean score increasing with socio‐economic conditions and diminishing among low‐birthweight children. If a standardised measure of development status (z‐scores) is required, this can be obtained by dividing the score by its standard deviation. Concurrent and discriminant validity of the score must be examined in further studies.
Maternal sensitivity concerning aetiological research into childhood cancer: results of preliminary focus groups
Authors: Linet Martha S. , Byrne Julianne , Willis Gordon B. , Wacholder Sholom , Forman Michele R. 
Published: February 2007

SummaryWe and others have postulated that modifications to epidemiological methods and tools could improve understanding of childhood cancer aetiology. We describe features of paediatric cancer that influence study design and data collection strategies, and examine determinants of the reproducibility and accuracy of mothers' responses to questionnaires, which are the primary source of risk factor information. Two focus group sessions with mothers of children with acute lymphoblastic leukaemia (ALL) and two with mothers of children with brain tumours were conducted to explore: the optimal time of day, method of administration, and location for the interview; the availability of alternative data sources; the interval between paediatric cancer diagnosis and epidemiological interview; and other features which may affect maternal interview responses.Mothers of children with both types of cancer preferred being interviewed at home during the evening and were willing to provide complete access to their offsprings' medical records. Emotional, socio‐economic and perhaps cultural differences between the groups of mothers were exemplified by the willingness of mothers of children with ALL to participate in epidemiological interviews earlier in their child's treatment course and to provide greater access to maternal reproductive history records compared with mothers of children with brain tumours. Parental concerns about the difficult disease and treatment course of children with brain tumours were a key element in their decision to defer participating in epidemiological interviews for many months after their child's cancer diagnosis. We conclude that the focus group approach can contribute to a broad strategy for improving questionnaires and methods for conducting paediatric cancer epidemiological research.
Vaginal birth after caesarean delivery: does maternal age affect safety and success?
Authors: Srinivas Sindhu K. , Stamilio David M. , Sammel Mary D. , Stevens Erika J. , Peipert Jeffrey F. , Odibo Anthony O. , Macones George A. 
Published: February 2007

SummaryTo estimate maternal age effects on the rates of vaginal birth after caesarean delivery (VBAC), the related maternal complications and patient election to attempt VBAC, we conducted a secondary analysis of a retrospective cohort study of women who were offered VBAC from 1996 to 2000 in 17 community and university hospitals. We used bivariable and multivariable analyses to assess the association between maternal age and the study outcomes. A total of 25 005 patients were included, of whom 13 706 (54.81%) elected to attempt VBAC. After controlling for several confounding variables, using ages 21–34 years as the referent group, women aged 15–20 years were 27% less likely to have a failed VBAC attempt (OR = 0.73 [0.62, 0.87], P < 0.001). Analysing maternal age as a dichotomous variable, women who were of advanced maternal age (≥35 years) were more likely to experience an unsuccessful trial of labour (OR = 1.14 [1.03, 1.25], P = 0.009). In addition, women ≥35 years of age had 39% more risk of experiencing one of the VBAC‐related operative complications (OR = 1.39 [1.02, 1.89], P = 0.039). As women increase in age, they are less likely to attempt VBAC and more likely to have an unsuccessful labour trial. While teenage patients do not appear to be at increased risk for VBAC‐related complications, patients of advanced maternal age do show an increase in composite VBAC‐related operative complication rates.
Breast feeding and mental and motor development at 12 months in a low‐income population in northeast Brazil
Authors: Eickmann Sophie Helena , De Lira Pedro Israel Cabral , Lima Marilia de Carvalho , Coutinho Sonia Bechara , Teixeira Maria de Lourdes Perez Diaz , Ashworth Ann 
Published: February 2007

SummaryThe aim of this prospective study was to investigate the association between breast feeding and mental and motor development at age 12 months, controlling for comprehensive measures of the child's socio‐economic, maternal and environmental background, and nutritional status. A cohort of 205 infants born during May–August 2001 in a poor area in the interior of the State of Pernambuco was enrolled, of whom 191 were tested at age 12 months with the Bayley Scales of Infant Development II, and in whom breast‐feeding status was measured at days 1, 10, 30, 60, 90, 120, 150, 180, 270 and 360. After adjusting for potential confounders, full breast feeding (i.e. exclusive or predominant) at 1 month was associated with a small but significant benefit in mental development (+3.0 points, P = 0.02) compared with partial or no breast feeding. No additional advantage in mental development was found with longer durations of full breast feeding. Full breast feeding at 1 month was associated with improved behaviour for two of 10 ratings tested: initiative with tasks (P = 0.003) and attention (P = 0.02). No association between breast feeding and motor development was found.