bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flowers adaptively face down‐slope in 10 forest‐floor herbs
Authors: USHIMARU A. , KAWASE D. , IMAMURA A. 
Published: June 2006

Summary

An animal‐pollinated plant living on a slope should orientate its flowers down‐slope towards the more open space if by doing so it receives more pollinator visits and thereby achieves increased reproductive success.
We measured flower orientation relative to slope direction on individuals of 10 species of forest‐floor herbs in cool temperate forests in Japan. For one of these species, Erythronium japonicum, we also manipulated flower orientation to test experimentally for its effects on both male and female reproductive function.
In all 10 species, flowers were preferentially orientated down‐slope. This pattern was more pronounced in plants growing on steeper slopes.
Our manipulative field experiment in Erythronium japonicum demonstrated that pollen dispatch was highest in flowers orientated down‐slope. Additionally, flowers orientated up‐slope may have achieved a lower seed set on steep slopes.
We conclude that down‐slope orientation of flowers was a general phenomenon among the species that we studied, and that this behaviour was adaptive in enhancing plant fitness through pollination.
Population‐scale drivers of individual arrival times in migratory birds
Authors: GUNNARSSON TÓMAS G. , GILL JENNIFER A. , ATKINSON PHILIP W. , GÉLINAUD GUILLAUME , POTTS PETER M. , CROGER RUTH E. , GUDMUNDSSON GUDMUNDUR A. , APPLETON GRAHAM F. , SUTHERLAND WILLIAM J. 
Published: June 2006

Summary

In migratory species, early arrival on the breeding grounds can often enhance breeding success. Timing of spring migration is therefore a key process that is likely to be influenced both by factors specific to individuals, such as the quality of winter and breeding locations and the distance between them, and by annual variation in weather conditions before and during migration.
The Icelandic black‐tailed godwit Limosa limosa islandica population is currently increasing and, throughout Iceland, is expanding into poorer quality breeding areas. Using a unique data set of arrival times in Iceland in different years for individuals of known breeding and wintering locations, we show that individuals breeding in lower quality, recently occupied and colder areas arrive later than those from traditionally occupied areas. The population is also expanding into new wintering areas, and males from traditionally occupied winter sites also arrive earlier than those occupying novel sites.
Annual variation in timing of migration of individuals is influenced by large‐scale weather systems (the North Atlantic Oscillation), but between‐individual variation is a stronger predictor of arrival time than the NAO. Distance between winter and breeding sites does not influence arrival times.
Annual variation in timing of migration is therefore influenced by climatic factors, but the pattern of individual arrival is primarily related to breeding and winter habitat quality. These habitat effects on arrival patterns are likely to operate through variation in individual condition and local‐scale density‐dependent processes. Timing of migration thus appears to be a key component of the intricate relationship between wintering and breeding grounds in this migratory system.
Plant size and resprouting ability: trading tolerance and avoidance of damage?
Authors: VESK PETER A. 
Published: June 2006

Summary

Resprouting has been much studied in mature plants and seedlings, but with little attention to how resprouting ability may change with ontogeny in cross‐species datasets. Because damage exposure and avoidance through large size may differ between growth forms, size‐stage, growth form and disturbance type may interact.
A Bayesian mixed‐effects model was used to analyse a wide‐ranging literature dataset of resprouting responses following clipping or burning. There were distinct ontogenetic patterns of resprouting ability between growth forms. In ground‐dwelling plants, seedling resprouting ability was high and was maintained as plants grew. In trees, survivorship increased with size‐stage. However, for disturbances resulting in stem‐kill, resprouting ability of trees declined with increasing size.
The finding of distinct ontogenetic patterns of sprouting ability between growth forms demonstrates how species trade‐off damage avoidance with resprouting ability to achieve persistence, and provides an example of the life‐history trade‐off of avoidance and tolerance of damage.
Large random effects associated with between‐species variation indicated that although such ontogenetic patterns can be detected, each growth form contains species employing diverse strategies. Bayesian modelling enables flexible and powerful analyses of literature datasets, to reveal diverse strategies often obscured by classical analyses exploring only main effects.
Detecting introgressive hybridization between free‐ranging domestic dogs and wild wolves (Canis lupus) by admixture linkage disequilibrium analysis
Authors: VERARDI A. , LUCCHINI V. , RANDI E. 
Published: June 2006

AbstractOccasional crossbreeding between free‐ranging domestic dogs and wild wolves (Canis lupus) has been detected in some European countries by mitochondrial DNA sequencing and genotyping unlinked microsatellite loci. Maternal and unlinked genomic markers, however, might underestimate the extent of introgressive hybridization, and their impacts on the preservation of wild wolf gene pools. In this study, we genotyped 220 presumed Italian wolves, 85 dogs and 7 known hybrids at 16 microsatellites belonging to four different linkage groups (plus four unlinked microsatellites). Population clustering and individual assignments were performed using a Bayesian procedure implemented in structure 2.1, which models the gametic disequilibrium arising between linked loci during admixtures, aiming to trace hybridization events further back in time and infer the population of origin of chromosomal blocks. Results indicate that (i) linkage disequilibrium was higher in wolves than in dogs; (ii) 11 out of 220 wolves (5.0%) were likely admixed, a proportion that is significantly higher than one admixed genotype in 107 wolves found previously in a study using unlinked markers; (iii) posterior maximum‐likelihood estimates of the recombination parameter r revealed that introgression in Italian wolves is not recent, but could have continued for the last 70 (± 20) generations, corresponding to approximately 140–210 years. Bayesian clustering showed that, despite some admixture, wolf and dog gene pools remain sharply distinct (the average proportions of membership to wolf and dog clusters were Qw = 0.95 and Qd = 0.98, respectively), suggesting that hybridization was not frequent, and that introgression in nature is counteracted by behavioural or selective constraints.
Tracking factors modulating cytoplasmic incompatibilities in the mosquito Culex pipiens
Authors: DURON OLIVIER , BERNARD CLOTILDE , UNAL SANDRA , BERTHOMIEU ARNAUD , BERTICAT CLAIRE , WEILL MYLÈNE 
Published: June 2006

Abstract Wolbachia are maternally inherited endosymbiotic bacteria that infect many arthropod species and may induce cytoplasmic incompatibility (CI), resulting in abortive embryonic development. One Wolbachia host, Culex pipiens complex mosquitoes, displays high levels of variability in both CI crossing types (cytotypes) and DNA markers. We report here an analysis of 14 mosquito strains, containing 13 Wolbachia variants, and with 13 different cytotypes. Cytotypes were Wolbachia‐dependent, as antibiotic treatment rendered all strains tested compatible. Cytotype distributions were independent of geographical distance between sampling sites and host subspecies, suggesting that Wolbachia does not promote a reproductive isolation depending on these parameters. Backcross analysis demonstrated a mild restoring effect of the nuclear genome, indicating that CI is mostly cytoplasmically determined for some crosses. No correlation was found between the phenotypic and genotypic variability of 16 WO prophage and transposon markers, except for the WO prophage Gp15 gene, which encodes a protein similar to a bacterial virulence factor. However, Gp15 is partially correlated with CI expression, suggesting that it could be just linked to a CI gene.
Jasmonic acid signalling and herbivore resistance traits constrain regrowth after herbivore attack in Nicotiana attenuata
Authors: ZAVALA JORGE A. , BALDWIN IAN T. 
Published: June 2006

ABSTRACTBecause traits conferring resistance on herbivores can reduce fitness‐associated traits, trade‐offs may occur between tolerance and resistance responses. We examined these trade‐offs in genotypes of Nicotiana attenuata that were transformed to silence trypsin proteinase inhibitor (TPI) production (AS‐Natpi), an antiherbivore defense associated with (14%) reductions in seed production, and the jasmonate signal cascade that elicits these defenses (AS‐Nalox3), by measuring stalk and axillary branch growth and seed production after two defoliation regimes and Manduca sexta larval attack to bottom or middle and top stalk leaves. Larval attack and defoliation at middle and top leaves depressed seed production and increased axillary branching more than at bottom leaves. AS‐Nalox3 and AS‐Natpi plants produced significantly longer (two‐ to fourfold) branches than did wild‐type (WT) plants, results that are consistent with resource‐based trade‐offs between resistance and regrowth. Methyl jasmonate (MeJA) treatment of AS‐Nalox3 plants restored WT branch growth, suggesting that jasmonic acid (JA) signalling suppresses regrowth and contributes to apical dominance. These results are consistent with the existence of JA‐ and resource‐mediated trade‐offs between regrowth and herbivore resistance traits.
A whole‐tree chamber system for examining tree‐level physiological responses of field‐grown trees to environmental variation and climate change
Authors: MEDHURST JANE , PARSBY JAN , LINDER SUNE , WALLIN GÖRAN , CESCHIA ERIC , SLANEY MICHELLE 
Published: June 2006

ABSTRACTA whole‐tree chamber (WTC) system was installed at Flakaliden in northern Sweden to examine the long‐term physiological responses of field‐grown 40‐year‐old Norway spruce trees [Picea abies (L.) Karst.] to climate change. The WTCs were designed as large cuvettes to allow the net tree‐level CO2 and water fluxes to be measured on a continuous basis. A total of 12 WTCs were used to impose combinations of atmospheric carbon dioxide concentration, [CO2], and air temperature treatments. The air inside the ambient and elevated [CO2] WTCs was maintained at 365 and 700 µmol mol−1, respectively. The air temperature inside the ambient temperature WTCs tracked air temperature outside the WTCs. Elevated temperatures were altered on a monthly time‐step and ranged between +2.8 and +5.6 °C above ambient temperature. The system allowed continuous, long‐term measurement of whole‐tree photosynthesis, night‐time respiration and transpiration. The performance of the WTCs was assessed using winter and spring data sets. The ability of the WTC system to measure tree‐level physiological responses is demonstrated. All WTCs displayed a high level of control over tracking of air temperatures. The set target of 365 µmol mol−1 in the ambient [CO2] chambers was too low to be maintained during winter because of tree dormancy and the high natural increase in [CO2] over winter at high latitudes such as the Flakaliden site. Accurate control over [CO2] in the ambient [CO2] chambers was restored during the spring and the system maintained the elevated [CO2] target of 700 µmol mol−1 for both measurement periods. Air water vapour deficit (VPD) was accurately tracked in ambient temperature WTCs. However, as water vapour pressure in all 12 WTCs was maintained at the level of non‐chambered (reference) air, VPD of elevated temperature WTCs was increased.
Are ABA, ethylene or their interaction involved in the response of leaf growth to soil water deficit? An analysis using naturally occurring variation or genetic transformation of ABA production in maize
Authors: VOISIN ANNE‐SOPHIE , REIDY BEAT , PARENT BORIS , ROLLAND GAËLLE , REDONDO ELISE , GERENTES DENISE , TARDIEU FRANÇOIS , MULLER BERTRAND 
Published: June 2006

ABSTRACTThe role of abscisic acid (ABA) and its possible interaction with ethylene in mediating leaf elongation response to soil water deficit are a matter of controversy. To address this question, we used a set of maize genotypes with various levels of ABA either due to natural variability or to genetic transformation targeted on NCED/VP14, a key enzyme of ABA synthesis. The transgenic lines yielded less strong phenotypes than available mutants, making it possible to use them under normal growing conditions. We focused on leaf elongation during night periods in order to avoid the confounding effect of ABA on leaf water status. Our results suggest that over a wide range, internal ABA level (measured in both leaf extracts or xylem sap) has no clear effect on leaf elongation response to soil water deficit, except in the case of an antisense line presenting the strongest reduction in ABA accumulation that showed a slight maintenance of leaf elongation during water deficit. Leaf ethylene production rate was variable and not related to water deficit except in the ABA‐deficient transgenic lines where it was increased by water deficit on average but not systematically. Moreover, variability in ethylene production rate was not linked to variability in elongation rate. Our results thus suggest that neither ABA nor ethylene seems to play a major role in the control of leaf elongation response to soil water deficit.
Contrasting patterns of body shape and neutral genetic divergence in marine and lake populations of threespine sticklebacks
Authors: Leinonen T. , Cano J. M. , Mäkinen H. , Merilä J. 
Published: June 2006

Abstract
Comparisons of neutral marker and quantitative trait divergence can provide important insights into the relative roles of natural selection and neutral genetic drift in population differentiation. We investigated phenotypic and genetic differentiation among Fennoscandian threespine stickleback (Gasterosteus aculeatus) populations, and found that the highest degree of differentiation occurred between sea and freshwater habitats. Within habitats, morphological divergence was highest among the different freshwater populations. Pairwise phenotypic and neutral genetic distances among populations were positively correlated, suggesting that genetic drift may have contributed to the morphological differentiation among habitats. On the other hand, the degree of phenotypic differentiation (PST) clearly surpassed the neutral expectation set by FST, suggesting a predominant role for natural selection over genetic drift as an explanation for the observed differentiation. However, separate PST/FST comparisons by habitats revealed that body shape divergence between lake and marine populations, and even among marine populations, can be strongly influenced by natural selection. On the other hand, genetic drift can play an important role in the differentiation among lake populations.
Effects of acute and chronic restraint stress on visceral sensitivity and neuroendocrine hormones in rats
Authors: SUN Yan , LIU Feng Ling , SONG Geng Qing , QIAN Wei , HOU Xiao Hua 
Published: June 2006

OBJECTIVE:  To investigate the effects of acute and chronic partial restraint stress (PRS) on visceral sensi‐tivity to colorectal distention and the neuroendocrine response in rats.METHODS:  Male Sprague–Dawley rats were used in this study. The abdominal withdrawal reflex score was assessed before stress, immediately after acute or chronic PRS, and 7 days after the first stress. The plasma levels of corticosterone (CORT) and adrenocorticotropic hormone (ACTH) were detected by radioimmunoassay at different time points.RESULTS:  The abdominal withdrawal reflex scores of the rats with acute or chronic PRS were significantly higher immediately after stress than those before and 7 days after the stress (P < 0.05). The levels of CORT (25.35 ± 6.03 ng/mL) and ACTH (312.47 ± 50.76 pg/mL) in rats with acute PRS showed a significant elevation immediately after stress compared to rats without PRS (7.24 ± 2.97 ng/mL, 97.00 ± 23.33 pg/mL, P < 0.05). However, these hormones returned to the baseline value 7 days after acute PRS. The levels of CORT (20.84 ± 2.19 ng/mL) and ACTH (200.41 ± 78.10 pg/mL) in rats with chronic PRS were significantly higher after stress than in rats without PRS (P < 0.05), and these hormones remained elevated 7 days after chronic PRS.CONCLUSIONS:  Both acute and chronic PRS induce reversible visceral hypersensitivity. Acute PRS transiently elevates the plasma levels of CORT and ACTH, whereas chronic PRS has a longer term effect.
Novel lipids in Myxococcus xanthus and their role in chemotaxis
Authors: Curtis Patrick D. , Geyer Roland , White David C. , Shimkets Lawrence J. 
Published: June 2006

SummaryOrganisms that colonize solid surfaces, like Myxococcus xanthus, use novel signalling systems to organize multicellular behaviour. Phosphatidylethanolamine (PE) containing the fatty acid 16:1ω5 (Δ11) elicits a chemotactic response. The phenomenon was examined by observing the effects of PE species with varying fatty acid pairings. Wild‐type M. xanthus contains 17 different PE species under vegetative conditions and 19 at the midpoint of development; 13 of the 17 have an unsaturated fatty acid at the sn‐1 position, a novelty among Proteobacteria. Myxococcus xanthus has two glycerol‐3‐phosphate acyltransferase (PlsB) homologues which add the sn‐1 fatty acid. Each produces PE with 16:1 at the sn‐1 position and supports growth and fruiting body development. Deletion of plsB1 (MXAN3288) results in more dramatic changes in PE species distribution than deletion of plsB2 (MXAN1675). PlsB2 has a putative N‐terminal eukaryotic fatty acid reductase domain and may support both ether lipid synthesis and PE synthesis. Disruption of a single sn‐2 acyltransferase homologue (PlsC, of which M. xanthus contains five) results in minor changes in membrane PE. Derivatization of purified PE extracts with dimethyldisulfide was used to determine the position of the double bonds in unsaturated fatty acids. The results suggest that Δ5 and Δ11 desaturases may create the double bonds after synthesis of the fatty acid. Phosphatidylethanolamine enriched for 16:1 at the sn‐1 position stimulates chemotaxis more strongly than PE with 16:1 enriched at the sn‐2 position. It appears that the deployment of a rare fatty acid (16:1ω5) at an unusual position (sn‐1) has facilitated the evolution of a novel cell signal.
APPLICATION OF LAPLACE'S BOUNDARY‐MODE APPROXIMATIONS TO ESTIMATE SPECIES AND SHARED SPECIES RICHNESS
Authors: Chao Anne , Shen Tsung‐Jen , Hwang Wen‐Han 
Published: June 2006

SummaryThe Laplace method for approximating integrals is a useful technique in a number of research fields. This paper shows that it also has interesting applications in biological and ecological statistical inferences. When sample abundance or replicated incidence (i.e., presence or absence) records of each species are available, the expected low‐order frequency counts in heterogeneous communities can be approximated by the Laplace method when the species discovery or detection probabilities are bounded from below by a constant. The approximation formulae as applied to one community can then be used to derive estimators of species richness and to examine their performance. The approach is also extended to obtain simple and new estimators for the number of shared species in two communities. The replicated species incidence data recorded by competing teams of the Hong Kong Big Bird Race for the years 1999 and 2000 are used to estimate the number of resident birds in Hong Kong and to illustrate the method of estimation.
BOOTSTRAP TESTS FOR THE ERROR DISTRIBUTION IN LINEAR AND NONPARAMETRIC REGRESSION MODELS
Authors: Neumeyer Natalie , Dette Holger , Nagel Eva‐Renate 
Published: June 2006

SummaryIn this paper we investigate several tests for the hypothesis of a parametric form of the error distribution in the common linear and non‐parametric regression model, which are based on empirical processes of residuals. It is well known that tests in this context are not asymptotically distribution‐free and the parametric bootstrap is applied to deal with this problem. The performance of the resulting bootstrap test is investigated from an asymptotic point of view and by means of a simulation study. The results demonstrate that even for moderate sample sizes the parametric bootstrap provides a reliable and easy accessible solution to the problem of goodness‐of‐fit testing of assumptions regarding the error distribution in linear and non‐parametric regression models.
A BAYESIAN HIERARCHICAL MODEL FOR POISSON RATE AND REPORTING‐PROBABILITY INFERENCE USING DOUBLE SAMPLING
Authors: Stamey James D. , Young Dean M. , Boese Doyle 
Published: June 2006

SummaryWe analyse a combination of errant count data subject to under‐reported counts and inerrant count data to estimate multiple Poisson rates and reporting probabilities of cervical cancer for four European countries. Our analysis uses a Bayesian hierarchical model. Using a simulation study, we demonstrate the efficacy of our new simultaneous inference method and compare the utility of our method with an empirical Bayes approach developed by Fader and Hardie (J. Appl. Statist., 2000).
BAYESIAN SUBSET SELECTION AND MODEL AVERAGING USING A CENTRED AND DISPERSED PRIOR FOR THE ERROR VARIANCE
Authors: Cripps Edward , Kohn Robert , Nott David 
Published: June 2006

SummaryThis article proposes a new data‐based prior distribution for the error variance in a Gaussian linear regression model, when the model is used for Bayesian variable selection and model averaging. For a given subset of variables in the model, this prior has a mode that is an unbiased estimator of the error variance but is suitably dispersed to make it uninformative relative to the marginal likelihood. The advantage of this empirical Bayes prior for the error variance is that it is centred and dispersed sensibly and avoids the arbitrary specification of hyperparameters. The performance of the new prior is compared to that of a prior proposed previously in the literature using several simulated examples and two loss functions. For each example our paper also reports results for the model that orthogonalizes the predictor variables before performing subset selection. A real example is also investigated. The empirical results suggest that for both the simulated and real data, the performance of the estimators based on the prior proposed in our article compares favourably with that of a prior used previously in the literature.
SECOND ORDER ASYMPTOTIC COMPARISON OF ESTIMATORS UNDER UNIVERSAL DOMINATION CRITERION
Authors: Takagi Yoshiji 
Published: June 2006

SummaryThe main purpose of this paper is to formulate theories of universal optimality, in the sense that some criteria for performances of estimators are considered over a class of loss functions. It is shown that the difference of the second order terms between two estimators in any risk functions is expressed as a form which is characterized by a peculiar value associated with the loss functions, which is referred to as the loss coefficient. This means that the second order optimal problem is completely characterized by the value of the loss coefficient. Furthermore, from the viewpoint of change of the loss coefficient, the relationship between two estimators is classified into six types. On the basis of this classification, the concept of universal second order admissibility is introduced. Some sufficient conditions are given to determine whether any estimators are universally admissible or not.