bluuebunny/crossref_metadata_2025_split huggingface dataset:
Trade‐offs in resource allocation that favour resprouting affect the competitive ability of woody seedlings in grassy communities
Authors: Clarke Peter J. , Knox Kirsten J. E. 
Published: August 2009

Summary 1.  Differences in the competitive ability of plant functional groups at early life‐history stages can have important consequences for community structure. In particular, trade‐offs in allocation to roots by woody plant seedlings may influence competitive ability with grasses in fire‐prone vegetation. 2.
We followed post‐fire survival of seedlings of facultative resprouter and obligate seeder (fire‐killed) shrubs for 3 years in adjacent communities with a grassy/graminoid ground stratum (54 plots, 20 m2) or a non‐graminoid ground stratum (54 plots, 20 m2). 3.
The competitive effect of a grass (Poa) on seedlings of three congeneric pairs of resprouters and obligate seeder shrubs was tested in a factorial experiment where nutrients and the grass competitor were manipulated. The effects of grass (+,−) and nutrients (+,−) on the growth response, biomass allocation and root carbohydrate storage were measured after harvest at 26 weeks and the relative neighbour effect calculated. 4.  Post‐fire shrub seedling survival was high with about 50% (2163 seedlings) surviving over 3 years, but this varied between habitats and functional groups. In the grassy/graminoid ground layer communities 27% of shrub seedlings survived, whereas in the habitats with a more open ground stratum 55% of seedlings survived. In grassy habitats, obligate seeder survival was lower (23% survival) than that of resprouter seedlings (35% survival). Similarly, in open habitats, obligate seeder seedling survival was lower (51%) than that of resprouter seedlings (64% survival). 5.  Growth of both resprouters and obligate seeders in our manipulative experiment was strongly reduced in the presence of a grass competitor. Moreover, the addition of nutrients increased the relative difference in mass and height between those seedlings exposed to a grass competitor and those grown without a competitor. Resprouter species allocated more to roots under competition and were less affected by grass competition than obligate seeders. 6.
Synthesis. The results of seedling survival and of the experiment on the effects of grass competition on woody plant seedlings suggest that early life‐history trade‐offs in allocation influence seedling survival. Allocation to resprouting appears to enhance the ability of shrub seedlings to survive grass competition. We propose that grass competition across productivity gradients plays an important role in influencing landscape‐level distribution patterns of woody resprouters.
Towards a new paradigm in mayfly phylogeny (Ephemeroptera): combined analysis of morphological and molecular data
Authors: OGDEN T.H. , GATTOLLIAT J. L. , SARTORI M. , STANICZEK A.H. , SOLDÁN T. , WHITING M.F. 
Published: August 2009

Abstract.This study represents the first formal morphological and combined (morphological and molecular) phylogenetic analyses of the order Ephemeroptera. Taxonomic sampling comprised 112 species in 107 genera, including 42 recognized families (all major lineages of Ephemeroptera). Morphological data consisted of 101 morphological characters. Molecular data were acquired from DNA sequences of the 12S, 16S, 18S, 28S and H3 genes. The Asian genusSiphluriscus(Siphluriscidae) was supported as sister to all other mayflies. The lineages Carapacea, Furcatergalia, Fossoriae, Pannota, Caenoidea and Ephemerelloidea were supported as monophyletic, as were many of the families. However, some recognized families (for example, Ameletopsidae and Coloburiscidae) and major lineages (such as Setisura, Pisciforma and Ephemeroidea among others) were not supported as monophyletic, mainly due to convergences within nymphal characters. Clade robustness was evaluated by multiple methods and approaches.
Seed dormancy dynamics and germination characteristics of Solanum nigrum
Authors: TAAB A , ANDERSSON L 
Published: August 2009

SummaryFour experiments were conducted to study seed dormancy and germination requirements in Solanum nigrum. In Expt 1, seeds were stratified at different constant and stepwise rising temperatures and their germinability was tested at three germination regimes at weekly intervals. In Expts 2–4, seeds dry stored at 4°C and stratified at 5 and 15°C were tested at constant temperatures, as well as fluctuating temperatures with constant and increasing amplitudes. Results suggest that the rate of dormancy release increased with increasing temperatures ranging from 4.5 to 18.6°C. However, prolonged stratification at higher temperatures caused subsequent induction of dormancy. When tested at constant temperatures, stratified seeds germinated between 18 and 34°C, with the optimum between 26 and 30°C, while dry‐stored seeds showed no germination. Fluctuating temperatures, with amplitudes ranging from 5 to 15°C, promoted germination of seeds from all treatments. The dormancy dynamics and germination characteristics of the species will have implications for its survival and establishment. This information can be used to predict time of emergence and, thus, improve control of the species in weed management systems.
Comparative anatomy and phylogenetic distribution of the mammalian cecal appendix
Authors: SMITH H. F. , FISHER R. E. , EVERETT M. L. , THOMAS A. D. , RANDAL BOLLINGER R. , PARKER W. 
Published: August 2009

AbstractA recently improved understanding of gut immunity has merged with current thinking in biological and medical science, pointing to an apparent function of the mammalian cecal appendix as a safe‐house for symbiotic gut microbes, preserving the flora during times of gastrointestinal infection in societies without modern medicine. This function is potentially a selective force for the evolution and maintenance of the appendix, and provides an impetus for reassessment of the evolution of the appendix. A comparative anatomical approach reveals three apparent morphotypes of the cecal appendix, as well as appendix‐like structures in some species that lack a true cecal appendix. Cladistic analyses indicate that the appendix has evolved independently at least twice (at least once in diprotodont marsupials and at least once in Euarchontoglires), shows a highly significant (P < 0.0001) phylogenetic signal in its distribution, and has been maintained in mammalian evolution for 80 million years or longer.
Stratified bacterial community in the bladder of the medicinal leech, Hirudo verbana
Authors: Kikuchi Yoshitomo , Bomar Lindsey , Graf Joerg 
Published: August 2009

SummaryMost animals harbour symbiotic microorganisms inside their body, where intimate interactions occur between the partners. The medicinal leech, Hirudo verbana, possesses 17 pairs of excretory bladders that harbour a large number of intracellular and extracellular symbiotic bacteria. In this study, we characterized the bladder symbionts using molecular phylogenetic analyses, transmission electron microscopy (TEM) and fluorescence in situ hybridization (FISH). Restriction fragment length polymorphism (RFLP) and sequence analyses of 16S rRNA gene clone libraries suggested that six bacterial species co‐colonize the leech bladders. Phylogenetic analyses revealed that these species belong to the α‐Proteobacteria (Ochrobactrum symbiont), β‐Proteobacteria (Beta‐1 and Beta‐2 symbionts), δ‐Proteobacteria (Bdellovibrio symbiont) and Bacteroidetes (Niabella and Sphingobacterium symbionts). Species‐specific PCR detection and FISH confirmed the localization of the symbiotic bacteria in the bladders. The Ochrobactrum, Beta‐1, Bdellovibrio and Sphingobacterium symbionts were consistently detected in 13 leeches from two populations, while infection rate of the other symbionts ranged between 20% and 100% in the two leech populations. Transmission electron microscopy observations of the bladders revealed epithelial cells harbouring a number of intracellular bacilli and an additional type of extracellular, rod‐shaped bacteria in the luminal region. Fluorescence in situ hybridization with group‐specific oligonucleotide probes revealed the spatial organization of the bacterial species in the bladder: the Ochrobactrum symbiont was located intracellularly inside epithelial cells; the Bacteroidetes were localized close to the epithelium in the lumen of the bladder; and the Bacteroidetes layer was covered with dense β‐proteobacterial cells. These results clearly demonstrate that a simple but organized microbial community exists in the bladder of the medicinal leech.
Eukaryotic diversity and phylogeny using small‐ and large‐subunit ribosomal RNA genes from environmental samples
Authors: Marande William , López‐García Purificación , Moreira David 
Published: August 2009

SummaryThe recent introduction of molecular techniques in eukaryotic microbial diversity studies, in particular those based in the amplification and sequencing of small‐subunit ribosomal DNA (SSU rDNA), has revealed the existence of an unexpected variety of new phylotypes. The taxonomic ascription of the organisms bearing those sequences is generally deduced from phylogenetic analysis. Unfortunately, the SSU rDNA sequence alone has often not enough phylogenetic information to resolve the phylogeny of fast‐evolving or very divergent sequences, leading to their misclassification. To address this problem, we tried to increase the phylogenetic signal by amplifying the complete eukaryotic rDNA cluster [i.e. the SSU rDNA, the internal transcribed spacers, the 5.8S rDNA and the large‐subunit (LSU) rDNA] from environmental samples, and sequencing the SSU and LSU rDNA part of the clones. Using marine planktonic samples, we showed that surveys based on either SSU or SSU + LSU rDNA retrieved comparable diversity patterns. In addition, phylogenetic trees based on the concatenated SSU + LSU rDNA sequences showed better resolution, yielding good support for major eukaryotic groups such as the Opisthokonta, Rhizaria and Excavata. Finally, highly divergent SSU rDNA sequences, whose phylogenetic position was impossible to determine with the SSU rDNA data alone, could be placed correctly with the SSU + LSU rDNA approach. These results suggest that this method can be useful, in particular for the analysis of eukaryotic microbial communities rich in phylotypes of difficult phylogenetic ascription.
Biofilms: the environmental playground of Legionella pneumophila
Authors: Declerck Priscilla 
Published: August 2009

Summary Legionella pneumophila, the aetiological agent of 90% of legionellosis cases, is a common inhabitant of natural and anthropogenic freshwater environments, where it resides in biofilms. Biofilms are defined as complex, natural assemblages of microorganisms that involve a multitude of trophic interactions. A thorough knowledge and understanding of Legionella ecology in relation to biofilm communities is of primary importance in the search for innovative and effective control strategies to prevent the occurrence of disease cases. This review provides a critical update on the state‐of‐the‐art progress in understanding the mechanisms and factors affecting the biofilm life cycle of L. pneumophila. Particular emphasis is given to discussing the different strategies this human pathogen uses to grow and retain itself in biofilm communities. Biofilms develop not only at solid‐water interfaces (substrate‐associated biofilms), but also at the water‐air interface (floating biofilms). Disturbance of the water surface can lead to liberation of aerosols derived from the floating biofilm into the atmosphere that allow transmission of biofilm‐associated pathogens over considerable distances. Recent data concerning the occurrence and replication of L. pneumophila in floating biofilms are also elaborated and discussed.
Acquisitions and Real Options: The Greenfield Alternative
Authors: Brouthers Keith D. , Dikova Desislava 
Published: August 2009

abstract Although acquisitions are a popular way to enter new markets, empirical evidence tends to indicate few benefits accrue to acquiring firms. This might be the case because firms use acquisitions when they should be employing an alternative mode of expansion. Applying real options theory to this issue, we suggest that greenfield start‐up ventures provide a real option alternative to acquisitions for firms establishing new international subsidiary units. To test this notion we examine a sample of Western European firms entering the emerging economies of Eastern Europe. The evidence suggests that acquisitions are a good choice only when firms enter markets containing low demand uncertainty and when these firms possess acquisition‐based strategic flexibility. Overall, our analysis indicates that greenfield ventures appear to provide firms with a real option when making the acquisition decision.
How is phonological processing related to individual differences in children’s arithmetic skills?
Authors: De Smedt Bert , Taylor Jessica , Archibald Lisa , Ansari Daniel 
Published: August 2009

AbstractWhile there is evidence for an association between the development of reading and arithmetic, the precise locus of this relationship remains to be determined. Findings from cognitive neuroscience research that point to shared neural correlates for phonological processing and arithmetic as well as recent behavioral evidence led to the present hypothesis that there exists a highly specific association between phonological awareness and single‐digit arithmetic with relatively small problem sizes. The present study examined this association in 37 typically developing fourth and fifth grade children. Regression analyses revealed that phonological awareness was specifically and uniquely related to arithmetic problems with a small but not large problem size. Further analysis indicated that problems with a high probability of being solved by retrieval, but not those typically associated with procedural problem‐solving strategies, are correlated with phonological awareness. The specific association between phonological awareness and arithmetic problems with a small problem size and those for which a retrieval strategy is most common was maintained even after controlling for general reading ability and phonological short‐term memory. The present findings indicate that the quality of children’s long‐term phonological representations mediates individual differences in single‐digit arithmetic, suggesting that more distinct long‐term phonological representations are related to more efficient arithmetic fact retrieval.
The interaction between acoustic salience and language experience in developmental speech perception: evidence from nasal place discrimination
Authors: Narayan Chandan R. , Werker Janet F. , Beddor Patrice Speeter 
Published: August 2009

AbstractPrevious research suggests that infant speech perception reorganizes in the first year: young infants discriminate both native and non‐native phonetic contrasts, but by 10–12 months difficult non‐native contrasts are less discriminable whereas performance improves on native contrasts. In the current study, four experiments tested the hypothesis that, in addition to the influence of native language experience, acoustic salience also affects the perceptual reorganization that takes place in infancy. Using a visual habituation paradigm, two nasal place distinctions that differ in relative acoustic salience, acoustically robust labial‐alveolar [ma]–[na] and acoustically less salient alveolar‐velar [na]–[ŋa], were presented to infants in a cross‐language design. English‐learning infants at 6–8 and 10–12 months showed discrimination of the native and acoustically robust [ma]–[na] (Experiment 1), but not the non‐native (in initial position) and acoustically less salient [na]–[ŋa] (Experiment 2). Very young (4–5‐month‐old) English‐learning infants tested on the same native and non‐native contrasts also showed discrimination of only the [ma]–[na] distinction (Experiment 3). Filipino‐learning infants, whose ambient language includes the syllable‐initial alveolar (/n/)–velar (/ŋ/) contrast, showed discrimination of native [na]–[ŋa] at 10–12 months, but not at 6–8 months (Experiment 4). These results support the hypothesis that acoustic salience affects speech perception in infancy, with native language experience facilitating discrimination of an acoustically similar phonetic distinction [na]–[ŋa]. We discuss the implications of this developmental profile for a comprehensive theory of speech perception in infancy.
Categorization, categorical perception, and asymmetry in infants’ representation of face race
Authors: Anzures Gizelle , Quinn Paul C. , Pascalis Olivier , Slater Alan M. , Lee Kang 
Published: August 2009

AbstractThe present study examined whether 6‐ and 9‐month‐old Caucasian infants could categorize faces according to race. In Experiment 1, infants were familiarized with different female faces from a common ethnic background (i.e. either Caucasian or Asian) and then tested with female faces from a novel race category. Nine‐month‐olds were able to form discrete categories of Caucasian and Asian faces. However, 6‐month‐olds did not form discrete categories of faces based on race. In Experiment 2, a second group of 6‐ and 9‐month‐olds was tested to determine whether they could discriminate between different faces from the same race category. Results showed that both age groups could only discriminate between different faces from the own‐race category of Caucasian faces. The findings of the two experiments taken together suggest that 9‐month‐olds formed a category of Caucasian faces that are further differentiated at the individual level. In contrast, although they could form a category of Asian faces, they could not discriminate between such other‐race faces. This asymmetry in category formation at 9 months (i.e. categorization of own‐race faces vs. categorical perception of other‐race faces) suggests that differential experience with own‐ and other‐race faces plays an important role in infants’ acquisition of face processing abilities.
Using innate visual biases to guide face learning in natural scenes: a computational investigation
Authors: Balas Benjamin 
Published: August 2009

AbstractNewborn infants appear to possess an innate bias that guides preferential orienting to and tracking of human faces. There is, however, no clear agreement as to the underlying mechanism supporting such a preference. In particular, two competing theories (known as the ‘structural’ and ‘sensory’ hypotheses) conjecture fundamentally different biasing mechanisms to explain this behavior. The structural hypothesis suggests that a crude ‘3‐dot’ representation of face‐specific geometry is responsible for the exhibited preference. By contrast, the sensory hypothesis suggests that face preference is the product of several generic visual preferences for qualities like dark/light vertical asymmetry, horizontal symmetry, and high contrast. To complement existing empirical results, the current study describes a computational investigation of how well both proposals actually support face detection in cluttered natural scenes. The results demonstrate that both models are capable of locating faces effectively, but that the model suggested by the ‘sensory hypothesis’ is more selective than the model suggested by the ‘structural hypothesis’.
Monolingual, bilingual, trilingual: infants' language experience influences the development of a word‐learning heuristic
Authors: Byers‐Heinlein Krista , Werker Janet F. 
Published: August 2009

AbstractHow infants learn new words is a fundamental puzzle in language acquisition. To guide their word learning, infants exploit systematic word‐learning heuristics that allow them to link new words to likely referents. By 17 months, infants show a tendency to associate a novel noun with a novel object rather than a familiar one, a heuristic known as disambiguation. Yet, the developmental origins of this heuristic remain unknown. We compared disambiguation in 17‐ to 18‐month‐old infants from different language backgrounds to determine whether language experience influences its development, or whether disambiguation instead emerges as a result of maturation or social experience. Monolinguals showed strong use of disambiguation, bilinguals showed marginal use, and trilinguals showed no disambiguation. The number of languages being learned, but not vocabulary size, predicted performance. The results point to a key role for language experience in the development of disambiguation, and help to distinguish among theoretical accounts of its emergence.
The emergence of a novel representation from action: evidence from preschoolers
Authors: Boncoddo Rebecca , Dixon James A. , Kelley Elizabeth 
Published: August 2009

AbstractRecent work in embodied cognition has proposed that representations and actions are inextricably linked. The current study examines a developmental account of this relationship. Specifically, we propose that children’s actions are foundational for novel representations. Thirty‐two preschoolers, aged 3.4 to 5.7 years, were asked to solve a set of simple gear‐system problems. Participants’ motions and verbalizations were coded to establish the strategies they used. The preschoolers initially solved the problems by simulating the turning and pushing of the gears. Subsequently, most participants discovered a new representation of the problems: the turning direction of the gears alternates. Results show that the number of actions that embodied alternation information, during their simulation of the system, predicted the later emergence of the higher‐order representation (i.e. that the gears alternate turning direction). Thus, it appears that the preschoolers discovered a new representation based on their own actions. These results are consistent with the developmental embodiment hypothesis: actions are central to the emergence of new representations.
A NEW CONFIDENCE BAND FOR CONTINUOUS CUMULATIVE DISTRIBUTION FUNCTIONS
Authors: Xu Xingzhong , Ding Xiaobo , Zhao Shuran 
Published: August 2009

SummaryWe consider confidence bands for continuous distribution functions. Following a review of the literature we find that previously considered confidence bands, which have exact coverage, are all step‐functions jumping only at the sample points. We find that the step‐function bands can be constructed through rectangular tolerance regions for an ordered sample from the uniform distribution R(0, 1). We then construct a set of new bands. Two criteria for assessing confidence bands are presented. One is the power criterion, and the other is the average‐width criterion that we propose. Numerical comparisons between our new bands and the old bands are carried out, and show that our new bands perform much better than the old ones.
What is Strong Correlation?
Authors: Kozak Marcin 
Published: August 2009

SummaryInterpretation of correlation is often based on rules of thumb in which some boundary values are given to help decide whether correlation is non‐important, weak, strong or very strong. This article shows that such rules of thumb may do more harm than good, and instead of supporting interpretation of correlation – which is their aim – they teach a schematic approach to statistics. Therefore they should be avoided in a statistics course.