bluuebunny/crossref_metadata_2025_split huggingface dataset:
Long‐term assessment of seed limitation in plants: results from an 11‐year experiment
Authors: EHRLÉN JOHAN , MÜNZBERGOVA ZUZANA , DIEKMANN MARTIN , ERIKSSON OVE 
Published: August 2006

Abstract

Seed limitation of plant species distribution has received much attention in recent years. The empirical evidence of seed limitation is, however, still weak, and mostly correlative. Unambiguous evidence can only be provided by long‐term transplantation experiments.
We used an 11‐year experiment, in which seeds of six perennial forest herbs were sown into 43 patches that were either occupied or unoccupied by the target species, to investigate the importance of seed limitation. In addition, we determined whether short‐term (1–4 years) and long‐term (11 years) experimental assessments provided similar results. Given that long‐term experiments are generally not possible, we examined whether environmental factors and vegetation composition can correctly identify suitable habitats.
Our results show that the distribution of the forest herbs investigated were limited by the availability of seeds, and that this pattern was qualitatively consistent, over time. However, the number of initially unoccupied patches with successful recruitment decreased with time.
The fact that a similar trend in recruitment success was found in sowing experiments in initially occupied patches suggests that the decrease in recruitment success over time cannot solely be attributed to habitat suitability. Environmental factors, such as soil nutrients and vegetation composition, were in some cases correlated with recruitment success, but the strength of these relationships was often weak.
Our results support the notion that seed availability is an important limitation of plant species abundance and distribution. The results also point to several difficulties related to the empirical assessment of seed limitation. We therefore suggest a protocol that should enhance the quality of future experiments.
Assembly rules operating along a primary riverbed–grassland successional sequence
Authors: HOLDAWAY ROBERT J. , SPARROW ASHLEY D. 
Published: August 2006

Summary

Assembly rules are broadly defined as any filter imposed on a regional species pool that acts to determine the local community structure and composition. Environmental filtering is thought to result in the formation of groups of species with similar traits that tend to co‐occur more often than expected by chance alone, known as Beta guilds. At a smaller scale, within a single Beta guild, species may be partitioned into Alpha guilds – groups of species that have similar resource use and hence should tend not to co‐occur at small scales due the principle of limiting similarity.
This research investigates the effects of successional age and the presence of an invasive exotic species on Alpha and Beta guild structuring within plant communities along two successional river terrace sequences in the Waimakariri braided river system in New Zealand.
Fifteen sites were sampled, six with and nine without the Russel lupin (Lupinus polyphyllus), an invasive exotic species. At each site, species presence/absence was recorded in 100 circular quadrats (5 cm in diameter) at 30‐cm intervals along a 30‐m transect. Guild proportionality (Alpha guild structuring) was tested for using two a priori guild classifications each containing three guilds, and cluster analysis was used to test for environmental structuring between sites.
Significant assembly rules based on Alpha guild structuring were found, particularly for the monocot and dicot guild. Guild proportionality increased with increasing ecological age, which indicated an increase in the relative importance of competitive structuring at later stages of succession. This provides empirical support for Weiher and Keddy's theoretical model of community assembly.
Lupins were associated with altered Alpha and Beta guild structuring at early mid successional sites. Lupin‐containing sites had higher silt content than sites without lupins, and this could have altered the strength and scale of competitive structuring within the communities present.
This research adds to the increasing evidence for the existence of assembly rules based on limiting similarity within plant communities, and demonstrates the need to incorporate gradients of environmental and competitive adversity when investigating the rules that govern community assembly.
Genetic enrichment of the arctic clonal plantSaxifraga cernuaat its southern periphery via the alpine sexualSaxifraga sibirica
Authors: KAPRALOV MAXIM V. , GABRIELSEN TOVE M. , SARAPULTSEV IVAN E. , BROCHMANN CHRISTIAN 
Published: August 2006

AbstractIsolation of populations at the margins of a species range may lead to decreasing genetic diversity via genetic drift and inbreeding. Hybridization between peripheral populations of two species can, however, counteract genetic impoverishment. The mainly clonal, polyploid plantSaxifraga cernuahas a wide arctic distribution but also extends southwards into alpine sites. In the Ural Mountains, its peripheral distribution overlaps with that of its sexually reproducing, diploid relativeSaxifraga sibirica, and fertile polyploids of more or less intermediate appearance are found in this overlap zone. We used amplified fragment length polymorphism (AFLP) analysis to address the potential impact of interspecific gene flow on genetic diversity in the peripheral populations. A total of 149 plants from 17 populations along a 1650 km south–north gradient were analysed for 253 markers. The results suggest that three Middle Ural populations containing fertile and morphologically more or less intermediate plants have been affected by hybridization. All of these plants formed a strongly supported (100%) group withS. cernuain a neighbour‐joining tree, but their AFLP phenotypes assigned either toS. cernuaor to artificial (simulated) F1hybrids betweenS. cernuaandS. sibiricain multilocus assignment tests. The three populations were highly diverse with virtually every plant representing a distinct AFLP phenotype, providing additional evidence for formation of later‐generation hybrids and/or backcrossing toS. cernua. In contrast, other peripheral populations ofS. cernuawere typically monoclonal, suggesting that hybridization withS. sibiricacan increase genetic diversity inS. cernuaat its southern periphery.
Comparative analysis of the within‐population genetic structure in wild cherry (Prunus avium L.) at the self‐incompatibility locus and nuclear microsatellites
Authors: SCHUELER SILVIO , TUSCH ALEXANDRA , SCHOLZ FLORIAN 
Published: August 2006

AbstractGametophytic self‐incompatibility (SI) systems in plants exhibit high polymorphism at the SI controlling S‐locus because individuals with rare alleles have a higher probability to successfully pollinate other plants than individuals with more frequent alleles. This process, referred to as frequency‐dependent selection, is expected to shape number, frequency distribution, and spatial distribution of self‐incompatibility alleles in natural populations. We investigated the genetic diversity and the spatial genetic structure within a Prunus avium population at two contrasting gene loci: nuclear microsatellites and the S‐locus. The S‐locus revealed a higher diversity (15 alleles) than the eight microsatellites (4–12 alleles). Although the frequency distribution of S‐alleles differed significantly from the expected equal distribution, the S‐locus showed a higher evenness than the microsatellites (Shannon's evenness index for the S‐locus: E = 0.91; for the microsatellites: E = 0.48–0.83). Also, highly significant deviations from neutrality were found for the S‐locus whereas only minor deviations were found for two of eight microsatellites. A comparison of the frequency distribution of S‐alleles in three age‐cohorts revealed no significant differences, suggesting that different levels of selection acting on the S‐locus or on S‐linked sites might also affect the distribution and dynamics of S‐alleles. Autocorrelation analysis revealed a weak but significant spatial genetic structure for the multilocus average of the microsatellites and for the S‐locus, but could not ascertain differences in the extent of spatial genetic structure between these locus types. An indirect estimate of gene dispersal, which was obtained to explain this spatial genetic pattern, indicated high levels of gene dispersal within our population (σg = 106 m). This high gene dispersal, which may be partly due to the self‐incompatibility system itself, aids the effective gene flow of the microsatellites, thereby decreasing the contrast between the neutral microsatellites and the S‐locus.
Assessment of the diversity and species specificity of the mutualistic association between Epicephala moths and Glochidion trees
Authors: KAWAKITA ATSUSHI , KATO MAKOTO 
Published: August 2006

AbstractThe obligate mutualisms between flowering plants and their seed‐parasitic pollinators constitute fascinating examples of interspecific mutualisms, which are often characterized by high levels of species diversity and reciprocal species specificity. The diversification in these mutualisms has been thought to occur through simultaneous speciation of the partners, mediated by tight reciprocal adaptation; however, recent studies cast doubt over this general view. In this study, we examine the diversity and species specificity of Epicephala moths (Gracillariidae) that pollinate Glochidion trees (Phyllanthaceae), using analysis of mitochondrial and nuclear gene sequences. Phylogenetic analysis of Epicephala moths associated with five Glochidion species in Japan and Taiwan reveal six genetically isolated species that are also distinguishable by male genital morphology: (i) two species specific to single host species (G. acuminatum and G. zeylanicum, respectively); (ii) two species that coexist on G. lanceolatum; and (iii) two species that share two, closely‐related parapatric hosts (G. obovatum and G. rubrum). Statistical analysis shows that the two species associated with G. lanceolatum are not sister species, indicating the colonization of novel Glochidion host in at least one lineage. Behavioural observations suggest that all six species possess the actively‐pollinating habit, thus none of the studied species has become a nonmutualistic ‘cheater’ that exploits the benefit resulting from pollination by other species. Our results parallel recent findings in ecologically similar associations, namely the fig–fig wasp and yucca–yucca moth mutualisms, and contribute to a more general understanding of the factors that determine ecological and evolutionary outcomes in these mutualisms.
Expression profiling and mutant analysis reveals complex regulatory networks involved in Arabidopsis response to Botrytis infection
Authors: AbuQamar Synan , Chen Xi , Dhawan Rahul , Bluhm Burton , Salmeron John , Lam Stephen , Dietrich Robert A. , Mengiste Tesfaye 
Published: August 2006

SummaryThe expression profiles of Botrytis‐inoculated Arabidopsis plants were studied to determine the nature of the defense transcriptome and to identify genes involved in host responses to the pathogen. Normally resistant Arabidopsis wild‐type plants were compared with coi1, ein2, and nahG plants that are defective in various defense responses and/or show increased susceptibility to Botrytis. In wild‐type plants, the expression of 621 genes representing approximately 0.48% of the Arabidopsis transcriptome was induced greater than or equal to twofold after infection. Of these 621 Botrytis‐induced genes (BIGs), 462 were induced at or before 36 h post‐inoculation, and may be involved in resistance to the pathogen. The expression of 181 BIGs was dependent on a functional COI1 gene required for jasmonate signaling, whereas the expression of 63 and 80 BIGs were dependent on ethylene (ET) signaling or salicylic acid accumulation, respectively, based on results from ein2 and nahG plants. BIGs encode diverse regulatory and structural proteins implicated in pathogen defense and abiotic and oxidative‐stress responses. Thirty BIGs encode putative DNA‐binding proteins that belong to ET response, zinc‐finger, MYB, WRKY, and HD‐ZIP family transcription‐factor proteins. Fourteen BIGs were studied in detail to determine their role in resistance to Botrytis. T‐DNA insertion alleles of ZFAR1 (At2G40140), the gene encoding a putative zinc‐finger protein with ankyrin‐repeat domains, showed increased local susceptibility to Botrytis and sensitivity to germination in the presence of abscisic acid (ABA), supporting the role of ABA in mediating responses to Botrytis infection. In addition, two independent T‐DNA insertion alleles in the WRKY70 gene showed increased susceptibility to Botrytis. The transcriptional activation of genes involved in plant hormone signaling and synthesis, removal of reactive oxygen species, and defense and abiotic‐stress responses, coupled with the susceptibility of the wrky70 and zfar1 mutants, highlights the complex genetic network underlying defense responses to Botrytis in Arabidopsis.
Pemphigus: Analysis of 1209 cases
Authors: Chams‐Davatchi Cheyda , Valikhani Mahin , Daneshpazhooh Maryam , Esmaili Nafiseh , Balighi Kamran , Hallaji Zahra , Barzegari Massoume , Akhiani Maryam , Ghodsi Zahra , Mortazavi Hosein , Naraghi Zahra 
Published: August 2006

AbstractBackground  Pemphigus is a rare and chronic life‐threatening disease. The clinical picture varies in reports from different regions of the world.Objective  To define the clinical forms of pemphigus in a large cohort of patients.Methods  Prospective analysis of 1209 patients diagnosed and followed at the Pemphigus Research Unit, Tehran University for Medical Sciences, from 1984 to 2003.Results   The mean age at onset was 42 years with a female to male ratio of 1.5/1. The most frequent form was pemphigus vulgaris. In pemphigus vulgaris, patients’ mucous membrane involvement alone was observed in 18%, skin involvement alone in 12%, and both in 70%. Pemphigus foliaceus was observed in 7% of the patients. Most complications were iatrogenic.Conclusion  In Iran, pemphigus vulgaris is the most frequent form of pemphigus. Females are more prone to the disease. The incidence of pemphigus in Tehran is approximately 1.6 per 100 000/year, and in Iran 1.0 per 100 000/year. The age of onset was lower than classically reported. Death occurred in 6.2% of the patients. In pemphigus vulgaris, the mucosal and skin form together had a worse prognosis than the other clinical forms.
Pigmented purpuric dermatosis and hepatitis profile: a report on 10 patients
Authors: Dessoukey M. Wagdy , Abdel‐Dayem Hussein , Omar Mohamed F. , Al‐Suweidi Naeema E. 
Published: August 2006

AbstractBackground  Pigmented purpuric dermatosis comprises a group of vascular disorders of unknown etiology. Histologically, it is characterized by lymphocytic capillaritis in the papillary dermis. Although leukocytoclastic vasculitis confined to the skin is frequently reported with hepatitis C, lymphocytic vasculitis is rarely reported.Methods  Ten patients with pigmented purpuric dermatosis were studied clinically and histopathologically. Hepatitis profile was carried out in all of the patients to evaluate the possible relation.Results  Of the 10 patients, five tested positive for hepatitis C and two for hepatitis B antibodies.Conclusion  Hepatitis C and B virus may play a role in the pathogenesis of pigmented purpuric dermatosis. Further case–control studies are necessary to confirm this conclusion.
Characterization of HLA‐B*5516, ‐B*1313, ‐B*9512, and ‐DRB1*1457 alleles identified in a southwest Chinese population†
Authors: Chen Q. , Zou H. , Xu X. H. , Luo M. , Wang J. , Zuo Y. Q. , Chen Y. H. , Chen X. H. , Chen X. L. , Yao Z. Q. , Song N. , Zeng J. , Mi X. Y. , Sun S. X. , Wang J. X. , Zhao T. M. 
Published: August 2006

AbstractThe human leukocyte antigen (HLA)‐B*5516 allele differs from the B*5502 by a single 97 T → C substitution (His to Tyr at position 33) in exon 2. The B*1313 allele results from 419 T → A and 420 A → C substitutions, encoding a Leu to Tyr substitution at 140 in exon 2 of the B*1301 allele. The B*9512 allele differs from B*1502 by a single 360 G → C substitution (Gln to His at 120) in exon 3. The DRB1*1457 allele appears to be a hybrid molecule generated by recombination between the DRB1*13 and DRB1*14 alleles. The serological equivalents of these new alleles are HLA‐B22, ‐B13, ‐B15, and DR13, respectively. Family studies detected two rare haplotypes: A*11, B*9512, DRB1*14 and A*24, B*52, Cw*07, DRB1*1457, DRB3*020201, DQB1*050301. The gene frequencies of these alleles in the Chinese population are less than 0.0001.
Association of Eubacterium nodatum and Treponema denticola with human periodontitis lesions
Authors: Haffajee A. D. , Teles R. P. , Socransky S. S. 
Published: August 2006

Background:  The purpose of the present investigation was to compare the levels, proportions and percentage of sites colonized by 40 bacterial species in subgingival plaque samples from periodontally healthy subjects and patients with chronic periodontitis to seek possible pathogens other than the consensus pathogens Porphyromonas gingivalis and Tannerella forsythia.Method:  Subgingival plaque samples were taken from the mesial aspect of each tooth in 635 subjects with chronic periodontitis and 189 periodontally healthy subjects. The samples were individually analyzed for their content of 40 bacterial species using checkerboard DNA–DNA hybridization (total samples = 21,832). Mean counts, % DNA probe counts and percentage of sites colonized at >105 were determined for each species in each subject and then averaged in each clinical group. Significance of difference between groups was determined using the Mann–Whitney test. Association between combinations of species and periodontal status was examined by stepwise logistic regression analysis. Analyses were repeated using a subset of subjects from both clinical groups who had proportions of P. gingivalis plus T. forsythia less than the median (4.42%) found in periodontally healthy subjects. All analyses were adjusted for multiple comparisons.Results:  For the 824 subjects the consensus pathogens P. gingivalis and T. forsythia as well as Eubacterium nodatum and Treponema denticola had significantly higher mean counts, proportions and percentage of sites colonized in samples from subjects with periodontitis than from periodontally healthy subjects. There were significantly more Capnocytophaga gingivalis, Streptococcus gordonii and Veillonella parvula in periodontally healthy subjects. E. nodatum, T. denticola, Streptococcus oralis, Streptococcus intermedius, Fusobacterium nucleatum ssp. vincentii all had higher counts and proportions in diseased than healthy subjects who had low proportions of P. gingivalis and T. forsythia. Logistic regression analysis indicated that the same species groups were associated with disease status after adjusting for the proportions of the other species.Conclusions:  This investigation confirmed the strong association of P. gingivalis and T. forsythia with chronic periodontitis and emphasized a strong association of E. nodatum and T. denticola with periodontitis whether in the presence or absence of high levels of the consensus pathogens. Other species, including S. oralis, Eikenella corrodens, S. intermedius and F. nucleatum ssp. vincentii, were associated with disease when P. gingivalis and T. forsythia were present in low proportions.
Resistance to acidic and alkaline environments in the endodontic pathogen Enterococcus faecalis
Authors: Nakajo K. , Komori R. , Ishikawa S. , Ueno T. , Suzuki Y. , Iwami Y. , Takahashi N. 
Published: August 2006

Background/aims:  This study aimed to investigate the biochemical mechanisms employed by the endodontic pathogen Enterococcus faecalis to confer acid‐ and alkali‐resistance and to compare these with the mechanisms of representative oral streptococci.Methods:  E. faecalis JCM8728, Streptococcus mutans NCTC10449 and Streptococcus sanguinis ATCC10556 were used to assess both acid‐ and alkali‐resistance by examining: (i) growth in complex media; (ii) stability of intracellular pH (pHin); (iii) cell durability to leakage of preloaded BCECF (2′,7′‐bis‐(2‐carboxyethyl)‐5,6‐carboxy‐fluorescein); and (iv) cell permeability to SYTOX‐Green.Results:  Growth was initiated by E. faecalis at pH 4.0–11.0, by S. mutans at pH 4.0–9.0 and by S. sanguinis at pH 5.0–9.0. The pHin was similar to the extracellular pH in S. mutans and S. sanguinis at pH 5–10, while the pHin of E. faecalis was maintained at approximately 7.5–8.5 when extracellular pH was 7.5–10 and was maintained at levels equivalent to the extracellular pH when pH < 7.5. Cell membranes of E. faecalis were resistant to BCECF leakage when extracellular pH was 2.5–12 and to SYTOX‐Green permeability at pH 4–10. The cell membrane durability to extracellular pH in E. faecalis was higher than that observed in the Streptococcus strains.Conclusion:  Compared to S. mutans, E. faecalis was found to be equally resistant to acid and more resistant to alkalis. The results suggest that pH‐resistance in E. faecalis is attributed to membrane durability against acid and alkali, in addition to cell membrane‐bound proton‐transport systems. These characteristics may account for why E. faecalis is frequently isolated from acidic caries lesions and from persistently infected root canals where calcium hydroxide medication is ineffective.
Oral adhesion and survival of probiotic and other lactobacilli and bifidobacteria in vitro
Authors: Haukioja A. , Yli‐Knuuttila H. , Loimaranta V. , Kari K. , Ouwehand A. C. , Meurman J. H. , Tenovuo J. 
Published: August 2006

Introduction:  Most probiotic products are consumed orally and hence it is feasible that the bacteria in these products may also attach to oral surfaces; however, the effects of these bacteria on the oral ecosystem are mostly unknown. Our aim was to evaluate the oral colonization potential of different probiotic, dairy, and fecal Lactobacillus and Bifidobacterium strains in vitro.Methods:  The binding of 17 Lactobacillus and seven Bifidobacterium strains to hydroxyapatite and microtitre wells coated with human saliva was tested. Binding of selected strains to human buccal epithelial cells and co‐adherence with Fusobacterium nucleatum were also investigated. In addition, the survival in sterilized human whole saliva was examined.Results:  There was a large variation in binding to saliva‐coated surfaces and buccal epithelial cells but all strains survived in saliva. The binding pattern of the probiotics did not differ from the binding of the fecal strains. F. nucleatum altered the binding of both the low‐binding bifidobacteria and the high‐binding lactobacilli.Conclusion:  The differences in binding in vitro may indicate that there are also differences in the persistence of the different probiotic strains in the oral cavity in vivo.