bluuebunny/crossref_metadata_2025 huggingface dataset:
Climatic variability alters the outcome of long‐term community assembly
Authors: MacDougall Andrew S. , Wilson Scott D. , Bakker Jonathan D.
Published: February 2008

We used seed additions to test experimentally whether long‐term community assembly unfolds consistently (deterministic model) or whether different outcomes are possible depending on variations in climate and the presence of exotic dominants (stochastic model). The experiment was conducted in homogeneous semi‐arid grassland on the northern Great Plains of North America. Native grass seed additions in each of 3 years (1994–96) were combined factorially with repeated selective herbicide applications to reduce the cover of the extant dominant, a Eurasian C3grass (Agropyron cristatum). We assessed whether composition converged or diverged among treatments between 1996 and 2004.

The outcome of long‐term community assembly varied by establishment year, in association with significant variations in monthly growing‐season precipitation from 68‐year averages during the years when seed was added. In 2004, the added native C4grassBouteloua gracilisdominated plots sprayed and seeded in 1994 and 1995, resisting re‐invasion and having significantly higher plot diversity. In contrast, plots sown in 1996 – one of the driest years on record – reverted to the exotic C3grass. Seeded but unsprayed plots maintained their pre‐treatment dominance by exotic grass. Rainfall variability was also associated with the extent of exotic grass cover and bare soil in unsprayed plots, and natural recruitment by native species from nearby prairie.

Establishment success varied significantly among the added species. All seeded grasses, other thanB. gracilis, were mostly absent by 2004. The failure of these native C3species to establish appears consistent with deterministic assembly models where local abiotic conditions filter out unsuitable species.

Synthesis. Our results indicate that stochastic and deterministic processes operate simultaneously to influence community assembly, depending on interactions among climate, seed availability, species identity and disturbance during the initial stages of establishment. Multiple assembly trajectories developed, but the assembled communities did not include all the added species. Conversion of degraded grassland back to native‐dominated grassland was possible, but only with the removal of the exotic dominant and seed additions during years that were suitably wet for establishment. Once formed, however, the assembled native community resisted re‐invasion. This suggests that native grassland restoration will depend on establishment measures as intense as those used during initial cultivation almost a century earlier.
Spatio‐temporal variation in fruit production and seed predation in a perennial herb influenced by habitat quality and population size
Authors: Ågren Jon , Ehrlén Johan , Solbreck Christer
Published: February 2008

In patchily distributed plant species, seed production is likely to be influenced both by local abiotic factors affecting plant size and conditions for fruit maturation, and by population characteristics affecting the intensity of interactions with mutualists and antagonists. However, the relative importance of these effects is poorly known.

We used multiple regression and path models to examine the importance of abiotic factors (sun exposure, soil depth) and population characteristics (size, density and connectivity) for variation in flower and fruit production and intensity of seed predation among 39 populations of the long‐lived herb Vincetoxicum hirundinaria in three consecutive years. In addition, we manipulated water availability in a field experiment and recorded short‐term and long‐term effects on fruit output, and conducted a supplemental hand‐pollination experiment.

Flower production varied little, while fruit initiation, fruit abortion and fruit predation varied considerably among years. Sun exposure and soil depth affected fruit production per plant indirectly and positively through their effects on flower number. Population density affected fruit production negatively through its effect on flower number. Both fruit initiation and the proportion of fruits attacked by the tephritid fly Euphranta connexa were related positively to population size.

The number of full‐size fruits per plant was related positively to sun exposure and population size in two years each, and related negatively to population density in one year. However, because of seed predation, the number of intact mature fruits was related significantly to population characteristics in only one of three years.

The field experiments showed that both shortage of water and insufficient pollination may limit fruit set in V. hirundinaria.

Synthesis. These results demonstrate that the relative importance of local abiotic conditions and population characteristics may vary considerably along the chain of events from flower formation to intact fruit, and also among years. They further show that, at least in species with a naturally patchy distribution, connectivity may be relatively unimportant for variation in reproductive output compared to effects of habitat quality, population size and density.
Effects of plant abundance on reproductive success in the biennial Sabatia angularis (Gentianaceae): spatial scale matters
Authors: Spigler Rachel B. , Chang Shu‐Mei
Published: February 2008

Small and low‐density populations often suffer significant reductions in reproduction, as exemplified by studies on rare and threatened species. While this phenomenon is less studied in common species, if general, it should not be restricted to those in peril. We addressed this assertion by examining the effects of plant abundance, measured at population‐level (population size, density) and local‐level (local neighbourhood size, LNS) spatial scales, on fruit set, seed set and subsequent reproductive success (RS) across 19 natural populations of the widespread biennial Sabatia angularis (Gentianaceae). We also examined stigmatic pollen loads across a subset of populations to address whether changes in reproduction were related to reduced pollination.

Effects of plant abundance on reproduction were evident at both spatial scales. At the population level, population size – but not density – affected fruit set significantly. This effect was non‐linear. Fruit set in populations larger than 15 individuals was relatively constant, but dropped abruptly in populations below that size. This relationship did not prevail between population size and RS. Instead, RS declined significantly with population density.

At the local level, increases in LNS between 1‐m and 4‐m radii from study plants increased fruit set significantly. In contrast, increases within 1 m significantly reduced seed set. Both of these effects prevailed at different spatial scales for RS; increases in 1‐m LNS reduced RS, but increases beyond that distance and within 4 m increased RS.

Although non‐significant, trends in the data are consistent with facilitative interactions for pollination influencing local‐level effects on fruit set. However, negative interactions, presumably because of competition for resources, are more important for determining seed set at local scales. Both interactions influence RS, but the effect of competition appears to dominate at the population level.

Synthesis. This study demonstrates that although significant reductions in fruit set in small S. angularis populations imply that common species are not impervious to reproductive disadvantages, small populations need not experience reduced RS. Furthermore, low‐density populations actually enjoy increased RS. As such, this study highlights the complexity of ecological interactions affecting reproduction and the importance of incorporating multiple spatial scales when examining population dynamics.
Differences in the degree of environmental control on large and small tropical plants: just a sampling effect?
Authors: Jones Mirkka M. , Tuomisto Hanna , Olivas Paulo C.
Published: February 2008

Tropical rain forest tree species are commonly perceived to have more generalized habitat distributions than understorey species. However, the correspondence between floristic patterns in large trees and smaller understorey plants in relation to environmental differences has rarely been investigated. Comparative analyses are complicated by the fact that tree data are often much more noisy, with higher overall species richness and poorer spatial and temporal representation of species composition within sampling plots.

Using data on trees and pteridophytes collected in 1125 plots located within 6 km2 of lowland rain forest in Costa Rica, we asked: (i) Is there evidence that trees are more generalized in their edaphic and topographic distributions than pteridophytes, and (ii) How much might differences in sampling efficiency affect the results?

We ran community‐level analyses using Mantel tests, and for the five most frequent tree and pteridophyte species we ran logistic regression analyses of species occurrence. To investigate the influence of differing sampling efficiency, the analyses were repeated with four rarefied pteridophyte data sets approximating key structural features of the tree data set.

Differences in community composition in trees and in all pteridophyte data sets were most strongly correlated with environmental differences in the same five soil variables. The most frequent species in both plant groups had non‐random edaphic and topographic distributions.

Both Mantel correlations and the predictive performance of single species models (AUC values) were higher for the full pteridophyte data set than for trees, but these differences were much reduced after pteridophyte rarefaction.

The performance of the species occurrence models calibrated with rarefied pteridophyte data appeared poor when tested on rarefied data. However, their performance in predicting occurrences in the full data set was usually moderate (AUC > 0.70). This suggests that the tree species models may also predict species’ potential habitat distributions better than is apparent from their AUC values.

Synthesis. Our results indicate that rain forest trees and pteridophytes may respond to mesoscale environmental variation in qualitatively similar ways, but that trees will appear much more generalized in their response to the environment unless differences in sampling efficiency are taken into account.
Growth and wood density predict tree mortality in Amazon forests
Authors: Chao Kuo‐Jung , Phillips Oliver L. , Gloor Emanuel , Monteagudo Abel , Torres‐Lezama Armando , Martínez Rodolfo Vásquez
Published: February 2008

Tree mortality is an important process in forest ecology. We explored the extent to which tropical tree death is a predictable outcome of taxon and individual level properties by means of mixed‐species logistic regression, for trees ≥ 10 cm in diameter. We worked in two lowland forest regions with markedly different floristic composition and dynamic regimes – the high wood density, low‐mortality northeastern (NE) Amazon (in eastern Venezuela), and the low wood density, high‐mortality northwestern (NW) Amazon (in northern Peru).

Among those genera that are shared between regions there were no detectable regional differences in mortality rates. This suggests that floristic compositional differences are a major driver of the twofold regional contrast in stand‐level mortality.

In NE forests, mortality risk of individual trees is best predicted by low taxon‐level wood density, slow relative growth, and large size, reflecting phylogenetically determined life‐history strategy, physiological stress and senescence.

In NW forests, trees with low wood density and slow relative growth are also at most risk, but probability of death is independent of tree size, indicating that senescence is unimportant in this region.

Synthesis.This study shows that despite fundamental floristic and dynamic differences between the two Amazonian regions, mortality risk can be predicted with mixed‐species, individual‐based statistical models and that the predictors are remarkably similar, such that tree growth and wood density both play important roles.
The spatiotemporal dynamics of a primary succession
Authors: Cutler N. A. , Belyea L. R. , Dugmore A. J.
Published: February 2008

Conceptual models of ecosystem development commonly predict a phase of initial colonization characterized by the nucleation, growth and coalescence of discrete patches of pioneer plants. Spatiotemporal dynamics during subsequent development may follow one of three different models: the classical model, in which initially discrete patches of competitive dominant (secondary) colonists coalesce to form a homogeneous cover; the patch dynamics model, in which renewal mechanisms such as disturbance create a shifting mosaic of patches at different stages; and the geoecological model, in which the vegetation gradually differentiates along edaphic gradients related to the underlying physical template.

These models of spatiotemporal dynamics were tested using vegetation and soil data from an 850‐year chronosequence, comprised of seven lava flows on Mt Hekla, Iceland. The scale and intensity of spatial pattern were quantified on each flow using spatial analyses (mean‐variance ratios, quadrat variance techniques and indices of autocorrelation). Changes in spatial pattern with increasing terrain age were compared with predicted trajectories, in order to identify which of the models of spatiotemporal dynamics was most consistent with the observations.

The early stages of ecosystem development were characterized by colonization of the pioneer species, especially Racomitrium mosses, in discrete patches (‘Pioneer colonization stage’, < 20 years), which then grew laterally and coalesced to form a continuous, homogeneous carpet (‘Pioneer expansion stage’, 20–100 years). Later in the sequence, higher plants established in discrete patches within this pioneer matrix (‘Higher plant colonization stage’, 100–600 years). Over time, heterogeneity re‐emerged at a larger spatial scale as the vegetation differentiated according to topographic variations in the underlying substrate (‘Differentiation stage’, > 600 years).

Synthesis. The spatiotemporal dynamics observed in the early stages of this succession were consistent with a model of pioneer nucleation in micro‐scale safe sites, followed by growth, coalescence and eventual fragmentation of pioneer patches. The spatial patterns which emerged later in development support the geoecological model, with spatial differentiation of vegetation related to meso‐scale substrate topography. The findings provide insight on how vegetation patterns emerge at different stages of ecosystem development in response to differing scales of heterogeneity in the underlying physical environment.
Regulation of Vibrio alginolyticus virulence by the LuxS quorum‐sensing system
Authors: Ye J , Ma Y , Liu Q , Zhao D L , Wang Q Y , Zhang Y X
Published: February 2008

Quorum sensing (QS) is a bacterial intercommunication system that controls the expression of multiple genes in response to population density. The LuxS QS system regulates the expression of several virulence factors in a wide variety of pathogenic bacteria. LuxS has been characterized to be responsible for producing a type of autoinducer, AI‐2, which stimulates the expression of the luciferase operon in Vibrio harveyi. Vibrio alginolyticus is established as an opportunistic pathogen of several marine animals, and its LuxS QS system remains undefined. To investigate the pathogenic role of luxS in V. alginolyticus, the luxS mutants of both the standard strain ATCC 33787 and a fish‐clinical isolate MVP01, named MYJS and MYJM, respectively, were constructed. The mutation resulted in reduced lethality to Pagrus major. Intraperitoneal LD50 of MYJS and MYJM increased by 15‐ and 93‐fold, respectively. The two luxS mutants exhibited a lower growth rate and defective flagellar biosynthesis. They also showed a significant decrease in protease production and an increase in both extracellular polysaccharide production and biofilm development. The results suggest that the LuxS QS system plays an important role in regulating the expression of virulence factors in V. alginolyticus.
Effect of temperature on pharmacokinetics of enrofloxacin in mud crab, Scylla serrata (Forsskål), following oral administration
Authors: Fang W H , Hu L L , Yang X L , Hu K , Liang S C , Zhou S
Published: February 2008

The study was conducted to evaluate the pharmacokinetics of enrofloxacin following a single oral gavage (10 mg kg−1) in mud crab, Scylla serrata, at water temperatures of 19 and 26 °C. Enrofloxacin concentration in haemolymph was determined using high‐performance liquid chromatography (HPLC). A multiple and repeated haemolymph sampling from the articular cavity of crab periopods was developed. The haemolymph of an individual crab was successfully sampled up to 11 times from the articular cavity. The profile of haemolymph enrofloxacin concentration of an individual crab versus time was thus achieved. The mean haemolymph enrofloxacin concentration versus time was described by a two‐compartment model with first‐order absorption at two water temperatures. The peak concentrations of haemolymph enrofloxacin at 19 and 26 °C were 7.26 and 11.03 μg mL−1, at 6 and 2 h, respectively. The absorption and distribution half‐life time ( and t1/2α) at 19 °C were 3.7 and 4.5 h, respectively, which were markedly larger than the corresponding values (1.1 and 1.5 h) at 26 °C; the elimination half‐life time (t1/2β) was 79.1 and 56.5 h at 19 and 26 °C, respectively. The area under curve (AUC), total body clearance (Cl) and mean residence time (MRT0–∞) at 19 °C were 636.0 mg L−1 h, 0.016 L h−1 kg−1 and 102.5 h, respectively; the corresponding values at 26 °C were 583.4 mg L−1 h, 0.018 L h−1 kg−1and 63.7 h. These results indicate that enrofloxacin is absorbed and eliminated more rapidly in mud crab at 26 °C than at 19 °C.
Nucleotide sequence variations of the major structural proteins (VP15, VP19, VP26 and VP28) of white spot syndrome virus (WSSV), a pathogen of cultured Litopenaeus vannamei in Mexico
Authors: Molina‐Garza Z J , Galaviz‐Silva L , Rosales‐Encinas J L , Alcocer‐González J M
Published: February 2008

White spot syndrome virus (WSSV) was first reported in farmed Litopenaeus vannamei stocks in Sinaloa and Sonora, Mexico during 1999 and continues to cause severe shrimp losses. WSSV genes encoding nucleocapsid (VP26 and VP15) and envelope proteins (VP19 and VP28) of a Mexican isolate were cloned in the pMosBlue vector. The nucleotide sequences of these genes were compared with WSSV isolates in GenBank. VP15 is highly conserved, and VP26 showed 99% homology to a Chinese isolate. The VP28 fragment demonstrated 100% homology to the majority of the isolates analysed (UniProt accession no. Q91CB7), differing from two Indian WSSV and one Chinese WSSV isolates by two non‐conserved and one conserved replacements, respectively. Because of their highly conserved nature, these three structural proteins are good candidates for the development of antibody‐based WSSV diagnostic tools or for the production of recombinant protein vaccines to stimulate the quasi‐immune response of shrimp. In contrast, VP19 of the Mexican isolate was distinguishable from almost all isolates tested, including an American strain of WSSV (US98/South Carolina, GenBank accession no. AAP14086). Although homology was found with isolates from Taiwan (GenBank accession no. AAL89341) and India (GenBank accession no. AAW67477), VP19 may have application as a genetic marker.
First cases of amoebic gill disease (AGD) in Norwegian seawater farmed Atlantic salmon, Salmo salar L., and phylogeny of the causative amoeba using 18S cDNA sequences
Authors: Steinum T , Kvellestad A , Rønneberg L B , Nilsen H , Asheim A , Fjell K , Nygård S M R , Olsen A B , Dale O B
Published: February 2008

Amoebic gill disease (AGD) was observed in seawater farmed Atlantic salmon at four geographically distant locations on the western coast of Norway. To the best of our knowledge, these are the first detected AGD outbreaks in Norway. The outbreaks lasted for 7–12 weeks in late autumn 2006 and were for the most part concurrent. The crude, cumulative mortality was in the range of 12–20% at three farms and 82% at a fourth. The histopathology showed uniform parasomal amoebae in lesions characteristic for AGD. Another gill disease, proliferative gill inflammation (PGI), was also present to a variable degree and the distinction between the two gill problems is discussed. Seawater temperatures were 3.5 °C higher than average before disease outbreaks, which subsided in early winter. The geographical and time pattern of these outbreaks strongly indicates simultaneous infection from the marine environment. Two contiguous 18S cDNA sequences, obtained by reverse transcriptase PCR from gill tissue with AGD‐related lesions, showed highest similarity (99.2%) to a newly recognized species designated Neoparamoeba perurans and maximum likelihood analysis demonstrates that they represent Norwegian strains of this Neoparamoeba lineage.
Endogenous ouabain and cardiomyopathy in dialysis patients
Authors: Stella P. , Manunta P. , Mallamaci F. , Melandri M. , Spotti D. , Tripepi G. , Hamlyn J. M. , Malatino L. S. , Bianchi G. , Zoccali C.
Published: February 2008

Background and methods.  Endogenous ouabain (EO) is markedly raised in patients with chronic renal failure. As high EO induces myocardial cell hypertrophy in vitro and it is associated with left ventricular hypertrophy (LVH) in essential hypertensives and in patients with heart failure we investigated the relationship between plasma EO and LV mass and geometry in 156 end‐stage renal disease (ESRD) patients. EO was measured by a specific radioimmunoassay and by mass spectrometry.

Results.  On univariate analysis, plasma EO was directly related to LV mass (r = 0.26, P = 0.001) and LV end diastolic volume (r = 0.25, P = 0.002) and these relationships held true in multiple linear regression models including a series of potential confounders. Patients with eccentric LVH (n = 41, i.e. 26%) had the highest plasma levels of EO when compared to patients with other patterns of LV geometry (P = 0.001). Furthermore, plasma EO had diagnostic value for eccentric LVH because the area under the corresponding ROC curve (68%) was significantly greater (P = 0.002) than the threshold of diagnostic indifference. In this analysis, the sensitivity was 91% and the specificity was 36%. The positive predictive value was 33% but EO had a remarkably high negative predictive value (92%) for the exclusion of eccentric hypertrophy.

Conclusions.  In ESRD patients, plasma EO is independently associated with LV mass, LV volume and eccentric LVH. The results of this study are compatible with the hypothesis that EO is involved in alterations of LV mass in ESRD.
Association of F11 receptor gene polymorphisms with central obesity and blood pressure
Authors: Ong K. L. , Leung R. Y. H. , Wong L. Y. F. , Cherny S. S. , Sham P. C. , Lam T. H. , Lam K. S. L. , Cheung B. M. Y.
Published: February 2008

Objectives.  F11 receptor, also known as junctional adhesion molecule‐1, in the autonomic nervous system is implicated in the development of hypertension in spontaneous hypertensive rats. We investigated the association of single nucleotide polymorphisms (SNPs) in the F11 receptor gene (F11R) with hypertension and central obesity in Hong Kong Chinese.

Methods.  Seven tagging SNPs were identified in the HapMap database. Genotyping was performed using Sequenom MassArray in 263 hypertensive subjects and 393 normotensive controls, of whom 263 matched the cases in age and sex.

Results.  When subjects on anti‐hypertensive medication were excluded, rs790056 and rs2774276 were associated with lower systolic blood pressure (TT:124.8 ± 18.3 mmHg vs. TC + CC: 120.2 ± 15.5 mmHg, P = 0.004 and CC: 124.7 ± 18.5 mmHg vs. CG+GG: 120.5 ± 15.1 mmHg, P = 0.007 respectively). Comparing 213 subjects with central obesity with 213 controls matched for sex and age, rs2481084 and rs3737787 were associated with lower odds of central obesity (odds ratio = 0.516, P = 0.002 and odds ratio = 0.540, P = 0.005 respectively). All these associations remained significant after correction for multiple testing. Analysis of statistically similar SNPs suggested that the causative variants for systolic blood pressure were located in F11R, whilst those for central obesity could be due to causative variants in the transcription factor 1 gene immediately upstream.

Conclusions.  F11 receptor plays a role in blood pressure regulation, not only in rats but also in man. The link between F11 receptor and central obesity merits further investigation.
Soluble CD40L, platelet surface CD40L and total platelet CD40L in congestive heart failure: relationship to platelet volume, mass and granularity
Authors: Chung I. , Choudhury A. , Patel J. , Lip G. Y. H.
Published: February 2008

Background.  Many complications associated with congestive heart failure (CHF) have a thrombosis‐related aetiology, which may involve platelets. The immune modulator pair CD40‐CD40L has been proposed to be an important link between inflammation and thrombosis and may be important in the pathophysiology of CHF.

Objective.  To study soluble CD40L (sCD40L), platelet surface CD40L (%GCD40L) and total platelet CD40L (pCD40L) levels in CHF patients, their relationships to other platelet indices (platelet volume, mass and component) and to assess their prognostic value.

Methods.  We measured sCD40L (by ELISA); pCD40L (by a platelet lysate assay); platelet surface CD40L (%GCD40L) expression by flow cytometry; mean platelet volume (MPV), mean platelet mass (MPM) and mean platelet component (MPC); in 108 patients with stable CHF. Levels were compared with 37 ‘healthy controls’ and 63 ‘disease controls’. After a median follow‐up period of 490 days, clinical endpoints were determined.

Results.  pCD40L was significantly higher in CHF than disease controls, but not sCD40L or %GCD40L levels. CHF patients and disease controls had higher MPV (one‐way anova, P < 0.0001), whilst MPC was significantly lower in CHF patients (P < 0.0001), compared to healthy controls. All indices related to CD40L (i.e. sCD40L, pCD40L and %GCD40L) were neither related to disease severity or left ventricular ejection function, nor to clinical endpoints at follow‐ups.

Conclusion.  Patients with stable CHF patients did not exhibit enhanced levels of CD40L and the latter did not predict clinical events at follow‐up. The lack of difference in CD40L levels between CHF and disease controls suggests that CD40L may not have a major role in CHF per se, but in the comorbidities associated with CHF.
Cholesterol efflux pathways and other potential mechanisms involved in the athero‐protective effect of high density lipoproteins
Authors: Tall A. R.
Published: February 2008

Plasma high density lipoprotein (HDL) levels bear a strong independent inverse relationship with atherosclerotic cardiovascular disease. Although HDL has anti‐oxidant, anti‐inflammatory, vasodilating and anti‐thrombotic properties, the central anti‐atherogenic activity of HDL is likely to be its ability to remove cholesterol and oxysterols from macrophage foam cells, smooth muscle cells and endothelial cells in the arterial wall. To some extent, the pleotropic athero‐protective properties of HDL may be related to its ability to promote sterol and oxysterol efflux from arterial wall cells, as well as to detoxify oxidized phospholipids. In cholesterol‐loaded macrophages, activation of liver X receptors (LXRs) leads to increased expression of adenosine triphosphate (ATP) binding cassetter transporter (ABCA1), ATP binding cassetter transporter gene (ABCG1) and apoE and promotes cholesterol efflux. ABCA1 stimulates cholesterol efflux to lipid‐poor apolipoproteins, whilst ABCG1 promotes efflux of cholesterol and oxysterols to HDL. Despite some recent setbacks in the clinical arena, there is still intense interest in therapeutically targeting HDL and macrophage cholesterol efflux pathways, via treatments with niacin, cholesterol ester transfer protein inhibitors, LXR activators and infusions of apoA‐1, phospholipids and peptides.
Stroke event rates in anticoagulated patients with paroxysmal atrial fibrillation
Authors: Lip G. Y. H. , Frison L. , Grind M. ,   the SPORTIF Investigators
Published: February 2008

Aims.  To test the hypothesis that stroke and systemic embolic events (SEE) in the stroke prevention using an oral thrombin inhibitor in atrial fibrillation (SPORTIF) III and V trials are different between paroxysmal and persistent atrial fibrillation (AF).

Methods.  Data analysis from two cohorts of patients enroled in the prospective SPORTIF III and V clinical trials (n = 7329); 836 subjects (11.4%) with paroxysmal AF [mean age 70.1 years (SD = 9.5)] were compared with 6493 subjects with persistent AF for this ancillary study.

Results.  The annual event rates for stroke/SEE are 1.73% for persistent AF and 0.93% for paroxysmal AF. In a multivariate analysis, after adjusting for stroke risk factors, gender and aspirin usage, the differences remained statistically significant with a higher hazard ratio (HR) for stroke/SEE in persistent AF [vs. paroxysmal AF, HR 1.87, 95% confidence interval (CI) 1.04–3.36; P = 0.037]. In ‘high risk’ patients (with ≥2 stroke risk factors) annual event rates for stroke/SEE were 2.08% for persistent AF and 1.27% for paroxysmal AF (adjusted HR = 1.68, 95% CI 0.91–3.1, P = 0.098). Elderly patients had annual event rates for stroke/SEE of 2.38% for persistent AF and 1.13% for paroxysmal AF (adjusted HR = 2.27, 95% CI 0.92–5.59, P = 0.075). Vitamin K antagonist (VKA)‐naïve paroxysmal AF patients had a 1.89%/year stroke/SEE rate, compared with 0.61% for previous VKA takers (HR = 0.33, 95% CI 0.11–1.01, P = 0.052).

Conclusion.  In this large clinical trial cohort of anticoagulated AF patients, those with paroxysmal AF had stroke rates which were lower than for patients with persistent AF, although both groups had broadly similar stroke risk factors. Subjects with paroxysmal AF at ‘high risk’ had stroke/SEE rates that were not significantly different to persistent AF subjects.
The first postmodern pandemic: 25 years of HIV/ AIDS
Authors: Kallings L. O.
Published: February 2008

Science responded to the challenge of AIDS by rapidly identifying aetiology, describing pathogenesis and transmission routes, and developing diagnostic tests and treatment. However, this did not prevent the global spread of HIV, with 25 million fatal cases so far, another 33 million infected, and disastrous socioeconomic and demographic consequences. In spite of unprecedented political attention and financial resources, the response is falling further behind the growth of the epidemic. This is partly due to the unique characteristics of the virus, such as persistent infection, vertical transmission and a variability that allows it to escape immunity and antiretroviral drugs, and partly due to human characteristics such as a strong procreative instinct, drug use and ostracism. Denial, myths and complacency are major obstacles to rational measures. With no cure or vaccine in sight, scaling up prevention is of paramount importance. To meet the goal of universal access to prevention, treatment and care by 2010 would require a quadrupling of funding to an estimated US$42 billion by 2010, including adequate overall strengthening of healthcare systems, but in any case, the world will have to learn to live with HIV for the foreseeable future.
Pyrethroid tolerance is associated with elevated expression of antioxidants and agricultural practice in Anopheles arabiensis sampled from an area of cotton fields in Northern Cameroon
Authors: MÜLLER PIE , CHOUAÏBOU MOUHAMADOU , PIGNATELLI PATRICIA , ETANG JOSIANE , WALKER EDWARD D. , DONNELLY MARTIN J. , SIMARD FRÉDÉRIC , RANSON HILARY
Published: February 2008

Spraying of agricultural crops with insecticides can select for resistance in nontarget insects and this may compromise the use of insecticides for the control of vector‐borne diseases. The tolerance of the malaria vector, Anopheles arabiensis to deltamethrin was determined in a field population from a cotton‐growing region of Northern Cameroon both prior to and midway through the 4‐month period of insecticide application to the cotton crop. A 1.6‐fold increase in the median knockdown time was observed. To determine whether this increased tolerance was associated with constitutively elevated levels of genes commonly associated with insecticide resistance, RNA was extracted from F1 progeny from family lines of field‐caught mosquitoes and hybridized to the Anopheles gambiae detox chip. The experimental design avoided the confounding effects of colonization, and this study is the first to measure gene expression in the progeny of gravid, wild‐caught mosquitoes. Several genes with antioxidant roles, including superoxide dismutases, a glutathione S‐transferase and a thioredoxin‐dependent peroxidase, and a cytochrome P450 showed elevated expression in mosquito families collected during the insecticide‐spraying programme. These genes may constitute an important general defence mechanism against insecticides. Intriguingly, the levels of expression of these genes were strongly correlated suggesting a common regulatory mechanism.
Evolution of ecological specialization and venom of a predatory marine gastropod
Authors: REMIGIO E. A. , DUDA JR T. F.
Published: February 2008

Understanding the evolution of ecological specialization is important for making inferences about the origins of biodiversity. Members of the predatory, marine gastropod genusConusexhibit a variety of diets and the ability to capture prey is linked to a venom comprised of peptide neurotoxins, termed conotoxins. We identified conotoxin transcripts fromConus leopardus, a species ofConusthat uniquely preys exclusively on hemichordates, and compared its venom duct transcriptome to that of four otherConusspecies to determine whether a shift to a specialized diet is associated with changes in the venom composition of this species. We also examined the secondary structure of predicted amino acid sequences of conotoxin transcripts ofC. leopardusto identify substitutions that may be linked to specialization on hemichordates. We identified seven distinct conotoxin sequences fromC. leopardusthat appear to represent transcripts of seven distinct loci. Expression levels and the diversity of conotoxins expressed byC. leopardusare considerably less than those of otherConus.Moreover, gene products of two transcripts exhibited unique secondary structures that have not been previously observed from otherConus. These results suggest that transition to a specialist diet is associated with reduction in the number of components expressed in venoms ofConusand that diverse venoms ofConusare maintained in species with a broad dietary width.
Chloroplast phylogeography ofDipentodon(Dipentodontaceae) in southwest China and northern Vietnam
Authors: YUAN QING‐JUN , ZHANG ZHI‐YONG , PENG HUA , GE SONG
Published: February 2008

The evolutionary history of plants in the southeast Tibetan Plateau might be the most complicated around the world because of the area's extremely complex topography and climate induced by strong tectonic activity in recent history. In this research, we implemented a phylogeographical study using chloroplast sequences (psbA‐trnH andtrnQ‐rps16 intergenic spacer) onDipentodon, a monotypic or ditypic genus (D. sinicusandD. longipedicellatus) distributed in southwest China and adjacent areas including Myanmar (Burma), northeast India and northern Vietnam. A total of 257 samples from 16 populations from the southeast Tibetan Plateau (D. longipedicellatus) and the Yungui Plateau (D. sinicus) were collected. The results revealed thatDipentodonhad 11 haplotypes for the two intergenic spacers, high genetic diversity (hT = 0.902) and high genetic differentiation (NST = 0.987 andGST = 0.948).amovaanalysis showed that the component of among‐population within region/species (55.25%) was unexpectedly larger than the among‐species/region component (43.69%), which indicates that there is no justification for recognizing two species inDipentodon. Correlation of pairwise genetic and geographical distances showed thatDipentodonpopulations in the southeast Tibetan Plateau may have suffered more habitat fragmentation than populations in the Yungui Plateau because of the uplift of the Tibetan Plateau than populations in the Yungui Plateau have. Nested clade analysis showed that 11 haplotypes formed two 3‐level, three 2‐level and seven 1‐level clades, with eight clades showing significant geographical association. However, clade 2‐1 and 2‐2 did not cluster together, although they are distributed in the same region (Yungui Plateau) and belong to the same species (D. sinicus). This led not only to incongruence between haplotype network and geographical distribution of 2‐level clades, but also to paraphyly ofD. sinicustoD. longipedicellatus. We concluded that the incongruence and paraphyly may result from incomplete lineage sorting during the rapid and extreme tectonic events of the Tibetan Plateau. The results reported here will no doubt provide new insights into the evolution of biodiversity on the Tibetan Plateau and adjacent areas, and a historical framework for the conservation of biodiversity in this area, includingDipentodon.
Host–parasite interactions in oligotrophic stream ecosystems: the roles of life‐history strategy and ecological niche
Authors: GEIST JUERGEN , KUEHN RALPH
Published: February 2008

Biodiversity in fluvial ecosystems is under pressure as a consequence of their degradation. Conservation strategies for endangered freshwater molluscs and for salmonid fishes have been proposed but they are typically poorly integrated. Here, we examined for the first time the genetic structure of a critically endangered obligate mollusc invertebrate parasite, the freshwater pearl mussel (Margaritifera margaritifera), and its vertebrate host fish, the brown trout (Salmo trutta m. fario), in European headwater streams. We compared genetic differentiation and diversity with productivity and ecological habitat features of both species in nine different European streams from the drainage systems of the Danube, Elbe, Weser, Tuuloma, Kemijoki and Aulne. Genetic differentiation was more pronounced in pearl mussel than in brown trout, although the drainage‐specific patterns were generally similar. Genetic diversity of host and parasite was negatively correlated. The most oligotrophic, postglacially colonized areas represented genetic diversity hotspots with high conservation priority for pearl mussels, whereas their host fish displayed low diversity in these areas. This pattern can be explained by differences in the ecological niches and in the life‐history strategies of both species. These results question the effectiveness of single‐species approaches in the conservation of genetic aquatic resources and suggest that genetic information from species with different life‐history strategies, such as invertebrates and fish, should be considered simultaneously for geographical conservation prioritization in stream ecosystems.
Defining reproductively isolated units in a cryptic and syntopic species complex using mitochondrial and nuclear markers: the brooding brittle star, Amphipholis squamata (Ophiuroidea)
Authors: BOISSIN E. , FÉRAL J. P. , CHENUIL A.
Published: February 2008

At a time when biodiversity is threatened, we are still discovering new species, and particularly in the marine realm. Delimiting species boundaries is the first step to get a precise idea of diversity. For sympatric species which are morphologically undistinguishable, using a combination of independent molecular markers is a necessary step to define separate species. Amphipholis squamata, a cosmopolitan brittle star, includes several very divergent mitochondrial lineages. These lineages appear totally intermixed in the field and studies on morphology and colour polymorphism failed to find any diagnostic character. Therefore, these mitochondrial lineages may be totally interbreeding presently. To test this hypothesis, we characterized the genetic structure of the complex in the French Mediterranean coast using sequences of mitochondrial DNA (16S) and for the first time, several nuclear DNA markers (introns and microsatellites). The data revealed six phylogenetic lineages corresponding to at least four biological species. These sibling species seem to live in syntopy. However, they seem to display contrasted levels of genetic diversity, suggesting they have distinct demographic histories and/or life‐history traits. Genetic differentiation and isolation‐by‐distance within the French Mediterranean coasts are revealed in three lineages, as expected for a species without a free larval phase. Finally, although recombinant nuclear genotypes are common within mitochondrial lineages, the data set displays a total lack of heterozygotes, suggesting a very high selfing rate, a feature likely to have favoured the formation of the species complex.
Cryptic ecological diversification of a planktonic estuarine copepod, Acartia tonsa
Authors: CHEN GANG , HARE MATTHEW P.
Published: February 2008

The recent discovery of cryptic species in marine holoplankton, organisms that ‘drift’ in oceanic currents throughout their life cycle, contrasts with their potential for long‐distance passive dispersal and presumably high gene flow. These observations suggest that holoplankton species are adapting to surprisingly small‐scale oceanographic features and imply either limited dispersal or strong selection gradients. Acartia tonsa is a widespread and numerically dominant estuarine copepod containing deep mitochondrial lineages within and among populations along the northwestern Atlantic coast. In this study, we intensively investigated A. tonsa populations in Chesapeake Bay with the goals of testing species status for the deep lineages and testing for their association with environmental features over space and time. Phylogenetic analyses of DNA sequences from mitochondrial cytochrome c oxidase I (mtCOI) and the nuclear ribosomal internal transcribed spacer (nITS) resolved two concordant monophyletic clades. Deep divergence between the two clades (13.7% uncorrected sequence divergence for mtCOI and 32.2% for nITS) and genealogical concordance within sympatric populations strongly suggest that the two clades represent reproductively isolated cryptic species. Based on restriction fragment length polymorphisms of mtCOI, representatives from the two clades were found consistently associated with contrasting salinity regimes (oligohaline vs. meso‐polyhaline) with an overlap between 2 and 12 PSU in samples from 1995 to 2005. Finding these patterns in one of the best‐known estuarine copepods reinforces the conclusion that marine biodiversity is underestimated, not only in terms of species numbers, but also with respect to niche partitioning and the potential importance of ecological divergence in marine holoplankton.
How many species are in the genus Batrachuperus? A phylogeographical analysis of the stream salamanders (family Hynobiidae) from southwestern China
Authors: FU JINZHONG , ZENG XIAOMAO
Published: February 2008

Phylogeographical analysis of DNA sequence data has been routinely used to test species boundaries using the monophyly criterion; however, a complementary criterion, reproductive isolation, is often ignored. We used a combination of phylogenetic and population genetic approaches to determine species boundaries among stream salamanders in the genus Batrachuperus. First, cytochrome b sequence data from 174 Batrachuperus individuals, sampled from 78 populations, were used to reconstruct historical relationships within the genus. Second, allozyme data for 14 presumptive nuclear loci, from 463 individuals sampled from 60 populations, were collected and analysed to assess population similarity or disparity, as well as potential reproductive isolation. The DNA sequence data grouped all populations into seven major monophyletic groups, and the allozyme data provided evidence for reproductive isolation among four of the seven groups, thereby supporting the species status of these groups. The allozyme data suggested that two of the other groups share the same gene pool, and therefore belong to a single species. Finally, the allozyme data revealed two reproductively isolated units within the seventh group, which we suggest represents a case of ‘budding speciation’ based on the DNA gene tree. In total, seven species of the genus Batrachuperus were defined, two of which were previously unknown. The phylogeographical analysis also revealed that vicariance events might have dominated the evolutionary history of this group, but the speciation events might precede the formation of the existing mountain topology. This study demonstrates the importance of including frequency data from multiple nuclear gene loci in determining species boundaries.
High paternal diversity in the self‐incompatible herbArabidopsis halleridespite clonal reproduction and spatially restricted pollen dispersal
Authors: LLAURENS V. , CASTRIC V. , AUSTERLITZ F. , VEKEMANS X.
Published: February 2008

The number of sires fertilizing a given dam is a key parameter of the mating system in species with spatially restricted offspring dispersal, since genetic relatedness among maternal sibs determines the intensity of sib competition. In flowering plants, the extent of multiple paternity is determined by factors such as floral biology, properties of the pollen vector, selfing rate, spatial organization of the population, and genetic compatibility between neighbours. To assess the extent of multiple paternity and identify ecological factors involved, we performed a detailed study of mating patterns in a small population of a self‐incompatible clonal herb,Arabidopsis halleri. We mapped and genotyped 364 individuals and 256 of their offspring at 12 microsatellite loci and jointly analysed the level of multiple paternity, pollen and seed dispersal, and spatial genetic structure. We found very low levels of correlated paternity among sibs (Pfull‐sib = 3.8%) indicating high multiple paternity. Our estimate of the outcrossing rate was 98.7%, suggesting functional self‐incompatibility. The pollen dispersal distribution was significantly restricted (mean effective pollen dispersal distance: 4.42 m) but long‐distance successful pollination occurred and immigrating pollen was at most 10% of all pollination events. Patterns of genetic structure indicated little extent of clonal reproduction, and a low but significant spatial genetic structure typical for a self‐incompatible species. Overall, in spite of restricted pollen dispersal, the multiple paternity in this self‐incompatible species was very high, a result that we interpret as a consequence of high plant density and high pollinator service in this population.