bluuebunny/crossref_metadata_2025 huggingface dataset:
Land use and population growth of Primula veris: an experimental demographic approach
Authors: EHRLÉN JOHAN , SYRJÄNEN KIMMO , LEIMU ROOSA , BEGOÑA GARCIA MARIA , LEHTILÄ KARI
Published: April 2005

Changes in land use are the primary cause of decline for many plant species. Efficient management actions for such species must be based on knowledge of the key phases of the plant life cycles that respond most to changes in environmental factors.

To assess how grazing influences population viability of the perennial rosette herb Primula veris, we applied four experimental treatments to abandoned grasslands and recorded the demographic response in permanent plots and seed sowing experiments over 3 years.

Treatments had strong effects on population viability. Transition matrix models showed that cutting the surrounding vegetation had no effect on population growth rate (λ). However, when this was combined with litter removal λ increased to 1·46, compared with 1·11 in controls. With disturbance and complete removal of the surrounding vegetation the effect was even stronger, and λ increased to 1·60.

Increases in λ were primarily a result of increased growth of the smallest rosettes, and increased seedling production. In contrast, the performance of larger P. veris individuals was not affected by experimental treatments.

The higher the elasticity of a particular life cycle transition, the less the change in the transition rate caused by treatments. This suggests that plants are able partly to buffer the effects of environmental variation by minimizing changes in the life cycle transitions that are most important to population growth rate.

Synthesis and applications. Experimental demographic approaches provide an important tool for assessing how grazing and other types of management influence species viability, and help to unravel the mechanisms underlying such relationships. With such information it is possible to predict the effects of novel types of management and land‐use scenarios on population viability. For P. veris, we identified seedling establishment as a key phase in the life cycle, and litter accumulation as a key environmental factor, suggesting that these should be prime targets for management. One practice that is likely to favour as well as seedling establishment preventing litter accumulation is late summer grazing.
Relative importance of burning, mowing and species translocation in the restoration of a former boreal hayfield: responses of plant diversity and the microbial community
Authors: ANTONSEN HILDE , OLSSON PÅL AXEL
Published: April 2005

The extensive loss of species‐rich grasslands in Europe as a result of agricultural intensification has triggered a desire to recreate more diverse and natural grassland systems in set‐aside fields. Appropriate management and species introductions are necessary to overcome residual soil fertility, lack of suitable plant propagules and dominance of undesirable invasive species.

A field experiment was performed in a boreal former hayfield to test the effect of turf inoculation, mowing (twice annually) and spring burning. We surveyed changes in plant diversity, composition and productivity over a 3‐year period. Signature fatty acids and soil respiration measurements were employed to survey changes in the soil community.

Few changes in the vegetation and soil communities could be related to inoculation of turf monoliths. Most of the measured variables in mown plots differed from the set‐aside (control) plots, while burned plots displayed mainly similar responses. Mowing increased plant species richness and diversity, mainly by enhancing the number and frequency of forb species. Small‐statured forb species were promoted by mowing, whereas tall leafy grasses declined. Effects of mowing on soil communities comprised an increased soil respiration and stimulation of arbuscular mycorrhizal fungi.

Synthesis and applications. The results demonstrate the importance of reducing sward height in order to promote plant species coexistence in former boreal hayfields. In such systems, eliminating accumulated litter by spring burning has little influence on species composition when the sward is allowed to grow tall. Mowing is therefore the most efficient way of enhancing biodiversity. The results also show that mowing‐mediated changes in above‐ground plant communities may stimulate below‐ground symbiotic micro‐organisms, potentially resulting in a positive feedback on ecosystem development.
Life after logging: post‐logging recovery of a neotropical bat community
Authors: CLARKE F. M. , ROSTANT L. V. , RACEY P. A.
Published: April 2005

There is considerable debate about whether tropical forests can be managed for timber production and to conserve biodiversity. Few ‘sustainable forestry’ systems have been evaluated adequately in this respect. Microchiropteran bats may be model taxa for this purpose. They are an important component of mammalian diversity, play key roles in forest dynamics and are indicators of disturbance in neotropical forests.

We investigated the effect of Trinidad's periodic block system (PBS) on bat species diversity and community organization. PBS is a polycyclic system of selective logging with a 30‐year harvesting rotation. We captured bats in primary forest and PBS‐managed forest logged 33, 31, 21, 20 and 10 years previously.

Selective logging did not affect species diversity but did affect community structure. Frugivorous bats were significantly more abundant in logged forest whereas gleaning animalivores were more abundant in primary forest, suggesting that frugivores benefited and gleaning animalivores were adversely affected by logging.

The bat community showed evidence of recovery. The number of years since forest disturbance was positively correlated with the abundance and number of species of gleaning animalivores and negatively correlated with the proportional abundance of the most common species. Gleaning animalivores increased in abundance with forest regeneration, whereas the community became less dominated by a single generalist frugivore.

Synthesis and applications. PBS selective logging appears to be compatible with the conservation of bat diversity. This provides evidence that neotropical forests can be managed for timber production in an ecologically sustainable way and that significant biodiversity conservation efforts can occur outside national parks and nature reserves in areas set aside for sustainable development. PBS could serve as a basic blueprint for sustainable forestry in the Guianan Shield where there are forests similar in species composition to those of Trinidad. Key attributes that could be adopted by many tropical countries to manage their forests in an ecologically sustainable way are a low intensity harvest, a long rotation and multiple controls on harvesting.
Molecular evidence for multiple introductions of garlic mustard (Alliaria petiolata, Brassicaceae) to North America
Authors: DURKA WALTER , BOSSDORF OLIVER , PRATI DANIEL , AUGE HARALD
Published: April 2005

Invasive species offer excellent model systems for studying rapid evolutionary change. In this context, molecular markers play an important role because they provide information about pathways of introduction, the amount of genetic variation introduced, and the extent to which founder effects and inbreeding after population bottlenecks may have contributed to evolutionary change. Here, we studied microsatellite variation in eight polymorphic loci among and within 27 native and 26 introduced populations of garlic mustard (Alliaria petiolata), a European herb which is a current serious invader in North American deciduous forests. Overall, introduced populations were genetically less diverse. However, considerable variability was present and when compared to the probable source regions, no bottleneck was evident. Observed heterozygosity was very low and resulted in high inbreeding coefficients, which did not differ significantly between native and introduced populations. Thus, selfing seems to be equally dominant in both ranges. Consequently, there was strong population differentiation in the native (FST = 0.704) and the introduced (FST = 0.789) ranges. The high allelic diversity in the introduced range strongly suggests multiple introductions ofAlliaria petiolatato North America. Out of six European regions, the British Isles, northern Europe, and central Europe had significantly higher proportions of alleles, which are common to the introduced range, and are therefore the most probable source regions. The genetic diversity established by multiple introductions, and the lack of inbreeding depression in this highly selfing species, may have contributed to the invasion success ofAlliaria petiolata.
Maintenance of clonal diversity during a spring bloom of the centric diatom Ditylum brightwellii
Authors: RYNEARSON TATIANA A. , ARMBRUST E. VIRGINIA
Published: April 2005

Maintenance of genetic diversity in eukaryotic microbes reflects a synergism between reproductive mode (asexual vs. sexual) and environmental conditions. We determined clonal diversity in field samples of the planktonic marine diatom, Ditylum brightwellii, during a bloom, when cell number increased by seven‐fold because of rapid asexual division. The genotypes at three microsatellite loci were determined for 607 individual cell lines isolated during the 11 days of sampling. Genetic diversity remained high during the bloom and 87% of the cells sampled each day were genetically distinct. Sixty‐nine clonal lineages were sampled two or more times during the bloom, and two clones were sampled seven times. Based on the frequency of resampled clonal lineages, capture–recapture statistics were used to determine that at least 2400 genetically distinct clonal lineages comprised the bloom population. No significant differences in microsatellite allele frequencies were observed among daily samples indicating that the bloom was comprised of a single population. No sexual stages were observed, although linkage equilibrium at two loci, high levels of allelic and genotypic diversity, and heterozygote deficiencies were all indicative of past sexual reproduction events. At the height of the bloom, a windstorm diluted cell numbers by 51% and coincided with a change in the frequency distribution of some resampled lineages. The extensive clonal diversity generated through past sexual reproduction events coupled with frequent environmental changes appear to prevent individual clonal lineages from becoming numerically dominant, maintaining genetic diversity and the adaptive potential of the population.
The ileocolonic sphincter
Authors: Malbert C‐h.
Published: April 2005

Abstract  The human ileocolonic sphincter (ICS) develops a sustained tone mainly due to propagated and not propagated phasic motor activity. The ileocaecocolonic segment is also able to behave, yet uncommonly, as a synchronized segment involving propagated contractions originating from the ileum and migrating to the proximal colon. The ICS motor activity alone has a limited role towards forward flow. On the contrary, the functional entity corresponding to the distal ileum and the ICS provides a clearance mechanism for reflux of colonic contents into the small intestine. The presence of short chain fatty acids (SCFA) in the distal ileum, sensed either by endocrine cells or chemo‐sensitive vagal afferents, is an important actor in triggering this clearance mechanism. The ICS tone is in part myogenic but a neuronal nitrergic component is also involved. Reflex excitatory and inhibitory responses of the ICS originating from ileal or colonic distension involve primarily spinal nitrergic and adrenergic pathways.
The lower oesophageal sphincter
Authors: Boeckxstaens G. E.
Published: April 2005

Abstract  The lower oesophageal sphincter (LOS) is a specialized segment of the circular muscle layer of the distal oesophagus, accounting for approximately 90% of the basal pressure at the oesophago‐gastric junction. Together with the crural diaphragm, it functions as an antireflux barrier protecting the oesophagus from the caustic gastric content. During swallowing or belching, the LOS muscle must relax briefly in order to allow passage of food or intragastric air. These swallow‐induced and prolonged transient lower oesophageal sphincter relaxations (TLOSRs) respectively result from activation of the inhibitory motor innervation of the sphincter. Both in man and animals, the main neurotransmitter released by the inhibitory neurones is nitric oxide. The two typical examples of dysfunction of the LOS are achalasia and gastro‐oesophageal reflux disease (GORD). Achalasia is characterized by reduction or even absence of the inhibitory innervation to the LOS, leading to impaired LOS relaxation with dysphagia and stasis of food in the oesophagus. On the contrary, GORD results from failure of the antireflux barrier, with increased exposure of the oesophagus to gastric acid. This leads to symptoms such as heartburn and regurgitation, and in more severe cases to oesophagitis, Barrett's oesophagus and even carcinoma. To date, TLOSRs are recognized as the main underlying mechanism, and may represent an important target for treatment. More insight in the pathogenesis of both diseases will undoubtedly lead to new treatments in the near future.
Inheritance of song and stridulatory peg number divergence between Chorthippus brunneus and C. jacobsi, two naturally hybridizing grasshopper species (Orthoptera: Acrididae)
Authors: SALDAMANDO C. I. , MIYAGUCHI S. , TATSUTA H. , KISHINO H. , BRIDLE J. R. , BUTLIN R. K.
Published: April 2005

Knowledge of the genetic basis of divergence in mating signal characters that contribute to reproductive isolation is critical to understanding speciation. Here, we describe a semi‐automated system for characterizing grasshopper acoustic signals. We used this system to study the genetic basis of divergence in three male calling song components [echeme (EL), syllable (SL) and phrase (PL) lengths] between Chorthippus brunneus and C. jacobsi, two species of grasshoppers that hybridize in northern Spain. We also studied the number of pegs in the stridulatory file. For all characters, additive effects accounted for most of the genetic differentiation between species. However, the three song components also showed small but significant epistatic effects. No sex linkage was detected. Wright–Castle–Lande estimates of the minimum numbers of genetic factors underlying song and peg number divergence were low: peg number (ne = 5.87 ± 5.84), SL (ne = 2.37 ± 4.79) and PL (ne = 0.87 ± 0.86). On the other hand, EL appeared to be controlled by many genes. These results suggest that divergence in SL and PL might be driven by sexual selection whereas EL might not be under selection. This is consistent with experimental results on female song preference in related species. However, the fact that few factors appear to underlie the differences in peg number is surprising. Peg number is not closely related to song characteristics. It often varies between closely related grasshopper species and it has been assumed to be a neutral character. The biometrical approaches used here tend to underestimate the number of factors influencing a trait but provide valuable background for subsequent quantitative trait loci analyses.
Evolution of bite force in Darwin's finches: a key role for head width
Authors: HERREL A. , PODOS J. , HUBER S. K. , HENDRY A. P.
Published: April 2005

Studies of Darwin's finches of the Galápagos Islands have provided pivotal insights into the interplay of ecological variation, natural selection, and morphological evolution. Here we document, across nine Darwin's finch species, correlations between morphological variation and bite force capacity. We find that bite force correlates strongly with beak depth and width but only weakly or not at all with beak length, a result that is consistent with prior demonstrations of natural selection on finch beak morphology. We also find that bite force is predicted even more strongly by head width, which exceeds all beak dimensions in predictive strength. To explain this result we suggest that head width determines the maximum size, and thus maximum force generation capacity of finch jaw adductor muscles. We suggest that head width is functionally relevant and may be a previously unrecognized locus of natural selection in these birds, because of its close relationship to bite force capacity.
Direct and correlated responses to artificial selection on male mating frequency in the stalk‐eyed fly Cyrtodiopsis dalmanni
Authors: ROGERS D. W. , BAKER R. H. , CHAPMAN T. , DENNIFF M. , POMIANKOWSKI A. , FOWLER K.
Published: April 2005

Traditionally it was thought that fitness‐related traits such as male mating frequency, with a history of strong directional selection, should have little additive genetic variance and thus respond asymmetrically to bidirectional artificial selection. However, recent findings and theory suggest that a balance between selection for increased male mating frequency and opposing selection pressures on physiologically linked traits will cause male mating frequency to have high additive genetic variation and hence respond symmetrically to selection. We tested these hypotheses in the stalk‐eyed fly, Cyrtodiopsis dalmanni, in which males hold harems comprising many females and so have the opportunity to mate at extremely high frequencies. We subjected male stalk‐eyed flies to artificial selection for increased (‘high’) and decreased (‘low’) mating frequency in the presence of ecologically realistic, high numbers of females. High line males mated significantly more often than control or low line males. The direct response to selection was approximately symmetric in the high and low lines, revealing high additive genetic variation for, and no significant genetic constraints on, increased male mating frequency in C. dalmanni. In order to investigate trade‐offs that might constrain male mating frequency under natural conditions we examined correlated responses to artificial selection. We measured accessory gland length, testis length and eyespan after 7 and 14 generations of selection. High line males had significantly larger accessory glands than low line males. No consistent correlated responses to selection were found in testis length or eyespan. Our results suggest that costs associated with the production and maintenance of large accessory glands, although yet to be identified, are likely to be a major constraint on mating frequency in natural populations of C. dalmanni.
Adaptive evolution in GroEL from distantly related endosymbiotic bacteria of insects
Authors: FARES M. A. , MOYA A. , BARRIO E.
Published: April 2005

Many symbioses between bacteria and insects resulted from ancient infections followed by strict vertical transmission within host lineages. The strong bottlenecks under which this transmission occurs promote the neutral fixation of slightly deleterious mutations by genetic drift. As predicted by Muller's ratchet, this fixation will drive endosymbiotic bacteria through an irreversible dynamics of fitness loss. The chaperonin GroEL has been proposed as a compensatory mechanism whereby endosymbiotic bacteria of aphids persist. Here, we show that endosymbiotic bacteria of insects from two phylogenetically very distant bacterial phyla have fixed amino acid substitutions by positive selection in functionally important GroEL regions involved in either GroES/peptide binding or in the en bloc movement of the GroEL apical domain. These results, together with the high levels of constitutive expression of GroEL in these endosymbionts, provide valuable insights into the evolution of a molecular mechanism responsible for the maintenance of the symbiotic lifestyle.
Lower fecundity in parthenogenetic geckos than sexual relatives in the Australian arid zone
Authors: KEARNEY M. , SHINE R.
Published: April 2005

Theoretical models of the advantage of sexual reproduction typically assume that reproductive output is equal in sexual and parthenogenetic females. We tested this assumption by comparing fecundity between parthenogenetic and sexual races of gekkonid lizards in the Heteronotia binoei complex, collected across a 1200 km latitudinal gradient through the Australian arid zone. Under laboratory conditions, parthenogenetic geckos had approximately 30% lower fecundity when compared with their sexual progenitors, irrespective of body size. Reflecting clutch‐size constraints in gekkonids, this fecundity difference was mainly because of fewer clutches over a shorter period. When parthenogens were compared more broadly with all coexisting sexual races across the latitudinal gradient, parthenogens had lower fecundity than sexuals only when corrected for body size. Differences in fecundity between parthenogens and coexisting sexual races depended on which sexual race was considered. There was no significant relationship between fecundity and parasite (mite) load, despite significantly higher mite loads in parthenogens than in sexual races.
Direct and indirect assortative mating: a multivariate approach to plant flowering schedules
Authors: WEIS ARTHUR E.
Published: April 2005

This paper develops methods to partition the phenotypic correlation between mates for a focal trait – the standard measure for assortative mating – into a direct component and additional indirect components. Indirect assortative mating occurs when a nonassorting trait is correlated within individuals to a directly assorting trait. Direct and indirect assortative mating is assessed for flowering phenology in Brassica rapa. The flowering time of pollen recipients (mothers) was strongly correlated (ρ = 0.67) to that of potential pollen donors (fathers). Similarly, recipients and donors were correlated for duration of their flowering periods (ρ = 0.32) and stem diameters (ρ = 0.52). A partitioning of between‐mate correlations revealed direct assortative mating for flowering time and period duration. However, assortment for stem diameter is explained solely through its correlation to flowering time. Examination of standard quantitative genetic theory shows that indirect assortative mating inflates genetic variance in a focal trait and the genetic covariance between focal and phenotypically correlated traits.
Lectin Histochemical Investigations of the Distal Gut of Chicks with Special Emphasis on the Follicle‐associated Epithelium
Authors: Pohlmeyer I. , Jörns J. , Schumacher U. , Van Damme E. J. M. , Peumans W. J. , Pfüller U. , Neumann U.
Published: April 2005

Carbohydrates on epithelial cell surfaces play an important role as attachment sites for different microorganisms like bacteria, viruses and protozoa. To obtain more information about the distribution of carbohydrates on the luminal surface along the intestine, lectin histochemical studies on different gut segments of chicks of different age groups were carried out using a panel of 13 lectins with specificities for Man, Glc, Gal, GalNAc, GlcNAc or GlcNAc oligosaccharides and Sia. Furthermore, we tried to find out whether previously reported specificities of certain lectins for M cells (membranous or multifold cells) in the bursa of Fabricius (BF) can be observed also on M cells of the intestine. As a result we were able to demonstrate binding of all lectins employed in these studies in all investigated gut segments. In some cases, the application of the same lectin led to varying staining intensities of the same histological structures in different age‐groups (e.g. staining of the brush border with WGA, LEA, MAA or Conarva) or different gut segments (e.g. staining of goblet cells with CMA II, LEA and MPA). Hence, terminal carbohydrate residues of glycoconjugates on the intestinal epithelium vary depending on age and organ site. As glycoconjugates can act as attachment sites for microorganisms, these differences in the distribution of sugar residues may be one explanation for the site‐specificity of certain pathogens. Furthermore, the binding of lectins to the follicle‐associated epithelium (FAE) of the BF differs from that to the FAE of the intestine again stressing the site specificity of lectin binding. Thus, up to now no universal M‐cell marker along the chicken intestine exists.
Biochemical Intestinal Parameters in Germ‐free Minipigs and Rats and in Ex‐germ‐free Minipigs and Rats Monoassociated with Escherichia coli
Authors: Cardona M. E. , Kozakova H. , Collinder E. , Persson A.‐K. , Midtvedt T. , Norin E.
Published: April 2005

Intestinal contents of newborn and young germ‐free minipigs and germ‐free rats were investigated for the following biochemical parameters – conversion of cholesterol to coprostanol, degradation of β‐aspartylglycine, level of tryptic activity, formation of urobilinogen and the profile of short‐chain fatty acids. Additionally, germ‐free minipigs and germ‐free rats were monoassociated with non‐pathogenic strains of Escherichia coli and were investigated for the same biochemical parameters. The conversion of cholesterol to coprostanol, degradation of β‐aspartylglycine, tryptic activity and the short‐chain fatty acid profile were similar to those found in previous studies in germ‐free animals. Slightly higher amounts of urobilinogen than in the other species investigated so far were found in samples from germ‐free and monoassociated minipigs. Except for the total amount of short‐chain fatty acids in rats, monoassociation with E. coli did not alter any of the parameters either in the minipigs or in the rats.
Immunohistochemical Demonstration of Connexin‐Related Epithelization Defects in a Lamb Caused by (Erythro)keratodermia Variabilis
Authors: Meyer W. , Wehrend A. , Schnapper A. , Bostedt H.
Published: April 2005

The distribution of four important connexins (Cx 26, 30, 31, 43) in the skin of a neonatal lamb with (erythro)keratodermia (EKV) was demonstrated using immunohistochemistry, including a very sensitive visualization system. The reaction staining for Cx 26, 30 and 31 was negative to weak in all skin structures, and only Cx 43 displayed weak to moderate positive reactions, although not uniformly distributed throughout the important systems (e.g. epidermis, hair follicle sheaths). Thus, the study proves for the first time that connexin defects are associated with the development of EKV in domesticated mammals, as they are in humans.
Disseminated Acute Concomitant Aspergillosis and Mucormycosis in a Pony
Authors: Thirion‐Delalande C. , Guillot J. , Jensen H. E. , Crespeau F. L. , Bernex F.
Published: April 2005

A 6‐year‐old female pony died after 2 days of prostration. Clinical signs included hyperthermia and abnormal pulmonary auscultation sounds. Necropsy revealed diffuse severe necrohaemorrhagic colitis and splenitis, multiple visceral ecchymoses, petechial haemorrhages in the brain and lungs. Microscopical examination showed acute necrohaemorrhagic colitis, encephalitis, pneumonia and splenitis associated with fibrinoid vasculitis, thrombosis and fungal hyphae within and around vessels. Immunohistologically, concomitant aspergillosis (caused byAspergillus fumigatus) and mucormycosis (causde byAbsidia corymbifera) were identified in the colonic and pulmonary lesions, whereas pure mucormycosis was observed in cerebral and splenic lesions. Dual mycotic infections are very rarely described, and the present case emphasizes the need of immunohistochemistry in order to obtain a clear‐cut diagnosis of mixed fungal infections.
Serum Osteocalcin and CTX‐MMP Concentration in Young Exercising Thoroughbred Racehorses
Authors: Carstanjen B. , Amory H. , Sulon J. , Hars O. , Remy B. , Langlois P. , Lepage O. M.
Published: April 2005

Bone responds to exercise with changes in bone (re‐)modelling, which might be monitored non‐invasively with biochemical bone markers. The aim of this study was to evaluate the influence of exercise on serum osteocalcin and serum carboxy‐terminal cross‐linked telopeptide of type I collagen generated by matrix metalloproteinases (CTX‐MMP) concentration in young racehorses. Seventy‐one 2 to 4‐year‐old Thoroughbreds were included in this prospective infield study. Blood sampling was performed six times (i.e. six sampling cycles) during a 9‐month period. Serum samples were analysed with commercial osteocalcin and CTX‐MMP radioimmunoassays. Two‐year‐old racehorses had higher serum osteocalcin and CTX‐MMP values than 3‐year‐old horses. Gender and training amplitude did not significantly influence serum osteocalcin and CTX‐MMP values. Two‐year‐old horses showed an increase in osteocalcin values between cycles 2 and 3 and an increase in serum CTX‐MMP values between cycles 1 and 2. Serum osteocalcin and CTX‐MMP concentrations decreased between cycles 4 and 5, and 5 and 6. Three‐year‐old horses showed an increase in serum osteocalcin levels between cycles 3 and 4 and an increase in serum CTX‐MMP concentrations between cycles 1 and 2, and 3 and 4. Serum osteocalcin levels decreased between cycles 5 and 6, whereas serum CTX‐MMP levels decreased between cycles 4 and 5, and 5 and 6. Two‐ and three‐year‐old horses showed a decreased osteocalcin/CTX‐MMP ratio between cycles 1 and 2. Moreover, 2‐year‐old horses showed an increase in the osteocalcin/CTX‐MMP ratio between cycles 2 and 3. Sore shin formation did not significantly influence serum osteocalcin and CTX‐MMP values. Serum osteocalcin and CTX‐MMP are promising bone markers for monitoring exercise induced changes in equine bone metabolism.
The dynamics of spatially coupled food webs
Authors: McCann K. S. , Rasmussen J. B. , Umbanhowar J.
Published: April 2005

The dynamics of ecological systems include a bewildering number of biotic interactions that unfold over a vast range of spatial scales. Here, employing simple and general empirical arguments concerning the nature of movement, trophic position and behaviour we outline a general theory concerning the role of space and food web structure on food web stability. We argue that consumers link food webs in space and that this spatial structure combined with relatively rapid behavioural responses by consumers can strongly influence the dynamics of food webs. Employing simple spatially implicit food web models, we show that large mobile consumers are inordinately important in determining the stability, or lack of it, in ecosystems. More specifically, this theory suggests that mobile higher order organisms are potent stabilizers when embedded in a variable, and expansive spatial structure. However, when space is compressed and higher order consumers strongly couple local habitats then mobile consumers can have an inordinate destabilizing effect. Preliminary empirical arguments show consistency with this general theory.
Forest turnover rates follow global and regional patterns of productivity
Authors: Stephenson Nathan L. , van Mantgem Phillip J.
Published: April 2005

Using a global database, we found that forest turnover rates (the average of tree mortality and recruitment rates) parallel broad‐scale patterns of net primary productivity. First, forest turnover was higher in tropical than in temperate forests. Second, as recently demonstrated by others, Amazonian forest turnover was higher on fertile than infertile soils. Third, within temperate latitudes, turnover was highest in angiosperm forests, intermediate in mixed forests, and lowest in gymnosperm forests. Finally, within a single forest physiognomic type, turnover declined sharply with elevation (hence with temperature). These patterns of turnover in populations of trees are broadly similar to the patterns of turnover in populations of plant organs (leaves and roots) found in other studies. Our findings suggest a link between forest mass balance and the population dynamics of trees, and have implications for understanding and predicting the effects of environmental changes on forest structure and terrestrial carbon dynamics.
Ecology of invasive mosquitoes: effects on resident species and on human health
Authors: Juliano Steven A. , Philip Lounibos L.
Published: April 2005

Investigations of biological invasions focus on patterns and processes that are related to introduction, establishment, spread and impacts of introduced species. This review focuses on the ecological interactions operating during invasions by the most prominent group of insect vectors of disease, mosquitoes. First, we review characteristics of non‐native mosquito species that have established viable populations, and those invasive species that have spread widely and had major impacts, testing whether biotic characteristics are associated with the transition from established non‐native to invasive. Second, we review the roles of interspecific competition, apparent competition, predation, intraguild predation and climatic limitation as causes of impacts on residents or as barriers to invasion. We concentrate on the best‐studied invasive mosquito, Aedes albopictus, evaluating the application of basic ecological theory to invasions by Aedes albopictus. We develop a model based on observations of Aedes albopictus for effects of resource competition and predation as barriers to invasion, evaluating which community and ecosystem characteristics favour invasion. Third, we evaluate the ways in which invasive mosquitoes have contributed to outbreaks of human and animal disease, considering specifically whether invasive mosquitoes create novel health threats, or modify disease transmission for existing pathogen–host systems.
Phylogenetic position of Nerillidae and Aberranta (Polychaeta, Annelida), analysed by direct optimization of combined molecular and morphological data
Authors: Worsaae Katrine , Nygren Arne , Rouse Greg W. , Giribet Gonzalo , Persson Jenny , Sundberg Per , Pleijel Fredrik
Published: April 2005

The phylogenetic position of the most speciose meiofaunal polychaete family, Nerillidae, has remained contentious. Recent hypotheses have generally focused on the fact that Nerillidae shares with Aciculata (a major polychaete subgroup) features such as compound chaetae, ventral buccal organ and short ventrolateral palps. Here we present the first phylogenetic analysis of Aciculata, together with Nerillidae, combining morphological and molecular data. We also include Aberrantidae, previously referred to or placed near to spiomorph polychaetes, but recently referred to Aciculata, possibly close to Nerillidae. The data sets of 24 terminals contain 53 morphological characters and nearly complete sequences of 18S rRNA. The sequences were analysed simultaneously with the morphological data by direct optimization in the program POY with a variety of parameter settings (costs of gaps: transversions: transitions). The various settings resulted in markedly different phylogenetic hypotheses, but on the basis of congruence (ILD) the results of two parameter settings were chosen. In all analyses, the three included nerillid species constituted a monophyletic group. Only two analyses provided fully resolved cladograms. The morphological analysis gave poor resolution and the position of the nerillids was equivocal. The two molecular‐based cladograms (minimizing ILD) were also poorly resolved, but one provided a position for nerillids next to Eunice pennata and Nothria conchilega, from the subgroup Eunicida within Aciculata. The two cladograms of the combined analyses (minimizing ILD) were fully resolved and placed nerillids in a terminal position next to Aberranta sp., within a clade of eunicidan species. The study showed that the analytical conditions for the homology assignment of 18S rRNA strongly influenced the phylogenetic results. The various previous proposals on the phylogenetic position of the Nerillidae are reviewed, some of which are in accordance with the results of the present study.
Reassessment of morphological characteristics in freshwater eels (genus Anguilla, Anguillidae) shows congruence with molecular phylogeny estimates
Authors: Lin Yeong‐Shin , Tzeng Chyng‐Shyan , Hwang Jenn‐Kang
Published: April 2005

The morphology‐based phylogeny of freshwater eels, proposed by V. Ege in 1939, has been accepted as the basis of eel classification since that time. However, this has been called into question by recent molecular studies. Most of the morphological characteristics recognized by Ege are morphometric. Since methods for the application of morphometric data to phylogeny construction have not been fully established, it is unclear whether the observed discrepancies between morphological and molecular data arise from intrinsic differences or from flawed analyses. Here, we have used two methods to assemble evolutionary trees from distance matrices constructed according to Ege's data, the neighbor‐joining (NJ) method and the minimum network (MinNet) method; the latter is based on an evolutionary algorithm. After reanalysing Ege's morphological data, we found that both methods gave results consistent with those based on molecular data, although not with Ege's original classification. Therefore, we speculate that some morphological features Ege used to subdivide the eel groups may not be synapomorphic as he proposed, but symplesiomorphic or convergent . The method developed here may prove useful for constructing phylogeny for taxon groups where only continuous morphometric characteristics are recognized, such as the freshwater eels.
Phylogenetic revision of the spider genus Negayan (Araneae, Anyphaenidae, Amaurobioidinae)
Authors: Lopardo Lara
Published: April 2005

A taxonomic revision and phylogenetic analysis of the spider genus Negayan Ramírez, 2003 (Anyphaenidae, Amaurobioidinae, Amaurobioidini) is presented. All 12 known species of Negayan plus representatives of each of the other nine amaurobioidini genera (25 taxa in total) were scored for 134 morphological characters. The cladistic analysis of this matrix results in a single most parsimonious tree (LE = 382; CI = 0.42; CI for informative characters = 0.36; RI = 0.49). The monophyly of Negayan is corroborated, although with low support values. My results correspond to those of a previous study, with N. paduana as the basal species of the genus and Selknamia as the sister‐group of Negayan. Negayan is diagnosed by the genitalic morphology in both sexes. Males of Negayan have a characteristic retrolateral tibial apophysis on palps that is long, thick and sinuous at the tip. Females of Negayan have a characteristic genitalic pattern with coiled copulatory ducts and contiguous spermathecae. New diagnostic characters are proposed. The genus Negayan comprises 12 species, four of them known only from females. It is known from Argentina, Chile and Peru. Eight new species are described here: N. puno sp. nov., N. cerronegro sp. nov., N. tata sp. nov., N. ancha sp. nov., N. enrollada sp. nov., N. tucuman sp. nov., N. tarapaca sp. nov., and N. argentina sp. nov. New morphological data are added to the descriptions of N. tridentata (Simon), N. paduana (Karsch) and N. coccinea (Mello‐Leitão). The male of N. excepta (Tullgren) is described for the first time and the female is redescribed. Negayan tridentata is a senior synonym of Gayenna exigua (Mello‐Leitão); and N. paduana is a senior synonym of Tomopisthes lebruni (Simon).
Genetic association study of adiponectin polymorphisms with risk of Type 2 diabetes mellitus in Korean population
Authors: Lee Y. Y. , Lee N. S. , Cho Y. M. , Moon M. K. , Jung H. S. , Park Y. J. , Park H. J. , Youn B. S. , Lee H. K. , Park K. S. , Shin H. D.
Published: April 2005

Aims  To investigate any association between Type 2 diabetes mellitus and two single nucleotide polymorphisms (SNPs) in the adiponectin gene, T45G and G276T, in the Korean population.

Methods  We genotyped 427 non‐diabetic controls and 493 Type 2 diabetic patients for SNPs T45G and G276T of adiponectin gene, measured plasma adiponectin concentrations, and examined clinical parameters in Koreans.

Results  There were no statistically significant differences in allele frequencies of SNPs 45 and 276 comparing control with Type 2 diabetic subjects (T frequency 68.3% vs. 71.6%, P = 0.13 for SNP45, G frequency 72.2% vs. 68.9%, P = 0.12 for SNP276). The genotype distributions of these SNPs had no association with the risk of Type 2 diabetes and metabolic parameters of insulin resistance. Plasma levels of adiponectin were not statistically different according to T45G and G276T either, in both control and Type 2 diabetic subjects.

Conclusion  The T45G and G276T of the adiponectin gene may not be an important determinant of Type 2 diabetes or insulin resistance in Korean subjects.
Effect of diabetes mellitus and its treatment on ventricular arrhythmias complicating acute myocardial infarction
Authors: Rana J. S. , Mukamal K. J. , Nesto R. W. , Morgan J. P. , Muller J. E. , Mittleman M. A.
Published: April 2005

Aims  To evaluate the effect of diabetes mellitus and its treatment on the risk of arrhythmias among early survivors of acute myocardial infarction.

Research design and method  The Onset Study was conducted in 64 US medical centres. Between August 1989 and September 1996, 3882 patients were interviewed after having an acute myocardial infarction. We used logistic regression models to examine the association of diabetes and its treatment with the risk of ventricular arrhythmia after adjustment for age, gender, hypertension, thrombolytic therapy, smoking, obesity, cardiac medicines and congestive heart failure.

Results  During the index hospitalization, patients with diabetes (n = 814) were less likely to develop ventricular arrhythmias than patients without diabetes (6.8 vs. 13.3%, P < 0.001). The risk of ventricular arrhythmia in patients treated with first generation sulphonylureas or diet alone was similar to patients without diabetes (OR = 0.91; 95% CI, 0.39–2.15, and 0.76; 95% CI, 0.46–1.26, respectively). However, compared with patients without diabetes, the adjusted odds ratio (OR) for ventricular arrhythmias was lower among patients treated with insulin or patients treated with second generation sulphonylureas (OR = 0.54, 95% CI 0.32–0.92; OR = 0.45, 95% CI 0.27–0.75, respectively).

Conclusions  Compared with patients without diabetes, the risk of ventricular arrhythmias complicating acute myocardial infarction is lower in patients with diabetes treated with second generation sulphonylureas or insulin, but not in those treated with first generation sulphonylureas or diet alone. This suggests that differences in the mechanism of action of different sulphonylureas may result in clinically relevant differences in arrhythmic risk.
A case of novel de novo paired box gene 6 (PAX6) mutation with early‐onset diabetes mellitus and aniridia
Authors: Nishi M. , Sasahara M. , Shono T. , Saika S. , Yamamoto Y. , Ohkawa K. , Furuta H. , Nakao T. , Sasaki H. , Nanjo K.
Published: April 2005

Background  Paired box gene 6 (PAX6) is a transcription factor involved in eye development. Mutations of PAX6 cause congenital eye anomalies, such as aniridia. PAX6 is also involved in the development of the endocrine pancreas, and reported to be a genetic factor common to aniridia and glucose intolerance, although the latter is usually mild. Here, we describe a case of PAX6 mutation with early‐onset diabetes mellitus.

Case report  A 27‐year‐old woman was referred to our clinic. She was diagnosed having diabetes at the age of 15 with negative glutamic acid decarboxylase (GAD) antibody. Insulin treatment was started at age 24. Because she had aniridia, PAX6 gene mutation was investigated and a heterozygous 2‐bp deletion (c.402del2) was identified. Her parents did not have aniridia and PAX6 mutations. Heterozygous PAX6 mutation may cause glucose intolerance. However, cases of early‐onset diabetes mellitus have not been reported. Her parents did not have diabetes, but their insulinogenic indices were low (0.25 and 0.3, respectively). We thought her early‐onset diabetes was partly as a result of PAX6 mutation and partly because of an unknown insulin secretory defect inherited from her parents. We could not find any mutations in HNF‐1α, ‐1β, ‐4α, IPF‐1, ISL‐1, BEAT2/NeuroD1, PAX4, and amylin genes.

Conclusions  We report a case of PAX6 gene mutation with early‐onset diabetes mellitus and aniridia. Low insulin secretory capacity in her parents suggested that her insulin secretory defect is as a result of not only PAX6 mutation but other genetic factors inherited from her parents.
Changing patterns of primary care for diabetes in Trinidad and Tobago over 10 years
Authors: Mahabir D. , Gulliford M. C.
Published: April 2005

Objective  To evaluate standards of preventive medical care for Type 2 diabetes in the context of high prevalence and limited resources.

Methods  Surveys of records for diabetic subjects attending 23 government primary care health centres in Trinidad and Tobago in 2003 and 1998 and nine health centres in 1993. Records were compared by study year for blood glucose and blood pressure, surveillance for complications, appropriate management advice and drug prescriptions. Relevant interventions included new clinical guidelines, training workshops for clinical staff and reports to the Ministry of Health. During this time, investment in primary care increased in the context of health sector reform policies and a favourable macroeconomic environment.

Results  Comparing 1993 with 2003, the proportion with a blood glucose test in the past 12 months increased from 33% to 91%, urea or creatinine ever recorded increased from 14% to 61%, diet advice recorded in the first 12 months of follow‐up from 35% to 67%, exercise advice from 3% to 61%. The proportion prescribed metformin increased from 25% to 65%, while chlorpropamide decreased from 48% to 0%. The proportion of all subjects treated with antihypertensive drugs increased from 49% to 70%, and the proportion of treated patients prescribed angiotensin‐converting enzyme inhibitors increased from 8% to 72%. Most recent ever records of blood glucose, blood pressure and body weight showed no decrease.

Conclusions  Repeated surveillance of processes of care provided information to stimulate and plan change. Process changes were associated with intervention at several levels and increased availability of resources.
Prevalence of obesity in Korea
Authors: Kim D. M. , Ahn C. W. , Nam S. Y.
Published: April 2005

During the past decade, obesity has substantially increased in Korea, and this is leading to dramatic increases in complications such as type 2 diabetes. In this review, we discuss the past and the current situation of obesity in Korea based on the national health and nutrition surveys of 1995, 1998, and 2001. Because Korea is geographically isolated with relatively few migrants and has a low level of genetic heterogeneity, this report demonstrates the impact of environmental factors on the development of obesity beyond epidemiological information about one of the Asian countries. The third national health and nutrition survey reported in 2001 announced that the overall prevalence of obesity [body mass index (BMI) ≥ 25.0 kg m−2] in Korean adults is 30.6% (32.4% in men and 29.4% in women). The prevalence of obesity in adults and children has increased rapidly from 1990s through the beginning of the new millennium and is steadily increasing in parallel with our rapid socio‐economic progress. In particular, special attention should be paid to two groups in hormonal transition: first, middle‐aged men and women who experience a great increase in body weight, BMI and waist circumference because of andropause or menopause, and second, adolescents in middle to high school who are preparing for qualification or entrance examinations and are prone to overnutrition or nutritional imbalance and physical inactivity.