bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inducible defences and the paradox of enrichment
Authors: Vos Matthijs , Kooi Bob W. , DeAngelis Donald L. , Mooij Wolf M. 
Published: May 2004

In order to evaluate the effects of inducible defences on community stability and persistence, we analyzed models of bitrophic and tritrophic food chains that incorporate consumer‐induced polymorphisms. These models predict that intra‐specific heterogeneity in defence levels resolves the paradox of enrichment for a range of top‐down effects that affect consumer death rates and for all possible levels of primary productivity. We show analytically that this stability can be understood in terms of differences in handling times on the different prey types. Our predictions still hold when defences also affect consumer attack rates. The predicted stability occurs in both bitrophic and tritrophic food chains.Inducible defences may promote population persistence in tritrophic food chains. Here the minimum densities of cycling populations remain bound away from zero, thus decreasing the risk of population extinctions. However, the reverse can be true for the equivalent bitrophic predator–prey model. This shows that theoretical extrapolations from simple to complex communities should be made with caution. Our results show that inducible defences are among the ecological factors that promote stability in multitrophic communities.
Escaping the Bonferroni iron claw in ecological studies
Authors: García Luis V. 
Published: May 2004

I analyze some criticisms made about the application of alpha‐inflation correction procedures to repeated‐test tables in ecological studies. Common pitfalls during application, the statistical properties of many ecological datasets, and the strong control of the tablewise error rate made by the widely used sequential Bonferroni procedures, seem to be responsible for some ‘illogical’ results when such corrections are applied. Sharpened Bonferroni‐type procedures may alleviate the decrease in power associated to standard methods as the number of tests increases.More powerful methods, based on controlling the false discovery rate (FDR), deserve a more frequent use in ecological studies, especially in those involving large repeated‐test tables in which several or many individual null hypotheses have been rejected, and the most significant p‐value is relatively large.I conclude that some reasonable control of alpha inflation is required of authors as a safeguard against striking, but spurious findings, which may strongly affect the credibility of ecological research.
What causes the decrease in haematocrit during egg production?
Authors: WILLIAMS T. D. , CHALLENGER W. O. , CHRISTIANS J. K. , EVANSON M. , LOVE O. , VEZINA F. 
Published: May 2004

Summary

Anaemia has been reported in wild animals, typically associated with traumatic events or ill health. However, female birds routinely become ‘anaemic’ during egg‐laying; we sought to determine the causes of this reduction in haematocrit.
Haematocrit in female European Starlings (Sturnus vulgaris Linnaeus) decreased between pre‐breeding and egg‐laying in 3 out of 4 years (the decrease was marginally non‐significant in the fourth year). This was independent of changes in ambient temperature altering the metabolic requirements for thermoregulation.
There was a positive relationship between haematocrit and plasma levels of the yolk precursor vitellogenin among egg‐laying birds, supporting the hypothesis that the initial reduction in haematocrit is caused by increased blood volume associated with osmoregulatory adjustments to elevated levels of yolk precursors.
However, haematocrit did not always recover upon cessation of egg production, remaining low at clutch completion (2 of 4 years), incubation (1 of 2 years) and chick rearing (1 of 4 years), suggesting an additional cause of the prolonged reduction in haematocrit.
Given the magnitude and prolonged nature of the changes in haematocrit we report, and the interannual variation in haematocrit even during chick‐rearing (47–54%), we suggest that ‘anaemia’ associated with egg production might have implications for aerobic performance during later stages of breeding.
Morphological plasticity of shade‐tolerant tropical rainforest tree seedlings exposed to light changes
Authors: BLOOR J. M. G. , GRUBB P. J. 
Published: May 2004

Summary

Previous studies on tropical rainforest seedlings have demonstrated low physiological plasticity in shade‐tolerant species in response to light, but little is known about the morphological plasticity of such species. We examined morphological traits in seedlings of 10 shade‐tolerant tropical rainforest tree species grown in four combinations of high and low light (10 and 0·8% full daylight, respectively). Plasticity of each trait was quantified using coefficients of variation.
Plant traits varied in their plasticity, and could broadly be ranked as follows: stem form > crown traits > root form > leaf form > biomass allocation. Acclimation to an increase in light was generally greater than acclimation to a decrease in light, but crown traits showed significant changes in the high–low treatment.
The ranking of species according to plasticity varied depending on the trait examined. Mean plasticity across all light treatments showed no relationship with either dry mass or relative growth rate of dry mass (RGRM) across species. However, plasticity in stem mass fraction (fraction of stem to total dry mass) was negatively correlated with low‐light RGRM across species.
Principal components analysis indicated clustering of species depending on trait plasticity. These results suggest different strategies of light response among shade‐tolerant tropical tree seedlings.
An ecological evaluation of Eagleson's optimality hypotheses
Authors: KERKHOFF A. J. , MARTENS S. N. , MILNE B. T. 
Published: May 2004

Summary

The pioneering work of Peter Eagleson has been proposed as a theoretical basis for ecohydrology. Central to the theory are three ‘ecological optimality hypotheses’ which represent ecologically important aspects of atmosphere–soil–vegetation interactions.
The model and its underlying assumptions have never been evaluated in an explicitly ecological context. We examine each of the three optimality hypotheses in turn and test the ability of the model to make ecologically relevant predictions using climate, soil and vegetation data from a semi‐arid woodland site in central New Mexico, USA.
We find that all three of the optimality hypotheses are ecologically flawed. While we could qualitatively reproduce previously published results, model behaviour under novel conditions was highly variable and frequently unrealistic.
The poor performance of the model was probably due to the inadequate treatment of water‐limited transpiration in its original derivation. The theory thus requires redevelopment for ecological application, and we suggest several strands of research that could contribute to its improvement.
Plant palatability can be inferred from a single‐date feeding trial
Authors: ELGER A. , BARRAT‐SEGRETAIN M. H. 
Published: May 2004

Summary

Most studies of plant palatability do not consider its seasonal variability, and infer general life‐history patterns from single‐date feeding experiments. This paper investigates whether different seasonal patterns in the palatability of perennial plant species in one community can alter their relative susceptibility to grazing.
The palatability of eight freshwater macrophyte species growing at the same site was monitored during 1 year through nine consecutive feeding experiments using a generalist consumer, the pond snail Lymnaea stagnalis.
Plant palatability varied significantly throughout the year, and reached its maximum in autumn. Beyond this general trend, seasonal patterns in palatability differed markedly between species, and two (Callitriche platycarpa and Nuphar lutea) showed no significant seasonal variations.
Despite the interspecific differences in seasonal patterns of palatability, species’ palatability rankings remained stable throughout the year. Therefore feeding experiments performed at a single sampling date are suitable to assess the relative palatability of a set of species.
Spatial interactions between the hemiparasitic angiosperm Rhinanthus minor and its host are species‐specific
Authors: KEITH A. M. , CAMERON D. D. , SEEL W. E. 
Published: May 2004

Summary

Effects of organisms that obtain resources from others (e.g. herbivores) can depend on the location of resource removal with respect to their ‘prey’. We investigated whether such an effect can be seen in hemiparasitic plant–host plant interactions.
We conducted rhizotron studies of the interactions between Rhinanthus minor and individuals of two common host species, Festuca rubra and Festuca ovina. Parasites were grown at two distances from the host, and growth characteristics of hosts and parasites measured over time.
Parasites close to their host suffered reduced survival as a result of shading. Without shading these parasites attached earlier, produced more haustoria, grew larger and had a greater fecundity than those planted further away. This effect was significant for parasites infecting the fast‐growing F. rubra, but not for parasites infecting the less vigorous F. ovina. Effect of parasite position on host biomass was significant only for F. rubra, which showed a greater reduction when infected by more proximal parasites.
Differences in the response of hosts to infection, and parasite growth, suggest the effect of the position of R. minor is host‐species specific.
The functional significance of synchronous protandry in Alstroemeria aurea
Authors: HARDER L. D. , AIZEN M. A. 
Published: May 2004

Summary

Synchronous dichogamy, the simultaneous change in sex phases of all flowers in an inflorescence or entire plant, has been proposed to reduce self‐pollination between flowers within a plant (geitonogamy) and so should leave more pollen for export and/or reduce inbreeding. We tested these hypotheses with Alstroemeria aurea Graham, a self‐compatible, clonal herb with synchronous protandrous inflorescences.
We manipulated A. aurea inflorescences to compare pollen export, pollen receipt and pollen‐tube attrition in synchronous and asynchronous inflorescences. We constructed asynchronous inflorescences by tying together female‐ and male‐phase ramets which were collected within 1 m of each other and so had a high probability of being genetically related.
Inflorescences with both male‐ and female‐phase flowers received 27% more pollen than synchronous inflorescences, which was associated with higher pollen‐tube attrition. The selfing suggested by these results would reduce genetic contributions to the next generation as a result of the strong inbreeding depression found in this species.
In contrast, we found no evidence that asynchronous inflorescences exported less pollen to companion female‐phase inflorescences than did synchronous inflorescences.
Our results suggest that synchronous dichogamy evolves primarily as an anti‐selfing mechanism, rather than to promote outcross siring success.
Regulation of development time and hatch synchronization in Black Brant (Branta bernicla nigricans)
Authors: NICOLAI C. A. , S. SEDINGER J. , WEGE M. L. 
Published: May 2004

Summary

Eggs of precocial bird clutches hatch more synchronously than they are laid. The widely accepted hypothesis to explain hatching synchrony has been that vocalizations from earlier laid embryos accelerate development of later laid embryos. The relationship between position in the laying sequence (hereafter PILS) and time to hatching was investigated in Black Brant (Branta bernicla nigricans L.; hereafter brant). Factors associated with variation in incubation duration were also examined.
Experimental clutches comprising eggs laid on the same day from the same PILS were assembled to eliminate the effects of earlier laid eggs on those laid later. This experiment allowed us to examine developmental time in clutches without the effects of interactions between eggs laid earlier in the sequence and those laid later. In a separate experiment, clutches were manipulated so that the full complement of laying sequences was maintained in each clutch, but each egg originated from a different female. This experiment allowed us to separate the influences of genetic‐maternal effects from the influence of nest environment and incubation behaviour. Developmental time was also monitored in a set of clutches that were unmanipulated.
Metabolic rates of eggs from each PILS were measured at mid‐incubation and the day before hatch for both experimental and control nests. By measuring metabolic rates, it was possible to examine changes in metabolic rates of embryos as hatch approaches, which may be another mechanism to synchronize hatch.
No difference was detected in incubation period between control and manipulated clutches. There was a steady decline in incubation period from first to last laid eggs independent of the clutch type. Fifth laid eggs required >3 days less to hatch than those laid first. These data suggest that sounds produced by brood mates and/or female incubation patterns are not the principal mechanisms for hatching synchrony. Both genetic and host mothers influenced overall developmental time, indicating that genetic‐maternal effects and incubation behaviour and nest environment also influenced developmental time.
Embryonic metabolic rate was negatively correlated with number of days before hatch, but there was not a positive relationship between PILS and metabolic rate. Our findings show that embryonic metabolic rate may affect development more than vocalizations between brood members in synchronizing hatch.
Within‐brood size differences, sex and parasites determine blood stress protein levels in Eurasian Kestrel nestlings
Authors: MARTÍNEZ‐PADILLA J. , MARTÍNEZ J. , DÁVILA J. A. , MERINO S. , MORENO J. , MILLÁN J. 
Published: May 2004

SummaryBrood hierarchies established through hatching asynchrony are supposed to be costly for small chicks because of impaired growth and survival. An additional cost that has remained unexplored is the stress imposed by competition for resources in the nest.In the present study of broods of Eurasian kestrels, we have used the level of heat shock proteins such as Hsp60 and Hsp70 in peripheral blood as well as the heterophile/lymphocyte ratio to detect stress in nestlings. The sex of nestlings and theirCaryosporasp. oocyst excretion were included in analyses.Nestlings showing a large size difference with respect to their largest sibling had higher levels of both stress proteins, and this effect was stronger for female chicks as indicated by a significant interaction sex × size difference, presumably because of their higher food requirements for growth. Nestlings for which the largest sibling was a female had higher levels of Hsp60 than when it was a male. The heterophile/lymphocyte index was a much poorer predictor of competitive stress.Stress proteins are effective estimators of competitive, nutritional and parasite‐mediated stress of nestlings in the wild. The cost of sustained stress has to be included in future analyses of the fitness repercussions of dominance hierarchies in avian broods.
Ethical Issues in Dialysis: Institutionalized Racism and End‐Stage Renal Disease: Is Its Impact Real or Illusionary?
Authors: Spital Aaron , Callender Clive O. , Miles Patrice V. 
Published: May 2004

ABSTRACTRacism is the subjugation of one group (superior) over another (inferior) and may be divided into two categories: overt (gross) and covert. Covert racism (subconscious) is categorized as institutionalized racism. Although institutionalized racism is a more tolerant and restrained practice of this superior/inferior ethnic construct in which African Americans or other people of color are treated as inferiors, it has led to important health disparities between blacks and whites. One area where its mark is most indelible is in the treatment of end‐stage renal disease (ESRD).
Reviews: Residual Renal Function: Considerations on Its Importance and Preservation in Dialysis Patients
Authors: Chandna Shahid M. , Farrington Ken 
Published: May 2004

ABSTRACTResidual renal function (RRF) remains important even after commencement of dialysis. Its role in the adequacy of peritoneal dialysis (PD) is well recognized and is increasingly utilized in incremental PD regimes, but it is also vitally important in hemodialysis (HD) patients, in whom it, as in PD patients, may improve survival. It may allow for a reduction in the duration of HD sessions. It reduces the need for dietary and fluid restrictions in both PD and HD patients. Other contributions include improved middle molecule clearance, better hemoglobin, phosphate, potassium, and urate levels, enhanced nutritional status and quality of life scores, and better outcomes in pregnancy. On the negative side, hypoalbuminemia may be prolonged in patients with persistent nephrotic‐range proteinuria. Contrary to popular belief, RRF does not necessarily decline rapidly with the initiation of HD. PD may be better than HD in preserving RRF, although this difference may not persist if biocompatible membranes, bicarbonate buffer, and ultrapure water are used. Nocturnal ambulatory peritoneal dialysis (APD) patients may fare worse than continuous ambulatory peritoneal dialysis (CAPD) patients. RRF can be adversely affected by angiotensin‐converting enzyme (ACE) inhibitors, nonsteroidal anti‐inflammatory drugs (NSAIDs), aminoglycosides, and radiocontrast agents. Diuretics can help maintain fluid balance but not RRF.
The Consequences of Uncontrolled Secondary Hyperparathyroidism and Its Treatment in Chronic Kidney Disease
Authors: Goodman William G. 
Published: May 2004

ABSTRACTSecondary hyperparathyroidism (HPT) is a common complication of chronic kidney disease (CKD) and a frequent cause of clinically significant bone disease. Soft‐tissue and vascular calcification, cardiovascular disease, and calcific uremic arteriolopathy (CUA) are additional serious consequences of the disorder that may contribute directly to cardiovascular morbidity and mortality in patients with CKD. Less widely appreciated manifestations include neurological disturbances, hematological abnormalities, and endocrine dysfunction. Secondary HPT arises from alterations in calcium, phosphorus, and vitamin D metabolism that develop early in the course of CKD and become more pronounced as kidney function declines. Treatment is often delayed, however, until the disease is well established. Current therapeutic strategies rely largely on the use of vitamin D sterols to diminish excess parathyroid hormone (PTH) synthesis and to lower serum or plasma PTH levels, but their use is often confounded by increases in serum calcium and phosphorus concentrations, changes that can aggravate soft‐tissue and vascular calcification. As such, there is a need for new therapeutic interventions that can effectively lower serum or plasma PTH levels without producing untoward side effects. The current review summarizes the diverse manifestations of secondary HPT in patients with CKD. The consequences of inadequately controlled secondary HPT and the adverse effects of selected therapeutic interventions for the disorder on vascular calcification and cardiovascular disease in those with CKD are discussed.
Potential impact of climatic change on the distribution of forest herbs in Europe
Authors: Skov Flemming , Svenning Jens‐Christian 
Published: May 2004

The aim of this study is to evaluate the possible consequences of climate change on a representative sample of forest herbs in Europe. A fuzzy climatic envelope was used to predict the location of suitable climatic conditions under two climatic change scenarios. Expected consequences in terms of lost and gained range size and shift in distribution for 26 forest herbs were estimated. These results were combined in an Index of Predicted Range Change for each species. Finally, the effects of habitat fragmentation for potential dispersal routes were evaluated and options for management on a European scale are discussed.Generally, a good agreement of the estimated suitability under the present climate and the observed current distribution was observed. However, species vary a lot in the degree to which they occupy the presently climatically suitable areas in Europe. Many species are absent from large areas with suitable climate and thus could be said to have poor range‐filling capacity.A general change in location (range centroid) of the total suitable area was observed: The total suitable area will on average move strongly northwards and moderately eastwards under the relatively mild B1 scenario and more strongly so under the A2 scenario. The required average minimum migration rate per year to track the potential range shift is 2.1 km under the B1 scenario and 3.9 km under the A2 scenario.Moderate losses in the total suitable area in Europe are predicted for most species under both scenarios. However, the predicted changes are very variable, with one species (Actaea erythrocarpa) experiencing total range elimination in Europe (A2 scenario) while the total suitable area is predicted to show large increases for other species. The species that are predicted to experience the greatest proportional losses in their climatically suitable area within their presently realised range tend to have northern or eastern range centroids.The Index of Predicted Range Change roughly divides the species studied in four groups: One species face a high risk of extinction; eight species are expected to experience moderate to severe threat of extinction; 11 species are not considered at risk and, finally, six species may actually benefit from global warming.An analysis of potential migration routes shows the importance of maintaining and, if possible, improving the network of forest throughout Europe to make migration possible. It is also suggested to closely monitor the status of boreal and subalpine species that are most threatened by global warming. Finally it is recommended that special concern should be given to increased protection and restoration of forest habitats in southern montane areas for their crucial long‐term importance for the maintenance of European plant diversity.
The roles of interleukin-18 in collagen-induced arthritis in the BB rat
Authors: YE X J , TANG B , MA Z , KANG A H , MYERS L K , CREMER M A 
Published: May 2004

SUMMARYInterleukin (IL)-18 is a member of the IL-1 cytokine family. Its expression is increased in rheumatoid arthritis synovium, and its proinflammatory effects have been demonstrated in experimental models of murine arthritis. Here, we investigate the actions of varying doses of recombinant rat IL-18 (rIL-18) on the course of type II collagen-induced arthritis (CIA) in BB rats, including clinical and immune events, plus splenic cytokine production. Small doses of rIL-18 (10 and 50 µg/rat) administered intraperitoneally (i.p.) increased arthritis incidence and severity (P &lt; 0·01) when a low-potency CII preparation was used for immunization. IgG1 and IgG2a anti-CII antibody levels were significantly greater in rats given 10 and 50 µg rIL-18 doses than controls. rIL-18 significantly increased levels of proinflammatory cytokines [interferon (IFN)-γ, IL-2, tumour necrosis factor (TNF)-α and IL-6] produced by splenocyte cultures. Larger doses of rIL-18 (300 µg/rat) suppressed arthritis and immunity. To ascertain whether the pro-arthritic effects of IL-18 could be attenuated, rats were treated with neutralizing rabbit anti-rIL-18 IgG before immunization with a high-potency CII preparation. When given serially for 3 weeks, the incidence and severity of CIA, in addition to anti-CII IgG2a and splenic IL-6 and IFN-γ production, were all significantly reduced. Similar results were noted when antibody was given twice, just before arthritis onset. These results demonstrate that IL-18 plays an important proinflammatory role in the pathogenesis of CIA which is achieved, in part, by an immunostimulatory action. Neutralizing endogenous IL-18 with antibodies attenuated CIA, CII immunity and cytokine responses. These studies support the use of IL-18 antagonists as treatments for inflammatory arthritis.