bluuebunny/crossref_metadata_2025_split huggingface dataset:
Plasticity in leaf traits of 38 tropical tree species in response to light; relationships with light demand and adult stature
Authors: ROZENDAAL D. M. A. , HURTADO V. H. , POORTER L. 
Published: May 2006

Summary

The sun–shade acclimation and plasticity of 16 functional leaf traits of 38 tropical tree species were studied in relation to their light demand, maximum adult stature and ontogenetic changes in crown exposure.
Species differed significantly in all leaf traits, which explained a large part of the observed variation (average R2 = 0·72). Light had a significant effect on 12 traits and species showed a similar proportional response to light, indicating that the species ranking in trait performance is largely maintained in different light environments.
Specific leaf area, leaf nutrient content and chlorophyll : nitrogen ratio showed the largest plasticity to irradiance. These traits are important for maximizing growth in different light conditions because they are closely linked to the photosynthetic capacity and carbon balance of the plant.
Plasticity is generally thought to be greatest for pioneer species that occupy early successional habitats with a large variation in irradiance. This hypothesis was rejected because short‐lived pioneers showed the lowest plasticity to irradiance.
An alternative hypothesis states that plasticity is largest for tall species that experience large ontogenetic changes in irradiance during their life cycle. Yet plasticity was barely related to adult stature or ontogenetic changes in crown exposure. Short‐lived pioneers that experience consistently high light levels did have low plasticity, but shade‐tolerant species that experience consistently low light levels had high plasticity.
Tropical rainforest species show a large variation in plasticity. Plasticity is a compromise between many factors and constraints, and all of these may explain the observed patterns to some extent.
Maternal effects in Wood Ducks: incubation temperature influences incubation period and neonate phenotype
Authors: HEPP G. R. , KENNAMER R. A. , JOHNSON M. H. 
Published: May 2006

SummaryMaternal effects often explain a significant amount of variation in offspring phenotype, and can be important in the evolution of life histories. Incubation of eggs is an important maternal effect, and optimal growth and development of avian embryos takes place within a narrow range of incubation temperatures, but the effect of incubation microclimate on neonate phenotype remains relatively unexplored in birds.In this study of Wood Ducks (Aix sponsaLinnaeus) we examined effects of incubation temperature on the length of incubation period and neonate quality. We monitored nest temperatures and incubation periods of naturally incubated Wood Duck nests and found a strong inverse relationship between incubation period and average nest temperature.Next, we collected three unincubated eggs from each of 48 nests, and randomly assigned eggs from each nest to one of three incubation temperatures (34·6, 36·0 and 37·4 °C). Experimental incubation temperatures overlapped average nest temperatures of naturally incubated Wood Duck nests.Hatching success varied with incubation temperature and was lowest for eggs incubated at the lowest temperature. Incubation period of experimental eggs decreased with increasing temperature but was not affected by fresh egg mass.Wood Duck embryos catabolized an estimated 34–38% of egg lipids and 25–33% of egg protein during incubation. Percentage change of lipids increased with decreasing incubation temperature, but not significantly. Embryos incubated at lower temperatures used a greater percentage of protein than embryos incubated at higher temperatures.In analyses using fresh egg mass as the covariate, we found that wet and dry mass of ducklings increased with increasing incubation temperature. Decreases in lipid content of Wood Duck neonates with decreasing incubation temperature were not significant, but eggs incubated at low temperatures produced ducklings that had reduced protein mass and that were structurally larger than ducklings from eggs incubated at high temperatures.Our study illustrates the importance of incubation temperature on the development of Wood Duck embryos. Decisions made by incubating parents that influence egg temperature can modify incubation period and offspring phenotype. Investigations of incubation as a reproductive cost should consider how parental decisions influence both parents and offspring.
Dependence on p38 MAPK signalling in the up‐regulation ofTLR2,TLR4andTLR9gene expression inTrichomonas vaginalis‐treated HeLa cells
Authors: Chang Jae‐Ho , Park Ju‐Youn , Kim Soo‐Ki 
Published: May 2006

SummaryToll‐like receptors (TLRs) are pattern recognition receptors (PRRs) that recognize conserved pathogen‐associated molecular patterns (PAMPs) synthesized by micro‐organisms. Despite the essential requirement for TLRs in prokaryotic infection, the pattern and regulation ofTLRgene expression byTrichomonas vaginalisin the mucocutaneous barrier are still unknown. Our hypothesis is thatT. vaginalis‐infected epithelial cells are major effector cells in the skin barrier. These cells function as a central regulator ofTLRgene expression, thus accelerating the process of barrier dysfunction via increased release of chemokines and proinflammatory cytokines. To test this hypothesis, RT‐PCR was performed onTLRs, interleukin (IL)‐8 and tumour necrosis factor (TNF)‐α. Stimulation of HeLa cells byT. vaginaliswas observed to up‐regulateTLR2,4and9mRNA expression as well as that ofIL‐8andTNF‐α. To further clarify the molecular mechanism of barrier devastation triggered by these up‐regulatory stimuli, we examined the profiles of extracellular signal‐regulated kinase (ERK), p38 mitogen‐activated protein kinase (MAPK) and nuclear factor (NF)‐κB activation in HeLa cells using specific inhibitors. Interestingly, pretreatment of HeLa cells with the p38 MAPK inhibitor SB203580 demonstrated inhibition ofT. vaginalis‐induced up‐regulation ofTLR2,4, and9mRNA expression. By contrast, inhibition of ERK or NF‐κB activation failed to blockT. vaginalis‐induced up‐regulation ofTLR9mRNA expression orTLR2andTLR4mRNA expression, respectively. In addition, pretreatment with SB203580 reduced epithelium‐derived IL‐8 and TNF‐α release evoked byT. vaginalis. Our results show thatT. vaginalisinfection of the mucocutaneous barrier could up‐regulateTLR2,4and9gene expression via the p38 MAPK signalling pathway in epithelial cells; this process then leads to modulation of p38 MAPK‐dependent IL‐8 and TNF‐α release from the epithelium.
Lyme borreliosis reinfection: might it be explained by a gender difference in immune response?
Authors: Jarefors Sara , Bennet Louise , You Elin , Forsberg Pia , Ekerfelt Christina , Berglund Johan , Ernerudh Jan 
Published: May 2006

SummaryLyme borreliosis is a tick‐borne disease often manifesting as a circular skin lesion. This cutaneous form of the disease is known as erythema migrans. In a 5‐year follow‐up study in southern Sweden, 31 of 708 individuals initially diagnosed with erythema migrans and treated with antibiotics were found to be reinfected with Borrelia burgdorferi. Although men and women were tick‐bitten to the same extent, 27 of the 31 reinfected individuals were women, all of whom were over 44 years of age. The aim of this study was to determine whether this discrepancy in gender distribution could be a result of differences in immunological response. Twenty single‐infected and 21 reinfected women and 18 single‐infected and three reinfected men were included in the study. None of the participants showed any sign of an ongoing B. burgdorferi infection, and thus the habitual response was captured. Lymphocytes were separated from blood and stimulated with antigens. The secretion of interleukin (IL)‐4, IL‐6, IL‐10, interferon (IFN)‐γ and tumour necrosis factor (TNF)‐α was measured by enzyme‐linked immunosorbent assay (ELISA), enzyme‐linked immunosorbent spot‐forming cell assay (ELISPOT) or Immulite. No difference was detected in cytokine secretion between single‐infected and reinfected individuals. We also compared the immunological response in men and women, regardless of the number of B. burgdorferi infections. Women displayed a significantly higher spontaneous secretion of all cytokines measured. The ratios of IL‐4:IFN‐γ and IL‐10:TNF‐α were significantly higher in women. Gender differences in immune reactivity might in part explain the higher incidence of reinfection in women. The higher IL‐4:IFN‐γ and IL‐10:TNF‐α ratios seen in women indicate that postmenopausal women have T helper type 2 (Th2)‐directed reactivity with impaired inflammatory responses which might inhibit the elimination of spirochetes.
Cytotoxic T lymphocyte antigen‐4‐dependent down‐modulation of costimulatory molecules on dendritic cells in CD4+ CD25+ regulatory T‐cell‐mediated suppression
Authors: Oderup Cecilia , Cederbom Lukas , Makowska Anna , Cilio Corrado M. , Ivars Fredrik 
Published: May 2006

SummaryWe have previously demonstrated that CD4+ CD25+ natural regulatory T cells (Treg cells) induce down‐modulation of CD80 and CD86 (B7) molecules on dendritic cells (DCs) in vitro. In this report we show that the extent of down‐modulation is functionally significant because Treg‐cell conditioned DCs induced poor T‐cell proliferation responses. Further, we report that down‐modulation was induced rapidly and was inhibited by blocking cytotoxic T lymphocyte antigen‐4 (CTLA‐4), which is constitutively expressed by the Treg cells. Even though Treg cells have previously been reported to kill antigen‐presenting cells, the down‐modulation was not due to selective killing of DCs expressing high level of the costimulatory molecules. We propose that Treg cells down‐modulate B7‐molecules on DCs in a CTLA‐4‐dependent way, thereby enhancing suppression of T‐cell activity.
Tumoristatic effects of anti‐CD40 mAb‐activated macrophages involve nitric oxide and tumour necrosis factor‐α
Authors: Lum Hillary D. , Buhtoiarov Ilia N. , Schmidt Brian E. , Berke Gideon , Paulnock Donna M. , Sondel Paul M. , Rakhmilevich Alexander L. 
Published: May 2006

SummaryEffector cells of the innate immune system have diverse functions that can result in tumour inhibition or tumour progression. Activation of macrophages by CD40 ligation has been shown to induce antitumour effects in vitro and in vivo. Here we investigated the role of nitric oxide (NO) and tumour necrosis factor‐α (TNF‐α) as mediators in the tumoristatic effects of murine peritoneal macrophages activated with agonistic anti‐CD40 monoclonal antibody (αCD40) alone and following further stimulation with bacterial lipopolysaccharide (LPS). We found that macrophages activated in vivo by αCD40 exhibited tumoristatic activity in vitro against B16 melanoma cells; the tumoristatic effect correlated with the level of NO production and was enhanced by LPS. Use of the NO inhibitor l‐nitro‐arginine‐methyl esterase (L‐NAME) and evaluation of macrophages from inducible NO synthase (iNOS)‐knockout (KO) mice following αCD40 activation showed reduced tumoristatic activity. CD40 ligation enhanced expression of TNF‐α. Macrophage tumoristatic activity following αCD40 treatment was reduced by TNF‐α mAb or use of macrophages from TNF‐α‐KO mice. However, further stimulation of αCD40‐activated macrophages with LPS resulted in strong tumoristatic activity that was much less dependent on NO or TNF‐α. Taken together, these results suggest that NO and TNF‐α are involved in, but not solely responsible for, the antitumour effects of macrophages after activation by CD40 ligation.
Urban amphibian assemblages as metacommunities
Authors: PARRIS KIRSTEN M. 
Published: May 2006

Summary

Urban ecosystems are expanding throughout the world, and urban ecology is attracting increasing research interest. Some authors have questioned the value of existing ecological theories for understanding the processes and consequences of urbanization.
In order to assess the applicability of metacommunity theory to urban systems, I evaluated three assumptions that underlie the theory – the effect of patch area, the effect of patch isolation, and species–environment relations – using data on assemblages of pond‐breeding amphibians in the Greater Melbourne area of Australia. I also assessed the relative impact of habitat fragmentation, habitat isolation, and changes to habitat quality on these assemblages.
Poisson regression modelling provided support for an important increase in species richness with patch area (pond size) and a decrease in species richness with increasing patch isolation, as measured by surrounding road cover. Holding all other variables constant, species richness was predicted to be 2·8–5·5 times higher at the largest pond than at the smallest, while the most isolated pond was predicted to have 12–19% of the species richness of the least isolated pond. Thus, the data were consistent with the first two assumptions of metacommunity theory evaluated.
The quality of habitat at a pond was also important, with a predicted 44–56% decrease in the number of species detected at ponds with a surrounding vertical wall compared with those with a gently sloping bank. This demonstrates that environmental differences between habitat patches were also influencing amphibian assemblages, providing support for the species‐sorting and/or mass‐effect perspectives of metacommunity theory.
Without management intervention, urbanization may lead to a reduction in the number of amphibian species persisting in urban ponds, particularly where increasing isolation of ponds by roads and associated infrastructure reduces the probability of re‐colonization following local extinction.
Climate change may account for the decline in British ring ouzels Turdus torquatus
Authors: BEALE COLIN M. , BURFIELD IAN J. , SIM INNES M. W. , REBECCA GRAHAM W. , PEARCE‐HIGGINS JAMES W. , GRANT MURRAY C. 
Published: May 2006

Summary

Climate change is already affecting biodiversity, but the number of species for which reliable models relate weather and climate to demographic parameters is low.
We modelled the effect of temperature and rainfall on the breeding success and territory occupancy of ring ouzels Turdus torquatus (L.) in northern Britain, using data from a range of study areas, including one where there was a long‐term decline in ring ouzel abundance.
Timing of breeding was significantly related to meteorological variables affecting birds in the early spring, though there was no evidence that laying dates had advanced. Breeding success was not significantly related to weather variables; instead, over 90% of annual variation in this parameter could be explained by density dependence.
Annual change in territory occupancy was linked to rainfall and temperature the preceding summer, after the main breeding season and to rainfall in the wintering grounds 24 months previously, coincident with the period of juniper Juniperus sp. (L.) flowering. High temperature in late summer, intermediate levels of late summer rainfall, and high spring rainfall in Morocco 24 months previously all had negative impacts on territory occupancy the following year.
All three weather variables have changed over recent decades, with a significant increase in summer temperature, a significant decrease in summer rainfall, and a nonsignificant decline in Moroccan spring rainfall. A model based on these trends alone predicted an annual decline in occupancy of 3·6% (compared with an observed decline of 1·2%), and suggested that increased summer temperatures may underlie declines in the British ring ouzel population.
Changes in summer temperature after the main breeding period could affect the survival rates of adult and/or juvenile birds. An improved understanding of the post‐breeding ecology of ring ouzels is required to elucidate the mechanisms and causes of this relationship. Such knowledge might allow management aimed at buffering the impacts of climate change on ring ouzels.
Warm, windy winters drive cod north and homing of spawners keeps them there
Authors: RINDORF ANNA , LEWY PETER 
Published: May 2006

Summary

Climatic and anthropogenic effects often interact leading to unexpected results. For example, climate may lead to a change in the spatial distribution of a fish stock and thereby its vulnerability to exploitation. The North Sea cod stock is currently under pressure from both environmental change and human exploitation. This stock has experienced a series of poor recruitments since the late 1990s and, concomitant with the decrease in abundance, the distribution of cod has changed. While it has been suggested that the change in distribution can be linked to increasing temperatures and fishing pressure, there is little evidence for this hypothesis.
Using winter and summer survey catches, we investigated whether a directional shift in the distribution of cod has taken place over the years 1983–2003. We then examined whether the change could be linked to climatic conditions, fishing mortality, stock size or limited directional movement of cod. Using the derived models, we investigated whether fishing has increased the sensitivity of the cod population to climate‐induced distribution changes.
A series of winters characterized by high temperatures and southerly winds during the egg and larval phases of cod led to a northward shift in the distribution of juvenile North Sea cod the following year. A concomitant northern shift of mature fish around the time of spawning was linked directly to a tendency for northerly distributed juveniles to remain northerly throughout their life. This shift of the spawners further augmented that of the new recruits.
Although fishing mortality on a North Sea scale was not directly correlated with the displacement of any of the age groups, fishing has severely decreased the number of fish in older age groups. This increased the sensitivity of the distribution of the cod stock to climatic changes.
Synthesis and applications. The centre of gravity of North Sea cod has moved north as a result of the effect of a series of warm, windy winters on the distribution of recently settled cod. The shift was followed by a northwards shift in the distribution of older age groups. Unless a series of cold and calm years combined with a reduced mortality in the southern areas allows a southern spawning population to rebuild, the cod stock is unlikely to return to its previous area of distribution. Furthermore, protecting adult cod mainly in northern areas is unlikely to result in improved recruitment to the southern North Sea.
Making better biogeographical predictions of species’ distributions
Authors: GUISAN ANTOINE , LEHMANN ANTHONY , FERRIER SIMON , AUSTIN MIKE , OVERTON JACOB MC. C. , ASPINALL RICHARD , HASTIE TREVOR 
Published: May 2006

SummaryBiogeographical models of species’ distributions are essential tools for assessing impacts of changing environmental conditions on natural communities and ecosystems. Practitioners need more reliable predictions to integrate into conservation planning (e.g. reserve design and management).Most models still largely ignore or inappropriately take into account important features of species’ distributions, such as spatial autocorrelation, dispersal and migration, biotic and environmental interactions. Whether distributions of natural communities or ecosystems are better modelled by assembling individual species’ predictions in a bottom‐up approach or modelled as collective entities is another important issue. An international workshop was organized to address these issues.We discuss more specifically six issues in a methodological framework for generalized regression: (i) links with ecological theory; (ii) optimal use of existing data and artificially generated data; (iii) incorporating spatial context; (iv) integrating ecological and environmental interactions; (v) assessing prediction errors and uncertainties; and (vi) predicting distributions of communities or collective properties of biodiversity.Synthesis and applications. Better predictions of the effects of impacts on biological communities and ecosystems can emerge only from more robust species’ distribution models and better documentation of the uncertainty associated with these models. An improved understanding of causes of species’ distributions, especially at their range limits, as well as of ecological assembly rules and ecosystem functioning, is necessary if further progress is to be made. A better collaborative effort between theoretical and functional ecologists, ecological modellers and statisticians is required to reach these goals.
The impact of harvesting on a formerly endangered tropical bird: insights from life‐history theory
Authors: NICOLL MALCOLM A. C. , JONES CARL G. , NORRIS KEN 
Published: May 2006

Summary

Life‐history theory assumes that trade‐offs exist between an individual's life‐history components, such that an increased allocation of a resource to one fitness trait might be expected to result in a cost for a conflicting fitness trait. Recent evidence from experimental manipulations of wild individuals supports this assumption.
The management of many bird populations involves harvesting for both commercial and conservation purposes. One frequently harvested life‐history stage is the egg, but the consequences of repeated egg harvesting for the individual and the long‐term dynamics of the population remain poorly understood.
We used a well‐documented restored population of the Mauritius kestrel Falco punctatus as a model system to explore the consequences of egg harvesting (and associated management practices) for an individual within the context of life‐history theory.
Our analysis indicated that management practices enhanced both the size and number of clutches laid by managed females, and improved mid‐life male and female adult survival relative to unmanaged adult kestrels.
Although management resulted in an increased effort in egg production, it reduced parental effort during incubation and the rearing of offspring, which could account for these observed changes.
Synthesis and applications. This study demonstrates how a commonly applied harvesting strategy, when examined within the context of life‐history theory, can identify improvements in particular fitness traits that might alleviate some of the perceived negative impact of harvesting on the long‐term dynamics of a managed population.