bluuebunny/crossref_metadata_2025 huggingface dataset:
Occupational autoeczematization or atopic eczema precipitated by occupational contact dermatitis?
Authors: Williams Jason , Cahill Jennifer , Nixon Rosemary
Published: December 2006

Autoeczematization is characterized by the sudden dissemination of a previously localised form of eczema. While widely described, most cases reported have followed chronic, localized stasis dermatitis. In this study, we describe the clinical scenario of occupational contact dermatitis (OCD) triggering endogenous‐like eczema in atopic individuals, who often have not had eczema since childhood, if at all. These cases appear similar to previously described cases of autoeczematization. To show this clinical scenario, a series of 6 patients is presented from the Occupational Dermatology Clinic in Melbourne, Australia. These workers initially developed OCD, usually affecting the hands, which then precipitated a flare of more generalized eczema. This appeared clinically consistent with atopic eczema (AE), and often became recurrent, and sometimes persistent. OCD can precipitate a flare of more generalized eczema, in a pattern consistent with AE, which may then persist. The clinical scenario is similar to that described for autoeczematization. It is possible that the pathophysiology, when clarified, will prove to be similar. Workers’ compensation issues may become complicated for these patients, as the relationship between their generalized eczema and their occupational exposures may not be readily apparent. As a result, the work relatedness of their condition may not be recognized.
Information derived from sensitization test methods: test sensitivity, false positives and false negatives
Authors: Basketter David A. , Kimber Ian
Published: December 2006

Predictive toxicology tests for the prospective identification of skin‐sensitizing chemicals are well known and have been used for many years. However, of these, only the local lymph node assay (LLNA) has actually undergone formal independent assessment to determine the accuracy of the predictions, particularly with respect to the likelihood of false positives and false negatives. Often, efforts to increase the sensitivity of a test (reducing false negatives) tend to increase the number of false positives. In this short review, these issues are discussed in particular relation to the 3 predictive tests available in regulatory toxicology, the guinea‐pig maximization test, the occluded patch test of Buehler and the LLNA. A key perspective is that no predictive test is without limitations; having a good appreciation of these limitations is necessary for making the best use of the information derived from these methods.
Allergic contact dermatitis from modified colophonium in wound dressings
Authors: Pereira Teresa M. , Flour Maria , Goossens An
Published: December 2006

This study concerns a 69‐year‐old female patient with a longstanding history of venous ulcerations on both lower legs and multiple sensitivities, who developed eczematous lesions with the hydrocolloid dressing Combiderm® (Convatec Ltd., a Bristol‐Myers Squibb division, Ickenham, Middlesex, UK). Epicutaneous tests were positive to this dressing and to a modified colophonium derivative, i.e. glyceryl rosinate, however not to the unmodified colophonium from the standard series. A review of the literature showed several case reports about sensitization to similar hydrocolloids being distributed under various brand names in different countries and which contain the pentaerythritol ester of the hydrogenated rosin as the tackifying agent. Some of the patients described did, while others did not, react to colophonium but only to a modified derivative. In our patient, the reaction to glyceryl rosinate most probably represent cross‐sensitivity with the modified colophonium derivative used in Combiderm®, the presence (but not the exact nature) of which was showed by the company. In patients where allergic contact dermatitis from hydrocolloid dressings is strongly suspected and colophonium tests negatively, patch testing to modified colophonium derivatives should therefore be performed. As the complete composition of wound dressings is most often unknown, we urgently advocate legal requirements for labelling of those and in fact all medically used devices.
N1‐acetyl‐N2‐formyl‐5‐methoxykynuramine modulates the cell cycle of malaria parasites
Authors: Budu Alexandre , Peres Rafael , Bueno Vânia Blasques , Catalani Luiz Henrique , Garcia Célia Regina da Silva
Published: December 2006

Abstract:  We previously reported that intraerythrocytic malaria parasites have their development synchronized by melatonin and other products of tryptophan catabolism (i.e. serotonin, N‐acetylserotonin and tryptamine). Here, we show that N1‐acetyl‐N2‐formyl‐5‐methoxykynuramine (AFMK), a product of melatonin degradation, synchronizes Plasmodium chabaudi and Plasmodium falciparum. The synchronization is abrogated with a melatonin receptor antagonist, luzindole. We established quantitatively that a differential AFMK production occurred within the intraerythrocytic stages of rodent malaria parasite Plasmodium chabaudi (ring, trophozoite and schizont), when the infected erythrocytes were previously incubated with melatonin. Measurement of AFMK formation in P. chabaudi after incubation with melatonin at a concentration of 500 nmol/L revealed the following values for AFMK production: ring 0.1 ± 0.1 nmol/L, trophozoite 22.9 ± 0.5 nmol/L, schizont 29 ± 5 nmol/L. Confocal and spectrofluorophotometer experiments with isolated parasites and infected‐RBC, loaded with calcium indicator Fluo‐4 showed that AFMK elicits an increase in the cytosol calcium concentration in these parasites. Our data suggest that AFMK could have an important role in modulating the cell cycle of malaria parasites mainly in the late stages (trophozoite and schizont).
Skin radiance: how to quantify? Validation of an optical method
Authors: Petitjean Adeline , Sainthillier Jean‐Marie , Mac‐Mary Sophie , Muret Patrice , Closs Brigitte , Gharbi Tijani , Humbert Philippe
Published: December 2006

Background/purpose: The aim of this study was to validate an optic device used to measure the quantity of light reflected by the skin, which depends on the brightness of the skin.

Methods: This apparatus gives three parameters, called Complexion/diffusion (Cd), Cr (Complexion/reflection) and Complexion/specular position (Csp). Measurements were carried out on the forehead (slightly rounded surface) and the cheekbone (angular surface). To estimate the repeatability and the reproducibility of each parameter, two female subjects (one with a dull complexion and the other with a glowing complexion) and three operators participated in the study. To investigate repeatability, each operator performed 10 consecutive measurements on both zones. To investigate inter‐investigator reproducibility, the operators performed the measurements alternately. To investigate day‐to‐day reproducibility, these measures were achieved during three visits at a 2‐day interval, at D1, D3 and D5. To estimate the sensitivity and the specificity, 30 females participated in the study (15 in the dull complexion group and 15 in the glowing complexion group).

Results: Cd was repeatable (variation coefficient <20%), day‐to‐day reproducible on both sites (generally P>0.05) but not inter‐investigators reproducible (generally P<0.05). The sensitivity was 93% on the forehead and 80% on the cheekbone; the specificity was 87% on the forehead and 60% on the cheekbone. Cr was repeatable (variation coefficient <5%), day‐to‐day reproducible (P>0.05) and not inter‐investigators reproducible (generally P<0.05). The sensitivity was 93% on the forehead and 80% on the cheekbone; the specificity was 87% on the forehead and 80% on the cheekbone. Csp was not repeatable (variation coefficient >5%) on both the studied zones and for the three investigators.

Conclusion: The repeatability and the day‐to‐day reproducibility were satisfying for the Cd and Cr parameters on both the studied sites. The sensitivity and the specificity were satisfying for both parameters on both sites, except for the specificity of the Cd parameter on the cheekbone. Therefore, this apparatus is suitable to follow‐up an evolution on both the studied sites, but we recommend: (a) that the same trained investigator always performs the measurements, (b) to privilege the forehead in particular for a classification (dull or glowing).
Porcine ear skin: an in vitro model for human skin
Authors: Jacobi Ute , Kaiser Marco , Toll Rani , Mangelsdorf Susanne , Audring Heike , Otberg Nina , Sterry Wolfram , Lademann Juergen
Published: December 2006

Background/purpose: Porcine ear skin is used in studies of percutaneous penetration as a substitute for human skin. The structure of this tissue, including hair follicles, was studied qualitatively and quantitatively in comparison with human skin.

Methods: Sections of shock‐frozen biopsies, biopsies embedded in paraffin and cyanoacrylate skin surface biopsies were investigated using microscopy. The thickness of the different skin layers and the follicular characteristics were determined.

Results: The thickness of the stratum corneum was 17–28 μm, whereas the viable epidermis was 60–85 μm thick. On 1 cm2, 11–25 hairs were detected, showing a diameter of 58–97 μm and a maximal extension depth of 0.96–1.38 mm into the skin. The orifices of the porcine infundibula showed a diameter of approximately 200 μm.

Conclusions: The results obtained are similar to those of human skin, indicating the suitability of this porcine tissue as a model for human skin.
Oily skin: specific features in Chinese women
Authors: Nouveau‐Richard S. , Zhu W. , Li Y. H. , Zhang Y. Z. , Yang F. Z. , Yang Z. L. , Lian S. , Qian B. Y. , Ran Y. P. , Bouillon C. , Chen H. D. , De Lacharrière O.
Published: December 2006

Background/Purpose: Inconsistent data are available on the various types of skin, their prevalence and characterization, particularly regarding Asian skins. This observation prompted to conduct a large study in China to assess the prevalence of oily skin and identify the specific factors related to that type of skin.

Methods: The multicentre trial involved 1787 Chinese women in Shenyang, Harbin, Beijing, Chengdu and Suzhou, between 18 and 65 years of age. Data on history of acne, the presence of environmental factors and a detailed self‐evaluation of the skin were collected using a standardized questionnaire. A clinical evaluation of facial skin oiliness was carried‐out by a dermatologist at each centre. Sebum secretion was measured on the forehead using Sebumeter® SM810. Statistical analysis (multiple correspondence analysis) of typology was conducted based on self‐evaluation data.

Results: According to self‐evaluation data, oily skin prevalence in the overall Chinese population of the study was 25.6%. Self‐evaluation results were quite consistent with sebum measurements and with clinical assessment by dermatologist. Parameters associated with oily skin were (i) shiny skin and a past history of acne, (ii) irregular menstruation, and (iii) highly reactive or sensitive skin. Moreover, a clear and significant link was noted between oily skin and the ingestion of spicy or sweet food. Lastly, sebum levels were found to be twice as high in Beijing as in the other cities and were correlated to higher oily skin prevalence.

Conclusion: The study demonstrated the capacity of women for proper self‐evaluation of their skin type. It also suggests a potential link between nutritional factors such as spicy and/or sweet diets and oily skin as well as between sensitive and oily skin in this population.
Understanding “Good Days” and “Bad Days”: Emotional and Physical Reactivity Among Caregivers for Elder Relatives*
Authors: Koerner Susan Silverberg , Kenyon DenYelle Baete
Published: December 2006

Abstract:Using a daily diary design, we examined fluctuations in caregiver well‐being; how day‐to‐day variations in stressors related to the caregiving experience are linked to fluctuations in well‐being; and whether caregivers who are women, or high on certain personality traits (e.g., neuroticism) are more susceptible to emotional/physical health fluctuations in the face of daily stressors. Sixty‐three caregivers reported on eight consecutive days. Multilevel analyses (Hierarchical Linear Modeling) indicated significant within‐person reactivity. On days when caregivers faced more tasks than usual, more care recipient behavior problems, or more family disagreements regarding care, they experienced more depressive symptoms, feelings of burden, and physical symptoms. Some within‐person patterns of reactivity were moderated by gender and personality. Implications for community interventions for caregivers are discussed.
Family Caregivers’ Patterns of Positive and Negative Affect*
Authors: Robertson Suzanne M. , Zarit Steven H. , Duncan Larissa G. , Rovine Michael J. , Femia Elia E.
Published: December 2006

Abstract: Stressful and positive family caregiving experiences were examined as predictors of caregivers’ patterns of positive and negative affect in a sample of families providing care for a relative with dementia (N= 234). Four affect pattern groups were identified: (a) Well Adjusted (i.e., high positive affect, low negative affect); (b) Ambiguous (i.e., low on both positive and negative affect); (c) Intense (i.e., high on both positive and negative affect); and (d) Distressed (i.e., high negative affect, low positive affect). A multivariate model that included demographic characteristics and indicators of stressful and positive experiences of caregiving yielded 2 significant discriminant functions that served to classify caregivers correctly into their known affect groups. Implications for improving intervention efforts targeting family caregivers are discussed.
Mothering Through Recruitment: Kinscription of Nonresidential Fathers and Father Figures in Low‐Income Families*
Authors: Roy Kevin , Burton Linda
Published: December 2006

Abstract: We identify and discuss mothers’ early strategies to recruit nonresidential biological fathers, intimate partners, male family members and friends, and paternal kin to support the needs of young children in low‐income families. Using the concept of kinscription and longitudinal ethnographic data on 149 African American, Hispanic, and non‐Hispanic White families from Welfare, Children and Families: A Three‐City Study, we developed a model of recruitment that includes three related processes: the search for legitimacy with conventional fathers and partners, the consequences of maternal advocacy for intimate relationships, and protection of children and reduction of risks to family well‐being. Results indicate that mothers’ co‐opting of fathers and father figures to support their children is shaped by men’s immigration status, the tenuous nature of romantic relationships, and fathers’ intergenerational caregiving responsibilities. Implications for theories of coparenting and partner dynamics in low‐income families and for policy and programs are discussed.
A Qualitative Study of Homeless Fathers: Exploring Parenting and Gender Role Transitions*
Authors: Schindler Holly S. , Coley Rebekah L.
Published: December 2006

Abstract: The present qualitative research focuses on homeless fathers living with their children in family shelters. Data were collected through semistructured, face‐to‐face interviews with homeless fathers (n= 9) and shelter directors (n= 3). Findings suggest that how fathers made meaning of their experiences in a homeless shelter was related to contextual factors and constructions of masculinity. Contextual constraints deriving from unemployment, behavioral and psychological restrictions of shelters, and new parenting roles led men to reassess their parental and masculine role identities. Results further suggest that homeless shelters may provide a unique point for intervention services to assist poor fathers.
Support and Conflict in the Foster Family and Children’s Well‐Being: A Comparison Between Foster and Birth Children
Authors: Denuwelaere Mieke , Bracke Piet
Published: December 2006

Abstract: Data on 96 foster families with a foster child and a birth child between the ages of 10 and 21 years were used to analyze the association between support and conflict processes within the foster family and youths’ reports on four indexes of well‐being: self‐esteem, self‐efficacy, emotional problems, and behavioral problems. The self‐esteem of foster children was more strongly affected by support and conflict processes in the foster family than was the self‐esteem of birth children in the same family. For birth children as well as for foster children, parental support significantly related to emotional problems. For foster children, but not for birth children, more conflicts with the foster parents related to more behavioral problems. The results are compared with other studies, and implications for practice are suggested.
The Predictors of Parental Use of Corporal Punishment
Authors: Grogan‐Kaylor Andrew , Otis Melanie D.
Published: December 2006

Abstract:Corporal punishment has been the focus of considerable study over the past decade. Some recent research suggesting that the use of corporal punishment may have significant long‐term negative effects on children has prompted increasing exploration and interest in the issue. We used tobit regression analysis and data from the 2000 National Longitudinal Survey of Youth to examine both the prevalence and the chronicity of spanking in a nationally representative sample of parents. Mother’s characteristics (e.g., age, education) and neighborhood context did not show a relationship with parental use of corporal punishment. Among parents who used corporal punishment, being Protestant had a relatively large relationship with its use. Although children’s externalizing behaviors had some association with parent’s propensity to spank, findings suggest that use of corporal punishment may be better understood as part of a constellation of behaviors relating to a parenting style. Further, findings indicate that it is easier to predict the incidence of corporal punishment than to predict its frequency of use.
Identification and characterization of a nuclear receptor subfamily I member in the Platyhelminth Schistosoma mansoni (SmNR1)
Authors: Wu Wenjie , Niles Edward G , Hirai Hirohisa , LoVerde Philip T
Published: December 2006

A cDNA encoding a nuclear receptor subfamily I member in the platyhelminth Schistosoma mansoni (SmNR1) was identified and characterized. SmNR1 cDNA is 2406 bp long and contains an open reading frame encoding a 715 residue protein. Phylogenetic analysis demonstrates that SmNR1 is a divergent member of nuclear receptor subfamily I with no known orthologue. SmNR1 was localized to S. mansoni chromosome 1 by fluorescent in situ hybridization. Gene structure of SmNR1 was determined showing it to consist of eight exons spanning more than 14 kb. Quantitative real‐time RT‐PCR showed that SmNR1 was expressed throughout schistosome development with a higher expression in eggs, sporocysts and 21‐day worms. SmNR1 contains an autonomous transactivation function (AF1) in the A/B domain as demonstrated in a yeast one‐hybrid assay; it interacts with SmRXR1 in a yeast two‐hybrid assay and in a glutathione S‐transferase pull‐down assay. Electrophoretic mobility shift assay showed that SmNR1 could form a heterodimer with SmRXR1 to bind to DNA elements containing the half‐site AGGTCA, a direct repeat of the half‐site separated by 0–5 nucleotides (DR1‐DR5) and a palindrome repeat of the half‐site not separated by nucleic acids (Pal0). Transient transfection in mammalian COS‐7 cells showed that SmNR1/SmRXR1 could enhance the transcriptional activation of a DR2‐dependent reporter gene. Our results demonstrate that SmNR1 is a partner of SmRXR1.
Responses of shoot growth and survival to water stress gradient in diploid and tetraploid populations of Lolium multiflorum and L. perenne
Authors: Sugiyama Shu‐ichi
Published: December 2006

Drought stress is one of the critical environmental factors in determining growth and survival of herbage grasses. In this study, by using a hydroponic culture system including different amounts of polyethylene glycol (PEG), responses of plant shoots to water stress in four different intensities (0 Mpa, −0.6 Mpa, −1.2 Mpa and −1.8 Mpa) were examined in diploid and tetraploid cultivars of Italian ryegrass (Lolium multiflorum) and perennial ryegrass (L. perenne). Since freezing injury is caused by cell dehydration, freezing tolerance was also examined for six subzero temperatures (−11, −12, −14, −16, −18 and −20°C) in both species. L. multiflorum had a larger shoot biomass at all stress intensities and a lower survival rate under severe water stress and freezing stress conditions than L. perenne. Thus, there was a trade‐off (negative correlation) between potential growth under a stress‐free condition and survival under a severe stress condition in diploid and tetraploid cultivars of both species. This trade‐off was mediated by tissue water content. High water content led to a high growth rate through increasing specific leaf area, while low water content resulted in a high tissue osmotic potential that could confer high cell dehydration tolerance.
Effects of grass height at the start of grazing on herbage intake and milk production under rotational grazing by lactating dairy cows
Authors: Nakatsuji H. , Nishimichi Y. , Yayota M. , Takahashi M. , Ueda K. , Kondo S. , Okubo M.
Published: December 2006

Under rotational grazing by lactating dairy cows, effects of grass height at the start of a grazing season on herbage intake and milk production were evaluated. A 1.87 ha grass‐clover mixed sward was divided evenly into two paddocks, and a different group of six lactating Holstein cows were rotationally grazed on each paddock for 5 h a day. Grazing was commenced when mean grass height in the two paddocks reached 15 cm (S15) and 20 cm (S20), respectively. Mean grass height throughout the grazing period tended to be higher in S20 than S15, and in particular, the difference at June between the treatments was significant (P < 0.01). However, mean crude protein and neutral detergent fiber contents of herbage, including those at June, did not significantly differ between S15 and S20. Mean daily herbage dry matter (DM) and total digestible nutrients (TDN) intake per cow were similar between S15 and S20, while mean daily total feed DM and TDN intake tended to be higher in S15 than S20, although the difference was not significant. Mean daily total 4% fat‐corrected milk (FCM) yield tended to be higher in S15 than S20, but there was no difference in mean daily FCM yield derived from herbage between the treatments. The amount of herbage DM and TDN intake per unit area throughout the grazing period was similar between the treatments, and were 8.56 and 5.61 t/ha in S15 and 8.62 and 5.54 t/ha in S20. The amount of FCM yield from pasture differed very little between the treatments, and was 11.10 and 10.81 t/ha in S15 and S20, respectively. The difference in the grass height at the start of grazing as in the present study had no obvious effect on nutritive values of herbage, herbage intake per animal, and herbage intake and milk production per unit area.
Multitracer Test Approach to Characterize Reactive Transport in Karst Aquifers
Authors: Geyer Tobias , Birk Steffen , Licha Tobias , Liedl Rudolf , Sauter Martin
Published: December 2006

A method to estimate reactive transport parameters as well as geometric conduit parameters from a multitracer test in a karst aquifer is provided. For this purpose, a calibration strategy was developed applying the two‐region nonequilibrium model CXTFIT. The ambiguity of the model calibration was reduced by first calibrating the model with respect to conservative tracer breakthrough and later transferring conservative transport parameters to the reactive model calibration. The reactive transport parameters were only allowed to be within a defined sensible range to get reasonable calibration values. This calibration strategy was applied to breakthrough curves obtained from a large‐scale multitracer test, which was performed in a karst aquifer of the Swabian Alb, Germany. The multitracer test was conducted by the simultaneous injection of uranine, sulforhodamine G, and tinopal CBS‐X. The model succeeds to represent the tracer breakthrough curves (TBCs) of uranine and sulforhodamine G and verifies that tracer‐rock interactions preferably occur in the immobile fluid region, although the fraction of this region amounts to only 3.5% of the total water. However, the model failed to account for the long tailing observed in the TBC of tinopal CBS‐X. Sensitivity analyses reveal that model results for the conservative tracer transport are most sensitive to average velocity and volume fraction of the mobile fluid region, while dispersion and mass transfer coefficients are least influential. Consequently, reactive tracer calibration allows the determination of sorption sites in the mobile and immobile fluid region at small retardation coefficients.
Successful wastewater reuse scheme and sustainable development: a case study in Adelaide
Authors: Keremane Ganesh B. , McKay Jennifer
Published: December 2006

Freshwater availability to meet the growing needs of humankind has raised serious concerns in the recent past. Two immediate responses to counter this challenge are efficient allocation of the scarce resources, and development and use of alternative sources of water. While ‘water markets’ are seen as a means to achieve efficient allocation of the scare resources, treated wastewater and low‐quality water are now considered as potential sources of water to supplement the freshwater supplies. However, the latter option, that is use of reclaimed water as an alternative, imposes concerns regarding its suitability to sustain development. This is because of various issues related to wastewater usage and application. At the same time, it is also true that a successful and well‐planned reuse scheme can help achieve sustainability as evidenced in some isolated cases around the world. In line with this, the current paper adopts a case‐study approach to demonstrate how a successful reuse scheme in Adelaide, South Australia, has contributed to the sustainable development of the region. The paper looks into the socio‐economic and environmental dimensions of sustainability and arrives at a conclusion that properly planned and managed reuse schemes backed with effective regulatory and policy measures can lead to sustainable development.
Temporal variation and the evolution of a parasitoid foraging cue
Authors: Brassil Chad E.
Published: December 2006

This work details theory in which selection favors generalists in a more variable environment. Specifically, in a two‐host‐one‐parasitoid model, temporal variation in host abundances alters the optimal searching strategy and leads to the evolution of more generalist parasitoid strategies. Consistent with empirical observations, parasitoids learn host/plant odors, and use them as a cue to search for oviposition sites. The amount of unsuccessful search time required before a parasitoid alters its searching cues (the “giving‐up time”) is modeled in order to understand the evolutionarily optimal giving‐up times under a variety of conditions. When host abundances vary across time, a generalist parasitoid strategy evolves with short giving‐up times as it is likely that the host initially favored by a parasitoid will now have a low abundance. In contrast, when populations reach stable dynamics across time, giving‐up times typically evolve to longer times, i.e. parasitoids remain specialized longer. The effect of temporal fluctuations is consistent across variation caused by endogenous population interactions and, to some degree, by environmental stochasticity. The conclusions are robust in that there is a strong degree of concordance between the results of a stochastic, individual‐based model and a deterministic, numerical model. As an extension, spatial variation in hosts that leads to unequal tradeoffs between generalist parasitoids and specialist parasitoids may also result in the evolution of reduced giving‐up times.
Predator selectivity alters the effect of dispersal on coexistence among apparent competitors
Authors: Östman Örjan , M. Chase Jonathan
Published: December 2006

While the majority of studies on dispersal effects on patterns of coexistence among species in a metacommunity have focused on resource competitors, dispersal in systems with predator–prey interactions may provide very different results. Here, we use an analytical model to study the effect of dispersal rates on coexistence of two prey species sharing a predator (apparent competition), when the traits of that predator vary. Specifically, we explore the range in immigration rates where apparent competitors are able to coexist, and how that range changes with predator selectivity and efficiency. We find that if the inferior apparent competitor has a higher probability of being consumed, it will require less immigration to invade and to exclude the superior prey as the predator becomes more opportunistic. However, if the inferior apparent competitor has a lower probability of being consumed (and lower growth rates), higher immigration is required for the inferior prey to invade and exclude the superior prey as the predator becomes more opportunistic. We further find that the largest range of immigration rates where prey coexist occurs when predator selectivity is intermediate (i.e. they do not show much bias towards consuming one species or the other). Increasing predator efficiency generally reduces the immigration rates necessary for the inferior apparent competitor to invade and exclude the superior apparent competitor, but also reduces the range of immigration rates where the two apparent competitors can coexist. However, when the superior apparent competitor has a higher probability of being consumed, increased predator efficiency can increase the range of parameters where the species can coexist. Our results are consistent with some of the variation observed in the effect of dispersal on prey species richness in empirical systems with top predators.
Importance of spatial autocorrelation in modeling bird distributions at a continental scale
Authors: Bahn Volker , J. O'Connor Raymond , B. Krohn William
Published: December 2006

Spatial autocorrelation in species’ distributions has been recognized as inflating the probability of a type I error in hypotheses tests, causing biases in variable selection, and violating the assumption of independence of error terms in models such as correlation or regression. However, it remains unclear whether these problems occur at all spatial resolutions and extents, and under which conditions spatially explicit modeling techniques are superior. Our goal was to determine whether spatial models were superior at large extents and across many different species. In addition, we investigated the importance of purely spatial effects in distribution patterns relative to the variation that could be explained through environmental conditions. We studied distribution patterns of 108 bird species in the conterminous United States using ten years of data from the Breeding Bird Survey. We compared the performance of spatially explicit regression models with non‐spatial regression models using Akaike's information criterion. In addition, we partitioned the variance in species distributions into an environmental, a pure spatial and a shared component. The spatially‐explicit conditional autoregressive regression models strongly outperformed the ordinary least squares regression models. In addition, partialling out the spatial component underlying the species’ distributions showed that an average of 17% of the explained variation could be attributed to purely spatial effects independent of the spatial autocorrelation induced by the underlying environmental variables. We concluded that location in the range and neighborhood play an important role in the distribution of species. Spatially explicit models are expected to yield better predictions especially for mobile species such as birds, even in coarse‐grained models with a large extent.
Variations in species and functional plant diversity along climatic and grazing gradients
Authors: De Bello Francesco , Lepš Jan , Sebastià Maria‐Teresa
Published: December 2006

Different components of biodiversity may vary independently of each other along environmental gradients giving insights into the mechanisms that regulate species coexistence. In particular, the functional diversity (FD) or the presence of rare or endemic species in natural assemblages do not necessarily increase with species diversity. We studied if different components of plant species diversity (species richness, Simpson diversity, evenness) varied similarly to FD (measured as a generalization of the Simpson index) and rarity along grazing intensity and climatic gradients. Plots under different sheep grazing regimes (high and low intensity, abandonment) were surveyed in five locations along a climatic gradient in north‐eastern Spain, from semi‐arid lowland to moist upland locations. Variation in species diversity, functional diversity and rarity followed different patterns. Species diversity was lowest in water‐stressed environments (arid locations and southern aspects) and increased with grazing more makedly in humid locations. The FD was comparable between the most species‐poor and species‐rich locations and decreased with grazing in the moistest location, i.e. where species diversity markedly increased. The FD did not show a strong correlation with species richness nor with the Simpson index and less specious communities could show the highest functional diversity. The rarest species in the region were more frequently found in the abandoned areas, which held the lowest species diversity. Consequently, the mechanisms that enhance the diversity of species do not necessarily support a functional differentiation among those species or the maintenance of rare species in a region. We hypothesize that the degree of dependence of functional diversity on species diversity might be mostly related to the amplitude of the species’ traits pool and on how species partition the niche space available.
Bottom‐up and top‐down processes in African ungulate communities: resources and predation acting on the relative abundance of zebra and grazing bovids
Authors: Grange Sophie , Duncan Patrick
Published: December 2006

African ungulate populations appear to be limited principally by their food resources. Within ungulate communities, plains zebras coexist with grazing bovids of similar body size, but rarely are the dominant species. Given the highly effective nutritional strategy of the equids and the resistance of zebras to drought, this is unexpected and suggests that zebra populations may commonly be limited by other mechanisms. Long‐term research in the Serengeti ecosystem and in the Kruger National Park suggests that zebra could be less sensitive to food shortage, and more sensitive to predation, than grazing bovids: if this is a general principle, then, at a larger scale, resource availability should have a weaker effect on the abundance of zebra than on grazing ruminants of similar body size (wildebeest and buffalo), and zebras should be relatively more abundant in ecosystems where predators are rare or absent. We test these expectations using data on 23 near‐natural ecosystems in east and southern Africa. The abundance of wildebeest is more closely related to resources than is that of zebra; buffalo are intermediate. We show that hyena densities are closely correlated with those of lions, and use the abundance of lions as an index of predation by large predators. The numerical response of lions to increases in the abundance of their prey was linear for mesoherbivores, and apparently so for the three species alone. Finally, the abundance of zebra relative to grazing bovids is lower in ecosystems with high biomasses of lions. These results indicate that zebras may commonly be more sensitive to top‐down processes than grazing bovids: the mechanism(s) have not been demonstrated, but predation could play a role. If it is true, then when numbers of the large mammalian predators decline, zebra populations should increase faster than buffalo and wildebeest.
Contrasting spatial and temporal global change impacts on butterfly species richness during the 20th century
Authors: White Peter , Kerr Jeremy T.
Published: December 2006

Regional patterns of species richness are often explained by models using temperature or measures habitat suitability. Generally, species richness is positively associated with temperature, and negatively associated with habitat degradation. While these models have been well tested across spatial scales, they have rarely been tested on a temporal scale – in part due to the difficulty in ascertaining accurate historical data at an appropriate resolution. In this study, we compared the results of temporal and spatial models, each incorporating two predictors of species richness: temperature, and human population density (as a surrogate of human‐related habitat impacts). We found that the change in species richness from the early to late part of the 20th century was positively correlated with temperature change, and negatively correlated with human population density change. When we compared these results to two spatial models using contemporary and historic data, the spatial effects of temperature on butterfly richness were similar to its temporal effects, while the effect of human population density through time is the opposite of its spatial effect. More generally, the assumption that spatial patterns are equivalent to temporal ones when applying macroecological data to global change is clearly unreliable.
Effect of community assembly and primary succession on the species‐area relationship in disturbed ecosystems
Authors: Carey Susan , Harte John , Del Moral Roger
Published: December 2006

The species‐area relationship (SAR) provides a cornerstone for ecological theory. Implicit in SAR studies is the assumption that SAR properties, especially SAR slopes, remain constant through time, even though the ecosystem characteristics that they encompass–the spatial distribution and abundance of species–change on seasonal to evolutionary time scales. Focusing on disturbed subalpine systems, we evaluated whether SAR properties are a function of stage of succession at Mount St. Helens, WA, and at Gothic, CO. We found that the SAR flattens and shifts upward as these systems mature. The decrease in SAR curvature at Mount St. Helens suggests a transition toward power‐law SAR behavior with assembly. Overall, the observed changes in SAR properties raise questions about the appropriateness of applying contemporary SARs to predict future levels of species richness in disturbed or successional systems.
Dispersal and recruitment during population growth in a colonial bird, the great cormorantPhalacrocorax carbo sinensis
Authors: Hénaux Viviane , Bregnballe Thomas , Lebreton Jean‐Dominique
Published: December 2006

While the factors influencing reproduction and survival in colonial populations are relatively well studied, factors involved in dispersal and settlement decisions are not well understood. The present study investigated exchanges of great cormorantsPhalacrocorax carbo sinensisamong six breeding colonies over a 13‐year period when the breeding population in Denmark increased from 2800 to 36 400 nests. We used a multistate capture‐recapture model that combined multisite resightings and recoveries to examine simultaneously recruitment, natal dispersal, breeding dispersal and annual survival of first‐year, immature and breeding great cormorants. Mean survival of first‐year birds (0.50±0.09, range=0.42–0.66 among colonies) was lower than survival of breeders (0.90±0.06, range=0.81–0.97). Mean survival of immature birds over the study period was 0.87±0.08. Dispersal from a colony increased with decreasing mean brood size in the colony in both first‐time and experienced breeders. The choice of the settlement colony in first‐time breeders was affected by conditions in the natal colony and in the colonies prospected during the pre‐breeding years. In particular, first‐time breeders recruited to colonies where they could expect better breeding success. Experienced breeders relied mainly on cues present early in the season and on their own breeding experience to choose a new breeding colony. Newly established colonies resulted mainly from the immigration of first‐time breeders originating from denser colonies. Dispersal was distance‐dependent and first‐time breeders dispersed longer distances than breeders. We suggest that the prospecting behaviour allows first‐time breeders to recruit in nearby as well as more distant potential breeding colonies. Dispersing breeders preferred to settle in neighbouring colonies likely to benefit from their experience with foraging areas. We discuss the importance of these movements for growth and expansion of the breeding population.
Intraspecific genetic analysis of the summer tanagerPiranga rubra: implications for species limits and conservation
Authors: M. Shepherd Tiffany , J. Burns Kevin
Published: December 2006

The summer tanagerPiranga rubrais a Neotropical migrant that has experienced noted declines in the southwestern United States caused by extensive habitat loss of native riparian woodlands. This species is composed of two morphologically and behaviorally distinct taxa that traditionally have been recognized as subspecies, each occupying unique habitats in the southern part of North America. Genetic analyses of intraspecific variation are important in studies of threatened or endangered species because they can indicate whether smaller management units exist below the species level and they also provide estimates of within population variability. Using a mitochondrial DNA marker, the intraspecific genetic variation of this species is explored to determine whether the morphologically and behaviorally distinct subspecies are also genetically unique. By using traditional phylogenetic methods and building haplotype networks, results from this study indicate that the subspecies represent two phylogenetic species and should be managed as separate units. In addition, the level of gene flow among geographically isolated populations of the western subspecies is explored using Nested Clade Phylogeographic Analysis and population genetic tests. These analyses show that populations are genetically diverse and that haplotypes are shared across populations. Newly colonized populations are as diverse as older populations. This suggests that as habitat degrades in traditional breeding areas of the summer tanager, if suitable habitat elsewhere becomes available for new populations, these new colonies should be genetically diverse.
Does having multiple partners weaken the benefits of facultative mutualism? A test with cacti and cactus‐tending ants
Authors: Miller Tom E. X.
Published: December 2006

Interspecific facultative mutualisms typically involve guilds of interacting species, and species within a guild can vary in the quality of services they provide. For plants that secrete extrafloral nectar (EFN), visitation by multiple ant species that vary in anti–herbivore abilities may result in reduced benefits, relative to an exclusive association with a high‐quality mutualist. This raises the intriguing problem of how facultative ant‐plant mutualisms persist, given that EFN is costly to produce, yet may confer diminishing returns as partner diversity increases. I tested the prediction that association with two ant partners (Crematogaster opuntiae and Liometopum apiculatum) weakens benefits to the EFN‐producing tree cholla cactus (Opuntia imbricata). I found that only one ant (L. apiculatum) provided protection against herbivores and seed predators. However, this species associated with cacti more frequently than Crematogaster across multiple temporal scales. Within years, Liometopum showed greater constancy on plants they occupied, more frequently colonized vacant plants, and replaced but were never replaced by Crematogaster. Across years of plant development, Liometopum was more abundant on reproductive plants and showed greater overlap with cactus enemies. Simulations of cactus lifetime reproductive output indicated that associating with high‐ and low‐quality mutualists did not significantly reduce plant benefits relative to an exclusive L. apiculatum–O. imbricata association. The results suggest that non‐random interaction frequencies, possibly driven by competition, may contribute to the maintenance of facultative mutualisms involving multiple, qualitatively different partners.
Dark‐bellied brent geese Branta b. bernicla breeding near snowy owl Nyctea scandiaca nests lay more and larger eggs
Authors: H. van Kleef Henricus , Willems Frank , E. Volkov Andrei , J. H. R. Smeets Joseph , Nowak Damian , Nowak Agnieszka
Published: December 2006

Several studies have demonstrated that snowy owls Nyctea scandiaca defend an area around their nests against predators, hereby inadvertently creating safe havens for breeding dark‐bellied brent geese Branta b. bernicla. However, studies investigating brent goose breeding ecology within the predator‐exclusion zones of the snowy owls are absent. In 1999 and 2005, years of high lemming abundance Lemmus sibiricus and Dicrostonyx torquatus, brent geese were primarily breeding in association with snowy owls in the Medusa river catchment on western Taimyr, Russia. Goose nest failure, either as a result of nest abandonment by the adult birds or of nest depredation, increased with increasing distance from the owl nests. Within the brent goose colonies, clutch size as well as egg size increased with decreasing distance from the snowy owl nest, indicating an increasing adult quality closer to owl nests. However, as a result of the abandonment of eggs and goslings, the increasing clutch size did not result in a higher nest success during this study. Apparently brent geese compete for breeding sites close to owl nests, but details of this process remain unknown.
Quantum Spin Hall Effect and Topological Phase Transition in HgTe Quantum Wells
Authors: Bernevig B. Andrei , Hughes Taylor L. , Zhang Shou-Cheng
Published: December 2006

We show that the quantum spin Hall (QSH) effect, a state of matter with topological properties distinct from those of conventional insulators, can be realized in mercury telluride–cadmium telluride semiconductor quantum wells. When the thickness of the quantum well is varied, the electronic state changes from a normal to an “inverted” type at a critical thickness
d
c
. We show that this transition is a topological quantum phase transition between a conventional insulating phase and a phase exhibiting the QSH effect with a single pair of helical edge states. We also discuss methods for experimental detection of the QSH effect.