bluuebunny/crossref_metadata_2025 huggingface dataset:
Spatial Variation in Abundance
Authors: Brown James H. , Mehlman David W. , Stevens George C.
Published: May 2006

To quantify the magnitude and pattern of spatial variation in local population density within a single species, we analyzed large numbers of samples, representing a large geographic area or a wide range of ecological conditions. Our analyses focused on, but were not limited to, censuses of birds recorded in the North American Breeding Bird Survey. Birds and other organisms exhibited a common pattern: each species was represented by only a few individuals in most of the sample sites where it occurred, but was orders of magnitude more abundant in a few "hot spots." The highly clumped frequency distributions of intraspecific abundance among sample sites resemble distributions, such as the negative binomial, canonical lognormal, and broken stick, that have been used to characterize the distribution of abundances among species within local ecological communities. We hypothesize that the spatial variation in abundance largely reflects the extent to which local sites satisfy the niche requirements of a species. Several results are consistent with this hypothesis. First, a computer simulation model in which abundance is determined by the multiplicative combination of several independent environmental variables produces ranked distributions of abundances similar to those observed empirically. Second, geographic patterns of abundance of bird species have been relatively stable over several decades, indicating that different abundances are associated with particular places on the landscape. Third, the abundance of bird species varies in a systematic way over the geographic range, exhibiting positive spatial autocorrelation at small distances and a tendency to increase from the edges toward the center of the range. The magnitude and pattern of spatial variation in local population density has important implications for basic ecology and biogeography, especially for the dynamics and regulation of abundance on both space and time, the limits and internal structure of the geographic range, and the interspecific variation in abundance observed within local communities. Patterns of spatial and temporal variation in abundance should be considered in the design of nature reserves and the conservation of biological diversity.
Initiation of Metamorphosis in the Pitcher‐Plant Mosquito: Effects of Larval Growth History
Authors: Bradshaw William E. , Johnson Kevin
Published: May 2006

Variable growth and development were imposed on the pitcher—plant mosquito. Wyeomyia smithii, to test whether the initiation of metamorphosis was determined early in larval life or remained flexible throughout development. Like anurans, larval W. smithii are specialized for a suspension—feeding way of life and they metamorphose into dispersing, reproductive adults. We therefore used models originally formulated in an amphibian context to examine the effects of modified larval growth on the triggering of metamorphosis and then used our results to reexamine metamorphosis in amphibians. Response to enhanced and decreased food regimens showed that larval growth during the first two (of four) instars affected both the time to and mass at metamorphosis. The major effects of developmental inertia are prominent for about one to two instars and then abate, but do not necessarily disappear, with each succeeding instar. Despite evidence for developmental inertia in W. smithii, experiments transferring larvae from high food to starvation show that the physiological commitment to undergo metamorphosis does not take place until the last (fourth) instar and that nonzero growth during the last instar is required to trigger metamorphosis. All amphibian models for the initiation of metamorphosis involve the effects of rates: developmental rate and past or present growth rates. In W. smithii, there is no primacy of developmental rate and low growth rate does not stimulate metamorphosis of larvae having attained the minimum mass required for metamorphosis. An insect—derived model involving the effects of size—specific growth increments is more consistent than any amphibian model with our results in W. smithii. Testing the reciprocal ability of the insect model to predict amphibian metamorphosis is not possible with current data, because no study has considered zero growth in amphibians to identify the transition from growth—dependent to growth—independent development leading to metamorphosis. This transition marks the irrevocable commitment of the organism to an ontogenetic niche shift from an aquatic larva to a terrestrial, dispersing, and reproducing adult. Identifying the proximal causes of this mechanism is fundamental to understanding how flexible growth and ontogeny of complex life cycles have adapted to variable larval environments.
Body Condition and Seabird Reproductive Performance: A Study of Three Petrel Species
Authors: Chastel Olivier , Weimerskirch Henri , Jouventin Pierre
Published: May 2006

We investigated relationships between body condition (body mass scaled by body size) early in the breeding season and reproductive performance of three seabird species showing various life history traits. The study was conducted at Kerguelen Island from 1987 to 1994 on the Blue Petrel (Halobaena caerulea, an oceanic feeder), the Thinbilled Prion (Pachyptila belcheri, a neritic feeder), and the Common Diving Petrel (Pelacanoides urinatrix, a coastal feeder). Breeding success was highly variable among years in the three species, but the proportion of nonbreeding experienced breeders varied significantly only in the Blue Petrel. In the three species, body condition showed considerable year—to—year variation, suggesting substantial fluctuation in the availability of prey early in the breeding season. Relationships between early body condition and reproductive performance differed among the species. Reproductive success was significantly influenced by early condition in the Blue Petrel but not in the Thin—billed Prion and the Common Diving Petrel. In the long—lived Blue Petrel, depletion of body condition early in the breeding season resulted in a high proportion of nonbreeders and massive egg desertion. On the other hand, the shorter lived Thin—billed Prion and Common Diving Petrel seemed to respond by maintaining their reproductive output during poor years, probably investing more in the reproductive episode. Such contrasted patterns are analyzed in the light of reproductive effort and optimal clutch size theory.
Effect of Trace Elements on Population Dynamics: Selenium Deficiency in Free‐Ranging Black‐Tailed Deer
Authors: Flueck Werner T.
Published: May 2006

The effect of the trace element selenium on black—tailed deer (Odocoileus hemionus columbianus) was studied in northern California. The role of selenium was evaluated by supplementing free—ranging adult females with selenium, measuring fawn production before weaning, and comparing to unsupplemented controls. Whole blood selenium levels (mode = 24 mg/kg) of unsupplemented animals were low, and 95% of free—ranging deer had inadequate levels according to livestock standards. There were no differences in whole blood selenium levels among sexes, ages, or seasons. However, there were significant differences between spring blood samples over the years. Selenium supplements increased preweaning fawn survival from 0.32 fawns/female to 0.83 fawns/female. The assumption that free—ranging wild ruminants are not normally susceptible to trace mineral deficiencies because adaptations to deficiencies occur over geological time was not supported.
Primary Production of the Central Grassland Region of the United States
Authors: Sala O. E. , Parton W. J. , Joyce L. A. , Lauenroth W. K.
Published: May 2006

Aboveground net primary production of grasslands is strongly influenced by the amount and distribution of annual precipitation. Analysis of data collected at 9500 sites throughout the central United States confirmed the overwhelming importance of water availability as a control of production. The regional spatial pattern of production reflected the east—west gradient in annual precipitation. Lowest values of aboveground net primary production were observed in the west and highest values in the east. This spatial pattern was shifted eastward during unfavorable years and westward during favorable years. Variability in production among years was maximum in northern New Mexico and southwestern Kansas and decreased towards the north and south. The regional pattern of production was largely accounted for by annual precipitation. Production at the site level was explained by annual precipitation, soil water—holding capacity, and an interaction term. Our results support the inverse texture hypothesis. When precipitation is <370 mm/yr, sandy soils with low water—holding capacity are more productive than loamy soils with high water—holding capacity, while the opposite pattern occurs when precipitation is >370 mm/yr.
A Holocene Sedimentary Record from Anangucocha in the Ecuadorian Amazon
Authors: Frost Ian
Published: May 2006

The stratigraphic, seddimentary pigment, loss—on—ignition, pollen, and radiocarbon data of a sedimentary record from Anangucocha, in the Ecuadorian Amazon, define three environmental episodes during the last 3100 yr. A swamp episode (<3100—1300 BP) was followed by regional flooding (1300—800 BP) and an open lake period (since 800 BP). Pollen data show that a Mauritia palm forest occupied the early blackwater swamp and was replaced by a riparian community dominated by Cecropia during the flooding episode. The pollen of Urticaceae—Moraceae taxa, especially Urtica, has increased in abundance since the flood. Past flooding was an important disturbance agent, which influenced the history of the plant community around Anangucocha. In the Amazon forest, such episodic flooding may be an important type of disturbance that promotes and maintains high species diversity. The Anangucocha record indicates that Amazonia experienced climatic fluctuation during the late Holocene.
Do Interactions of Cellular Slime Mold Species Regulate their Densities in Soil?
Authors: Ketcham Robert B. , Levitan Don R. , Shenk M. Andrew , Eisenberg Robert M.
Published: May 2006

Studies of the ecology of macroorganisms have produced a body of theory about the nature of biological interactions and their effects on species in the field. This body of theory describes the ways that species affect each other and also predicts the outcome of specific interactions such as competition or predation. It is reasonable to ask whether the same body of theory applies to species of microorganisms. We performed a simple field experiment to test the hypothesis that biological interactions influence species of cellular slime molds living in forest soils. Members of the guild of cellular slime mold species co—occur on both microhabitat and geographic scales and in laboratory cultures, the species all consume the same food resources. We experimentally elevated the density of one cellular slime mold species and detected significant population responses in the remaining species in the cellular slime molds: (1) we observed resource limitation in the species that we added, and (2) we observed that the densities of cellular slime mold species are interrelated.
Interactions among Vetches Bearing Extrafloral Nectaries, their Biotic Protective Agents, and Herbivores
Authors: Koptur Suzanne , Lawton John H.
Published: May 2006

The stipular nectaries of the common vetch (Vicia sativa L.) are present on young plants from about the seventh node and continue to secrete nectar through flowering, until fruit are mature. The ant Myrmica ruginodis is the primary visitor to these nectaries in North Yorkshire, England. The ants are effective at removing or disturbing some of the externally feeding insect herbivores (mostly Lepidoptera, and some Coleoptera), but leaves nevertheless sustain some damage from hard—bodied beetles. More devasting are the pod—feeding larvae of Cydia spp., tortricid moths that oviposit on ovaries of flowers and whose larvae feed in the developing legumes, safe from ants. In areas where ant abundance is highest, the pod—feeding larvae are apparently well protected by ants from their natural enemies, ichneumonid parasitoid wasps (Scambus planatus and Campoplex punctulatus). Plants in such areas have greater numbers of seeds damaged and produce fewer viable seeds than plants in areas of low ant abundance. The vetches are more successful where ant abundance is low; larvae in the pods get parasitized, and fewer seeds are damaged. These data imply that pod feeders may have successfully short—circuited extrafloral nectary—mediated ant defense for their own benefit.
Mutualism Denied? Nectar‐Robbing Bumble Bees do not Reduce Female or Male Success of Bluebells
Authors: Morris William F.
Published: May 2006

Although mutualisms are often viewed as fragile constructs, subject to invasion by “cheaters“ that gain from the mutualism without providing compensating benefits, few studies have explored whether or not apparent cheating behavior by one player actually denies benefits to the other species. Panicled bluebells (Mertensia paniculata) experience high rates of nectar robbery by bumble bees (Bombus mixtus and B. frigidus) in the Wrangell Mountains of southcentral Alaska. Nevertheless, experimental prevention of nectar larceny in two seasons did not enhance components of female reproductive success (nutlet initiation, seed—set, and seed mass) or male success (pollen removal). Observational data show that the absence of a negative impact of nectar robbery is a consequence of bumble bee behaviors; the two bee species that rob mature flowers buzz—pollinate the same flowers at an earlier stage in floral development. The shift in bee behavior is driven by the presentation of different rewards at different times in the flowering period; young flowers contain pollen and older flowers produce nectar. Although flowers typically receive and donate pollen before most nectar is produced, the mature flowers producing a robbed nectar reward may nonetheless contribute to the reproductive success of bluebell plants. Flowers sequestered from pollinators in the early stage were still capable of initiating nutlets, demonstrating that older flowers can enhance female reproduction if pollinators are rare (when many early—stage flowers may go unvisited). Moreover, the removal of mature flowers reduced the visitation rate to early—stage flowers on the same plant. Because individual bumble bees switch frequently between nectar robbing and pollen collection, the nectar reward in mature flowers may act as a key enticement to pollinators, which then enhance plant reproduction by legitimately visiting early—stage flowers. Rather than representing a case of cheating behavior, nectar robbery may be an integral part of this plant—pollinator mutualism.
Effects of Individual Variation in Size on Growth and Development of Larval Salamanders
Authors: Brunkow Paul E. , Collins James P.
Published: May 2006

Theoretical population models suggest that variation among individuals can affect population—level properties like stability and equilibrial density. Few studies, however, have tested the importance of individual variation to factors affecting population dynamics (e.g., average individual growth rates, developmental rates, survivorship, etc.) using natural populations. We conducted a field experiment designed to test effects of larval density and individual variability in body size on growth and development of larval tiger salamanders (Ambystoma tigrinum nebulosum). We performed our experiment in a natural sinkhole lake in central Arizona; experimental populations differing in density and initial variability in body size were held in nylon mesh enclosures. Effects of individual variability in size were examined independently of any effects due to mean body size of the population or total population biomass. Density affected growth rates and development to metamorphosis of experimental larvae in a manner consistent with other studies. Initial variability in body size did not affect larval growth rates or diets but did interact with density to affect survivorship and development: experimental larvae held with similarly sized individuals experienced lower survivorship and were metamorphosing earlier than experimental larvae held with variably sized individuals. These effects did not appear to be mediated by size—specific competitive abilities but may have been mediated by individual behavioral responses to size structure. This study underscores the importance of incorporating information about interindividual variability into our understanding of processes affecting population dynamics.
Evolution and Stasis in Plant‐‐Pathogen Associations
Authors: Clay Keith , Kover Paula
Published: May 2006

The impact of disease on plant populations may change as a result of coevolutionary interactions. The Red Queen hypothesis suggests that parasites provide a selective advantage to host sexual recombination sufficient to explain it persistence despite the twofold advantage of asexual reproduction. The constant production of resistant host genotypes by sexual recombination favors parasite genotypes that can overcome host resistance, resulting in a coevolutionary arms race. Systemic fungal parasites differ from nonsystemic fungi in ways that affect plant—pathogen interactions. Many systemic fungal parasites castrate their host plants, which reduces the potential for production of genetically variable, resistant progeny. Moreover, host genotypes susceptible to infection by the maternal pathogen are perpetuated through parasite—induced asexual reproduction or enforced selfing. Grasses in the genus Danthonia infected by Atkinsonella hypoxylon represent a model system for investigating evolution and stasis in plant—pathogen associations. Infected plants, unlike uninfected plants, reproduce only by self—fertilized seed through which the fungus is vertically transmitted. Other similar associations exist, suggesting that parasites can often enforce genetic uniformity within host populations.
Diversity and Temporal Change in the Effective Pollinators of Asclepias Tuberosa
Authors: Fishbein Mark , Venable D. Lawrence
Published: May 2006

Although pollination effectiveness is a central process underlying the evolution of plant and pollinator traits, it is difficult to measure and has rarely been reported for a diverse spectrum of visitors under natural conditions. We measured the effectiveness of all common flower visitors to Asclepias tuberosa (butterfly weed) at a site in southeastern Arizona, in terms of visitation rate, per—visit rate of pollinia removal and insertion, and pollinia load. Bombus and Apis (Hymenoptera) were the most effective pollinators, counter to predictions that A. tuberosa is butterfly—pollinated. We also documented large differences between 2 yr in the pollination effectiveness of visitors, primarily due to changes in visitation rate. Bombus were the most frequent and effective pollinators in 1992. In 1993, Apis were equivalent to Bombus. Battus (Lepidoptera) were the second most effective pollinators in 1992, but were scarce in 1993. Thus, conclusions about the identity of effective pollinators based on floral traits, casual observations of visitation, or even precise measurement of effectiveness in a single season are all potentially suspect. We compare our results to those of previous studies of Asclepias pollination.
Competitive and Predatory Interactions among Raptors: An Observational and Experimental Study
Authors: Hakkarainen Harri , Korpimaki Erkki
Published: May 2006

We examined the effects of predatory and competitive interactions among three owl species on reproductive success and population composition of these raptors both experimentally and observationally. Eagle Owls (Bubo bubo, body mas $\approx$ 2700 g), Ural Owls (Strix uralensis, 900 g), and Tengmalm's Owls (Aegolius funereus, 130 g) coexist in Fennoscandia and feed mainly on small rodents. Predation may play an important role in interactions among these owl species, because Eagle Owls and Ural Owls can kill Tengmalm's Owls but cannot enter the small entrance hole of Tengmalm's Owl nest boxes. We asked (i) whether predation risk and interspecific competition due to Eagle Owls and Ural Owls reduced breeding density and fitness of Tengmalm's Owls, and (ii) whether these interactions increased intraspecific competition for safe nesting sites among Tengmalm's Owls. We manipulated breeding densities of potentially competing owls by erecting nest boxes, the control being boxes in areas where breeding attempts of competing owl species were absent. Control nest boxes in areas with no Eagle Owl and Ural Owl territories, and nest boxes within Eagle Owl territories, were used by breeding Tengmalm's Owls more than nest boxes within Ural Owl territories. Most breeding attempts of Tengmalm's Owls near Ural Owls failed during the courtsip period. The observational data revealed that breeding frequency of Tengmalm's Owls was reduced and the mean start of egg laying was delayed by 11 d within 2 km of Ural Owl nest. In addition, male Tengmalm's Owl at these nests were younger and paired more often with short—winged (i.e., young and generally subdominant) females than when farther away from Ura Owl nests. Our results suggest that inexperienced male Tengmalm's Owls are forced to establish their territories in the vicinity of Ura Owls where they often paired with subdominant females. The areas near Ura Owl nests are suboptimal habitats for Tengmalm's Owls, whereas those near Eagle Owls are not. We conclude that predatory and competitive interactions from Ural Owls decrease the breeding population size of Tengmalm's Owls by reducing the suitable habitats. This is the first experimental demonstration that such interactions may decrease fitness of raptors.
Within‐Population Variation in Demography of Taraxacum Officinale: Maintenance of Genetic Diversity
Authors: Vavrek M. C. , McGraw J. B. , Yang H. S.
Published: May 2006

Differential response of genotypes to temporal environmental heterogeneity may contribute to the long—term persistence of those genotypes within a population. We tested whether season—dependent fitness components of genotypes could be responsible for the maintenance of genetic diversity within a population. Clonal replicates of five genotypes of Taraxacum officinale were planted in each of four seasons (spring—April to July, summer—July to October, autumn—October to January, and winter—January to April). Individuals were planted directly into natural, field vegetation. Fitness components (establishment, survival, growth, seed production, and leaf area dominance) and an integrated measure of fitness (finite rate of increase) were measured for each genotype in each season. Differential genotypic responses to seasons were observed for all fitness components. Despite seasonal differences, genotypic performances summed across seasons were equivalent. This result indicates that temporal heterogeneity may have a substantial effect on within—population genetic structure. The persistence of genotypes of contrasting seasonal performance through time is expected if long—term fitness values remain similar
Intraguild Predation and Cannibalism among Larvae of Detritivorous Caddisflies in Subalpine Wetlands
Authors: Wissinger Scott A. , Sparks Grace B. , Rouse Gretchen L. , Brown Wendy S. , Steltzer Heidemarie
Published: May 2006

Comparative data from subalpine wetlands in Colorado indicate that larvae of the limnephilid caddisflies, Asynarchus nigriculus and Limnephilus externus, are reciprocally abundant among habitats–Limnephilus larvae dominate in permanent waters, whereas Asynarchus larvae dominate in temporary basins. The purpose of this paper is to report on field and laboratory experiments that link this pattern of abundance to biotic interactions among larvae. In the first field experiment, growth and survival were compared in single and mixed species treatments in littoral enclosures. Larvae, which eat mainly vascular plant detritus, grew at similar rates among treatments in both temporary and permanent habitats suggesting that exploitative competition is not important under natural food levels and caddisfly densities. However, the survival of Limnephilus larvae was reduced in the presence of Asynarchus larvae. Subsequent behavioral studies in laboratory arenas revealed that Asynarchus larvae are extremely aggressive predators on Limnephilus larvae. In a second field experiment we manipulated the relative sizes of larvae and found that Limnephilus larvae were preyed on only when Asynarchus larvae had the same size advantage observed in natural populations. Our data suggest that the dominance of Asynarchus larvae in temporary habitats is due to asymmetric intraguild predation (IGP) facilitated by a phenological head start in development. These data do not explain the dominance of Limnephilus larvae in permanent basins, which we show elsewhere to be an indirect effect of salamander predation. Behavioral observations also revealed that Asynarchus larvae are cannibalistic. In contrast to the IGP on Limnephilus larvae, Asynarchus cannibalism occurs among same—sized larvae and often involves the mobbing of one victim by several conspecifics. In a third field experiment, we found that Asynarchus cannibalism was not density—dependent and occurred even at low larval densities. We hypothesize that Asynarchus IGP and cannibalism provide a dietary supplement to detritus that may be necessary for the timely completion of development in these nutrient—poor, high—elevation wetlands.
Ecological Energetics of the Desert Tortoise (Gopherus Agassizii): Effects of Rainfall and Drought
Authors: Peterson Charles C.
Published: May 2006

To elucidate ecological effects of variation in the temporal distribution of a limiting resource (water in the Mojave Desert), energetics of two free—living populations of desert tortoises (Gopherus [Xerobates] agassizii) were studied concurrently over 18 mo with use of doubly—labeled water. Field metabolic rates (FMR) and feeding rates (estimated from rates of water influx and rates of change in dry mass) were highly variable. This variability was manifested at several levels, including seasonal changes within populations, year—to—year differences within populations, and differences between populations. Underlying observed patterns and contrasts was considerable variation among individuals. Much of the variation in energetic variables was associated with a single climatic variable, rainfall. Seasonal, annual, and interpopulation differences in FMR and foraging rates corresponded to differences in availability of free—standing water from rainstorms. At least some of the differences among individuals were apparently due to differences in proclivity or ability to drink. Tortoises had very low FMRs relative to other reptiles, which allowed them to tolerate long periods of chronic energy shortage during a drought. Calculations suggested that tortoises experienced a net loss of energy on their spring diet of succulent annual plants. If so, tortoises require drier forage to accrue an energy profit, which emphasizes their reliance on drinking rainwater (which can be stored in the bladder and resorbed later to hydrate dry forage). Further, it suggests that growth (as protein deposition) and net acquisition of energy may be temporally decoupled in desert tortoises, which has potential consequences for geographic variation in life history traits. Energy acquisition and expenditure in desert tortoises are thus strongly constrained by the contingencies of rainfall, both indirectly through effects on availability and quality of food, and directly through reliance on free—standing water for drinking, which is apparently necessary for achieving a net annual energy profit.
Ecosystem Engineering by a Dominant Detritivore in a Diverse Tropical Stream
Authors: Flecker Alexander S.
Published: May 2006

Prochilodus mariae (Characiformes: Prochilodontidae) is a detritivorous fish distributed throughout the Orinoco river basin of South America. Spectacular migrations of these fishes occur at the end of the rainy season into the Andean foothills. Prochilodus ingest large quantities of sediments and may thereby modify habitats in neotropical streams. The major objectives of this study were (1) to explore experimentally the importance of Prochilodus in structuring a tropical stream in the Venezuelan Andean piedmont, and (2) to determine whether there was sufficient ecological redundancy in a diverse and abundant assemblage of epibenthic fishes to compensate for the removal of Prochilodus. Community structure was compared among three experimental treatments: (1) Prochilodus exclusion, (2) Prochilodus enclosure, and (3) the natural fish assemblage. Selective exclusion of Prochilodus resulted in striking changes in community structure as measured by patterns of sediment accrual and the composition of algal and invertebrate assemblages. Highly significant increases in total dry mass and in ash—free dry mass of sediments accruing on stream—bottom substrates were observed almost immediately following the exclusion of Prochilodus. Moreover, the composition of algal and invertebrate assemblages was significantly modified by Prochilodus. Taxa such as diatoms were reduced in number when Prochilodus was present; in contrast, Prochilodus appeared to facilitate nitrogen—fixing cyanobacteria. Total invertebrate densities were greatest in the Prochilodus removal treatment; however, a variety of responses to the experimental treatments was observed among different taxa analyzed individually, including density reductions, increases, and no measurable effects. This study suggests that the detritivore Prochilodus is a functionally dominant species in Andean foothill streams via sediment—processing activities. Moreover, it provides little evidence to support the notion that strongly interacting species are limited to simple systems with few food web components.
Salmonberry Clonal and Population Structure: The Basis for a Persistent Cover
Authors: Tappeiner John , Zasada John , Ryan Peter , Newton Michael
Published: May 2006

To understand how populations of salmonberry (Rubus spectabilis) persist in common forest stand types, we studied the above— and belowground structure of salmonberry clones and populations in upland alder and conifer stands in riparian stands, and in 2—yr—old and 13— to 18—yr—old clearcuts in the central Oregon Coast Range. On undisturbed sites individual clones and populations replace aerial stems by rhizome extension, by production of new genets, and by sprouts from buds on old aerial stems. It appears that frequent initiation of aerial stems from these three sources enables salmonberry populations to persist and maintain a dense cover. The size distribution of aerial stems on these sites resembled that of an uneven—aged stand of trees, with stem numbers decreasing from small to large size classes. Within the first two growing seasons after disturbance to overstory trees and the understory, salmonberry populations maintained themselves by a rapid initiation of new rhizomes (1.0—1.5 m/m2 annually) and aerial stems (25—50 stems/m2). These populations apparently continue to grow well, since the greatest rhizome and aerial stem biomass occurred in 13— to 18—yr—old clearcuts with no overstory trees. Rhizome density of salmonberry populations, as well as rhizome and aerial stem biomass, was significantly and negatively related (r2 =0.71—O.83) to the basal area of overstory trees. It appears that population structure, rhizome length and aerial stem, rhizome, and total biomass, can be predicted from measures of preharvest overstory trees, and also from salmonberry stem number and basal area. Clonal architecture varied with stand type. Salmonberry clones in alder stands were larger (18 m total rhizome) than those in conifer stands and on riparian sites (5—6 m rhizome). Clones in alder stands also produced more ramets and more serial stems than those in conifer and riparian stands.
Four‐node semi‐EAS element in six‐field nonlinear theory of shells
Authors: Chróścielewski J. , Witkowski W.
Published: May 2006

We propose a new four‐node C0 finite element for shell structures undergoing unlimited translations and rotations. The considerations concern the general six‐field theory of shells with asymmetric strain measures in geometrically nonlinear static problems. The shell kinematics is of the two‐dimensional Cosserat continuum type and is described by two independent fields: the vector field for translations and the proper orthogonal tensor field for rotations. All three rotational parameters are treated here as independent. Hence, as a consequence of the shell theory, the proposed element has naturally six engineering degrees of freedom at each node, with the so‐called drilling rotation. This property makes the element suitable for analysis of shell structures containing folds, branches or intersections. To avoid locking phenomena we use the enhanced assumed strain (EAS) concept. We derive and linearize the modified Hu–Washizu principle for six‐field theory of shells. What makes the present approach original is the combination of EAS method with asymmetric membrane strain measures. Based on literature, we propose new enhancing field and specify the transformation matrix that accounts for the lack of symmetry. To gain knowledge about the suitability of this field for asymmetric strain measures and to assess the performance of the element, we solve typical benchmark examples with smooth geometry and examples involving orthogonal intersections of shell branches. Copyright © 2006 John Wiley & Sons, Ltd.
High‐dose therapy and autologous stem cell transplantation for children with HIV‐associated non‐Hodgkin lymphoma
Authors: Fluri Simon , Ammann Roland , Lüthy Annette Ridolfi , Hirt Andreas , Aebi Christoph , Duppenthaler Andrea , Leibundgut Kurt
Published: May 2006

In contrast to adults, autologous stem cell transplantation (ASCT) as part of the salvage strategy after high‐dose chemo/radiotherapy in human immunodeficiency virus (HIV) related Non‐Hodgkin lymphoma (NHL) is not yet established for children. We report on a 13‐year patient with congenital HIV infection and refractory Burkitt lymphoma, who was successfully treated by high‐dose therapy (HDT) including rituximab followed by ASCT. After 26 months follow‐up the patient remains in complete remission and his HIV parameters have normalized with continued highly active antiretroviral therapy (HAART). HIV infection may no longer exclude children from ASCT as part of salvage therapy. Pediatr Blood Cancer 2007;49:984–987. © 2006 Wiley‐Liss, Inc.
Postnatal follow‐up of prenatally diagnosed trisomy 16 mosaicism
Authors: Langlois Sylvie , Yong Paul J. , Yong Siu Li , Barrett Irene , Kalousek Dagmar K. , Miny Peter , Exeler Rita , Morris Kathy , Robinson Wendy P.
Published: May 2006

Objective

To determine the long‐term outcome of pregnancies prenatally diagnosed with trisomy 16 and identify variables associated with the outcome.

Methods

We reviewed all published and our unpublished data from trisomy 16 pregnancies for which outcomes were available for children of greater than 1 year of age.

Results

Nineteen cases were diagnosed with trisomy 16 on chorionic villus sampling (CVS) and 17 cases at amniocentesis. Age at last follow‐up ranges from 1 to13 years. Among the CVS group, four out of five patients, with a birth weight and/or length below −2 SD and postnatal growth information, showed catch‐up growth (80%). Among the amniotic fluid (AF) group, the birth weight was available in 13 cases. Eleven of the 13 cases had a birth weight less than −2 SD. In eight cases, the length was also below −2 SD (length data unavailable in one case). Nine out of ten cases (90%) and seven out of eight (87.5%) showed catch‐up growth for weight and length, respectively. In terms of development, no cases of CVS mosaicism had global developmental delay. One child had a history of delay in speech development. Among the AF‐detected cases, 4/17 cases had global developmental delay. All four children with global developmental delay had more than one major malformation compared to 6 out of 32 children in the group with normal development (p = 0.004). The finding of uniparental disomy (UPD) was not associated with developmental delay.

Conclusions

The majority of prenatally diagnosed trisomy 16 mosaic cases have a good postnatal outcome. However, the finding of mosaicism on AF and the presence of major congenital anomalies are associated with an increased risk of developmental delay. Copyright © 2006 John Wiley & Sons, Ltd.
Trisomy 15 mosaicism owing to familial reciprocal translocation t(1;15): implication for prenatal diagnosis
Authors: Prontera Paolo , Buldrini Barbara , Aiello Vincenzo , Gruppioni Rita , Bonfatti Alessandra , Venti Giovanna , Ferlini Alessandra , Sensi Alberto , Calzolari Elisa , Donti Emilio
Published: May 2006

We describe a 4‐year‐old female child with severe global mental retardation, myoclonic epilepsy, proximal hypotonia and dysmorphisms, whose prenatal diagnosis following amniocentesis revealed a constitutional female karyotype carrying a t(1;15)(q10;p11) familial reciprocal translocation. Post‐natal high‐resolution karyotype, Fluorescence in situ hybridization (FISH) screening for subtelomeric rearrangements, VNTR search for UPD15 in the blood and fibroblast, and WCP1 and 15 in the mother, failed to provide an explanation for the complex clinical phenotype of the proband. Since the pachytene configuration of the translocated chromosomes defines a high probability of 3:1 segregation, an extensive workup was undertaken to look for a possibly cryptic mosaicism. Four percent of the cells with trisomy 15 was found in the peripheral blood lymphocytes examined by classical cytogenetic technique and interphase FISH analysis. The clinical features associated with cryptic trisomy 15 mosaicism and the problems concerning prenatal diagnosis and genetic counselling for carriers of translocations at high risk of 3:1 segregation are discussed. Copyright © 2006 John Wiley & Sons, Ltd.
Heteroarm H‐shaped terpolymers through the combination of the Diels–Alder reaction and controlled/living radical polymerization techniques
Authors: Durmaz Hakan , Karatas Figen , Tunca Umit , Hizal Gurkan
Published: May 2006

Heteroarm H‐shaped terpolymers (PS)(PtBA)–PEO–(PtBA)(PS) and (PS)(PtBA)–PPO–(PtBA)(PS) [where PS is polystyrene, PtBA is poly(tert‐butyl acrylate), PEO is poly(ethylene oxide), and PPO is poly(propylene oxide)], containing PEO or PPO as a backbone and PS and PtBA as side arms, were prepared via the combination of the Diels–Alder reaction and atom transfer radical and nitroxide‐mediated radical polymerization routes. Commercially available PEO or PPO containing bismaleimide end groups was reacted with a compound having an anthracene functionality, succinic acid anthracen‐9‐yl methyl ester 3‐(2‐bromo‐2‐methylpropionyloxy)‐2‐methyl‐2‐[2‐phenyl‐2‐(2,2,6,6‐tetramethylpiperidin‐1‐yloxy)ethoxycarbonyl]propyl ester, with a Diels–Alder reaction strategy. The obtained macroinitiator with tertiary bromide and 2,2,6,6‐tetramethylpiperidin‐1‐oxy functional end groups was used subsequently in the atom transfer radical polymerization of tert‐butyl acrylate and in the nitroxide‐mediated free‐radical polymerization of styrene to produce heteroarm H‐shaped terpolymers with moderately low molecular weight distributions (<1.31). The polymers were characterized with 1H NMR, ultraviolet, gel permeation chromatography, and differential scanning calorimetry. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3947–3957, 2006
Note on ‘Construction of Double Sampling s‐Control Charts for Agile Manufacturing’
Authors: Hsu Lie‐Fern
Published: May 2006

He and Grigoryan (Quality and Reliability Engineering International 2002; 18:343–355) formulated the design of a double‐sampling (DS) s control chart as an optimization problem and solved it with a genetic algorithm. They concluded that the DS s control charts can be a more economically preferable alternative in detecting small shifts than traditional s control charts. We explain that, since they only considered the average sample size when the process is in control, their conclusion is questionable. Copyright © 2006 John Wiley & Sons, Ltd.
Bayesian meta‐analysis and meta‐regression for gene–disease associations and deviations from Hardy–Weinberg equilibrium
Authors: Salanti Georgia , Higgins Julian P. T. , Trikalinos Thomas A. , Ioannidis John P. A.
Published: May 2006

Violation of Hardy–Weinberg equilibrium (HWE) can raise doubts about the validity of the conclusions from genetic association studies. However, for most currently performed gene–disease association studies, the available tests have low power to detect deviations from HWE. We consider this issue from a meta‐analysis perspective, and suggest an approach to estimate the deviation and investigate its relationship with the observed genetic effects. Different degrees of deviation from HWE have previously been proposed as a potential source of heterogeneity across studies. We present a hierarchical meta‐regression model that can be applied to test this assumption, using the concept of the fixation coefficient. We re‐analyse seven meta‐analyses to illustrate these methods. The uncertainty in the genetic effect estimate tended to increase once the fixation coefficient was taken into account. Dependence of the genetic effect size on the deviation from HWE was found in one meta‐analysis, while in the other six examples, deviations from HWE did not clearly explain between‐study heterogeneity in the genetic effects. The proposed hierarchical models allow the synthesis of data across gene–disease association studies with appropriate consideration of HWE issues. Copyright © 2006 John Wiley & Sons, Ltd.
Grain size of activated carbon, and untreated and modified granular clinoptilolite under freeze-thaw: applications to permeable reactive barriers
Authors: Gore Damian B. , Heiden Erika S. , Snape Ian , Nash Geraldine , Stevens Geoffrey W.
Published: May 2006

Permeable reactive barriers are used to adsorb contaminants from soil water. Their fillings are granular materials whose stability under freezing conditions has not been demonstrated. In this research, three granular materials (activated carbon, raw clinoptilolite and a nutrient amended clinoptilolite) were subjected to freeze-thaw cycles at different moisture conditions, in order to simulate their use in permeable reactive barriers in areas of freezing ground. The <250 μm fraction, which will potentially accumulate grain fragments, showed no change for the carbon, but an increase from ∼1% to ∼3% abundance by volume for the clinoptilolite with modes at 100–200 μm. SEM images show cracks in the zeolite grains, forming fragments of the size observed in the particle size data. These findings may have implications for the long-term permeabilities of reactive barriers operated in areas of freezing ground.
Opioid and cannabinoid receptors: friends with benefits or just close friends?
Authors: Christie MacDonald J
Published: May 2006

μ‐Opioid (MOP) and cannabinoid CB1 receptors mediate overlapping pharmacological responses in clinically important areas such as drug abuse and pain management, and functional interactions between agonists at these receptors have long been recognized. In the present issue of this Journal, Rios and co‐workers have provided the first strong evidence that the two receptors interact directly when coexpressed in the same cells. The authors report a close physical association between MOP and CB1 receptors and novel pharmacological interactions of MOP and CB1 agonists. They argue that MOP/CB1 heterodimer formation explains these interactions. If correct, the direct interaction of MOP and CB1 pharmacophores in a quaternary complex would provide real benefits by opening the potential for development of novel MOP/CB1 small molecules or new strategies for use of current ligands. However, a lot more evidence will be required before the heterodimer interpretation can be accepted. If it turns out that MOP and CB1 receptors do not readily form hetero‐oligomers, the study by Rios and co‐workers shows that they are still friends but there may be few benefits.

British Journal of Pharmacology (2006) 148, 385–386. doi:10.1038/sj.bjp.0706756
Reinforcement of polymeric nanofibers by ferritin nanoparticles
Authors: Shin Min Kyoon , Kim Sun I. , Kim Seon Jeong , Kim Sung-Kyoung , Lee Haiwon
Published: May 2006

Poly(vinyl alcohol) (PVA) nanofibers containing bimolecular ferritin nanoparticles exhibited the enhancement of elastic modulus as compared to pure PVA nanofibers due to chemical interactions between the ferritin and the PVA matrix. The elastic modulus of the nanofibers was measured using a three-point bending test employing an atomic force microscope (AFM). To improve the reliability of the AFM measurements, uniform nanofibers were oriented linearly on an AFM calibration grating by introducing parallel subelectrodes in an electrospinning system. The length to diameter ratio of the measured nanofibers was >16. The PVA nanofibers reinforced by ferritin are applicable as artificial muscles and actuators.
Cloning, sequencing and expression of the transferrin-binding protein 2 gene fromActinobacillus pleuropneumoniae
Authors: Fang Wang , Kong-Wang He
Published: May 2006

To amplify the transferrin-binding protein 2 (Tbp2) gene fromActinobacillus pleuropneumoniae(App) by polymerase chain reaction (PCR), a pair of primers were designed according to sequence Z46774 ofA. pleuropneumoniaeserotype 5. The amplified DNA fragment (1642 bp) was cloned into pMD18-T and sequenced. The sequencing result showed that the homology was 99.8% compared with the reference sequence. The target fragment of the positive clones was inserted into pET-32a and transformed inEscherichia coliBL21 (DE3). After its induction, the fragment was expressed inE. coli. The Western blotting results were positive.
Enteral feeding: the effect on faecal output, the faecal microflora and SCFA concentrations
Authors: Whelan Kevin , Judd Patricia A , Preedy Victor R. , Taylor Moira A.
Published: May 2006

Enteral tube feeding is common in both the hospital and community environment; however, patients can suffer alterations in faecal output that can have serious clinical sequelae. Problems associated with accurate characterisation of faecal output and definition of diarrhoea impede the comparison of research studies and prevent standardised assessment of therapeutic interventions in clinical practice. The colonic microflora may protect the patient against diarrhoea by preventing enteropathogenic infection and by producing SCFA that stimulate colonic water absorption. However, studies in healthy volunteers suggest that the composition of the enteral formula may have a negative impact on the microflora and SCFA concentrations. The addition of fructo-oligosaccharides to the enteral formula may partially prevent negative alterations to the microflora, although conclusive data from studies in patients are not yet available. Modification of the microflora with probiotics and prebiotics may hold potential in prophylaxis against diarrhoea during enteral tube feeding.