bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intermittent low temperatures constrain spring recovery of photosynthesis in boreal Scots pine forests
Authors: Ensminger Ingo , Sveshnikov Dmitry , Campbell Douglas A. , Funk Christiane , Jansson Stefan , Lloyd Jon , Shibistova Olga , Öquist Gunnar 
Published: December 2004

AbstractDuring winter and early spring, evergreen boreal conifers are severely stressed because light energy cannot be used when photosynthesis is pre‐empted by low ambient temperatures. To study photosynthetic performance dynamics in a severe boreal climate, seasonal changes in photosynthetic pigments, chloroplast proteins and photochemical efficiency were studied in a Scots pine forest near Zotino, Central Siberia. In winter, downregulation of photosynthesis involved loss of chlorophylls, a twofold increase in xanthophyll cycle pigments and sustained high levels of the light stress‐induced zeaxanthin pigment. The highest levels of xanthophylls and zeaxanthin did not occur during the coldest winter period, but rather in April when light was increasing, indicating an increased capacity for thermal dissipation of excitation energy at that time. Concomitantly, in early spring the D1 protein of the photosystem II (PSII) reaction centre and the light‐harvesting complex of PSII dropped to their lowest annual levels. In April and May, recovery of PSII activity, chloroplast protein synthesis and rearrangements of pigments were observed as air temperatures increased above 0°C. Nevertheless, severe intermittent low‐temperature episodes during this period not only halted but actually reversed the physiological recovery. During these spring low‐temperature episodes, protective processes involved a complementary function of the PsbS and early light‐induced protein thylakoid proteins. Full recovery of photosynthesis did not occur until the end of May. Our results show that even after winter cold hardening, photosynthetic activity in evergreens responds opportunistically to environmental change throughout the cold season. Therefore, climate change effects potentially improve the sink capacity of boreal forests for atmospheric carbon. However, earlier photosynthesis in spring in response to warmer temperatures is strongly constrained by environmental variation, counteracting the positive effects of an early recovery process.
Groundwater use and salinization with grassland afforestation
Authors: Jobbágy Esteban G. , Jackson Robert B. 
Published: December 2004

AbstractVegetation changes, particularly transitions between tree‐ and grass‐dominated states, can alter ecosystem water balances and soluble salt fluxes. Here we outline a general predictive framework for understanding salinization of afforested grasslands based on biophysical, hydrologic, and edaphic factors. We tested this framework in 20 paired grassland and adjacent afforested plots across ten sites in the Argentine Pampas. Rapid salinization of groundwater and soils in afforested plots was associated with increased evapotranspiration and groundwater consumption by trees, with maximum salinization occurring on intermediately textured soils. Afforested plots (10–100 ha in size) showed 4–19‐fold increases in groundwater salinity on silty upland soils but <twofold increases on clay loess soils and sand dunes. Two years of salinity and groundwater measurements at a 40 haEucalyptus camaldulensisplantation revealed that the plantation reduced groundwater recharge, underwent groundwater discharge on >50% of the days, and depressed the water table 38 cm on average compared to the adjacent grassland. Soil cores and vertical electrical soundings indicated that ≈6 kg m−2of salts accumulated close to the water table and suggested that salinization resulted from the exclusion of fresh groundwater solutes by tree roots. Groundwater use with afforestation in the Pampas and in other regions around the world can enhance primary production and provide a tool for flood control. However, our framework and experimental data also suggest that afforestation can compromise the quality of soils and water resources in predictable ways based on water use, climate, and soil texture.
Elevated CO2 alters birch resistance to Lagomorpha herbivores
Authors: Mattson William J. , Kuokkanen Kari , Niemelä Pekka , Julkunen‐Tiitto Riitta , Kellomäki Seppo , Tahvanainen Jorma 
Published: December 2004

AbstractWe studied the three‐way interaction of elevated CO2, nitrogen (N), and temperature (T), and the two‐way interaction of elevated CO2 and early‐season defoliation on the secondary chemistry and resistance of Eurasian silver birch (Betula pendula) and North American paper birch (B. papyrifera) against the Eurasian hare (Lepus timidus) and the North American eastern cottontail rabbit (Sylvilagus floridanus), respectively. Elevated CO2 decreased the palatability of winter‐dormant silver and paper birch stems to both hares and rabbits, respectively. But the effect on hares was only apparent at intermediate levels of N fertilization. Elevated T had no effect on palatability. The effects of elevated CO2, N, and T on levels of silver birch bark phenolics and terpenoids were dominated by two‐way interactions between N and CO2, and N and T. Generally, however, N amendments elicited a parabolic response in carbon partitioning to most biosynthetic classes of silver birch phenolics (i.e. highest concentrations occurring at intermediate N). CO2 elevation was most enhancing at highest levels of N. On the other hand, T increases, more often than not, elicited reductions in phenolics, but especially so at the highest N level. In the case of B. papyrifera, elevated CO2 increased carbon partitioning to Folin‐Denis stem and branch phenolics and condensed tannins. Early‐season defoliation, on the other hand, had no effect on phenolics and tannins but lowered both N and energy levels of branches. Elevated CO2 substantially ameliorated the negative effects of severe defoliation on tree growth. These results support the hypothesis that continuing anthropogenic alterations of the atmosphere may trigger significant changes in plant phenotypic resistance to mammalian herbivores owing to an increasing net carbon balance between the highly vagile supply and demand capacities of plant carbon sources and sinks.
Phytogeography, range size and richness of Australian endemic Sauropus (Euphorbiaceae)
Authors: Hunter John T. 
Published: December 2004

AbstractAim  To investigate the distribution of Australian species of Sauropus. The information obtained is used to (1) identify areas of highest richness and centres of endemism, (2) investigate latitudinal gradients of richness and range size, (3) determine the types of rarity shown, and (4) provide hypotheses on historical biogeography of the genus within Australia.Location  Australia.Methods  Specimens from 17 herbaria and field searches were examined and label and field information collated on distribution, habit and habitat. Distribution information was used to map all species within 784 grid cells of 1° × 1° and within the 97 Australian ‘ecological regions’. Morphometric cluster analysis of species was conducted using Kulczynski association and flexible UPGMA on 23 character states. Simple regression was used to correlate species richness, density and range size to changes in latitude. CLIMEX is used to match the climate of the region of highest richness in Australia with other areas of the world.Results  Species richness was highest within the tropical north of Australia, and most species were associated with tropical savanna woodlands. Two areas were identified as centres of endemism and these corresponded closely to areas of high species richness. Four morphological groups were identified. One species (Sauropus trachyspermus) was found to be widespread, however all other species had small geographical ranges. Species richness and range size were significantly correlated with changes in latitude. Ten species were found to be of the rarest type, warranting conservation initiatives.Main conclusions  Two regions of high richness and endemism of Sauropus occur, Thailand and Australia. Within Australia, the Kakadu‐Alligator River and the Cairns‐Townsville areas were identified as centres of endemism and high species richness for Sauropus. Australian Sauropus in general occur in similar communities and climates as other members of the genus elsewhere. Ten of the 27 species of Australian endemic Sauropus are extremely rare and warrant conservation initiatives. Correlations of latitude to species richness are potentially due to Sauropus radiating from the climatically stable top end of Australia. Increasing range size in more southern latitudes may also be due to stability of climates in the top end or because there is more available land area at these latitudes. Sauropus micranthus, the only non‐endemic species, is probably a more recent invader from the Tertiary period when tropical rain forests where more extensive and congruent with those of New Guinea.
Desert vines: a comparison of Australia with other areas
Authors: Parsons R. F. 
Published: December 2004

AbstractAim  To characterize the Australian desert vine flora and to compare it with that of deserts in other continents.Location  The Stony Deserts, the Simpson Desert and the four main deserts of Western Australia.Methods  The Western Australian Herbarium data base and published papers were used to develop vine checklists for each Australian desert studied. A literature search was used to classify the families and genera into phytogeographical elements and to provide data for intercontinental comparisons.Results  Thirty‐seven vine species are listed for the six Australian deserts studied. They constitute from 0.8 to 2.7% of the vascular flora, which is within the normal range for arid zone floras. Comparing Australian data with those from the Sonoran and Chihuahuan deserts (North America), for non‐vine taxa, very different phylogenetic lines are present. However, for vines, three of the four most important families are the same in each case, viz. Convolvulaceae, Fabaceae and Asclepiadaceae. This reflects large pantropical and cosmopolitan families shared between all three data sets. At the generic level, in Australia pantropical taxa and taxa from the Old World tropics far outnumber endemic ones, as do pantropical and neotropical genera in North America. Herbaceous vines predominate in Australian deserts as they do in North American ones, but nevertheless, the percentage of woody vines is higher in Australia (32%) than in North America (highest value of 24%). Earlier views that Australian deserts are rich in annual vines are not supported.Main conclusions  For many life‐forms, the Australian flora is composed of very different phylogenetic lines to the floras of other continents. However, for desert vines, at the level of family and even of genus, there are surprising similarities between Australia and even a continent as distant as North America, because of shared pantropical and cosmopolitan taxa.
Nestedness of Southern Ocean island biotas: ecological perspectives on a biogeographical conundrum
Authors: Greve Michelle , Gremmen Niek J. M. , Gaston Kevin J. , Chown Steven L. 
Published: December 2004

AbstractAim To use patterns of nestedness in the indigenous and non‐indigenous biotas of the Southern Ocean islands to determine the influence of dispersal ability on biogeographical patterns, and the importance of accounting for variation in dispersal ability in their subsequent interpretation, especially in the context of the Insulantarctic and multi‐regional hypotheses proposed to explain the biogeography of these islands.Location Southern Ocean islands.Methods Nestedness was determined using a new metric,d1(a modification of discrepancy), for the indigenous and introduced seabirds, land birds, insects and vascular plants of 26 Southern Ocean islands. To assess the possible confounding effects of spatial autocorrelation on the results, islands were assigned to 11 major island groups and each group was treated as a single island in a following analysis. In addition, nestedness of the six Southern Ocean islands comprising the South Pacific Province (New Zealand islands) was analysed. All analyses were conducted for species and genera, for each of the taxa on its own, and for the complete data sets.Results Statistically significant nestedness was found in all of the taxa examined, with nestedness declining in the order seabirds > land birds > vascular plants > insects for the indigenous species. Vagility had a marked influence on nestedness and the biogeographical patterns shown by the indigenous species. This influence was borne out by additional analyses of marine taxa and small‐sized terrestrial species, both of which were more nested than the most nested group examined here, the seabirds. Assemblages of non‐indigenous species also showed nestedness, and nestedness was generally more pronounced than in the indigenous species. Surprisingly, vagility had a significant effect on nestedness in these assemblages too.Main conclusions Nestedness analyses provide a quantitative means of comparing biogeographical patterns for groups differing in vagility. These comparisons revealed that vagility has a considerable influence on biogeographical patterns and should be taken into account in analyses. Here, investigations of more vagile taxa support hypotheses for a single origin of the Southern Ocean island biota (the Insulantarctica scenario), whilst those of less mobile taxa support the more commonly held, multi‐regional hypothesis. All biogeographical analyses across the Southern Ocean (and elsewhere) will be influenced by the effects of dispersal ability, with composite analyses dominated by sedentary groups likely to favour multi‐regional scenarios, and those dominated by mobile groups favouring single origins. Mechanisms underlying nestedness in the region range from nested physiological tolerances in more mobile groups to colonization ability and patterns of speciation in less vagile taxa. Considerable nestedness in the non‐indigenous assemblages is largely a consequence of the fact that many of these species are European weedy species.
The Southern African orchid flora: composition, sources and endemism
Authors: Linder H. P. , Kurzweil H. , Johnson S. D. 
Published: December 2004

AbstractAim The Southern African orchid flora is taxonomically well known, but the biogeographical and diversity patterns have not yet been analysed. In particular, we want to establish whether (a) it is, like the Southern African flora in general, more diverse than would be expected from its latitude and area; (b) it is an African flora, or whether it contains palaeoendemic relicts of a Gondwanan orchid flora; (c) the diversity and endemism in the orchid flora is concentrated in particular biomes and habitat types; and (d) the patterns of endemism in the flora can be accounted for by current environmental parameters, or whether we need to invoke historical explanations.Location Southern Africa.Methods We used the recent floristic account of the Southern African orchids, in conjunction with a data base of over 14,642 herbarium records, to assign the species and subspecies of Southern African orchids to biomes, habitats, and clades. We explored the relationship between the number and endemism of entities (species, subspecies and varieties) and the biomes and habitats. We compared the richness of this flora with that of 31 other regions from all continents and latitudes, to establish whether the Southern African orchid flora is richer or poorer than expected. We assigned the Southern African orchid species to 16 monophyletic clades and mapped the global distribution of these clades to establish the continental affinities of the flora.Main conclusions The Southern African orchid flora is not any more diverse than could be expected from its latitude or area, while the two tropical African floras included were less diverse than expected. Latitude is an excellent predictor of regional orchid species richness; this might indicate that available habitat is more important for orchid diversity than gross area available, since latitude is probably correlated with the extent of suitable habitat. The Southern African orchid flora is clearly an African flora, since all clades are also found in tropical Africa, while many of them are absent from the Americas or Asia. Conversely, while most African orchid clades are also found in Southern Africa, both the Americas and Asia contain many clades absent from Africa. The distribution of orchid entities among the biomes in Southern Africa is very uneven, with two of the seven biomes totally devoid of orchids. Habitats and biomes that have no equivalent in tropical Africa are high in endemism, and habitats and biomes which are also well developed in tropical Africa are low in endemism. Endemism appears largely explained in terms of modern habitats. However, two patterns (the high endemism in the Succulent Karoo and the lack of endemism in the southern Cape among epiphytic orchids) may also be explained in terms of Quaternary climatic changes.
Major histocompatibility complex variation at three class II loci in the northern elephant seal
Authors: Weber Diana S. , Stewart Brent S. , Schienman John , Lehman Niles 
Published: December 2004

AbstractNorthern elephant seals were hunted to near extinction in the 19th century, yet have recovered remarkably and now number around 175 000. We surveyed 110 seals for single‐strand conformation polymorphism (SSCP) and sequence variation at three major histocompatibility (MHC) class II loci (DQA, DQB and DRB) to evaluate the genetic consequences of the population bottleneck at these loci vs. other well‐studied genes. We found very few alleles at each MHC locus, significant variation among breeding sites for the DQA locus, and linkage disequilibrium between the DQB and DRB loci. Northern elephant seals are evidently inbred, although there is as yet no evidence of correlative reductions in fitness.
The serine/threonine protein phosphatase SIT4 modulates yeast‐to‐hypha morphogenesis and virulence in Candida albicans
Authors: Lee Chang‐Muk , Nantel André , Jiang Linghuo , Whiteway Malcolm , Shen Shi‐Hsiang 
Published: December 2004

Summary SIT4 encodes the multifunctional catalytic subunit of a type 2A‐related protein phosphatase of Saccharomyces cerevisiae and has been implicated in cell cycle regulation and nitrogen sensing. We have identified the Candida albicans homologue of SIT4, and we show that its disruption caused a significant reduction in general growth rate, in hyphal outgrowth and in virulence in a mouse infection model. These phenotypes were reversed by the reintroduction of the wild‐type SIT4 gene. We used glass DNA microarrays to measure the transcriptional profiles of 6287 open reading frames in sit4 cells undergoing the yeast‐to‐hypha transition induced by serum. Although differential expression of many of the hyphae‐specific genes was not affected by the SIT4 deletion, the transcription of two new hyphae‐induced genes, XOG1 and YNR67, was entirely reliant upon Sit4p. Both genes represent glucanases, indicating that SIT4 may play a role in controlling cell wall biogenesis. Furthermore, sit4 cells exhibited a reduced heat shock response to treatment with serum/37°C, suggesting that SIT4 acts to co‐ordinate the stress response signals during morphological switching. Finally, sit4 cells displayed reduced transcript levels for the genes encoding the Hog1p MAP kinase and several modulators of protein biosynthesis. Sit4p thus plays important roles during hyphal growth in Candida albicans through the regulation of cell wall biogenesis, osmosensing and protein translation.
Structure of the OmpA‐like domain of RmpM from Neisseria meningitidis
Authors: Grizot Sylvestre , Buchanan Susan K. 
Published: December 2004

SummaryRmpM is a putative peptidoglycan binding protein from Neisseria meningitidis that has been shown to interact with integral outer membrane proteins such as porins and TonB‐dependent transporters. Here we report the 1.9 Å crystal structure of the C‐terminal domain of RmpM. The 150‐residue domain adopts a βαβαββ fold, as first identified in Bacillus subtilis chorismate mutase. The C‐terminal RmpM domain is homologous to the periplasmic, C‐terminal domain of Escherichia coli OmpA; these domains are thought to be responsible for non‐covalent interactions with peptidoglycan. From the structure of the OmpA‐like domain of RmpM, we suggest a putative peptidoglycan binding site and identify residues that may be essential for binding. Both the crystal structure and solution experiments indicate that RmpM may exist as a dimer. This would promote more efficient peptidoglycan binding, by allowing RmpM to interact simultaneously with two glycan chains through its C‐terminal, OmpA‐like binding domain, while its (structurally uncharacterized) N‐terminal domain could stabilize oligomers of porins and TonB‐dependent transporters in the outer membrane.
Scrotal ulceration induced by all‐trans retinoic acid in a patient with acute promyelocytic leukemia
Authors: Mourad Yasser Abou , Jabr Fadi , Salem Ziad 
Published: December 2004

AbstractAll‐trans retinoic acid (ATRA) has been shown to improve the outcome in patients with acute promyelocytic leukemia compared with chemotherapy alone, but it is associated with adverse effects. We report the development of scrotal ulcer in a patient with acute promyleocytic leukemia (APL) within 10 days of treatment with ATRA at a dose of 40 mg orally twice daily. The ulcer did not respond to antibiotic treatment and healed shortly after withholding ATRA. The biopsy showed inflammation only, and other microbiological workup was negative.
The value of Doppler ultrasound in diagnosis in 25 cases of furunculoid myiasis
Authors: Quintanilla‐Cedillo Marco R. , León‐Ureña Heberth , Contreras‐Ruiz José , Arenas Roberto 
Published: December 2004

AbstractBackground  The larvae of the botfly Dermatobia hominis cause furunculoid myiasis in endemic areas. Lack of knowledge of this condition outside these areas leads to confusion in diagnosis and delays appropriate treatment.Objective  To describe the clinical findings of furunculoid myiasis encountered in Quintana Roo, in the south‐east of Mexico.Materials and methods  We performed an observational study on 25 cases diagnosed over a period of 4 years.Results  Diagnosis of furunculoid myiasis was made in 14 males and 11 females with an average age of 24.5 years. Most of our patients were students, farmers, or housewives. The number of lesions varied from one to four. In 20% of cases, more than one parasite was present in each lesion. The scalp was the most commonly affected region (40%), followed by the trunk and the extremities. Doppler ultrasound study (DUSG) of the furuncle‐like lesions confirmed the clinical diagnosis in all cases.Conclusions  Furunculoid myiasis is frequent in the state of Quintana Roo, Mexico. We found no association with occupation, gender, social background or age. DUSG can be used to evaluate the number of parasites per furunculoid lesion avoiding misdiagnoses and treatment delays.