140 research outputs found

    New species and records of tree ferns (Cyatheaceae, Pteridophyta) from the northern Andes

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    AbstractFour new species of Cyatheaceae from Ecuador are described: Alsophila conantiana Lehnert, Cyathea brucei Lehnert, C. moranii Lehnert, and C. sylvatica Lehnert. Range extensions are documented for Alsophila esmeraldensis R.C. Moran and Cyathea macrocarpa (C. Presl) Domin.For full article, see Electronic Supplement at: http://www.senckenberg.de/odes/06-13.ht

    Influence of Increasing Nutrient Availability on Fern and Lycophyte Diversity

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    Increased nutrient supply can have drastic effects on natural ecosystems, especially in naturally nutrient-poor ones such as most tropical rainforests. Many studies have focused on the reaction of trees to fertilization, but little is known about herbaceous plants. Ferns are a particularly common group in tropical forests, spanning all vegetation types and zones. Here, we assess how seven years of moderate addition of nitrogen (N), phosphorus (P), and N+P along an elevational gradient (1000–3000 m) have impacted richness and composition of fern and lycophyte assemblages in tropical montane rain forests growing on naturally nutrient deficient soils in the Ecuadorian Andes. We found that fertilization does not affect overall species richness, but that there were strong differences in species abundances (∼60% of species), both negative and positive, that were apparently related to the systematic affiliations and ecological properties of the affected species. These diverse responses of ferns to fertilization provide insight into the sensitivity and complexity of the relationships of nutrient availability and community composition in tropical forests

    Adiciones a la pteridoflora de Tabasco, México: la importancia del bosque mesófilo de montaña

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    Background and Aims: The ejido Villa de Guadalupe of the municipality of Huimanguillo, Tabasco, contains the only fragment of humid montane forest in the state, which has been little explored floristically. This study is an addition to those previously published, where reports of new records increase considerably the richness of fern species known so far for Tabasco state. The main objective is to update the knowledge of the pteridophyte flora of this state, emphasizing the importance of the humid montane forest.Methods: Epiphytic and terrestrial fern collections were made randomly on the north and northeast face of the Las Flores mountain (450-1000 m a.s.l.) in the municipality of Huimanguillo. Specimens were identified mainly by dichotomous keys and distributed to national and foreign herbaria.Key results: A total of 64 species of ferns and lycopods were recorded. The best represented families were Polypodiaceae, Dryopteridaceae and Hymenophyllaceae. We highlight the records of 30 species that had not previously been reported in the state of Tabasco. Even of the genera Cochlidium, Elaphoglossum, Hypolepis, Odontosoria, Parapolystichum, Polytaenium, Saccoloma and Sphaeropteris, this is the first report for the state.Conclusions: The new additions to the pteridophyte flora of Tabasco lead to a count of 169 species for the state, which updates the information known so far (137 species) and shows the need of continued regional floristic inventories. The present study represents one of the few published papers that document the richness of a specific taxonomic group in the humid montane forest of the state.Antecedentes y Objetivos: El ejido Villa de Guadalupe del municipio Huimanguillo, Tabasco, mantiene el único fragmento de bosque mesófilo de montaña en el estado, mismo que ha sido florísticamente poco explorado. Este estudio se suma a otros anteriormente publicados, donde los reportes de nuevos registros aumentan considerablemente la riqueza de especies de helechos y licopodios conocidas hasta ahora para Tabasco. El objetivo principal es actualizar el conocimiento de la pteridoflora de la entidad, enfatizando la importancia del bosque mesófilo de montaña.Métodos: Se realizaron colectas al azar de helechos epífitos y terrestres en la cara norte y noreste del cerro Las Flores (450-1000 m s.n.m.) en el municipio Huimanguillo. Los especímenes fueron identificados principalmente mediante claves taxonómicas y distribuidos en herbarios nacionales y extranjeros.Resultados clave: Se registraron en total 64 especies de helechos y licopodios. Las familias mejor representadas fueron Polypodiaceae, Dryopteridaceae e Hymenophyllaceae. Se destaca el registro de 30 especies que no habían sido reportadas previamente en el estado de Tabasco. Para los géneros Cochlidium, Elaphoglossum, Hypolepis, Odontosoria, Parapolystichum, Polytaenium, Saccoloma y Sphaeropteris, este es el primer reporte para la entidad.Conclusiones: Las nuevas adiciones a la pteridoflora de Tabasco proporcionan un recuento de 169 especies para el estado, lo cual actualiza la información conocida hasta ahora (137 especies) y manifiesta la necesidad de continuar con la realización de inventarios florísticos regionales. El presente estudio representa uno de los pocos trabajos publicados que documentan la riqueza de un grupo taxonómico en específico en el bosque mesófilo de montaña del estado

    Slowly but surely: gradual diversification and phenotypic evolution in the hyper-diverse tree fern family Cyatheaceae

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    Background and Aims The tremendously unbalanced distribution of species richness across clades in the tree of life is often interpreted as the result of variation in the rates of diversification, which may themselves respond to trait evolution. Even though this is likely a widespread pattern, not all diverse groups of organisms exhibit heterogeneity in their dynamics of diversification. Testing and characterizing the processes driving the evolution of clades with steady rates of diversification over long periods of time are of importance in order to have a full understanding of the build-up of biodiversity through time. Methods We studied the macroevolutionary history of the species-rich tree fern family Cyatheaceae and inferred a time-calibrated phylogeny of the family including extinct and extant species using the recently developed fossilized birth–death method. We tested whether the high diversity of Cyatheaceae is the result of episodes of rapid diversification associated with phenotypic and ecological differentiation or driven by stable but low rates of diversification. We compared the rates of diversification across clades, modelled the evolution of body size and climatic preferences and tested for trait-dependent diversification. Key Results This ancient group diversified at a low and constant rate during its long evolutionary history. Morphological and climatic niche evolution were found to be overall highly conserved, although we detected several shifts in the rates of evolution of climatic preferences, linked to changes in elevation. The diversification of the family occurred gradually, within limited phenotypic and ecological boundaries, and yet resulted in a remarkable species richness. Conclusions Our study indicates that Cyatheaceae is a diverse clade which slowly accumulated morphological, ecological and taxonomic diversity over a long evolutionary period and provides a compelling example of the tropics as a museum of biodiversity

    Self-Assembled Nanometer-Scale Magnetic Networks on Surfaces: Fundamental Interactions and Functional Properties

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    Nanomagnets of controlled size, organized into regular patterns open new perspectives in the fields of nanoelectronics, spintronics, and quantum computation. Self-assembling processes on various types of substrates allow designing fine-structured architectures and tuning of their magnetic properties. Here, starting from a description of fundamental magnetic interactions at the nanoscale, we review recent experimental approaches to fabricate zero-, one-, and two-dimensional magnetic particle arrays with dimensions reduced to the atomic limit and unprecedented areal density. We describe systems composed of individual magnetic atoms, metal-organic networks, metal wires, and bimetallic particles, as well as strategies to control their magnetic moment, anisotropy, and temperature-dependent magnetic behavior. The investigation of self-assembled subnanometer magnetic particles leads to significant progress in the design of fundamental and functional aspects, mutual interactions among the magnetic units, and their coupling with the environment

    Simulating Supersonic Turbulence in Galaxy Outflows

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    We present three-dimensional, adaptive mesh simulations of dwarf galaxy out- flows driven by supersonic turbulence. Here we develop a subgrid model to track not only the thermal and bulk velocities of the gas, but also its turbulent velocities and length scales. This allows us to deposit energy from supernovae directly into supersonic turbulence, which acts on scales much larger than a particle mean free path, but much smaller than resolved large-scale flows. Unlike previous approaches, we are able to simulate a starbursting galaxy modeled after NGC 1569, with realistic radiative cooling throughout the simulation. Pockets of hot, diffuse gas around individual OB associations sweep up thick shells of material that persist for long times due to the cooling instability. The overlapping of high-pressure, rarefied regions leads to a collective central outflow that escapes the galaxy by eating away at the exterior gas through turbulent mixing, rather than gathering it into a thin, unstable shell. Supersonic, turbulent gas naturally avoids dense regions where turbulence decays quickly and cooling times are short, and this further enhances density contrasts throughout the galaxy- leading to a complex, chaotic distribution of bubbles, loops and filaments as observed in NGC 1569 and other outflowing starbursts.Comment: 22 pages, 13 figures, MNRAS, in pres

    All-cause mortality and serum insulin-like growth factor I in primary care patients

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    Objective: Previous population-based studies provided conflicting results regarding the association of total serum insulin-like growth factor I (IGF-I) and mortality. The aim of the present study was to assess the relation of IGF-I levels with all-cause mortality in a prospective study. Design: DETECT (Diabetes Cardiovascular Risk-Evaluation: Targets and Essential Data for Commitment of Treatment) is a large, multistage, and nationally representative study of primary care patients in Germany. The study population included 2463 men and 3603 women. Death rates were recorded by the respective primary care physician. Serum total IGF-I levels were determined by chemiluminescence immunoassays and categorized into three groups (low, moderate, and high) according to the sex- and age-specific 10th and 90th percentiles. Results: Adjusted analyses revealed that men with low [hazard ratio (HR) 1.70 (95% confidence interval [CI] 1.05–2.73), p=0.03] and high [HR 1.76 (95% CI 1.09–2.85), p=0.02] IGF-I levels had higher risk of all-cause mortality compared to men with moderate IGF-I levels. The specificity of low IGF-I and high IGF-I levels increased with lower and higher cut-offs, respectively. No such association became apparent in women. Conclusions: The present study revealed a U-shaped relation between IGF-I and all-cause mortality in male primary care patients

    Final results of a phase I/II pilot study of capecitabine with or without vinorelbine after sequential dose-dense epirubicin and paclitaxel in high-risk early breast cancer

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    Background: The integration of the non-cross-resistant chemotherapeutic agents capecitabine and vinorelbine into an intensified dose-dense sequential anthracycline- and taxane-containing regimen in high-risk early breast cancer (EBC) could improve efficacy, but this combination was not examined in this context so far. Methods: Patients with stage II/IIIA EBC (four or more positive lymph nodes) received post-operative intensified dose-dense sequential epirubicin (150mg/m2 every 2 weeks) and paclitaxel (225mg/m2 every 2 weeks) with filgrastim and darbepoetin alfa, followed by capecitabine alone (dose levels 1 and 3) or with vinorelbine (dose levels 2 and 4). Capecitabine was given on days 1-14 every 21 days at 1000 or 1250 mg/m2 twice daily (dose levels 1/2 and 3/4, respectively). Vinorelbine 25 mg/m2 was given on days 1 and 8 of each 21-day course (dose levels 2 and 4). Results: Fifty-one patients were treated. There was one dose-limiting toxicity (DLT) at dose level 1. At dose level 2 (capecitabine and vinorelbine), five of 10 patients experienced DLTs. Therefore evaluation of vinorelbine was abandoned and dose level 3 (capecitabine monotherapy) was expanded. Hand-foot syndrome and diarrhoea were dose limiting with capecitabine 1250 mg/m2 twice daily. At 35.2 months' median follow-up, the estimated 3-year relapse-free and overall survival rates were 82% and 91%, respectively. Administration of capecitabine monotherapy after sequential dose-dense epirubicin and paclitaxel is feasible in node-positive EBC, while the combination of capecitabine and vinorelbine as used here caused more DLTs. Trial registration: Current Controlled Trials ISRCTN38983527
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