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ResumenLos gradientes altitudinales representan un sistema apropiado para evaluar si existe una relación general entre los patrones de riqueza, variables ambientales, y los procesos ecológicos que determinan cuantas especies co-ocurren en un área dada.En cuanto a los peces de agua dulce en arroyos de montaña la relación prevalente es un decrecimiento monotónico en riqueza de especies con la altura. El objetivo de este estudio es evaluar cuatro hipótesis que pueden explicar la relación negativa entre la riqueza local de especies de peces y la altura, 1) hipótesis de la disminución de la energía disponible 2) hipótesis del aumento del rigor climático 3) hipótesis de la diversidad de hábitats e 4) hipótesis de la severidad de las condiciones físicas del hábitat que se presentan río arriba, relacionada a las dificultades para colonizar las partes altas de los ríos. Se recolectaron peces y macro-invertebrados en 83 sitios entre 200 a 4 000 m en dos cuencas en la Amazonía boliviana. La primera hipótesis fue evaluada mediante regresiones entre la densidad de macro-invertebrados, los peces invertívoros y la altura. Para evaluar la segunda y tercera hipótesis se realizó un análisis de regresión múltiple (GLM), entre la riqueza y varios factores locales y regionales. Se analizó también la disimilitud de los ensamblajes de peces sobre el gradiente altitudinal utilizando los índices βsim y βnes. Se encontró que la riqueza de peces disminuye de manera lineal con el aumento de la altura. La densidad de macroinvertebrados aumenta con la altura, contrariamente a la riqueza de peces invertívoros, sugiriendo que la energía no constituye un factor limitante para la colonización de las especies de peces en zonas altas. El GLM explicó un 86 % de la variación total de la riqueza, con un aporte significativo de la temperatura del agua, las pendientes máximas en el río principal y el ancho de río. El βsim presentó valores altos en niveles de altura bajos, mostrando mayor recambio de especies entre los sitios cercanos a la fuente de colonización. Inversamente, el βnes mostró valores mayores en las partes altas, correspondientes a cambios por pérdida de especies. Estos resultados sugieren que el rigor climático junto con la severidad física del hábitat crean barreras a la colonización y explican los cambios de riqueza en el gradiente altitudinal.

AbstractAltitudinal gradients represent an appropriate system to assess whether there is a relationship between richness patterns, environmental variables, and the ecological processes that determine the species type and number inhabiting a given area. In mountain streams freshwater fishes, the most prevalent relationship is a monotonic decrease in species richness with elevation. The objective of this study was to evaluate four hypotheses that can explain the negative relationship between local fish species richness and altitude, 1) the hypothesis of decreasing energy availability, 2) the hypothesis of increasing climate severity, 3) the hypothesis of habitat diversity, and 4) the hypothesis of isolation by physical severity of the environment. Fish and macro-invertebrates were collected following standard methods from 83 sites (between 200-4 000 meters) of two river basins in the Bolivian Amazon. The first hypothesis was tested by analyzing relationships between the density of macro-invertebrates, the richness of invertivorous fish species and altitude; while the second and third hypotheses were assessed by a multiple regression analysis (GLM) between fish species richness and several local and regional factors. Besides, assemblage dissimilarity between sites along the altitudinal gradient was analyzed using βsim and βness indices. Fish richness decreases linearly with increasing altitude. The density of macro-invertebrates tends to increase at higher altitudes, contrary to invertivorous fish species richness, suggesting that energy availability is not a limiting factor for fish species colonization. The GLM explained 86 % of the variation in fish species richness, with a significant contribution of water temperature, maximum slope in the river mainstem, and stream width. There is a higher species turnover (βsim) between sites at low elevation. Inversely, βness shows higher values in the upper parts, corresponding to change in assemblages mainly due to species loss. Taken together, these results suggest that climatic and physical severities create strong barriers to colonization, further explaining the decrease in fish richness along the altitudinal gradient.

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Altitudinal gradients represent an appropriate system to assess whether there is a relationship between richness patterns, environmental variables, and the ecological processes that determine the species type and number inhabiting a given area. In mountain streams freshwater fishes, the most prevalent relationship is a monotonic decrease in species richness with elevation. The objective of this study was to evaluate four hypotheses that can explain the negative relationship between local fish species richness and altitude, 1) the hypothesis of decreasing energy availability, 2) the hypothesis of increasing climate severity, 3) the hypothesis of habitat diversity, and 4) the hypothesis of isolation by physical severity of the environment. Fish and macro-invertebrates were collected following standard methods from 83 sites (between 200-4 000 meters) of two river basins in the Bolivian Amazon. The first hypothesis was tested by analyzing relationships between the density of macro-invertebrates, the richness of invertivorous fish species and altitude; while the second and third hypotheses were assessed by a multiple regression analysis (GLM) between fish species richness and several local and regional factors. Besides, assemblage dissimilarity between sites along the altitudinal gradient was analyzed using ßsim and ßness indices. Fish richness decreases linearly with increasing altitude. The density of macro-invertebrates tends to increase at higher altitudes, contrary to invertivorous fish species richness, suggesting that energy availability is not a limiting factor for fish species colonization. The GLM explained 86 % of the variation in fish species richness, with a significant contribution of water temperature, maximum slope in the river mainstem, and stream width. There is a higher species turnover (ßsim) between sites at low elevation. Inversely, ßness shows higher values in the upper parts, corresponding to change in assemblages mainly due to species loss. Taken together, these results suggest that climatic and physical severities create strong barriers to colonization, further explaining the decrease in fish richness along the altitudinal gradient.

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Aerial insectivorous bats represent almost half of the bat diversity in the Neotropics. They use mainly echolocation (active or passive) to find their prey and contribute to pest control and herbivory reduction. We assessed the structure of the community of aerial insectivorous bats in four microhabitats (upper and lower forest edge, and upper and lower open space) through acoustic sampling in shoreline areas of Barro Colorado Nature Monument, Panama. Seven sites were chosen for sampling, each was visited four times, and bat recordings were taken during four consecutive hours per site each time. We found differences among species in foraging microhabitat, and a tendency of some species to be associated with particular microhabitats. During search calls, species that preferred forest edges (e.g., Saccopteryx bilineata) produced high frequency echolocation calls of short duration, short pulse intervals, and a combination of components of frequency modulation (FM) and quasi-constant frequency (QCF). On the other hand, species that preferred open spaces (e.g., Diclidurus albus) produced echolocation calls with low frequency, long duration, long pulse intervals, and QCF combined with FM components. Differences between guilds are explained by foraging strategy, and some bats prefer the upper stratum while others the lower stratum. This result provides important information on resource partitioning in aerial insectivorous bat communities, as well as on the importance of having a standard protocol to improve the use of acoustic monitoring.

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Aerial insectivorous bats represent almost half of the bat diversity in the Neotropics. They use mainly echolocation (active or passive) to find their prey and contribute to pest control and herbivory reduction. We assessed the structure of the community of aerial insectivorous bats in four microhabitats (upper and lower forest edge, and upper and lower open space) through acoustic sampling in shoreline areas of Barro Colorado Nature Monument, Panama. Seven sites were chosen for sampling, each was visited four times, and bat recordings were taken during four consecutive hours per site each time. We found differences among species in foraging microhabitat, and a tendency of some species to be associated with particular microhabitats. During search calls, species that preferred forest edges (e.g., Saccopteryx bilineata) produced high frequency echolocation calls of short duration, short pulse intervals, and a combination of components of frequency modulation (FM) and quasi-constant frequency (QCF). On the other hand, species that preferred open spaces (e.g., Diclidurus albus) produced echolocation calls with low frequency, long duration, long pulse intervals, and QCF combined with FM components. Differences between guilds are explained by foraging strategy, and some bats prefer the upper stratum while others the lower stratum. This result provides important information on resource partitioning in aerial insectivorous bat communities, as well as on the importance of having a standard protocol to improve the use of acoustic monitoring.(AU)

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Productivity (trophic energy) is one of the most important factors promoting variation in species richness. A variety of species-energy relationships have been reported, including monotonically positive, monotonically negative, or unimodal (i.e. hump-shaped). The exact form of the relationship seems to depend, among other things, on the spatial scale involved. However, the mechanisms behind these patterns are still largely unresolved, although many hypotheses have been suggested. Here we report a case of local-scale positive species-energy relationship. Using 14 local fish assemblages in tropical forested headwater streams (Bolivia), and after controlling for major local abiotic factors usually acting on assemblage richness and structure, we show that rising energy availability through leaf litter decomposition rates allows trophically specialized species to maintain viable populations and thereby to increase assemblage species richness. By deriving predictions from three popular mechanistic explanations, i.e. the 'increased population size', the 'consumer pressure', and the 'specialization' hypotheses, our data provide only equivocal support for the latter.

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Breast cancer is one of the most frequent neoplasms in women. New drugs, including taxanes, have improved survival in patients with metastatic disease. Quality of life and efficacy are important goals during treatment of these women. Herein, we report a 51 year-old woman with metastatic breast cancer who developed gastrointestinal pneumatosis (GIP) after the first cycle of treatment, which consisted of docetaxel and pamidronate. The symptoms disappeared after 7 days with supportive management, nasogastric intubation, parenteral fluids, and wide-spectrum antibiotics. Thereafter, weekly fractionated chemotherapy with an initial 50% dose reduction was administered. Because of adequate tolerance, the dose was increased by 25% after the second cycle, and full-dose docetaxel was administered after the third cycle. After 6 months of follow-up, the patient remained under treatment, with an Eastern Cooperative Oncology Group performance status of 1. Gastrointestinal pneumatosis has been reported in association with chemotherapy. In most patients, it is reported to be associated with neutropenia, which was not present in this patient.

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