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Despite their limited vagility and pronounced habitat heterogeneity in the tropics, many anuran species have unexpectedly extensive geographic ranges. One prominent example of this phenomenon is Pithecopus hypochondrialis, which is found in the Cerrado, Guianan savanna, and Llanos domains, as well as isolated tracts of savanna and open habitat within the Amazon Forest. The present study employs an integrative species delimitation approach to test the hypothesis that P. hypochondrialis is in fact a species complex. We also reconstruct the relationships among the lineages delimited here and other Pithecopus species. In this study, we employ Ecological Niche Modelling (ENM) and spatiotemporal phylogeographic reconstruction approaches to evaluate a multitude of scenarios of connectivity across the Neotropical savannas. We identified three divergent lineages, two of which have been described previously. The lineages were allocated to a lowland Pithecopus clade, although the relationships among these lineages are weakly supported. Both the ENM and the phylogeographic reconstruction highlight the occurrence of periods of connectivity among the Neotropical savannas over the course of the Pliocene and Pleistocene epochs. These processes extended from eastern Amazonia to the northern coast of Brazil. The findings of the present study highlight the presence of hidden diversity within P. hypochondrialis, and reinforce the need for a comprehensive taxonomic review. These findings also indicate intricate and highly dynamic patterns of connectivity across the Neotropical savannas that date back to the Pliocene.

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RESUMEN Introducción: el Dr. Mario E. Dihigo Llanos, junto a un grupo de colegas emprendedores, fundó en Matanzas, en 1921, la revista Médica (devenida Revista Médica Electrónica en 1997). Objetivos: resaltar el centenario de la publicación y contribuir a la preservación de la memoria del eximio pedagogo. Materiales y métodos: fueron utilizados métodos de la investigación histórica, como el analítico-sintético y el deductivo-inductivo, así como los submétodos cronológico y geográfico. Se realizaron entrevistas y se revisó el legado documental del Dr. Dihigo. La información fue triangulada con las fuentes referenciadas y con otras bibliografías y documentos consultados. Resultados: se resaltaron algunos de los aspectos más significativos relacionados con la vida y la obra del Dr. Dihigo, y se realizó una caracterización de las primeras etapas de la revista, donde se abordan su significación histórica y científica. Conclusiones: sus aportes en Medicina y Pedagogía, así como sus esfuerzos por establecer la revista Médica, son los mayores legados de Dihigo (AU).

ABSTRACT Introduction: Dr. Mario E. Dihigo Llanos, and a group of colleagues-enterprisers, founded the journal Medica (renamed Revista Medica Electronica in 1997) in Matanzas, in 1921. Objectives: to highlight the centenary of the journal and to contribute to keep the memory of the prominent pedagogue up. Materials and methods: methods of the historical research were used like the analytic-synthetic and the deductive-inductive ones, and also the chronological and geographic sub-methods. Interviews were made and the documental legacy of Dr. Mario Dihigo was reviewed. The information was compared with the referenced sources and the other referred bibliography and documents. Results: some of the most significant features of Dr. Dihigo's life and work were emphasized. A characterization of the first stages of the journal was carried out, approaching its historical and scientific significance. Conclusions: the main Dihigo's legacies were his contributions to Medicine and Pedagogy, and his efforts for founding the journal Medica (AU).

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Esta investigación tiene como principal propósito analizar la probabilidad de deserción temprana de los estudiantes de la Universidad de los Llanos mediante un modelo de regresión logística. Además, identificar cuáles son las variables de mayor incidencia en la deserción temprana. Para la construcción del modelo se tomó como muestra la información de 574 estudiantes que ingresaron en la cohorte 2015-2 y que para el periodo 2018-1 eran registrados como vigentes o reportaban como último periodo matriculado cualquiera de los cuatro primeros semestres. Los resultados dan cuenta de que un buen puntaje en la prueba Saber 11, el ser mujer, no haber reprobado años durante el bachillerato, el haber cursado estudios antes y si los padres conviven, disminuye la probabilidad de deserción; así mismo, el haber egresado de un colegio privado aumenta esta probabilidad. De todas las facultades en las que se puede matricular el estudiante, las que mayor riesgo tienen de deserción temprana son la de Ciencias Básicas e Ingeniería y la Facultad de Ciencias de la Salud.

The main purpose of this study is to analyze the early dropout probability in the University of Los Llanos students using a logistic regression model and to identify which are the variables with a higher incidence value. To build the model, data were taken from 574 students who had been admitted in the 2015 second semester and were registered as active or whose last semester was one of the last four. As result, the dropout factor decreases if the student had a high score in Saber 11 test, is a woman, had not to fail any school year, had taken some courses before and his parents are alive and increase if the student comes from a private school. The faculties with the high dropout index are Basic Sciences and Engineering, and Health Sciences.

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A major goal in ecology is to understand mechanisms that influence patterns of biodiversity and community assembly at various spatial and temporal scales. Understanding how community composition is created and maintained also is critical for natural resource management and biological conservation. In this study, we investigated environmental and spatial factors influencing beta diversity of local fish assemblages along the longitudinal gradient of a nearly pristine Neotropical river in the Colombian Llanos. Standardized surveys were conducted during the low-water season at 34 sites within the Bita River Basin. Physical, chemical, and landscape parameters were recorded at each site, and asymmetric eigenvector maps were used as spatial variables. To examine the relative influence of dispersal and environmental variables on beta diversity and its components, distance-based redundancy analysis (db-RDA) and variation partitioning analysis were conducted. We proposed that spatial scale of analysis and position within the river network would constrain patterns of beta diversity in different ways. However, results indicated that in this system, high beta diversity was consistent among species assemblages no matter the scale of analysis or position within the river network. Species replacement (turnover) dominated beta diversity, an indication of the importance of species sorting. These findings suggested that conservation of fish diversity in tropical rivers requires maintenance of both habitat heterogeneity (spatial variation in habitat conditions) and connectivity at the scale of entire river basins.

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Many studies have addressed the potential of low-input agroecosystems for biological conservation. However, most have been carried out on annual agroecosystems in temperate, developed countries. As agricultural surface will increase and natural protected areas alone will not warrant the conservation of biodiversity, it is crucial to include different types of agroecosystems in research and conservation efforts. In Mexico, perennial, low-input, fruit-oriented nopal orchards (Opuntia spp.), one of the few crops suitable for semiarid areas, are the 10th out of 61 most important fruit crops grown in the country. We assessed their value for conservation in an anthropized landscape by comparing their rodent assemblages with those in adjacent habitats and determined the influence of the latter on the rodent communities inside them. We live-trapped rodents in 12 orchards and adjacent natural xeric shrubland, grassland, and cropland. We captured 19 different species, of which 17 used the orchards. Four are Mexican endemics. Orchards have higher α diversity, species richness, and abundance than cropland and grassland and are not different from shrubland. The dominant rodent species are the same in orchards and shrubland, and where these two meet they integrate into one habitat. Within-habitat quality is a critical driver of the composition and diversity of rodent communities in the orchards studied, and the neighboring habitats do not modify them substantially. Increasing within-patch heterogeneity beyond a certain level is at the expense of habitat integrity and produces small-scale fragmentation reducing habitat quality. At a landscape scale, orchards contribute importantly to regional rodent diversity compared with other land use types, and appear to increase habitat connectivity between patches of shrubland. Orchards' higher α diversity would give them higher ecological resilience and make them better suited than grassland and cropland to contribute to the conservation of local biota. Nopal orchards should be considered conservation allies and incorporated in regional conservation plans. Regrettably, their future is unwarranted as producers face low revenues and lack of governmental support. Our confirmation that orchards have an important, positive impact on biodiversity can be used as a strong argument to lobby for incentives to safeguard this environmental friendly, low-input agroecosystem.

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The Cusiana River sub-basin has been identified as a priority conservation area in the Orinoco region in Colombia due to its high species diversity. This study presents an updated checklist and identification key for fishes of the Cusiana River sub-basin. The checklist was assembled through direct examination of specimens deposited in the main Colombian ichthyological collections. A total of 2020 lots from 167 different localities from the Cusiana River sub-basin were examined and ranged from 153 to 2970 m in elevation. The highest number of records were from the piedmont region (1091, 54.0 %), followed by the Llanos (878, 43.5 %) and Andean (51, 2.5 %). 241 species distributed in 9 orders, 40 families, and 158 genera were found. The fish species richness observed (241), represents 77.7 % of the 314 estimated species (95 % CI=276.1-394.8). The use of databases to develop lists of fish species is not entirely reliable; therefore taxonomic verification of specimens in collections is essential. The results will facilitate comparisons with other sub-basins of the Orinoquia, which are not categorized as areas of importance for conservation in Colombia.

ResumenLa sub-cuenca del rio Cusiana ha sido designada como una de las áreas prioritarias para la conservación en la región del Orinoco en Colombia debido a su alta diversidad de especies. Este estudio presenta una lista actualizada y una clave de identificación para los peces del área. Para ello se revisaron los especímenes depositados en las principales colecciones ictiológicas colombianas. Se examinaron un total de 2020 lotes de 167 localidades diferentes de la sub-cuenca del río Cusiana, que oscilaron entre 153 y 2970 m en altitud. El mayor número de registros corresponde a la región del piedemonte (1091, 54.0%), seguida por los Llanos (878, 43.5%) y Andina (51, 2.5%). Encontramos 241 especies distribuidas en 9 órdenes, 40 familias y 158 géneros. La riqueza de especies de peces observada (241), representan el 77.7% de las 314 especies estimadas (IC 95% = 276.1-394.8). El uso de bases de datos para elaborar listas de especies de peces no es del todo fiable, por lo tanto, es esencial la verificación taxonómica de los especímenes en las colecciones. Estos resultados permitirán evaluar otras sub-cuencas de la Orinoquia, las cuales no están categorizadas como áreas de importancia para la conservación en Colombia.

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RESUMEN El departamento del Meta cuenta con un elevado potencial hidrológico que se traduce en oportunidades para los sectores agrícola, pecuario y ambiental. Por otra parte, se han incrementado considerablemente las actividades de la industria petrolera, lo cual ha traído nuevos retos y amenazas a la región. En consecuencia, los ríos del departamento se ven afectados por vertimientos de diferentes tipos, por captaciones y por modificaciones de los entornos de ribera y de los ambientes bentónicos. Sin embargo, es poco lo que se conoce acerca de estos sistemas y de las comunidades de microalgas y macroinvertebrados que los habitan, las cuales cumplen un papel fundamental en el funcionamiento ecológico de los ríos. Por esta razón se analizan las características más relevantes de dichas comunidades y se discuten las modificaciones que las actividades humanas provocan sobre la estabilidad ecológica de los ríos en un contexto regional. Adicionalmente, se presenta un listado de los taxones de microalgas perifíticas y macroinvertebrados bentónicos registrados para el departamento del Meta.

ABSTRACT Nowadays the Meta Department has a high hydrological potential, which results in an opportunity for agriculture and livestock. Moreover, activities of the oil industry have significantly increased, which have brought new challenges and threats to the region. Consequently, different types of discharges and environment modifications affect the Meta Region's rivers in their watersheds and their riparian and benthic communities. However, these systems are poorly understood, including the periphyton and macroinvertebrate communities that inhabit them. In this paper, we provide a review of the most relevant characteristics of these communities, and we discuss the changes caused by human activities on the ecological stability of the rivers in a regional context. Additionally, we presented a list of periphytic algae and benthic macroinvertebrates taxa registered in the Meta Region.

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Resumen La variabilidad climática es un tema de importancia para el desarrollo de actividades agropecuarias. En la descripción de las tendencias del comportamiento del clima, es necesario establecer referentes de consulta, los cuales puedan respaldar pronósticos y análisis de los datos. En Colombia existen zonas donde no se cuenta con equipos para la medición de estos parámetros, debido a que requieren una inversión significativa y capacitación técnica para el manejo y mantenimiento de los equipos. Una posible solución es establecer modelos que permitan visualizar la tendencia de estos datos. Esta investigación se desarrolló en la región del Casanare, ubicada en los llanos orientales de Colombia. Esta zona se caracteriza por la producción ganadera, así como de arroz, plátano y yuca. En el presente estudio se desarrolló el análisis de las tendencias de datos climatológicos, según la base de datos del periodo 2012-2015, de una estación climatológica tipo Davis Weather Station. Los datos analizados fueron temperatura ambiente (°C), humedad relativa (%), radiación solar (W/m-2) y velocidad del viento (m/s-1). Se evaluó la tendencia de estos parámetros anualmente, y se hallaron los coeficientes de determinación (r2) según los modelos de ajuste empleados.

Abstract Climatic variability is an important issue for the development of agricultural activities. In the description of climate trends, it is necessary to establish models for consultation, which can support forecasts and data analysis. In Colombia, in certain areas there are no available equipment to measure these parameters, because significant investment and technical training is required for their management and maintenance. One possible solution is to establish models that allow visualizing data trends. This research was developed in the region of Casanare, located on the eastern plains of Colombia. This area is characterized by the production of livestock, as well as rice, banana, and cassava. The present study analyzed climatological data trends, using the database of the period 20122015 of a Davis Weather Station-type weather station. The data analyzed were ambient temperature (°C), relative humidity (%), solar radiation (W/m-2), and wind speed (m/s-1). The trend of these parameters was evaluated annually, and determination coefficients (r2) were calculated according to the adjustment models used.

Resumo A variabilidade climática é um tema de importância para o desenvolvimento de atividades agropecuárias. Na descrição das tendências do comportamento do clima, é necessário estabelecer referências de consulta, as quais possam apoiar os prognósticos e análises dos dados. Na Colômbia existem zonas onde não se conta com equipamentos para a medição destes parâmetros, devido ao fato de que requerem um investimento significativo e capacitação técnica para o manejo e manutenção dos equipamentos. Uma possível solução é estabelecer modelos que permitam visualizar a tendência destes dados. Esta pesquisa foi desenvolvida na região de Casanare, situada nas planícies orientais da Colômbia. Esta zona se caracteriza pela produção de gado, assim como também de arroz, banana e mandioca. Neste estudo se desenvolveu a análise das tendências de dados climatológicos, segundo a base de dados do período 2012-2015, de uma estação climatológica tipo Davis Weather Station. Os dados analisados foram temperatura ambiente (°C), umidade relativa (%), radiação solar (W/m-2) e velocidade do vento (m/s-1). Avaliou-se a tendência destes parâmetros anualmente, e foram encontrados os coeficientes de determinação (r2) segundo os modelos de ajuste empregados.

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Tres meses, antes del gran descubrimiento de los rayos que marcarían el nacimiento de la Radiología, y en pleno estremecimiento nacional independentista, nació el Dr. Mario Emilio Dihigo Llanos, en Cidra, Matanzas, en 1895. Profesional multifacético: médico, radiólogo, escritor, periodista, pedagogo y fundador de la revista Médica, fue reconocido como educador destacado del siglo XX en Cuba e incluido entre las cien figuras científicas cubanas de todos los tiempos. Estudió entre 1912 y 1917 en la Escuela de Medicina de la Universidad de La Habana, de modo que conoció y fue alumno de varias de las más excelsas figuras de la ciencia cubana. En ocasión del ciento veinte aniversario de su nacimiento y del surgimiento de la Radiología, y a través de artículos recogidos en su autobiografía, el autor abordó otra visión, más humana, de la personalidad del Dr. Francisco Domínguez Roldán: médico, patriota, coronel del Ejército Libertador, defensor de la doctrina finlaísta e introductor de la Radiología en Cuba. Se analizaron algunas notas biográficas de ambas figuras. El trabajo pretendió reconocer a todos los que han dedicado, o han decidido dedicar su vida a la ciencia de las Radiaciones e Imágenes(AU)

Three months before the great discovery of the rays that marked the birth of Radiology, and in full force of the national independent quiver, Dr Mario Emilio Dihigo Llanos was born in Cidra, Matanzas, in 1895. Multifaceted professional: physician, radiologist, writer, journalist, pedagogue and founder of the journal Mdica, he was recognized as outstanding educator of the 20 century in Cuba and among the 100 Cuban scientific personalities of all the times. Between 1912 and 1917 he studied in the Medicine School of the University of Havana, therefore he met and was the pupil of several of the most distinguished figures of the Cuban science. In occasion of the 120 anniversary of his birth and of the emergence of Radiology, and through articles gathered in his autobiography, the author approached another, more human view of Dr. Francisco Dominguez Roldans personality: physician, patriot and Colonel of the Liberator Army, defender of the Carlos J. Finlays doctrine and introducer of Radiology in Cuba. We analyzed several biographic notes of both of the figures. The work pretended to recognize all the persons who had devoted, or have decided to devote their life to the science of Radiology and Imaging(AU)

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En 2014 se cumplieron 129 años del nacimiento del Dr. Mario Emilio Dihigo Llanos (1895-1976), reconocido médico y profesor. Con el objetivo de rendirle un merecido homenaje, se realizó este trabajo. Se abordaron aspectos de su vida y obra, resaltándose sus valores y las aristas más destacadas de su formación y desempeño. Se hace referencia a otros médicos que han sido glorias de la ciencia matancera y cuyas obras fueron contemporáneas(AU)

In 2014, 129 years were commemorated from the birth of Dr Mario Emilio Dihigo Llanos (1895-1976), renowned physician and professor. With the aim of rendering him a deserved homage, we carried out this work. We dealt with aspects of his life and work, highlighting his values and the most important facets of his formation and performance. We made reference to other physicians who have been glories of Matanzas sciences and whose activities were contemporary(AU)

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Roads directly or indirectly affect the structure, dynamics and function of ecosystems that they traverse. Most studies on the effect of roads on wildlife focus on the evaluation of mortality of vertebrates by vehicle collisions. Despite the extensive road network that exists in Venezuela, studies of wildlife mortality in them are scarce. In this paper, we analyzed the temporal and spatial pattern of vertebrate’s collisions along the road Guanare-Guanarito, in Portuguesa state. We travelled 26 times between these towns (74km) to localize dead vertebrates, at a speed of 50-60km/h. of those trips were conducted from March 13 to October 26, 2010, and 10 additional trips from December 7, 2009 to December 14, 2010; these ones, with the aim to include months and seasons that were insufficiently sampled during the first period. The elapsed time between trips varied from 14 to 37 days. The total distance traveled was 1 924km. Dead animals found amounted 464 individuals, 66 of them were birds (25 identified species), 130 mammals (15 species) and 268 reptiles (18 species). The species with the highest number of individuals were the snake Leptodeira annulata (n=119), the oppossum Didelphis marsupialis (n=39) and the spectacled caiman Caiman crocodilus (n=33). Excluding domestic animals, the rate of road-killed vertebrates was 0.2282indiv./km, a figure 28.3% higher than previous studies in the same road. Changes in the relative number of collisions for some species, respect to the numbers reported 20 years ago, were linked to the increase in traffic flow and changes in land use. Road segments with collision rates higher than expected by chance were identified. Collition by cars may be the principal cause of mortality for species like the tamandua (Tamandua tetradactyla) and the giant anteater (Myrmecophaga tridactyla), the last considered a vulnerable species. Some basic measures are proposed to reduce wildlife mortality on the road.

Uno de los aspectos más investigados en relación a la “ecología de la carretera” es el atropellamiento de vertebrados silvestres. Se evaluó la distribución espacial y temporal de los atropellos de vertebrados en la carretera Guanare-Guanarito, estado Portuguesa, Venezuela. Desde 2008 hasta el 2010 se realizaron 26 viajes en carro a lo largo de 74km, a 50-60km/h, para un total recorrido de 1 924km. Se encontraron 464 animales muertos: 66 aves (25 especies), 130 mamíferos (15 especies) y 268 reptiles (18 especies). La serpiente Leptodeira annulata (n=119), el rabipelado Didelphis marsupialis (n=39) y la baba Caiman crocodilus (n=33) fueron las especies con mayor frecuencia de atropellos. Excluyendo a los animales domésticos, se localizaron 0.2282indviv./km; cifra 28.30% mayor que la reportada en estudios previos en la misma vía. Los cambios en la frecuencia relativa de atropellos de algunas especies con respecto a los reportados hace 20 años, se relacionan con el incremento en el flujo vehicular y por modificaciones en el uso de la tierra. Se identificaron segmentos donde el número de individuos atropellados supera al esperado por azar. Los atropellos pudieran ser la principal causa de mortalidad para especies como el oso melero (Tamandua tetradactyla) y el oso hormiguero (Myrmecophaga tridactyla), esta última considerada como una especie vulnerable. Se recomiendan algunas medidas básicas para disminuir la mortalidad de fauna en la carretera.

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El objetivo de este artículo fue analizar datos meteorológicos para identificar el comportamiento de variables físicas de relevancia y definir el clima de la región y el microclima de Yopal, Casanare. Se estudiaron los registros de las variables climáticas en una serie de tiempo de treinta años en la estación meteorológica del aeropuerto de Yopal, los cuales fueron suministrados por el Instituto de Estudios Ambientales y Meteorológicos (Ideam). Luego se llevó a cabo una tipificación climática basada en las clasificaciones más utilizadas por la comunidad científica, como son Thornthwaite, De Martone y Koppen, con el propósito de situar climáticamente la región de estudio. Por último, se analizaron las dos variables físicas más importantes en cuanto al comportamiento del microclima del lugar respecto al crecimiento de la vegetación, por sus procesos de evapotranspiración y uso del recurso hídrico.

The purpose of this article was to analyze meteorological data to identify the behavior of relevant physical variables and to define the regional climate and microclimate of Yopal, Casanare. The records of climatic variables in a time period of thirty years at the Yopal airport weather station, supplied by the Institute of Environmental and Meteorological Studies (Ideam), were studied. Then, a climatic classification was performed, based on the most used classifications by the scientific community, such as Thornthwaite, De Martone and Koppen, in order to climatically locate the region under study. Finally, the two most important physical variables were analyzed, in terms of behavior of the microclimate of the site regarding the growth of vegetation, by its processes of evapotranspiration and water use.

O objetivo deste artigo foi analisar dados meteorológicos para identificar o comportamento de variáveis físicas de relevância e definir o clima da região e o microclima de Yopal, Casanare. Estudaram-se os registros das variáveis climáticas em uma série de tempo de trinta anos na estação meteorológica do aeroporto de Yopal, os quais foram fornecidos pelo Instituto de Estudos Ambientais e Meteorológicos (Ideam). Depois foi realizada uma tipificação climática baseada nas classificações mais utilizadas pela comunidade científica, como é Thornthwaite, De Martone e Koppen, com o propósito de situar climaticamente a região de estudo. Por último, analisaram-se as duas variáveis físicas mais importantes, em quanto ao comportamento do microclima do lugar com relação ao crescimento da vegetação, por seus processos de evapotranspiração e uso do recurso hídrico.

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El siguiente artículo es un informe de investigación que da cuenta del planteamiento de unaEtnografía realizada en la región colombiana de los llanos del Yarí. El eje central de la investigación giró en torno al proceso de construcción territorial que han desplegado las comunidades campesinas de la zona.

The following article is a research report that realizes of the exposition of an ethnography realized in the plains of the Yari - Colombia. The backbone of the investigation turned concerning the process of territorial construction that the communities have opened compesinas of the zone.

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Genetic structure of a group of capybaras, Hydrochoerus hydrochaeris (Rodentia: Hydrocheridae) in the Colombian Eastern Llanos. The capybaras are the biggest rodents in the world but, however, there are not extensive population genetics studies on them. In the current work, we studied the genetic structure of a troop of 31 capybaras (Hydrochoerus hydrochaeris) sampled in Hato Corozal, Casanare Department at the Colombian Eastern Llanos, by means of five microsatellite markers. The gene diversity was 0.61 and the average allele number was 5.2, which is a medium-low level for markers of this nature. Out five markers employed, three were in Hardy-Weinberg equilibrium meanwhile one showed a significant homozygote excess and other presented a significant heterozygote excess. There were not significant genetic differences between males and females inside this troop. The application of different procedures to determine possible historical demographic changes (population expansions or bottlenecks) clearly showed that the population analyzed crossed over a very narrow recent bottleneck. The illegal hunt is the possibly cause of this strong genetic bottleneck. Rev. Biol. Trop. 59 (4): 1777-1793. Epub 2011 December 01.

Los capibaras son los roedores más grandes del mundo, sin embargo, no se han realizado estudios genético poblacionales exhaustivos con ellos. En el presente trabajo se analizó la estructura genética de una manada de 31 capibaras (Hydrochoerus hydrochaeris) muestreada en Hato Corozal, Departamento de Casanare en los Llanos Orientales de Colombia, mediante cinco marcadores microsatelitales. La diversidad genética se determinó en 0.61 y un número promedio de alelos de 5.2, lo cual se puede considerar medio-bajo para este tipo de marcadores. De los cinco marcadores empleados, tres mostraron proporciones genotípicas en concordancia con lo esperado en equilibrio Hardy-Weinberg, mientras que un marcador mostró un exceso significativo de homocigotos y otro un exceso significativo de heterocigotos. No se encontraron diferencias significativas para esos cinco marcadores entre machos y hembras de la manada muestreada. La aplicación de diferentes procedimientos para detectar posibles cambios demográficos históricos (expansiones poblacionales o cuellos de botella) mostró claramente que la población analizada ha pasado por un cuello de botella extremadamente fuerte en épocas recientes. La limitada variabilidad genética encontrada y la fuerte evidencia de que la manada estudiada ha pasado por un cuello de botella reciente es probablemente el resultado de la cacería ilegal.

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A palynological analysis of an organic paleosol found at 150-125 cm depth in a Mauritia swamp from the Eastern Orinoco Llanos is presented. The 25 cm pollen record summarizes the vegetation history during the Early Holocene, from 10,225 to 7,800 calendar yr BP. The vegetation was characterized by a Poaceae marsh, where Asteraceae, Melastomataceae, Schefflera-type and Phyllanthus were the most abundant shrubs and trees. Pollen-types richness was lower than that recorded today in similar environments, and Mauritia pollen was absent. Results suggest that climate was as humid as present during the beginning of the Holocene, with a decreasing trend in humidity from around 8,000-7,000 yr BP, in coincidence with the beginning of the "Early-Mid-Holocene Dryness" that affected deeply the Amazon Basin and neighboring areas. Dry climatic conditions could have existed in the study site until the Mid-Late Holocene when a Mauritia swamp developed, and humid conditions similar to present established. Main climate phases inferred in our study site fit well with regional trends recorded in other places located north Amazon Basin. However, conclusions are still limited by the lack of additional Quaternary records in the Orinoco Llanos area, avoiding regional correlations.

Realizou-se uma análise de pólen amostrada em paleossolos orgânicos, entre 150-125 cm de profundidade, em um pântano Mauritia os lhanos do Orinoco. O registro de pólen dessa amostra resumiu a história da vegetação durante o Holoceno Temprano, entre 10,225-7,800 cal. anos AP. A vegetação durante esse período foi caracterizada por um pântano de Poaceae, com maior abundância de arbustos e árvores de Asteraceae, Melastomataceae, tipo-Schefflera e Phyllanthus. Encontrou-se que a riqueza de tipos polínicos no Holoceno Temprano foi menor do que a riqueza atualmente encontrada em ambientes similares; o pólen de Mauritia esteve ausente de todas as amostras. Os resultados deste estudo sugerem que o clima durante o início do Holoceno foi úmido, semelhante ao clima atual. Houve também uma tendência de diminuição de umidade entre 8,000-7,000 anos AP, o que coincidiu com o início da "seca do Holoceno Temprano-Médio". Esta seca afetou profundamente a Bacia Amazônica e áreas adjacentes, persistindo no local de estudo até o Holoceno Médio-Final, período em que surgiram o pântano Mauritia e as condições climáticas atuais. Fases climáticas principais deduzidas se encaixam bem com as tendências regionais registradas em outros lugares localizados ao norte da Bacia Amazônica. No entanto, as conclusões ainda são limitadas pela falta de novos registros quaternários na área lhanos do Orinoco, evitando correlações regionais.

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Feeding behavior and habitat use of two species of pike cichlids, or mataguaros, (Crenicichla lugubris and C. aff. wallacii) were studied in the río Cinaruco, a floodplain river in the Venezuelan llanos. We examined 309 individuals of C. lugubris and 270 individuals of C. aff. wallacii from both the main channel and lagoons throughout the falling-water phase of the annual hydrological cycle. Crenicichla lugubris was common within habitats that contained rocks or woody debris, whereas C. aff. wallacii was more abundant in lagoons than the main channel, especially within shallow areas containing leaf litter. Although we did not capture C. aff. wallacii in rocky shoals, they sometimes were observed in these habitats. Crenicichla lugubris was larger than C. aff. wallacii (198.4 mm and 44.6 mm, respectively). Analysis of stomach contents showed that larger specimens (> 100 mm SL) C. lugubris fed mostly on small fishes (e. g. characids, cichlids), but juveniles (< 100 mm SL) consumed mostly aquatic insects, fish scales, and shrimps. Crenicichla aff. wallacii fed on aquatic insects and other invertebrates associated with leaf litter substrates.

O comportamento alimentar e o uso de habitat de duas espécies de "joanas", ou "mataguaros", (Crenicichla lugubris e C. aff. wallacii) foram estudados no río Cinaruco, uma planície de alagamento nos llanos Venezuelanos. Examinamos 309 indivíduos de C. lugubris e 270 de C. aff. wallacii do canal principal e lagoas ao longo da fase de vazante de um ciclo hidrológico anual. Crenicichla lugubris foi comum em ambientes que continham rochas, galhos e troncos, enquanto que C. aff. wallacii foi mais abundante em lagoas do que no canal principal, especialmente em áreas rasas contendo folhiço. Embora não tenhamos capturado C. aff. wallacii em cardumes em meio às rochas, em algumas ocasiões eles foram observados nestes ambientes. Crenicichla lugubris foi maior do que C. aff. wallacii (198,4 mm e 44,6 mm CP, respectivamente). Análise dos conteúdos estomacais de C. lugubris revelou que os indivíduos maiores (> 100 mm CP) se alimentaram principalmente de peixes pequenos (e. g. caracídeos e ciclídeos), e os menores (< 100 mm CP) consumiram principalmente larvas aquáticas de insetos, escamas de peixes e camarões. Crenicichla aff. wallacii se alimentou de insetos aquáticos e outros invertebrados associados ao folhiço.

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Effect of landscape change on the structure of the sting-less bee community (Hymenoptera: Apidae) in Meta, Colombia. Stingless bees represent one of the most diversified components of the natural Apoidea fauna of pollinators in the tropics. They use diverse kinds of substrates and inhabit varied habitats. Some species are typical for some natural either artificial place. The landscape alteration were this group of bees nests, has and important impact on the natural composition of its community structure, fact which is reflected in the nest density. We analyzed the structure composition of the stingless bees’ community in three environments in the Colombian llanos piedmont, an important region that represents the transition between Andean ecosystems and a savannah that is seriously threatened by cattle practices. We made systematic samples in secondary forest, agro-ecosystems and urban areas, recording the presence of 204 nests from 11 genera (24 species). The nest density per landscape was heterogeneous and never higher than 16 nests/Ha. We observed two nesting patterns and an effect of sampling criterion on the measured biodiversity. Rev. Biol. Trop. 56 (3): 1295-1308. Epub 2008 September 30.

Las abejas sin aguijón son unos de los polinizadores naturales más diversos de la fauna Apoidea en los trópicos. Nidifican en diversos sustratos y distintos ambientes, existiendo algunas especies típicas de lugares naturales o artificiales. La alteración del medio donde nidifican tiene un importante impacto sobre la composición natural de su estructura, hecho que se ve reflejado también en la densidad de nidos. Analizamos la composición de la estructura de la comunidad de abejas sin aguijón en tres paisajes del piedemonte llanero colombiano, una región importante por representar la transición entre ambientes andinos y de sabana (seriamente amenazada por la ganadería intensiva). Realizamos muestreos sistemáticos en bosque secundario, agro-ecosistema y zona urbana; registramos la presencia de 204 nidos de 11 géneros representados por 24 especies. La riqueza de abejas sin aguijón fue similar, aun cuando hubo diferencias significativas en la estructura de la comunidad en los tres paisajes. La densidad de nidos por paisaje fue heterogénea y nunca mayor de 16 nidos/Ha. Observamos dos patrones de nidificación y registramos diferente número de especies en la misma zona utilizando otro criterio de muestreo.

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Variation of the orchid bees community (Hymenoptera: Apidae) in three altered habitats of the Colombian "llano" piedmont. Orchid bees subsist in vast tropical forest areas because they maintain close relationships with particular plant species in diverse micro-habitats. Based on the relationships among the environment and biological features (food preference, morphologic and ethologic diversity), it is possible to determine habitat quality using the euglossine array. This work proposes the use of this ecological information, in addition to diversity indices, for the evaluation of environmental quality. Fifteen localities in three landscape types (urban, rural and conserved) were sampled in the eastern llanos foothill (Meta, Colombia), between March and December of 2003 using entomological nets, and Cineol and Metil Salicylate as baits. Of the 26 species known to occur in the area, 17 were registered. Eulaema nigrita was the most frequent, while E. speciosa E. bombiformis, Euglossa magnipes, E. cybelia, E. heterosticta, E. singularis and Exaerete frontalis were mostly found in habitats rated "good to acceptable". The vegetation composition and proximity of forest fragments seem to favor some species in disturbed habitats. Relative diversity of bee body shapes and sizes is proportional to habitat quality. Rev. Biol. Trop. 55 (3-4): 931-941. Epub 2007 December, 28.

Las abejas de las orquídeas subsisten en vastas áreas de bosque tropicales gracias a que mantienen estrechas relaciones con tipos de vegetación particular en diversos micro-hábitats. Con base en este tipo de relaciones con el medio y características biológicas como preferencia por ciertos tipos de néctares y de polen, y diversidad morfológica y etológica de la tribu, es posible evaluar la calidad de un hábitat según la distribución de euglosinos. Este trabajo propone el uso de esta información, además de índices de diversidad para la evaluación de la calidad del medio. Entre marzo y diciembre de 2003 muestreamos tres tipos de paisaje (Urbano, Rural y Conservado) en el piedemonte llanero colombiano, usando redes entomológicas y sustancias aromáticas (Cineol y Metil Salicilato). Para las 15 localidades muestreadas se registraron 17 de las 26 especies conocidas para el área. Eulaema nigrita fue la más frecuente mientras que Euglossa magnipes, E. cybelia, E. heterosticta, E. singularis, Eulaema bombiformis, E. speciosa y Exaerete frontalis correspondieron a ambientes considerados de aceptable a buena calidad. La composición y cercanía de fragmentos de bosque son factores favorables. La diversidad relativa (máxima variación de formas y tamaños dentro de la tribu), sería proporcional a la calidad del medio.

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The richness and abundance of aquatic plant communities were studied in 14 habitats of the Venezuelan "llanos" (07 degrees 35'-07 degrees 55' N-68 degrees 50'-69 degrees 00' W, Apure) during an annual cycle. Annual means were 27 degrees C, 115 mm rainfall and 77% relative humidity. A permanent transect was set in each habitat (ten consecutive square meter quadrats from the shore to the water). The plants and the area they covered in each quadrat were recorded monthly for a year. The total richness was 69 species. Alatalo and Alatalo's diversity analysis indicates that season, and its correlate, water level, influence species diversity and abundance more than habitat (spatial factor: geometric index-Euclidean distance).

A fin de describir la variabilidad espacio temporal de las comunidades de plantas acuáticas en un humedal de los Llanos de Venezuela, se estudiaron su riqueza y abundancia, en 14 hábitat, durante un ciclo anual. En los transectos de estudio se identificó un total de 69 especies. Según el análisis de diversidad con interacción de Alatalo y Alatalo el aspecto temporal, es decir el régimen anual de lluvia-sequía y la consecuente variación del nivel del agua, es el factor que ejerce mayor influencia sobre la riqueza de especies, en relación al aspecto espacial, o tipo de hábitat. Según el índice geométrico de las distancias euclídeas, se concluye igualmente que la variación en la abundancia de especies se debe más a las fluctuaciones hidrométricas (estacionalidad) que al hábitat considerado.

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Ten traits related to life history theory were measured or estimated for 71 freshwater fish species from two locations in the Venezuelan llanos. Multivariate statistics and cluster analysis revealed three basic endpoint patterns bounding a two-dimensional continuum. A suite of attributes associated with parental care and aseasonal reproduction appeared to correspond to an equilibrium strategy. A second group of small fishes was distinguished by traits associated with rapid colonizing ability: early maturation, continuous reproduction, and small clutches. The third basic pattern was associated with synchronized reproduction during the early wet season, high fecundity, absence of parental care, and breeding migrations. A subset of mostly small fishes exhibiting little or no parental care, small clutches, and two to four month reproductive seasons was intermediate between the opportunistic (rapidly colonizing) and seasonal strategies. All ten life history variables showed significant effects of phylogeny. The cluster of species corresponding to the equilibrium group was dominated by siluriform fishes and perciforms of the Cichlidae. The opportunistic cluster was dominated by cyprinodontiform and characiform fishes, whereas the seasonal cluster contained primarily characiform and siluriform fishes. Seven of nine traits were significantly correlated with body length. The three reproductive patterns are interpreted as being adaptative with respect to relative intensity and predictability of temporal and spatial variation in abiotic environmental parameters, food availability, and predation pressure.