1,721,003 research outputs found
Una revisión de la evidencia de la dependencia de la soja [Glycine max (L.) Merr.] de la polinización por insectos
No full textLa comprensión de los servicios ecosistémicos, con toda la complejidad que implica, es necesaria para un manejo adecuado de los ecosistemas, y los científicos deben generar esa información para que sea utilizada en la toma de decisiones. Las recomendaciones de manejo se basan en evidencia científica que puede ser de calidad variable. La importancia de la polinización de cultivos es un ejemplo de un servicio ecosistémico para el cual se ha acumulado un volumen de evidencia creciente. En particular para soja hay varios trabajos que sugieren que el rendimiento del cultivo depende de la acción de polinizadores. Sin embargo, esto contradice lo que tradicionalmente se asume del cultivo. En este contexto, es necesario revisar críticamente la evidencia disponible para decidir si es necesario un cambio en las recomendaciones de manejo del servicio de polinización de este cultivo.Fil: Palacios, Tania Paula. Universidad de Buenos Aires. Facultad de Agronomía. Cátedra de Botánica General; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Devoto, Mariano. Universidad de Buenos Aires. Facultad de Agronomía. Cátedra de Botánica General; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaPrimera reunión de la red de investigadores en biología de la polinización de ArgentinaCiudad Autónoma de Buenos AiresArgentinaUniversidad de Buenos Aires. Facultad de Agronomí
Evidencia preliminar de la existencia de estructuración en el nivel de paisaje en una población de una hierba perenne, Cypella Herbertii (Iridaceae)
Get PDFPresentamos evidencia preliminar de la existencia de una estructura genética en el nivel de paisaje en una población de Cypella herbertii. Esto podría ser consecuencia de la reducción en el flujo de polen que ocurre en las poblaciones intensamente pastoreadas de esta especieWe present preliminary evidence for the existence of a genetic landscape-level structuring that might be a consequence of depressed pollen flow across heavily grazed populations of Cypella herbertii.Fil: Devoto, Mariano. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Botánica Agrícola; ArgentinaFil: Medan, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Botánica Agrícola; Argentin
Reproductive ecology of a perennial outcrosser with a naturally dissected distribution
Get PDFWe surveyed four populations of contrasting size (two isolated and two large stands) of a woody outcrossing species, Discaria trinervis (Rhamnaceae), which has a naturally dissected distribution. Our main goal was to investigate the floral biology, breeding system and pollination mechanism of the species, which in turn may help to explain the mechanisms underlying the survival of the isolated populations. Discaria trinervis is both wind- and insect-pollinated, showing interactions with a large fraction of the available flower visitors at both stand sizes. In the larger populations, stigmatic loads were larger, more pollen tubes reached the ovules, and fruit and seed set were higher; however, the reproductive output in the smaller populations (over 2000 seeds per plant per year) seemed adequate for population persistence. Human disturbance (e.g. destruction of trees for wood extraction) may put these smaller populations at risk through loss of incompatibility alleles. The results suggest that plant species with naturally dissected distributions may provide clues about which reproductive mechanisms ensure survival under fragmentation.Fil: Medan, Diego. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Botánica Agrícola; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; ArgentinaFil: Devoto, Mariano. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Botánica Agrícola; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; Argentin
Sistema de apareamiento esperado, diversidad floral y visitantes florales de cinco especies de Iridaceae de la región pampeana argentina
Get PDFLas Iridáceas son una familia de plantas interesantes desde el punto de vista de la biología reproductiva debido a que la diversidad de estructuras florales de sus especies atrae una variedad de visitantes florales. Este trabajo describe algunos aspectos reproductivos de cinco especies de Iridáceas de la cuenca del río Salado en las pampas argentinas:Cypella herbertii, Alophia lahue y tres especies de Sisyrinchium. C. herbertii exhibe una interacción especializada con abejas colectoras de aceite, mientras que el resto de las especies estudiadas posee visitantes poco especializados. Para A. lahue y las especies de Sisyrinchium analizadas las estimaciones del sistema de apareamiento tienden a subestimar el grado de autogamia encontrado en experimentos previos. Observaciones de campo verificaron la producción de néctar en las flores de C. herbertii y sugieren que el éxito reproductivo de esta especie podría estar limitado por polen en una de las poblaciones estudiadas.Iridaceae is an interesting plant family from the viewpoint of reproductive biology because the diverse floral structures of its species attract a gamut of different flower visitors. This work reports some reproductive aspects of five species of Iridaceae of the Salado river basin in the Argentine pampas: Cypella herbertii, Alophia lahue and three species of Sisyrinchium. C. herbertii exhibits a specialized interaction with oil-collecting bees, while the rest of the species studied had rather unspecialized visitors. For A. lahue and the species of Sisyrinchium analyzed estimations of expected mating system tend to underestimate the degree of autogamy found in previous experiments. Field observations verified the production of nectar in the flowers of C. herbertii and suggested that the reproductive success of this species might be pollen limited in one of the population studied.Fil: Devoto, Mariano. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Botánica Agrícola; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Medan, Diego. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Botánica Agrícola; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Ambophily, not entomophily: the reproduction of the perennial Discaria chacaye (Rhamnaceae: Colletieae) along a rainfall gradient in Patagonia, Argentina
Get PDFGeographical gradients are useful tools for studying how changing environmental conditions affect communities’ structure and function, and any perceived general pattern can be tested by examining the response of different populations of a given species widely distributed along the focal gradient. We studied populations of the perennial, putatively entomophilous plant Discaria chacaye located along a strong east–west rainfall gradient in the north-west of Patagonia, Argentina, where a significant community-level eastwards replacement of Diptera by Hymenoptera as main flower visitors takes place. Discaria chacaye showed an invariant set of traits (flowers rewarding with nectar and pollen a fly-dominated pollinator assemblage, combined with protandry, incomplete dichogamy and self-incompatibility) which were modulated by site-dependent factors (availability of pollinators, wind strength, and perhaps abundance of seed predators). The interplay between all factors resulted in an increase in fruit set from the wet to the dry end of the gradient. Unexpectedly, wind was found to be an important pollen transporter, while (a) the plant’s use of pollinator groups was mostly uncorrelated with their local abundances along the gradient, and (b) both pre-and postzygotic fecundity losses occurred, mostly attributable to geitonogamy. The finding of ambophily in D. chacaye suggests that this pollination strategy could be more frequent than previously suspected along the studied gradient.Fil: Medan, Diego. Universidad de Buenos Aires. Facultad de Agronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Devoto, Mariano. Universidad de Buenos Aires. Facultad de Agronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Patterns of interaction between plants and pollinators along an environmental gradient
Get PDFPatterns of variation in plant-pollinator (p-p) systems in response to environmental variables have been the focus of much recent attention. We analyzed species diversity and generalization of interactions of flower visitors belonging to eight p-p networks along a steep rainfall gradient in NW Patagonia, Argentina. To our knowledge, this is the first published study that applies a humidity - gradient approach to p-p networks analysis. Throughout the gradient, we recorded 1232 interactions between 413 different animal species and 111 plant species. We found that (a) specialization measures showed no clear pattern of variation throughout the rainfall gradient, (b) the diversity of flower-visiting insects does not consistently respond to rainfall gradients along the gradient, and (c) as we predicted, flies dominated the wetter end of the gradient, while at the drier end bees prevailed. The lack of differences in diversity could be explained by the repeated cycles of species extinctions undergone in the past by the southern temperate forests, which dominate the wetter end of the gradient. A logistic model that related the flies' dominance of the visitor assemblage with latitude was good predictor of the average fly composition of the entire region, although we found major between-site variations in response to local environmental conditions. The replacement of flies by bees towards the drier end of the gradient seemed to repeat a worldwide pattern where flies dominate humid regions while bees attain their greatest abundance in xeric regions. Regional patterns in the structure of our p-p systems (composition of the visitor fauna) were better explained by altitudinal differences, while function (percentage of interactions established by each taxon) seemed to be more influenced by precipitation.Fil: Devoto, Mariano. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Botánica Agrícola; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; ArgentinaFil: Medan, Diego. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Botánica Agrícola; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; ArgentinaFil: Montaldo, Norberto Horacio. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Botánica Agrícola; Argentin
Plant–frugivore interactions in an urban nature reserve and its nearby gardens
Get PDFIn the current global context of growing urbanization, urban nature reserves play a crucial role as habitats that serve educational, recreational and conservation purposes. Biodiversity conservation within urban reserves is a challenging task, particularly since connectivity between a reserve and its surrounding artificial green spaces (e.g. gardens and parks) may affect the ecological processes within the reserve in complex ways. In this context, we studied the feeding interactions between plants and birds to provide evidence that an urban nature reserve is connected to its surrounding artificial habitats by mobile organisms. We focused on fleshy-fruited plants and frugivorous birds, and we used a network approach to describe the feeding interactions between these two guilds. The most important connecting bird was Turdus rufiventris, an abundant and obligate frugivore, whose abundance was positively linked to fruit availability in most of the study sites. The apparent increase in the abundance of T. rufiventris in one habitat when it decreases in the other suggests that the two habitats may be complementary for this species. The nature reserve, with many native plants, however, seems to be the preferred site when both habitats offer an abundant fruit supply. Our results suggest changes in either habitat can have consequences in the other one, which has broad implications for the design of management plans of urban nature reserves.Fil: Zietsman, Mariki Yvonne. Universidad de Buenos Aires. Facultad de Agronomía. Cátedra de Botánica General; ArgentinaFil: Montaldo, Norberto Horacio. Universidad de Buenos Aires. Facultad de Agronomía. Cátedra de Botánica General; ArgentinaFil: Devoto, Mariano. Universidad de Buenos Aires. Facultad de Agronomía. Cátedra de Botánica General; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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