1,721,017 research outputs found
Echinate fossil pollen of Asteraceae from the Late Oligocene of Patagonia: An assessment of its botanical affinity
Full text linkThe Late Oligocene Mutisiapollis telleriae, which is the oldest echinate fossil pollen of Asteraceae from Patagonia, was tentatively related to the subfamily Mutisioideae. A detailed comparison of M. telleriae with extant asteraceous pollen indicates strong similarities with both Mutisioideae (in particular the Gongylolepis type) and Carduoideae (some genera of Carduinae) subfamilies. This morphotype, as an example of the exceptional diversity of fossil pollen of Asteraceae found in Patagonia, contributes to the knowledge of the early history of the family.Fil: Tellería, María Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Laboratorio de Sistemática y Biología Evolutiva; ArgentinaFil: Barreda, Viviana Dora. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; ArgentinaFil: Palazzesi, Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; ArgentinaFil: Katinas, Liliana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División de Plantas Vasculares; Argentin
Role of climate and tectonism on the modernization of Patagonian floras: Evidence from the fossil record
No full textA major reorganization of Patagonian ecosystems occurred when permanent ice sheets appeared in Antarctica and the Andean Range uplifted in southern South America. Rich plant communities dominated by Gondwanan trees and other species with tropical modern distribution vanished and those with cool and arid distributions rose to prominence. Rather than a single event, this landscape-level floristic replacement may have occurred as pulses following the paleoclimatic dynamism of the Coolhouse state (~34–4 Ma). However, the associated shifts in diversity and in climatically-key sensitive plant species have never been studied in detail so far. Here, we estimated richness using robust (non-parametric) methods and selected climatically-sensitive species to trace back past floristic trends in the high southern latitudes during the Coolhouse state. We used a high resolution palynological record from well-constrained Patagonian sediments from the Early Oligocene to the Late Miocene (~34–10 Ma), spanning most of the Coolhouse state. Our fossil data reveal the presence of five major floristic phases, closely linked with global climate states and regional orographic events. We found that diversity rises during global warming periods (↑100% at the Late Oligocene Warming Event or LOWE and ↑50% at the Miocene Climatic Optimum or MCO) and drops during glaciation periods (↓60% at Oi-1 (earliest Oligocene), ↓50% at Mi-1 (earliest Miocene) and ↓35% at Mi-3 (Middle Miocene) glaciation events) or intense tectonism (↓60% after the Andean uplift), relative to background levels. The representation of warm-demanding taxa peaked during LOWE and MCO, while arid-adapted taxa rose briefly during the MCO and took over following the major surface uplift of the southern Andes by 15–14 Ma. Humid-demanding species (e.g., tree-ferns) showed a general decreasing trend in abundance from their climax at 34 Ma to their minimum occurrence at 10 Ma. Our study reveals the potential of using robust statistical diversity methods in unraveling the relationship between past floras and climatic-orogenic forcing during the Coolhouse state.Fil: Barreda, Viviana Dora. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Palazzesi, Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentin
Fossil pollen records reveal a late rise of open-habitat ecosystems in Patagonia
Full text linkThe timing of major turnovers in terrestrial ecosystems of the Cenozoic Era has been largely interpreted from the analysis of the assumed feeding preference of extinct mammals. For example, the expansion of open-habitat ecosystems (grasslands or savannas) is inferred to have occurred earlier in Patagonia than elsewhere because of the early advent of high-crowned teeth (hypsodont) mammals ∼26 Ma ago. However, the plant fossil record from Patagonia implies another evolutionary scenario. Here we show that the dominance of key open-habitat species - amaranths, Ephedra, asters and grasses - occurred during the last 10 Ma, about 15 Ma later than previously inferred using feeding/habitat ecology of extinct mammals. This late rise of open-landscapes in southern South America brings into question whether the expansion of open-habitat vegetation could have been the prime factor of high-crowned mammal diversification.Fil: Palazzesi, Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; ArgentinaFil: Barreda, Viviana Dora. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentin
Evolutionary significance of exine ultrastructure in the subfamily Barnadesioideae (Asteraceae) in the light of molecular phylogenetics
Full text linkBarnadesioideae (94 species) is the sister subfamily to the rest of the Asteraceae (23,000 species). Pollen grains in this subfamily are structurally and sculpturally distinctive and diverse. Although pollen morphology has contributed to the taxonomy of the subfamily, there is a gap of knowledge concerning the evolution of the exine structure. This study aims at exploring the systematic and phylogenetic significance of optimizing selected pollen characters of Barnadesioideae on the latest molecular phylogenetic tree. Transmission electron microscope (TEM) observations on pollen of selected species, some of them never explored so far, show that the exine probably evolved from a thin pattern (ca. 1–3 μm), with a well-developed foot layer and solid and free columellae, present in sister family Calyceraceae, towards a thicker (> 6–11 μm) and a more complex columellate-granulate bilayered exine in Barnadesioideae (with very delicate columellae). The particular exine structure observed in the monotypic Schlechtendalia luzulaefolia, which combines compact and independent columellae (common in more derived Asteraceae) with a granular internal tectum as the inner ectexine layer (as in Barnadesioideae), reinforces its distant phylogenetic position within Barnadesioideae. More derived lineages within Asteraceae (e.g. Mutisioideae) retained some ancestral exine features although evolved an even thicker exine and a columellate trilayered exine (with robust columellae), rare in the angiosperm pollen grains.Fil: Tellería, María Cristina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Laboratorio de Sistemática y Biología Evolutiva; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Palazzesi, Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Barreda, Viviana Dora. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentin
Pollen morphology of the least known families of the order Asterales
Full text linkThe recent discovery of pollen grains assigned to the earliest branch of Asteraceae from Cretaceous sediments in Antarctica prompted us to examine the pollen from five lesser known members of Asterales (Alseuosmiaceae, Argophyllaceae, Pentaphragmataceae, Phellinaceae and Roussaceae) that might also be represented in fossil sediments. Detailed pollen morphology in the basal members of the order Asterales has, until now, been incomplete. Our study reveals a highly variable pollen morphology of these small, and poorly explored families. The tricolporate character of Phelline macrophylla and the zono-hexaporate aperture of Roussea simplex are described for the first time. Pollen of Alseuosmiaceae share granulate structure and tectum little sculpturate, with the exception of Periomphale which is verrucate; Crispiloba has an isolated position due to very large size and porate aperture. Pollen of Argophyllaceae is relatively homogeneous sharing tricolporate aperture, tectum little sculpturate and columellate structure. Pentaphragmataceae is distinguished by its smallest pollen, with oblate-peroblate shape, di or tricolporate aperture and psilate exine. Roussaceae is the most diverse family at level of dispersion unit, aperture type, sculpture and structure of exine. The morphological characters here analysed can be potentially used to unmask fossil dispersed pollen grains with unknown botanical affinity.Fil: Tellería, María Cristina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Laboratorio de Sistemática y Biología Evolutiva; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Barreda, Viviana Dora. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Palazzesi, Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentin
The presence of a neotropical family (Malpighiaceae) in the far south of South America during the Eocene
Full text linkPresented here is the discovery of pollen grains and a foliar impression assigned to Malpighiaceae from the Río Turbio Formation, SW Santa Cruz Province, indicating the presence of this Neotropical family in the southernmost tip of South America by the Eocene. Perisyncolporites pokornyi Germeraad, Hopping & Muller, erected to group fossil pollen similar to Malpighiaceae, includes a wide variety of pollen-forms with a complex aperture distribution, more or less concordant with the sides of a hexagon. The extant clades most closely related to the fossil forms of the Río Turbio Formation (Tetrapteroids and Stigmaphylloids) are today distributed in tropical and subtropical regions of South America, reaching up to the 35ºS. The only extant species distributed closer to the studied area, and that, in turn, represents the world’s southernmost penetration of the family (Gallardoa fischeri Hicken, reaching the 42°S), is morphologically unrelated to the studied fossils. The foliar impression is similar to those recognized previously in the Río Pichileufú locality, Río Negro Province (Mascagnia sepiumoides Berry, Tetrapteris precrebrifolia Berry), and also in the Río Turbio Formation (Tetrapteris precrebrifolia Berry). The present results support earlier hypotheses that suggest a major penetration of Neotropical lineages into the southernmost latitudes during the Eocene as well as a possible migration to Australia via Antarctica, at least of those perisyncolporate-related forms.Fil: Fernández, Damián Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Panti, Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Palazzesi, Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Barreda, Viviana Dora. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentin
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Laboratorio de Paleopalinología (BA Pal) Museo Argentino de Ciencias Naturales "Bernardino Rivadavia" - CONICET
Full text linkLa Colección de Paleopalinología, iniciada en los primeros años de la década de 1960 por el Dr. Carlos A. Menéndez, constituye una de las 4 Colecciones Nacionales de Paleontología depositadas en el Museo Argentino de Ciencia Naturales (http://www.macn.secyt.gov.ar/Investigacion). Esta colección, como parte de la Colección Nacional de Paleobotánica, es reconocida a nivel internacional bajo la sigla BA, otorgada por la International Association of Plant Taxonomists (asociación que regula las condiciones que debe presentar una colección para ser acreditada internacionalmente)...Fil: Gutierrez, Pedro Raul. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; ArgentinaFil: Barreda, Viviana Dora. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; ArgentinaFil: Perez Loinaze, Valeria Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; ArgentinaFil: Palazzesi, Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; ArgentinaFil: Balarino, María Lucía. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentin
Variations on the Author
Full text link“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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