3,089 research outputs found
Pollen morphology of Nothofagus (Nothofagaceae, Fagales) and its phylogenetic significance
Nothofagaceae (southern beeches) are a relatively small flowering plant family of trees confined to the Southern Hemisphere. The fossil record of the family is abundant and it has been widely used as a test case for the classic hypothesis that Antarctica, Patagonia, Australia and New Zealand were once joined together. Although the phylogenetic relationships in Nothofagus appear to be well supported, the evolution of some pollen morphological traits remains elusive, largely because of the lack of ultrastructural analyses. Here we describe the pollen morphology of all extant South American species of Nothofagus, using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and light microscopy (LM), and reconstruct ancestral character states using a well-supported phylogenetic tree of the family. Our results indicate that the main differences between pollen of subgenera Fuscospora (pollen type fusca a) and Nothofagus (pollen type fusca b) are related to the size of microspines (distinguishable or not in optical section), and the thickening of colpi margins (thickened inwards, or thickened both inwards and outwards). In particular, Nothofagus alessandrii, the only extant South American species of subgenus Fuscospora, presents distinctive pollen features that have not been observed in any other species of the genus (i.e. a large granular infratectum and spongy apertural endexine). Species of subgenus Lophozonia are characterized by having the largest pollen grains, with polygonal outline in polar view, microspines distinguishable in optical section, long and non-thickened colpi, and a thin endexine. The reconstruction of character states for the node corresponding to the common ancestor to genus Nothofagus leads us to conclude that the ancestral form of Nothofagaceae should have had: equatorial diameter < 40 μm, circular outline in polar view, microspines distinguishable in optical section, short colpi thickened inwards, and a thin endexine. These features are fully consistent with those present in Nothofagidites senectus Dettmann & Playford, the oldest fossil species of Nothofagaceae recorded in Campanian-Maastrichtian sediments of Gondwana.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: Santamarina, Patricio Emmanuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: 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
El fons documental de l’empresa Viuda Sauquet a l’Arxiu Municipal de Granollers
Des de l’any 1939 fins al 2013 va funcionar a Granollers l’empresa tèxtil Viuda Sauquet. Amb el seu tancament definitiu l’any 2013, desapareixia una de les darreres empreses tèxtils en funcionament a la ciutat. Gràcies a la donació de la família Sauquet, va ingressar a l’Arxiu Municipal de Granollers (AMGr) una gran part de la documentació de la fàbrica, que ha constituït el fons documental Viuda Sauquet, format per 20 metres de documents d’entre 1925 i 2013. Juntament amb el fons documental de l’empresa Roca Umbert, aquest és el segon fons d’empresa consultable a l’Arxiu Municipal de Granollers d’un sector, el tèxtil, que durant més d’un segle va ser protagonista absolut de l’activitat econòmica de la ciutat. En aquest article es descriu aquest fons documental i es presenta un breu resum de la història de l’empresa
Exploring the Nature of Strategic Interactions in the Ratification Process of the Kyoto Protocol
Do countries interact when they decide whether or not to ratify the Kyoto Protocol? If so, what is the nature of these interactions? To answer these questions, we provide a theoretical analysis based on the notions of strategic substitutability and strategic complementarity. Firstly, we analyze the nature of interactions between countries when they are merely seeking to provide a global public good. Secondly, we argue that countries have ties in several spheres in the real world and we try to shed light on the nature of the strategic interactions generated by geographic proximity, trade flows, and green investment flows. The empirical investigation is realized via the estimation of a parametric survival model, and our data sample covers 164 countries for the period from 1998 to 2009. We find evidence that, while countries' ratification decisions are originally strategic substitutes, they became strategic complements when we focus on the ratification decisions of specific peers.Ratification, Kyoto Protocol, International Environmental Agreements, Spatial survival model
Challenges and questions in reconstructing the ancestral flower of angiosperms: A reply to Sokoloff et al
Le partage de la ressource en eau sur la Durance en 2050 : vers une évolution du mode de gestion des grands ouvrages duranciens ?
Congrès SHF: Water Tensions in Europe and in the Mediterranean: water crisis by 2050?, Paris, FRA, 08-/10/2015 - 09/10/2015International audienceUne vision prospective de la gestion de l'eau du bassin de la Durance et des territoires alimentés par ses eaux à l'horizon 2050 a été élaborée, appuyée par une chaine de modèles incluant des représentations du climat, de la ressource naturelle, des demandes en eau et du fonctionnement des grands ouvrages hydrauliques (Serre-Ponçon, Castillon et Sainte-Croix), sous contraintes de respect des débits réservés, de cotes touristiques dans les retenues et de restitution d'eau stockée pour des usages en aval. Cet ensemble, validé en temps présent, a été alimenté par des projections climatiques et paramétré pour intégrer les évolutions du territoire décrites par des scénarios de développement socio-économique avec une hypothèse de conservation des règles de gestion actuelles. Les résultats suggèrent à l'horizon 2050 : une hausse de la température moyenne de l'air impactant l'hydrologie de montagne ; une évolution incertaine des précipitations ; une réduction des stocks de neige et une fonte avancée dans l'année qui induisent une réduction des débits au printemps ; une diminution de la ressource en eau en période estivale ; une diminution de la demande globale en eau à l'échelle du territoire, cette demande étant fortement conditionnée par les scénarios territoriaux élaborés ici ; la satisfaction des demandes en eau en aval des ouvrages considérées comme prioritaires, au détriment de la production d'énergie en hiver (flexibilité moindre en période de pointe) et du maintien de cotes touristiques en été ;une diminution de la production d'énergie due notamment à la réduction des apports en amont des ouvrages hydroélectriques
Can we talk about a GATPAC urbanism without Le Corbusier’s influence?
El artículo revisa los proyectos urbanos del GATCPAC (Grupo de Arquitectos y Técnicos Catalanes para el Progreso de la Arquitectura Contemporánea) con el objetivo de comprender cuál es el modelo urbano que está en su base y revelar posibles influencias. Desde la publicación en 1935 del Pla Macià en el libro La Ville Radieuse es frecuente la vinculación de este plan con las ideas urbanísticas de Le Corbusier. Sin embargo, lo que aparece normalmente publicado sobre el plan, por ejemplo, los esquemas de manzanas del Ensanche de Cerdá reconvertidas en súper-manzanas con bloques redents lecorbuserianos o el famoso diorama de seis metros dibujado por el GATCPAC, son una pequeña parte de todo el conjunto de planes que el grupo catalán elaboró para la “Barcelona Futura”. A partir de cinco palabras –Barcelona, zonificación, (des)urbanización, organicismo y preservación–, el articulo va definiendo algunos de los puntos clave del urbanismo del GATCPAC; sitúa, en su justa relevancia estratégica por parte del grupo, lo definido conjuntamente con Le Corbusier y finaliza con una conclusión que, a modo de radiografía, describe un hipotético modelo urbano; una síntesis que el grupo nunca tuvo la ocasión de esquematizar.The article revises the planning projects of the GATCPAC (Group of Catalan Architects and Technicians for the Progress of Contemporary Architecture), in order to understand the urban model in their base and to reveal possible influences. Since the publication in 1935 of the Pla Macià in the book La Ville Radieuse, it is common to link this plan with the planning ideas of Le Corbusier. However, what is usually published from the plan, for example, the conversion of the Eixample Cerda blocks into super-blocks with LeCorbuserian redents-buildings, or the famous twenty-feet diorama drawn by the GATCPAC, are a small part of the set of plans the Catalan group prepared for the “Barcelona Futura”. Using five words -Barcelona, zoning, (un)urbanism, organicism and preservation- the article defines some of the key points of the GATCPAC planning ideas and places in its exact strategic importance for the group, the points developed together with Le Corbusier. Finally, it ends with a conclusion that, as in an X-ray photography, describes a hypothetical urban model; the summary which the group could never outline
Zygomorphic Flowers May Reduce Extinction Rates by Allowing Angiosperms to Occur in Low Abundances
The high species richness that angiosperm show has been extensively correlated with key floral innovations. Key floral traits contribute to species boundaries and the origin of new species. However, how these relate to extinction remains largely untested. Among the multiple theories that attribute diversification to floral innovations, the reduced extinction model predicts that floral specialization allows the persistence of small populations and avoids their loss. Bilateral symmetry (zygomorphy) is a trait that has evolved recurrently in angiosperms. It is a form of floral specialization that restricts pollination to fewer visitors and precisely places pollen to ensure more effective transmission of pollen between conspecific flowers. In this study, I investigate the relationship between floral symmetry and abundance of species from 33 (1 ha) plots in tropical and subtropical forest in the Madidi National Park, Bolivia. If zygomorphy reduces the extinction of rare species, that is, species with small local abundance and low occupancy then, zygomorphy is present in smaller and more dispersed populations. For this, I carry out linear models with phylogenetic correction that explain the abundance of 545 species according to zygomorphy of the petals, of the stamens and stigma, and corolla shape. Results show that corolla zygomorphy is present in species with smaller populations. Species that contribute to this pattern are mainly present in the species-rich sub-humid and humid forest. However, zygomorphy of the reproductive organs does not have a significant impact in species abundances except for the analysis of species from the higher elevation. Multiple selective forces can shape the abundance of species. When facing the biotic forces that affect success of reproduction, such as pollinator availability and interspecific pollination, zygomorphy seems to provide an advantage to species that are rare by allowing them to persist at low abundances. More studies that further explore the causes for zygomorphy in smaller populations and the extinction rate using phylogenetic methods can help to understand how species loss is avoided
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