Research on arid ecosystems in the region : research potential and possible areas of concentration

Meeting: Reunión sobre Capacidad de Investigación en Temas de Medio Ambiente en América Latina y el Caribe, 27-29 enero 1992, Montevideo, U

Functional variants of DOG1 control seed chilling responses and variation in seasonal life-history strategies in Arabidopsis thaliana.

The seasonal timing of seed germination determines a plant's realized environmental niche, and is important for adaptation to climate. The timing of seasonal germination depends on patterns of seed dormancy release or induction by cold and interacts with flowering-time variation to construct different seasonal life histories. To characterize the genetic basis and climatic associations of natural variation in seed chilling responses and associated life-history syndromes, we selected 559 fully sequenced accessions of the model annual species Arabidopsis thaliana from across a wide climate range and scored each for seed germination across a range of 13 cold stratification treatments, as well as the timing of flowering and senescence. Germination strategies varied continuously along 2 major axes: 1) Overall germination fraction and 2) induction vs. release of dormancy by cold. Natural variation in seed responses to chilling was correlated with flowering time and senescence to create a range of seasonal life-history syndromes. Genome-wide association identified several loci associated with natural variation in seed chilling responses, including a known functional polymorphism in the self-binding domain of the candidate gene DOG1. A phylogeny of DOG1 haplotypes revealed ancient divergence of these functional variants associated with periods of Pleistocene climate change, and Gradient Forest analysis showed that allele turnover of candidate SNPs was significantly associated with climate gradients. These results provide evidence that A. thaliana's germination niche and correlated life-history syndromes are shaped by past climate cycles, as well as local adaptation to contemporary climate

The impact of significant input of fine sediment on benthic fauna at tributary junctions: a case study of the Bermejo-Paraguay River confluence, Argentina

This study examines the morphological features, suspended sediment inputs and hydraulic conditions within a large river in association with ecological patterns before and after a tributary confluence. In order to examine these effects, the macroinvertebrate distributions from three reaches of the Paraguay and Bermejo Rivers (Paraguay-Argentina) are investigated. The Bermejo River is a tributary that supplies significant quantities of fine sediment to the Paraguay River, primarily in suspension. Two reaches were examined on the Paraguay River, upstream and downstream of the Bermejo River junction, with the third study reach located on the Bermejo River, upstream of the confluence with the Paraguay River. The results provide clear evidence that a significantly increased loading of fine sediment at a river confluence has effects on the distribution and potential movement of benthic invertebrates in the lotic environment by representing physical barriers at affected sites. These effects may be important at both local and regional scales, and such increases in suspended sediment (especially associated with anthropogenic change) may thus pose a major threat to ecosystem integrity that has been historically underestimated

Calidad educativa: la motivación docente como elemento clave

Los sistemas educativos mundiales están en continuo desarrollo hacia una educación de calidad, siendo esta un elemento en constante perfeccionamiento y mejora. Concretamente, en España, la actual legislación educativa promulga acciones con el fin de lograr máximas de Es fundamental conocer qué agentes y factores contribuyen a la misma para que las propuestas de calidad sean coherentes y ajustadas a un contexto determinado. De forma generalizada se otorga gran valor al profesor y a su papel transformador en el proceso de enseñanza-aprendizaje. Se podría afirmar que es el agente más importante que contribuye a la calidad educativa. Es el intermediario entre el conocimiento y el aprendizaje del alumno. Actualmente el docente se enfrenta a un contexto y acontecimientos que pueden poner en juego su bienestar, así como modificar sus creencias de valor hacia la educación. Ante esta realidad no existe un respaldo suficiente por parte de las administraciones, haciendo que en ocasiones el profesional se sienta solo y desprestigiado. Sin embargo, es imprescindible que el profesor esté dotado de una serie de cualidades que le permitan dar de sí lo mejor y potenciar el aprendizaje de los estudiantes, superando las dificultades encontradas en el camino. Concretamente, la motivación constituye uno de los factores principales a desarrollar y mantener en los docentes, considerándose a la misma el motor inicial que puede ayudar a impulsar otras habilidades. Consideramos que es imprescindible elaborar estrategias de actuación para mantener y fomentar la motivación del docente. Desde el centro educativo, mediante la colaboración de otros equipos, se pueden desarrollar ciertas acciones específicas que ayuden a lograr este fin.Global education systems are continually developing towards quality education, which is constantly being improved. In particular, there are many educational laws in Spain that, over the years, enact actions in order to achieve an educational quality. It is essential to know which agents and factors contribute to quality education in order to adjust coherent proposals in a specific context. The teacher has a great value and a transforming role in the teaching-learning process. It could be said that he is the most important agent that contributes to the quality of education. He is the intermediary between the knowledge and the student`s learning. Currently, teachers are faced with a context and events that may negatively affect their well-being, as well as modify their beliefs of personal competences. In this situation, there is no support from the Educational Administration, making the professional feel alone and discredited. However, it is essential that the teacher has different qualities that allow him to give the best and to promote student learning, overcoming the difficulties found along the way. Specifically, motivation is one of the main factors to develop and maintain in teachers, considering it the initial engine that can build other skills. It is crucial to develop action strategies to maintain and promote teacher’s motivation. From the school, through the collaboration of the professionals who work in it, specific actions could be developed to achieve this aim

Hydrodynamic and morphologic effects on the benthic invertebrate ecology along a meander bend of a large river (Paraguay River, Argentina-Paraguay)

A detailed hydro-ecological study to identify the effects of bed flow and morphodynamic processes on the distribution (and composition) of benthic invertebrates in a large river is presented herein. A crossing-pool sequence in a meander bend of the Paraguay River (Paraguay-Argentina) was examined. According to the results, there is a link between the benthic fauna, hydraulic and bed sediment size along the bend. The meander pool, with a deep scour hole and the largest bed shear stresses, would be a hostile area for benthic invertebrates, since lower densities were found there. A transversal analysis revealed two different invertebrate assemblages at each of the sampled cross sections: one across the mobile bottom with higher densities but lower diversity, richness and evenness than the other one found close to the banks. On the other hand, a comparison between both Paraguay and Paraná rivers revealed that the first one would seem to have optimal hydraulic conditions for the invertebrate's development, because the hydraulic energy of the Paraná River was too intense for the favorable settlement of benthic organisms at some specific habitats. The overall conclusion of this paper, that morpho-hydraulic features and biotopes are related, is an important step forward in river ecohydrology. With further development of this concept, river management techniques can improve and river rehabilitation projects can be designed with greater confidence.Fil: Blettler, Martin Cesar Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; ArgentinaFil: Amsler, Mario Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; ArgentinaFil: Ezcurra de Drago, Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; ArgentinaFil: Drago, Edmundo Carlos E.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; ArgentinaFil: Paira, Aldo Raul. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; ArgentinaFil: Espínola, Luis Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentin

Feeding spectra and activity of the freshwater crab Trichodactylus kensleyi (Decapoda: Brachyura: Trichodactylidae) at La Plata basin

Background: In inland water systems, it is important to characterize the trophic links in order to identify the ‘trophic species’ and, from the studies of functional diversity, understand the dynamics of matter and energy in these environments. The aim of this study is to analyze the natural diet of Trichodactylus kensleyi of subtropical rainforest streams and corroborate the temporal variation in the trophic activity during day hours. Results: A total of 15 major taxonomic groups were recognized in gut contents. The index of relative importance identified the following main prey items in decreasing order of importance: vegetal remains, oligochaetes, chironomid larvae, and algae. A significant difference was found in the amount of full stomachs during day hours showing a less trophic activity at midday and afternoon. The index of relative importance values evidenced the consumption of different prey according to day moments. Results of the gut content indicate that T. kensleyi is an omnivorous crab like other trichodactylid species. Opportunistic behavior is revealed by the ingestion of organisms abundant in streams such as oligochaetes and chironomid larvae. The consumption of allochthonous plant debris shows the importance of this crab as shredder in subtropical streams. However, the effective assimilation of plant matter is yet unknown in trichodactylid crabs. Conclusions: This research provides knowledge that complements previous studies about trophic relationships of trichodactylid crabs and supported the importance of T. kensleyi in the transference of energy and matter from benthic community and riparian sources to superior trophic levels using both macro- and microfauna.Fil: Williner, Verónica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina. Universidad Nacional del Litoral. Facultad de Humanidades y Ciencias; ArgentinaFil: de Azevedo Carvalho, Debora. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; ArgentinaFil: Collins, Pablo Agustin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; Argentin

Non-CO2 generating energy shares in the world : cross-country differences and polarization.

The aim of this paper is to examine the spatial distribution of non-CO2 generating energy sources in the world for the period 1990–2009, paying special attention to the evolution of cross-country disparities. To this end, after carrying out a classical convergence analysis, a more thorough investigation of the entire distribution is presented by examining its external shape, the intra-distribution dynamics and the long-run equilibrium distribution. This analysis reveals the existence of a weak, rather insignificant, convergence process and that large crosscountry differences are likely to persist in the long-run. Next, as polarization indicators are a proper way of appraising potential conflict in international environmental negotiations, we test whether, or not, the distribution dynamics concurs with the presence of polarization. Our results indicate that two poles can be clearly differentiated, one with high and other with low non-CO2 generating energy shares. In view of these findings, and to ensure a fair transition to a sustainable energy system, the paper calls for the development of an ambitious clean energy agenda, especially in countries with low non-CO2 generating energy shares

Untangling the dinosaur family tree

For over a century, the standard classification scheme has split dinosaurs into two fundamental groups: ‘lizard-hipped’ saurischians (including meat-eating theropods and long-necked sauropodomorphs) and ‘bird-hipped’ ornithischians (including a variety of herbivorous species).In a recent paper, Baron et al. challenged this paradigm with a new phylogenetic analysis that places theropods and ornithischians together in a group called Ornithoscelida, to the exclusion of sauropodomorphs, and used their phylogeny to argue that dinosaurs may have originated in northern Pangaea, not in the southern part of the supercontinent, as has more commonly been considered. Here we evaluate and reanalyse the morphological dataset underpinning the proposal by Baron et al. and provide quantitative biogeographic analyses, which challenge the key results of their study by recovering a classical monophyletic Saurischia and a Gondwanan origin for dinosaurs. This shows that the Ornithoscelida hypothesis is not the final word, and that there is still great uncertainty around the basic structure of the dinosaur family tree.Fil: Langer, Max C.. Universidade de Sao Paulo; BrasilFil: Ezcurra, Martin Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; ArgentinaFil: Rauhut, Oliver Walter Mischa. Ludwig Maximilians Universitat; AlemaniaFil: Benton, Michael J.. University of Bristol; Reino UnidoFil: Knoll, Fabien. University of Manchester; Reino UnidoFil: McPhee, Blair W.. Universidade de Sao Paulo; BrasilFil: Novas, Fernando Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; ArgentinaFil: Pol, Diego. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Brusatte, Stephen L.. University of Edinburgh; Reino Unid