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The mechanisms associated with the intraseasonal variability of precipitation over South America during the spring season are investigated with emphasis on the influence of a quasi-stationary anomalous circulation over the southeastern South Pacific Ocean (SEP). A spectral analysis performed to the bandpass-filtered time series of daily precipitation anomalies for the La Plata Basin (LPB) and the South Atlantic convergence zone (SACZ) regions revealed several statistically relevant peaks corresponding to periods of roughly 23 days and 14-16 days--with the lower (higher) frequency peaks more prevalent for the SACZ (LPB). The large-scale circulation patterns preconditioning precipitation variability over both regions were explored by means of a regression analysis performed on the daily 500-hPa geopotential anomaly field provided by the NCEP--NCAR reanalysis dataset. The most prominent feature of the regression fields is the presence of a quasi-stationary anomalous anticyclonic (cyclonic) circulation over the southeastern South Pacific Ocean associated with positive rainfall anomalies over the LPB (SACZ) and, emanating from that high (low), an external Rossby wave propagating northeastward toward the South American continent. The synoptic-scale activity, quantified in terms of a frontal activity index, showed a strong influence on precipitation over the LPB and to a lesser extent over the SACZ. Moreover, the frontal activity is actually modulated by the anomalous high circulation over the SEP region. The behavior of this anomalous circulation may be supported by a positive feedback mechanism that can enhance the response of the high anomaly itself, which in turns reinforces the Rossby wave train propagating toward the South American continent. DOI: 10.1175/2009JAS3309.1

Byline: Mariano Re (1,2), Vicente Ricardo Barros (3,4) Abstract: Heavy rainfall trends in a region of south-eastern South America during 1959--2002 were discussed using daily data of 52 meteorological stations of Argentina, Brazil and Uruguay. Changes in intensity and frequency were both studied with different statistical tests and approaches to check the significance of trends of single and regional aggregated rainfall series. There were predominant positive trends in the annual maximum rainfalls, as well as a remarkable increment in the frequency of heavy rainfalls over thresholds ranging from 50 to 150 mm. However, significant positive trends were not shown in the series of annual maximums and shown only in 15% to 30% of the series of frequencies over thresholds. This lack of significance is due to the high variability of heavy rainfalls in space and time, which makes difficult their capture by single rain gauges. Thus, when the assessment of the heavy rainfall indicators of intensity and frequency were conducted at the regional and sub-regional level, it showed significant trends, both in intensity and frequency over thresholds, with a clearer signal in central and eastern Argentina between 30deg and 40deg S. Author Affiliation: (1) Computational Hydraulics Program, Hydraulics Laboratory, National Institute for Water (INA), Ezeiza-Canuelas Highway, J. Newbery Section, km 1,620, 1804, Ezeiza, Argentina (2) Mathematical Modeling Laboratory, School of Engineering, University of Buenos Aires, Av. Las Heras 2214, 1127, Buenos Aires, Argentina (3) Department of Oceanic and Atmospheric Sciences, University of Buenos Aires, Ciudad Universitaria, Pabellon II, 2deg piso, 1428, Buenos Aires, Argentina (4) Center for Atmospheric and Oceanic Research (CIMA, UBA/CONICET), Ciudad Universitaria, Pabellon II, 2deg piso, 1428, Buenos Aires, Argentina Article History: Registration Date: 28/05/2009 Received Date: 03/07/2007 Accepted Date: 15/12/2008 Online Date: 01/08/2009

December--March climatologies of precipitation and vertically integrated water vapor transport were analyzed and compared to find the main paths by which moisture is fed to high-rainfall regions in the Southern Hemisphere in this season. The southern tropics (20[degrees]S-0[degrees]) exhibit high rainfall and receive ample moisture from the northern trades, except in the eastern Pacific and the Atlantic Oceans. This interhemispheric flow is particularly important for Amazonian rainfall, establishing the North Atlantic as the main source of moisture for the forest during its main rainy season. In the subtropics the rainfall distribution is very heterogeneous. The meridional average of precipitation between 35[degrees] and 25[degrees]S is well modulated by the meridional water vapor transport through the 25[degrees]S latitude circle, being greater where this transport is from the north and smaller where it is from the south. In South America, to the east of the Andes, the moisture that fuels precipitation between 20[degrees] and 30[degrees]S comes from both the tropical South and North Atlantic Oceans whereas between 30[degrees] and 40[degrees]S it comes mostly from the North Atlantic after passing over the Amazonian rain forest. The meridional transport (across 25[degrees]S) curve exhibits a double peak over South America and the adjacent Atlantic, which is closely reproduced in the mean rainfall curve. This corresponds to two local maxima in the two-dimensional field of meridional transport: the moisture corridor from Amazonia into the continental subtropics and the moisture flow coming from the southern tropical Atlantic into the subtropical portion of the South Atlantic convergence zone. These two narrow pathways of intense moisture flow could be suitably called 'aerial rivers.' Their longitudinal positions are well defined. The yearly deviations from climatology for moisture flow and rainfall correlate well (0.75) for the continental peak but not for the oceanic peak (0.23). The structure of two maxima is produced by the effect of transients in the time scale of days.

Salt tolerance is an agronomically important trait that affects plant species around the globe. The Salt Overly Sensitive 1 (SOS1) gene encodes a plasma membrane [Na.sup.+]/[H.sup.+] antiporter that plays an important role in germination and growth of plants in saline environments. Quinoa (Chenopodium quinoa Willd.) is a halophytic, allotetraploid grain crop of the family Amaranthaceae with impressive nutritional content and an increasing worldwide market. Many quinoa varieties have considerable salt tolerance, and research suggests quinoa may utilize novel mechanisms to confer salt tolerance. Here we report the cloning and characterization of two homoeologous SOS1 loci (cgSOS1A and cgSOS1B) from C. quinoa, including full-length cDNA sequences, genomic sequences, relative expression levels, fluorescent in situ hybridization (FISH) analysis, and a phylogenetic analysis of SOS1 genes from 13 plant taxa. The cgSOS1A and cgSOS1B genes each span 23 exons spread over 3477 by and 3486 by of coding sequence, respectively. These sequences share a high level of similarity with SOS1 homologs of other species and contain two conserved domains, a Nhap cation-antiporter domain and a cyclic-nucleotide binding domain. Genomic sequence analysis of two BAC clones (98 357 by and 132 770 bp) containing the homoeologous SOS1 genes suggests possible conservation of synteny across the C. quinoa sub-genomes. This report represents the first molecular characterization of salt-tolerance genes in a halophytic species in the Amaranthaceae as well as the first comparative analysis of coding and non-coding DNA sequences of the two homoeologous genomes of C. quinoa. Key words: quinoa, SOS1, [Na.sup.+]/[H.sup.+] antiporter, synteny. La tolerance a la salinite est un caractere agronomique important chez plusieurs especes vegetales partout sur le globe. Le gene Salt Overly Sensitive 1 (SOS1) code pour un antiporteur [Na.sup.+]/[H.sup.+] de la membrane plasmique qui joue un role important dans la germination et la croissance des plantes en conditions salines. Le quinoa (Chenopodium quinoa Willd.) est une culture halophyte allotetraploide de la familles des amaranthacees qui affiche une valeur nutritionnelle impressionnante et dont le marche connait un essor mondial. Plusieurs cultivars de quinoa presentent une tolerance considerable a la salinite et la recherche suggere que le quinoa utilise des mecanismes inedits pour obtenir une telle tolerance. Les auteurs rapportent ici le clonage et la caracterisation de deux locus SOS1 homeologues (cgSOS1A et cgSOS1B) chez le C. quinoa. Cette caracterisation comprend les sequences completes des ADNc, les sequences genomiques, les niveaux relatifs d'expression, l'hybridation in situ en fluorescence (FISH) ainsi qu'une analyse phylogenetique des genes SOS1 provenant de 13 especes vegetales. Les genes cgSOS1A et cgSOS1B comptent tons deux 23 exons qui totalisent respectivement 3477 et 3486 pb de sequence codante. Ces sequences presentent une grande similarity avec les homologues SOS1 identifies chez d'autres especes et contiennent deux domaines conserves, un domaine antiporteur de cations Nhap et un domaine de liaison a des nucleotides cycliques. L'analyse de la sequence genomique de deux clones BAC (de 98 357 pb et 132770 pb) contenant des genes SOS1 homeologues suggere une possible conservation de la syntenie an sein des sousgenomes du C. quinoa. Ce travail constitue la premiere caracterisation de genes de tolerance a la salinite chez une espece halophyte de la famille des amaranthacees ainsi que la premiere analyse comparee de sequences codantes et non-codantes an sein des genomes homeologues du C. quinoa. Mots-cles : quinoa, SOS1, antiporteur [Na.sup.+]/[H.sup.+], syntenie. [Traduit par la Redaction], Introduction The productivity of over one-third of all arable land worldwide is affected by soil salinity (Epstein and Bloom 2005). High [Na.sup.+] concentrations in soil or water lead to high [...]

This study uses phylogenetic relationships of New World representatives of the species-rich genus Astragalus (Leguminosae; Papilionoideae) to follow up on recent evidence pointing to rapid and recent plant diversification patterns in the Andes. Bayesian and maximum likelihood phylogenetic analyses were done using nuclear rDNA ITS and chloroplast spacers trnD-trnT and trnfM-trnS1, either separately or in combination. The effect of using partitioned vs. nonpartitioned analyses in a Bayesian approach was evaluated. Highest resolution was obtained when the data were combined in partitioned or nonpartitioned Bayesian analyses. All phylogenies support two clades of South American species nested within the North American species, implying two separate invasions from North to South America. These two clades correspond to the original morphological classification of Johnston (1947 Journal of the Arnold Arboretum 28: 336-409). The mean ages of the South American clades were very recent but still significantly different (1.89 and 0.98 Ma). Upper and lower bounds on rates of diversification varied between 2.01 and 0.65 species/Ma for the older clade and 2.06 and 1.24 species/Ma for the younger clade. Even the lower bounds are still very high, reasserting Neo-Astragalus in the growing list of recent rapid radiations of plants, especially in areas with a high physiographic diversity, such as the Andes. Key words: Astragalus; biogeography; chloroplast spacers; internal transcribed spacer; Leguminosae; phylogeny; rates of diversification.

Abstract: Basic morphology, scanning electron microscopy, and DNA sequence data from the plastid trnL-F region and the nuclear internal transcribed spacer (ITS) regions were used to delimit the species of [...]

Humeral variation associated with digging ability in the subterranean rodent Ctenomys was analyzed through 6 functionally significant indexes. The humerus of some extinct and living species was slightly more specialized than that of fossorial octodontoids [dagger] Actenomys and Octodon, whereas it was highly specialized in some living species. The constant occurrence of greater epicondyles suggests a hierarchical pattern in the acquisition of scratch-digging specializations. A possible relationship between humeral morphological diversity and environments is preliminarily discussed. Key words: Ctenomyidae, morphofunctional humeral diversity, rodents, scratch-digging adaptations

The incident solar radiative fluxes, simulated by an atmospheric general circulation model over South America for the period 1986-88, are compared with the satellite-derived surface fluxes provided by the Surface Radiation Budget (SRB) datasets. The comparison shows that the model systematically overestimates both all-sky and clear-sky SRB fluxes while representing well their latitudinal variations. In order to analyze the reasons for the bias, the shortwave radiation code employed in the model is tested with more comprehensive techniques in a stand-alone mode. The results of testing demonstrate that the code underestimates solar radiation absorption in the clear-sky atmosphere due to trace gases and aerosols. The underestimation of the absorption due to aerosols contributes noticeably to the surface flux bias. The impact of clouds on the surface fluxes is estimated by calculating cloud radiative forcing, defined as the difference between the net surface fluxes in all-sky and clear-sky conditions. The comparison of model-simulated and satellite-derived values of cloud radiative forcing over South America demonstrates that the model simulates fairly well its latitudinal variations and annual cycles as compared with SRB data. However, the model overestimates the SRB surface cloud radiative forcing over the tropical region of South America and underestimates it over the extratropical region in both January and July. The comparisons of the incident surface fluxes simulated by the model at the grid points with those measured at three Amazonian observational sites show good agreement at one site and large discrepancies at the other two sites.

Chromocenter numbers in samples of Artemia franciscana from North, Central and South America, and samples of A. persimilis from Argentina are compared. Chromocenters, a good marker for speciation in Artemia, are highly stainable heterochromatic areas with highly repetitive DNA seen in resting nuclei. A probably hybrid zone between the two species was detected in Chilean Patagonia. A. persimilis showed low average chromocenter numbers vs those of A. franciscana and is like the ancestral Mediterranean species in this respect.

We respond to Steppan and Sullivan's (2000) critique of the systematic arguments and recommendations presented by Mares and Braun (1996). We argue that a 'nonstatistical' approach still has a place in systematics as it is currently practiced. Although useful for hypothesis testing, Steppan and Sullivan's (2000) statistical approach should be used with caution when proposing changes in classification.

The relationship among migration, habitat and diet was studied by introducing avian phylogeny in the analysis of austral migration in South America. Austral and Neotropical-Nearctic systems were also compared by re-evaluating available data on Neotropical-Nearctic migrants. Habitat was demonstrated to be a probable determinant of evolutionary patterns of migration beyond the Neotropics. On the other hand, the effect of diet on migration was found negligible.

Using satellite imagery, more than five million square kilometers of the forest and cerrado regions over South America are extensively studied to monitor fires and smoke during the 1985 biomass burning season. The results are characterized for four major ecosystems, namely, 1) tropical rain forest, 2) tropical broadleaf seasonal, 3) savanna/grass and seasonal woods (SGW), and 4) mild/warm/hot grass/shrub (MGS). The spatial and temporal distribution of rims are examined from two different methods using the multispectral Advanced Very High Resolution Radiometer Local Area Coverage data. Using collocated measurements from the instantaneous scanner Earth Radiation Budget Experiment data, the direct regional radiative forcing of biomass burning aerosols is computed. The results show that more than 70% of the fires occur in the MGS and SGW ecosystems due to agricultural practices. The smoke generated from biomass burning has negative instantaneous net radiative forcing values for all four major ecosystems within South America. The smoke found directly over the fires has mean net radiative forcing values ranging from -25.6 to -33.9 W [m.sup.-2]. These results confirm that the regional net radiative impact of biomass burning is one of cooling. The spectral and broadband properties for clear-sky and smoke regions are also presented that could be used as input and/or validation for other studies attempting to model the impact of aerosols on the earth-atmosphere system. These results have important applications for future instruments from the Earth Observing System (EOS) program. Specifically, the combination of the Visible Infrared Scanner and Clouds and the Earth's Radiant Energy System (CERES) instruments from the Tropical Rainfall Measuring Mission and the combination of Moderate Resolution Imaging Spectrometer and CERES instruments from the EOS morning crossing mission could provide reliable estimates of the direct radiative forcing of aerosols on a global scale, thereby reducing the uncertainties in current global aerosol radiative forcing values.

The climatological structure in the upper-tropospheric summertime circulation over South America is diagnosed using a GCM (with and without South American topography), a linear model, and observational data. Emphasis is placed on understanding the origin of observed features such as the Bolivian high and the accompanying 'Nordeste low' to the east. Results from the linear model indicate that these two features are generated in response to precipitation over the Amazon basin, central Andes, and South Atlantic convergence zone, with African precipitation also playing a crucial role in the formation of the Nordeste low. The direct mechanical and sensible heating effects of the Andes are minimal, acting only to induce a weak lee trough in midlatitudes and a shallow monsoonal circulation over the central Andes. In the GCM, the effects of the Andes include a strengthening of the Bolivian high and northward shift of the Nordeste low, primarily through changes in the precipitation field. The position of the Bolivian high is primarily determined by Amazonian precipitation and is little affected by the removal of the Andes. Strong subsidence to the west of the high is found to be important for the maintenance of the high's warm core, while large-scale convective overshooting to the east is responsible for a layer of cold air above the high.

A multilevel limited-area primitive equations model in eta coordinate is used to simulate the effects of the Amazonian latent heat source and the Andean topography on the summer (December, January, February) circulation over the South American region. The observed circulation features, such as the Bolivian high and the trough near the coast of Northeast Brazil in the upper troposphere, the elongated South Atlantic convergence zone (SACZ) oriented northwest to southeast from the southern Amazon region into the Atlantic Ocean, and the subtropical anticyclones in the South Pacific and South Atlantic Oceans in the lower levels are well simulated. Although heating alone produces the SACZ, the mountain and the basic flow put it in the observed position. It is found that regular daily pulses of heating are necessary for the maintenance of the SACZ. The position and intensity of the SACZ change rather substantially from the no-mountain case to the mountain case, thus showing the importance of the effect of the Andes on determining the convergence zone.

Studies of the distribution of beetle populations in southern South America provide insight on the ability of cladistic biogeographical studies to provide information that can be used in conservation studies. The distribution of Cleopatra species of beetles was studied in five areas to show how conservation efforts affect population. A series of area fragmentation is hypothesized based upon the areas of endimism of 7 taxa of beetles.

An estimate of tropospheric ozone concentrations was obtained from the difference in the Total Ozone Mapping Spectrometer (TOMS) data between the high Andes and the Pacific Ocean. From 1979 to 1992 the tropospheric ozone concentration apparently increased by 1.48 ± 0.40 percent per year or 0.21 ± 0.06 Dobson unit per year over South America and the surrounding oceans. An increase in biomass burning in the Southern Hemisphere can account for this trend in tropospheric ozone concentrations., Tropospheric [O.sub.3] plays a key role in regulating the chemical composition and climate of the troposphere (1). The photolysis of [O.sub.3] forms O([D.sup.1]), which reacts with [H.sub.2]O to form reactive [...]

A study focuses on two prochilodontid species, Prochilodus mariae Eigenmann and P. rubrotaeniatus Jardine and Schomburgk. Two nuclear loci that are unlinked to the mtDNA genome are used to assess the findings of Turner and colleagues.

Phylogenetic diversity measures ranks is used to consider factors that can provide additional taxic information such as taxa richness, taxa distributional patterns, area endemicity and complimentary between areas. The use of complementarity allows for preservation of the maximum quantity of taxa in minimal number of protected areas and an example from South America justifies the studies.

A study done on amphibian survey sites at Central and Southern America using solar UV-B radiation exposure to find out whether UV-B radiation is a contributing factor in amphibian declines is reported. The results indicate that the UV index was consistently higher for Central America where species declines were high and severe.

Long sediment cores recovered from the deep portions of Lake Titicaca are used to reconstruct the precipitation history of tropical South America for the past 25,000 years. Lake Titicaca was a deep, fresh, and continuously overflowing lake during the last glacial stage, from before 25,000 to 15,000 calibrated years before the present (cal yr B.P.), signifying that during the last glacial maximum (LGM), the Altiplano of Bolivia and Peru and much of the Amazon basin were wetter than today. The LGM in this part of the Andes is dated at 21,000 cal yr B.P., approximately coincident with the global LGM. Maximum aridity and lowest lake level occurred in the early and middle Holocene (8000 to 5500 cal yr B.P.) during a time of low summer insolation. Today, rising levels of Lake Titicaca and wet conditions in Amazonia are correlated with anomalously cold sea-surface temperatures in the northern equatorial Atlantic. Likewise, during the deglacial and Holocene periods, there were several millennial-scale wet phases on the Altiplano and in Amazonia that coincided with anomalously cold periods in the equatorial and high-latitude North Atlantic, such as the Younger Dryas., There are three major centers of deep atmospheric convection: tropical South America, tropical Africa, and the tropical western Pacific (1). These regions play a dominant role in energizing global atmospheric [...]

Conservation in South America: Problems, Consequences, and Solutions ECOLOGISTS HAVE BEEN AWARE FOR DECADES THAT THE largest known ecosystem in the biosphere. The biospheric concept holds that all life is [...]

Using the NASA/GEOS reanalysis data for 1980-95, the austral-summer stationary eddies in the tropical-subtropical Southern Hemisphere are examined in two wave regimes: long and short wave (wave I and waves 2-6, respectively). The basic structure of the Bolivian high-Nordeste low (BH-NL) system is formed by a shortwave train across South America but modulated by the long-wave regime. The short-wave train exhibits a monsoonlike vertical phase reversal in the midtroposphere and a quarter-wave phase shift relative to the divergent circulation. As inferred from (a) the spatial relationship between the streamfunction and velocity potential and (b) the structure of the divergent circulation, the short-wave train forming the BH-NL system is maintained by South American local heating and remote African heating, while the long-wave regime is maintained by western tropical Pacific heating. The maintenance of the stationary waves in the two wave regimes is further illustrated by a simple diagnostic scheme that includes the velocity-potential maintenance equation (which links velocity potential and diabatic heating) and the streamfunction budget (which is the inverse Laplacian transform of the vorticity equation). Some simple relationships between streamfunction and velocity potential for both wave regimes are established to substantiate the links between diabatic heating and streamfunction; of particular interest is a Sverdrup balance in the short-wave regime. This simplified vorticity equation explains the vertical structure of the short-wave train associated with the BH-NL system and its spatial relationship with the divergent circulation. based upon the diagnostic analysis of its maintenance a simple forced barotropic model is adopted to simulate the BH-NL system with idealized forcings, which imitates the real 200-mb divergence centers over South America, Africa, and the tropical Pacific. Numerical simulations demonstrate that the formation of the BH-NL system is affected not only by the African remote forcing, but also by the tropical Pacific forcing.

It's summer in the southern hemisphere, and the news from scientists who study different penguin populations is both good and bad. First, the good news from South America: Magellanic penguins [...]

Thousands of years old smelting and mining complexes are polluting and posing health risks to regions in South America, Jordan, Africa, and the Middle East. Endangered species lists have biases and limitations from the scientists who put them together according to botanist Mark Burgman of Melbourne University, Australia.