Northeastern Paraguay Research Articles

A new species of Phalotris (Serpentes, Colubridae, Elapomorphini) from Paraguay

A new species of Phalotris from the nasutus group, Phalotris shawnellasp. nov., is described. It can be distinguished from the other members of the group by having the following combination of characters: 1) fifth supralabial in contact with parietal, 2) vertebral stripe present, 3) yellowish nuchal collar (2 or 3 dorsal scales long), 4) dull reddish color of head, 5) broad, solidly or near solidly dark, lateral bands, 6) red-orange ventral scales lightly and irregularly spotted with black mainly on the posterior half of the body and 7) a bilobed, extremely asymmetrical hemipenis, with enlarged, curved, lateral spines. The species is only known from a recent specimen collected in the Cerrado zone of northeastern Paraguay at Rancho Laguna Blanca, San Pedro department, and two photographic records of live specimens from this and an additional locality. Limited ecological data based on observations of a captive individual, and a wild record, are provided, and a conservation assessment is performed for this extremely limited range Paraguayan endemic snake.

A long-lived active margin revealed by zircon U–Pb–Hf data from the Rio Apa Terrane (Brazil): New insights into the Paleoproterozoic evolution of the Amazonian Craton

We present the first regional in-situ zircon U–Pb–Hf isotopic data from metaigneous and metasedimentary rocks from the Paleo- to Mesoproterozoic Rio Apa Terrane (RAT), a crustal fragment outcropping in the central-western Brazil and north-eastern Paraguay. These new ages and Hf isotopic data delineate three magmatic events, which record the construction of the temporally and isotopically distinct Western and Eastern Terranes of the RAT. The Western Terrane comprises the 2100–1940 Ma Porto Murtinho Complex and the 1900–1840 Ma Amoguijá Belt, which both define a crustal reworking array in εHfT-time space evolving from a precursor source with Hf TDM age of ca. 2700 Ma. The 1800–1720 Ma Caracol Belt constitutes the Eastern Terrane and yields suprachondritic εHfT signatures up to +7.1, indicating significant juvenile input. The metasedimentary Amolar Group and Rio Naitaca Formation in the Western Terrane have maximum depositional ages of 1850–1800 Ma and subchondritic εHfT signatures down to −5.7, similar to the underlying basement of the Amoguijá Belt. In the Eastern Terrane, the Alto Tererê Formation has a maximum depositional age of 1750 Ma and mostly suprachondritic εHfT signatures, similar to magmatic rocks of the underlying Caracol Belt. Together, the new igneous and detrital zircon age and Hf isotopic data record a temporal and spatial transition from 2100 to 1840 Ma crustal reworking in the west to more juvenile magmatism at 1800–1720 Ma in the east. This transition is interpreted to reflect convergent margin magmatism associated with periods of subduction zone advance and retreat in an accretionary orogenic setting. Comparison of the εHfT-time signature of the RAT with the Amazonian Craton suggest penecontemporaneous development, with the Western and Eastern Terranes of the RAT being correlative with the Ventuari-Tapajós and Rio Negro-Juruena Province of the Amazonian Craton, respectively. Our new data also reveal that the εHfT signatures of the RAT are distinct from the Maz terrane, which refutes the MARA Block hypothesis.

Sigmodontine community and species responses to El Niño and precipitation in different levels of forest degradation.

Few studies have focused on rodent communities at the margins of an ecoregion or the limits of species’ distributions, where the community may be more sensitive to extrinsic variables, both biotic and abiotic. This study evaluates sigmodontine rodent species diversity and overall abundance, and variation associated with climatic variables, in three locations with differing levels of habitat degradation. The study was conducted in northeastern Paraguay, near the western limit of the Upper Parana Atlantic Forest and near the distributional limits of the three most abundant species in the study sites. Three mark-recapture grids were established and classified as least, moderately and most-degraded based on an analysis of several vegetation parameters. The grids were sampled for five consecutive nights, six times during two years. Shannon diversity and overall abundance were calculated for each sample. Monthly Multivariate ENSO Index and rainfall values were obtained from publicly available resources. Product-moment correlations were calculated between community and climatic parameters, including cumulative values for the climatic variables. The same correlations were calculated for the three common sigmodontine species. 1,632 captures were recorded, representing 13 sigmodontine species. Species richness in the samples (one session on one grid) varied from four to seven. Akodon montensis, Hylaeamys megacephalus and Oligoryzomys nigripes were the three most abundant species. In general, species diversity was negatively correlated with ENSO index, precipitation and precipitation anomaly, including cumulative one- to six-month cumulative values of each. Total sigmodontine abundance was positively correlated with the climatic variables. However, these correlations were not uniform among the three levels of habitat degradation, nor did the three abundant species show similar correlation patterns. The three most abundant species are each near their distributional limits, whereas several less abundant species have distributions that extend well beyond the study area. This somewhat counterintuitive result bears further investigation in other sites at ecoregional margins, to determine whether it is a commonly observed pattern, or an exception. Overall sigmodontine abundances were generally reflective of Akodon montensis abundance, which generally correlated with precipitation (including cumulative amounts). Our analyses of these longitudinal data showed two major effects on sigmodontine species diversity and population. First, they are impacted by habitat and secondly, they are affected by climate (ENSO, precipitation). However, individual species are not impacted similarly. Akodon montensis abundances primarily were correlated with abiotic (climatic) variables, and the correlations were consistent across habitats (biotic factors). In contrast, Hylaeamys megacephalus abundance was correlated with climatic variables in two habitats, but not the moderately-degraded habitat, and Oligoryzomys nigripes abundance was not correlated with climate in the most-degraded habitat.

A new species of Mimosa section Mimosa (Leguminosae) from the Paraguayan Cerrado

Mimosa schininii (Leguminosae), a new species from the Amambay region, in the Cerrado ecoregion of northeastern Paraguay, is described and illustrated. This new species belongs to Mimosa L. section Mimosa series Mimosa subseries Brevipedes Barneby, and is similar to M. brevipes Benth. and M. sceptrum Barneby, but differs from them by shorter inflorescence, secondary leaflets venation pattern and fruit dehiscence. This new entity resembles, in some characters, other subseries of series Mimosa, such as Mimosa section Mimosa series Mimosa subseries Pedunculosae (Benth.) Barneby and Hirsutae (Benth.) Barneby, but can be distinguished adequately from them by vegetative, floral, and carpological characters. Illustration, distribution map, and a key to distinguish M. schininii from close relatives are provided.

On the distribution of the Brazilian porcupine Coendou prehensilis (Erethizontidae) in Colombia

Abstract The Brazilian porcupine Coendou prehensilis is distributed from northwestern South America to northeastern Paraguay and northwestern Argentina. In Colombia, it is present mainly in the Caribbean, the eastern Llanos and the Andean regions, which correspond to six of the biogeographical provinces of the country. Its presence in the Colombian Amazon region has been suggested based on records from neighboring countries such as Ecuador, Venezuela and Brazil. However, no voucher specimens or additional evidence that corroborates the presence of the species in that region of Colombia is known. Based on the review of specimens deposited in Colombian collections, analyses of photographic records, and the literature, the presence of the species in the Colombian Amazon is confirmed, and its distribution in the country updated. Overall, we found 36 records of C. prehensilis in Colombia, of which seven correspond to the Colombian Amazon (four photographic records and three specimens). A genetic analysis based on cytochrome-b suggests that this species is genetically uniform throughout its distributional range. These new records make C. prehensilis the most widespread species of the genus among natural regions and biogeographic provinces of Colombia. Other species are restricted to one or two provinces.

Burrowing Owls Athene cunicularia (Strigidae) respond with increased vigilance to calls of the Curl-crested Jay Cyanocorax cristatellus (Corvidae) in the Paraguayan Cerrado

Nesting Burrowing Owls ( Athene cunicularia) in the Cerrado of northeastern Paraguay were observed to show increased vigilance in response to Curl-crested Jay ( Cyanocorax cristatellus ) calls. To test whether this reaction was species specific, a playback experiment was conducted using jay calls, a native passerine and three exotic passerines, and responses of the owls to the recordings were measured. The results indicated that the owls responded with increased vigilance only to calls of the Curl-crested Jay. It is hypothesized that the interaction between the two species may be related to competition for dietary resources initiating a greater aggressive response in the diurnal jay due to its more limited foraging time, compared to the nocturnal and diurnal owls. The vigilant response of the owls may thus be related to avoidance of potentially costly aggressive interactions with jays.

Rhinella scitula (Caramaschi & Niemeyer, 2003) (Amphibia: Anura: Bufonidae): New distribution records

Rhinella scitula is a small frog belonging to the R. margaritifera group that is found in southwestern and central Mato Grosso do Sul, Brazil, and in the provinces of Amambay and Concepcion in Paraguay. We extend the distribution of the species across the north and the southeast prior distribution limit, and provide an updated map. The distribution of R. scitula encompasses mainly areas with seasonal forests and mountainous landscape in central-western Brazil and northeastern Paraguay.

Carbonatites and primary carbonates in the Rio Apa and Amambay regions, NE Paraguay

In the Rio Apa and Amambay regions, north-eastern Paraguay (NPAA), potassic, alkaline-carbonatitic rocks (138–139Ma) predate the eruption of tholeiitic flood basalts (133±1Ma). These rocks, mainly outcropping as dykes or ring-like complexes, intrude a Cambro-Ordovician carbonate platform and Precambrian metamorphic rocks along with their Silurian and Permo-Carboniferous sediments. The main rock-types range from basanite to trachyte and trachyphonolite (and intrusive equivalents) to carbonatite, in addition to glimmeritic and pyroxenitic veins. Geological and geophysical evidence indicate that the NPAA magmatism is related to extensional tectonics, like the Early Cretaceous alkaline-carbonatitic complexes from central-eastern Paraguay (127±1Ma) and the eastern magmatic occurrences of the Paraná Basin.Oxygen and carbon isotope compositions (whole rocks and carbonates) vary from values close to the field of continental lithospheric mantle, or that of primary carbonatites, up to values typical of a hydrothermal environment. An isotope exchange model implies that the main isotope variations, ranging from a magmatic (e.g., 1200°C) to a low temperature (<400°C) environment, involved fluids with CO2/H2O ratios between 0.8 and 1.0. In particular, the OC isotopic variations, in combination with the La vs La/Yb ratios, suggest an increasingly higher level of carbonate in the silicate liquids, with increasing evolution, i.e., basanite→phonotephrite→trachyphonolite–phonolite (trachyte)→carbonatite. SrNd isotopes show that the carbonatites are mantle derived without significant crustal contamination and that they can be related to isotopically enriched sources where newly formed veins (enriched component) and peridotite matrix (depleted component) underwent differing isotopic evolution.TDM model ages for NPAA range from 1.2 to 2.3Ga. Considering that in the whole Paraná Basin isotopically distinct K-alkaline and tholeiitic magmas were generated following the enrichment of the subcontinental mantle mainly between 1.0 and 2.3Ga (Paleo-Mesoproterozoic events), the mantle sources preserved the isotopic heterogeneities over long time periods, suggesting a non-convective, i.e., lithospheric, mantle source beneath different cratonic or intercratonic areas.

Morphometrics of Cerrado Birds from the Reserva Natural Laguna Blanca (Ne Paraguay)

Abstract Smith P., Onley D., Northcote-Smith E, Atkinson K. 2012. Morphometrics of cerrado birds from the Reserva Natural Laguna Blanca (NE Paraguay). Ring 34: 51-67. Morphometric data are provided for 204 individuals of 61 species from the Reserva Natural Laguna Blanca in Departamento San Pedro in north-eastern Paraguay. Measurements were taken according to Svensson (1984). Data for 2 cerrado endemic species, 2 species of global conservation concern and 5 species of national conservation concern are presented. These are the first published biometric data for birds of the Paraguayan cerrado.

The Rio Apa Craton in Mato Grosso do Sul (Brazil) and northern Paraguay: Geochronological evolution, correlations and tectonic implications for Rodinia and Gondwana

The Rio Apa cratonic fragment crops out in Mato Grosso do Sul State of Brazil and in northeastern Paraguay. It comprises Paleo-Mesoproterozoic medium grade metamorphic rocks, intruded by granitic rocks, and is covered by the Neoprotero- zoic deposits of the Corumbaand Itapocumi Groups. Eastward it is bound by the southern portion of the Paraguay belt. In this work, more than 100 isotopic determina- tions, including U-Pb SHRIMP zircon ages, Rb-Sr and Sm-Nd whole-rock determina- tions, as well as K-Ar and Ar-Ar mineral ages, were reassessed in order to obtain a complete picture of its regional geological history. The tectonic evolution of the Rio Apa Craton starts with the formation of a series of magmatic arc complexes. The oldest U-Pb SHRIMP zircon age comes from a banded gneiss collected in the northern part of the region, with an age of 1950 23 Ma. The large granitic intrusion of the Alumiador Batholith yielded a U-Pb zircon age of 1839 33 Ma, and from the southeastern part of the area two orthogneisses gave zircon U-Pb ages of 1774 26 Ma and 1721 25 Ma. These may be coeval with the Alto Tereremetamorphic rocks of the northeastern corner, intruded in their turn by the Bao´a das Garcas granitic rocks, one of them yielding a zircon U-Pb age of 1754 49 Ma. The original magmatic protoliths of these rocks involved some crustal component, as indicated by the Sm-Nd T DM model ages, between 1.9 and 2.5 Ga. Regional Sr isotopic homogenization, associated with tectonic deformation and medium-grade metamorphism occurred at approximately 1670 Ma, as suggested by Rb-Sr whole rock reference isochrons. Finally, at 1300 Ma ago, the Ar work indicates that the Rio Apa Craton was affected by widespread regional heating, when the temperature probably exceeded 350°C. Geographic distribution, age and isotopic signature of the lithotectonic units suggest the existence of a major suture separating two different tectonic domains, juxtaposed at about 1670 Ma. From that time on, the unified Rio Apa continental block behaved as one coherent and stable tectonic unit. It correlates well with the SW corner of the Amazonian Craton, where the medium-grade rocks of the Juruena-Rio Negro tectonic province, with ages between 1600 and 1780 Ma, were reworked at about 1300 Ma. Looking at the largest scale, the Rio Apa Craton is probably attached to the larger Amazonian Craton, and the actual configuration of southwestern South America is possibly due to a complex arrangement of allochthonous blocks such as the Arequipa, Antofalla and Pampia, with different sizes, that may have originated as disrupted parts of either Laurentia or Amazonia, and were trapped during later collisions of these continental masses.

Population genetic structuring in pacu (Piaractus mesopotamicus) across the Paraná-Paraguay basin: evidence from microsatellites

The Paraná-Paraguay basin encompasses central western Brazil, northeastern Paraguay, eastern Bolivia and northern Argentina. The Pantanal is a flooded plain with marked dry and rainy seasons that, due to its soil characteristics and low declivity, has a great water holding capacity supporting abundant fish fauna. Piaractus mesopotamicus, or pacu, endemic of the Paraná-Paraguay basin, is a migratory species economically important in fisheries and ecologically as a potential seed disperser. In this paper we employ eight microsatellite loci to assess the population structure of 120 pacu sampled inside and outside the Pantanal of Mato Grosso. Our main objective was to test the null hypothesis of panmixia and to verify if there was a different structuring pattern between the Pantanal were there were no physical barriers to fish movement and the heavily impounded Paraná and Paranapanema rivers. All loci had moderate to high levels of polymorphism, the number of alleles varied from three to 18. The average observed heterozygosity varied from 0.068 to 0.911. After the Bonferroni correction three loci remained significant for deviations from Hardy-Weinberg, and for those the frequency of null alleles was estimated. F ST and R ST pairwise comparisons detected low divergence among sampling sites, and differentiation was significant only between Paranapanema and Cuiabá and Paranapanema and Taquari. No correlation between genetic distance and the natural logarithm of the geographic distance was detected. Results indicate that for conservation purposes and for restoration programs small genetic differences detected in the Cuiabá and Paranapanema rivers should be taken in consideration.

Reciprocal altruism, rather than kin selection, maintains nepotistic food transfers on an Ache reservation

Cooperation among relatives is often regarded as evidence of kin selection. Yet altruism not requiring shared genes can also evolve among relatives. If characteristics of relatives (such as proximity, familiarity, or trust) make kin preferred social partners, the primary causes of nepotistic biases may reside principally in direct fitness payoffs from cooperation rather than indirect fitness payoffs acquired from aiding collateral kin. We consider the roles of kin selection and reciprocal altruism in maintaining nepotistic food transfers on an Ache reservation in northeastern Paraguay. Households do not primarily direct aid to related households that receive larger comparative marginal gains from food intake as we would predict under kin selection theory. Instead, (1) food transfers favor households characterized by lower relative net energy production values irrespective of kinship ties, (2) households display significant positive correlations in amounts exchanged with each other, suggesting contingency in food transfers, and (3) kinship interacts with these positive correlations in amounts households exchange with each other, indicating even stronger contingency in sharing among related households than among unrelated households. While kin are preferred recipients of food aid, food distributions favor kin that have given more to the distributing household in the past rather than kin that would benefit more from the aid. Such discrimination among kin accords better with reciprocal altruism theory than with kin selection theory.

Distribution, abundance, and conservation of Vinaceous Amazons (Amazona vinacea) in Argentina and Paraguay

ABSTRACT Vinaceous Amazons (Amazona vinacea) are endemic to the Atlantic forest of southeastern Brazil, eastern Paraguay, and the province of Misiones in Argentina. We searched for Vinaceous Amazons throughout the western part of its range in Argentina and Paraguay during 1639 days of fieldwork from 1997 to 2006. These parrots have disappeared from most areas where they were historically recorded in these countries, and are now limited to a few sites in northeastern Paraguay and central Misiones (Argentina). We estimate the minimum remaining populations at 220 individuals in Paraguay and 203 individuals in Argentina. Important sites for the species are (1) the farming area from San Pedro to Tobuna (Misiones, Argentina) and (2) the Itaipú reserves complex and Reserva Natural Privada Itabó (Paraguay). In our surveys, Vinaceous Amazons were absent from the largest tracts of forest in Misiones, and were most often observed feeding, roosting, and nesting in small forest remnants and in agricultural areas that included forest fragments and isolated trees. Threats to amazons in these areas include nest poaching, forest clearing, and being shot as a crop pest. We confirmed 40 Vinaceous Amazons kept as pets in 35 homes between San Pedro and Tobuna. Environmental education and law enforcement are urgently needed to reduce threats in populated areas, and subsistence farmers need technical and logistical support to slow or stop the conversion of forest into cropland. Finally, additional study is needed to determine this amazon's habitat preferences, nest site requirements, and demography in different habitats. El loro vinoso (Amazona vinacea) es endémico del bosque Atlántico del sudeste de Brasil, este de Paraguay, y la provincia de Misiones en Argentina. Buscamos esta especie durante 1639 días de trabajo de campo de 1997 a 2006, a lo largo de la porción oeste de su distribución, en Argentina y Paraguay. A. vinacea ha desaparecido de la mayor parte de las áreas donde ha sido registrada históricamente en estos paises, y permanece sólo en algunos pocos sitios del noroeste de Paraguay y del centro de Misiones (Argentina). Estimamos el tamaño mínimo de las poblaciones remanentes en 220 individuos en Paraguay y 203 individuos en Argentina. Los sitios importantes para la especie son: (1) la zona rural de San Pedro a Tobuna (Misiones, Argentina) y (2) el complejo de reservas de Itaipú y la Reserva Natural Privada Itabó (Paraguay). A. vinacea no fue encontrada en los tractos más grandes de bosque durante nuestras prospecciones en Misiones. Mayormente fue observada alimentándose, durmiendo y nidificando en pequeños remanentes boscosos y en hábitats antropogénicos. Las amenazas en estos hábitats incluyen robo de pichones de los nidos, deforestación, y cacería por daño a cultivos. Confirmamos la existencia de 40 ejemplares cautivos como mascotas en 35 hogares de San Pedro y Tobuna. Para reducir las amenazas se requieren urgentemente educación ambiental y fortalecimiento legal en las áreas pobladas. Es necesario proveer de apoyo técnico y logístico a los agricultores de subsistencia para reducir la conversión de bosques a cultivos. Finalmente, estudios futuros deberían tratar la preferencia de hábitat del loro, sus requerimientos de nidificación, y su demografía en distintos hábitats.

Identification of BSPRY as a Novel Auxiliary Protein Inhibiting TRPV5 Activity

Transient receptor potential vallinoid 5 (TRPV5) and TRPV6 are the most Ca2+-selective members of the TRP superfamily and are essential for active Ca2+ (re)absorption in epithelia. However, little is known about intracellular proteins that regulate the activity of these channels. This study identified BSPRY (B-box and SPRY-domain containing protein) as a novel factor involved in the control of TRPV5. The interaction between BSPRY and TRPV5 by GST pull-down and co-immunoprecipitation assays was demonstrated. BSPRY showed co-localization with TRPV5 in mouse kidney. Expression of BSPRY resulted in a significant reduction of the Ca2+ influx in Madin-Darby Canine Kidney cells that stably express TRPV5 without affecting channel cell-surface abundance. Finally, BSPRY expression in kidney was increased in 25-hydroxyvitamin D3-1alpha-hydroxylase knockout mice, suggesting an inverse regulation by vitamin D3. Together, these results demonstrate the physiologic role of the novel protein BSPRY in the regulation of epithelial Ca2+ transport via negative modulation of TRPV5 activity.

Stevia rebaudiana – A Functional Component for Food Industry

AbstractStevia (Stevia rebaudiana Bertoni) is a natural herb native of northeastern Paraguay, cultivated as a cash crop in number of countries. There appears to be no large-scale mechanized production of stevia due to difficulties in producing the crop through seeds. The stevia leaves in its powder form is green in color, 10 – 15 times sweeter than sucrose with after taste bitterness. However, there are no studies reported on the use of stevia in food product formulation and development and other related aspects. Considering its sweetness potentia-lities and possible health implications, an investigation was focused and the results indicated that gram of stevia sweetness was perceived to be equivalent to 20g of sucrose and produced more than 40 seconds of sweetness stimulus. Per cent nutrient composition of stevia was found to be impressive with 269 Kcal, 9.8 g of protein, ash at 10.5 g and crude fiber at 18.4 g. Mineral composition indicated that presence of fairly good amount of calcium (464 mg), iron (...

História de um país inexistente: O Pantanal entre os séculos XVI e XVIII

Based on the author’s recently completed doctoral thesis at the University of São Paulo, História de um país inexistente by Maria de Fátima Costa documents the history of the world’s largest wetland, a floodplain covering more than 39,000 square miles of southwestern Brazil and northeastern Paraguay: the Pantanal. Initially christened Laguna de los Xarayes by early Spanish explorers who mistook the seasonal floodplain for a large and fabulous lake, the region would not be conceived as the Pantanal (literally “the wetland”) until the middle of the eighteenth century with the signing of the Treaty of Madrid. Costa’s book not only documents the history of the Pantanal, but more especially describes its invenção, or rather, the manner in which early explorers “invented” the region by imposing their own images, conceptions, and designs upon it (p. 22). In examining how the Pantanal was understood by the historical actors themselves, Costa draws upon sixteenth-, seventeenth-, and eighteenth-century travel accounts as well as the iconography of the period (including various maps and sketches that have been reproduced in full-color throughout the book). Since relatively little academic work is available on this region in either Spanish or Portuguese (much less in English), Costa has supplemented her primary sources with an assortment of regional materials, including local histories from Argentina, Paraguay, and the Brazilian states of São Paulo and Mato Grosso.The book begins with a short historical synthesis of the Pantanal, from the incursion of Spanish conquistadors at the beginning of the sixteenth century to the end of the eighteenth century when royal officials demarcated the region’s borders. Following this short historical prelude, Costa turns to the heart of her work: the travel accounts of those who journeyed through the Pantanal during the colonial period. Beginning with narratives by Ulrico Schmidl, Ruy Díaz de Guzmán, and Alvar Núñez Cabeza de Vaca, Costa examines how early images of the region spread throughout Europe, influencing the cartography of the period with tales of the fabulous Laguna de los Xarayes, an earthly paradise of immense wealth. Costa then contrasts these early accounts with subsequent narratives by Luso-Brazilian explorers who describe the region in pragmatic terms as they explain how to navigate through a fantastically inhospitable wetland. According to Costa, these two contrasting perspectives would briefly coexist until the second half of the eighteenth century when surveying expeditions would establish a more realistic picture of the region.A history of both the real and the imagined, Costa’s book is well researched and gracefully written, making an important contribution to the history of a region and period that have largely been neglected in the current literature.

History of Arachis Including Evidence of A. hypogaea L. Progenitors

Abstract The genus Arachis L. probably originated as a geocarpic form of Stylosanthes Sw. on the old Brazilian Shield in what is now southwestern Mato Grosso do Sul, Brazil or northeastern Paraguay. Several mid-Tertiary uplifts followed, raising the penaplain and the ancient Arachis with it. The two most ancient species are still found in the area today, comprising the taxonomic section Trierectoides Krapov. and W.C. Gregory. From this beginning the other species and sections evolved as the shield was uplifted and eroded by the tributaries. The more advanced species, but still quite ancient, are in sections Extranervosae Krapov. and W.C. Gregory, Triseminatae Krapov. and W.C. Gregory, Heteranthae Krapov. and W.C. Gregory, and Erectoides Krapov. and W.C. Gregory. The evolution and distribution of these species was a slow process because of the geocarpic fruit, which would have limited movement to an estimated 1 m/yr. However, after several geologic uplifts, flowing water likely played a large part in the distribution of the Arachis species. From the early materials evolved the more advanced species in sections Caulorrhizae Krapov. and W.C. Gregory, Procumbentes Krapov. and W.C. Gregory, and Rhizomatosae Krapov. and W.C. Gregory. The evolution of species in the most advanced section Arachis, which includes the cultivated peanut, has overlapped the distribution of other sections, and the distribution of some members of section Arachis has been strongly affected by man. There is evidence that development of the major domesticated species, A. hypogaea L., did not occur in the wild, and extensive supportive data now exist on two other cultivated Arachis species still grown in Brazil for food and medicinal use—A. villosulicarpa Hoehne and A. stenosperma Krapov. and W.C. Gregory. Arachis hypogaea seeds likely moved to China and Africa with ancient mariners well before the time of Columbus. After discovery of the Western Hemisphere and the conquests, many forms of A. hypogaea spread to Africa and Asia. Later the cultivated peanut traveled in slave ships from Africa into the southeastern U.S., Central America, and northeast South America, thus returning modified germplasm to the Americas. No evidence has been found that native Americans brought the peanut, along with corn (Zea mays L), to the east coast of North America in pre-Columbian times.

Geochemistry and CO isotopes of the Chiriguelo carbonatite, northeastern Paraguay

The Chiriguelo carbonatitic complex crops out in northeastern Paraguay at the central western fringe of the stratoid volcanic rock-types of the Serra Geral Formation. At least three stages of emplacement of carbonatitic rocks can be distinguished: a C1 main søvite, a C2 alvikite and a C3 ferrocarbonatite. A C4 stage may be inferred from the diffusion of late quartz, barite, and uranpyrochlore. The geologic, petrographic, and geochemical traits show environmental conditions similar to volcanic ones, and point to a vertical zonation in the fenitization processes versus a K-enrichment near the surface. The CO isotopic data suggest a loss of isotopically light water, along with a loss of Sr, following the hydrothermal recrystallization process(es) of the main søvite. Such losses may be related to low-temperature ( e.g. down to 25°C) weathering processes.