Regions Of Central South America Research Articles

Variability of Winter Frosts in Central South America: Quantifying Mechanisms with Decision Trees

AbstractAgricultural production in Central South America (CSA) is substantially influenced by frost events. This study characterises and quantifies the physical processes leading to frost conditions in CSA from 1979 to 2022, focusing on three innovative aspects: regional frost properties, a novel multi-parametric upper-level jet description, and the quantification of underlying mechanisms through decision trees (DTs). The regionalisation analysis identifies five homogeneous frost regions in CSA. In all regions, the events tend to occur more frequently during the La Niña phase. Moreover, a significant increase in the frequency of widespread frost events has been observed in the Argentinean Pampas during the study period, primarily due to negative trends in minimum temperatures. Furthermore, the synoptic mechanisms triggering frosts, such as cold fronts and post-frontal anticyclones enhanced by subsidence near the subtropical jet (STJ) entrance, have not shown major long-term changes. To describe the jets, we compute six parameters for the STJ and seven for the polar front jet, including latitude, intensity, height, tilting, longitudinal extent, and branch number. DTs are used to identify key jet parameters linked to frost events, such as the latitude, longitudinal extent, and tilt of the Atlantic STJ. Frost likelihood increases when the STJ is north of 31°S, and the extension of the Atlantic STJ is longer than 35° and has a negative tilt. Finally, DTs focused on the onset and end of events highlight geopotential height anomalies and STJ extension as critical variables. These DTs provide concise and accessible information for agricultural decision-makers in CSA.

A single origin for the widely distributed B chromosomes of the gladiator frog Boana albopunctata

Abstract B chromosomes are supernumerary elements that have a wide taxonomic distribution among eukaryotes. Although they are dispensable, they can acquire mechanisms to be overrepresented in the next generation and therefore avoid being eliminated. These elements have been discovered in < 2% of the karyotyped anurans. B chromosomes were described for Argentine and Brazilian populations of Boana albopunctata, a Neotropical tree frog widely distributed in the central region of South America. We assessed the distribution of B chromosomes in this species via cytogenetic studies of 365 specimens from Argentina, Brazil and Paraguay. We found that 101 individuals carried B chromosomes, with striking differences in their frequency of occurrence among localities. Our findings might be related to the evolutionary dynamics of these elements. Microdissection and chromosome painting experiments demonstrated sequence similarity between B chromosomes from localities that are > 1000 km apart, showing the most widely distributed B chromosome system known for anurans. The B chromosome system of B. albopunctata might help to fill the general knowledge gap for these elements in anurans compared with other vertebrates.

Frost risk in canola and carinata as a function of sowing date in the agricultural central region of South America

AbstractCrop cycles in spring canola (Brassica napus L.) and carinata (Brassica carinata A. Braun) are controlled by temperature and photoperiod. In the central region of South America, which accounts for 90% of South American rapeseed crop production, farmers seek to sow as early as possible to maximize yield even though early sowing dates expose crops to a higher probability of frost occurrence that had not been quantified before. Our objective was to model phenology for one spring cultivar of canola (‘Rivette’) and one of carinata (‘Avanza 641’) and assess the probability of frost occurrence during flowering and grain filling in the central region of South America. For the estimation of frost risk, we modeled phenology resulting from 15 April to 15 August sowing dates at 12 locations (from 31.16° to 34.20° S latitude). We assumed that the critical period spans from 100 to 500 growing degree days (GDD) after flowering. Under early sowing dates, carinata tends to have a longer cycle (200 GDD more than canola) although both crops had a similar cycle length under a late sowing date. Predicted and observed flowering dates showed an average difference of 1.6 and 0.95 d for canola and carinata, respectively. Carinata has a lower probability of suffering frost events, and early sowing dates result in a greater exposure to frost damage. The results of this work will enable farmers and stakeholders to know the potential frost risk when defining a sowing date for canola and carinata.

Integrative Revision about Parental Care and Life History in Canids, with Emphasis on the Chrysocyon brachyurus Species (Illiger, 1815)

The canidae are a family of the Mammalia class represented by two extinct subfamilies called Hesperocyoninae and Borophaginae. Also by the still existing subfamily called Caninae which includes all living canids (dogs, wolves, jackals, coyotes and foxes). Divided into 14 genus and 34 species distributed on all continents. They have carnivorous and omnivorous feeding, being pack animals or essentially solitary animals meeting only during the breeding season where many species develop parental care for their offspring. Among these species the maned wolf (Chrysocyon brachyurus) stands out. Being the largest South American canid an omnivorous, generalist and opportunistic species whose diet varies seasonally consuming a great diversity of fruits and small vertebrates. They are widely distributed in the areas of fields and savannahs in the central region of South America. However it is noted that there was a considerable decrease in the original portion of their habitat in addition to the illegal hunting to use the animals' fur being run over on roads and diseases are the most frequent causes that do not contribute to the conservation of this species. Therefore the species is listed in Appendix II of CITES and is considered Vulnerable (VU). As Chrysocyon brachyurus represents one of the main predators of its biome playing a fundamental role for its balance. Its preservation is essential and further studies are needed for better understanding and formation of strategies that contribute to its conservation.

Ecology of Pheidole oxyops Forel, 1908, a dominant ant in neotropical savannas

Pheidole oxyops is a common and widely spread species in the central region of South America. Despite its ecological importance, relatively little is known about its habitat preferences, population dynamics and natural history. Here we provide information about the diet, daily foraging schedule, nest size and densities, and on the influence of habitat on the dynamics of P. oxyops colonies in southeastern Brazil. We found that P. oxyops is a habitat generalist, occurring in grasslands, savannas and forests. Although mean nest densities did not differ between the habitats we surveyed, the greatest densities were detected in the savanna plots, where up to 175 nests ha−1 were found. Pheidole oxyops presented an essentially predatory/scavenger habit, feeding on arthropod prey and especially on termites. Ant workers foraged during the day and the night at temperatures ranging from 14 to 28 °C. Nest mortality over a period of 1 year was positively related to initial nest densities, indicating a density-dependent regulation of the population. Nest growth rates were higher for small-sized—and thus presumably younger—nests than for large-sized nests. Overall, these life-history data reinforce the view that P. oxyops is a species typical of the Cerrado savannas, and a numerically and behaviourally dominant ant.

DNA barcoding for identification of anuran species in the central region of South America.

The use of COI barcodes for specimen identification and species discovery has been a useful molecular approach for the study of Anura. Here, we establish a comprehensive amphibian barcode reference database in a central area of South America, in particular for specimens collected in Mato Grosso do Sul state (Brazil), and to evaluate the applicability of the COI gene for species-level identification. Both distance- and tree-based methods were applied for assessing species boundaries and the accuracy of specimen identification was evaluated. A total of 204 mitochondrial COI barcode sequences were evaluated from 22 genera and 59 species (19 newly barcoded species). Our results indicate that morphological and molecular identifications converge for most species, however, some species may present cryptic species due to high intraspecific variation, and there is a high efficiency of specimen identification. Thus, we show that COI sequencing can be used to identify anuran species present in this region.

Growing diversity supports radiation of an Ellipsomyxa lineage into the Amazon freshwater: Description of two novel species parasitizing fish from Tapajós and Amazon rivers

Species of the genus Ellipsomyxa Køie, 2003, parasitize mostly marine and brackish fish around the world. In the present study, we describe two novel species of Ellipsomyxa: Ellipsomyxa plagioscioni n. sp. parasitizing the gall bladder of Plagioscion squamosissimus (Sciaenidae), a freshwater fish but commonly found in brackish water in the Amazonian estuarine environment; and Ellipsomyxa paraensis n. sp. infecting Cichla monoculus (Cichlidae), a strictly freshwater fish. The host specimens were caught from the Amazon and Tapajós rivers, in the municipal region of Santarém, in the State of Pará, Brazil. The study was performed using a combination of morphological, biological, and SSU rDNA-based phylogeny, which suggested that marine transgressions of the Miocene epoch, in the central region of South America, were a pathway for the adaptation and radiation of these cnidarian parasites in the freshwater environment. Both disporic plasmodia and mature myxospores were found floating freely in the bile. Mature myxospores from both species were ellipsoidal in the valvular and sutural views, with thin smooth valves elongated in the direction perpendicular to the plane of the transverse sutural line. Ellipsomyxa plagioscioni n. sp. myxospores measured 11.1 (10.2–12.8) µm in length and 6.6 (5.6–7.6) µm in width. Two pyriform polar capsules discharging on opposite sides, some distance from both the sutural line and the spore ends, measured 3.8 (3.2–4.4) µm in length and 2.8 (2.3–3.3) µm in width, with 5–6 coil polar tubules. Ellipsomyxa paraensis n. sp. myxospores measured 11.5 (10.5–12.4) µm in length and 7.5 (6.6–8.6) µm in width. Two pyriform polar capsules which discharged on opposite sides some distance from both the sutural line and spore ends, measured 3.2 (2.1–3.9) µm in length and 2.6 (2.0–3.3) µm in width, with 2–3 coil polar tubules. Valvular protrusions were observed, associated with the tips of the polar capsules. Molecular analysis based on the SSU rDNA sequences indicated that the two novel Ellipsomyxa species were distinct from all other sequences deposited in the GenBank database. The phylogenetic trees clustered E. plagioscioni n. sp. as a basal species of a lineage of the marine/estuarine Ellipsomyxa, while E. paraensis n. sp. clustered together with other Amazonian species.

Climate and evolutionary history define the phylogenetic diversity of vegetation types in the central region of South America.

In South America the biogeographic history has produced different biomes with different vegetation types and distinct floras. As these vegetation types may diverge in evolutionary histories, we analysed how alpha and beta phylogenetic diversity vary across them and determine the main drivers of variation in phylogenetic diversity. To this end, we compiled a list of 205 sites and 1222 tree species spread over four biomes and eight vegetation types in central South America. For each site we evaluated six measures of evolutionary alpha diversity (species richness, phylogenetic diversity sensu stricto and the standardized effect size of phylogenetic diversity, mean phylogenetic distance and mean nearest taxon distance) and beta diversity (phylogenetic Sorensen's similarity). We checked the influence of spatial and environmental variables using generalized least squares models. The greatest phylogenetic differentiation was found between west and east of central South America, mainly between the Chaco communities and the other vegetation types, suggesting that species found in this biome come from different lineages, comparing with the others vegetation types. Our results also showed a clustered phylogenetic structure for the Dry Chaco woodlands, which may be associated with harsh environmental conditions. In addition to historical process, climatic conditions are the main drivers shaping phylogenetic patterns among the distinct vegetation types. Understanding patterns of phylogenetic diversity and distribution can greatly improve conservation planning and management since it allows the conservation of unique biome characteristics.

Barcoding Analysis of Paraguayan Squamata

Paraguay is a key spot in the central region of South America where several ecoregions converge. Its fauna (and specifically its herpetofauna) is getting better studied than years before, but still there is a lack of information regarding molecular genetics, and barcoding analyses have proven to be an excellent tool in this matter. Here, we present results of a barcoding analysis based on 16S rRNA gene sequences, providing valuable data for the scientific community in the region. We based our fieldwork in several areas of Paraguay. We analyzed 249 samples (142 sequenced by us) with a final alignment of 615 bp length. We identified some taxonomic incongruences that can be addressed based on our results. Furthermore, we identify groups, where collecting efforts and research activities should be reinforced. Even though we have some blanks in the geographical coverage of our analysis—and there is still a lot to do towards a better understanding of the taxonomy of the Paraguayan herpetofauna—here, we present the largest genetic dataset for the mitochondrial DNA gene 16S of reptiles (particularly, Squamata) from Paraguay, which can be used to solve taxonomic problems in the region.

Review of Temnomastax Rehn & Rehn, 1942 (Orthoptera, Caelifera, Eumastacidae, Temnomastacinae)

Temnomastax is the commonest genus of monkey grasshoppers in the central region of South America. Herein the revision of this genus is presented. Three new species are described, Temnomastax descampsi Olivier sp. nov., Temnomastax monnei Olivier sp. nov., and Temnomastax otavioi Olivier sp. nov. Temnomastax chiquitos syn. nov. is proposed as a new synonym of Temnomastax borellii. Three morphological groups are proposed: the Beni group composed of Temnomastax beni; the Latens group composed of T. borellii, T. hamus, T. latens and T. monnei sp. nov.; and the Tigris group composed of T. descampsi sp. nov., T. otavioi sp. nov., T. ricardoi and T. tigris. Identification keys, biological and distribution data are provided.

THREATS TO THE BIODIVERSITY OF THE BRAZILIAN PANTANAL DUE TO LAND USE AND OCCUPATION

Abstract The Pantanal is a wetland located in the central region of South America (150,355 km2), mainly in Brazil (nearly 140,000 km2), touching Paraguay and Bolivia. The floodplain is fed by the Paraguay River and its tributaries, where the headwater of the rivers is located on the surrounding upland. Only 40% of this plateau retains its natural vegetation. Although the natural habitats of the Pantanal are still considered well preserved, retaining 80% of the vegetation cover, the biome faces environmental and socioeconomic threats that affect its biodiversity. The seasonal flux of the rivers is a fundamental ecological element for regional biodiversity. Habitat alteration and deforestation have affected terrestrial and aquatic habitats and their associated wildlife. This work identifies and analyses the threats to biodiversity considering land use, based on research experience in the region plus field work. Based on this, it discusses a strategic action plan for the biome’s biodiversity.

Predicting the potential global distribution of diosgenin-contained Dioscorea species

BackgroundDiosgenin, mainly extracted from wild diosgenin-contained Dioscorea species, is a well-known starting material of steroidal and contraceptive drugs. However, due to large market demand and increasingly ecological damage, wild Dioscorea species resources available have been gradually declining. Therefore, identification of new potential ecological distribution of diosgenin-contained Dioscorea species is necessary for diosgenin production.MethodsIn this study, a large occurrence dataset (1808 data points) of diosgenin-contained Dioscorea species was obtained from Eastern Asia, Southern North America and Southern Africa. Along with the data for six critical environmental parameters and one soil factor, Geographic Information System for Global Medicinal Plant was applied to predict the potential suitable distribution of Dioscorea species.ResultsThe results showed that the potential distribution of these Dioscorea species covered a wide field, and that new ecological suitability areas were mainly distributed in the central region of South America, the southern part of the European and coastal region of Oceania. Jackknife test indicated that annual precipitation and annual mean radiation were the important climatic factors controlling the distribution of Dioscorea species.ConclusionsThe suitable areas and critical climatic factors will serve as a useful guide for diosgenin-contained Dioscorea species conservation and cultivation in ecological suitable areas.

Exposure of Fishery Resources to Environmental and Socioeconomic Threats within the Pantanal Wetland of South America

The huge Pantanal wetland, located in the central region of South America, mainly in Brazil, formed by the Upper Paraguay River Basin,...

Energetics of southeastern Pacific cut-off lows

The existence of cut-off lows (COLs) over South Pacific and South America is often associated with adverse weather events such as intense precipitation over the central region of South America, frost episodes in southern Brazil and the development of Andes lee cyclones and intense cyclones over the southern coast of Brazil. Despite this importance, the formation and maintenance mechanisms of the COLs are not well understood. To detail the significant variability in terms of the eddy kinetic energy equation for fifty cases of COLs that formed over the southeastern Pacific Ocean is the aim of this study. Only the cases of COLs that formed over the ocean and remained there during most of their life were chosen. The main terms of the equation [ageostrophic flux convergence (AFC), baroclinic conversion (BRC) and barotropic conversion (BRT)] were calculated using the 6-hourly gridded data from the National Centers for Environmental Prediction/Department of Energy reanalysis. The formation mechanism of the COLs was associated with BRC and AFC. During the midlife period, the BRC term converted eddy kinetic energy to eddy potential energy and the AFC had a positive contribution until 6 h after the midlife point. In the dissipation phase, the BRC term remained positive and AFC became negative. The BRT extracted kinetic energy from the COL during the entire life cycle. The AFC term was the most important in all phases of the cut-off lifetime, and it was the responsible for extending the cut-off lifetime while the others terms were negatives.

Ammonia emissions in tropical biomass burning regions: Comparison between satellite-derived emissions and bottom-up fire inventories

Vegetation fires emit large amounts of nitrogen compounds in the atmosphere, including ammonia (NH3). These emissions are still subject to large uncertainties. In this study, we analyze time series of monthly NH3 total columns (molec cm−2) from the IASI sounder on board MetOp-A satellite and their relation with MODIS fire radiative power (MW) measurements. We derive monthly NH3 emissions estimates for four regions accounting for a major part of the total area affected by fires (two in Africa, one in central South America and one in Southeast Asia), using a simplified box model, and we compare them to the emissions from both the GFEDv3.1 and GFASv1.0 biomass burning emission inventories. In order to strengthen the analysis, we perform a similar comparison for carbon monoxide (CO), also measured by IASI and for which the emission factors used in the inventories to convert biomass burned to trace gas emissions are thought to be more reliable. In general, a good correspondence between NH3 and CO columns and the FRP is found, especially for regions in central South America with correlation coefficients of 0.82 and 0.66, respectively. The comparison with the two biomass burning emission inventories GFASv1.0 and GFEDv3.1 shows good agreements, particularly in the time of the maximum of emissions for the central South America region and in the magnitude for the region of Africa south of the equator. We find evidence of significant non-pyrogenic emissions for the regions of Africa north of the equator (for NH3) and Southeast Asia (for NH3 and CO). On a yearly basis, total emissions calculated from IASI measurements for the four regions reproduce fairly well the interannual variability from the GFEDv3.1 and GFASv1.0 emissions inventories for NH3 but show values about 1.5–2 times higher than emissions given by the two biomass burning emission inventories, even when assuming a fairly long lifetime of 36 h for that species.

A New Species ofMolinema(Nematoda: Onchocercidae) in Bolivian Rodents and Emended Description ofLitomosoides esslingeriBain, Petit, and Diagne, 1989

We report the distribution of 2 species of filarioid nematodes occurring in different hosts in the central region of South America. Molinema boliviensis n. sp. was recorded as a parasite of sigmodontine and echymyid rodents in Bolivia, and Litomosoides esslingeri was recorded in sigmodontine and ctenomyid rodents from Bolivia and Argentina. Molinema boliviensis n. sp. shares several similarities with other species reported in spiny rats; however, it can be easily differentiated by the presence of a flat anterior end, gradually tapering lappets and a tubercle present in posterior end, a short, uniform buccal capsule, an oval-shaped vagina vera, and a ratio of spicules of 1:1.44. An account for the morphological variability of L. esslingeri is presented that allows the identification of the buccal capsule, the tail tip in females, and the shape of spicules as reliable diagnostic traits. A complete set of head papillae is also described. The finding of these parasites in phylogenetically unrelated hosts suggests that host capture may be a frequent phenomenon in these filarioids. Researchers should focus efforts in surveying mammals within the same ecological guild to understand the distribution and host specificity of these nematodes.

Diversity of popular names of the main medicinal plants (MP) used by the local people in the central region of South America

The diversity of the main „medicinal plants names“-(MP) most used by the local people in the central region of South America (21 municipalities of the Southwest of Mato Grosso, Brazil) were investigated in 2005. Firstly, the popular names of the main MP were obtained. Three „reference“ people in each of the 21 municipalities were indicated as informants by their pairs (21×3=63 informants). In every region, the informants (63) listed 503 MP. The list presented from 42 to 137 different MP names by municipality. Two presented more than 100 MP names while one presented less than 50, and the remaining 18 municipalities between 50–100 MP. One way to measure the diversity of MP „within and between municipalities“ was through „recurrent indications“ of same MP. To this RI index was used (RI=Sum of the number of MP names cited by the three informants of each municipality divided by the number of different MP names cited in this municipality). The lowest RI value was 1.085 and the highest 1.693, indicating that the list of MP names was more distinct in the municipalities with lower RI and more similar in the municipalities with higher RI. The average number of MP listed per county (municipality) was 107. Only one MP(urtigão) was mentioned unanimously by the three informants of a same municipality. In general, the recurrence of indications (RI) was low. It's revealing a great informative, cultural and ethnoknowledge diversity in respect of medicinal plants used by these communities in central region of South America.

Assays for the cultivation of two native plant species largely utilized as aphrodisiac in the central region of South America

Assays for the cultivation of two native plant species largely utilized as aphrodisiac in the central region of South America

Characteristics of the equatorial electrojet current in the central region of South America

Abstract We describe here for the first time the morphology of the equatorial electrojet (EEJ) in the Central American Sector based on an analysis of the geomagnetic field components from six stations distributed on both sides of the dip equator along the 60°W geographic longitude sector. Diurnal and latitudinal variations in the horizontal and vertical components are shown to follow the Chapman model of EEJ. The horizontal component vector due to the ionospheric current aligned itself close to magnetic north, with a mean Declination of 10°W (ranging from 9°W to 14°W). There was a significant counter-electrojet effect before sunrise at stations close to the dip equator, suggesting late reversal of solar-quiet (S q) electric field in the morning hours. The observed variations in the magnetic meridional current did not seem to be associated with EEJ currents. The centre of the electrojet was around 0.25°S of the dip equator in the morning hours and shifted gradually to 1.5°S by the evening hours. Magnetic storms occurring during the midday hours produced an exceptionally large decrease in the H (horizontal component) field at stations close to the dip equator.

Sinopsis de las Thelypteridaceae de Brasil central y Paraguay

Aunque las Thelypteridaceae han sido tratadas en forma actualizada para Norteamérica, Mesoamérica, Guayanas, Ecuador, Perú, Argentina y sur y sudeste de Brasil, la región central de Sudamérica aún requería de una puesta al día. Con este motivo se estudiaron las especies de Thelypteridaceae de Paraguay y Brasil central, encontrándose 55 taxones, entre especies e infraespecíficos, comprendidos en dos géneros y cinco subgéneros. Se brinda una clave general para los grupos y sus entidades, con datos de distribución, ecología e ilustraciones. Se incluyen una nueva combinación, nuevos sinónimos y extensiones de área, se resuelven problemas nomenclaturales y discuten cuestiones taxonómicas. Pese a que el área estudiada es muy amplia se destaca que el número total de especies es menor respecto a las regiones conocidas en concordancia con la menor riqueza de ambientes.