Northwest Argentina Research Articles

New insights on black carbon in pelagic Atlantic sediments

Black carbon (BC) is ubiquitous in pelagic sediments and presumed to have an older radiocarbon age due to long ocean residence times and pre-aging in terrestrial soils. Here, we analyzed sediments from five regions in the subtropical Atlantic Ocean to quantify the black carbon fraction of the total organic carbon pool. Black carbon, derived from the chemothermal oxidation method, comprised between 17 ± 6% of the sedimentary organic carbon in the Northwest Argentina Basin and 65 ± 18% in the Amazon Delta. Black carbon sediment accumulation rates were six times greater in the Sierra Leone Rise (8.4 ± 4.1 mg cm−2 kyr−1) compared to the remote Northwest Argentina Basin (1.3 ± 0.4 mg cm−2 kyr−1), possibly due to enhanced regional atmospheric deposition from annual African grassland fires. The radiocarbon age for BC from subtropical Atlantic sediments were more modern compared to the bulk total organic carbon, and BC source was apportioned as biomass burning byproducts from their stable carbon isotopic signatures and characteristic ratios of polycyclic aromatic hydrocarbons. This study demonstrated that subtropical Atlantic Ocean sediments serve as an important sink for young BC.

The interplay between magma source and geodynamic evolution in porphyry Cu-Au fertility of the Farallon Negro Volcanic Complex, Argentina

Zircon U-Pb, O, Lu-Hf and trace element systematics are used to track the magmatic-hydrothermal evolution and metallogenic potential of porphyry intrusions and associated Cu-Au deposits. We apply this analytical approach to unveil the poorly constrained geological history of the Farallon Negro Volcanic Complex in the Central Andes of northwest Argentina. This complex contains the world-class Au-rich Cu-Au Bajo de la Alumbrera deposit (here dated at 6.9 ± 0.1 to 6.8 ± 0.2 Ma; U-Pb SHRIMP) and a series of barren to weakly mineralized satellite porphyry intrusions, including El Durazno (8.0 ± 0.3 Ma; U-Pb SHRIMP), San Lucas (7.4 ± 0.1 to 7.3 ± 0.1 Ma; U-Pb SHRIMP) and Las Pampitas (7.2 ± 0.2 to 7.0 ± 0.1 Ma, U-Pb SHRIMP). Zircon Hf and O isotope data record a change in magma source from El Durazno (δ18O = 5.7 ± 0.3‰; εHf = −0.3 ± 1.8) to San Lucas, Las Pampitas and Bajo de la Alumbrera (δ18O > 6.7‰, εHf = − 4.0 ± 0.5 to −2.2 ± 1.0). This reflects a switch from a predominantly mantle-derived magma source to a mixed mantle-derived and supracrustal source that homogenized in a lower-crustal magma assimilation, segregation and homogenization (MASH) zone. All intrusions have a hydrous (Eu/Eu* > 0.5, Dy/Yb < 0.3), oxidized (ΔFMQ >1.0, Ce/Ce* > 100) and, therefore, ‘fertile’ zircon trace element signature, despite having variable Cu and Au grades. Likewise, ore-barren extrusive units in the FNVC have an overlapping ‘fertile’ zircon signature, reinforcing the view that zircon-based proxies for fertility may not be useful for mineralization targeting at a district scale. The magmatic evolution of the FNVC was significantly influenced by the tectonic setting, as the onset of regional transpression at ∼8 Ma after a period of localized extension caused pooling of mantle-derived magmas in a lower-crustal MASH zone and build-up of volatiles and metals. The petrogenetic model proposed for the FNVC emphasizes the role of the geodynamic environment and magma evolution in the Cu-Au endowment of Bajo de la Alumbrera

Determination of ptaquiloside in ten species of Pteris in northwestern Argentina

The toxic effect of ferns of the genus of Pteris in bovines is caused by ptaquiloside, the main carcinogenic toxin. In this study, ten species of Pteris fern in different phenologic stages and plant conditions were collected in northwest Argentina. The phytochemical analysis showed the presence of Pt in the recent collected samples (adults and young plants) but not in the herbarium specimens. The results show a great variation of Pt concentration that depends on the phenologic stage, plant condition, and collection site. Pt was measured in 6–4326 μg/g concentration, with a mean concentration of 644 μg/g. No Pt was detected in eight species of Pteris collected from herbarium samples; such results may be a false negative. It is important to notice that analysis of herbarium samples for Pt may not be a reliable method to determine its presence. It is important to further understand the potential toxicity caused by these ferns because of their effect on animals, public health, and the environment.

Molecular characterisation of the potato cyst nematode, Globodera ellingtonae Handoo et al., 2012 (Tylenchida: Heteroderidae) from Bolivia

Summary In 2022, during potato cyst nematode surveys in several departments of Bolivia, the potato cyst nematode Globodera ellingtonae Handoo et al., 2012 was detected for the first time in Bolivia from potato fields located in the Department of Tarija. Cysts and second-stage juveniles of the Bolivian populations were morphologically and morphometrically similar to those of the USA (Oregon and Idaho) and Argentina. Nine new ITS rRNA, 15 COI, 13 cytb gene sequences of G. ellingtonae from ten Bolivian populations were obtained in this study. The phylogenetic analyses of the ITS rRNA and cytb genes showed that all Bolivian sequences clustered together and formed a major clade with other G. ellingtonae sequences from Argentina, Chile and the USA. Molecular results confirmed the hypothesis that the mountain region in southern Bolivia, northwest Argentina and northern Chile could be considered as an ancient centre of origin of G. ellingtonae. The present molecular results suggested that G. ellingtonae was likely introduced into the USA from Chile, rather than from Bolivia and Argentina.

A Model for the Lithospheric Architecture of the Central Andes and the Localization of Giant Porphyry Copper Deposit Clusters

Abstract In the central Andes, giant porphyry copper deposits of similar ages group into discrete geographic clusters that are regularly spaced and aligned within orogen-parallel belts. This clustering highlights how exceptional geologic processes affected localized regions of the lithosphere during mineralization and that the spatial and temporal distribution of giant porphyry deposits is nonrandom. Development of favorable regions of lithosphere for significant metal concentration are linked to the overlap of structural pathways that focus fluid and magma flow from the mantle to upper crust during high-horizontal-compressive-strain events. These structural pathways are notoriously difficult to identify in the field due to their often-subtle surficial manifestations and continental scale. Field mapping at multiple scales in northwest Argentina and southern Peru, as well as regional structural traverses throughout the central Andes, indicates the presence of regional-scale structural corridors 5 to 25 km wide and hundreds of km long that consist of myriad fault planes. The variable width and diffuse surface expression of these corridors is interpreted to reflect the upward propagation of underlying zones of basement weakness through younger supracrustal sequences in the overriding plate. Such structural corridors are (1) apparent at multiple scales of investigation, (2) long-lived, (3) preferentially reactivated though time, and (4) evident in geophysical data sets. This structural architecture formed in response to the interplay of pre-Cenozoic tectonics and the orientation of inherited structural weaknesses. These fault systems persist in the upper crust as steep zones of enhanced permeability that can preferentially reactivate as pathways for ascending hydrous magmas and fluids during major deformation events. Linear orogen-parallel structural belts cogenetic with the magmatic arc provide the first-order control to giant porphyry copper deposit distribution. The second-order control is the intersection of orogen-oblique structural corridors with the orogen-parallel belts, localizing deposit clusters at these intersections. Such regions are inferred to have been zones of deep permeability, with vertical translithospheric pathways activated during high-strain tectonic events that affected the intra-arc stress field.

Genetic diversity and climatic suitability over time of Baetodes huaico (Ephemeroptera: Baetidae)

In the Neotropical region, the genetic diversity and bioclimatic preferences of Ephemeroptera are poorly known mainly due to the lack of studies. We used the 16S rRNA mitochondrial gene to examine the genetic structure of Baetodes huaico, an aquatic insect distributed in the Northwest of Argentina. Also, we performed an ecological niche modeling (ENM) to understand bioclimatic preferences and combine with the genetic data to understand historical dynamic distribution of B. huaico. We found that B. huaico populations are genetically structured into two distinct geographic groups. The ENM showed a distributional shift from south to north through time. Also, we recovered a stable region over time in the Southwest of Tucumán with the highest value of suitability and high genetic diversity; this region was previously proposed as a Pleistocene refuge. Our result suggests that the northern group was stable over time and underwent a recent demographic expansion coincident with a glacial refugium, whereas the southern group could have been affected by climatic fluctuations during. The results emphasize possible climatic influences in genetic population differentiation, and contributes to the knowledge of the genetic diversity of Ephemeroptera from subtropical Argentina laying the groundwork for future work for other freshwater insects in our region.

A Lacustrine Record for the Cretaceous–Paleogene Boundary—Yacoraite Fm., (Northwest Argentina)

The Yacoraite Fm. (Salta rift basin, Argentina) consists of a mixed carbonate–siliciclastic lacustrine succession, interbedded with volcanic ash layers and organised in four third-order stratigraphic sequences. It is one of the few sites in South America that encompass the Cretaceous–Paleogene (K–Pg) transition, the position of which remains debated. Here, samples were collected along a depocentral stratigraphic section that was previously dated by zircon and carbonate U-Pb geochronology. The consistency between zircon and carbonate U-Pb ages, together with an accurate petrographic analysis, allowed the selection of carbonates potentially preserving the original geochemical signature. Accordingly, C-O stable isotopes were analysed from microbialites, oncoids, ooids and lacustrine cements. The available depositional age model from zircon geochronology defined the stratigraphic interval, potentially including the K–Pg transition. Within this interval, carbonates provided negative δ13C values consistent with the negative C anomaly recorded in various K–Pg sites elsewhere. Additionally, spherical particles resembling spherulites related to meteorite impacts were found in two samples. Accordingly, the K–Pg transition could be placed at the top of the second stratigraphic sequence. These findings encourage further investigation of the Yacoraite Fm. to gain insights into the response of South American terrestrial settings to the K–Pg palaeoenvironmental crisis.

Diversity, Genomics and Symbiotic Characteristics of Sinorhizobia That Nodulate Desmanthus spp. in Northwest Argentina.

Desmanthus spp. are legumes with the ability to associate with diverse α-proteobacteria-a microsymbiont-in order to establish nitrogen-fixing root nodules. A previous investigation from our laboratory revealed that the main bacteria associated with Desmanthus paspalaceus in symbiosis in central Argentina (Province of Santa Fe) were quite diverse and belonged to the genera Rhizobium and Mesorhizobium. To achieve a more extensive view of the local microsymbionts associated with Desmanthus spp., we sampled three different sites in Jujuy and Salta, in northwest Argentina. Matrix-assisted Laser-Desorption-Ionization Time-of-Flight mass spectrometry (MALDI-TOF) typing, 16S-rDNA analysis, and genome sequencing demonstrated that the dominant root-nodule microsymbionts belonged to the genus Sinorhizobium, with some sequenced genomes related to Sinorhizobium mexicanum, Sinorhizobium chiapanecum, and Sinorhizobium psoraleae. An analysis of nodA and nodC markers indicated that, in some of the isolates, horizontal gene transfer appeared to be responsible for the lack of congruence between the phylogenies of the chromosome and of the symbiotic region. These results revealed diverse evolutionary strategies for reaching the current Desmanthus-microsymbiont diversity. What is remarkable beside their observed genetic diversity is that the tolerance profiles of these isolates to abiotic stresses (temperature, salt concentration, pH) were quite coincident with the separation of the sinorhizobia according to place of origin, suggesting possible ecoedaphic adaptations. This observation, together with the higher aerial dry-weight matter that some isolates generated in Desmanthus virgatus cv. Marc when compared to the biomass generated by the commercial strain Sinorhizobium terangae CB3126, distinguish the collected sinorhizobia as constituting valuable germplasm for evaluation in local fields to select for more efficient symbiotic pairs.

Modeling potential risk areas of Orthohantavirus transmission in Northwestern Argentina using an ecological niche approach

BackgroundHantavirus Pulmonary Syndrome (HPS) is a rodent-borne zoonosis in the Americas, with up to 50% mortality rates. In Argentina, the Northwestern endemic area presents half of the annually notified HPS cases in the country, transmitted by at least three rodent species recognized as reservoirs of Orthohantavirus. The potential distribution of reservoir species based on ecological niche models (ENM) can be a useful tool to establish risk areas for zoonotic diseases. Our main aim was to generate an Orthohantavirus risk transmission map based on ENM of the reservoir species in northwest Argentina (NWA), to compare this map with the distribution of HPS cases; and to explore the possible effect of climatic and environmental variables on the spatial variation of the infection risk.MethodsUsing the reservoir geographic occurrence data, climatic/environmental variables, and the maximum entropy method, we created models of potential geographic distribution for each reservoir in NWA. We explored the overlap of the HPS cases with the reservoir-based risk map and a deforestation map. Then, we calculated the human population at risk using a census radius layer and a comparison of the environmental variables’ latitudinal variation with the distribution of HPS risk.ResultsWe obtained a single best model for each reservoir. The temperature, rainfall, and vegetation cover contributed the most to the models. In total, 945 HPS cases were recorded, of which 97,85% were in the highest risk areas. We estimated that 18% of the NWA population was at risk and 78% of the cases occurred less than 10 km from deforestation. The highest niche overlap was between Calomys fecundus and Oligoryzomys chacoensis.ConclusionsThis study identifies potential risk areas for HPS transmission based on climatic and environmental factors that determine the distribution of the reservoirs and Orthohantavirus transmission in NWA. This can be used by public health authorities as a tool to generate preventive and control measures for HPS in NWA.

Climatic niche convergence through space and time for a potential archaeophyte (Acacia caven) in South America

Based on the niche conservatism hypothesis, i.e. the idea that niches remain unchanged over space and time, climatic niche modelling (CNM) is a useful tool for predicting the spread of introduced taxa. Recent advances have extended such predictions deeper in time for plant species dispersed by humans before the modern era. The latest CNMs successfully evaluate niche differentiation and estimate potential source areas for intriguing taxa such as archaeophytes (i.e., species introduced before 1492 AD). Here, we performed CNMs for Acacia caven, a common Fabaceae tree in South America, considered an archaeophyte west of the Andes, in Central Chile. Accounting for the infraspecific delimitation of the species, our results showed that even when climates are different, climatic spaces used by the species overlap largely between the eastern and western ranges. Despite slight variation, results were consistent when considering one, two, or even three-environmental dimensions, and in accordance with the niche conservatism hypothesis. Specific distribution models calibrated for each region (east vs west) and projected to the past, indicate a common area of occupancy available in southern Bolivia—northwest Argentina since the late Pleistocene, which could have acted as a source-area, and this signal becomes stronger through the Holocene. Then, in accordance with a taxon introduced in the past, and comparing regional vs continental distribution models calibrated at the infraspecific or species level, the western populations showed their spread status to be mostly in equilibrium with the environment. Our study thus indicates how niche and species distribution models are useful to improve our knowledge related to taxa introduced before the modern era.

Evolution of the Earth's magnetic field strength in northwestern Argentina during the last two millennia: Towards the improvement of south American geomagnetic paleosecular variation curve

A magnetic mineralogy and absolute geomagnetic intensity study was carried out on prehispanic ceramic fragments from the Southern Andes region (Northwest Argentina). Magnetic susceptibility vs. temperature curves and alternating field demagnetization treatments were applied to select the most suitable samples for the absolute archaeointensity experiments. A total of 66 samples were analyzed following the Thellier modified by Coe protocol, including cooling rate corrections and potential mitigation of the magnetic anisotropy effect. Thirty-eight samples (out of 66) belonging to nine pottery fragments yielded reliable absolute intensity determinations The new data, accompanied by associated radiocarbon ages, were integrated into previously published data in order to construct an improved paleosecular variation curve for South America. The highest quality data covers only the last 1000 years. The general variation patterns show good agreement with global geomagnetic prediction models. This updated regional curve may be used as the reference curve for archaeomagnetic dating in the major part of South America (Brazil, Argentina, Chile, Uruguay and Bolivia), even though caution should be paid for the areas and time periods poorly covered by data.

Temporal and Spatial Change in Vegetation and Its Interaction with Climate Change in Argentina from 1982 to 2015

Studying vegetation change and its interaction with climate change is essential for regional ecological protection. Previous studies have demonstrated the impact of climate change on regional vegetation in South America; however, studies addressing the fragile ecological environment in Argentina are limited. Therefore, we assessed the vegetation dynamics and their climatic feedback in five administrative regions of Argentina, using correlation analysis and multiple regression analysis methods. The Normalized Difference Vegetation Index 3rd generation (NDVI3g) from Global Inventory Monitoring and Modeling Studies (GIMMS) and climatic data from the Famine Early Warning Systems Network (FEWS NET) Land Data Assimilation System (FLDAS) were processed. The NDVI of the 1982–2015 period in Argentina showed a downward trend, varying from −1.75 to 0.69/decade. The NDVI in Northeast Argentina (NEA), Northwest Argentina (NWA), Pampas, and Patagonia significantly decreased. Precipitation was negatively correlated with the NDVI in western Patagonia, whereas temperature and solar radiation were positively correlated with the NDVI. Extreme precipitation and drought were essential causes of vegetation loss in Patagonia. The temperature (73.09%), precipitation (64.02%), and solar radiation (73.27%) in Pampas, Cuyo, NEA, and NWA were positively correlated with the NDVI. However, deforestation and farming and pastoral activities have caused vegetation destruction in Pampas, NEA, and NWA. Environmental protection policies and deforestation regulations should be introduced to protect the ecological environment. The results of this study clarify the reasons for the vegetation change in Argentina and provide a theoretical reference for dealing with climate change.

“Ways of Doing” Pottery in the Cajón Valley (Argentine Northwest) during the First Centuries AD

This article presents an example of ceramic circulation and exchange networks in the southern Andean region during the first centuries AD, derived from the study of the production, circulation, and consumption of the pottery assemblages found in the villages of Cardonal and Bordo Marcial, located in the Cajón Valley in Catamarca, Argentina. Our analysis of the technical, morphological, and design aspects of the ceramics suggested six morphological groups using three representation techniques and 16 paste recipes; we also found that locally manufactured vessels were used together with ceramics of nonlocal origin in similar domestic contexts. In addition, the foreign ceramic materials suggest that there were networks of interaction between Cardonal and Bordo Marcial and other regions, such as the southern Puna, the Hualfín Valley, the Rosario-Lerma Basin, and the San Francisco Valley in northwestern Argentina.

Effects of Goat Manure Fertilization on Grain Nutritional Value in Two Contrasting Quinoa (Chenopodium quinoa Willd.) Varieties Cultivated at High Altitudes

In this study, the effects of goat manure fertilization (2, 4, 8, and 12 Tn/ha) on the grain yield, organic compounds, and mineral composition of two quinoa varieties (CICA-17 and Regalona Baer) were evaluated under field conditions in Northwest Argentina. The results indicate that fertilization improved the quinoa grain yield and total protein content. Low manure doses positively affected the fatty acid (FA) profile, and significant changes were determined for the monounsaturated (MUFA) and polyunsaturated (PUFA) fatty acid contents of CICA-17 and on the saturated fatty acid (SFA) contents of R. Baer seeds. The amino acid contents were positively affected in CICA-17 and negatively in R. Baer. Soluble sugars (glucose, fructose, and sucrose), major elements (K, Si, P, Mg, Ca, and Na), minor elements (Fe, Mn, Al, Zn, and Cu), and ultratrace elements (Cr and Li) were detected and discussed in terms of their impact on human nutrition and health. Conclusively, manure addition affected some essential amino acids, the desaturase activity, the n6:n3 and SFA/UFA ratios, the atherogenic index, soluble sugars, and mineral content, and the fatty acid metabolism of each variety was differently affected, especially the C16 and C18 desaturase activity, which responded differently to various manure doses. Manure addition is a promising alternative to improve the nutritional quality and functionality of quinoa grains, but the response is not linear.

Petrography and geochemistry of successions from northwest Bolivia

A complete section of Paleozoic sedimentary rocks has been sampled in northwest Bolivia to investigate compositional changes based on petrographic but mainly geochemical data. Studies of Paleozoic succession in southern Peru, northern Chile and northwest Argentina allowed to decipher the paleotectonic history of the region for the Paleozoic (e.g. compilations in Bahlburg et al., 2009). However, a few is only known about the area geographically in between. We focus here on an area in the vicinity of the capital La Paz, where the Paleozoic belongs paleogeographically to the so-called ‘altiplano’ and the ‘Cordillera Oriental del Norte’ and tectonically to the ‘Faja de Huarina del Norte’. The objective of the study is, hence, to establish a first complete stratigraphic insight of the Paleozoic to enable further studies on key formations or horizons. While the abovementioned areas to the north and south do reflect in the sedimentary record the emergence of a continental arc during the Ordovician, followed by a significant tectonic quiescence during the late Silurian and Devonian and succeeded by the evolution of a second active margin with a continental arc during the late Paleozoic, these events are not visible in the Bolivian samples which is sandwiched between the westerly Arequipa Massif and the eastern Sunsas belt, both composed of mainly metamorphic rocks.The Paleozoic section in northwest Bolivia shows highly recycled quartz-arenites of Ordovician age followed by Silurian and Devonian successions mainly composed of subangular to surrounded detritus, moderately sorted, devoid of significant typical metamorphic detritus. During the late Paleozoic, the rocks tend to a larger variability, partly even poorly sorted, higher amount of angular grains and the occurrence of volcaniclastic debris. Geochemically the same trend can be observed, with strongly recycled successions during the Ordovician (Zr/Sc 20–200) followed by moderately recycled rocks (mainly Zr/Sc 10–20100) with typical trace element composition for unrecycled upper continental crust (UCC). During the Permian, sediments which are less weathered and slightly less fractionated in their overall geochemical composition, have been deposited. The geochemistry may point to the evolution of late Paleozoic volcanism, recorded in overlying, but however, Triassic rocks. Significant increase or even typical UCC values of compatible elements or ratios are absent besides Cr and Ni increase in Ordovician rocks. The absence of any significant input of arc related detritus can be explained by not effective sediment dispersal system to transport arc related detritus into the depositional area. The low compositional and low to moderate textural maturity throughout the entire post-Ordovician stratigraphy implies relatively proximal sources and insignificant intra-basinal recycling. This together with the absence of metamorphic detritus, allows in proposing thick homogeneous sedimentary successions with low or no metamorphic overprint as major sources. Those covered possibly the today exposed metamorphic successions of the aforementioned basin surroundings. Sedimentary or any other lithologies older than the Ordovician and younger than Mesoproterozoic are nearly unknown in the region, besides one exception (Chilla beds; Bahlburg et al., 2020). Those hypothetical deposits would be at this stage of knowledge the best explanation.

Nutritional status of adults in Northwest Argentina: an observational study

Background: Northwestern Argentina (NWA) is a region with geographic, ethnic, socioeconomic, and cultural characteristics that set it apart from the rest of the country. The present study aimed to analyze both the anthropometry and nutritional status of adults in this region and establish its recent secular trend.

Emergence and clonal spread of KPC-2-producing clinical Klebsiella aerogenes isolates in a hospital from northwest Argentina.

Introduction. Klebsiella aerogenes is a nosocomial pathogen associated with drug resistance and healthcare-associated infections.Gap Statement. K. aerogenes is associated with hospital-acquired infections with the ability to acquire mechanisms of resistance to reserve antimicrobials; its clinical behaviour has been poorly documented.Objective. We proposed to investigate an outbreak of carbapenem-resistant K. aerogenes in a hospital that persisted for 4 months.Methods. The primary aim was to evaluate the molecular characteristics and the clonal relationships among the isolates. We characterized isolates by polymerase chain reaction (PCR) and pulsed-field gel electrophoresis (PFGE). The information was integrated with clinical and epidemiological data.Results. Fourteen strains were disseminated in an intensive care unit and different wards at the hospital. The overall mortality was 42.8 %, and mortality attributed to infection was 21.4 %; strains showed high rates of resistance to most of the antimicrobials tested and carried bla KPC-2, bla SHV-2 and bla CTXM-15 genes. PFGE analysis indicated 2 PFGE groups; 12/14 isolates were associated with subgroup A and were likely to be primarily responsible for the first isolation and subsequent dissemination. The outbreak characteristics data showed prolonged hospitalization and previous use of antibiotics as potential risk factors.Conclusion. We consider that it is essential to perform phenotypic and genotypic identification of early genetic resistance mechanisms in K. aerogenes isolates, not only from infection sites but also from colonization, to prevent the spread of these multidrug-resistant (MDR) isolates.

Genotype-dependent responses of Andean and Coastal quinoa to plant population density for yield and its physiological determinants in Northwest Argentina

Context In quinoa, similar yields are found under a wide range of plant population densities due to its phenotypic plasticity. Aims This study aimed to identify optimal plant population densities for achieving attainable yields, in relation to the most adapted genotype for a given environment. Methods Andean (RQ252 and RQ420) and Coastal (Titicaca and Puno) genotypes were tested at conventional (14 plants/m2) and low (7 plants/m2) plant population densities, in Dry Valley and Highland mega-environments for 2 years. Key results More than 64% of total variation was explained by genotype, location, and interaction effects for grain yield, biomass, and harvest index. For these variables, the genotype × location × plant population density term presented the highest percentage of variation among triple and quadruple interaction terms. In the Highlands, grain yields decreased with plant population density for Andean genotypes (30–40%), in contrast to lower reductions for Coastal genotypes (9–20%). In the Dry Valleys, no effect of plant population density was found for all genotypes. In the Highlands, reductions in biomass and harvest index explained grain yield response, in parallel with increases in small grain percentage of up to 16% when frosts came early, related to uneven maturity at low plant population density. Conclusions Attainable yields in Northwest Argentina were achieved by exploring local adaptation and response to plant population density of Andean genotypes in the Highlands, in contrast to stable yields of Coastal genotypes through locations and plant population densities. Implications Understanding genotype-dependent responses to plant population density according to Northwest Argentina mega-environments can reduce yield gaps in quinoa production and refine breeding strategies.

Environmental factors determining the diversity of darkling beetles (Coleoptera: Tenebrionidae) in arid, high-altitude environments in Northwestern Argentina

Factors influencing the diversity of tenebrionid beetles in arid, high-altitude environments in the northwest of Argentina are little-known. Using pitfall traps and suction sampling in 30 sites, we collected these beetles in Altos Andes (AA) and Puna (PU) ecoregions and evaluated how local and regional factors influenced their assemblages. During each sampling date, we registered variables related to climate, vegetation, and soil in each sampling site. In total, we recorded 270 individuals from 21 species, richness of species was higher in PU than in AA, but without a statistically significant difference. Twelve species were present exclusively in PU, while two in AA. Tenebrionid assemblages in both ecoregions had different dominant species, in PU, Psectrascelis cariosicollis while Epipedonota interandina in AA. Beta diversity between ecoregions was moderate and we recorded a high beta diversity and high turnover of species in each ecoregion. The geographical distance between the sites influenced the similarity of the assemblages inside and between ecoregions, therefore, an increase in the geographical distance between sites determined a decrease in the similarity of the assemblages. The increase in elevation of the sampled sites did not produce significant changes in the abundance and richness of Tenebrionidae. There is no individual factor responsible for the darkling beetle communities structuration in these high-altitude environments. Different combinations of both local (soil and vegetation) and regional (climate and geographical distance) environmental factors together explain the ecoregional tenebrionid assemblages. We suggest including them among the focus groups in conservation studies to evaluate anthropogenic activities in this area.

Dos nuevas especies de la subfamilia Asclepiadoideae (Apocynaceae) en la provincia de Salta, Argentina

Recent botanical explorations carried out in the northwest of Argentina allowed us to find two new species of Apocynaceae, one of them, which belongs to the genus Petalostelma, was found in the Garrapatas Private Reserve, General Güemes, in the Mountain Chaco region, the other, of the genus Philibertia, was found in the Quebrada de Escoipe, Chicoana, in inter-Andean valleys. In this contribution both taxa are described and illustrated.