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Access to water has been and remains one of humanity’s greatest challenges. Especially in arid plains exposed to significant climatic fluctuations and future global change trends. In the past and present, local communities of the arid plains of central-western Argentina (i.e., Guanacache Lagoons, Cuyo region) have developed multiple strategies to manage water supply problems. The aims of this study are: i) to characterize the different water harvesting technologies (pre-Hispanic and modern) used, and ii) to compare the small local strategies of water harvesting (bottom-up solutions) with the large centralized projects (top-down solutions). On the one hand, we show the transformations of these technologies over time, and the challenges faced by inhabitants in the context of climate change trends. On the other hand, we analyze the role of the state through hydraulic policies and projects implemented by the provincial states over the last two centuries and how this impacted the study area. This review is based on a historical and archaeological bibliography, and recent publications about the region, including articles based on our ethnographic fieldwork. Our results demonstrate the valuable experience accumulated by local populations in water harvesting methods, particularly in areas where groundwater is deep and saline, and shows the adaptability of these technologies in contexts of increasing scarcity. We considered that local indigenous knowledge can largely contribute to the sustainable management of water resources. This study might be useful for decision-makers and water managers in drylands around the world to find and equitable approach that combines technical advances with local knowledge.

Abstract By incompletely understood mechanisms, type 2 (T2) inflammation present in the airways of severe asthmatics drives the formation of pathologic mucus which leads to airway mucus plugging. Here we investigate the molecular role and clinical significance of intelectin-1 (ITLN-1) in the development of pathologic airway mucus in asthma. Through analyses of human airway epithelial cells we find that ITLN1 gene expression is highly induced by interleukin-13 (IL-13) in a subset of metaplastic MUC5AC+ mucus secretory cells, and that ITLN-1 protein is a secreted component of IL-13-induced mucus. Additionally, we find ITLN-1 protein binds the C-terminus of the MUC5AC mucin and that its deletion in airway epithelial cells partially reverses IL-13-induced mucostasis. Through analysis of nasal airway epithelial brushings, we find that ITLN1 is highly expressed in T2-high asthmatics, when compared to T2-low children. Furthermore, we demonstrate that both ITLN-1 gene expression and protein levels are significantly reduced by a common genetic variant that is associated with protection from the formation of mucus plugs in T2-high asthma. This work identifies an important biomarker and targetable pathways for the treatment of mucus obstruction in asthma.

Abstract Genome-wide association studies (GWAS) have become well-powered to detect loci associated with telomere length. However, no prior work has validated genes nominated by GWAS to examine their role in telomere length regulation. We conducted a multi-ancestry meta-analysis of 211,369 individuals and identified five novel association signals. Enrichment analyses of chromatin state and cell-type heritability suggested that blood/immune cells are the most relevant cell type to examine telomere length association signals. We validated specific GWAS associations by overexpressing KBTBD6 or POP5 and demonstrated that both lengthened telomeres. CRISPR/Cas9 deletion of the predicted causal regions in K562 blood cells reduced expression of these genes, demonstrating that these loci are related to transcriptional regulation of KBTBD6 and POP5. Our results demonstrate the utility of telomere length GWAS in the identification of telomere length regulation mechanisms and validate KBTBD6 and POP5 as genes affecting telomere length regulation.

Polycystic Ovary Syndrome (PCOS) is a complex hormonal disorder that is associated with heightened metabolic risks. While oxidative stress (OS) is known to play a role in PCOS, the precise nature of the relationship between PCOS and increased OS remains not entirely understood. Combined oral contraceptives (COCs) are the first-line treatment to regulate menstrual cycles and androgen levels, but their impact on oxidative stress requires further study. We conducted a transcriptomic analysis using RNAseq and assessed the levels of various oxidative stress (OS) markers in serum samples from women with PCOS and controls and whether they were using combined oral contraceptives (COCs), including enzymatic activities, FRAP, and 8-isoprostane (8-iso). A total of 359 genes were differentially expressed in women with PCOS compared to control women. Genes differentially expressed were enriched in functions related to inflammation and, interestingly, oxidative stress response. In controls, 8-iso levels were increased in women using COCs, whereas in women with PCOS, 8-iso levels were reduced in those using oral contraceptives (191.1 ± 97 vs. 26.4 ± 21 pg/mL, p: p = 0.06) and a negative correlation between GSH and hyperandrogenism in women with PCOS (r = −0.89, p = 0.01). These results reveal the presence of lipid peroxidation in women with PCOS, which was modified by the use of COCs, providing new insights into the pathophysiology of PCOS in the Chilean population.

Abstract Background Albuterol is the first-line asthma medication used in diverse populations. Although DNA methylation (DNAm) is an epigenetic mechanism involved in asthma and bronchodilator drug response (BDR), no study has assessed whether albuterol could induce changes in the airway epithelial methylome. We aimed to characterize albuterol-induced DNAm changes in airway epithelial cells, and assess potential functional consequences and the influence of genetic variation and asthma-related clinical variables. Results We followed a discovery and validation study design to characterize albuterol-induced DNAm changes in paired airway epithelial cultures stimulated in vitro with albuterol. In the discovery phase, an epigenome-wide association study using paired nasal epithelial cultures from Puerto Rican children (n = 97) identified 22 CpGs genome-wide associated with repeated-use albuterol treatment (p

Abstract Atopic dermatitis (AD) is a common inflammatory skin condition and prior genome-wide association studies (GWAS) have identified 71 associated loci. In the current study we conducted the largest AD GWAS to date (discovery N = 1,086,394, replication N = 3,604,027), combining previously reported cohorts with additional available data. We identified 81 loci (29 novel) in the European-only analysis (which all replicated in a separate European analysis) and 10 additional loci in the multi-ancestry analysis (3 novel). Eight variants from the multi-ancestry analysis replicated in at least one of the populations tested (European, Latino or African), while two may be specific to individuals of Japanese ancestry. AD loci showed enrichment for DNAse I hypersensitivity and eQTL associations in blood. At each locus we prioritised candidate genes by integrating multi-omic data. The implicated genes are predominantly in immune pathways of relevance to atopic inflammation and some offer drug repurposing opportunities.

The blood–brain barrier (BBB) represents a crucial interface between the circulatory system and the brain. In Drosophila melanogaster, the BBB is composed of perineurial and subperineurial glial cells. The perineurial glial cells are small mitotically active cells forming the outermost layer of the nervous system and are engaged in nutrient uptake. The subperineurial glial cells form occluding septate junctions to prevent paracellular diffusion of macromolecules into the nervous system. To address whether the subperineurial glia just form a simple barrier or whether they establish specific contacts with both the perineurial glial cells and inner central nervous system (CNS) cells, we undertook a detailed morphological analysis. Using genetically encoded markers alongside with high-resolution laser scanning confocal microscopy and transmission electron microscopy, we identified thin cell processes extending into the perineurial layer and into the CNS cortex. Interestingly, long cell processes were observed reaching the glia ensheathing the neuropil of the central brain. GFP reconstitution experiments highlighted multiple regions of membrane contacts between subperineurial and ensheathing glia. Furthermore, we identify the G-protein-coupled receptor (GPCR) Moody as negative regulator of the growth of subperineurial cell processes. Loss of moody triggered a massive overgrowth of subperineurial cell processes into the CNS cortex and, moreover, affected the polarized localization of the xenobiotic transporter Mdr65. Finally, we found that GPCR signaling, but not septate junction formation, is responsible for controlling membrane overgrowth. Our findings support the notion that the Drosophila BBB is able to bridge the communication gap between circulation and synaptic regions of the brain by long cell processes.

BackgroundPrevious research showed that 5-hydroxytryptophan (5HTP), a metabolic precursor of serotonin, reduces allergic lung inflammation by inhibiting eosinophil migration across endothelial monolayers.ObjectiveIt is unknown if serotonin receptors are involved in mediating this 5HTP function or if serotonin receptor (HTR) single nucleotide polymorphisms (SNPs) associate with lung function in humans.MethodsSerotonin receptor subtypes were assessed by qPCR, western blot, confocal microscopy, pharmacological inhibitors and siRNA knockdown. HTR SNPs were assessed in two cohorts.ResultsPharmacological inhibition or siRNA knockdown of the serotonin receptors HTR1A or HTR1B in endothelial cells abrogated the inhibitory effects of 5HTP on eosinophil transendothelial migration. In contrast, eosinophil transendothelial migration was not inhibited by siRNA knockdown of HTR1A or HTR1B in eosinophils. Surprisingly, these HTRs were intracellular in endothelial cells and an extracellular supplementation with serotonin did not inhibit eosinophil transendothelial migration. This is consistent with the inability of serotonin to cross membranes, the lack of selective serotonin reuptake receptors on endothelial cells, and the studies showing minimal impact of selective serotonin reuptake inhibitors on asthma. To extend our HTR studies to humans with asthma, we examined the CHIRAH and GALA cohorts for HTR SNPs that affect HTR function or are associated with behavior disorders. A polygenic index of SNPs in HTRs was associated with lower lung function in asthmatics.ConclusionsSerotonin receptors mediate 5HTP inhibition of transendothelial migration and HTR SNPs associate with lower lung function. These results may serve to aid in design of novel interventions for allergic inflammation.

Abstract Floods in ideal landscapes follow a coherent pattern where single water‐covered areas expand and afterward recede following the inverse sequence, but deviate in real landscapes due to natural or human factors resulting in water coverage shifts. Using remote sensing, we introduced two indices to describe the discrepancies between spatially integrated versus pixel‐level frequency distributions under maximum inundated conditions (dext) and throughout all flooding conditions (dtot), expressed as the relative weight of shifts on each landscape's maximum registered coverage, theoretically ranging between no displacement (

Abstract Variability in response to short-acting β2-agonists (e.g., albuterol) among patients with asthma from diverse racial/ethnic groups may contribute to asthma disparities. We sought to identify genetic variants associated with bronchodilator response (BDR) to identify potential mechanisms of drug response and risk factors for worse asthma outcomes. Genome-wide association studies of bronchodilator response (BDR) were performed using TOPMed Whole Genome Sequencing data of the Asthma Translational Genomic Collaboration (ATGC), which corresponded to 1136 Puerto Rican, 656 Mexican and 4337 African American patients with asthma. With the population-specific GWAS results, a trans-ethnic meta-analysis was performed to identify BDR-associated variants shared across the three populations. Replication analysis was carried out in three pediatric asthma cohorts, including CAMP (Childhood Asthma Management Program; n = 560), GACRS (Genetics of Asthma in Costa Rica Study; n = 967) and HPR (Hartford-Puerto Rico; n = 417). A genome-wide significant locus (rs35661809; P = 3.61 × 10–8) in LINC02220, a non-coding RNA gene, was identified in Puerto Ricans. While this region was devoid of protein-coding genes, capture Hi-C data showed a distal interaction with the promoter of the DNAH5 gene in lung tissue. In replication analysis, the GACRS cohort yielded a nominal association (1-tailed P

Understanding regulation of genes associated to disease can reveal insights into disease mechanisms. Here, the authors perform an airway epithelial transcriptome-wide association analysis to elucidate genetic determinants of airway dysfunction in asthma, identifying genetic mechanisms of mucus pathobiology.

The accurate regulation of the microenvironment within the nervous system is one of the key features characterizing complex organisms. To this end, neural tissue has to be physically separated from circulation, but at the same time, mechanisms must be in place to allow controlled transport of nutrients and macromolecules into and out of the brain. These roles are executed by cells of the blood-brain barrier (BBB) found at the interface of circulation and neural tissue. BBB dysfunction is observed in several neurological diseases in human. Although this can be considered as a consequence of diseases, strong evidence supports the notion that BBB dysfunction can promote the progression of brain disorders. In this review, we compile the recent evidence describing the contribution of the Drosophila BBB to the further understanding of brain disease features in human patients. We discuss the function of the Drosophila BBB during infection and inflammation, drug clearance and addictions, sleep, chronic neurodegenerative disorders and epilepsy. In summary, this evidence suggests that the fruit fly, Drosophila melanogaster, can be successfully employed as a model to disentangle mechanisms underlying human diseases.

Las ciudades dependen de distintos ecosistemas que les proveen servicios. Para el caso de la provisión de agua potable y la disposición de aguas servidas en las ciudades argentinas, el reconocimiento de esto aún es incompleto y fragmentado. Aquí presentamos la primera base de datos que mapea y clasifica las fuentes de suministro de agua y destinos de los efluentes de todas las ciudades argentinas con más 20000 habitantes (en 2010). A partir de reportes existentes, noticias periodísticas e información satelital se registraron en 243 ciudades los puntos de toma y vertido de aguas, junto a otra infraestructura asociada. Se encontró que 30.5, 17.5 y 12.6% de la población se abastece sólo de grandes ríos transfronterizos, agua subterránea y ríos y arroyos internos, respectivamente, con 25.2% abastecido por fuentes mixtas. Las ciudades que están conectadas a las redes públicas de saneamiento recurren para su disposición sobre todo a ríos y arroyos internos (26.6%); sin embargo, de la población urbana que no está conectada a la red cloacal, una proporción elevada dispone sus vertidos en acuíferos libres. La mayoría de las ciudades argentinas no devuelven las aguas de saneamiento al mismo sistema que las provee, y predominan los trasvases desde fuentes subterráneas hacia ríos y arroyos internos. La base de datos evidencia la contrastante ‘presión efluente’ (relación población/caudal del sistema receptor) entre ciudades vinculadas a grandes ríos (e.g., la cuenca del Paraná, con 273 habitantes.m-3.s-1) y a cuencas internas (e.g., la cuenca de Mar Chiquita, con 16141 habitantes.m-3.s-1). Esta base de datos, abierta para la consulta y actualización, visibiliza la conexión espacial e hidrológica entre las ciudades y la red hidrográfica, y contribuye a mejorar la seguridad hídrica y a priorizar los esfuerzos de protección de los ecosistemas acuáticos que la garantizan desde todos los niveles de gestión.

En las últimas décadas, la transformación de los sistemas ecológicos dio lugar a la formación de ‘neo-ecosistemas’. En las llanuras del Chaco Seco-Espinal argentino, la expansión agrícola en reemplazo de bosques, arbustales y pastizales naturales ha generado excedentes hídricos, lo que favoreció la formación de neo-humedales caracterizados por un aumento de los niveles freáticos, anegamiento y salinización. En este trabajo nos proponemos describir los neo-humedales del Chaco Seco-Espinal argentino y los factores que favorecen su formación, tomando como caso de estudio la cuenca de El Morro en la provincia de San Luis. A través de una búsqueda bibliográfica describimos las características de los sistemas que propician la formación de neo-humedales en el Chaco Seco-Espinal. Por otra parte, realizamos un análisis temporal de imágenes de alta resolución a partir del cual caracterizamos los neo-humedales de un sitio específico, la cuenca de El Morro, en la provincia de San Luis. Encontramos que en los últimos 13 años los neo-humedales triplicaron su extensión, cubriendo el 15% de la parte baja de la cuenca donde la salinización ha sido más extendida. Los neo-humedales de la cuenca presentaron valores de actividad de la vegetación (NDVI-LANDSAT) menor a los bosques circundantes (0.44±0.04 vs. 0.35±0.09), pero similar al de los cultivos anuales (neo-humedales 0.35±0.09 y cultivos 0.37±0.13). Comparados con estos últimos, los neo-humedales mostraron estaciones de crecimiento más largas (241±54 días vs. 194±54 días, para neo-humedales y cultivos, respectivamente), evidenciando revegetación con especies tolerantes a las nuevas condiciones ambientales. Finalmente, proponemos algunas pautas para la restauración y utilización de estos sistemas mediante diversos manejos que permitan recuperar su funcionalidad y su valor ecológico-productivo.

Ecología Austral celebrates its first 30 years of life with this special issue. This issue gathers a small sample of what Argentine ecology can offer to the region and the world: quality science achieved with scarce means, but with a creative use of opportunities to advance knowledge. Our perspective and context allow us to cover a wide variety of topics with great implications for ecosystem management. As editors, we would like to greatly thank those who collaborated with articles, peer review, edition of each article, and administrative and editorial management. We also thank the members of the Argentine Ecological Society for their contribution in the form of a fee that does not give them any privilege other than the satisfaction of contributing to the cause.

Latinos are heavily affected with childhood asthma. Little is known about epigenetic mechanisms of asthma in Latino youth. We conducted a meta-analysis of two epigenome-wide association studies (EWAS) of asthma, using DNA from white blood cells (WBCs) from 1,136 Latino children and youth aged 6 to 20 years. Genes near the top CpG sites in this EWAS were examined in a pathway enrichment analysis, and we then assessed whether our results replicated those from publicly available data from three independent EWAS conducted in non-Latino populations. We found that DNA methylation profiles differed between subjects with and without asthma. After adjustment for covariates and multiple testing, two CpGs were differentially methylated at a false discovery rate (FDR)-adjusted P

A cross-sectional study was carried out to determine the teachers’ attitudes and knowledge about the COVID-19 pandemic in the Canary Islands region in Spain, between May 14 - 18, 2020. A virtual questionnaire based on a validated instrument was applied. We included 1,503 surveys, which showed that teachers are unwilling to work if there is risk of infection at the school (76.6%). However, they state that they would go to work if they had the appropriate hygiene (69.2%) and protection (67.0%) measures. In conclusion, it is important to guarantee the necessary preventive measures to avoid contagion in educational centers, promoting specific training of teachers in primary prevention.

In the wild, animals face different challenges including multiple events of food scarcity. How they overcome these conditions is essential for survival. Thus, adaptation mechanisms evolved to allow the development and survival of an organism during nutrient restriction periods. Given the high energy demand of the nervous system, the molecular mechanisms of adaptation to malnutrition are of great relevance to fuel the brain. The blood-brain barrier (BBB) is the interface between the central nervous system (CNS) and the circulatory system. The BBB mediates the transport of macromolecules in and out of the CNS, and therefore, it can buffer changes in nutrient availability. In this review, we collect the current evidence using the fruit fly, Drosophila melanogaster , as a model of the role of the BBB in the adaptation to starvation. We discuss the role of the Drosophila BBB during nutrient deprivation as a potential sensor for circulating nutrients, and transient nutrient storage as a regulator of the CNS neurogenic niche.

ACE2 and TMPRSS2 have received recent attention as entry factors for SARS-CoV-2. Here the authors analyze nasal airway transcriptome data from 695 children determining ACE2 and TMPRSS2 expression is induced by viral and type2 inflammation, respectively, and both exhibit eQTLs that vary across world populations.

Abstract Background Current South American populations trace their origins mainly to three continental ancestries, i.e. European, Amerindian and African. Individual variation in relative proportions of each of these ancestries may be confounded with socio-economic factors due to population stratification. Therefore, ancestry is a potential confounder variable that should be considered in epidemiologic studies and in public health plans. However, there are few studies that have assessed the ancestry of the current admixed Chilean population. This is partly due to the high cost of genome-scale technologies commonly used to estimate ancestry. In this study we have designed a small panel of SNPs to accurately assess ancestry in the largest sampling to date of the Chilean mestizo population (n = 3349) from eight cities. Our panel is also able to distinguish between the two main Amerindian components of Chileans: Aymara from the north and Mapuche from the south. Results A panel of 150 ancestry-informative markers (AIMs) of SNP type was selected to maximize ancestry informativeness and genome coverage. Of these, 147 were successfully genotyped by KASPar assays in 2843 samples, with an average missing rate of 0.012, and a 0.95 concordance with microarray data. The ancestries estimated with the panel of AIMs had relative high correlations (0.88 for European, 0.91 for Amerindian, 0.70 for Aymara, and 0.68 for Mapuche components) with those obtained with AXIOM LAT1 array. The country’s average ancestry was 0.53 ± 0.14 European, 0.04 ± 0.04 African, and 0.42 ± 0.14 Amerindian, disaggregated into 0.18 ± 0.15 Aymara and 0.25 ± 0.13 Mapuche. However, Mapuche ancestry was highest in the south (40.03%) and Aymara in the north (35.61%) as expected from the historical location of these ethnic groups. We make our results available through an online app and demonstrate how it can be used to adjust for ancestry when testing association between incidence of a disease and nongenetic risk factors. Conclusions We have conducted the most extensive sampling, across many different cities, of current Chilean population. Ancestry varied significantly by latitude and human development. The panel of AIMs is available to the community for estimating ancestry at low cost in Chileans and other populations with similar ancestry.

Background: Chagas disease (CD) is a tropical parasitic disease spread by triatomine bugs, which are bugs that tend to infest precarious housing in rural and impoverished areas. Reducing exposure to the bugs, and thus the parasite they can carry, is essential to preventing CD in these areas. One promising long-term sustainable solution is to reconstruct precarious houses. Implementing home reconstruction requires an understanding of how householders construct barriers and facilitators they might encounter when considering whether to rebuild their homes. Methods: To understand barriers and facilitators to home reconstruction, we performed in-depth qualitative interviews with 33 residents of Canton Calvas, Loja, Ecuador, a high-risk endemic region. Thematic analysis was used to identify these barriers and facilitators. Results: The thematic analysis identified three facilitators (project facilitators, social facilitators, and economic facilitators) and two major barriers (low personal economy and extensive deterioration of existing homes). Conclusions: The study findings provide important loci for assisting community members and for agents of change in home reconstruction projects to prevent CD. Specifically, the project and social facilitators suggest that collective community efforts (minga) are more likely to support home reconstruction intentions than individualist efforts, while the barriers suggest that addressing structural issues of economy and affordability are necessary.

Las regiones áridas tienen déficit hídrico a lo largo de todo el año, lo cual limita el crecimiento de la vegetación y la provisión de agua para bebida animal. El Chaco Árido (~10 Mha) sostiene una producción ganadera extensiva de baja inversión, basada en cosechar agua de lluvia en represas (tajamares) como principal fuente de abastecimiento de agua. En este trabajo se determinó la distribución espacial de las represas y su relación con el entorno biofísico (precipitación, vegetación, caminos) en el Chaco Árido. Para ello analizamos imágenes satelitales, información vectorial y análisis multivariados sobre una grilla de 135 celdas de 0.25°x0.25° cada una. En total identificamos 7920 represas (1 cada 1230 ha) y observamos densidades máximas de 1 represa cada 185 ha, pero también celdas sin represas, asociadas a la presencia de sierras, salinas y dunas. La densidad de represas fue mayor en celdas con mayor densidad de establecimientos ganaderos, caminos y carga animal (r=0.63, r=0.56 y r=0.51, respectivamente; P

Summary: Genetic studies on telomere length are important for understanding age-related diseases. Prior GWASs for leukocyte TL have been limited to European and Asian populations. Here, we report the first sequencing-based association study for TL across ancestrally diverse individuals (European, African, Asian, and Hispanic/Latino) from the NHLBI Trans-Omics for Precision Medicine (TOPMed) program. We used whole-genome sequencing (WGS) of whole blood for variant genotype calling and the bioinformatic estimation of telomere length in n = 109,122 individuals. We identified 59 sentinel variants (p < 5 × 10−9) in 36 loci associated with telomere length, including 20 newly associated loci (13 were replicated in external datasets). There was little evidence of effect size heterogeneity across populations. Fine-mapping at OBFC1 indicated that the independent signals colocalized with cell-type-specific eQTLs for OBFC1 (STN1). Using a multi-variant gene-based approach, we identified two genes newly implicated in telomere length, DCLRE1B (SNM1B) and PARN. In PheWAS, we demonstrated that our TL polygenic trait scores (PTSs) were associated with an increased risk of cancer-related phenotypes.

Central nervous system (CNS)-related diseases are difficult to treat as most therapeutic agents they cannot reach the brain tissue, mainly due to the blood-brain barrier (BBB), arguably the tightest barrier between the human body and cerebral parenchyma, which routinely excludes most xenobiotic therapeutics compounds. The BBB is a multicellular complex that structurally forms the neurovascular unit (NVU) and is organized by neuro-endothelial and glial cells. BBB breakdown and dysfunction from the cerebrovascular cells lead to leakages of systemic components from the blood into the CNS, contributing to neurological deficits. Understanding the molecular mechanisms that regulate BBB permeability and disruption is essential for establishing future therapeutic strategies to restore permeability and improve cerebrovascular health. MicroRNAs (miRNAs), a type of small non-coding RNAs, are emerging as an important regulator of BBB integrity by modulating gene expression by targeting mRNA transcripts. miRNAs is implicated in the development and progression of various illnesses. Conversely, nanoparticle carriers offer unprecedented opportunities for cell-specific controlled delivery of miRNAs for therapeutic purposes. In this sense, we present in this graphical review critical evidence in the regulation of cell junction expression mediated by miRNAs induced by hypoxia and for the use of nanoparticles for the delivery of miRNA-based therapeutics in the treatment of BBB permeability.

The Major Histocompatibility Complex (MHC) makes the largest genetic contribution to multiple sclerosis (MS) susceptibility, with 32 independent effects across the region explaining 20% of the heritability in European populations. Variation is high across populations with allele frequency differences and population-specific risk alleles identified. We sought to identify MHC-specific MS susceptibility variants and assess the effect of ancestral risk modification within 2652 Latinx and Hispanic individuals as well as 2435 Black and African American individuals. We have identified several novel susceptibility alleles which are rare in European populations including HLA-B*53:01, and we have utilized the differing linkage disequilibrium patterns inherent to these populations to identify an independent role for HLA-DRB1*15:01 and HLA-DQB1*06:02 on MS risk. We found a decrease in Native American ancestry in MS cases vs controls across the MHC, peaking near the previously identified MICB locus with a decrease of ~5.5% in Hispanics and ~0.4% in African Americans. We have identified several susceptibility variants, including within the MICB gene region, which show global ancestry risk modification and indicate ancestral differences which may be due in part to correlated environmental factors. We have also identified several susceptibility variants for which MS risk is modified by local ancestry and indicate true ancestral genetic differences; including HLA-DQB1*06:02 for which MS risk for European allele carriers is almost two times the risk for African allele carriers. These results validate the importance of investigating MS susceptibility at an ancestral level and offer insight into the epidemiology of MS phenotypic diversity.

Abstract Background Global gene expression levels are known to be highly dependent upon gross demographic features including age, yet identification of age-related genomic indicators has yet to be comprehensively undertaken in a disease and treatment-specific context. Methods We used gene expression data from CD4+ lymphocytes in the Asthma BioRepository for Integrative Genomic Exploration (Asthma BRIDGE), an open-access collection of subjects participating in genetic studies of asthma with available gene expression data. Replication population participants were Puerto Rico islanders recruited as part of the ongoing Genes environments & Admixture in Latino Americans (GALA II), who provided nasal brushings for transcript sequencing. The main outcome measure was chronic asthma control as derived by questionnaires. Genomic associations were performed using regression of chronic asthma control score on gene expression with age in years as a covariate, including a multiplicative interaction term for gene expression times age. Results The SMARCD1 gene (SWI/SNF-related matrix-associated actin-dependent regulator of chromatin subfamily D member 1) interacted with age to influence chronic asthma control on inhaled corticosteroids, with a doubling of expression leading to an increase of 1.3 units of chronic asthma control per year (95% CI [0.86, 1.74], p = 6 × 10− 9), suggesting worsening asthma control with increasing age. This result replicated in GALA II (p = 3.8 × 10− 8). Cellular assays confirmed the role of SMARCD1 in glucocorticoid response in airway epithelial cells. Conclusion Focusing on age-dependent factors may help identify novel indicators of asthma medication response. Age appears to modulate the effect of SMARCD1 on asthma control with inhaled corticosteroids.

Abstract Background Association studies in recently admixed populations are extremely useful to identify the genetic architecture of pigmentation, due to their high genotypic and phenotypic variation. However, to date only four Genome-Wide Association Studies (GWAS) have been carried out in these populations. Results We present a GWAS of skin pigmentation in an admixed sample from Cuba (N = 762). Additionally, we conducted a meta-analysis including the Cuban sample, and admixed samples from Cape Verde, Puerto Rico and African-Americans from San Francisco. This meta-analysis is one of the largest efforts so far to characterize the genetic basis of skin pigmentation in admixed populations (N = 2,104). We identified five genome-wide significant regions in the meta-analysis, and explored if the markers observed in these regions are associated with the expression of relevant pigmentary genes in human melanocyte cultures. In three of the regions identified in the meta-analysis (SLC24A5, SLC45A2, and GRM5/TYR), the association seems to be driven by non-synonymous variants (rs1426654, rs16891982, and rs1042602, respectively). The rs16891982 polymorphism is strongly associated with the expression of the SLC45A2 gene. In the GRM5/TYR region, in addition to the rs1042602 non-synonymous SNP located on the TYR gene, variants located in the nearby GRM5 gene have an independent effect on pigmentation, possibly through regulation of gene expression of the TYR gene. We also replicated an association recently described near the MFSD12 gene on chromosome 19 (lead variant rs112332856). Additionally, our analyses support the presence of multiple signals in the OCA2/HERC2/APBA2 region on chromosome 15. A clear causal candidate is the HERC2 intronic variant rs12913832, which has a profound influence on OCA2 expression. This variant has pleiotropic effects on eye, hair, and skin pigmentation. However, conditional and haplotype-based analyses indicate the presence of other variants with independent effects on melanin levels in OCA2 and APBA2. Finally, a follow-up of genome-wide signals identified in a recent GWAS for tanning response indicates that there is a substantial overlap in the genetic factors influencing skin pigmentation and tanning response. Conclusions Our meta-analysis of skin pigmentation GWAS in recently admixed populations provides new insights about the genetic architecture of this complex trait.

Neurogenesis is achieved through a sequence of steps that include specification and differentiation of progenitors into mature neurons. Frequently, precursors migrate to distinct positions before terminal differentiation. The Slit-Robo pathway, formed by the secreted ligand Slit and its membrane bound receptor Robo, was first discovered as a regulator of axonal growth. However, today, it is accepted that this pathway can regulate different cellular processes even outside the nervous system. Since most of the studies performed in the nervous system have been focused on axonal and dendritic growth, it is less clear how versatile is this signaling pathway in the developing nervous system. Here we describe the participation of the Slit-Robo pathway in the development of motion sensitive neurons of the Drosophila visual system. We show that Slit and Robo receptors are expressed in different stages during the neurogenesis of motion sensitive neurons. Furthermore, we find that Slit and Robo regulate multiple aspects of their development including neuronal precursor migration, cell segregation between neural stem cells and daughter cells and formation of their connectivity pattern. Specifically, loss of function of slit or robo receptors in differentiated motion sensitive neurons impairs dendritic targeting, while knocking down robo receptors in migratory progenitors or neural stem cells leads to structural defects in the adult optic lobe neuropil, caused by migration and cell segregation defects during larval development. Thus, our work reveals the co-option of the Slit-Robo signaling pathway in distinct developmental stages of a neural lineage.

Los ecosistemas acuáticos continentales (EAC) constituyen elementos de gran valor natural, social y cultural. Además, son sumideros naturales de distintos procesos que involucran la interfase agua-tierraatmósfera y, por lo tanto, los primeros a nivel territorial en mostrar síntomas de deterioro ambiental. En este artículo analizamos el enfoque de los servicios ecosistémicos (SE) y su aplicación a los EAC. Nuestro objetivo primario es proveer una introducción y revisión crítica del enfoque, y sus prácticas para científicos, técnicos y funcionarios interesados en los problemas del agua. Presentamos el enfoque en general y realizamos un desglose de los principales elementos constitutivos del análisis, en particular de aquellos que consideramos más relevantes para impulsar una mirada ambiental e integral de los EAC. También revisamos los aspectos más contenciosos del enfoque de los SE y discutimos en qué medida representan matices prácticos más que brechas conceptuales. Luego, caracterizamos distintos escenarios que brindan oportunidades para su aplicación desde la óptica de la administración ambiental, incluyendo una revisión de soluciones basadas en la naturaleza en comparación con sus contrapartes basadas en infraestructura gris. Más allá de todas las características positivas que pudieran atribuirse al enfoque, reconocemos incorporarlo de manera efectiva en los ámbitos de decisión tradicionales de los recursos hídricos de nuestro país no será automática. En este sentido, proponemos que es necesario alinear el enfoque de los SE con el del manejo integrado de los recursos hídricos, que es la base de los ‘Principios rectores de la política hídrica de la República Argentina’ adoptados por la Nación y las provincias. Foto: Microsoft Argentina

El agua media o protagoniza muchas de las contribuciones de la naturaleza a los seres humanos. Este artículo explora y ejemplifica la representación espacial de la oferta y la demanda de servicios ecosistémicos relacionados con el agua y su aplicación a distintas necesidades de la gestión y la política ambiental, con particular foco en la Argentina. La oferta de estos servicios se puede mapear combinando distintas fuentes de información geográfica y satelital apoyada en protocolos o modelos preestablecidos. Su demanda, aun para servicios de gran subjetividad como los culturales, puede mapearse aprovechando bases de datos públicas de fotografías o redes sociales. Para representar el vínculo entre oferta y demanda se requieren abstracciones o distorsiones del espacio. Una posibilidad es discretizar el territorio en sectores y generar una matriz de intercambio de múltiples servicios entre ellos. Otra es el análisis continuo de la producción y el consumo de servicios a lo largo de las cuencas. La representación del transporte de ‘agua virtual’ asociado al intercambio de productos puede relacionarse al flujo de servicios ecosistémicos hídricos sólo si se distinguen las fuentes de agua involucradas (e.g., lluvia o ‘agua verde’ vs. riego o ‘agua azul’ para productos agropecuarios) y su valoración en los contextos de origen y destino. Cada representación se adapta a diferentes situaciones de gestión. Los mapas son valiosos para el ordenamiento territorial. Las matrices de intercambio entre sectores del territorio son indicadas para explorar conflictos y oportunidades de acuerdos. La representación continua de servicios de provisión y regulación en cuencas es útil para evaluar intervenciones hidráulicas o verdes. Finalmente, los análisis del intercambio de agua virtual entre países constituyen una valiosa pieza para negociaciones internacionales. La representación de los servicios ecosistémicos relacionados con el agua es un pilar de la gobernanza de la naturaleza idealmente construido por científicos y decisores en conjunto.

Abstract International agreements aim to conserve 17% of Earth's land area by 2020 but include no area‐based conservation targets within the working landscapes that support human needs through farming, ranching, and forestry. Through a review of country‐level legislation, we found that just 38% of countries have minimum area requirements for conserving native habitats within working landscapes. We argue for increasing native habitats to at least 20% of working landscape area where it is below this minimum. Such target has benefits for food security, nature's contributions to people, and the connectivity and effectiveness of protected area networks in biomes in which protected areas are underrepresented. We also argue for maintaining native habitat at higher levels where it currently exceeds the 20% minimum, and performed a literature review that shows that even more than 50% native habitat restoration is needed in particular landscapes. The post‐2020 Global Biodiversity Framework is an opportune moment to include a minimum habitat restoration target for working landscapes that contributes to, but does not compete with, initiatives for expanding protected areas, the UN Decade on Ecosystem Restoration (2021–2030) and the UN Sustainable Development Goals.

Humans place strong pressure on land and have modified around 75% of Earth’s terrestrial surface. In this context, ecoregions and biomes, merely defined on the basis of their biophysical features, are incomplete characterizations of the territory. Land system science requires classification schemes that incorporate both social and biophysical dimensions. In this study, we generated spatially explicit social-ecological land system (SELS) typologies for South America with a hybrid methodology that combined data-driven spatial analysis with a knowledge-based evaluation by an interdisciplinary group of regional specialists. Our approach embraced a holistic consideration of the social-ecological land systems, gathering a dataset of 26 variables spanning across 7 dimensions: physical, biological, land cover, economic, demographic, political, and cultural. We identified 13 SELS nested in 5 larger social-ecological regions (SER). Each SELS was discussed and described by specific groups of specialists. Although 4 environmental and 1 socioeconomic variable explained most of the distribution of the coarse SER classification, a diversity of 15 other variables were shown to be essential for defining several SELS, highlighting specific features that differentiate them. The SELS spatial classification presented is a systematic and operative characterization of South American social-ecological land systems. We propose its use can contribute as a reference framework for a wide range of applications such as analyzing observations within larger contexts, designing system-specific solutions for sustainable development, and structuring hypothesis testing and comparisons across space. Similar efforts could be done elsewhere in the world.

Leukotrienes play a central pathophysiological role in both paediatric and adult asthma. However, 35% to 78% of asthmatics do not respond to leukotriene inhibitors. In this study we tested the role of the LTA4H regulatory variant rs2660845 and age of asthma onset in response to montelukast in ethnically diverse populations. We identified and genotyped 3,594 asthma patients treated with montelukast (2,514 late-onset and 1,080 early-onset) from seven cohorts (UKBiobank, GoSHARE, BREATHE, Tayside RCT, PAGES, GALA II and SAGE). Individuals under montelukast treatment experiencing at least one exacerbation in a 12-month period were compared against individuals with no exacerbation, using logistic regression for each cohort and meta-analysis. While no significant association was found with European late-onset subjects, a meta-analysis of 523 early-onset individuals from European ancestry demonstrated the odds of experiencing asthma exacerbations by carriers of at least one G allele, despite montelukast treatment, were increased (odds-ratio = 2.92, 95%confidence interval (CI): 1.04-8.18, I2 = 62%, p = 0.0412) compared to those in the AA group. When meta-analysing with other ethnic groups, no significant increased risk of asthma exacerbations was found (OR = 1.60, 95% CI: 0.61-4.19, I2 = 85%, p = 0.342). Our study demonstrates that genetic variation in LTA4H, together with timing of asthma onset, may contribute to variability in montelukast response. European individuals with early-onset (≤18y) carrying at least one copy of rs2660845 have increased odd of exacerbation under montelukast treatment, presumably due to the up-regulation of LTA4H activity. These findings support a precision medicine approach for the treatment of asthma with montelukast.

Agroecology promises a third way between common global agriculture tradeoffs such as food production and nature conservation, environmental sustainability and ecosystem services. However, most successful examples of mainstreaming agroecology come from smallholder, family agriculture, that represents only about 30% of the world agricultural area. Mainstreaming agroecology among large scale farmers is urgently needed, but it requires addressing specific questions in research, technology and policy development to support sustainable transitions. Here we take stock of the existing knowledge on some key aspects necessary to support agroecological transitions in large scale farming, considering two contrasting starting points: highly subsidized and heavily taxed agricultural contexts, represented here by the examples of Western Europe and temperate South America. We summarize existing knowledge and gaps around service crops, arthropod-mediated functions, landscape and watershed regulation, graze-based livestock, nature-inclusive landscapes, and policy mechanisms to support transitions. We propose a research agenda for agroecology in large scale farming organized in five domains: (i) Breeding for diversity, (ii) Scalable complexity, (iii) Managing cycles beyond fields and farms, (iv) Sharing the cultivated landscape, and (v) Co-innovation with farmers, value chains and policy makers. Agroecology may result in a renewed impetus in large scale farming, to attract the youth, foster clean technological innovation, and to promote a new generation of large-scale farmers that take pride in contributing to feeding the world while serving the planet and its people.

While the function of proteins and genes has been widely studied during vertebrate development, relatively little work has addressed the role of carbohydrates. Hyaluronan (HA), also known as hyaluronic acid, is an abundant carbohydrate in embryonic tissues and is the main structural component of the extracellular matrix of epithelial and mesenchymal cells. HA is able to absorb large quantities of water and can signal by binding to cell-surface receptors. During organ development and regeneration, HA has been shown to regulate cell proliferation, cell shape, and migration. Here, we have investigated the function of HA during molar tooth development in mice, in which, similar to humans, new molars sequentially bud off from a pre-existing molar. Using an ex vivo approach, we found that inhibiting HA synthesis in culture leads to a significant increase in proliferation and subsequent size of the developing molar, while the formation of sequential molars was inhibited. By cell shape analysis, we observed that inhibition of HA synthesis caused an elongation and reorientation of the major cell axes, indicating that disruption to cellular orientation and shape may underlie the observed phenotype. Lineage tracing demonstrated the retention of cells in the developing first molar (M1) at the expense of the generation of a second molar (M2). Our results highlight a novel role for HA in controlling proliferation, cell orientation, and migration in the developing tooth, impacting cellular decisions regarding tooth size and number.

The genetic control of gene expression is a core component of human physiology. For the past several years, transcriptome-wide association studies have leveraged large datasets of linked genotype and RNA sequencing information to create a powerful gene-based test of association that has been used in dozens of studies. While numerous discoveries have been made, the populations in the training data are overwhelmingly of European descent, and little is known about the generalizability of these models to other populations. Here, we test for cross-population generalizability of gene expression prediction models using a dataset of African American individuals with RNA-Seq data in whole blood. We find that the default models trained in large datasets such as GTEx and DGN fare poorly in African Americans, with a notable reduction in prediction accuracy when compared to European Americans. We replicate these limitations in cross-population generalizability using the five populations in the GEUVADIS dataset. Via realistic simulations of both populations and gene expression, we show that accurate cross-population generalizability of transcriptome prediction only arises when eQTL architecture is substantially shared across populations. In contrast, models with non-identical eQTLs showed patterns similar to real-world data. Therefore, generating RNA-Seq data in diverse populations is a critical step towards multi-ethnic utility of gene expression prediction.

The burden of asthma varies between ancestries, but GWAS have so far focused on mainly European ancestry populations. Here, Daya et al. perform GWAS for asthma in 14,654 individuals of African ancestry and, besides confirming previously known loci, identify two potentially African ancestry-specific loci.

Chagas disease is a neglected tropical disease that disproportionately affects impoverished rural communities. Insecticide-based approaches are inconsistently performed and exorbitantly priced for the communities affected. The present study considers an alternative approach to primary prevention of Chagas disease using entertainment education. As part of an ongoing effort in rural Ecuador, we worked with the children of the community of Guara, national insect control workers, and academicians to co-develop a song to promote behaviors related to preventing Chagas. Through an analysis of the song, we demonstrate opportunities for meaningful intervention in rural communities, as well as challenges to implementing an entertainment education approach when working with national stakeholders.

Abstract Background Neural stem cells generate all of the neurons and glial cells in the central nervous system, both during development and in the adult to maintain homeostasis. In the Drosophila optic lobe, neuroepithelial cells progress through two transient progenitor states, PI and PII, before transforming into neuroblasts. Here we analyse the role of Notch signalling in the transition from neuroepithelial cells to neuroblasts. Results We observed dynamic regulation of Notch signalling: strong activity in PI progenitors, low signalling in PII progenitors, and increased activity after neuroblast transformation. Ectopic expression of the Notch ligand Delta induced the formation of ectopic PI progenitors. Interestingly, we show that the E3 ubiquitin ligase, Neuralized, regulates Delta levels and Notch signalling activity at the transition zone. We demonstrate that the proneural transcription factor, Lethal of scute, is essential to induce expression of Neuralized and promote the transition from the PI progenitor to the PII progenitor state. Conclusions Our results show dynamic regulation of Notch signalling activity in the transition from neuroepithelial cells to neuroblasts. We propose a model in which Lethal of scute activates Notch signalling in a non-cell autonomous manner by regulating the expression of Neuralized, thereby promoting the progression between different neural stem cell states.

Abstract Precise control of neurite guidance during development is essential to ensure proper formation of neuronal networks and correct function of the central nervous system (CNS). How neuronal projections find their targets to generate appropriate synapses is not entirely understood. Although transcription factors are key molecules during neurogenesis, we do not know their entire function during the formation of networks in the CNS. Here, we used the Drosophila melanogaster optic lobe as a model for understanding neurite guidance during development. We assessed the function of Sox102F/SoxD, the unique Drosophila orthologue of the vertebrate SoxD family of transcription factors. SoxD is expressed in immature and mature neurons in the larval and adult lobula plate ganglia (one of the optic lobe neuropils), but is absent from glial cells, neural stem cells and progenitors of the lobula plate. SoxD RNAi knockdown in all neurons results in a reduction of the lobula plate neuropil, without affecting neuronal fate. This morphological defect is associated with an impaired optomotor response of adult flies. Moreover, knocking down SoxD only in T4/T5 neuronal types, which control motion vision, affects proper neurite guidance into the medulla and lobula. Our findings suggest that SoxD regulates neurite guidance, without affecting neuronal fate.

Pulmonary function is influenced by environmental factors, lifestyle, and genetics. Here, in a multiethnic GWAS meta-analysis for pulmonary function traits, the authors identify over 50 additional genetic loci, a subset of which are specific for European, African, Asian, or Hispanic/Latino ancestry.

Pulmonary arterial hypertension of newborns (PAHN) constitutes a critical condition involving both severe cardiac remodeling and right ventricle dysfunction. One main cause of this condition is perinatal hypoxia and oxidative stress. Thus, it is a public health concern for populations living above 2500 m and in cases of intrauterine chronic hypoxia in lowlands. Still, pulmonary and cardiac impairments in PAHN lack effective treatments. Previously we have shown the beneficial effects of neonatal melatonin treatment on pulmonary circulation. However, the cardiac effects of this treatment are unknown. In this study, we assessed whether melatonin improves cardiac function and modulates right ventricle (RV) oxidative stress. Ten lambs were gestated, born, and raised at 3600 m. Lambs were divided in two groups. One received daily vehicle as control, and another received daily melatonin (1 mg·kg−1·d−1) for 21 days. Daily cardiovascular measurements were recorded and, at 29 days old, cardiac tissue was collected. Melatonin decreased pulmonary arterial pressure at the end of the experimental period. In addition, melatonin enhanced manganese superoxide dismutase and catalase (CAT) expression, while increasing CAT activity in RV. This was associated with a decrease in superoxide anion generation at the mitochondria and NADPH oxidases in RV. Finally, these effects were associated with a marked decrease of oxidative stress markers in RV. These findings support the cardioprotective effects of an oral administration of melatonin in newborns that suffer from developmental chronic hypoxia.

BackgroundMitochondria support critical cellular functions, such as energy production through oxidative phosphorylation, regulation of reactive oxygen species, apoptosis, and calcium homeostasis.ObjectiveGiven the heightened level of cellular activity in patients with asthma, we sought to determine whether mitochondrial DNA (mtDNA) copy number measured in peripheral blood differed between individuals with and without asthma.MethodsWhole genome sequence data was generated as part of the Trans-Omics for Precision Medicine (TOPMed) Program on participants from the Study of Asthma Phenotypes and Pharmacogenomic Interactions by Race-ethnicity (SAPPHIRE) and the Study of African Americans, Asthma, Genes, & Environment II (SAGE II). We restricted our analysis to individuals who self-identified as African American (3,651 asthma cases and 1,344 controls). Mitochondrial copy number was estimated using the sequencing read depth ratio for the mitochondrial and nuclear genomes. Respiratory complex expression was assessed using RNA-sequencing.ResultsAverage mitochondrial copy number was significantly higher among individuals with asthma when compared with controls (SAPPHIRE: 218.60 vs. 200.47, PConclusionsWe observed a robust association between asthma and higher mitochondrial copy number. Asthma having an effect on mitochondria function was also supported by lower respiratory complex gene expression in this group.

RationaleSevere early-life respiratory illnesses, particularly those caused by respiratory syncytial virus (RSV) and human rhinovirus (HRV), are strongly associated with the development of asthma in children. Puerto Rican children in particular have a strikingly high asthma burden. However, prior studies of the potential associations between early-life respiratory illnesses and asthma in Puerto Rican and other minority populations have been limited.ObjectivesWe sought to determine whether early-life respiratory illness was associated with asthma in Puerto Rican, Mexican American, and African American children.MethodsUsing a logistic regression analysis, we examined the association between early-life respiratory illnesses (report of upper respiratory infection (URI), pneumonia, bronchitis, and bronchiolitis/RSV) within the first two years of life and physician-diagnosed asthma after the age of two in a large cohort of Puerto Rican, Mexican American, and African American children.Measurements and main resultsWhile early-life respiratory illnesses were associated with greater asthma odds in Puerto Ricans, Mexican Americans, and African Americans, these associations were stronger among Puerto Rican children. Specifically, in Puerto Ricans, the odds was 6.15 (95% CI: 4.21-9.05) if the child reported at least one of the following respiratory illness: URI, pneumonia, bronchitis or bronchiolitis. The odds were also higher in Puerto Ricans when considering these conditions separately.ConclusionsWe observed population-specific associations between early-life respiratory illnesses and asthma, which were especially significant and stronger in Puerto Ricans. Taken together with the known high burden of RSV in Puerto Rico, our results may help explain the high burden of asthma in Puerto Ricans.

El reemplazo de pastizales por forestaciones es uno de los cambios más extremos en el uso del suelo por su impacto en el suelo y en el funcionamiento de la vegetación. En los ecosistemas de llanuras, este cambio generó, en muchos casos, alteraciones químicas en los suelos como salinización, sodificación y alcalinización/acidificación. Si bien los procesos hídricos, químicos y biológicos que tienen lugar fueron extensamente caracterizados, debido al acoplamiento entre estos procesos y su no-linealidad, la tarea de cuantificarlos es difícil y, hasta el momento, no existen estudios que los hayan evaluado. El presente trabajo intenta caracterizar, mediante la modelación del transporte reactivo, los procesos físico-químicos que tienen lugar en un pastizal forestado con Eucalyptus camaldulensis en la Pampa Deprimida (Castelli, provincia de Buenos Aires). Para ello, se utilizó información hidrológica y química (agua, suelo y plantas). El modelo numérico simula los flujos de agua y las potenciales reacciones químicas en el contexto de reproducir 1) las alteraciones hidrológicas que causa la forestación y por 2) la intrusión de agua salina profunda, 3) la absorción y la exudación de nutrientes por las raíces, y 4) la respiración y el reciclaje de solutos. Los resultados de la modelación sugieren que factores como la composición química de la napa freática, el intercambio catiónico de los materiales del suelo con la solución del suelo, la precipitación/disolución de minerales y la interacción con la rizósfera (toma/exclusión/exudación de solutos) son los mecanismos dominantes que controlarían la dirección del cambio químico en el suelo (acidificación vs. alcalinización). Este cambio muestra contrastes marcados en distancias cortas (250 m) desde el pastizal, pasando por el margen, hasta el centro del sector forestado. Finalmente, la intensidad y la dirección de los cambios, y la transformación del suelo dependerá tanto del nuevo ecosistema que los humanos imponen como de la naturaleza química e hidrológica del sitio. https://doi.org/10.25260/EA.19.29.3.0.896

Background South America faces strong environmental pressures as a result of agriculture and infrastructure expansion and also of demographic growth, demanding immediate action to preserve natural assets by establishing protected areas. Currently, 7.1% of the (sub)continent is under strict conservation categories (I to IV, IUCN), but the spatial distribution of these 1.3 × 106 km2 is poorly understood. We evaluated the representation of nature within the networks of protected areas, map conservation priorities and assess demographic, economic or geopolitical causes of existing protection patterns. Methods We characterized nature representation by looking at two components: the extent and the equality of protection. The first refers to the fraction of territory under protection, while the second refers to the homogeneity in the distribution along natural conditions of this protected fraction. We characterized natural conditions by either 113 biogeographical units (specifically, ecoregions) or a series of limited and significant climatic, topographic and edaphic traits. We analyzed representation every ten years since 1960 at national and continental levels. In the physical approach, histograms allowed us to map the degree of conservation priorities. Finally, we ranked the importance of different economic or geopolitical variables driving the observed distributions with a random forest technique. Results Nature representation varied across countries in spite of its priority in conservation agendas. In Brazil, Peru and Argentina there are still natural conditions with no formal protection, while in Bolivia and Venezuela, protected areas incorporate the natural diversity in a more balanced manner. As protected networks have increased their extent, so did their equality across and within countries over time. Our maps revealed as top continental priorities the southern temperate, subhumid and fertile lowland environments, and other country-specific areas. Protection extent was generally driven by a low population density and isolation, while other variables like distance to frontiers, were relevant only locally (e.g., in Argentina). Discussion Our description of the spatial distribution of protected areas can help societies and governments to improve the allocation of conservation efforts. We identified the main limitations that future conservation efforts will face, as protection was generally driven by the opportunities provided by low population density and isolation. From a methodological perspective, the physical approach reveals new properties of protection and provides tools to explore nature representation at different spatial, temporal and conceptual levels, complementing the traditional ones based on biodiversity or biogeographical attributes.