Chaco Ecoregion Research Articles

Geographic Variation in Cranial Morphology of the Southern Mountain Cavy, Microcavia australis (Rodentia, Caviidae): Taxonomic Implications, with the Description of a New Species.

Pablo Teta, Ricardo A. Ojeda, Sergio O. Lucero, and Guillermo D'Elía (2017) We analyzed the geographic variation in cranial morphology of the Southern Mountain Cavy, Microcavia australis, throughout of its distributional range. Our analysis allows us to recognize three geographically allopatric morphotypes. These morphotypes differ in the general size and shape of the skull and discrete morphological traits of the zygomatic arch, palate and mesopterygoid fossa. Based on these results, we restrict the name australis to populations distributed in southern Argentina and west-central Andes and the name maenas to the morphotype of northwestern and central Argentina. The third morphotype occurs in the Dry Chaco ecoregion and is described here as a new species.

Phylogenetic and divergence time analysis of the Chelonoidis chilensis complex (Testudines: Testudinidae)

We present a phylogenetic and divergence time analysis of the Chelonoidis chilensis complex (the southernmost tortoises of South America) within crown Testudinidae. We compiled a dataset of 1118 bp cytochrome b (cyt b) sequences derived from 111 individuals sampled across the known geographic range of the species, and performed a phylogenetic analysis employing Maximum Parsimony, Maximum Likelihood and Bayesian Inference methods. The resulting trees showed similar topologies and support values. The C. chilensis complex was always recovered as a monophyletic group composed by two major clades (i.e. haplogroups). The biogeographic distribution of one of these clades overlaps with the Dry Chaco eco–region, while the biogeographic distribution of the other overlaps with the Monte eco–region. In order to date the origin and diversification time of these two clades, we employed a previously published two-step molecular clock method. In the first step we dated the time of origin of C. chilensis as a clade within the Testudinidae family using new and previously published sequences, extinct testudinid taxa for age calibration and the Fossilized Birth-Death (FBD) model. In the second step we dated the divergence between the haplogroups of C. chilensis based on the time of origin estimated in the first step and a coalescent evolution model. Our results suggest that divergence between Dry Chaco and Monte tortoises may have occurred about 2.47 million of years ago. We interpret these results in the light of the environmental and geological changes that occurred during the late Pliocene to Middle Pleistocene of South America.

To chop or not to chop? Tackling shrub encroachment by roller-chopping preserves woody plant diversity and composition in a dry subtropical forest

Shrub encroachment is a frequently observed phenomenon in the arid and semi-arid biomes. In the dry forests of the Argentine Chaco ecoregion that are affected by shrub encroachment, the growing demand for grazing areas has led to the creation of a silvopastoral system. Under the Chaco silvopastoral system, a commonly used treatment to disrupt the excessive shrub layer and promote the growth of grasses is roller-chopping by a tractor-pulled iron drum. While previous studies evaluating the effects of roller-chopping on diversity have focused mostly on the herbaceous stratum as the primary source of forage, much less is known about the effects of roller-chopping on woody plants. To fill this gap, we measured woody plants of the shrub layer in a low-intensity roller-chopping experiment in northern Argentina after applying different frequencies of roller-chopping in a semi-arid Chaco forest area with a well-developed shrub layer. Data were collected in an experiment in which 3 different roller-chopping treatments were applied: a single two-pass roller-chopping in the summer of 2006/2007 (RCh1); a one-pass roller-chopping in the summer of 2006/2007, repeated in the summer of 2014/2015 (RCh2); and no treatment (Control). In each treatment, 16 circular, randomly placed plots with a radius of 9m were sampled, and all woody plants in the shrub layer with a diameter ≥10mm at the base were recorded. The diversity was analysed using profiles of alpha and beta diversity and by calculating the average distance from an individual circular plot to the treatment group centroid defined in the principal coordinate space. In total, 26 species of woody plants were recorded, of which 24 were found in Control, 22 in RCh1, and 23 in RCh2. Although the alpha diversity differed only slightly among the treatments, the beta diversity of the roller-chopped treatment areas was generally higher than that of the untreated plots. The species composition of the roller-chopped plots differed little from that of the control plots. Our study revealed little overall effect of roller-chopping on the species diversity and composition of woody plants. The transformation of the Chaco forest degraded by shrub encroachment to a silvopastoral system by roller-chopping is changing the structure of the forest but to a large extent has retained the presence and the relative abundance of woody plant species. We conclude that roller-chopping is a good management tool to reduce woody plant encroachment and create a silvopastoral system while preserving ecosystem functions.

Reptile species persistence under climate change and direct human threats in north-western Argentina

SUMMARYProtected areas have been established historically in residual places where the potential for extractive uses is low, implying that places at risk are usually under-protected. Argentina is no exception, with few protected areas established in productive regions that are prone to conversion. Here, using reptiles as a study group and considering the most important human threats in north-western Argentina, we estimated priority conservation areas where we expect species to persist in the face of climate change and land conversion. Protected areas cover no more than 9% of the study region, but represent less than 15% of reptile distributions. There are great opportunities for improving the conservation status in the region by protecting only 8% more of north-western Argentina, with the level of species protection inside the protected area network increasing almost four-fold, reaching 43% of species distributions on average and 59% of the distributions of threatened reptiles. Fortunately, the highest diversity of reptiles in the region does not match the places targeted for agriculture expansion. Our findings suggest that future prioritization schemes should embrace other groups that are especially diverse in the Chaco ecoregion, which overlaps with our study area.

Primeros registros de la herpetofauna en dos areas naturales protegidas de la provincia de Santiago del Estero (Argentina)

Dry Chaco ecoregion is one of the largest remnants of dry forest in Latin America and has a very diverse herpetofauna. However, further studies are required for deep knowledge of its composition and complexity. Our objective in this study was performing an inventory of the herpetofauna in two Natural Areas of Dry Chaco, Santiago del Estero: Cabure Sur and Parque Provincial Copo. The herpetofauna inventory was performed by visual, photographic, and auditory registers. In two protected areas were recorded 21 and 25 species of anurans and reptiles, respectively. According to last Argentinian Herpetological Categorization were found one threatened and five vulnerable species of reptiles. This first inventory revealed that herpetofauna of two protected areas of Santiago del Estero contains about 60% of Dry Chaco herpetofauna. Finally, we provide new information for future research and conservation actions on this ecoregion that currently are severely modified by the expansion of agricultural frontier.

New records of bats (Mammalia: Chiroptera) for a southern locality of the Argentine Yungas

The forests of northwestern Argentina represent one of the most diverse areas of the country, but also one of the most affected by human activities. The southern border of this region is a transition area with the Dry Chaco Ecoregion and represents a poorly studied zone. The aim of this study was to assess the diversity of bats at the village of Escaba, southern Tucuman. Seven field surveys were conducted at five different sites. A total of 120 specimens in three families and 14 species were recorded, 12 of them representing new records for the study area, increasing the species richness of Escaba from four to 16 species. The area will be recommended as an AICOM, a status given by the RELCOM, thereby promoting actions to preserve the species of bat in the area.

Identifying Current and Missing Knowledge in the Control of Pyrethroid-Resistant Triatoma infestans, Vector of Chagas Disease

Triatomines are blood-sucking bugs that occur mainly in Latin America. They are vectors of Trypanosoma cruzi, the parasite that causes Chagas disease. Chemical control of Chagas disease´s vectors by using pyrethroid insecticides has been highly successful for the elimination of domestic infestation and consequently the reduction of the vector transmission. However, at the beginning of the 2000s a decrease in the effectiveness of the chemical control of triatomines was detected in several areas from Argentina and Bolivia, particularly in the Gran Chaco eco-region.During the last 15 years, several studies demonstrated the evolution of insecticide resistance in Triatoma infestans and established the presence of different toxicological profiles, the autosomal inherence of resistance, the biological costs of deltamethrin resistance, the expression of deltamethrin resistance thorough the embryonic development, and the main mechanisms of resistance (target-site insensitivity and metabolic detoxification of insecticides).The emergence of pyrethroid resistance coupled with the usual difficulties in sustaining adequate rates of insecticide applications emphasize the need of incorporating other tools for integrated vector and disease control, such as the proposal of the organo-phosphorus insecticide fenitrothion as an alternative chemical strategy for the management of the resistance because it was effective against pyrethroid-resistant populations in laboratory and semi-field trials.New studies on the current situation of presence and spread of resistant populations of triatomines and the acceptance of the use of alternative insecticides are critical requirements in the implementation of strategies for the management of resistance and for the rational design of campaigns oriented to reducing the vector transmission of Chagas’ disease.

Trophic plasticity, environmental gradients and food‐web structure of tropical pond communities

Summary Freshwater pond communities exhibit strong patterns in species composition in response to environmental gradients such as ecosystem size, disturbance and productivity, serving as excellent systems for studies of food‐web structure. We surveyed 13 ponds that varied along environmental gradients of canopy cover, pond size and hydroperiod at the beginning and end of the rainy season in the semi‐arid thorn forests of the Gran Chaco ecoregion of Bolivia. We collected basal resources and consumers (tadpoles, macroinvertebrates and fishes) from these ponds and used stable isotope ratios of carbon (13C/12C) and nitrogen (15N/14N), to quantify the spatiotemporal dynamics of the food webs in these tropical ponds. There were no relationships between vertical structure of the food webs and the environmental gradients associated with the ponds. Consumers within these ponds exhibited high trophic variability, with multiple taxa occupying more than one trophic position across space or time. Consumers from larger ponds had a greater degree of trophic redundancy. More shaded ponds supported food webs that had lower trophic diversity. More permanent ponds had significantly greater trophic diversity as well as a greater range of basal resource diversity. The breeding ponds utilised by tadpoles and macroinvertebrates are patchily distributed across space and time. In these dynamic habitats, a feeding strategy of trophic generalism and plasticity enables consumers to exploit a broad range of resources and promote species coexistence. These results suggest that high diversity in tropical ponds does not necessarily translate into specialisation of trophic function.

Environmental, land cover and land use constraints on the distributional patterns of anurans: Leptodacylus species (Anura, Leptodactylidae) from Dry Chaco.

Subtropical dry forests are among the most vulnerable biomes to land transformation at a global scale. Among them, the Dry Chaco suffers an accelerated change due to agriculture expansion and intensification. The Dry Chaco ecoregion is characterized by high levels of endemisms and species diversity, which are the result of a variety of climates and reliefs, allowing a wide variety of environments. The amphibian group exhibits a high richness in the Dry Chaco, which has been barely studied in relation to land cover changes. We used ecological niche models (ENMs) to assess the potential geographic distribution of 10 Leptodactylus species (Anura, Leptodactylidae), which are mainly distributed within the Dry Chaco. We characterized these distributions environmentally, analyzed their overlap with land cover classes, and assessed their diversity of ecoregions. Also, we evaluated how these species potential distribution is affected by the transformation of land, and quantified the proportional area of the potential distribution in protected areas. We found that temperature seasonality is the main constraint to the occurrence of the species studied, whose main habitats are savannas, grasslands and croplands. The main threats to these species are the effects of climate change over spatial patterns of seasonality, which could affect their breeding and reproduction mode; the loss of their natural habitat; the exposure to contaminants used by intensive agriculture and their underrepresentation in protected areas.

Contribución al conocimiento de las aves presentes en la costa rioplatense de los partidos de Quilmes y Avellaneda (Buenos Aires, Argentina)

En este trabajo se presentan nuevos registros de aves para la costa rioplatense de los partidos de Quilmes y Avellaneda (Provincia de Buenos Aires, Argentina). La zona estudiada incluye dos áreas protegidas: Reserva Natural Municipal Los Sauces y el Parque Natural y Reserva Ecológica Municipal Selva Marginal Quilmeña, como también sectores sin categoría de conservación, abarcando en conjunto más de 300 hectáreas. Las observaciones se realizaron tanto por el Club de Observadores de Aves de Bernal como por estudiantes de la Facultad de Ciencias Naturales y Museo (Universidad Nacional de la Plata). Se adiciona un total de 31 especies nuevas en relación a trabajos anteriores, pertenecientes a las familias Tinamidae (1), Falconidae (1), Anatidae (2), Ardeidae (1), Rallidae (3), Strigidae (2), Cuculidae (1), Alcedinidae (1), Furnaridae (7), Sturnidae (1), Motacillidae (1), Thraupidae (2), Tityridae (1), Tyrannidae (5), Icteridae (2). Destacan los registros de Spartonoica maluroides (Espartillero enano) y Asthenes hudsoni (Espartillero pampeano), ambas catalogadas como vulnerables, además de varias especies categorizadas como escasas y sensibles frente a disturbios antropogénicos. También se ha observado un ejemplar de Icterus croconotus (Matico), una especie natural de la ecoregión del Chaco Húmedo. Cabe señalar el registro de Acridotheres cristatellus (Estornino crestado), ave introducida en nuestro país, cuyo impacto en las especies nativas tanto de aves como de otros animales es desconocido. Con esta contribución, se adicionan registros con valor conservacionista y el número de especies observables pasa de 124 a 155 para éste área, que se encuentra bajo un importante impacto antrópico y es considerado un posible corredor biológico entre las reservas Costanera Sur y Punta Lara.

Geographical Variation of Deltamethrin Susceptibility of Triatoma infestans (Hemiptera: Reduviidae) in Argentina With Emphasis on a Resistant Focus in the Gran Chaco.

Chagas disease is one of the most important parasitic infections in Latin America. The main vector of the protozoan Trypanosoma cruzi in America is Triatoma infestans, a blood-sucking triatomine bug who is widely distributed in the Gran Chaco ecoregion. Control programs in endemic countries are focused in the elimination of triatomine vectors with pyrethroid insecticides. However, chemical control has failed in the Gran Chaco over the last two decades because of several factors. Previous studies have reported the evolution of different levels of resistance to deltamethrin in Tri. infestans Recently, very high resistance has been found in the central area of the Argentine Gran Chaco. However, the origin and the extension of this remarkably resistant focus remain unknown. The aim of this study was to evaluate the geographical variation of deltamethrin susceptibility of Tri. infestans in different endemic provinces of Argentina, with emphasis in the center of the Argentine Gran Chaco ecoregion where this main vector has not been reduced. Populations of Mendoza, San Juan, Santiago del Estero, and Tucumán provinces were all susceptible. Resistant populations were only detected in the province of Chaco, where a mosaic resistant focus was described at the Güemes Department. It was characterized into three pyrethroid resistance categories: susceptible, low, and highly resistant populations. We found the populations with the highest resistance levels to deltamethrin, with resistant ratios over 1000.

New records of the Endangered Chacoan peccary Catagonus wagneri suggest a broader distribution than formerly known

AbstractThe Chacoan peccary Catagonus wagneri is the rarest and most threatened of the three extant species of peccary. Its presence has been recorded in the northern Dry Chaco ecoregion, which spans northern Argentina, western Paraguay and south-eastern Bolivia. However, distribution models based on its occurrence in Argentina have predicted that suitable habitat extends southwards into central Argentina, where the species was not previously recorded. We present several records of the species outside the currently accepted distribution, including the first two records in the west of Córdoba province, > 650 km south of the southern limit of the previously known distribution. The discovery of the Chacoan peccary in central Argentina could serve as a justification for the protection of Chacoan forests in this region, where deforestation rates are among the highest worldwide.

Kdr mutations in Triatoma infestans from the Gran Chaco are distributed in two differentiated foci: Implications for pyrethroid resistance management

Point mutations in the voltage-gated sodium channel, the primary target of pyrethroid insecticides, have been associated with the resistance in Triatoma infestans, an important vector of Chagas’ disease. Hence, the sustainability of vector control programs requires the implementation of resistance management strategies.We determined the sensitivity of the molecular assays previously designed for early resistance detection to be used in pooled samples from a wide area of the endemic region, and validated them for their routine use in control campaigns for the monitoring of insecticide resistance in T. infestans. Consequently, we used these methods to examine the distribution of resistance-associated mutations in the sodium channel gene in populations of T. infestans from the Argentinean and Bolivian Gran Chaco.The PASA and REA assays tested proved sensitive enough to detect kdr SNPs in pooled samples, indicating these assays are suitable for routine screening in insecticide resistance surveillance. Two geographically differentiated foci were detected in T. infestans populations from the Argentinean and Bolivian Gran Chaco, with populations on the Bolivian-Argentinean border carrying L1014F mutation, and those from the Argentinean Chaco carrying L925I mutation. In all highly resistant populations analyzed, one of both kdr mutations was present, and toxicological assays determined that all pyrethroid resistant populations analyzed herein were sensitive to fenitrothion.The principal cause of pyrethroid resistance in T. infestans from the Gran Chaco ecoregion is kdr mutations in the sodium channel. Different levels of resistance occur in different populations carrying identical mutation, suggesting the existence of contributory mechanisms.

Predator‐induced phenotypic plasticity in an arid‐adapted tropical tadpole

AbstractAdaptive phenotypic plasticity is widespread and involves diverse phenotypes. Key environmental stressors, such as predation risk, can simultaneously induce changes in multiple traits, but the magnitude of response is dependent upon the environmental conditions. Species that utilize temporary ponds are expected to exhibit stronger predator‐induced responses in the form of morphology than behaviour (i.e. reduced activity) to meet the demands of rapid development by maintaining high foraging activity while reducing predation risk via morphologically plastic traits. In a laboratory experiment, I examined the effects of predator chemical cues and conspecific alarm cues on activity, development and morphology on Leptodactylus bufonius tadpoles. This species has terrestrial oviposition and completes the early part of its development outside of ephemeral and temporary ponds in the Gran Chaco ecoregion of South America. Tadpoles in the predator treatments exhibited both behavioural and morphological predator‐induced plastic responses. Tadpoles tended to possess shorter, deeper tails when exposed to predators. The greatest reduction in activity was observed in tadpoles exposed to both predator and conspecific alarm cues, which subsequently resulted in the slowest development. Temporary and ephemeral pond adapted species with terrestrial oviposition may capitalize on a head start in development by being able to afford reduced growth rates via a reduction in activity. This may occur when the constraints imposed by pond hydroperiod (e.g. risk of pond drying) are relaxed when compared with species with aquatic oviposition, which must undergo all stages of development during the pond's hydroperiod. Thus, in addition to the predator and hydroperiod gradients, examining phenotypically plastic responses along a ‘terrestriality gradient’ in a comparative framework would provide insights as to the costs and benefits of increasing terrestriality in anuran reproductive modes to environmental stressors.

Environmental drivers of anuran calling phenology in a seasonal Neotropical ecosystem

AbstractTemporal variation represents an important component in understanding the structure of ecological communities and species coexistence. We examined calling phenology of an assemblage of anurans in the Gran Chaco ecoregion of Bolivia by deploying automated recording devices to document nocturnally vocalizing amphibians nightly at seven ponds from 20 January 2011 until 31 October 2011. Using logistic regression, we modelled the relationships between temperature, rainfall and photoperiod with calling activity. There was a distinct seasonal effect with calling activity concentrated in the rainy season with no species detected during the dry season from June until the end of October. Calling activity was positively and significantly correlated with photoperiod in 9 of the 10 species analyzed, but there were distinct species‐specific relationships associated with rainfall and temperature. All of these species utilize ephemeral ponds as breeding sites, which can account for their reliance on rainfall as an important driver in calling activity. Two prolonged breeders exhibited similar seasonal breeding patterns across the rainy season, but differed in their response to daily abiotic factors, which might be attributed to the constraints imposed by their reproductive mode. Explosive breeders needed several days of rain to elicit calling. Two pairs of congeners had distinct species‐specific relationships between their calling activity and abiotic factors, even though the congeners shared the same reproductive mode, suggesting that the reproductive modes vary in the constraints imposed on calling activity. The patterns observed suggest that calling phenology of tropical anurans is determined by the interaction of exogenous factors (i.e. climatic variables) and endogenous factors (i.e. reproductive modes).

Latitudinal Gradient of Biting Midges in the GenusCulicoides(Diptera: Ceratopogonidae) in Argentina and Bolivia

Abstract We provide the first records of 8 species of biting midges in the genus Culicoides (Diptera: Ceratopogonidae) in a wide latitudinal gradient of the Yungas Ecoregion in Argentina and the Chaco Ecoregion in Bolivia, including a map of their distribution, and an updated checklist of species in the study area. Additional locality records were obtained from published articles and from specimens collected in these and other ecoregions in both countries. Included are the first Argentinean records of Culicoides crescentis Wirth & Blanton and C. pampaensis Spinelli & Wirth from Salta Province; C. caridei Brethes, C. crescentis, C. guttatus Coquillett, C. insignis Lutz, C. pampaensis, and C. venezuelensis Ortiz & Mirsa from Jujuy Province, and C. saltaensis Spinelli & Wirth and C. pampaensis from Tucuman Province. In addition, the first records of C. brasilianum Forattini, C. crescentis, and C. guttatus are provided from Bolivia.

Ontogenetic shifts in ambush-site selection of a sit-and-wait predator, the Chacoan Horned Frog (Ceratophrys cranwelli)

Ontogenetic shifts in habitat use are widespread among vertebrates. These niche shifts are often attributed to age-specific patterns of resource use, which are correlated with changes in morphology, diet, and habitat. We examined the ontogeny of ambush-site selection in a sit-and-wait predator, the Chacoan Horned Frog (Ceratophrys cranwelli Barrio, 1980), in the Gran Chaco ecoregion of Bolivia. We quantified covariation in microhabitat and morphological variables and tested for microhabitat selection against randomly selected points. We identified an ontogenetic shift in ambush-site selection between adult and metamorph frogs. When compared with random points, metamorphs selected a subset of available habitat, whereas adult frogs did not appear to select ambush sites. Metamorphs, compared with adults, selected ambush sites farther from a pond’s edge with a greater proportion of dry mud. The metamorph of C. cranwelli may have selected ambush sites based on spatial distribution of certain size classes of prey. Alternatively, metamorphs could have selected sites to minimize asymmetric agonistic intraspecific interactions with adults. These mechanisms are not mutually exclusive and probably occur in concert. Habitat selection and ontogenetic niche shifts by these organisms provide insights to the trade-offs between foraging strategy and mortality risk.

Amphibian assemblages in dry forests: Multi-scale variables explain variations in species richness

Pond-breeding amphibians depend on several habitats and scales throughout their complex life cycle. For pond-breeding amphibians inhabiting seasonal dry forests, landscape is composed of a set of scarce and ephemeral isolated ponds surrounded by a contrasting matrix. The Chaco ecoregion is one of the most extensive dry seasonal forests in South America. In the last four decades, agricultural expansion and transformation from subsistence livestock farming to commercial livestock production have triggered dramatic deforestation processes all across the region, changing landscape composition and configuration. We postulate that richness of pond-breeding amphibians in the Chaco dry forest is negatively associated with pond hydroperiod and isolation, and terrestrial matrix degradation. Pond attributes and landscape configuration and composition were used to fit a statistical model to predict amphibian species abundance and richness in Arid Chaco ponds. Our results show that amphibian abundance and species richness in Chaco ponds is related to local and landscape predictors. Isolated and ephemeral ponds located in degraded shrublands showed low species richness values in Chaco dry forests. These results suggest that present-day land-use changes in the Chaco will have important effects on amphibians assemblages from the region, because such changes imply not only the loss of native vegetation but also a reduction of rural people devoted to extensive livestock production, where the artificial ponds used for watering livestock are also used as breeding sites by Chaco amphibians.

Activity and reproductive patterns of lizards in the Chaco of Argentina

We studied the activity and breeding pattern of dominant lizard species in the Arid Chaco, the southernmost subregion of the Chaco ecoregion (Chancaní Reserve, Córdoba province, Argentina). Lizards were captured with pitfall traps over a 4-year period. In total, 1449 individuals belonging to 11 of the 12 lizard species recorded in the area were trapped. Of these, we selected six species for a detailed analysis: Teius teyou and Stenocercus doellojuradoi accounted for 63% of the captures, Tropidurus etheridgei, Liolaemus chacoensis and Homonota fasciata accounted for 32%, and 5% comprised Leiosaurus paronae and the remaining five species. All the studied species were active during the warm–rainy season (September to March). Monthly lizard captures were highly correlated with monthly mean temperature and rainfall. No captures occurred during the remaining months of the year. All reproductive tactics known for the Chaco lizards were observed in Chancaní, including single clutch in a short breeding season in summer or autumn, as well as an extended breeding season with multiple clutches. Stenocercus doellojuradoi and L. paronae showed a singular reproductive timing, suggesting the occurrence of egg retention. Compared with sub-tropical Chaco sites, the Arid Chaco only differs in the lack of winter activity, resulting from the lower temperature and rainfall regime of our study site.

Rainwater harvesting in Dry Chaco: Regional distribution and local water balance

Rainwater harvesting (RWH) has been essential for the establishment of human settlements in many dry regions of the world that lacked suitable surface or groundwater resources. A vast fraction of the South American Dry Chaco ecoregion still relies on RWH to support, not only livestock production, but domestic and industrial uses as well. As a result, water capture and storage infrastructure is widely disseminated throughout the region. In this paper we characterized the most typical RWH systems in two contrastingly developed sub-regions of Dry Chaco, ranging from extensive ranching to intensive beef and dairy production (central Argentina and western Paraguay, respectively). In each sub-region, we quantified RWH systems density, spatial distribution and associations with landscape features; furthermore, we illustrated how the daily dynamic of water stock in a typical RWH system contributes to assess their capture and storage efficiency. We found that randomly distributed low sophisticated RWH systems prevailed in central Argentina, while clustered distributed high sophisticated ones were more common in western Paraguay. RWH systems density was ten times higher in western Paraguay (0.94 vs. 0.098 units/km2), showing an exponential association with land cleared fraction and proximity to villages. The daily dynamic of water stock of the RWH impoundment showed that water harvest events were exponentially associated with precipitation magnitude events (R2 = 0.86), while annual water losses were explained by infiltration and evaporation fluxes (59 vs. 41%, respectively). Across both sub-regions, RWH accounts for less than 1% of the annual precipitation, playing a minor role on the regional water balance; however at a local level, they can affect several hydrological fluxes including the onset of groundwater recharge and the mitigation of extreme runoff events.