Southern Pampas Research Articles

You are what you eat: is the apple snail Pomacea canaliculata a macrophytophage or a detritivore in its native range (southern Pampas, Argentina)?

You are what you eat: is the apple snail Pomacea canaliculata a macrophytophage or a detritivore in its native range (southern Pampas, Argentina)?

Seasonal changes in habitat use and behavior of the threatened Pampas meadowlark Leistes defilippii

The Pampas grasslands’ biodiversity is severely threatened by habitat modification, as is the case for the Pampas meadowlark ( Leistes defilippii). Here we study the areas used by the species throughout the year in the Southern Pampas of Argentina, in association with seasonal changes in behavior, in an attempt to provide information for its effective conservation. We selected four grassland sites with livestock activities in which we studied vegetation characteristics and the abundance and behavior of the Pampas meadowlark, during breeding and non-breeding seasons. The species was absent in sites with higher bare ground cover and lower cover of >30 cm vegetation, and with high proportions of forb, shrub or exotic grass species. In those areas where the Pampas meadowlark was present during the breeding season, its abundance was higher where the grassland was entirely dominated by native grasses, and abandoned another site when the grassland became dominated by introduced plant species, after the breeding period. We are the first to report the behavior of a Pampas meadowlark population throughout an entire year with its seasonal changes. Our results and description of the behavior throughout the year highlight the importance of structural heterogeneity of the grasslands, determined by a low intensity of grazing, for the breeding of the Pampas meadowlark. Also, features associated with breeding habitat can’t predict the presence of flocks during the non-breeding season, as noted in our results for vegetation structure, but vegetation composition, food availability and landscape variables could play an important role in determining which areas serve as appropriate habitat during the non-breeding season, when large flocks search the grasslands for food. A better understanding of the habitat requirements and the use of space at different scales by the Pampas meadowlark will allow the identification of the most urgent and effective measures for its conservation.

Nitrogen deficiency in maize fields of the Southern Pampas does not affect kernel number but reduces weight per kernel.

Nitrogen (N) requirement of maize has been increasing over the past decades, but there has been a lack of adjustment in fertilization management practices across different regions in Argentina. The higher N requirement in modern hybrids is associated with a higher post-flowering N accumulation. Additionally, soil fertility in the Argentina Pampas has consistently decreased in recent years. Whether the effects of N deficiency are expressed in the post-flowering period is still unclear at field level. The objective of this work was to quantify the yield reduction attributed to N deficiency and to identify the physiological basis of this effect at the field level for typical high-tech farms across the south-eastern Pampas of Argentina. Nineteen experiments were conducted during the 2020/2021 growing season in the south-eastern Pampas, evaluating two N managements i) Farmers' N level; ii) High N input. Results showed that the additional N input increased grain yield by an average of 6.4% (average grain yield difference of 712 kg ha−1). Weight per kernel was the only yield component that responded to N fertilization. Farmers' N management did not affect N accumulation or growth-related variables such as leaf area index, green leaves per plant, PAR interception, nitrogen sufficiency index until flowering, but the farmers' N level reduced these variables during the grain filling period leading to differences in aerial biomass and N accumulated at physiological maturity. Farmers' N level led to decreased post-flowering N uptake during grain filling period, which reduced the photosynthetic capacity of the canopy. These findings suggest that N management strategies and models need to be reviewed for high-tech maize systems.

Seasonal variation of body condition in feral horses at Tornquist Park, Southern Pampas, Argentina

Seasonal variation of body condition in feral horses at Tornquist Park, Southern Pampas, Argentina

Influence of climate variability on fire generation

This study evaluates the occurrence of dry and wet events and their relationship with fires in southern Pampas, Argentina. The intensity and magnitude of dry and wet events were determined based on the regional series of the Standardized Precipitation and Evapotranspiration Index (SPEI) for the 2000-2021 period. The data obtained were related to the El Niño Oceanic Index (ONI) to analyze the incidence of El Niño and La Niña events in generating them. Fires in the region were detected using remote sensing techniques, considering the number of events, their intensity, extent, and duration. The southern Pampas experiences marked rainfall variability, with 15 dry events, 11 wet years, and 2 standard years recorded for the period analyzed. Extreme dry years were, on average, more intense (SPEI = -2.14) and occurred mainly during the negative ONI phase. In contrast, extreme wet years exhibited lower intensity (SPEI = 1.98), and only the most intense ones were related to neutral ONI phases. We analyzed a representative extremely dry (ED) and an extremely wet events (EW) to interpret the relationship between climate variability and the spatiotemporal variability of fires in the region. It was observed that during the EW event (2014-2015, SPEI = 1.52, and El Niño event until 2015) the number of fires was higher compared to an ED event (2008-2009, SPEI = -2.22, and La Niña event during 2008), with 460 and 205 fires, respectively. The intensity was higher in the EW (302.6 and 31.5 MW), while the area presented considerable differences (1722 and 815.5 km2, respectively). Finally, the duration of the fires was shorter in ED than in EW (6 and 8 months, respectively). These results were related to vegetation health (NDVI = 0.29 and 0.41 and EVI = 0.15 and 0.21 in ED and EW, respectively) and changes in land covers. This study provides a solid database for future research efforts and sustainable land management plans.

How effective is camera trapping in monitoring grassland species in the southern Pampas ecoregion?

We assessed the efficiency of camera trapping in monitoring bird and mammal species in the grasslands of Tandilia Mountains by calculating the naïve occupancy, capture rate, and time to the first detection for each species. We compared the observed richness with the reported richness from online databases. We performed species accumulation curves to estimate the sampling effort necessary to detect bird species. We detected 50 bird and 15 mammal species. The top 5 bird species (Chalk-browed Mockingbird, Rufous-collared Sparrow, Rufous Hornero, Great Pampa-Finch, and Spotted Nothura) accounted for 48% of all detected individual birds, with naïve occupancy of 21-25% and mean times for the first detection between 6 and 9 days. The top 5 mammal species (Pampas fox, Large hairy Armadillo, European hare, Molina’s hog-nosed skunk, and Geoffroy’s cat) accounted for 81% of all detected individual mammals, with naïve occupancy of 32-77% and mean times for the first detection between 4 and 7 days. A sampling effort of 2 weeks was the optimal balance between effort and result qualities. We detected all the reported richness of mammals and half of the reported grassland-associated birds. We provide valuable information for future grassland species monitoring with camera trapping in Neotropical grasslands.

First description of courtship and copulation in Pristidactylus casuhatiensis (Squamata, Leiosauridae)

BackgroundReproductive behaviour under natural conditions is hard to record, especially in rare and cryptic species, such as the Casuhatien anole (Pristidactylus casuhatiensis). This medium size lizard is endemic to the Sierras Australes Bonaerenses, a rocky outcrop in the Southern Pampas of Argentina.MethodsDuring spring and summer from 2018 to 2022, we surveyed five hills at above 600 m altitude, where specimens were known to occur. Every time we detected a courtship or copulation event, we took photographs of the specimens for their individual identification, and recorded the body temperature of the participating individuals as well as air temperature, wind speed and relative humidity. We recorded the duration in minutes of each phase of the event (immobilization, juxtaposition of the cloacae followed by copulation, and finally, restraint and separation) and described the main habitat features of the site where it happened.ResultsWe detected 12 reproductive events; all of them occurred in October and November, on Funke, Puntudo and Tres Picos hills, mostly between 1300 and 1700 h. The mean duration of each copulation phase was 6 min (95% CI = ± 1.4, n = 10), 4.3 min (95% CI = ± 1.8, n = 10) and 3.8 min (95% CI = ± 3.42, n = 10), respectively.ConclusionThe reproductive activity of the Casuhatien anole is concentrated in the spring, particularly in the early afternoon, following the patterns described for other species of lizards. During these events, the greatest exposure of individuals could make them more vulnerable. This, together with other features related to their reproductive behaviour revealed in this paper may contribute to the planning of conservation actions.

Ancient mitogenomes from the Southern Pampas of Argentina reflect local differentiation and limited extra-regional linkages after rapid initial colonization.

This study aims to contribute to the recovery of Indigenous evolutionary history in the Southern Pampas region of Argentina through an analysis of ancient complete mitochondrial genomes. We generated DNA data for nine complete mitogenomes from the Southern Pampas, dated to between 2531 and 723 cal BP. In combination with previously published ancient mitogenomes from the region and from throughout South America, we documented instances of extra-regional lineage-sharing, and estimated coalescent ages for local lineages using a Bayesian method with tip calibrations in a phylogenetic analysis. We identified a novel mitochondrial haplogroup, B2b16, and two recently defined haplogroups, A2ay and B2ak1, as well as three local haplotypes within founder haplogroups C1b and C1d. We detected lineage-sharing with ancient and contemporary individuals from Central Argentina, but not with ancient or contemporary samples from North Patagonian or Littoral regions of Argentina, despite archeological evidence of cultural interactions with the latter regions. The estimated coalescent age of these shared lineages is ~10,000 years BP. The history of the human populations in the Southern Pampas is temporally deep, exhibiting long-term continuity of mitogenome lineages. Additionally, the identification of highly localized mtDNA clades accords with a model of relatively rapid initial colonization of South America by Indigenous communities, followed by more local patterns of limited gene flow and genetic drift in various South American regions, including the Pampas.

Abundance, distribution, and associated forage losses of pest grasshoppers (Orthoptera: Acrididae) in the Argentine Pampas.

The goal of this study was to assess the status of Dichroplus elongatus and Borellia bruneri as actual agricultural pests in the Argentine Pampas by determining their abundance, distribution, and associated forage loss. The study was conducted in Laprida and Tandil, two counties in Buenos Aires province. In each county 20 sampling sites were established and monitored from 2012 to 2018. B. bruneri was more abundant and with a wider distribution in Laprida (91.4% of the sites) than in Tandil (42.1% of the sites) while D. elongatus abundance was significantly higher from 2012 to 2016 in Tandil than in Laprida and its distribution was wide in Laprida (75% of the sites) and very wide in Tandil (77.14%). Under field-cage conditions forage loss caused at three different densities (8, 16, and 32 ind/m2) of D. elongatus and B. bruneri adults on a pasture of Festuca arundinacea was estimated. Forage loss caused by D. elongatus was significantly higher than that caused by B. bruneri. Dichroplus elongatus caused a significant decrease in biomass at the three densities respect to the control, while B. bruneri only caused a significant decrease at the highest density. Our study suggests that although the gomphocerine B. bruneri is an abundant and widely-distributed species capable of doing some damage in the grasslands of the southern Pampas, it is comparatively much less harmful than the melanopline D. elongatus.

Established but not spreading: the tropical invasive snail Melanoides tuberculata in a geothermally warmed channel in temperate Southern Pampas

Melanoides tuberculata is a freshwater snail native to Old World tropical areas but has invaded tropical and subtropical regions around the world. In Argentina, populations established in natural environments were reported from northeastern tropical provinces. Here we report for the first time the presence of M. tuberculata in a geothermally warmed channel in temperate Southern Pampas. We mapped its distribution in the channel, searched for its presence in five nearby basins, estimated the risk of establishment and expansion in Argentina with distribution models and analyzed shape variation through geometric morphometrics. Melanoides tuberculata was recorded exclusively in the channel in sites with temperatures between 20 and 40°C, with almost no overlap with other snails. No evidence of M. tuberculata was found in nearby basins. The distribution model predicted that only northernmost areas from Argentina are suitable for this species, where it could impact snail communities and food webs if introduction through the aquarium trade is not prevented. The absence of males indicates parthenogenetic reproduction and probably a recent invasion. Shell shape variation in this population, 15 % of which is attributable to allometry, encompasses the shapes of specimens from other South American populations, suggesting that all belong to the same lineage.

Escondido en los pajonales: registros fotográficos y variación fenotípica de Leopardus pajeros en la Patagonia chilena

Hidden in the southern Pampas: Photographic records and phenotypic variation of Leopardus pajeros The Southern pampas cat (Leopardus pajeros) is a small felid whose range is restricted to Argentina and southern Chile. There is very little specific literature and its natural history remains an enigma. In the present note, we report four records of the Southern pampas cat in Patagonia and provide photographs and detailed descriptions, from which we propose a phenotypic spectrum ranging from light gray, to brownish gray, to rusty red.

Evaluation of agrobiodiversity and its trophic interactions as an indicator of sustainability in productive systems

Agriculture has intervened, modified, and simplified ecosystems to obtain some goods and services. Conventional o industrial agriculture emphasizes the use of external inputs and the homogeneity of the landscape; agroecology promotes biodiversity to maximize biological interactions and their ecosystem services. The objective was to evaluate agrobiodiversity and its trophic interactions as an indicator of sustainability by comparing: industrial productive systems, and agro-ecological and semi-natural sites in the southern Pampas region. Samples were taken of mammals, birds, arthropods, and vegetation; with different indices, the food chains and the state of the system were evaluated. The results show that agricultural intensification simplifies landscape structure with a loss of biodiversity and the absence of functional groups (herbivores and nectarivorous). In agroecological wheat, the highest density of links was found and in agroecological pastures the highest grouping coefficient, this reveals greater cohesion and integration among the components of the system and more mechanisms of self-regulation. The agroecological diversity Index showed no differences between the management, this could be related to the presence of a biological corridor in the conventional field that would be increasing biodiversity. The key to achieving sustainable agroecosystems is to procure biodiverse landscapes with patches and corridors of shrub and herbaceous species.

Relationship between pest grasshopper densities and climate variables in the southern Pampas of Argentina.

Grasshoppers are one of the most predominant insects in the grasslands of the southern Pampas. In this region, Dichroplus elongatus, Dichroplus maculipennis, Dichroplus pratensis and Borellia bruneri are the most abundant species and have the greatest economic importance. This study aimed to assess the relationship between temporal changes in the density of these species and climate variables associated with temperature and rainfall over an 11-year study period., We monitored 22 sites in different areas of Laprida county from 2005 to 2016. A total of 25 grasshopper species were collected. The most abundant species were D. maculipennis and B. bruneri which reached the highest densities from 2008-2009 to 2010-2011. The rainfall accumulated from September (RAS) to the sampling date and the number of rainy days (RD) largely explained the density variation of B. bruneri. Besides RD and RAS, winter rainfall, rainfall accumulated from October to the sampling date, and thermal amplitude of October (TAO) influenced the density of D. maculipennis. Our results indicated that seasons with less rainfall and fewer RD favored these two species' abundance. We identified that the RD and TAO contributed significantly to variations in the density of D. elongatus. In contrast to the other two species, we recorded D. elongatus in seasons with high rainfall and high RD. A better understanding of the climate influence on the life cycle of these economically important insects may identify key factors in their population dynamics which in turn may improve management options.

Linking Farmers' Perception of Biodiversity, Subjective Well-being and Conservation in the Tandilia System in the Southern Pampas of Argentina

Linking Farmers' Perception of Biodiversity, Subjective Well-being and Conservation in the Tandilia System in the Southern Pampas of Argentina

Eumysops marplatensis Olivares and Verzi 2015 (Rodentia, Hystricognathi) from the Plio-Pleistocene of the Northern Pampa in Argentina: Paleoenvironmental and paleobiogeographic implications

The tribe Myocastorini (Caviomorpha, Echimyidae) currently comprises living species inhabiting Central America from Honduras and extending throughout South America to Patagonia, in a wide variety of environments. This clade is well represented in the late Miocene-Pleistocene fossil beds of central and northern Argentina. Its diversification at high latitudes during part of the Cenozoic would be linked to the rise of open and progressively drier environments. Here we report the record of a myocastorine lower deciduous premolar (dp4) from the locality of Casilda, Santa Fe Province, in central Argentina. The Casilda fossiliferous level is correlated with part of the lithostratigraphic sequence from the elevated San Guillermo block in western Santa Fe province and may be assigned to palustrine clays. Based on recent studies of sequential stratigraphy and lateral correlation, neotectonics, and new dating using Optically Stimulated Luminescence performed in the Northern Pampa geomorphological region, the deposits that overlie those clays have been considered to be the Middle Pleistocene in age. According to this interpretation, the fossil-bearing level corresponds to the Pliocene-Early Pleistocene sensu lato and thus, this specimen is the first vertebrate recorded in that age for the Santa Fe Province. Based on an exhaustive comparison with dp4 of different caviomorph species, the specimen is assigned to Eumysops marplatensis. The occurrence of this extreme open-habitat specialist at Casilda supports previous paleoenvironmental interpretations for the Northern Pampa that indicate open or semi-open environments for the Plio-Pleistocene. Furthermore, the presence of the three modern species of Eumysops, and other vertebrates, in the Northern and Southern Pampas geomorphological regions during the Pliocene-Early Pleistocene suggest a paleobiogeographic connection between both regions.

A Maxent Predictive Model for Hunter-Gatherer Sites in the Southern Pampas, Argentina

The following paper presents the results of a Species Distribution Model (SDM) for grassland hunter-gatherer archaeology sites in the southern Pampas region of Argentina. The goal of this exploratory model is to provide a complementary survey model for the detection of archaeological sites in this region, which will also help characterize and discuss site locations and regional distribution patterns of hunter-gatherer occupations. Even in this largely homogenous and highly dynamic landscape, SDMs can help guide archaeological surveys by identifying some environmental variables affecting hunter-gatherer decisions, and can provide insights into mobility and archaeological settlement patterns. Among the available tools for SDM, Maximum Entropy Modeling (Maxent) is one of the most widely used approaches in archaeological predictive modelling. After controlling for bias and adjustment of several modifiable parameters, the Maxent software provided a potentially effective predictive model to direct future archaeological survey and heritage management projects. The results of this research suggest that watercourses and slope were the key environmental factors influencing the distribution of hunter-gatherer archaeological sites in the southern Pampas region.

Bacterial Diversity in Calcium Carbonate Paleo Accretions (Tosca) in the Southern Pampas, Argentina

Paleosoil accretions of carbonates in the Tandilia system (Southern Pampas, Argentina) dated to the lower/middle Pleistocene age are locally referred to as tosca. The characterization of this indurated layer of carbonates were analyzed via a biophysicochemical approach, including, physicochemical analysis of soils, mineral x-ray diffraction of the tosca, and microbial diversity of modern soils and tosca layers. The minerals found within tosca were calcite, albite, muscovite, quartz, orthoclase and dolomite in order of most to least abundant. The microbial metataxonomics of tosca was described for the first time. The most abundant microorganisms in tosca were g_Geobacter, g_Pseudonocardia and p_Gemmatimonadetes2 and redundancy analysis of physicochemical parameters and relative microbial abundances revealed positive correlations between Nitrospirae and calcium ions, while mineral and microbial correlations associated Gemmatimonadetes and Firmicutes with calcite and dolomite presence. Magnetospirillum, Geobacter and Bacillus were present in the tosca and the soil above, indicating possible prenucleation sites for calcite and dolomite. Core microorganism abundance was >80% throughout horizons including tosca, hence either microbial entrapment via calcium carbonate precipitation or microbial leaching occurred within this layer.

Technology, subsistence, and mobility of Middle to Late Holocene hunter-gatherers in the southern Pampas: new archaeological data from Las Toscas shallow lake (Argentina)

Despite a long history of hunter-gatherer occupation in the Pampas region starting at the end of the Pleistocene, the known archaeological record is still sparse for some periods, such as the Middle Holocene. Here, we present new archaeological data from Las Toscas shallow lake, located in the inland plains of the southern Pampas, where systematic fieldwork revealed an abundant and diverse archaeological record resulting from hunter-gatherer occupation. The aims of this study were to establish the chronology of the occupations; to evaluate the use of faunal and lithic resources; and to contribute to the understanding of hunter-gatherer land use patterns. Archaeological evidence indicates that procurement, domestic, and ritual activities were conducted around the shallow lake during the Middle and Late Holocene, including hunting of terrestrial game; tool manufacture and repair; storing and use of mineral pigments; and likely human burial practices. Evidence also suggests that the use of this locality was not continuous but redundant and that this shallow lake was a persistent place for hunter-gatherers. Faunal data agrees with regional models that propose that Lama guanicoe was the main food resource during the second half of the Middle Holocene, although a taphonomic bias in favor of larger vertebrates cannot be ruled out. The lithic assemblages suggest that artifacts entered the locality mostly as part of individual toolkits and indicate a strong preference for orthoquartzite. Finally, bone remains of extinct fauna were recovered at the locality; however, a functional association between these remains and cultural material could not be demonstrated.

AGRICULTURA NATURAL EN LA PAMPA AUSTRAL ARGENTINA: EL CASO “MONTE CALLADO”

En La Pampa argentina son escasos los casos documentados de productores agroecológicos. En el campo “Monte Callado”, pampa austral, un productor familiar desarrolla desde 2001 una experiencia agroecológica inspirada en la agricultura natural de Fukuoka. Aquí caracterizamos sus principales aspectos ecológico-productivos y socio-económicos, y evaluamos preliminarmente su grado de autonomía (período 2014-2018). Se utilizó información cartográfica, entrevistas y se relevaron indicadores de biodiversidad. Se determinó un alto grado de diversificación e integración de subsistemas, y rasgos que favorecen la viabilidad socio-económica. Se registraron 11 cultivos extensivos, 31 hortícolas y 18 frutales. Cuenta con ganado vacuno para cría e invernada, aves, cerdos y vacas lecheras. No se utilizaron agroquímicos. La producción intensiva se destina mayormente al autoconsumo. La harina de trigo es la principal salida del sistema y principal ingreso monetario. La alta autosuficiencia alimentaria, el bajo uso de insumos externos y la comercialización directa en canales cortos son rasgos de una alta autonomía. Este caso evidencia la conveniencia del modelo agroecológico en pampa austral.

PALEONVIRONMENTAL RELEVANCE OF AMORPHOUS SILICA MICROFOSSILS IN HYDROMORPHIC PALEOSOLS, A COMPARATIVE STUDY WITH MODERN ANALOGOUS ENVIRONMENTS IN THE SOUTHERN PAMPAS, ARGENTINA

PALEONVIRONMENTAL RELEVANCE OF AMORPHOUS SILICA MICROFOSSILS IN HYDROMORPHIC PALEOSOLS, A COMPARATIVE STUDY WITH MODERN ANALOGOUS ENVIRONMENTS IN THE SOUTHERN PAMPAS, ARGENTINA