Nuevos sitios fosilíferos y evolución paleoambiental del cenozoico tardío del suroeste de Córdoba, Argentina

New fossil remains were found in Neogene and quaternary sedimentary sequences exposed in Alpa Corral and río San Bartolomé localities (Rio Cuarto Department, Córdoba, Argentina). They were assigned to Nopachtus cabrerai (Xenarthra, Cingulata, Glyptodontidae), Notiomastodon platensis (Proboscidea, Gomphotheriidae) and cf. Trigodon gaudryi (Notoungulata, Toxodontidae), and traces of the Scoyenia ichnofacies, as Taenidium barretti, were identified. Based on these findings, we conclude that: 1, the species Nopachtus cabrerai and cf. Trigodon gaudryi are registered for the first time in the Sierras Pampeanas region and support (along with the rest of the known taxa) a clear faunistic similarity to the Pampean region; 2, the beginning of the Neogene sedimentation in the Alpa Corral area (Las Barrancas river and San Bartolome river) would have started during the early Pliocene (Montehermosan Age); 3, the paleoenvironment would have been a fluvial system, with meandering canals interspersed with paleosols developed in floodplains with overflow deposits or abandoned meanders; 4, the paleontological and sedimentary record suggests a well-marked diachronism (from west-southwest to east-northeast) between the beginning of the Neogene sedimentation in the southern sector of San Alberto valley (late Miocene [Huayquerian Age]), the Alpa Corral region (early Pliocene [Monthermosan Age), and Río La Cruz valley (late Pliocene [Chapadmalalan Age]).

Surface water extent dynamics from three periods of continuous Landsat time series; subregional differences across Argentine plains

<p>The Pampean region in Argentina is an extensive plain characterized by abundant shallow lakes that fulfill many environmental, ecological, and social functions. This study aims to detect the multiannual lake area changes in this region during 2001-2009 using remote sensing, including lakes as small as ≥10,000 m² or 1 ha. Landsat scenes of the wet (2008-2009), normal (2006), and dry (2008-2009) seasons were obtained, and using remote sensing techniques, the number and area of shallow lakes were calculated. The spatiotemporal variation of shallow lakes was studied in different climate periods in eight singular subregions. Spatial associations between annual precipitation and lake number and area were analyzed through the development of a Geographic Information System (GIS) at a subregional scale. During the study period the total lake area in the Pampean region decreased by 5257.39 km²(62 %), but each subregion showed different responses to climatic events. In seven of them, the differences between climate periods prove to be statistically significant (P&gt;0.01). The relationship between precipitation and lake number and area revealed the domain of positive association. We conclude that climate factors play a dominant role in lake changes across the Pampean plains. However, other factors such as origin, topographic and edaphic characteristics intensify or mitigate changes in surface hydrology.</p>

Pleistocene Mammals from Pampean Region (Argentina). Biostratigraphic, Biogeographic, and Environmental Implications

The Pampean Region contains sedimentary sequences with abundant mammal fossil records, which constitute the chronological outline of the Plio–Pleistocene of South America. These classic localities have been used for more than a century to correlate with other South American regions. Throughout this time, a series of misinterpretations have appeared. To understand the stratigraphic significance of these localities and the geochronological situation of each unit referring to the Pleistocene, a critical historical study of the antecedents was carried out, evaluating the state of each unit. The biostratigraphic studies of the Pampean Region’s mammalian faunas improved the understanding of biogeographic changes taking into account the environmental fluctuations of the Pleistocene.

Six Species of Diaporthe Associated with Phomopsis Stem Canker of Sunflower in Southern Pampean Region of Argentina

A survey of 67 commercial fields in 19 locations was conducted in the southern Pampean region of Argentina for Phomopsis stem canker of sunflower (Helianthus annuus L.) between 2014 and 2019. A total of 210 plants having typical symptoms of Phomopsis stem canker were randomly sampled, and fungal isolation was performed. Of the 187 isolates of Diaporthe that were recovered, 94% of the isolates showed morphological characteristics similar to D. helianthi, 3% to D. gulyae, 1% to D. caulivora, 1% to D. sojae, 0.5% to D. kongii, and 0.5% to D. longicolla. Following morphological characterization, the identity of the six morpho-species was confirmed by phylogenetic analyses of β-tubulin, translation elongation factor 1-α, and internal transcribed spacer gene regions. Koch’s postulates were completed for the six fungi by inoculating one susceptible sunflower hybrid with one isolate each of the six species of Diaporthe using the stem-wound inoculation method. Seven days postinoculation, significant differences in disease severity were observed between the six isolates (P < 0.0001), with D. helianthi and D. gulyae isolates causing significantly greater disease severity. To our knowledge, this is the first report of D. kongii, D. longicolla, D. caulivora, and D. sojae associated with Phomopsis stem canker of sunflower in Argentina.

Fossil record of a Characiform in the Monte Hermoso Formation (lower Pliocene), Buenos Aires, Argentina. Palaeobiogeographical implications

The fossil record of fishes from the Farola de Monte Hermoso locality (lower Pliocene) in the southern Buenos Aires province, Argentina, shows an unusual composition. The locality at the southern boundary of the Brazilian Ichthyogeographic Realm. However, its fossil record is composed of fossil fishes that are not necessarily related to Brazilian lineages, namely indeterminate siluriforms, trichomycterid catfishes, and percomorphaceans. The aim of the present contribution is to describe and report for the first time isolated specimens belonging to Characidae fishes. In the Pampean region the fossil record of characids is restricted to Oligosarcus Günther, 1864 sp. from the late-middle Pleistocene. The present finding fills a temporal gap between the Paleogene and Quaternary reports and indicates that Brazilian fish lineages were present in the area by early Pliocene times, and may constitute an indirect evidence of the evolution of the basins in the southern Pampean Area.

Cuenca hidrográfica agropecuaria y evolución de los servicios ecosistémicos en la región sur pampeana Argentina

Los modelos productivos actuales incluyen doble cultivo anual, aumento de agroquímicos, fragmentación de la biodiversidad y alteración de ecosistemas. El objetivo del presente trabajo es analizar de forma temporal las transformaciones de los servicios ecosistémicos (SE) de las unidades agroecológicas (UAE) de la Cuenca del río Quequén Grande (CrQG). La metodología se basa en la estimación de indicadores de sustentabilidad: conservación de la calidad de suelos y agua (CCSA), conservación de la biodiversidad (CB) y conservación del ecosistema (CE). La metodología utilizada fue el cálculo de las ecuaciones de los indicadores por UAE (a partir de datos de trabajos antecedentes y observación actual directa a campo), y se calcularon coeficientes de correlación lineal (r) entre los indicadores. Los resultados muestran que el proceso de agriculturización afecta sobre todo a los servicios de regulación de la unidad de Sierras y Serranías, y que en todas las UAE los ecosistemas fueron adaptados en su mayor parte a la provisión de servicios de abastecimiento de importancia comercial. Los gráficos de dispersión permitieron verificar correspondencia en los valores. Se concluye que los SE se ven afectados de diferente manera al interior de la CrGQ siendo fundamental una gestión que permita un futuro ordenamiento territorial. The Pampean Region has strong comparative advantages for agricultural production. Current production models include annual double cultivation with increased use of agrochemicals and strong alteration of ecosystems with biodiversity fragmentation. The aim of this work is to temporarily analyze the transformations of the ecosystem services (SE) of the agroecological units (UAE) of the Quequén Grande River Basin (CrQG). The methodology is based on the estimation of sustainability indicators: soil and water quality conservation (CCSA), biodiversity conservation (CB) and ecosystem conservation (CE). For these, surface data obtained from classified images on the advancement of agricultural development by UAE of the Basin and field data obtained in interviews and background studies are necessary. The results show that the agricultural instensification process was manifested with different intensity in the different UAE of the Basin, the Sierras and Serranías unit was the most affected in both periods, with high values of environmental risk. The conclusions are that SE are affected differently in the CrQG and therefore it is intended to contribute to the territorial planning of SE in the basin.