Insect Marks on Bones from La Guillerma Archaeological Locality (Salado River Depression, Buenos Aires, Argentina)

The La Guillerma archaeological locality is located in the northeast sector of Buenos Aires province (Argentina). Two of its sites (LG1 and LG5), dated between ca. 1400- and 600-years BP, have a great amount of faunal remains including deer, rodents, fish and small birds that are subjected to taphonomic agents and processes (e.g., weathering, manganese, roots). Previous studies have shown osteophagic behaviour in different insects (e.g., Coleoptera, Blattodea). In this paper, we evaluate their incidence on La Guillerma faunal assemblage. We performed an analysis on marks that were identified in bone remains of various taxa and applied the criteria for identifying bone alteration by insects (i.e., by measuring each trace and comparing them with the types of insect marks described in the literature). Fifteen specimens (LG1 = 6 and LG5 = 9) exhibited different types of modifications (e.g., pits with striae in base, pits with emanating striae, striations) that are related to the action of insects. Although the proportion of affected bones is low in relation to the total sample, we highlight our study as the first detailed analysis of insect marks on archaeological bones from Argentina. We also emphasize the significance of addressing insect-produced modifications on Argentinean archaeological sites.

Morpho-anatomical features of the leaves and stems of Baccharis notosergila (Asteraceae) and their relationship with the environment and chemical control

Background and aims: Baccharis notosergila is an aggressive weed inhabiting the Salado river basin, Buenos Aires province, Argentina. The aims of this work were: to analyze the morpho-anatomy and histochemistry of aerial vegetative organs in order to understand the adaptation strategies that ensure its survival, as well as to expand knowledge on traits determining resistance to the control methods applied. M&M: The material collected was prepared and examined with conventional techniques of microscopy. Histochemical tests to identify starch, resins, polyphenols, and lipophilic substances were performed. Results: The major features found were small and deciduous leaves; uniseriate epidermis with massive and striate cuticle; stomata at level or slightly above the other epidermal cells and glandular trichomes secreting oily substances; stomata on both surfaces and isobilateral mesophyll. Tannins, starch and lipophilic substances were identified in leaves and stems; polyphenols, resins and lipids in ducts, and calcium oxalate crystals in leaves, stems and capitate trichomes. Conclusions: The aerial vegetative organs features of B. notosergila explain its tolerance to the unfavorable conditions of the Salado river basin area, as well as its high competitive ability over others species of the natural prairie. The reduced and deciduous leaves, the epidermal traits, and chemical substances found constitute a physical and chemical barrier reducing dehydration as well as the penetration of the herbicides applied for its control. Botanical knowledge of B. notosergila is the basis for the design and development of new and appropriate management methods for this species.

The Influence of Climate Change on River Corridors in Drylands: The Case of the Tehuacán-Cuicatlán Biosphere Reserve

The Tehuacán-Cuicatlán Biosphere Reserve, Mexico (TCBR) is the southernmost arid or semi-arid zone with the highest biodiversity in North America and is a UNESCO World Heritage site. Two main hydrographic streams cross the TCBR, the Salado River (an endogenous river) and the Grande River (an exogenous river). This study investigated temperature anomalies over the past 40 years. We analyzed potential differences between sub-basins and riparian areas on both streams using various indices, namely the Global Warming Index (GWI), Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI), and Normalized Difference Drought Index (NDDI), and analyzed the potential relationship of these indices with climate change. Time series of satellite-based precipitation (June 2000–December 2020) and air temperature (January 1980–December 2020) were analyzed. A set of Landsat 8 OLI TIRS imagery from the driest and wettest months (2013–2020) was used to estimate NDVI, NDWI, and NDDI. These indices were evaluated separately for the sub-basins and river corridors in the dry and rainy seasons. The precipitation records indicate that in the Grande river sub-basin, precipitation is higher than in the Salado river sub basin. Normalized temperature anomalies and the GWI suggest a warming trend from 1994 to 2020, increasing up to 0.86°C in the Salado River and 0.52°C in the Grande River. The Grande and Salado sub basins showed significant differences between dry and wet seasons for each index (NDVI, NDWI, and NDDI). A Discriminant Analysis showed that the Salado sub-basin and the Salado River corridor are associated with severe drying conditions in the dry season (highest NDDI values). In the wet season, the Grande River corridor showed intermediate values of NDVI and NDWI but low values of NDDI. The Grande River corridor in the dry season was characterized by intermediate values of NDVI, NDWI, and NDDI. These river corridors provide environmental services in a trade-off with the stream and should be considered biodiversity hotspots. Due to the accentuated warming trend and the lowest precipitation, the Salado River sub-basin showed desertification signs associated with climate change. Both the Salado and the Grande River corridors showed resilience strategies to face climatic conditions.

Biological Nitrogen Fixation, Carbon assimilation and plant performance of Lotus tenuis, contribute to define a strategic role in the lowlands in the Salado River Basin (Argentina)

Background and AimsForage production constitutes a great challenge for the Salado River Basin (Argentina), the major area devoted to livestock in the country. The successful naturalization of the European legume Lotus tenuis has been a productive and environmental relevance for the region. This study aims to evaluate its strategic contribution, reporting for the first time the B value for this species in these marginal environments for agriculture.MethodsThe 15N natural abundance method was used to evaluate the BNF of L. tenuis at soil plots and non-leguminous weed species in the same plots were utilized as reference plants. The assays included determinations of the 13C isotope, as well. Simultaneously, evaluations were carried out in the greenhouse for the determination of the B value of L. tenuis and the relative reproducibility of the field experiments.ResultsThe results obtained demonstrated that the L. tenuis promotion is accompanied by an increase in forage quality, due to the predominance of this C3 legume species, over C4 species. Moreover, its contribution to N inputs to the system, through the BNF with native rhizobia demonstrated to be about 80%, a highly relevant percentage for these constrained agroecosystems.ConclusionsThis work supports the hypothesis that L. tenuis promotion plays a strategic role in the sustainability of the ecosystem, especially in soil constrained areas. Joined with data previously published, the results obtained contribute to support the criteria that define the naturalized legume playing a strategic role in the sustainability of agriculture marginal soils.

Reconstructing the tectono-sedimentary evolution of the Early– Middle Jurassic Tlaxiaco Basin in southern Mexico: New insights into the crustal attenuation history of southern North America during Pangea breakup

During Pangea breakup, several Jurassic extensional to transtensional basins were developed all around the world. The boundaries of these basins are major structures that accommodated continental extension during Jurassic time. Therefore, reconstructing the geometry of Jurassic basins is a key factor in identifying the major faults that produced continental attenuation during Pangea breakup. We reconstruct the tectono-sedimentary evolution of the Jurassic Tlaxiaco Basin in southern Mexico using sedimentologic, petrographic, and U-Pb geochronologic data. We show that the northern boundary of the Tlaxiaco Basin was an area of high relief composed of the Paleozoic Acatlán Complex, which was drained to the south by a set of alluvial fans. The WNW-trending Salado River–Axutla fault is exposed directly to the north of the northernmost fan exposures, and it is interpreted as the Jurassic structure that controlled the tectono-sedimentary evolution of the Tlaxiaco Basin at its northern boundary. The eastern boundary is represented by a topographic high composed of the Proterozoic Oaxacan Complex, which was exhumed along the NNW-trending Caltepec fault and was drained to the west by a major meandering river called the Tlaxiaco River. Data presented in this work suggest that continental extension during Pangea breakup was accommodated in Mexico not only by NNW-trending faults associated with the development of the Tamaulipas–Chiapas transform and the opening of the Gulf of Mexico, but also by WNW-trending structures. Our work offers a new perspective for future studies that aim to reconstruct the breakup evolution of western equatorial Pangea.

Potential of arsenic bioremediation by a cyanobacterium isolated from the Salado River in the Atacama Desert

Cyanobacteria and microalgae are recognized as excellent metal(loid)s-bioremediators of aquatic systems. We isolated a cyanobacterium from the Salado River in the Atacama Desert, northern Chile, which was identified as Cyanobium sp. Growth inhibition bioassays were conducted with arsenic and cadmium, and tolerance of Cyanobium to these metals was estimated. Removal of arsenic was assessed under different pH conditions and over time. We showed that the Cyanobium strain isolated from the Salado River has a greater tolerance to the arsenic and cadmium compounds than other species commonly used in metal(loid)s-bioremediation. Removal of up to 90% of arsenic was obtained in alkaline conditions, within the first 3 hours of exposure suggesting that Cyanobium sp. isolated from the Atacama Desert could be further studied with biotechnological purposes and to understand the evolutionary mechanisms of adaption to arid environments.