Humid and cold forest connections in South America between the eastern Andes and the southern Atlantic coast during the LGM.

The presence of Andean plant genera in moist forests of the Brazilian Atlantic Coast has been historically hypothesized as the result of cross-continental migrations starting at the eastern Andean flanks. Here we test hypotheses of former connections between the Atlantic and Andean forests by examining distribution patterns of selected cool and moist-adapted plant arboreal taxa present in 54 South American pollen records of the Last Glacial Maximum (LGM), ca. 19-23 cal ka, known to occur in both plant domains. Pollen taxa studied include Araucaria, Drimys, Hedyosmum, Ilex, Myrsine, Podocarpus, Symplocos, Weinmannia, Myrtaceae, Ericaceae and Arecaceae. Past connectivity patterns between these two neotropical regions as well as individual ecological niches during the LGM were explored by cluster analysis of fossil assemblages and modern plant distributions. Additionally, we examined the ecological niche of 137 plant species with shared distributions between the Andes and coastal Brazil. Our results revealed five complex connectivity patterns for South American vegetation linking Andean, Amazonian and Atlantic Forests and one disjunction distribution in southern Chile. This study also provides a better understanding of vegetation cover on the large and shallow South American continental shelf that was exposed due to a global sea level drop.

Historical Hg accumulation (∼65 cal kyr BP) in upland lakes of the Southeastern Brazilian Amazonia: New evidence of the extent of geogenic and diagenetic control.

The historical upland lake sediments in the Brazilian Amazon witnessed significant enrichment of total mercury (Hg). However, its spatio-temporal relationships between lakes and the main factors responsible for this enrichment are still poorly constrained. Given this, we geochemically investigated 12 radiometrically dated (extending back to ∼65 cal kyr BP) sediment cores from the Carajás plateau, Brazil. The Hg level in historical sediments presented a large temporal variability (from 1 to 3200 µg/kg), with maximum accumulation peaks observed between 30 and 45 cal kyr BP in core R2, LB3, and R1. However, the lack of the Hg peak in other cores (LV2 and LTI3) during the same period despite being proximity and non-correlation of these Hg peaks with the onset of major volcanic events indicates that this source has little bearing. Hg enrichment is highly dependent on the type of sedimentary facies, with higher values were associated with detritic facies (MI) and detritic+organic facies (P/M). Principal component analysis shows that aluminosilicate minerals and organic matter are essential hosts of Hg in sediments. The positive correlation between Al, Ti, and Hg in detritic facies and their strong coherence with Hg/TOC in R1, R5, LSL, ST02, and LB3 cores indicate that Hg is primarily of lithogenic origin. This can be substantiated by the higher background threshold value of Hg (574 µg/kg) in historical lake sediments compared to those in recent lake sediments (340 µg/kg). However, the most pronounced Hg peak (3200 µg/kg) in R2 around 45 cal kyr BP, which correlates positively with TOC, S, Se, As, and Mo indicates their diagenetic enrichment in organic-rich sediments under anoxic conditions. Thus, in addition to the lithogenic effect, it can be argued that diagenesis can play a significant role in prompting Hg enrichment in the Carajás lake sediments in Amazonia.

A comprehensive procedure for pollen extraction from bat guano deposits in organic and detrital matrices.

Although bat guano deposits have been proven to be excellent environmental archives for paleoecological and paleoclimate studies, the development of a standardized method specially catering to pollen extraction has received no attention so far. In general, the processing procedure is quite similar among published studies, but adjustments must be made regarding the proportion of organic and particulate matter in the guano deposit. In this study, we present step-by-step optimized sample processing methods for pollen analysis. These procedures first apply a chemical treatment for the removal of siliceous and organic material, followed by a sieving step to remove the remaining inorganic matter from those samples with high detrital content. Overall, our methods can efficiently remove particulate matter and improve the quality of the final residue, resulting in cleaner slides and better visualization of pollen and spores.•Remove humic acid and organic material with Potassium hydroxide.•Remove inorganic matter with hydrofluoric acid and sieving.•Concentrate and store the pollen residues in glycerin.

Is the 'canine surrogacy approach' (CSA) still valid for dogs and humans in market-oriented and subsistence-oriented communities in Brazil?

Based on the assumptions that human food is available for dogs and isotope diet-tissue differences are similar in dogs and humans, the 'canine surrogacy approach' (CSA) has been used to infer patterns of ancient populations. The goal of this study was to test the CSA in urban (Brasília and Piracicaba) and in rural (Ubatuba and Maraã) areas. The hair C and N isotope ratios of modern dogs were compared with those of human fingernails from different regions of Brazil. Our CSA results showed a correlation between dog and human isotopes values: in rural areas δ15N of humans and dogs was not statistically different; contrarily, in urban centres, δ15N of humans was approximately 1 ‰ higher (p < 0.01) than δ15N of dogs; humans had lower δ13C values (p < 0.01) than dogs in Brasília, Piracicaba and Ubatuba. In Maraã, there was not any significant difference between dogs and humans. We concluded that CSA is still valid as a first approach in modern societies. However, isotopic differences found suggest that in modern societies processed dog food is increasingly disconnecting human and dog, jeopardising the use of CSA in the future if the trend of increasing processed dog food consumption continues to occur.

Carbon and nitrogen isotopic composition of commercial dog food in Brazil.

BACKGROUND: Brazil is a low- to medium-income country and has the second largest pet food market in the world with 8% of world pet food consumption. The lowest-income social class spends around 17% of their domestic budget on pet food and other items related to pets. Consumers are frequently misled by advertising as there is no precise information about the main sources of protein, carbohydrates and fat in the labels, and the Brazilian pet food industry can legally claim that their products contain certain items like salmon or beef even if they use just a flavoring compound. METHODS: The stable isotope methodology compares the stable isotope ratios of carbon (13C/12C) and nitrogen (15N/14N) between source and product. The 13C/12C ratio of a specific product (e.g., dog food) reveals the proportions of C4 (maize) and C3 (soybean, rice and wheat) plants in that product and the 15N/14N ratio reveals the proportion of the compounds derived from animals. With this isotopic data, we used MixSIAR, a Bayesian stable isotope-mixing model, to estimate the proportion of maize, grains, poultry and beef in dog food. RESULTS: The δ13C values of dry dog food ranged from -24.2‰ to -12.8‰, with an average (± standard-deviation) of -17.1‰ ± 2.8‰. The δ13C values of wet pet food ranged from -25.4‰ to -16.9‰, with an average (± standard-deviation) of -21.2‰ ± 2.4‰, which was significantly lower (p < 0.01). The δ15N values of the dry and wet food ranged from 1.7‰ to 4.2‰, and from 0.5‰ to 5.5‰, respectively. The average δ15N values of dry food (2.9‰ ± 0.5‰) was not higher than the wet food (2.6‰ ± 1.3‰) (p > 0.01). The output of the MixSIAR showed a low proportion of bovine products in dry dog food samples. On the other hand, poultry was obviously the dominant ingredient present in most of the samples. Maize was the second dominant ingredient. Wet and dry dog food showed similar isotopic analysis results. The only difference was a lower proportion of maize and higher proportion of grains in wet dog food. DISCUSSION: The main finding is that dog food in Brazil is mostly made of approximately 60% (ranging from 32% to 86%) animal-based and 40% (ranging from 14% to 67%) plant-based products. Poultry and maize are the main ingredients. Poultry is added as a by-product or meal, which avoids competition between dogs and humans for meat products, while they can compete for maize. On the other hand, a large proportion of plant-based products in dog food decreases the energy and environmental footprint, since plant-based food products tend to be less harmful compared to animal-based products. Labels can mislead consumers by showing pictures of items that are not necessarily part of the product composition and by not showing the detailed information on the proportion of each ingredient. This information would allow customers to make their own choices considering their pet's nutrition, the competition between animals and humans for resources and environmental sustainability.