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This paper presents the results of a study on the isotopic ecology of guanacos in central western Argentina. We examine the historical population ecology of guanacos using stable isotope analysis of bone collagen from pre-Hispanic and modern guanaco populations (n = 129), considering variability in two ecoregions: the Monte hot desert and the Andean-Patagonian cold desert. Our study addresses the consistency of guanaco diets over time, evaluating palaeoecology to provide information for conservation of this taxon. We found significant differences in isotopic niche size between modern and archaeological guanacos. When analyzed by ecoregion, there were significant differences in niche size through time, indicating that guanacos had distinctive dietary habits and occupied different ecological niches across the ecoregions. Comparing Standard Ellipse Areas (SEA) through time and across space, we observed that the archaeological SEA for guanacos is smaller than its modern counterpart in the Andean-Patagonia ecoregion. Conversely, in Monte, the archaeological SEA is larger than the one established for modern samples. The contrast between pre-Hispanic and modern populations highlight the impact of human activity and conservation efforts on the distribution and ecology of guanacos. These findings have important implications for understanding guanaco ecology with consequences for conservation policies. [ABSTRACT FROM AUTHOR]

Previous research on intensification in hunter gatherer strategies from Central West Argentina ca. 2000 years BP states that human demographic packing and overhunting of guanacos ( Lama guanicoe ) may have caused resource depression of this large prey animal. As a result, people broadened their diet to include smaller prey animals. Evidence supporting this conclusion includes an increase in Shannon's Diversity Index and a decrease in the abundance of artiodactyl remains over time in southern Mendoza. However, these studies about change in diet breadth did not consider the importance of spatial scale on analysis of prey choice and diet breadth and used the entire region as a unit of analysis. This is problematic because southern Mendoza has a heterogeneous landscape. In this paper we analyze different faunal abundance indices considering different spatial scales and the representativeness of the zooarchaeological samples. The results of the analyses show distinctive patterns of resource use over time at the macro- and subregional scales. Some of the difference can be explained by environmental differences between subregions and others might relate to differences in sample representativeness between subregions. [ABSTRACT FROM AUTHOR]

Zooarchaeologists have relied upon various approaches to study the impacts of harvest pressure and environmental change on ungulate populations, such as analysis of prey mortality patterns and morphometrics. Analysis of ancient DNA from ungulate bones and bone fragments from archaeological sites provides an additional means for studying prey population dynamics related to environmental change and human ecology over time. In this paper, we study the population history of the largest game animal in northwest Patagonia, the guanaco (Lama guanicoe). Our study relies on the use of Bayesian Skyline Plots to determine shifts in estimated guanaco population size based on analysis of ancient mitochondrial DNA. Our results indicate that hunting by humans in addition to increases in aridity during the late Holocene led to a decline in the guanaco population in the region, which is in contrast to the harvest and environmental history in other parts of Patagonia (south of our study area). Using a weight of evidence approach that includes proxies of environmental change, human population dynamics, exploitation of guanacos, and estimates of guanaco population size, we argue that the late Holocene shift in guanaco population size was a driving factor in subsistence and settlement change related to resource intensification during the late Holocene in northwest Patagonia. • Demographic reconstruction of guanaco population dynamics during the Holocene. •Estimated population size is based on ancient DNA analysis through Next Generation Sequencing. •There are key changes in guanaco population size during the late Holocene. •Late Holocene guanaco population relates to increased hunting pressure in northwest Patagonia. [ABSTRACT FROM AUTHOR]

The southern boundary of prehispanic farming in South America occurs in central Mendoza Province, Argentina at approximately 34 degrees south latitude. Archaeological evidence of farming includes the recovery of macrobotanical remains of cultigens and isotopic chemistry of human bone. Since the 1990s, archaeologists have also hypothesized that the llama (Lama glama), a domesticated South American camelid, was also herded near the southern boundary of prehispanic farming. The remains of a wild congeneric camelid, the guanaco (Lama guanicoe), however, are common in archaeological sites throughout Mendoza Province. It is difficult to distinguish bones of the domestic llama from wild guanaco in terms of osteological morphology, and therefore, claims that llama were in geographic areas where guanaco were also present based on osteometric analysis alone remain equivocal. A recent study, for example, claimed that twenty-five percent of the camelid remains from the high elevation Andes site of Laguna del Diamante S4 were identified based on osteometric evidence as domestic llama, but guanaco are also a likely candidate since the two species overlap in size. We test the hypothesis that domesticated camelids occurred in prehispanic, southern Mendoza through analysis of ancient DNA. We generated whole mitochondrial genome datasets from 41 samples from southern Mendoza late Holocene archaeological sites, located between 450 and 3400 meters above sea level (masl). All camelid samples from those sites were identified as guanaco; thus, we have no evidence to support the hypothesis that the domestic llama occurred in prehispanic southern Mendoza., Competing Interests: The authors have declared that no competing interests