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Insect faunas from the latest Cretaceous are poorly known worldwide. Particularly, in the Southern Hemisphere, there is a gap regarding insect assemblages in the Campanian-Maastrichtian interval. Here we present an insect assemblage from the Maastrichtian Chorrillo Formation, southern Argentina, represented by well-preserved and non-deformed, chitinous microscopic remains including head capsules, wings and scales. Identified clades include Chironomidae dipterans, Coelolepida lepidopterans, and Ephemeroptera. The assemblage taxonomically resembles those of Cenozoic age, rather than other Mesozoic assemblages, in being composed by diverse chironomids and lepidopterans. To the best of our knowledge, present discovery constitutes the first insect body fossils for the Maastrichtian in the Southern Hemisphere, thus filling the gap between well-known Early Cretaceous entomofaunas and those of Paleogene age. The presented evidence shows that modern clades of chironomids were already dominant and diversified by the end of the Cretaceous, in concert with the parallel radiation of aquatic angiosperms which became dominant in freshwater habitats. This exceptional finding encourages the active search of microscopic remains of fossil arthropods in other geological units, which could provide a unique way of enhancing our knowledge on the past diversity of the clade. An insect assemblage gathered from the Chorrillo Formation in Argentina constitutes an important set of insect body fossils for the Maastrichtian interval in the Southern Hemisphere. [ABSTRACT FROM AUTHOR]

Understanding how animals respond to large-scale environmental changes is difficult to achieve because monitoring data are rarely available for more than the past few decades, if at all. Here, we demonstrate how a variety of palaeoecological proxies (e.g. isotopes, geochemistry and DNA) from an Andean Condor (Vultur gryphus) guano deposit from Argentina can be used to explore breeding site fidelity and the impacts of environmental changes on avian behaviour. We found that condors used the nesting site since at least approximately 2200 years ago, with an approximately 1000-year nesting frequency slowdown from ca 1650 to 650 years before the present (yr BP). We provide evidence that the nesting slowdown coincided with a period of increased volcanic activity in the nearby Southern Volcanic Zone, which resulted in decreased availability of carrion and deterred scavenging birds. After returning to the nest site ca 650 yr BP, condor diet shifted from the carrion of native species and beached marine animals to the carrion of livestock (e.g. sheep and cattle) and exotic herbivores (e.g. red deer and European hare) introduced by European settlers. Currently, Andean Condors have elevated lead concentrations in their guano compared to the past, which is associated with human persecution linked to the shift in diet. [ABSTRACT FROM AUTHOR]

Lake Morenito located in the Argentinean Patagonia has been exposed to climatic, volcanic, and anthropogenic impacts for the last decades. In particular, the damming of the lake and the eruption of the Calbuco/Puyehue Volcanoes in AD 1960 played an important role in the lake's history. A 80-cm-long sediment core from Lake Morenito spanning more than 100 years was studied for chironomids, stable isotopes, and organic geochemistry to investigate how natural and anthropogenic stressors impacted the lake. Chironomid assemblages display large changes around AD 1950, with the appearance of the warm-adapted Chironomus and the replacement of Apsectrotanypus by Ablabesmyia, indicating a shift to warmer conditions. By that time and up to the present, an increasing trend of δ15N coupled with a decrease of δ13C points to shifts in the carbon and nitrogen cycles associated with human activities. It is evident that the onset of human activities during the 1950s following by the lake damming in AD 1960 had significant effects on the chironomid assemblages and the geochemical composition of sediments which is reflected in the progressive deterioration of the lake ecosystem. [ABSTRACT FROM AUTHOR]

Paleoecological studies are crucial for understanding ecosystem disturbance and resilience dynamics. However, nearly all the research related to the response of aquatic communities to disturbances has been developed at short-term ecological scales. In this study, we investigate the long-term response of chironomid insects of two lakes, to volcanic and other environmental disturbances that have taken place during the last 200 years. The studied lakes, Lake Verde and Lake Toncek, are located in the Nahuel Huapi National Park (northern Patagonia, Argentina), under contrasting environmental settings. Our results show that the main driver of faunal changes in both lakes is volcanism. Indeed, after the impact of the 1960 Puyehue/Calbuco volcanic events, the chironomid assemblage of Lake Verde recovered to initial conditions showing high resistance and a strong resilience to the impact. In this lake, the canopy, the presence of macrophytes, and the dynamic of the watershed are important determinants of resilience providing habitats for species colonization and/or by giving refugia to the community. Contrarily, chironomid assemblages from Lake Toncek did not recover to the original state after the impact of the ash. This lake is located above the tree line, and therefore it is highly probable that the lack of vegetation cover in the basin offered no protection for the aquatic environment, leaving the ecosystem highly exposed to the effect of the volcanic ashes. Subordinate to the effects of the volcanism, rising temperatures in the last 50 years and/or increasing human activities in the area, especially in L. Toncek, may also be responsible for the changes in chironomid assemblages. [ABSTRACT FROM AUTHOR]

Abstract: In the Southern Hemisphere, the lack of quantitative temperature records hampers the understanding of climate change since the Last Glaciation and refrains the comparison with the Northern Hemisphere records. To provide quantitative data, a 63-lake chironomid transfer functions was developed in Patagonia. Mean annual air temperature (MAT) was one of the most important factors explaining the distribution of chironomids while precipitation did not have any significant relationship with chironomid assemblages. The MAT model had a r 2 of 0.64, a RMSE of 0.83 and a maximum bias of 1.81°C, comparable to other transfer functions of this size. This model was applied to the Lake Potrok Aike (PTA) chironomid records which consisted of only four taxa (Phaenopsectra, Cricotopus, Smittia and Polypedilum). The chironomid-inferred air temperatures were colder-than-the-average (10.8°C) during the Lateglacial with the coldest temperatures (9°C in average) during the Antarctic Cold Reversal (ACR). Between ca. 8000 and 3500cal. years BP, the chironomid-inferred air temperatures were warmer-than-the-average with a decreasing trend. From ca. 3500cal. years BP to the present, the chironomid-inferred temperatures oscillated around the average. The difference between the chironomid-inferred air temperature in the surface sample and the climate normal (1961–1990) was 0.6°C, suggesting that chironomids are sensitive enough to quantitatively reconstruct MAT at PTA. The general pattern of temperature changes reconstructed by the PTA chironomid record corresponded well to other quantitative records in the Southern Hemisphere. The results presented here show that investing in the development of chironomid transfer functions for quantitative climate research in the Southern Hemisphere is valuable. [Copyright &y& Elsevier]