Browsing by Author "Latorre, Claudio"

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    A Partially Complete Skeleton of Hippidion Saldiasi Roth, 1899 (Mammalia: Perissodactyla) from the Late Pleistocene of the High Andes in Northern Chile
    (2020) Labarca, Rafael; Caro, Francisco J.; Villavicencio, Natalia A.; Capriles, Jose M.; Briones, Esteban; Latorre, Claudio; Santoro, Calogero M.
    South America is well known for its abundance of Quaternary fossiliferous deposits, but well-preserved fossil remains from well-dated sites are scarce in the Atacama Desert and adjacent arid Andes. Here we report on a partially complete skeleton (46%) of a single young (ca. 3-4 years old) extinct horse discovered in the Salar de Surire, a salt flat located on the Andean altiplano of northern Chile (4,250 m asl). Comparative and osteometric morphological analyses identify the specimen as a South American endemic horse Hippidion saldiasi Roth, 1899. A direct AMS radiocarbon date on bone collagen yielded a calibrated age of 13,170 cal yr BP (2 sigma range: 13,300-13,060 cal yr BP) indicating that it lived near the end of the last glaciation. The body mass of the individual was calculated at approximately 326.4 kg, close to the upper limit of the larger sizes reported for the genus. Stable isotope evidence shows that the Salar de Surire horse relied on an almost 100% C3 diet that is mostly consistent with Hippidion specimens from other environments that also consumed either mixed C3/C4 or fully C3 diets. This finding is now the southernmost high-elevation record for this species and provides further evidence for the broad geographic and ecological distribution of this genus throughout southern South America.
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    ANOTHER TALE FROM THE HARSH WORLD: HOW PLANTS ADAPT TO EXTREME ENVIRONMENTS
    (2021) Dussarrat, Thomas; Decros, Guillaume; Diaz, Francisca P.; Gibon, Yves; Latorre, Claudio; Rolin, Dominique; Gutierrez, Rodrigo A.; Petriacq, Pierre
    The environmental fluctuations of a constantly evolving world can mould a changing context, often unfavourable to sessile organisms that must adjust their resource allocation between both resistance or tolerance mechanisms and growth. Plants bear the fascinating ability to survive and thrive under extreme conditions, a capacity that has always attracted the curiosity of humans, who have discovered and improved species capable of meeting our physiological needs. In this context, plant research has produced a great wealth of knowledge on the responses of plants to a range of abiotic stresses, mostly considering model species and/or controlled conditions. However, there is still minimal comprehension of plant adaptations and acclimations to extreme environments, which cries out for future investigations. In this article, we examined the main advances in understanding the adapted traits fixed through evolution that allowed for plant resistance against abiotic stress in extreme natural ecosystems. Spatio-temporal adaptations from extremophile plant species are described from morpho-anatomical features to physiological function and metabolic pathways adjustments. Considering that metabolism is at the heart of plant adaptations, a focus is given to the study of primary and secondary metabolic adjustments as well as redox metabolism under extreme conditions. This article further casts a critical glance at the main successes in studying extreme environments and examines some of the challenges and opportunities this research offers, especially considering the possible interaction with ecology and metaphenomics.
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    Big Fish or Small Fish? Differential Ichthyoarchaeological Representation Revealed by Different Recovery Methods in the Atacama Desert Coast, Northern Chile
    (2023) Rebolledo, Sandra; Bearez, Philippe; Zurro, Debora; Santoro, Calogero M.; Latorre, Claudio
    Recovery methods and techniques for archaeological sampling can yield major differences in abundance and anatomo-taxonomical representation of animals, affecting past social and ecological reconstruction. Despite being a common organic material in archaeological sites, faunal remains typically exhibit differential preservation of species and skeletal elements due to pre- and post-depositional processes. This is particularly true for small-sized animals such as certain species of fish, whose often small and fragile fragments are difficult to recover and identify. Here, we present the results of a comparative analysis between two ichthyoarchaeological assemblages from Caleta Vitor 3 in northern Chile (CV3, 18 degrees 45 ' 09 '' S), an Early to Middle Holocene (9.2-7.6 ka cal BP) Chinchorro shell midden site. We compare samples obtained and processed, both in the field and the lab, using different recovery techniques. We developed a data standardisation procedure to compare and evaluate skeletal representation, taxa distribution and variations throughout the stratigraphic sequence. Our results show that mesh screen size affects not only the abundance and density of fish but also species representation. Moreover, the identification of small pelagic fish at CV3 sheds further light upon prehistoric fishing strategies and social organisation during the site's early occupation.
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    Dietary diverstiy in the Atacama desert during the Late intermediate period of northern Chile
    (2019) Alfonso-Durruty, Marta P.; Gayo, Eugenia M.; Standen, Vivien; Castro, Victoria; Latorre, Claudio; Santoro, Calogero M.; Valenzuela, Daniela
    The Pacific Ocean that flanks the hyperarid Atacama Desert of Northern Chile is one of the richest biomass producers around the world. Thus, it is considered a key factor for the subsistence of prehistoric societies (including mixed-economy groups), that inhabited its coastal ecosystems as well as the neighboring inland areas. This study assesses the Arica Culture groups' diet (Late Intermediate Period; 1000-1530 CE), through stable isotope (on bone-collagen; delta C-13 and delta N-15) and dental pathology data. Seventy-seven (n = 77) individuals from two inland (LLU54 and AZ8) and one coastal (CAMS) archaeological sites were studied. Results show an important, but lower than predicted by earlier studies, contribution of marine resources in the diet of all three groups. Dental pathologies and stable isotopes indicate that these groups' diet varied in correlation with their distance to the Pacific Ocean as well as group and individual preferences. The results challenge the idea that Arica Culture groups depended heavily on marine resources for their subsistence. In contrast, this study shows both that the Arica Culture groups' diet was diverse, and that the terrestrial resources consumed were mostly contributed by C-3/CAM plants instead of maize. (C) 2019 Elsevier Ltd. All rights reserved.
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    Ecological and metabolic implications of the nurse effect of Maihueniopsis camachoi in the Atacama Desert
    (2024) Diaz, Francisca P.; Dussarrat, Thomas; Carrasco-Puga, Gabriela; Colombie, Sophie; Prigent, Sylvain; Decros, Guillaume; Bernillon, Stephane; Cassan, Cedric; Flandin, Amelie; Guerrero, Pablo C.; Gibon, Yves; Rolin, Dominique; Cavieres, Lohengrin A.; Petriacq, Pierre; Latorre, Claudio; Gutierrez, Rodrigo A.
    Plant-plant positive interactions are key drivers of community structure. Yet, the underlying molecular mechanisms of facilitation processes remain unexplored. We investigated the 'nursing' effect of Maihueniopsis camachoi, a cactus that thrives in the Atacama Desert between c. 2800 and 3800 m above sea level. We hypothesised that an important protective factor is thermal amelioration of less cold-tolerant species with a corresponding impact on molecular phenotypes.To test this hypothesis, we compared plant cover and temperatures within the cactus foliage with open areas and modelled the effect of temperatures on plant distribution. We combined eco-metabolomics and machine learning to test the molecular consequences of this association.Multiple species benefited from the interaction with M. camachoi. A conspicuous example was the extended distribution of Atriplex imbricata to colder elevations in association with M. camachoi (400 m higher as compared to plants in open areas). Metabolomics identified 93 biochemical markers predicting the interaction status of A. imbricata with 79% accuracy, independently of year.These findings place M. camachoi as a key species in Atacama plant communities, driving local biodiversity with an impact on molecular phenotypes of nursed species. Our results support the stress-gradient hypothesis and provide pioneer insights into the metabolic consequences of facilitation.
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    Ecological fidelity and spatiotemporal resolution of arthropod death assemblages from rodent middens in the central Atacama Desert (northern Chile)
    (2019) Dezerald, Olivier; Latorre, Claudio; Betancourt, Julio L.; Brito Vera, Gabriel A.; Gonzalez, Angelica L.
    Evaluating the magnitude and direction of biases affecting the ecological information captured by death assemblages is an important prerequisite for understanding past, present, and future community-environment relationships. Here, we establish the ecological fidelity andspatiotemporal resolution of an overlooked source of fossil remains: the soil arthropod assemblages found in rodent middens (that span from the present to >44,420 cal yr BP) collected in the central Atacama Desert of northern Chile. We evaluated the "live-dead agreement" across four sources of soil arthropod data; two contemporary surveys of live communities (i.e., live), and two sources of death assemblages (i.e., dead). Although live-dead agreements and diversity indices are highly variable among samples (live and dead assemblages), our results consistently demonstrate that an average fossil midden (i) better captures the structure and composition of living communities than species richness per se; (ii) offers a spatially-resolved picture of those communities at local scales; and (iii) is only weakly affected by time-averaging. The fine spatio-temporal resolution of fossil midden records in the Atacama, and most likely other areas of the world where rodent middens occur offers ecological information on the structure and composition of fossil arthropod assemblages potentially over many thousands of years. This information is reliable enough to establish historical baselines before past and ongoing anthropogenic impacts. (C) 2019 Elsevier Ltd. All rights reserved.
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    Establishment and formation of fog-dependent Tillandsia landbeckii dunes in the Atacama Desert: Evidence from radiocarbon and stable isotopes
    (2011) Latorre, Claudio; Gonzalez, Angelica L.; Quade, Jay; Farina, Jose M.; Pinto, Raquel; Marquet, Pablo A.
    Extensive dune fields made up exclusively of the bromeliad Tillandsia landbeckii thrive in the Atacama Desert, one of the most extreme landscapes on earth. These plants survive by adapting exclusively to take in abundant advective fog and dew as moisture sources. Although some information has been gathered regarding their modern distribution and adaptations, very little is known about how these dune systems actually form and accumulate over time. We present evidence based on 20 radiocarbon dates for the establishment age and development of five different such dune systems located along a similar to 215 km transect in northern Chile. Using stratigraphy, geochronology and stable C and N isotopes, we (1) develop an establishment chronology of these ecosystems, (2) explain how the unique T. landbeckii dunes form, and (3) link changes in foliar delta N-15 values to moisture availability in buried fossil T. landbeckii layers. We conclude by pointing out the potential that these systems have for reconstructing past climate change along coastal northern Chile during the late Holocene.
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    Evaluating the isotopic composition of leaf organic compounds in fog-dependent Tillandsia landbeckii across the coastal Atacama Desert: Implications for hydroclimate reconstructions at the dry limit
    (2024) Jaeschke, Andrea; Boehm, Christoph; Schween, Jan H.; Schefuss, Enno; Koch, Marcus A.; Latorre, Claudio; Contreras, Sergio; Rethemeyer, Janet; Wissel, Holger; Luecke, Andreas
    Fog is an important component of the coastal climate of northern Chile and southern Peru. Moisture and nutrients from fog maintain highly endemic vegetation (lomas) as well as unique Tillandsia landbeckii ecosystems that thrive at elevations of ca. 900-1200 m asl. Although this epiphytic CAM bromeliad is well adapted to the extreme climate, declining Tillandsia stocks observed over the past decades question the long-term survival with ongoing climate change. Here, we aim at better understanding the hydroclimatic signal encoded in the leaf organic compounds of Tillandsia landbeckii across the Atacama Desert's coastal mountain range (ca. 18-21 degrees S). First, we investigate spatiotemporal patterns of fog occurrence and related moisture sources available for the plants applying a new satellite -based fog -detection approach. We then use stable carbon, oxygen and hydrogen ( delta 13 C, delta 18 O, delta D) isotope analysis of leaf wax n -alkanes and cellulose to identify photosynthetic pathway as well as environmental and physiological processes that shape the isotopic composition in Tillandsia landbeckii . We find that leaf wax n -alkanes and cellulose reflect the balance of climatic and physiological drivers differently. While n - alkane delta D values more closely follow changes in precipitation delta D, evaporative enrichment seems to have a dominant influence on cellulose delta 18 O values. Cellulose delta D values are highly enriched compared to n -alkane delta D values, likely reflecting a predominant metabolic imprint on delta D. delta 13 C signatures in the organic compounds are valid proxies for CAM activity. Our results prove the general applicability of the isotopic biomarkers for reconstructing environmental change in the coastal Atacama Desert. This approach can be extended globally to west -coast deserts that share fog as a major source of moisture.
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    First record of cf. Aenocyon dirus (Leidy, 1858) (Carnivora, Canidae), from the Upper Pleistocene of the Atacama Desert, northern Chile
    (2022) Caro, Francisco J.; Labarca, Rafael; Prevosti, Francisco J.; Villavicencio, Natalia; Jarpa, Gabriela M.; Herrera, Katherine A.; Correa-Lau, Jacqueline; Latorre, Claudio; Santoro, Calogero M.
    Fossil records of canids are rare and incomplete in South America. In Chile, all well-identified taxa are part of the "South American Canid Clade" and come from sites located in southern Patagonia. Here, we report the first record for Chile of a taxon of the "Canis clade," assigned to cf. Aenocyon dirus. The fossil remains consist of a partially complete left hind limb, exposed by aeolian deflation, which facilitated its discovery at an isolated setting in Quebrada Mani, named QM38 site, in the southern sector of the Pampa del Tamarugal basin, part of the hyperarid core of the Atacama Desert, northern Chile. Measurements of the fossil are larger than the Protocyon troglodytes, falling in the smaller size range of A. dirus and within the larger range of Theriodictis platensis. Its morphological features compared with bone references of large extinct canids show that the fossil belongs to a small-sized Aenocyon. The remains occur in surface silty clays deposited by an alluvial fan that was active in the Pampa del Tamarugal basin in the Late Pleistocene. A radiocarbon date from bone apatite yielded an age of 14,660 cal years BP, placing it within the first half of the Central Andean Pluvial Event when this basin was wetter, well vegetated, and inhabited by large, medium, and small herbivores. No other large predator records are known from this basin, and our find affords a more complete view of this ecosystem which thrived in the hyperarid core of the Atacama during the Late Pleistocene.
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    FROM THE PACIFIC TO THE TROPICAL FORESTS: NETWORKS OF SOCIAL INTERACTION IN THE ATACAMA DESERT, LATE IN THE PLEISTOCENE
    (2019) Santoro, Calogero M.; Gayo, Eugenia M.; Capriles, Jose M.; Rivadeneira, Marcelo M.; Herrera, Katherine A.; Mandakovic, Valentina; Rallo, Monica; Rech, Jason A.; Cases, Barbara; Briones, Luis; Olguin, Laura; Valenzuela, Daniela; Borrero, Luis A.; Ugalde, Paula C.; Roihhanuner, Francisco; Latorre, Claudio; Szpak, Paul
    The social groups that initially inhabited the hyper arid core of the Atacama Desert of northern Chile during the late Pleistocene integrated a wide range of local, regional and supra regional goods and ideas for their social reproduction as suggested by the archaeological evidence contained in several open camps in Pampa del Tamarugal (PdT). Local resources for maintaining their every-day life, included stone raw material, wood, plant and animal fibers, game, and fresh water acquired within a radius of similar to 30 km (ca. 1-2 days journey). At a regional scale, some goods were introduced from the Pacific coast (60-80 km to the west, ca. 3-4 days journey), including elongated rounded cobbles used as hammer stones in lithic production, and shells, especially from non-edible species of mollusks. From the Andes (ranging 80-150 km to the east, ca. 5-8 days of journey), they obtained camelid fiber, obsidian and a high-quality chalcedony, in addition to sharing knowledge on projectile point designs (Patapatane and Tuina type forms). Pieces of wood of a tropical forest tree species (Ceiba spp.) from the east Andean lowlands (600 km away, ca. 30 days of journey) were also brought to the PdT. While local goods were procured by the circulation of people within the PdT, the small number of foreign items would have been acquired through some sort of exchange networks that integrated dispersed local communities throughout several ecosystems. These networks may have been a key factor behind the success exhibited by these early huntergatherers in the hyper arid ecosystems of the Atacama Desert at the end of the Pleistocene.
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    High- and low-latitude forcings drive Atacama Desert rainfall variations over the past 16,000 years
    (2021) Gonzalez-Pinilla, Francisco J.; Latorre, Claudio; Rojas, Maisa; Houston, John; Ignacia Rocuant, M.; Maldonado, Antonio; Santoro, Calogero M.; Quade, Jay; Betancourt, Julio L.
    Late Quaternary precipitation dynamics in the central Andes have been linked to both high- and low-latitude atmospheric teleconnections. We use present-day relationships between fecal pellet diameters from ashy chinchilla rats (Abrocoma cinerea) and mean annual rainfall to reconstruct the timing and magnitude of pluvials (wet episodes) spanning the past 16,000 years in the Atacama Desert based on 81 C-14-dated A. cinerea paleomiddens. A transient climate simulation shows that pluvials identified at 15.9 to 14.8, 13.0 to 8.6, and 8.1 to 7.6 ka B.P. can be linked to North Atlantic (high-latitude) forcing (e. g., Heinrich Stadial 1, Younger Dryas, and Bond cold events). Holocene pluvials at 5.0 to 4.6, 3.2 to 2.1, and 1.4 to 0.7 ka B.P. are not simulated, implying low-latitude internal variability forcing (i.e., ENSO regime shifts). These results help constrain future central Andean hydroclimatic variability and hold promise for reconstructing past climates from rodent middens in desert ecosystems worldwide.
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    Hydroclimate variations over the last 17,000 years as estimated by leaf waxes in rodent middens from the south-central Atacama Desert, Chile
    (2023) Frugone-Alvarez, Matias; Contreras, Sergio; Meseguer-Ruiz, Oliver; Tejos, Eduardo; Delgado-Huertas, Antonio; Valero-Garces, Blas; Diaz, Francisca P.; Briceno, Matias; Bustos-Morales, Manuel; Latorre, Claudio
    Leaf cuticular waxes are one of the most important environment-plant interaction structural systems that enable desert plants to withstand extreme climatic conditions. We present a long chain n-alkyl lipids study in fresh plant leaves and rodent palaeomiddens collected along an elevational gradient in the south-central Atacama Desert of Chile, covering six different vegetation belts: Steppe (4500-4000 m asl), Puna (4000-3300 m asl), pre-Puna (3300-2400 m asl), Absolute Desert (2400-1000 m asl) and Coastal Desert (1000-0 m asl). The 28 rodent palaeomiddens analyzed from Quebrada Incahuasi (25.6 & DEG;S, 3600 m asl) span the last 17,000 years. Modern-day distribution of long-chain n-alkanes and n-alkanoic acids varies among the dominant plant associations of the Atacama Desert. These plants show a species -specific chemotaxonomy linked to the climatic conditions. Furthermore, differences in average chain length (ACL) and carbon preference index (CPI) suggest that these plant communities are highly adapted to extreme environmental conditions. The sum of leaf wax n-alkanes was highest under wet conditions, while n-alkanoic acids (between n -C24 and n -C28) increased with hyperaridity. Similarly, analysis of n- alkane time series from palaeomiddens showed that the greatest changes in leaf wax n-alkane distri-butions (ACL and CPI) corresponded to the greatest increases in moisture during the Central Andean Pluvial Event (CAPE; between 18 and 9 ka cal BP) and the Late Holocene. The shift in the palaeomidden n- alkane distributions is corroborated by the relative abundance of rainfall-dependent extra-local taxa. This is the first study to report leaf wax content obtained from ancient rodent middens, and shows promising results as a robust hydroclimate proxy for the Atacama Desert region. & COPY; 2023 Published by Elsevier Ltd.
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    Landscape Engineering Impacts the Long-Term Stability of Agricultural Populations
    (2021) Freeman, Jacob; Anderies, John M.; Beckman, Noelle G.; Robinson, Erick; Baggio, Jacopo A.; Bird, Darcy; Nicholson, Christopher; Finley, Judson Byrd; Capriles, Jose M.; Gil, Adolfo F.; Byers, David; Gayo, Eugenia; Latorre, Claudio
    Explaining the stability of human populations provides knowledge for understanding the resilience of human societies to environmental change. Here, we use archaeological radiocarbon records to evaluate a hypothesis drawn from resilience thinking that may explain the stability of human populations: Faced with long-term increases in population density, greater variability in the production of food leads to less stable populations, while lower variability leads to more stable populations. However, increased population stability may come with the cost of larger collapses in response to rare, large-scale environmental perturbations. Our results partially support this hypothesis. Agricultural societies that relied on extensive landscape engineering to intensify production and tightly control variability in the production of food experienced the most stability. Contrary to the hypothesis, these societies also experienced the least severe population declines. We propose that the interrelationship between landscape engineering and increased political-economic complexity reduces the magnitude of population collapses in a region.
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    Late Quaternary hydrological and ecological changes in the hyperarid core of the northern Atacama Desert (∼21°S)
    (2012) Gayo, Eugenia M.; Latorre, Claudio; Jordan, Teresa E.; Nester, Peter L.; Estay, Sergio A.; Ojeda, Karla F.; Santoro, Calogero M.
    The hyperarid core of the Atacama Desert possesses important reserves of "fossil" or ancient groundwater, yet the extent and timing of past hydrologic change during the late Quaternary is largely unknown. In situ and/or short-distance transported leaf-litter deposits abound along relict fluvial terraces inserted within four dry and unvegetated valleys that drain into the endorheic basin of Pampa del Tamarugal (PDT, 21 degrees S, 900-1000 m), one of the largest and economically important aquifers in northern Chile. Our exceptional archive offers the opportunity to evaluate the response of low-elevation desert ecological and hydrological systems to late Quaternary climate variability. Three repeated expansions of riparian/wetland ecosystems, and perennial rivers occurred along the southernmost PDT basin between 17.6-14.2 ka, 12.1-11.4 ka and from 1.01-0.71 ka. Both early and late archaic archaeological artefact are present in clear association with our fossil riparian/wetland assemblages, which suggests that these palaeoenvironmental changes facilitated past human occupations in the hyperarid core of the Atacama Desert. Using modern analogues, we estimate that these ecological and hydrological changes were triggered by a threefold increase in rainfall along the headwaters of what are presently inactive canyons. Comparisons with other regional palaeoclimatic records from the central Andes indicate that these changes were synchronous with the widespread pluvial stages now termed the Central Andean Pluvial Event (CAPE- 17.5-14.2 ka and 13.8-9.7 ka). In addition, we summarize new evidence for perennial runoff, riparian ecosystems and a major human settlement during the latest Holocene. Our findings clearly show that local hydrological changes in the PDT were coupled with precipitation variability in the adjacent eastern highlands during the late Quaternary. The long-term dynamics of low-elevation desert ecological and hydrological systems are likely driven by changes in moisture sources, with one source tied to the Amazon region (N-NE mode) and the other to the Gran Chaco region (SE mode). We conclude by linking ENSO-like variability and moisture variations over the Gran Chaco to the three major regional-scale recharge events over the last 18 ka in the PDT basin. We conclude by asserting that an important portion of the groundwater resources in the PDT is indeed fossil, inherited from past pluvial events. We recommend that the relationship between ancient recharge, together with palaeoclimate records of past headwater rainfall fluctuations should be incorporated into future water-balance models and evaluation of groundwater potential in northern Chile. (C) 2012 Elsevier B.V. All rights reserved.
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    Leaf wax composition and distribution of Tillandsia landbeckii reflects moisture gradient across the hyperarid Atacama Desert
    (2022) Contreras, Sergio; Landahur, Manlio; Garcia, Karla; Latorre, Claudio; Reyers, Mark; Rethemeyer, Janet; Jaeschke, Andrea
    In the hyperarid Atacama Desert, water availability plays a crucial role in allowing plant survival. Along with scant rainfall, marine advective fog frequently occurs along the coastal escarpment fueling isolated mono-specific patches of Tillandsia vegetation. In this study, we investigate the lipid biomarker composition of the bromeliad Tillandsia landbeckii (CAM plant) to assess structural adaptations at the molecular level as a response to extremely arid conditions. We analyzed long-chain n-alkanes and fatty acids in living specimens (n = 59) collected from the main Tillandsia dune ecosystems across a 350 km coastal transect. We found that the leaf wax composition was dominated by n-alkanes with concentrations (total average 160.8 +/- 91.4 mu g/g) up to three times higher than fatty acids (66.7 +/- 40.7 mu g/g), likely as an adaptation to the hyperarid environment. Significant differences were found in leaf wax distribution (Average Chain Length [ACL] and Carbon Preference Index [CPI]) in the northern zone relative to the central and southern zones. We found strong negative correlations between fatty acid CPI and n-alkane ACL with precipitation and surface evaporation pointing at fine-scale adaptations to low moisture availability along the coastal transect. Moreover, our data indicate that the predominance of n-alkanes is reflecting the function of the wax in preventing water loss from the leaves. The hyperarid conditions and good preservation potential of both n-alkanes and fatty acids make them ideal tracers to study late Holocene climate change in the Atacama Desert.
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    Microbial hotspots in a relict fog-dependent Tillandsia landbeckii dune from the coastal Atacama Desert
    (2024) Jaeschke, Andrea; May, S. Matthias; Hakobyan, Anna; Morchen, Ramona; Bubenzer, Olaf; Bernasconi, Stefano M.; Schefu, Enno; Hoffmeister, Dirk; Latorre, Claudio; Gwozdz, Martina; Rethemeyer, Janet; Knief, Claudia
    The hyperarid Atacama Desert in northern Chile is considered to be one of the most hostile habitats for microbial life. Despite the extreme environmental conditions, isolated patches of vegetation exist in an otherwise barren landscape. Unique dune ecosystems dominated by rootless Tillandsia landbeckii vegetation occur at elevations of about 900-1200 m asl within the coastal mountain range and receive water and nutrients mostly from the Pacific Ocean via fog deposition. The largest dunes can form over thousands of years, and may host diverse and abundant populations of microorganisms, sustained by fog moisture and nutrients via plant litter deposition. Relict dune ecosystems, with no living plants, are also common on this landscape. We investigated the microbial community structure in such a relict and stratified Tillandsia dune, located north of the Rio Loa canyon, to explore links between plant occurrence and past hydroclimatic variations using a multi-proxy approach. Our results indicated multiple phases of dune growth with alternating plant colonization, dieback, and sand accumulation during the past similar to 1300 years. Hydrogen isotope analysis of fossil leaf wax n-alkanes showed a distinct pattern of more humid conditions during the Medieval Climate Anomaly and increasing aridity during the Little Ice Age. We found that microbial abundance and diversity were generally higher in and just beneath core sections with elevated amounts of plant material. Recurrent rewetting events during specific climatic periods in the past may have supported active microbial communities in the sand dune, sustained by plant resources. This is further supported by significant changes in foliar and sedimentary delta N-15 values. Most negative delta N-15 values concurred with higher n-alkane abundances and distinct shifts in microbial community structure, pointing to increased biological nitrogen cycling in the central part of the dune, where niche occupation occurred by nitrifying Thaumarchaeota. In contrast, the upper part of the dune core was characterized by low microbial diversity and abundance. The community was dominated by members of the Bacilli, which may have dispersed via dust during a generally more arid climate. The sand dune thus retains a unique and well-preserved environmental record that reflects concomitant changes in past hydrological (i.e., fog) conditions, plant growth and microbial abundance and diversity during late Holocene climate extremes.
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    Molecular systematics of chinchilla rats and taxonomic assessment of the Abrocoma cinerea species complex
    (2024) Gonzalez-Pinilla, Francisco J.; Latorre, Claudio; Palma, R. Eduardo
    Chinchilla rats (family Abrocomidae) are hystricomorph rodents primarily inhabiting the central Andes in South America with 8 species in the genus Abrocoma and 2 in Cuscomys. The systematics of this family-relying only on morphological differences-has faced several controversies, particularly in arid-adapted species of Abrocoma (the A. cinerea species complex, or ACC). By using partial DNA sequences of 1 mitochondrial (Cytochrome b) and 2 nuclear genes (GHR and RAG1), we: (i) inferred phylogenetic relationships between 5 species of Abrocoma and 1 of Cuscomys; (ii) performed molecular species-delimitation analyses in 4 species of the ACC (A. cinerea, A. famatina, A. schistacea, and A. uspallata); and (iii) estimated divergence times using stratigraphic ages of extinct taxa. Our phylogenetic analyses recovered 3 main clades: A. bennettii (basal); C. ashaninka; and the ACC. Striking differences in habitat use, morphology, and genetics suggest that each of these main clades might represent a distinct genus. In species-delimitation analyses in the ACC, only 2 species were recognized, and we thus suggest the synonymy of A. famatina with A. cinerea and of A. uspallata with A. schistacea. The origin of extant abrocomids was estimated at the late Miocene (similar to 5.6 million years ago, Ma) with the subsequent origin of arboreal species during the early Pliocene (similar to 4.3 Ma) and the ACC during the late Pliocene (similar to 3.3 Ma). We hypothesize that topographic uplift of the central Andes and associated climatic and ecological changes were the main drivers of diversification in this family.
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    New uses for ancient middens: bridging ecological and evolutionary perspectives
    (2024) Becklin, Katie M.; Betancourt, Julio L.; Braasch, Joseph; Dezerald, Olivier; Diaz, Francisca P.; Gonzalez, Angelica L.; Harbert, Robert; Holmgren, Camille A.; Hornsby, Angela D.; Latorre, Claudio; Matocq, Marjorie D.; Smith, Felisa A.
    Rodent middens provide a fine-scale spatiotemporal record of plant and animal communities over the late Quaternary. In the Americas, middens have offered insight into biotic responses to past environmental changes and historical factors influencing the distribution and diversity of species. However, few studies have used middens to investigate genetic or ecosystem level responses. Integrating midden studies with neoecology and experimental evolution can help address these gaps and test mechanisms underlying eco-evolutionary patterns across biological and spatiotemporal scales. Fully realizing the potential of middens to answer cross -cutting ecological and evolutionary questions and inform conservation goals in the Anthropocene will require a collaborative research community to exploit existing midden archives and mount new campaigns to leverage midden records globally.
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    Plant ecological genomics at the limits of life in the Atacama Desert
    (2021) Eshel, Gil; Araus, Viviana; Undurraga, Soledad; Soto, Daniela C.; Moraga, Carol; Montecinos, Alejandro; Moyano, Tomas; Maldonado, Jonathan; Diaz, Francisca P.; Varala, Kranthi; Nelson, Chase W.; Contreras-Lopez, Orlando; Pal-Gabor, Henrietta; Kraiser, Tatiana; Carrasco-Puga, Gabriela; Nilo-Poyanco, Ricardo; Zegar, Charles M.; Orellana, Ariel; Montecino, Martin; Maass, Alejandro; Allende, Miguel L.; DeSalle, Robert; Stevenson, Dennis W.; Gonzalez, Mauricio; Latorre, Claudio; Coruzzi, Gloria M.; Gutierrez, Rodrigo A.
    The Atacama Desert in Chile-hyperarid and with high-ultraviolet irradiance levels-is one of the harshest environments on Earth. Yet, dozens of species grow there, including Atacama-endemic plants. Herein, we establish the Talabre-Leji = a transect (TLT) in the Atacama as an unparalleled natural laboratory to study plant adaptation to extreme environmental conditions. We characterized climate, soil, plant, and soil-microbe diversity at 22 sites (every 100 m of altitude) along the TLT over a 10-y period. We quantified drought, nutrient deficiencies, large diurnal temperature oscillations, and pH gradients that define three distinct vegetational belts along the altitudinal cline. We deep-sequenced transcriptomes of 32 dominant plant species spanning the major plant clades, and assessed soil microbes by metabarcoding sequencing. The top-expressed genes in the 32 Atacama species are enriched in stress responses, metabolism, and energy production. Moreover, their root-associated soils are enriched in growthpromoting bacteria, including nitrogen fixers. To identify genes associated with plant adaptation to harsh environments, we compared 32 Atacama species with the 32 closest sequenced species, comprising 70 taxa and 1,686,950 proteins. To perform phylogenomic reconstruction, we concatenated 15,972 ortholog groups into a supermatrix of 8,599,764 amino acids. Using two codonbased methods, we identified 265 candidate positively selected genes (PSGs) in the Atacama plants, 64% of which are located in Pfam domains, supporting their functional relevance. For 59/184 PSGs with an Arabidopsis ortholog, we uncovered functional evidence linking them to plant resilience. As some Atacama plants are closely related to staple crops, these candidate PSGs are a "genetic goldmine" to engineer crop resilience to face climate change.
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    Population dynamics and cultural niche construction during the Late Holocene in a mediterranean ecosystem (central Chile, 32°S-36°S)
    (2024) Godoy-Aguirre, Carolina; Frugone-Alvarez, Matias; Gayo, Eugenia M.; Campbell, Roberto; Lima, Mauricio; Maldonado, Antonio; Latorre, Claudio
    Understanding socio-ecological systems over the long term can shed light on past adaptive strategies in environmentally sensitive regions. Central Chile is an emblematic case study for mediterranean ecosystems, where a progressive and sustained population increase began approximately 2000 years ago alongside significant landscape changes. In this work we analyzed regional paleo-demographic trends by compiling a new database of archaeological dates over the last 3000 years, and integrating population dynamics theory with an analysis of the spatio-temporal variation of regional cultural stages. Results show three moments of marked acceleration in population growth: just before agricultural adoption, during the Archaic Period (c. 700-300 BCE); during the second half of the ECP (500-900 CE); and during the Late Intermediate Period (1200-1400 CE). We also identified periods of deceleration in per capita growth rates, although population size continued to increase (300 BCE-500 CE, 900-1200 CE and after 1400 CE). These large shifts in the per capita growth rates coincide with major cultural changes associated with social and economic aspects. The pulses of major occupation show in general terms a more intensive use of the valleys as the population size increased, although the remaining ecosystems never ceased to be occupied with different economic and symbolic emphases.