Northwestern Patagonia Research Articles

Projectile point variability from a biogeographical approach in northwestern Patagonia, Argentina

Our objective is to analyse the relationship among the availability, selection, and use of raw materials suitable for knapping with projectile points from the Late Holocene of northwestern Patagonia. We analyse differences in the raw material used to make projectile points according to the techno-morphological characteristics. Non-stemmed projectile points predominate in all the biogeographic units. The size and weight of the projectile points in Patagonia duplicate those from Altoandina and Monte. We conclude that there was a coexistence of two weapons systems related to hunting, the bow and arrow, together with the use of darts.

Devonian to Early Carboniferous Retreating—Advancing Subduction Switch in the Northwestern Patagonia Accretionary Orogen: U‐Pb and Lu‐Hf Isotopic Insights

AbstractIn this contribution, we present new early middle Devonian igneous and metaigneous units with a major juvenile magmatic source input in the North Patagonian Massif, which were discovered through U‐Pb and Lu‐Hf zircon analyses. Afterward, we assessed their tectonic implications for northwestern Patagonia and then for southern South America, combining our results with available database information consisting of igneous crystallization ages and isotopic data of the Devonian to early Carboniferous magmatic units, tectonic‐metamorphic analyses, and thermochronologic record. This study allows for distinguishing retreating and advancing subduction switching in northwestern Patagonia (38°30′ to 44°S) and a contrasting coetaneous evolution for basement outcrops exposed further north (27°30′ and 37°30′S). The early middle Devonian (400–380 Ma) northwestern Patagonian magmatism is characterized by widespread magmatism and positive εHf–εNd linked to forearc and backarc magmatism that evolved within a retreating subduction stage. A tectonic switching toward advancing orogeny stage began in the late Devonian, evidenced by a lull in magmatic activity with a negative εHf–εNd trend, possibly contemporaneous with the first tectonic‐metamorphic event in western Patagonia. An early Carboniferous magmatic gap, followed by the subsequent development of the main foliation in the basement during the Carboniferous‐Permian period, denotes the acme of this contractional stage. In contrast, the Devonian period in the northern segment is characterized by mostly negative εHf–εNd values, reverse shear zone activity in the foreland, and an inboard magmatism migration, evidencing a compressive tectonic setting that changed to an extensional configuration in the early Carboniferous with widespread arc magmatism development.

Enrichment-planting with pines alters fuel amount and structure in endangered Araucaria araucana forests in northwestern Patagonia, Argentina

The introduction of non-native tree species for large-scale afforestation may alter the fire regime of native ecosystems by modifying fuel proprieties. We quantified changes in fuel abundance and structure resulting from the establishment of commercial Pinus spp. plantations in Araucaria araucana ecosystems in northwestern Patagonia, Argentina. Specifically, we assessed the amount, distribution, and condition (live/dead) of surface and standing fine fuel in A. araucana stands with mature pine plantations (i.e. > 20 cm dbh) and in stands dominated only by A. araucana (control). Our study shows that both types of stands are prone to wildfires, but pine plantations have fuel characteristics that imply greater flammability due to higher fuel load and vertical continuity in the understory and in the overstory canopy. In the absence of fuel mitigation practices, A. araucana stands with plantations exhibit greater flammability than the control A. araucana stands, potentially promoting the occurrence and spread of fires of greater severity. This study contributes to understanding the effects of enrichment planting of pines, and possibly pine invasions, on A. araucaria ecosystem flammability and their potential consequences on fire behavior.

Resident Hymenopteran Parasitoids with Potential Drosophilid Associations in Andean North Patagonia: Implications for the Biological Control of the Spotted Wing Drosophila.

The spotted wing drosophila, Drosophila suzukii Matsumura, is native to Southeast Asia and has become a serious pest of soft-skinned fruits worldwide. Several control methods are being tested worldwide as part of an integrated pest management approach. Biological control is a promising alternative tactic that can be used to manage D. suzukii populations, especially in unmanaged areas. This study aimed at exploring the diversity of resident hymenopteran parasitoids of drosophilids in northwestern Patagonia, where D. suzukii is considered an important pest. The survey also aimed to investigate possible associations between parasitoids and D. suzukii in several crops and non-crop fruits, and to determine D. suzukii fruits infestation levels. Fourteen sites with mainly berry crops were sampled biweekly using cider vinegar traps and collecting fresh fruits from a variety of crop and non-crop fruit plants. We identified five species of hymenopteran parasitoids, obtained from the baited traps, that have the potential to associate with D. suzukii: Leptopilina heterotoma Thomson, Ganaspis brasiliensis Ihering, Hexacola hexatoma Hartig (Figitidae), Pachycrepoideus vindemmiae Rondani (Pteromalidae), and Spalangia endius Walker (Spalangiidae). Leptopilina heterotoma is reported for the first time in Argentina. High numbers of D. suzukii adults were recovered from baited traps and field-collected fruits. However, no parasitoid emerged from D. suzukii pupae recovered from fruits, nor were any dead parasitoids recorded inside D. suzukii pupae. Overall infestation levels of D. suzukii on field-collected fruits did not differ significantly between species/varieties. The results are discussed with emphasis on the possible functionality and perspectives of using these species as biological control agents.

Freshwater diatom evidence for Southern Westerly Wind evolution since ∼18 ka in northwestern Patagonia

We report a fossil diatom record from small closed-basin Lago Lepué (43°S) to examine past changes in freshwater ecosystems and hydrologic balance in northwestern Patagonia since ∼18 ka. The record starts with abundant staurosiroids and the heavily silicified Aulacoseira granulata suggesting deep turbulent mixing during a low lake level stand between ∼18- 16.4 ka. A. distans increased shortly after ∼16.4 ka and achieved maximum abundance between ∼15.4-13.6 ka, while A. granulata disappeared at ∼15.8 ka and A. alpigena rose at ∼14.9 ka to its maximum between ∼13-12 ka. We infer turbulent, cold, and circumneutral to slightly acid lake conditions contemporaneous with a steady lake level rise that started at ∼16.4 ka and culminated between ∼13-12 ka. These trends reversed between ∼11-7.8 ka with the dominance of Discostella stelligera and staurosiroids, suggesting warmer lake conditions and shallower mixing. Subsequent changes include increases of A. distans with D. stelligera between ∼7.8-5.8 ka, dominance of the former between ∼5.8-3.3 ka, a rapid increase in A. perglabra at ∼3.3 ka, and ensuing diversification of benthic acidophilous species. We infer a rapid lake-level decline between ∼11-7.8 ka, with subsequent rising pulses at ∼7.8 ka and ∼5.8 ka, a multimillennial-scale lake acidification trend, and overall high lake levels with centennial-scale reversals between ∼6-0 ka. Coherent variations in terrestrial and aquatic ecosystem changes recorded in the same core suggest negative hydrologic balance between ∼18-16.4 ka and ∼11–7.8 ka, positive balance between ∼14.9-12 ka and ∼6–0 ka, with transitional conditions in the interim, overprinted by millennial-scale changes and enhanced variability since ∼6 ka. Covariation with paleoclimate records at regional, pan-Patagonian, and hemispheric scale suggests millennial to centennial-scale variability superimposed upon a multi-millennial pacing of Southern Westerly Wind evolution since ∼18 ka.

The Cuesta de Rahue Basement Inlier (Southern Neuquén Precordillera, Argentina): a Devonian to Triassic polyphase orogenic record in northern Patagonia

We present new geological, structural and microstructural data, together with K–Ar biotite and illite geochronological data, for the igneous–metamorphic rocks exposed in the Cuesta de Rahue Basement Inlier in the Southern Neuquén Precordillera, Argentina. We use these data to reconstruct the Late Paleozoic to Mesozoic tectonometamorphic and magmatic history of northwestern Patagonia. This block consists of a medium-grade metasedimentary sequence (the Cuesta de Rahue Metamorphic Complex), Late Carboniferous granitoids and a low-grade metavolcano-sedimentary unit (the Arroyo Coloco Metamorphic Complex). The Cuesta de Rahue Metamorphic Complex was deposited during the mid-Paleozoic and underwent Devonian low-pressure regional metamorphism, followed by the intrusion of granitoids at c. 300 Ma. By contrast, the Arroyo Coloco Metamorphic Complex records deformation and metamorphism under epizonal conditions (>300°C), constrained at c. 232–199 Ma by K–Ar and X-ray diffraction illite data. The Cuesta de Rahue Basement Inlier thus records a protracted orogenic evolution, recording Devonian metamorphism, Late Carboniferous–Permian Gondwanide tectonomagmatic processes, and Late Triassic deformation and metamorphism. This block was later affected by Mesozoic normal faulting and Miocene–Pliocene Andean deformation. The Andean deformation was intimately related to the reactivation of inherited basement fabrics, favouring a transpressional deformation regime. Supplementary material: Supplementary Material 1 – Analytical procedures is available at https://doi.org/10.6084/m9.figshare.c.6484467

Phidon abismus sp. nov. from Patagonian forests of Argentina (Blattaria: Pseudophyllodromiidae).

Phidon abismus sp. nov. is described from north-western Patagonian forests in Argentina. The specimens were collected under dead tree bark of Austrocedrus chilensis, Nothofagus dombeyi and Nothofagus pumilio. A detailed description of the male including abdominal apex, genitalia, tegmen and wing venation and front femur armament type B2 is provided as well as a description of the A type oviparity. The genus Phidon is recorded from Argentina for the first time. The key of Rehn (1933) for the known males of the genus is updated.

Synoptic-to-intraseasonal atmospheric modulation of phytoplankton biomass in the inner sea of Chiloé, Northwest Patagonia (42.5°-43.5°S, 72.5°-74°W), Chile

The Inner Sea of Chiloé (ISC) in northwestern Patagonia has experienced large harmful algal blooms in the past decade, impacting human health and affecting the large aquaculture industry of the region. Thus, the investigation of factors favouring regional phytoplankton growth are of particular interest. Analysing the synoptic-to-intraseasonal variability, we explore changes in phytoplankton biomass in southern ISC (S-ISC, 42.5°-43.5°S, 72.5°-74°W) and their concurrent mesoscale and large-scale meteorological and oceanographic conditions. We use high-resolution satellite normalized fluorescence line height (nFLH) and chlorophyll-a (CHL-A) from the MODIS-Aqua sensor as proxies for phytoplankton biomass, besides oceanic and atmospheric variables derived from various remote-sensing sources and atmospheric fields from the ERA5 reanalysis. Specifically, we focus on high phytoplankton biomass events HBEs, which are defined as those cases when intraseasonal nFLH anomaly (nFLH’) exceeds the 95th percentile threshold. Each event was characterised by its first date of occurrence (called day 0). We detected 16 HBE between 2003 and 2019 in S-ISC. HBEs tend to occur under the influence of a mid-latitude migratory anticyclone that induce persistent cloudless conditions preceding day 0, leading to enhanced photosynthetically active radiation (PAR) starting around day -8, and positive sea surface temperature (SST) anomalies between days -4 and +4. We hypothesise that HBEs are mainly modulated by i) mixing and advection that could contribute to a greater availability of nutrients in the upper sea layers before the onset of the anticyclonic anomalies; and ii) increased thermal stratification related to positive PAR and SST anomalies that would promote phytoplankton growth during the anticyclonic regime. Furthermore, we show that the Madden-Julian Oscillation modulates the frequency of nFLH’ and thus of HBEs, a result that suggests an enhanced predictability of these cases.

Honeydew production by the Giant Willow Aphid (Tuberolachnus salignus, Hemiptera: Aphididae) and its effect on foraging yellowjackets (Hymenoptera: Vespidae).

Understanding the factors that promote the success of invasive species is important for managing biological invasions. Interactions between invasives and other species (e.g., competitors, pathogens, or predators), could favor or limit their success. In recent decades, yellowjacket wasps, including Vespula germanica and V. vulgaris, have successfully established in Patagonia. Additionally, the invasive willow Salix fragilis has invaded areas next to watercourses, which in turn are typically colonized by the giant willow aphid (GWA, Tuberolagnus salignus), an additional species characterized as a successful invader in many regions worldwide. Aphid exudate (honeydew) has been reported to be used as a carbohydrate source by social wasps. The aim of our study was to gain a better understanding of the infestation pattern of the GWA in northwestern Patagonia, its effect on exudate availability and its relationship with yellowjacket foraging patterns. The study was conducted under the working hypothesis that the increase in the size of GWA colonies and resulting honeydew production, will fuel an increase in local Vespula spp. We found that the aphid honeydew is produced in relatively high amounts in the region (estimated at 1517 ± 139 Kg/ha/season), with strong indications that it is used by yellowjackets because of the significantly higher abundance levels of yellowjackets foraging on honeydew. The interaction of three invasive species, willows, GWA and yellowjackets, needs to receive special attention to develop future environmentally-sound mitigation tools of these nuisance pest.

A new lizard species of the Liolaemus kingii group (Squamata: Liolaemidae) from northwestern Chubut province (Argentina).

We describe Liolaemus attenboroughi sp. nov., a lizard distributed in the northwestern Patagonian Steppe of Chubut province (Argentina) previously confused with L. kingii (Bell 1843). Recent studies based on molecular evidence supports its evolutionary independence. Here we provide a morphological diagnosis of this lineage, comparisons between three molecular species delimitation methods, and an updated phylogeny of the L. kingii group. Based on current knowledge of its distribution, this new species is allopatric with geographically close species of the L. kingii group.

The Influence of Age, Sex and Season on Andean Condor Ranging Behavior during the Immature Stage.

Immature individuals move from their natal area to the area where they settle and reproduce, and this may take several years. This process is essential for long-lived species such as vultures and condors, which spend long periods as immature and move extensively. We studied the movement behavior of 26 GPS-tagged immature Andean condors (Vultur gryphus) from northwestern Patagonia throughout the immature stage, analyzing whether these patterns differed according to age, sex and season. We found that season and age influenced home range size and flight distances, the warm season being when immature condors move most; movement patterns were greater in sub-adults than in juveniles. The age effect was associated with the sex of individuals, with males increasing their home range more than females. Our results provide the first description of how immature Andean condor movement patterns are affected by internal and external factors. This information could be key to understanding condor responses to environmental change and threats at different stages during their immature phase. Until now, condor conservation efforts have not considered the areas used by dispersing individuals. Our results increase our understanding of ranging behavior during the immature stage of this threatened bird, enabling us to improve the conservation policies and management strategies designed to protect them.

Land use and systematic survey in the study of hunter-gatherers from northwestern Patagonia, Argentina

In this paper, we focus on the results of the archaeological research in the Diamante Valley, the southernmost limit of the expansion of agriculture, sedentary societies, and the Inka empire (Fig. 1). We conducted the first fieldwork in this area involving random surface sampling, followed by test pits in open-air sites. Our analyses show changes in the settlement pattern of hunter-gatherer societies. During the first part of the Late Holocene (3000–1500 years BP), hunter-gatherers used the highlands and the piedmont seasonally. The archaeological evidence suggests a context of resource abundance and frequent movements from one patch of resources to the other in both biogeographic units. During the last part of the Late Holocene (post-1500 BP period), the increased demography made hunter-gatherers stay longer in each patch. In this later period, we observe a settlement pattern that combines, on the one hand, short-term particular tasks camps with shallow anthropogenic deposits, low artifactual density, richness, and diversity, and on the other hand, larger residential base camps with deep deposits, high artifactual density, richness, and diversity. We also find differences in how hunter-gatherers use the two biogeographic units. We find short-term non-residential camps and larger residential camps in the piedmont. Here we found versatile toolkits with abundant cores and cortex. Even though basalts are abundant in the highlands, there is a more significant amount of non-local raw materials, such as obsidians. Projectile points and scrapers dominate the assemblages, which might lead to task-specific activities such as hunting and processing guanacos. From these results, we can affirm that Late Holocene hunter-gatherer groups from Diamante Valley had an excellent knowledge of the landscape and took advantage of the different altitudinal gradients' different resources with an organized settlement pattern.

Small mammals in pellets of birds of prey from a desert ecotone in Northwestern Patagonia, Argentina


 
 
 Uno de los rasgos distintivos de las tierras áridas sudamericanas es la composición de pequeños mamíferos. En este trabajo se presentan resultados tafonómicos y taxonómicos de restos óseos de micromamíferos (≤ 1 kg) recuperados de egagrópilas de aves rapaces encontradas en una caverna localizada en la provincia de Neuquén (Argentina). El análisis tafonómico reveló bajas proporciones de elementos modificados por la digestión y de elementos rotos como también abundancias relativamente altas de elementos esqueléticos, un patrón que sugiere que las egagrópilas fueron acumuladas por lechuzas de campanario (Tyto furcata). Se identificaron restos de miembros de cinco géneros de roedores (Calomys, Eligmodontia, Phyllotis, Oligmodontia, Ctenomys). Los resultados de estos análisis deberían contribuir a los estudios ecológicos en curso, especialmente en aves de presa del noroeste de la Patagonia.
 
 

Honeys from Patagonia revealed notable pesticide residues in small-scale agricultural landscapes in the past decade

Bees are major pollinators of wild and cultivated plants. Pesticides have been pointed out as a major driver of wild bee declines and of notorious honey bee colony losses, with high pesticide inputs frequently linked to large-scale agriculture. We explored the presence of pesticide residues in Apis mellifera honeys from a region characterised by small-scale agriculture in North-western Patagonia, Argentina in 2014. We compared Argentine and European Union (EU) regulations for pesticide residues found, and investigated the correlation with the botanical diversity of honey palynological spectrum. We identified residues of four pesticides in seven out of ten samples (the organophosphates Chlorpyrifos-ethyl, Pirimiphos-methyl and Dichlorvos, and the pyrethroid Cypermethrin); with concentrations higher than the maximum residue levels allowed in honey by UE. We found moderate evidence that the number of pesticides in honey correlated negatively with the diversity of pollen spectrum. Our results suggest risks due to pesticides to pollinators and human health also in small-scale agricultural areas. We highlight the need of strengthen regulations and controls in Argentina and Latin America regarding pesticide use in agriculture and pesticide residues in honey.

Molecular and cultural characterization of Morchella spp. from disturbed environments of central-southern Chile

In Northwestern Patagonia (Chile), three species of Morchella from undisturbed environments have been identified to date: Morchella tridentina, Morchella andinensis and Morchella aysenina, all belonging to the Elata clade and associated mainly with Nothofagus forests. In this study, the search for Morchella specimens was extended to disturbed environments in Central-Southern Chile, to further explore Morchella species diversity in the country, which is still very limited. The Morchella specimens were identified through multilocus sequences analysis, and the mycelial cultures were characterized, establishing comparisons with specimens from undisturbed environments. To the best of our knowledge, these results reveal for the first time in Chile the presence of the species Morchella eximia and Morchella importuna, and in the case of the last one also the first record in South America. These species were found associated almost exclusively with harvested or burned coniferous plantations. The in vitro mycelial characterization revealed certain inter- and intra-specific patterns of the morphology, such as pigmentation, mycelium type, and development and formation of sclerotia, which varied according to growth media and incubation temperature. The growth rates (mm/day) and mycelial biomass (mg) were significantly influenced by the temperature (p < 0.05), with maximum rates (>10 mm/day) and biomass (approx. 20 mg) between 20 and 24 °C, while a significant growth reduction (70–90%) was observed at 28 °C, mainly in the species from undisturbed environments. Potato-dextrose (PDA) medium stimulated the greatest mycelial density and sclerotia formation in most of the isolates, mainly in M. eximia (UDEC-LAF 236 isolate) which recorded the best mycelial growth performance. Among isolates, UDEC-LAF 236 also showed the best performance in sclerotia production (>350 sclerotia/dish) in 10 days of growth. This study contributes to the knowledge of the diversity of Morchella species in Chile by broadening the species range to those from disturbed environments. It also provides molecular and morphological characterization of the in vitro cultures of different Morchella species. The report on M. eximia and M. importuna, species known as cultivable, adapted to local climatic and edaphic conditions could represent the first step to developing artificial Morchella cultivation methods in Chile.

A new giant titanosaur (Dinosauria, Sauropoda) from the Upper Cretaceous of Northwestern Patagonia, Argentina

Chucarosaurus diripienda gen. et sp. nov. is a new and large titanosaurian sauropod from the Neuquén Basin, Rio Negro Province, Patagonia. The specimen was discovered in the Upper Cretaceous strata of the Huincul Formation (middle Cenomanian–lower Turonian). It includes appendicular and relatively slender elements, with a femoral total length of about 1.9 m long. This taxon shows a unique combination of characters indicating that appendicular bones such as the femur, ischium and tibia, show a remarkable morphological variety, greater than previously described, and are morphologically informative as source of phylogenetic data. A cladistic phylogenetic analysis placed Chucarosaurus well nested within the Colossosauria clade.

Microclimate and species composition shape the contribution of fuel moisture to positive fire-vegetation feedbacks

Ecosystems with positive fire-vegetation feedbacks are highly sensitive to extreme fire events, which are expected to increase in frequency with climate change. Understanding mechanisms maintaining flammability differences between alternative vegetation states is key to elucidate possible ecosystems shifts related to altered fire regimes. Here we assessed whether microclimatic differences between pyrophobic forests and pyrophilic shrublands in northwestern Patagonia can affect the fuel moisture content and partially explain their contrasting flammability. We measured dead and live fuel moisture content and recorded air temperature and relative humidity during one fire season in 10 sites corresponding to either forest or shrubland physiognomy. To disentangle effects from microclimate and species composition on live/dead fuel moisture content we used similar-composition fuels (wood sticks and single-species live leaves) and fuel mixtures (litter and a mixture of live leaves). We found that forests’ microclimate is cooler and moister than shrublands’, harbouring dead fuels with higher moisture content, irrespective of species composition. This suggests that dead fuel moisture content is contributing to make forests less flammable than shrublands. Live fuels tended to show higher moisture content under the forest microclimate, but only when single-species samples were considered. Contrarily, the species mixtures showed higher moisture content in shrublands, the most desiccant communities, suggesting that live fuel moisture content does not contribute to make shrublands more flammable.

Fires and rates of change in the temperate rainforests of northwestern Patagonia since ∼18 ka

We examine the temporal and spatial structure of wildfires and rates of vegetation change in the Pacific sector of northwestern Patagonia (40°-44°S) over the last ∼18,000 years. Macroscopic Charcoal Accumulation Rates (CHAR), a proxy of past local fires, shows a geographic variation that mirrors the modern north-to-south and low-to-high elevation increase in annual precipitation and decrease in precipitation seasonality, and the frequency of explosive volcanic events. Variability in past fires is evident at multiple timescales, with a significant multi-millennial low between ∼18–13.1 ka, an abrupt rise between ∼13.1–12.5 ka, and heightened fire activity between ∼11.4–8.2 ka with significant high values between ∼10–9.4 ka. A subsequent decline led to the lowest Holocene values between ∼6–5.4 ka, which rose and led to significant high values between ∼3.1 ka and the present. Andean and Western Upwind Environments share a multi-millennial structure of fire activity since ∼18 ka, overprinted by millennial and centennial-scale divergences. These differences underscore the role of explosive volcanism as a trigger or modulator of fire activity in the vicinity of Andean eruptive centers. We posit that fire activity in Western Upwind Environments was driven primarily by hydroclimate variations, namely changes in the intensity of the Southern Westerly Winds. Compilations of CHAR and the Rates of Change (ROC) parameter, a measure of the magnitude and rapidity of changes in the pollen records, covary during the onset of the interglacial fire regime at ∼13.1 ka and the last ∼4000 years, suggesting that fires catalyzed vegetation changes during specific intervals since the last glaciation. Highly mobile human occupations deployed along the coasts started at ∼6.2 ka, increased in pulses, and spread widely during the last two millennia. Covariation with CHAR and ROC since ∼4 ka suggests that hunter-gatherer-fishers contributed to enhanced fire activity and abrupt vegetation changes at regional scale. The ubiquitous fire maximum over the last four centuries relates to widespread settlement and associated large-scale land clearance conducted by European/Chilean settlers.

Population expansion of the invasive sea anemone Metridium senile in the spatial mesoscale of a sea urchin bed in north-western Patagonia

Population expansion of the invasive sea anemone Metridium senile in the spatial mesoscale of a sea urchin bed in north-western Patagonia

&lt;i&gt;Corrigendum to&lt;/i&gt;: Local patterns of edaphic mesofauna distribution in the arid Patagonian steppe, Argentina

Mesofauna represents a major component of soil biological community and play a critical role in maintaining soil quality, as well as a range of ecosystem functions. A split&amp;#x2013;split plot design was performed with the aim of identifying the main predictors (phytogeographical criteria, cover type and environmental variables) of edaphic community structure under the effect of desertification. The study also aimed to examine the spatial and seasonal distribution of mesofauna community according to phytogeographical criteria (shrubland vs grassland) and cover type (bare vs covered soil) in the north-western Patagonian steppe of Argentina. The relationship between edaphic fauna, environmental variables and site location was investigated using redundancy analysis (RDA), while the main predictors of edaphic community were analysed using generalised linear mixed models (GLMMs). A total of 43 taxa of Oribatida were found in 168 samples. GLMM approaches selected cover type due to its higher effect on mesofauna community. In this sense, cover type was more important than phytogeographical criteria and environmental variables as predictor of mesofauna community. These findings contribute to a better understanding of how the distribution of mesofauna community respond in Patagonia steppe.