Somuncura Plateau Research Articles

Mass mortality of the Critically Endangered naked characin (Gymnocharacinus bergii): Possible causes and impact

Abstract The naked characin (Gymnocharacinus bergii) is the only endemic fish of the arid Patagonia of Argentina, living only in the thermal headwaters of the Valcheta Stream in the Somuncura Plateau. This species is listed as Critically Endangered on the IUCN Red List. In April 2018, a massive mortality event was observed in the species. Parasitological studies identified the cause as an epidemic of white spot disease, caused by the parasite Ichthyophthirius multifiliis (Ich). Ich is a common disease in aquaculture settings, but it has also been reported as an epizootic in wild fish populations across tropical and temperate regions worldwide. This occurrence is associated with the introduction of fish into non‐native environments. This article presents the first recorded instance of a mass mortality event and Ich outbreak in the naked characin. It includes a mapping of the disease in the headwaters of the stream, an estimation of the impact on the species' population size, and an analysis of potential causes associated with this epidemic. The results indicate that the epizootic produced mortality of 82% of the global population of the naked characin and was linked to the presence and high abundances of the invasive fish species Uruguay tetra (Cheirodon interruptus). The disease occurred in stream sectors where both characid species coexist, particularly in areas with the highest water temperatures. The Ich outbreak represents the most recent and severe threat recorded for the Critically Endangered naked characin. Implementing control measures against the invasive Uruguay tetra is imperative to prevent future outbreaks that could push the species to the brink of extinction in the near future. This study provides crucial information for assessing current management interventions and developing new strategies within the framework of the action plan for naked characin conservation.

The Critically Endangered El Rincon stream frog: Population viability and management actions in Patagonia, Argentina

Abstract The El Rincon stream frog (Pleurodema somuncurense) is a microendemic species currently restricted to the thermal headwaters of the Valcheta Stream in the Somuncura Plateau, Northern Patagonia, Argentina. This species is listed as Critically Endangered on the IUCN Red List. The critical status of the El Rincon stream frog requires urgent management actions. Population viability analysis is one of the most effective tools to predict extinction risk and assess the potential effect of management actions. It is also helpful in knowing the minimum viable population (MVP) and minimum area requirements (MAR). However, this tool is rarely used to model viability in endangered amphibians. This work aimed to: (i) estimate the extinction risk of each local population of El Rincon stream frogs; (ii) estimate the MVP and MAR; and (iii) model reintroduction and supplementation of the population as management strategies for this species. Practical management actions are also suggested for each relict population. Population viability analyses were developed in Vortex 10.3.5.0 to estimate each local population's extinction risk, MVP and MAR. Supplementation and reinforcement of individuals were also modelled for local populations that are below the MVP. The estimated MVP was 430 individuals, while MAR reached 683 m2. Modelling of reintroducing individuals showed that a single reintroduction of at least 50 adults, 140 juveniles, or 1,000 tadpoles would be needed to achieve a viable population. Local populations below the MVP would benefit from supplementation of a pair of adult frogs every 17 to 20 years. This study provides a fundamental basis for assessing and improving current management and planning future conservation strategies within the framework of the El Rincon stream frog action plan.

Los restos faunísticos del sitio arqueológico Tembrao (provincia de Río Negro, Argentina)

En este trabajo se presenta el análisis de los materiales faunísticos del sitio Tembrao, ubicado en un pequeño valle al pie de la meseta de Somuncurá (sur de la provincia de Río Negro). Un fechado realizado sobre restos faunísticos ubica la ocupación del lugar en el Holoceno tardío final. El conjunto está conformado principalmente por restos óseos de mamíferos, entre los que predominan los de artiodáctilos. Se propone que los guanacos habrían sido la presa principal de los cazadores recolectores pre-hispánicos, mientras que los restos de ovejas fueron ingresados por las ocupaciones modernas del paraje Tembrao. Se discute la disponibilidad de recursos faunísticos en cercanías del sitio, especialmente de guanacos sobre la meseta de Somuncurá, y las implicancias de la presencia de elementos foráneos (valvas de almejas fluviales y de moluscos marinos, y probablemente cáscaras de huevos de Rhea americana). En base al análisis se infiere un patrón de subsistencia basado en pocas especies, similar al de otras regiones mesetarias de Norpatagonia y claramente diferenciado de aquel del litoral marino y de los valles fluviales.

Artefactos de molienda en el este de Norpatagonia (provincia de Río Negro, Argentina): un estudio de colecciones arqueológicas

En este trabajo se presentan los resultados del análisis tecno-morfológico y morfológico-funcional de los artefactos líticos de molienda provenientes del área del valle medio e inferior del río Negro, y del piedemonte de la meseta de Somuncurá (provincia de Río Negro). Los materiales analizados forman parte de tres colecciones del Museo de La Plata y una colección privada depositada en la localidad de San Antonio Este. Los objetivos principales de este trabajo son caracterizar la producción, uso y descarte de conjuntos de molienda del área y generar información de base para discutir estrategias tecnológicas relativas a esta parte del registro arqueológico a nivel regional. En el conjunto analizado se identificaron diferentes grupos tipológicos vinculados a la molienda (morteros, molinos, manos de mortero y de molino y artefactos compuestos) confeccionados, en su mayoría, sobre materias primas locales (areniscas, basaltos y otras rocas ígneas). El proceso de manufactura habría involucrado cierta regularidad en cuanto la selección y modificación de las materias primas para manufacturar los artefactos. La molienda en el área estaría vinculada con estrategias de equipamientos de sitios y posiblemente con un proceso de intensificación en la explotación de recursos. El estudio sistemático de colecciones representa un medio para su puesta en valor y para la protección del patrimonio arqueológico.

Phylogeography and palaeomodelling of Duseniella patagonica (Barnadesioideae), an early-diverging member of Asteraceae endemic to the Argentinean Monte and Patagonia

AbstractWe performed an integrated phylogeographical and palaeoclimatic study of an early-diverging member of Asteraceae, Duseniella patagonica, endemic to Argentina. Chloroplast and nuclear markers were sequenced from 106 individuals belonging to 20 populations throughout the species range. We analysed genetic spatial distribution, diversity and structure, tested for range expansion, estimated divergence times, reconstructed ancestral areas and modelled present and past species distributions based on climatic data. Duseniella diverged from its sister genera during the Late/Middle Miocene. Its ancestral area included southern Monte plus eastern and central Patagonia. A vicariant event separated Monte and Patagonian clades during the Plio-Pleistocene. This would have involved unfavourable climate, soil, elevation, volcanism and/or other geomorphological processes between 40 and 43.5°S, in the sourroundings of the Somuncura plateau. Each clade possesses its own haplotypes and nucleotypes. Two populations, one in southern Monte and the other in eastern Patagonia, contain the highest diversity and exclusive haplotypes, representing hypothetical ancestral refugia. Northern Monte and southern Patagonian populations show low to null genetic diversity, being the most recently colonized areas. Climatic models indicate that winter temperature influenced the distribution of Duseniella, with an increase in probability of occurrence during colder periods, thus enabling diversification during glacial episodes.

Análisis espacial del sitio Amigo Oeste, Meseta de Somuncurá (Río Negro, Argentina)

En este trabajo analizamos las distribuciones espaciales de los artefactos líticos en Amigo Oeste, un sitio al aire libre ubicado en la región de la meseta de Somuncurá (Río Negro, Argentina). Una de las principales singularidades del sitio es que una gran proporción de las evidencias arqueológicas registradas consiste en Puntas Cola de Pescado (PCP), artefactos de diagnóstico asignados a la transición Pleistoceno-Holoceno, lo que demuestra su relevancia para el estudio del poblamiento temprano de las Américas. El sitio se extiende tanto en la cima como en la ladera sureste de un cerro de 84m de desnivel.El relevamiento de información espacial en este sitio se realizó mediante 292 unidades transectas y recolección puntual de artefactos registrados mediante GPS no diferencial y teodolito electrónico. Se recolectaron 2575 artefactos líticos entre núcleos, artefactos formatizados y artefactos no formatizados. Hasta el momento el sitio ha sido interpretado como un lugar de visualización para control del entorno (que pudo haber sido usado como campo de caza), donde se realizaron tareas de reequipamiento de PCP, así como otras actividades relacionadas con la cacería.Con el objetivo de explorar patrones espaciales en los indicadores de actividades realizadas en el sitio, los datos generados en trabajos previos (la ubicación de los artefactos y los atributos generados desde el punto de vista tecno-morfológico y morfológico-funcional, así como información ambiental) se integraron en un Sistema de Información Geográfica, y se realizó un análisis espacial exploratorio para definir estadísticamente la existencia de agrupaciones en los artefactos, en los atributos asociados a ellos, así como el número de agrupaciones y su ubicación. Este trabajo permitió lograr un mayor conocimiento sobre las áreas de actividad en el sitio y en su entorno inmediato.

Status and population dynamics of the Critically Endangered Valcheta frog Pleurodema somuncurense on the Patagonian Somuncura Plateau

ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 40:163-169 (2019) - DOI: https://doi.org/10.3354/esr00988 Status and population dynamics of the Critically Endangered Valcheta frog Pleurodema somuncurense on the Patagonian Somuncura Plateau Melina Alicia Velasco1, Igor Berkunsky2, Mauricio Sebastián Akmentins3, Camila Alejandra Kass1,4, María Luz Arellano1, Tomás Martinez Aguirre1, Jorge Daniel Williams1, Federico Pablo Kacoliris1,* 1Sección Herpetología, División Zoología Vertebrados, CONICET, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, Argentina 2Instituto Multidisciplinario sobre Ecosistemas y Desarrollo Sustentable, CONICET, Universidad Nacional del Centro de la Provincia de Buenos Aires, Tandil, Argentina 3Instituto de Ecorregiones Andinas (INECOA), Universidad Nacional de Jujuy - CONICET, San Salvador de Jujuy, Argentina 4Universidad Nacional de Chilecito, CONICET, La Rioja, Argentina *Corresponding author: kacoliris@fcnym.unlp.edu.ar ABSTRACT: Amphibian populations are declining globally. In this scenario, detailed information on their ecology is crucial to determine the status and extinction risk of their populations and, therefore, better plan conservation activities. The Valcheta frog Pleurodema somuncurense is a Critically Endangered species, which is endemic to the Valcheta Stream, Patagonia, Argentina. We assessed the status of this species at the metapopulation level, which we consider is a key step in planning management activities. We conducted visual encounter surveys from 2013 to 2019 to determine the distribution range of each local population of the Valcheta frog. During 2015, we also applied a capture-recapture survey to estimate the density and apparent survival of 1 local population. We used POPAN models for density estimation and the classic model of Cormack-Jolly-Seber to estimate apparent survival, using snout-vent length as a covariate. The metapopulation of the Valcheta frog is composed of 9 isolated local populations: 7 extant and 2 extinct. The extant populations have population sizes ranging from 243 to 4516 individuals. The small size of the smaller local populations makes their long-term viability in isolation unlikely. We found a positive correlation between the apparent survival and the snout-vent length of individuals. Our results showed that management strategies should be aimed at ensuring the long-term survival of this species, with a focus on the recovery of extinct populations, the restoration of disturbed habitats and the improvement of connectivity between local populations. KEY WORDS: Local populations · Density · Apparent survival · Capture-mark-recapture Full text in pdf format PreviousNextCite this article as: Velasco MA, Berkunsky I, Akmentins MS, Kass CA and others (2019) Status and population dynamics of the Critically Endangered Valcheta frog Pleurodema somuncurense on the Patagonian Somuncura Plateau. Endang Species Res 40:163-169. https://doi.org/10.3354/esr00988 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 40. Online publication date: November 14, 2019 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2019 Inter-Research.

A traceological approach to the use of Laguna Azul during the Late Holocene (from ca. 2000 years BP) in Norpatagonia, Argentina

The lagoon environments were places recurrently visited and inhabited by hunter-gatherer groups throughout different areas of North Patagonia. These places were very important in the life of these mobile groups; they were part of their itineraries and they regularly returned to their shores. The Somuncura plateau’s lagoons (Rio Negro province, Argentina) represent one of these spaces, where, in addition to a vital resource such as water, it can be found a greater variety and biological abundance, facilitating a certain shelter during mobility. The Laguna Azul site is one of these places, where the hunting blinds (known as “parapetos”) are the most outstanding anthropic modification of the landscape. In this paper, we present the results obtained from the lithic material recovered from one of these structures, which is the most abundant material in the record. The knowledge about the specific uses of these stone tools, obtained through the functional analysis, is deepened to determine trends in the manufacturing process and designs chosen. The studies developed in this paper will expand the understanding about the technological decisions implemented by the hunter-gatherers that inhabited the Somuncura plateau during the Late Holocene.

Phylogenetic relationships and intraspecific diversity of a North Patagonian Fescue: evidence of differentiation and interspecific introgression at peripheral populations

Peripheral sites usually offer suboptimal conditions for species with wide distributions, where expression of phenotypic variability and potential interspecific hybridization might be enhanced. The Patagonian steppe, the largest and southernmost dryland ecosystem in South America, is characterized by natural rangelands dominated by grasses. Festuca pallescens is a keystone species with a wide distribution in Patagonia over diverse environments reaching the extreme arid zones in the Somuncura plateau, a biogeographical island. Our aim is to study the phylogenetic relationships among Festuca pallescens populations as well as between this species and the sympatric F. argentina in North Patagonia. We analysed fourteen populations along a west-east transect of about 500 km in North Patagonia with three types of molecular markers: ITS, chloroplast trnL-F and eight nuclear microsatellites. Bayesian inferences, maximum parsimony and maximum likelihood analyses with trnL-F and ITS showed that F. pallescens is related to the Patagonian clade within the Festuca phylogeny. However, the easternmost populations of F. pallescens at Somuncura plateau were highly differentiated from the other populations and clustered with F. argentina (a sympatric species of the Asian-American clade). Principal coordinates analyses and Bayesian clustering performed with nuclear microsatellites as well as morphoanatomical traits, showed an intermediate position of one of these easternmost populations with respect to the two species, suggesting admixture. The high genetic variability observed in these peripheral populations highlight their relevance for conservation and might be indicating the existence of evolutionary processes triggering events of speciation in the Patagonian fescues.

The rainbow trout is affecting the occupancy of native amphibians in Patagonia

In this work, we assessed the occupancy of two native amphibian species of the Valcheta stream in the Somuncura Plateau, northern Patagonia: the Valcheta frog, Pleurodema somuncurense and the Argentine common toad, Rhinella arenarum. We hypothesized that the occupancy of both amphibian species will be shaped by the presence of trout; we also expected a decline in occupancy assuming that the new predator in the system will affect native amphibian populations. Between December 2014 and March 2015, we conducted surveys in 148 sites along the headwaters of Valcheta stream. We modelled the occupancy by including the presence of trout, the temperature of water and the coverage of rocks and vegetation as site-habitat covariates. Models including trout were among the best ranked for both amphibian species. The presence of trout reduced the occupancy of both species and the magnitude of this reduction was much higher in the Valcheta frog than in the Argentine common toad. Overall, our results are of great relevance for land managers considering that the Valcheta frog is among the only three IUCN Critically Endangered amphibians in Argentina.

Distribución de núcleos en el sector central de la mesta de Somuncurá (Río Negro, Argentina). Relaciones entre la base regional de recursos líticos y el aprovisionamiento de materias primas líticas

In this paper we address rock procurement among hunter-gatherers societies from Somuncura plateau through the study of cores and quarries. Different analyses allowed us to infer the possible trajectories of the main raw materials recognized in the Talagapa stream basin: chalcedony, brown chert and obsidian. The raw materials and cores distribution allowed us to distinguish different provisioning strategies, use patterns and cores discard. The use of the most frequently represented rocks is related to the trajectories. While chalcedony had a main role, brown chert acted as a complement in certain sectors in the basin and obsidian appears as a secondary raw material.

Current distributional status of the critically endangered Valcheta Frog: Implications for conservation

The Valcheta Frog, Pleurodema somuncurense (Cei, 1969), is a critically endangered species endemic from Somuncura plateau, Patagonia, Argentina. Although this frog is facing several human-related threats, the available information about its population status and trends is scarce. In order to update the range of the species, from 2013 to 2015, we conducted exhaustive surveys in all its geographical distribution, including sites never explored in the past. In 2014, we estimated occupancy and probability of detection with a three-visit survey in 40 sites of headwaters of Valcheta stream. Frogs were present in 58% of sites, and the probability of detection was high. We increased the known range of Valcheta Frog in 160%, by adding new sites occupied by the species. However, the status of the species remains of great concern, since its total range barely reaches 4 square kilometres.Keywords: threatened amphibians, Somuncura plateau, occupancy models, population decline.

A new threat for the endangered frog Atelognathus reverberii (Anura: Batrachylidae) in Argentinean Patagonia

Atelognathus reverberii (Cei, 1969) is an endemic terrestrial frog that inhabits volcanic clay lagoons (mostly semi-permanent or temporary). These lagoons are scattered throughout the desertic Somuncura Plateau of Argentinean Patagonia (Cei 1969, Martinazzo et al. 2011). This frog species was listed as Endangered in the IUCN’s red list (IUCN 2014) and as Vulnerable in the last categorization of Argentinean amphibian fauna (Vaira et al. 2012).

Geology of the Anecón Grande area, Patagonia (Río Negro), Argentina

This contribution presents a 1:200,000 scale geologic map of the Anecón Grande area in northern Patagonia (41°00′–41°30′ S/70°00′–70°30′ W, Río Negro province, Argentina), covering around 2300 km2. The map results from a combination of classical visual stereoscopic interpretation of aerial photographs and remote sensing data, later corroborated by field surveys. The geology of the Anecón Grande is composed of a thick succession of intermediate to acidic volcanic and pyroclastic rocks (Late Triassic to Paleogene), and a thick pile of basaltic lava flows of the Somuncura Plateau (Neogene to Quaternary). Volcanic landforms, flat lava flows called ‘escoriales’, and regional peneplains are typical Patagonian landscapes in the Anecón Grande area. The map is of further interest for its socio-cultural relevance because the Anecón Grande area was settled by the Anikhon Grande Mapuche community, being one of the Native South American People and First Nations in Patagonia. Seven sites of geological interest are shown on the map which informs the reader of source areas of lithic materials (geodes, obsidian, peridotite mantle xenoliths) which may be potentially useful in the manufacturing of handicrafts by Mapuche people.

A new Bothriurus (Scorpiones, Bothriuridae) from the Somuncura Plateau, with additions to the knowledge to the endemic scorpion fauna of the area

A new Bothriurus (Scorpiones, Bothriuridae) from the Somuncura Plateau, with additions to the knowledge to the endemic scorpion fauna of the area

A new Bothriurus (Scorpiones, Bothriuridae) from the Somuncura Plateau, with additions to the knowledge to the endemic scorpion fauna of the area

Bothriurus nendai n. sp. is described. This species is endemic to the upper level of the Somuncura plateau, a Patagonian island placed in the Monte Phytogeographic province. This is the third known endemic scorpion from this area. Bothriurus nendai n. sp. is closely related to the patagonicus group; however, several morphological characters separate B. nendai from the species of this group. New data on the scorpion species of the plateau are also provided.

パタゴニア北部，超背弧域に分布するソムンクラ台地玄武岩の成因：ウォズリアイトの脱水溶融起因説

パタゴニア北部，超背弧域に分布するソムンクラ台地玄武岩の成因：ウォズリアイトの脱水溶融起因説

A new endemic scorpion species from the Somuncura Plateau, in northern Patagonia (Scorpiones, Bothriuridae)

A new endemic scorpion species from the Somuncura Plateau, in northern Patagonia (Scorpiones, Bothriuridae)

A new endemic scorpion species from the Somuncura Plateau, in northern Patagonia (Scorpiones, Bothriuridae)

A new scorpion species from Argentina, Bothriurus ceii n. sp., is described. This species belongs to the patagonicus group, which includes Bothriurus patagonicus Maury 1969 and several undescribed species from Patagonia. Bothriurus ceii n. sp. is endemic to the upper level of the Somuncura plateau, which shows characteristics of the Patagonic phytogeographyc province, whereas the surrounding area belongs to the Monte phytogeographyc province. Bothriurus ceii n. sp. can be distinguished from the rest of the species of the patagonicus group because it lacks the VSM and VL carinae of sternite V and metasomal segment I, which are present in the rest of the species of the group.

Paleomagnetism of the late Cenozoic basalts from northern Patagonia

Abstract Late Cenozoic volcanic rocks outcrop in the northern Patagonia Extrandina. Lava flows, characterized as olivine and alkaline basalts, belong to intraplate volcanism. We report paleomagnetic and rock-magnetic studies carried out on Late Cenozoic basalts belonging to the Cráter, Mojón and Moreniyeu Formations. The paleomagnetic sampling comprised 75 sites in lava flows and dikes from the Cráter Formation, three sites in a lava flow from the Mojón Formation and three sites in a lava flow from the Moreniyeu Formation. Alternating field (AF) and thermal detailed demagnetization techniques were used. Most of the samples have a viscous component. The AF procedure was more effective than thermal demagnetization in destroying viscous components and in defining the characteristic remanent magnetizations. Demagnetization curves and rock-magnetic studies suggest that the main remanence carrier is Ti-poor magnetite. Radiometric K-Ar ages were performed on these basalts. The radiometric ages are 0.8±0.1 Ma from outcrops located at Cerro Fermín and 1.9±0.4 Ma from outcrops at Cerro Negro, both at the Cráter Formation. These ages suggest an early-middle Pleistocene age for the lava flows from Cerro Fermín, and a late Pliocene to early Pleistocene age for the Cerro Negro lava flows. Based on the magnetic polarity temporal scale, the Cerro Fermín lava flows have registered the beginning of the Brunhes Chron, while the Cerro Negro basalts could have been extruded during the Olduvai Subchron. The K-Ar radiometric age of the Moreniyeu Formation (1.6±0.2 Ma) suggests an early Pleistocene age for this lava flow. The reverse polarity of its virtual geomagnetic poles (VGPs) is in agreement with the predominant one during the Matuyama Chron and suggests that the Moreniyeu Formation constitutes another volcanic event clearly separate from those of the Cráter Formation. The K-Ar radiometric age of the Mojón Formation (3.3±0.4 Ma) locates it in the middle Pliocene. The VGP polarity would be correlated with some reverse subchron located in Gauss Chron or with the end of the Gilbert Chron. The petrographical and geochemical similarities between the studied basalt and the Somuncura plateau basalts (late Oligocene-early Miocene, located northern and eastern of the study area), together with the time lapsed among between the Mojón and Cráter basalt extrusion suggest the presence in the area of a temporarily extensive thermal anomalies.