The National University of Comahue is an Argentine national university with branches in the provinces of Neuquén, Río Negro and Chubut, with a center in the city of Neuquén and units in Viedma, Bariloche, San Martín de los Andes, Cipolletti, Zapala, Allen, General Roca, Choele Choel, San Antonio Este, Villa Regina, Esquel, Puerto Madryn, Trelew. Wikipedia.
Zenni R.D.,University of Tennessee at Knoxville |
Nunez M.A.,University of Tennessee at Knoxville |
Nunez M.A.,National University of Comahue
Oikos | Year: 2013
Most species introductions are not expected to result in invasion, and species that are invasive in one area are frequently not invasive in others. However, cases of introduced organisms that failed to invade are reported in many instances as anecdotes or are simply ignored. In this analysis, we aimed to find common characteristics between non-invasive populations of known invasive species and evaluated how the study of failed invasions can contribute to research on biological invasions. We found intraspecific variation in invasion success and several recurring explanations for why non-native species fail to invade; these included low propagule pressure, abiotic resistance, biotic resistance, genetic constraints and mutualist release. Furthermore, we identified key research topics where ignoring failed invasions could produce misleading results; these include studies on historical factors associated with invasions, distribution models of invasive species, the effect of species traits on invasiveness, genetic effects, biotic resistance and habitat invasibility. In conclusion, we found failed invasions can provide fundamental information on the relative importance of factors determining invasions and might be a key component of several research topics. Therefore, our analysis suggests that more specific and detailed studies on invasion failures are necessary. © 2012 The Authors. Oikos © 2012 Nordic Society Oikos.
Kuebbing S.E.,University of Tennessee at Knoxville |
Kuebbing S.E.,Yale University |
Nunez M.A.,National University of Comahue
Global Change Biology | Year: 2015
The movement of species is one of the most pervasive forms of global change, and few ecosystems remain uninvaded by nonnative species. Studying species interactions is crucial for understanding their distribution and abundance, particularly for nonnative species because interactions may influence the probability of invasion and consequent ecological impact. Interactions among nonnatives are relatively understudied, though the likelihood of nonnative species co-occurrence is high. We quantify and describe the types of interactions among nonnative plants and determine what factors affect interaction outcomes for ecosystems globally. We reviewed 65 studies comprising 201 observations and recorded the interaction type, traits of the interacting species, and study characteristics. We conducted a census of interaction types and a meta-analysis of experiments that tested nonnative competition intensity. Both methods showed that negative and neutral interactions prevailed, and a number of studies reported that the removal of a dominant nonnative led to competitive release of other nonnatives. Positive interactions were less frequently reported and positive mean effect sizes were rare, but the plant characteristics nitrogen fixation, life cycle (annual or perennial), and functional group significantly influenced positive interactions. Positive interactions were three times more frequent when a neighboring nonnative was a nitrogen fixer and 3.5 times lower when a neighboring nonnative was an annual. Woody plants were two or four times more likely to have positive interactions relative to grasses or herbs, respectively. The prevalence of negative interactions suggests that managers should prepare for reinvasion of sites when treating dominant nonnatives. Though positive interactions were infrequent, managers may be able to anticipate positive interactions among nonnatives based upon traits of the co-occurring invaders. Predicting positive nonnative interactions is an important tool for determining habitat susceptibility to a particular invasion and for prioritizing management of nonnatives with a higher likelihood of positive interactions. © 2014 John Wiley & Sons Ltd.
Aprea J.L.,National University of Comahue
International Journal of Hydrogen Energy | Year: 2014
For decades, the issue of hydrogen quality specification has been a source of complexity and confusion in particular for end users, especially because of the jargon spoken by different providers and clients in varied and diverse areas of application. Virtually every requirement was established within the customer-supplier relationship. The rise of new hydrogen technologies, the emergence of new devices like fuel cells and the spread of knowledge, together with the growing need for uniformity has pushed the specialists to solve this problem. As a result, standardization seems to be the key to accomplish with quality goals at the lowest cost possible. This article discusses the traditional concepts used in the past, the current situation, the standards used today and future developments in hydrogen quality requirements to simplify and facilitate the use and the applications of hydrogen and blends with a careful respect for the quality of the product and safety. © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Harder L.D.,University of Calgary |
Aizen M.A.,National University of Comahue
Philosophical Transactions of the Royal Society B: Biological Sciences | Year: 2010
Pollen limitation (PL) of seed production creates unique conditions for reproductive adaptation by angiosperms, in part because, unlike under ovule or resource limitation, floral interactions with pollen vectors can contribute to variation in female success. Although the ecological and conservation consequences of PL have received considerable attention in recent times, its evolutionary implications are poorly appreciated. To identify general influences of PL on reproductive adaptation compared with those under other seed-production limits and their implications for evolution in altered environments, we derive a model that incorporates pollination and postpollination aspects of PL. Because PL always favours increased ovule fertilization, even when population dynamics are not seed limited, it should pervasively influence selection on reproductive traits. Significantly, under PL the intensity of inbreeding does not determine whether outcrossing or autonomous selfing can evolve, although it can affect which response is most likely. Because the causes of PL are multifaceted in both natural and anthropogenically altered environments, the possible outcrossing solutions are diverse and context dependent, which may contribute to the extensive variety of angiosperm reproductive characteristics. Finally, the increased adaptive options available under PL may be responsible for positive global associations between it and angiosperm diversity. © 2010 The Royal Society.
Kuebbing S.E.,Yale University |
Nunez M.A.,National University of Comahue
Nature Plants | Year: 2016
Human activity is creating a global footprint by changing the climate, altering habitats and reshuffling the distribution of species. The movement of species around the globe has led to the naturalization and accumulation of multiple non-native species within ecosystems, which is frequently associated with habitat disturbance and changing environmental conditions. However, interactions among species will also influence community composition, but little is known about the full range of direct and indirect interactions among native and non-native species. Here, we show through a meta-analysis of 1,215 pairwise plant interactions between 274 vascular plant species in 21 major habitat types that interactions between non-native plants are asymmetrical with interactions between non-native and native plants. Non-native plants were always bad neighbours, but the negative effect of non-natives on natives was around two times greater than the effect of non-natives on other non-natives. In contrast, the performance of non-native plants was five times higher in the presence of a neighbouring native plant species than in the presence of a neighbouring non-native plant species. Together, these results demonstrate that invaded plant communities may accumulate additional non-native species even if direct interactions between non-natives species are negative. Put another way, invasions may be more likely to lead to more invasions, requiring more active management of ecosystems by promoting native species restoration to undermine invasive positive feedback and to assist native species recovery in invaded ecosystems. © 2016 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.
Lambertucci S.A.,National University of Comahue
ORYX | Year: 2010
Estimations of the population sizes of threatened species are fundamental for conservation. The current estimate of the population of the Andean condor Vultur gryphus is based on limited local counts. Simultaneous censuses of 10 condor communal roosts were therefore conducted during 2006-2008 in north-west Patagonia, Argentina, to obtain a minimum population number, to estimate the size of the local population, and to describe use of the roosts by season and age classes. I fitted the data to two asymptotic models to calculate the population of condors as a function of the number of communal roosts surveyed. In an area of c. 6,300 km2 I obtained a minimum population size of 246 individuals by direct observation, and a population estimate of 296 condors (range 260-332) by applying the models. This population, the largest known of this species, comprises 68.5% adults and 31.5% immatures. Condors had large aggregations in some communal roosts and used the area seasonally, increasing in numbers from autumn to spring and decreasing in summer. Long-term monitoring of communal roosts across the Andean condors range is essential for the monitoring of this rare and vulnerable species. © 2010 Fauna & Flora International.
Suarez M.L.,National University of Comahue |
Kitzberger T.,National University of Comahue
Journal of Ecology | Year: 2010
1. The understanding of the impacts of climate anomalies on demographic processes involved in forest dynamics is becoming a major global change research objective, as climate-driven demographic changes have the potential to alter ecological processes and change the composition of existing communities. 2. Here, we test whether the effects of climatic variability on Nothofagus dombeyi forest dynamics differ along the W-E precipitation gradient of northern Patagonia, Argentina, due to different controlling factors along the gradient. 3. Using a dendroecological approach, we sampled six N. dombeyi stands along the gradient. Tree death, growth release and sapling birth dates were obtained and used to reconstruct stand mortality, canopy disturbance and establishment patterns in each stand. Discrete extreme climatic events were obtained by applying thresholds to meteorological time series. Bivariate event analysis was performed to examine the temporal relationships between climate events and forest demographic and canopy disturbance patterns. 4. In the xeric region, forest dynamics is driven by drought/heat and humid events. Following drought/heat events we observed standing-dead tree mortality, releases in growth, and tree establishment episodes. Regional synchrony of these events was coincident with droughts registered for northern Patagonia. However, successful establishment was related to wet periods that occurred after drought events, showing the dependence on favourable periods for growth. For wet regions, demographic patterns showed a temporally uniform pattern but with synchronies at the regional and local scales. Canopy openings produced by fallen trees, and consequent release in growth and establishment, were related to both drought and snowy/windy years. The effect of drought in wet region forests was related mainly to the extreme 1998-99 drought in northern Patagonia. 5. Synthesis. Climate in northern Patagonia influences N. dombeyi forest dynamics differentially along a precipitation gradient. In xeric forests, strong but relatively short climatic fluctuations impact forest structure through direct effects on tree demography. In wet forests, climatic-induced mechanical disturbance prevails, driving mortality and subsequent growth and establishment. Considering that recent extreme droughts have the strongest negative impact on N. dombeyi populations at the eastern distributional limits, a change in distribution of this species as a consequence of projected climate change is expected. © 2010 The Authors. Journal compilation © 2010 British Ecological Society.
Merkle J.A.,Laval University |
Fortin D.,Laval University |
Morales J.M.,National University of Comahue
Ecology Letters | Year: 2014
The restricted area of space used by most mobile animals is thought to result from fitness-rewarding decisions derived from gaining information about the environment. Yet, assessments of how animals deal with uncertainty using memory have been largely theoretical, and an empirically derived mechanism explaining restricted space use in animals is still lacking. Using a patch-to-patch movement analysis, we investigated predictions of how free-ranging bison (Bison bison) living in a meadow-forest matrix use memory to reduce uncertainty in energy intake rate. Results indicate that bison remembered pertinent information about location and quality of meadows, and they used this information to selectively move to meadows of higher profitability. Moreover, bison chose profitable meadows they had previously visited, and this choice was stronger after visiting a relatively poor quality meadow. Our work demonstrates a link between memory, energy gains and restricted space use while establishing a fitness-based integration of movement, cognitive and spatial ecology. © 2014 John Wiley & Sons Ltd/CNRS.
Aprea J.L.,National University of Comahue
International Journal of Hydrogen Energy | Year: 2012
Antarctica is a land of research, peace and one of the last refuges of pristine landscapes and pure environments of the planet. Therefore, the installation of a clean energy module at the Esperanza (HopeBay) Scientific Station of Argentina is one of the signs that opens new perspectives for the respect of the environment through the use of renewable energy sources with the aim of replacing fossil fuels currently used in the continent. This article briefly discusses the preparation, installation, commissioning and two years operation of an electrolytic hydrogen generator powered by wind and various devices designed for safe and reliable use of hydrogen for the benefit of the population of the station and visitors. We analyze the acceptance of the new technologies, the possibility of feeding the module independently from local renewable resources and the difficulties encountered due to the extreme conditions at the location. © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Mannion P.D.,University College London |
Calvo J.O.,National University of Comahue
Zoological Journal of the Linnean Society | Year: 2011
Titanosauria is a taxonomically and morphologically diverse clade of sauropod dinosaurs that appeared in the Middle Jurassic and radiated in the mid-Late Cretaceous; however, its intrarelationships are poorly understood. The mid-Cretaceous Argentinean sauropod Andesaurus delgadoi has repeatedly been recovered at the base of Titanosauria, and thus represents a crucial taxon for determining the evolutionary history of this clade; yet it has only received a brief description. Here, we re-describe the holotype, comprising dorsal, sacral, and caudal vertebrae, as well as limb and pelvic elements. Detailed comparisons are made with a global array of titanosauriforms. Andesaurus is a valid genus and can be diagnosed by five autapomorphies: (1) posterior dorsal neural spine height greater than twice centrum height (autapomorphic within Macronaria); (2) square-shaped anterior-middle caudal centra in lateral view; (3) anteroposteriorly elongate fossa present on the anterodorsal corner of the lateral surface of middle-posterior caudal centra; (4) ridge along the midshaft of the ventral surface of metacarpal I, close to the ventromedial margin; (5) prominent ventromedial ridge along the distal half of metacarpal V. Other remains previously attributed to Andesaurus cannot be referred to this genus. Sixteen putative titanosaur synapomorphies can be recognized in Andesaurus, including: (1) lateral pneumatic foramina in dorsal vertebrae situated within fossae; (2) anterior-middle caudal vertebrae with ventrolateral ridges either side of a ventral midline hollow; and (3) lateral bowing of metacarpal I. This revision provides an important foundation for future phylogenetic analyses of titanosaurs, and adds to our growing understanding of this enigmatic clade. Lastly, we recommend the disuse of the coordinated suprageneric rank taxa of Andesaurus (Andesaurinae, Andesauridae, and Andesauroidea), at least until titanosaur intrarelationships are better elucidated. © 2011 The Linnean Society of London.