Showing papers by "National University of Comahue published in 2005"

Landscape influences on occurrence and spread of wildfires in patagonian forests and shrublands

Abstract: Spatial heterogeneity of vegetation types and the abiotic environment can influence the occurrence and spread of wildfires, but in some landscapes the importance of these effects varies under conditions of severe fire weather In the northern Patagonian landscape of forests and shrublands we examined the effects of vegetation type (tall forest vs tall shrubland) and abiotic factors (elevation, topography, and precipitation) on fire occurrence at a broad scale and on fire spread at a fine scale We used satellite images (1985-1999) and aerial photography (1950-1999) to map fires in relation to pre-burn vegetation type and abiotic factors Fire extent is greatest at intermediate elevations and locations of intermediate precipitation Fire extent is limited by lack of fuel quantity at the lower end of the precipitation gradient and by infrequent or insufficient fuel desiccation at the upper end Tall shrublands are proportionally more affected by fire than are adjacent mesic forests of Nothofagus dombeyi and N pumilio Patches of subalpine forests often tend to serve as natural fire breaks, except under the most severe fire weather Tall shrublands are dominated by species that resprout vigorously so that fuels quickly recover In contrast, forests are dominated by species dependent on seed reproduction that sometimes fails after severe fires so that shrublands tend to replace burned forests The greater propensity of shrublands to burn is a positive feedback that is favorable to fire and that accelerates the replacement of forest by shrublands Infrequently occurring severe weather is important in the burning of otherwise relatively fire-resistant subalpine forests Past burning, associated both with drought and early forest clearing, expanded shrublands at the expense of forests so that in the modern landscape an increase in anthropogenic ignitions and the positive feedback of fire and shrublands are synergistically accelerating conversion from forest to shrubland

Edge effects on flower-visiting insects in grapefruit plantations bordering premontane subtropical forest.

Abstract: Summary 1 Over the last decade, there has been much concern about the decline in pollinator abundance and diversity caused by different types of anthropogenic disturbances, including deforestation and habitat fragmentation. However, little empirical information exists documenting this decline and its consequences for cultivated flowering crops. We tested the hypothesis that remnants of natural habitats act as a source of flower-visiting insects for neighbourhood crops. 2 Over 3 consecutive years we evaluated flower-visiting insect diversity, visitation frequency and composition in four grapefruit Citrus paradisi Macf. plantations at increasing distances (edge, 10, 100, 500 and 1000 m) from remnants of subtropical premontane forest in NW Argentina. 3 The frequency of visits to grapefruit flowers decreased by more than twofold as distance to the forest increased and the flower-visiting fauna became more depaupurate. Even the feral africanized honeybee Apis mellifera, the dominant flower visitor to grapefruit flowers, showed a decline at distances > 500 m from the forest edge. However, the greatest relative declines occurred among stingless and solitary bees as well as other native flower visitors, which were rarely seen a few hundred metres inside the plantations. In addition, flower-visiting insect faunas among plantations became more homogeneous as distance from the edge increased. 4 These trends were consistent over years and among plantations up to 50 km apart. Thus, we can conclude that negative forest edge effects on flower-visiting insects inside grapefruit plantations are widespread in the increasingly deforested landscape of NW Argentina. 5 Synthesis and applications. This study provides empirical evidence for considering remnants of natural habitats as a source of both native and alien flower-visiting insects that can be potential pollinators for agriculture. Increasing edge density in agricultural lands, through preservation and restoration of natural habitats, can foster stocks of diverse and abundant insect pollinators.

Composting vs. Vermicomposting: A Comparison of End Product Quality

Abstract: Composts and vermicomposts from a municipal composting plant in northwestern Patagonia, both having undergone a thermophilic phase, (with the vermicompost being inoculated with earthworms after the thermophilic stage) and a nonthermophilic backyard vermicompost were studied. Their effects on soil biological and biochemical properties and plant growth were evaluated in laboratory incubations and a greenhouse trial, using a degraded volcanic soil amended at rates of 20 and 40 g kg−1 of vermicompost or compost. Between the two municipal products, the vermicompost had significantly larger nutrient concentrations than the compost; when mixed with the soil, the vermicompost also had higher microbial populations size and activity, and produced increased ryegrass yields. Compared to the municipal compost, the backyard vermicompost had similar or higher nutrient concentrations but its effects on soil microbial biomass, soil microbial activity and ryegrass yields were lower. Our results suggest that no generalizati...

The importance of phylogenetic scale in tests of Bergmann's and Rapoport's rules: lessons from a clade of South American lizards

Abstract: We tested for the occurrence of Bergmann's rule, the pattern of increasing body size with latitude, and Rapoport's rule, the positive relationship between geographical range size and latitude, in 34 lineages of Liolaemus lizards that occupy arid regions of the Andean foothills. We tested the climatic-variability hypothesis (CVH) by examining the relationship between thermal tolerance breadth and distribution. Each of these analyses was performed varying the level of phylogenetic inclusiveness. Bergmann's rule and the CVH were supported, but Rapoport's rule was not. More variance in the data for Bergmann's rule and the CVH was explained using species belonging to the L. boulengeri series rather than all species, and inclusion of multiple outgroups tended to obscure these macroecological patterns. Evidence for Bergmann's rule and the predicted patterns from the CVH remained after application of phylogenetic comparative methods, indicating a greater role of ecological processes rather than phylogeny in shaping the current species distributions of these lizards.

A new specimen of neuquensaurus australis, a late cretaceous saltasaurine titanosaur from north patagonia

Abstract: A new specimen of the sauropod titanosaur Neuquensaurus australis, collected in the locality of Cinco Saltos (Patagonia, Argentina), provides an opportunity to improve our knowledge of the anatomy of this dinosaur. The elements represented in this specimen include a complete cervical vertebra, most of the dorsal vertebrae, fifteen caudal vertebrae, the complete sacrum articulated to both ilia, one ischium, two femora, one tibia articulated to the fibula and astragalus, and two osteoderms. Surprisingly, the sacrum is composed of seven vertebrae, the last of which, unfused to the other six, is apparently biconvex. A third femur and one tibia were found associated with this specimen; these are morphologically similar but stouter than those belonging to the former specimen.

Giant titanosaur (Dinosauria, Sauropoda) from the Late Cretaceous of Patagonia

Abstract: We report the discovery of a new titanosaurian taxon, Puertasaurus reuili gen. et sp. nov., from Maastrichtian beds of SW Patagonia. Four vertebrae were recovered (i.e., cervical 9, dorsal 2, and two mid-caudals). The new form is diagnosed on the basis of an inflated neural spine on cervical vertebra, and extremely short second dorsal vertebra, among other features. Puertasaurus is one of the largest known sauropod dino-saurs, with dorsal vertebra 2 measuring 168 cm in transverse width. This is the first time that a cervical verte-bra is reported for a giant titanosaur, giving a new insight on neck anatomy of neosauropod dinosaurs.

Citrus peel oil deterpenation with supercritical fluids: Optimal process and solvent cycle design

Abstract: In this work supercritical deterpenation of orange peel oil with carbon dioxide is studied. Optimal schemes and operating conditions are determined through the formulation of a nonlinear programming model that includes reliable thermodynamic predictions with a group contribution equation of state and rigorous unit models. A detailed comparison of binary and ternary equilibrium predictions with available experimental data is reported. Simulation results are in agreement with previous laboratory-scale separation values. Different solvent cycle schemes have been included in the mathematical model. Net profit is maximized taking into account capital and operating costs associated to the complete deterpenation process. Numerical results show that a compression cycle is the optimal solvent recovery system in all cases. Furthermore, optimal operating conditions have been determined in main units (extractor and separator), for the production of both a five-fold concentrate and a high purity aroma, as raffinate, respectively.

Estado del conocimiento de humedales del norte patagónico (Argentina): aspectos relevantes e importancia para la conservación de la biodiversidad regional

Abstract: Las areas de humedal ocupan casi el 5 % del territorio de la Patagonia argentina. En la zona extrandina y el desierto patagonico estos ecosistemas son esenciales para sostener numerosas especies de fauna y flora silvestre. Ademas, los humedales del norte patagonico permiten el desarrollo de comunidades acuaticas complejas y constituyen el habitat critico de grupos de organismos como los peces y los anfibios incluidos en listados de conservacion prioritaria. Estos ecosistemas tienen un funcionamiento complejo que depende estrechamente de las fluctuaciones de las variables meteorologicas y son por lo tanto muy sensibles a los efectos del cambio climatico. En la actualidad el uso de la tierra, la introduccion de especies y la interaccion de estos aspectos con el cambio climatico constituyen las variables de mayor impacto sobre estos ambientes patagonicos. En este trabajo se presenta informacion geografica, geomorfologica y climatica de un numero de humedales del norte de la Patagonia argentina. Por otra parte, se sintetiza informacion sobre la flora y la distribucion de peces y anfibios con el proposito de enfatizar la importancia de estos ambientes en el mantenimiento de la biodiversidad regional. Por ultimo, se senalan los procesos que actualmente afectan a estos sistemas poniendo en evidencia la necesidad de obtencion de conocimientos basicos para el diseno de planes de manejo y conservacion de sus comunidades biologicas

A new sebecosuchian crocodyliform from the Late Cretaceous of Patagonia

Abstract: A well-preserved dentary from the Late Cretaceous of Neuquen Province, Argentina, represents a new taxon of sebecosuchian crocodyliform, Pehuenchesuchus enderi. The specimen retains a number of diagnostic characters and is referable to Sebecosuchia on the basis of two derived features (a longitudinal groove on the lateral surface of the dentary and a sigmoidal tooth row in dorsal view). The new taxon differs from all other sebecosuchians by possessing laterally compressed teeth that lack serrated carinae. A phylogenetic analysis of 30 crocodyliform taxa and two character-taxon matrices, which include many putative sebecosuchians, supports a monophyletic Sebecosuchia. In both analyses, Pehuenchesuchus enderi was resolved as the sister taxon to all other sebecosuchians. A clear division of Sebecosuchia into Sebecidae and Baurusuchidae was not supported.

Regeneration mode affects spatial genetic structure of Nothofagus dombeyi forests.

Abstract: Disturbance may generate population bottlenecks by reducing population size and the number of founders establishing a new colony. We tested the hypothesis that the scale of disturbance affects the levels of genetic diversity and the spatial distribution of genotypes in naturally regenerating stands of Nothofagus dombeyi, an evergreen angiosperm tree, in northwestern Patagonia. At similar spatial scales, we predicted that old-growth stands characterized by fine-scale gap phase dynamics would be genetically diverse due to restricted gene flow among temporal and spatially isolated gaps. In contrast, young massively regenerated postfire cohorts resulting from coarse-scale disturbances would be genetically more homogeneous. At each of three paired old-growth and postfire stands a minimum of 50 trees were mapped and sampled within 1 ha. Fresh tissue was collected for isozyme analysis from a total of 361 trees along with tree cores and diameters. Tree age distributions reflected the dominant modes of regeneration. Six out of nine analysed loci were polymorphic. Mean genetic diversity parameters were greater but not significant in mature stands. Fixation indices suggested significant heterozygous deficit at two-thirds of possible tests indicating a Wahlund effect due to local recruitment of related seeds. F(ST) indicated moderate between-stand divergence. Mature stands concentrated half of positively like joins and yielded significant (P < 0.05) autocorrelation coefficients at small distance classes (< 20 m). Fine-scale patch dynamics within mature stands favours the maintenance of fine-scale genetic structure as a result of shade intolerance and local seed dispersal. Conversely, postfire stands suffer the effects of genetic drift given that a few reproductive trees produce a somewhat impoverished and genetically uniform progeny. Bottleneck effects will depend upon the density of remnant trees which could also be a function of the severity of fire.

Effects of fire severity in a north Patagonian subalpine forest

Abstract: Question: What is the relative importance of fire-induced canopy mortality, soil burning and post-fire herbivory on tree seedling performance? Location: Subalpine Nothofagus pumilio forests at Challhuaco valley (41°13'S, 71°19'W), Nahuel Huapi National Park, Argentina. Methods: We fenced and transplanted soils of three burning severities along a fire severity gradient produced by a fire in 1996. Over two growing seasons we monitored soil water, direct incoming solar radiation, seedling survival, final seedling total biomass and root/shoot ratio. Additionally, we assessed severity-related changes in soil properties. Results: Incoming radiation (an indicator of the amount of canopy cover left by the fire) was the primary factor influencing spring and summer top soil water availability, first and second-year seedling survival and seedling growth. While seedling survival and soil water content were negatively affected by increased radiation, seedling final biomass was highest in very open microsites. Burned soils showed lower water holding capacity and soil carbon; however these changes did not affect topsoil water, and, contrary to expectation, there was a slight tendency toward higher seedling survival on more heavily burned soils. Herbivory significantly reduced seedling survival, but only under high-radiation conditions. While the effect of radiation on final seedling biomass was not affected by herbivory, R/S ratios were significantly reduced by herbivory in high radiation microsites. Conclusions: Despite inducing faster aerial growth, increased radiation and herbivory in severely burned sites may effectively prevent post-fire regeneration in north Patagonian subalpine forest where seed sources are not limiting.

Dispersión de semillas por aves en un bosque templado de Sudamérica austral: ¿quién dispersa a quién?

Abstract: Seed dispersal by birds in a temperate forest of southern South America: Who disperses to whom? : Many plants depend on animals for seed dispersal, a task carried out mainly by birds that ingest fruits and defecate or regurgitate seeds undamaged. Unlike other temperate forest biomes, the Temperate Forest of Southern South America (TFSA) is characterized by a large proportion of woody plants (~ 60% of genera) producing fleshy fruits. We studied the interactions between plants and bird dispersers in a mesic forest dominated by Nothofagus dombeyi at the Llao-Llao Forest Reserve, Argentina (41∞00iS; 71∞ 30·W), close to the eastern boundary of the TFSA. We sampled birds using eight mist-nets and five sight/sound census stations during two consecutive fruiting seasons (1999 - 2000). We also recorded the phenology and fruit availability of six tree and shrub species. Gut content analysis was used to determine which fruits were consumed by the dispersers. Through the two sampling methods, we surveyed a total of 23 bird species occurring in the study area. We captured a total of 296 birds belonging to 12 species. We found evidence of fleshy fruit consumption only in two species, Elaenia albiceps and Turdus falcklandii, that consumed fruits and defecated seeds of eight from the nine fleshy-fruited plant species locally present. These two bird species were common in the forest during the fruiting season accounting for 52% and 9% of all mist-net captures and 35% and 4% of all sight/ sound censuses, respectively. Other birds consumed fruit or seeds (without dispersing them), insects, and/or small vertebrates. Phenological records indicated that most plant species bear

Parasitosis intestinales y su relacion con factores socioeconómicos y condiciones de habitat en niños de Neuquén, Patagonia, Argentina

Abstract: The prevalence and distribution of intestinal parasites (IP) were investigated in children from twopopulations of different socioeconomic level, located in the same area of the city of Neuquen, inorder to evaluate their relationship with habitat conditions and socioeconomic factors. Serial samplesof faeces and anal scraping of 126 children between 2 and 14 years from two sectors of the suburbanarea of Neuquen (Sector I and Sector II) were analyzed. Data concerning habitat conditions andsocioeconomic parameters were obtained by home visits and an observational structured survey.Presence of IP was detected in 50.7% of children from Sector I (suburban neighborhood with adequatesanitary conditions and middle or middle low socioeconomic level) and in 92.9% from children ofSector II (marginal settlement with poor sanitary conditions and low socioeconomic status). Sevenintestinal protozoan and 4 helminth species were identified.

Prenatal exposure to pesticides: analysis of human placental acetylcholinesterase, glutathione S-transferase and catalase as biomarkers of effect.

Abstract: Pre- and perinatal exposure to pesticides is deleterious on foetal and neonatal development, but information regarding possible effects on environmental low-dose exposure to pesticides is scarce. Most epidemiological studies of the health effect of pesticides have been based on self-reported information. However, detailed information on past pesticide use is difficult to reconstruct. This is a current study conducted among pregnant mothers attending a delivery care and perinatal programme at a public hospital. The study investigates biomarkers of early effects in placentas from women living in an area with an intensive use of pesticides in the northern part of Patagonia, province of Rio Negro, Argentina, and it assesses the consistency of the information provided by self-reports. The study confirms that placental acetylcholinesterase and catalase activities are significantly associated with periods of organophosphorus pesticides application, while glutathione S-transferase is not affected. We found a positive correlation between environmental exposure to organophosphorus pesticides and carbamate insecticides and newborn head circumference. The findings provide a further indication of a link between placenta acetylcholinesterase and catalase activity and prenatal exposure to pesticides in population studies. Both placenta enzymes may be used as biomarkers in health surveillance programmes for early diagnosis of exposure related alterations produced by organophosphorus pesticides and carbamate pesticides.

Biogeographical Consequences of Recent Climate Changes in the Southern Andes of Argentina

Abstract: Long-term trends of temperature variations across the Southern Andes (37–55°S) have been recently examined using a combination of instrumental and proxy records. Tree-ring based reconstructions indicate that the annual temperatures during the 20th century have been anomalously warm across the Southern Andes in the context of the past four centuries. The mean annual temperatures for northern and southern Patagonia during the interval 1900–1990 are 0.53°C and 0.86°C above the AD 1640–1899 means, respectively. Increased temperatures are seriously impacting the physical and biological systems across the Southern Andes.

Biochemical targets of xenobiotics: Biomarkers in amphibian ecotoxicology

Abstract: Biochemical biomarkers respond to a variety of environmental stresses, in particular to xenobiotic contamination. Their use in amphibian ecotoxicology has been scarce, and only in recent years have they been applied in a few cases of environmental monitoring. The best described biomarkers of xenobiotic effect in anurans are: the Cytochrome P450 enzymes which are induced in Phase I detoxification by a broad range of compounds; glutathione depletion and glutathione-S-Transferase induction by oxidative stress; vitellogenin induction by xenoestrogenic compounds causing feminization; acetylcholinesterase and carboxylesterase inactivation or inhibition by exposure to organophosphorus and carbamate compounds; and metallothioneins induced by exposure to toxic metals. As for other aquatic organisms, the integrated use of biochemical biomarkers seems the viable option for amphibian exposure and risk evaluations.

Conservation in Austral and Neotropical America: Building Scientific Capacity Equal to the Challenges

Abstract: JON PAUL RODRIGUEZ,∗ JAVIER A. SIMONETTI,† ANDREA PREMOLI,‡ AND MIGUEL ÂNGELO MARINI§ ∗Centro de Ecoloǵia, Instituto Venezolano de Investigaciones Cientificas, Apdo. 21827, Caracas 1020-A, Venezuela, and Provita, Apdo. 47552, Caracas 1041-A, Venezuela, email jonpaul@ivic.ve †Departamento de Ciencias Ecologicas, Facultad de Ciencias, Universidad De Chile, Casilla 653, Santiago, Chile ‡Laboratorio Ecotono, Universidad Nacional del Comahue—CRUB, 8400 Bariloche, Argentina §Departamento de Zoologia, IB, Universidade de Braśilia (UnB), 70.910–900, Braśilia, DF, Brazil

Simultaneous agronomic and molecular characterization of genotypes via the generalised procrustes analysis: an application to cucumber

Abstract: Characterizing entries in a germplasm bank by molecular markers and/or agronomic attributes is a common practice, but studies that simultaneously use molecular and agronomic traits are less frequent. Generalised Procrustes Analysis (GPA) was used to determine the relationships among 41 entries of cucumber (Cucumis sativus L.) via the simultaneous use of 16 agronomic traits (nine qualitative variables and seven quantitative variables) and 33 random amplified polymorphic DNA (RAPD) markers using a set of 11 primers. Other techniques like generalization of the simple matching coefficient, Gower's general similarity coefficient, and discretizing the quantitative variables were compared with GPA. The ordinations of cultivars using each trait individually did not fully characterize the cultivars. In fact, on the basis of the qualitative traits, only two groups were formed, with cultivars belonging to Beth-alpha and Dutch constituting a single group and the slice and gherkin types another group. The quantitative traits and also the molecular traits further separated the cultivars belonging Beth-alpha and Dutch types. The utilization of all variables together showed a greater discrimination power of genotypes. Four groups were defined which were consistent with Dutch, gherkin, slice, and Beth-alpha types. GPA was the most precise technique to cluster the entries. The final configuration was an average of the individual configurations. For other methods, those traits with more variants (but not necessarily more genetic information) had more influence on the final results. Besides, GPA allowed a deeper study of the relationships among relative ordinations of a same genotype under different types of descriptors to establish concordance between characterizations.

Sporidiobolus longiusculus sp. nov. and Sporobolomyces patagonicus sp. nov., novel yeasts of the Sporidiobolales isolated from aquatic environments in Patagonia, Argentina.

Abstract: During a survey of carotenogenic yeasts carried out in north-western Patagonia (Argentina), several ballistoconidia-producing strains belonging to the order Sporidiobolales were isolated from aquatic environments. Five strains were found to represent two novel species, for which the names Sporidiobolus longiusculus and Sporobolomyces patagonicus are proposed, with CBS 9654T (=PYCC 5818T=CRUB 1044T) and CBS 9657T (=PYCC 5817T=CRUB 1038T) as the type strains, respectively. The elongated basidia, which are five to six times longer that those of the remaining species of the genus Sporidiobolus, are a particular micromorphological feature of Sporidiobolus longiusculus. On the basis of the sequences of the D1/D2 domains of the 26S rRNA gene, the species most closely related to Sporidiobolus longiusculus is Sporobolomyces bannaensis, whereas Sporobolomyces marcillae is the closest relative of Sporobolomyces patagonicus. Complete internal transcribed spacer sequence analysis confirmed the separate position of Sporidiobolus longiusculus, whereas for Sporobolomyces patagonicus no nucleotide differences were found with respect to Sporidiobolus pararoseus CBS 491T. Negative mating experiments between strains of Sporobolomyces patagonicus and strains of Sporidiobolus pararoseus together with the low DNA–DNA reassociation values for the type strains of the two species validated the proposal of Sporobolomyces patagonicus as a distinct species. Information on additional Patagonian Sporobolomyces isolates is also included in this report.

Atomistic simulations of the effects of segregated elements on grain-boundary fracture in body-centered-cubic Fe

Abstract: We studied the detailed fracture behavior of a Σ=5 symmetrical-tilt grain boundary at low temperatures in Fe, using empirical interatomic potentials. For loadings just above the Griffith value, the crack propagates along the boundary for a distance of about 5 nm and then deflects toward the grains. When the boundary is loaded well above the Griffith criterion in pure bcc Fe, the crack deflects and propagates in an intragranular manner. Lattice trapping effects were observed in the initial stages, as the crack propagates along the grain boundary in a brittle manner with a periodicity given by the structural unit of the grain boundary. The effects of impurities on crack propagation along the grain boundary were simulated with various amounts of substitutional (Cr and Ni) and interstitial (H and C) impurities. The H impurities result in a strong embrittlement of the grain boundary, and no deflection of the fracture to the inside of the grains is observed. The element C has the opposite effect, inducing the deflection of the fracture to the interior of the grains from the beginning of the simulation. For the substitutional Ni and Cr impurities, the effects on grain-boundary fracture behavior are less dramatic, with Cr decreasing the resistance to grain-boundary fracture, if present in high concentrations. These effects agree with expectations based on the relative energies of segregation of the impurities to the grain boundary and free surface.

Breeding system of Tristerix corymbosus (Loranthaceae), a winter-flowering mistletoe from the southern Andes

Abstract: Harsh climates should select for breeding systems that uncouple reproductive success from unpredictable pollinator service, such as autonomous, within-flower pollination and autogamous seed set. I assessed the breeding system and overall pollinator dependence of Tristerix corymbosus (L.) Kuijt, a mistletoe that blooms during the snowy winters of the southern Andes and whose flowers are visited by the hummingbird Sephanoides sephaniodes. The nectar produced by T. corymbosus represents the main food for overwintering populations of S. sephanioides, one of the principal pollinators in the temperate forest of southern South America. Hand-pollination experiments showed that this plant is fully self-compatible, with only a slight advantage of cross- over self-pollen during either germination or early tube growth. Despite self-compatibility, T. corymbosus exhibited a limited capacity for autonomous, within-flower pollination and high dependence on its hummingbird pollinator for full seed set. Thus, dwindling hummingbird populations should compromise reproductive success in this potential keystone plant species.