Los carnívoros, por ser en mayor o menor grado predadores, son considerados muy frecuentemente especies conflictivas para el hombre. Este hecho trae aparejadas consecuencias importantes en relación a su manejo y conservación, principalmente en regiones alteradas, como lo es el pastizal pampeano de Argentina. El conocimiento de las densidades poblacionales resulta de fundamental importancia para el manejo de una especie y la estimación precisa de dichas densidades requiere del conocimiento de la organización social y espacial de la especie. Además, la evolución de la organización en los mamíferos y, en particular, en los cánidos, en donde se ha observado una gran plasticidad, es de interés teórico en sí misma. Sobre estas bases se planteó como objetivo para esta tesis aportar conocimientos sobre el comportamiento espacial del zorro gris pampeano, Pseudalopex gymnocercus, a través de la comparación entre dos áreas del pastizal con características distintas, en cuanto a la disponibilidad de recursos y actividades antrópicas. Se pretende, además, presentar información sobre su biología y plasticidad ecológica, que brinde soporte a planes de manejo y conservación de la especie y aporte al debate teórico sobre las relaciones entre la dispersión de los recursos y la organización social de los carnívoros de vida solitaria. Desde febrero 2001 a mayo 2007 se capturó y monitoreó, a través de radiocollares, una muestra de 26 individuos de dos poblaciones de zorro pampeano en el sud-oeste de la Provincia de Buenos Aires, una ubicada en el Parque Provincial E. Tornquist (PPET), área serrana protegida, con una alta densidad de caballos cimarrones, y la segunda, en un área cercana a la localidad de Aparicio (APA), con características netamente agrícola-ganaderas. Los animales fueron seguidos, en promedio, 198 días (rango: 1-406 días), utilizando para el análisis solamente aquellos animales que tuvieron más de 15 posiciones y que fueron seguidos por un período de al menos 3 meses. El tamaño promedio de área de acción (AC), estimado con el Mínimo Polígono Convexo al 100%, fue de 213,3±136,8 ha, con fuertes variaciones individuales para ambas áreas de estudio. PPET presentó una población de zorros pampeanos con AC de tamaños comparativamente pequeños. La variación individual en tamaño de las AC fue grande, pero no se evidenciaron diferencias entre machos y hembras ni variaciones importantes en la época de apareamiento. Los solapamientos de las AC entre sexos fueron amplios y se mantuvieron, por lo menos en algunas parejas, por más de una estación reproductiva. Se observó, también, una gran superposición entre las AC de dos hembras adultas, mientras que el solapamiento entre machos fue siempre escaso, independientemente del tamaño de las AC. Los datos indicarían que las excursiones representan una porción importante de las AC estimadas con todas las posiciones. Se observaron preferencias por ciertos hábitats, levemente más marcadas en la comparación entre la composición del área de estudio y la de las AC (selección de segundo orden), en la cual se registró selección negativa hacia los hábitats de sierra en altura, borde de ruta y cultivos y positiva hacia los restantes hábitats, principalmente borde de arroyo, seguido por sierra, bosque y clausura. Por otro lado, se observó la importancia del macro-hábitat cañadón, probablemente en relación a una mayor disponibilidad de alimentos y refugio. Los zorros pampeanos en PPET estuvieron, en general, muy poco activos en comparación con otras especies y con APA y si bien la mayor cantidad de registros fue durante la noche, también se observó actividad diurna, sin marcada estacionalidad. En APA la población de zorros observada presentó AC más grandes comparadas con PPET y menores excursiones. No hubo evidencias de que en las AC de las parejas macho-hembra, las cuales permanecerían juntas por más de una estación reproductiva, vivan otros individuos y se observó escaso solapamiento en las díadas intrasexuales. Se observaron diferencias en la selectividad entre los dos niveles de selección. Las AC presentaron una conformación en hábitat similar a la del área de estudio (selección de segundo orden débil), con preponderancia de áreas agrícola-ganaderas, pero se encontró una frecuencia de uso de cada hábitat muy selectiva (fuerte selección de tercer orden). Los hábitats principalmente elegidos fueron aquellos con cobertura vegetal más abundante y estable, como son borde de arroyo y fachinal. Los zorros de esta área mostraron un patrón netamente nocturno, probablemente influenciado por la actividad del hombre, y con una estacionalidad marcada. Los resultados obtenidos concuerdan con los esperados bajo la hipótesis de dispersión de recursos, y brindan evidencias concretas de la gran flexibilidad ecológica del zorro pampeano. Sin embargo, nuestros datos sugieren que los ambientes agrícolas ganaderos no ofrecen los recursos de alimento y refugio necesarios como para que las poblaciones mantengan una alta densidad; además, en estos mismos ambientes la presión de caza es mayor. La implementación de prácticas agrícolas-ganaderas que permitan un mayor desarrollo de estas áreas con cobertura vegetal permanente, sin perjuicio de los réditos económicos que surgen de esta actividad, contribuiría a mantener niveles poblacionales estables de la especie. Estas circunstancias conducen también a la necesidad de tener precaución en cuanto a la estimación de los niveles de extracción, ya que no se puede excluir que en ciertas condiciones los niveles poblacionales podrían caer por debajo de valores donde la población no pueda recuperarse. / Carnivores are very frequently considered conflicting species for men, to be in higher or lower grade predators. This fact brings important consequences related to its manage and conservation, mainly in altered regions, as it is pampas grassland of Argentina. The knowledge of the populational densities is fundamental for the species management, and the precise estimation of density requires the knowledge of social and spatial organization of the species. Furthermore, the evolution of the social organization in the mammals and particularly in the canidae, where a great plasticity has been observed, is a matter of theoretical interest by itself. On these bases, the objective proposed for this thesis is contribute to the knowledge on the spatial behavior of the pampas fox gray, Pseudalopex gymnocercus, through the comparison between two areas of grassland with different characteristic in relation to the availability of resources and antropic activities. Also, to present information about their biology and ecological plasticity to support conservation and managed plans of species and to contribute to the theoretical debate about relationships between the dispersion of the resources and the social organization of carnivores of solitary life. From February 2001 to May 2007 a sample of 26 individuals of two populations of pampas fox was captured and monitored, through radiocollars, in two study areas in the south-west of Buenos Aires Province. The first area was located in Tornquist Provincial Park (PPET), it was a protected mountain area, with a high density of wild horses; and the second area was near Aparicio town (APA), a highly crop and rangeland. Animals were followed, on the average, 198 days (range: 1-406 days), using for the analysis those animals that had more than 15 positions and that they were followed by a period of at least 3 months. The average size of home range with the Minimum Convex Polygon 100%, was 213.3±136.8, with strong individual variations for both study areas. PPET presented a population of pampas foxes with AC of small sizes comparatively t o APA .The individual variation in size of the AC was big, but differences were not evidenced between males and females neither important variations in the time of mating. The overlapping of the AC among sexes was wide and couples stayed together, at least in some cases, for more than a mating season. It was also observed, a great overlapping among the AC of two adult females, while the overlapping among males was always scarce, independently of the size of the AC. The data would indicate that trips represent an important portion of the AC (estimated with PMC 100%) without variation in the breeding season. Positive preferences were observed for certain habitats, in the comparison between the composition of the study area and that of the AC (selection of second order), in which negative selection was registered toward the height mountain habitats, route border and cultivations and positive toward the remaining habitat (stream border, mountain, wood patchy and enclose). On the other hand, the importance of the macro-habitat “cañadon” (small valleys between low canyons lands) was observed, probably in relation to a bigger availability of foods and shelters. The pampas foxes in PPET were, in general, not very active in comparison with other species and with foxes in APA, and although most of the registrations were during the night, day activity was also observed, without marked seasonality. Pampas foxes population in APA showed lower density compared to that in PEET, while the AC were bigger. Most of those AC seemed to be used by foxes (even 95 % of the positions) There was monogamous, with a couple that would remain together for more than a reproductive season but, without evidences of other individuals shearing the area with them, considering the scarce overlapping observed in the intrasexuales dyads. Differences were observed in the selectivity among the two selection levels. The composition of AC were similar to that of the study area (weak selection of second order), with preponderance of areas agricultural-cattlemen, but the frequency of use of each habitat was very selective (strong selection of third order). The mainly elected habitat were those with more abundant and more stable vegetable covering, like they are stream border and thick grassland. The foxes of this area showed a pattern highly nocturne, probably influenced by the man's activity, and with a marked seasonality. The results obtained in this thesis, agree with the ideas under the dispersion resources hypothesis, and they offer concrete evidences of the great ecological flexibility of the pampas fox. However, our data suggest that the landscape agricultural-cattlemen don not offer the availability of food and refuge necessary for maintain a populations in a high density; also, in these same landscape the hunt pressure is bigger. The implementation of crop-rangeland practices that allow bigger development of these areas with permanent vegetable covering, without damage of the economic interests that arise of this activity, would contribute to maintain stable populational levels of the species. These circumstances also lead to the necessity of having caution for the estimation of extraction levels, since it cannot exclude that under certain conditions the populational levels could fall below values where the population cannot recover.

La estructura de la tesis se dividió en dos secciones introductorias en las que se plasmaron los antecedentes, objetivos y una amplia descripción del área de estudio y cinco capítulos en los que se analizaron distintos enfoques sobre los ambientes lagunares del sistema, sus comunidades ícticas y aspectos diversos de los estados poblacionales de las especies de peces más abundantes. En el Capítulo 1 se caracterizaron física y químicamente cada una de las lagunas, develando la gran variabilidad existente entre los cuerpos de agua y confirmando el fuerte gradiente creciente de conductividad en sentido NE–SO, ya descripto por la bibliografía. Este resultó ser uno de los parámetros más influyentes para determinar la presencia de los diferentes taxones ícticos, lo que se abordó en el Capítulo 2. En este segundo capítulo, también se actualizó la distribución de las especies de peces y se presentó la estructura de cada comunidad y sus dinámicas estacionales. Entre los registros obtenidos, se destaca la cita de dos nuevas especies para el sistema de las lagunas Encadenadas del Oeste, ambas en laguna Alsina, el bagre cantor Pimelodella laticeps y la vieja de agua Hypostomus commersoni y la expansión de dos especies ya citadas para alguna de las lagunas: la carpa Cyprinus carpio y la madrecita, Jenynsia multidentata. En total se capturaron 44892 peces. Se registraron catorce (14) especies, pertenecientes a ocho (8) familias y cinco (5) órdenes. El Orden Characiformes fue el más representado, con 47,6% y le siguieron Siluriformes con 28,6% y Cyprinodontiformes con 9,5%. Los Ordenes Cypriniformes, Atheriniformes y Perciformes sólo estuvieron representados por una especie cada uno (4,8%). En la laguna Epecuén no se capturaron peces durante el año de estudio. El amplio dominio de pejerrey (Odontesthes bonariensis) en las lagunas centrales del sistema (Cochicó, del Monte y del Venado) se mantuvo constante a lo largo del año, con abundancia relativa siempre superior a 97,6% (en número) y 98,5% (en peso), en ambientes de aguas abiertas. Sin lugar a dudas, en estos tres cuerpos lagunares, la mayor concentración de sales y la pérdida de hábitats, como consecuencia de la continua bajante del nivel de agua, son los factores principales que han actuado en la disminución de la diversidad íctica, convirtiendo a estas lagunas en ambientes prácticamente monoespecíficos. En la laguna Alsina se observó un cambio significativo de la estructura comunitaria, explicado principalmente por una mortandad masiva de peces, originada por bajas temperaturas en julio de 2007. La mortandad masiva provocó la desaparición total de bagarito Parapimelodus valenciennis, especie muy sensible a las bajas temperaturas y afectó, en menor medida, a dientudo Oligosarcus jenynsii, sabalito Ciphocharax voga y bagre sapo Rhamdia quelen. El Capítulo 3 estuvo dirigido al análisis de los parámetros biológicos poblacionales de las especies más abundantes del sistema, pejerrey y dientudo. Las estructuras de tallas capturadas permitieron discriminar entre poblaciones de pejerrey dominadas por ejemplares de tallas pequeñas, tales como las de las lagunas del Venado, del Monte y Alsina, de aquellas dominadas por ejemplares de talla media a grande como las de laguna Cochicó. Tanto en pejerrey como en dientudo, las tallas medias de las hembras fueron significativamente mayores a las de machos. Las poblaciones de pejerrey de las lagunas del Venado y del Monte presentaron un predominio de hembras, mientras que en las lagunas Cochicó y Alsina, ambos sexos presentaron una relación de equilibrio. Sin embargo, en todas las lagunas se observó el uso diferencial del ambiente por parte de los sexos durante el período reproductivo, con predominio de hembras en lugares de aguas abiertas y mayoría de machos en los sectores costeros. A través de las proporciones de estadios gonadales y de los valores de índice gonadosomático (IGS), por estación, se determinó que el período reproductivo se limitó a la primavera. Para dientudo, la relación hembra-macho presentó un estado de equilibrio en Cochicó y dominio de hembras en Alsina. Los resultados de la relación longitud-peso evidenciaron un mayor factor de crecimiento en las etapas tempranas de los ejemplares de pejerrey de la laguna Cochicó, en comparación a los de laguna Alsina y los de las lagunas del Venado y del Monte, explicando en gran parte las diferencias en las Lt50 estimadas para cada una de las poblaciones (Lt50 de Cochicó > Alsina > del Monte = del Venado). Mientras que en los pejerreyes adultos generalmente el coeficiente b de los machos fue mayor o igual al de las hembras. En dientudo, la relación longitud-peso no presentó diferencias entre sexos pero sí entre las estaciones. El estado actual de los individuos de pejerrey y dientudo, evaluado a través de índices biométricos, presentó signos de una buena condición actual y pasada para el crecimiento y desarrollo. En el Capítulo 4, el esfuerzo se centró en el estudio de la alimentación del pejerrey, principal especie del sistema por ser la más abundante, en número y biomasa, y la de mayor importancia económica. Se analizaron los contenidos estomacales de 423 ejemplares entre los cuatro ambientes del sistema, que cubrieron un amplio rango de tallas, entre 93 y 585 mm de longitud total. Ninguna población de pejerrey presentó restricciones alimenticias. El menor índice de vacuidad se obtuvo en invierno (1,93%) y el mayor para el verano (23,85%). Los microcrustáceos, especialmente copépodos y cladóceros, constituyeron el principal tipo de alimento del pejerrey de las lagunas Encadenadas del Oeste. Los copépodos fueron el componente principal de la dieta de pejerrey en las lagunas del Venado y del Monte, mientras que los cladóceros fueron el alimento dominante en las lagunas Cochicó y Alsina, en términos de importancia relativa. En total se distinguieron 80 ítems alimenticios en la dieta del pejerrey, de ellos la gran mayoría se clasificaron como presas ocasionales o de complemento. Al analizar, la dieta de pejerrey por clase de tallas se observó que los microcrustácos fueron el componente dietario principal, con valores de %IRI siempre superiores a 91,3% en las clases de tallas I, II y III y superior al 69% en la clase de talla IV (ejemplares con longitud total mayor a 299 mm). Por último, en el Capítulo 5 se analizó la situación actual de cada población de pejerrey, desde el punto de vista del aprovechamiento pesquero. Se evaluaron las diferentes medidas de manejo aplicadas y los resultados obtenidos, prestando mayor atención en la situación de la laguna Cochicó, por ser un ambiente con fuerte desarrollo pesquero actual y se elaboraron consignas tendientes a optimizar el uso sostenible del recurso pejerrey, en relación a las características de cada una de las lagunas del sistema Encadenadas del Oeste. / The structure of the thesis is divided into two introductory sections in which we present the background, objectives, and a comprehensive description of the area of study; and five chapters in which we analyze different approaches to the lagoon environments of the system, their fish communities and the diverse population aspects of the most abundant fish species. In Chapter 1, each lagoon is physically and chemically characterized, revealing the great variability existing between bodies of water, and confirming the strong rising gradient of conductivity towards NE-SW already described in the bibliography. This proved to be one of the most influential parameters to determine the presence of different fish taxons, which are dealt with in Chapter 2. In this second chapter, the distribution of fish species is also updated and the structure of each community and their seasonal dynamics are presented. Among the records obtained, there are two facts that stand out: the appearance of two new species in the Encadenadas del Oeste system -the „bagre cantor‟ Pimelodella laticeps and „vieja del agua‟ Hypostomus commersoni-, both in Alsina lagoon; and the expansion of two species already cited for any of the lagoons: „carpa común‟ (common carp) Cyprinus carpio and the „madrecita‟ (onesided livebearer) Jenynsia multidentata. Forty-four thousand eight hundred and ninety-two (44892) fish were captured in total. There were fourteen (14) species belonging to eight (8) families and five (5) orders. The Characiformes order was the most represented with 47.6%, followed by the Siluriformes with 28.6%, and the Cyprinodontiformes with 9.5%. The Cypriniformes, Atheriniformes, and Perciformes orders were only represented by one species each one (4.8%). In Epecuén lagoon there were no fish captured during the year of study. The broad domain of silverside (Odontesthes bonariensis) in the central lagoons of the system (Cochicó, del Monte, and del Venado) remained constant throughout the year, with relatively abundance, always above 97.6% (in number) and 98.5% (in weight), in open water environments. Undoubtedly, the main factors that have been involved in the decrease of the fish biodiversity -making these lagoons into practically monospecific environments- are the large salt concentration and habitat loss, as a consequence of the continuous decrease of the water level. In Alsina lagoon there was a significant change in the community structure, explained mainly by a massive fish mortality caused by the low temperatures in July 2007. The massive mortality led to the complete disappearance of the „bagarito‟ Parapimelodus valenciennis -a species very sensitive to low temperatures- and affected, to a lesser extent, the „dientudo‟ Oligosarcus jenynsii, the „sabalito‟ Ciphocharax voga and the „bagre sapo‟ Rhamdia quelen. Chapter 3 is directed to the analysis of biological population parameters of the most abundant species of the system, silverside and „dientudo‟. The size structures in the captured specimens allowed us to differentiate between silverside populations dominated by specimens of small size -such as in del Venado, del Monte and Alsina lagoons- from those dominated by specimens of medium to large size -as in Cochicó lagoon. Both in silverside and „dientudo‟, the average size was significantly larger in females than in males. The silverside population in del Venado and del Monte lagoons presented a predominance of females; whereas in Cochicó and Alsina lagoons, both sexes presented a balanced proportion. However, in all the environments, a differential use of the environment on the part of the sexes was observed during the reproductive period, with a predominance of females in places of open water and most males in the coastal areas. We determined, through the proportions of gonadal stadiums and gonadosomatic index values (GSI), per season, that the reproductive period was limited to the spring. For the „dientudo‟, the female-male relationship presented a balanced proportion in Cochicó, and a predominance of females in Alsina. The results of the length-weight relation showed a greater growth factor in the early stages of the silverside individuals in Cochicó lagoon, in comparison to Alsina lagoon and del Venado and del Monte lagoons, explaining to a large extent the differences in the Tl50 estimated for each of the populations (Tl50 Cochicó > Alsina > del Monte = del Venado). While, generally, in adult silversides, b coefficient in males was higher than or equal to that in females. In the case of „dientudo‟, length-weight relation did not represent differences between sexes, but it did among seasons. The current status of silverside and „dientudo‟ individuals, evaluated through biometric indexes, presented signs of good current and past conditions for growth and development. In Chapter 4, the effort is focused on the study of the silverside diet -the main species of the system for being the most abundant in number and biomass, and the most important in economic terms. We analyzed the stomach contents of four hundred and twenty-three (423) specimens of the four (4) environments of the system, which covered a wide range of sizes, from ninety-three (93) to five hundred and eighty-five (585) mm long. None of the silverside populations presented food restrictions. The lowest rate of emptiness was obtained in winter (1.93%) and the largest, in summer (23.85%). Microcrustacean, especially copepoda and cladocera, were the main type of food of the silverside of the Encadenadas del Oeste lagoons. Copepoda were the main component of the silverside diet in del Venado and del Monte lagoons, while cladocera were the dominant food kind in Cochicó and Alsina, in terms of relative importance. Eighty food items in the silverside diet were distinguished in total, in most of the cases they were classified as occasional or complementary preys. When analyzing the diet of silversides for sixe class, we observed that microcrustacean were the main diet component in size groups I, II and III, with %IRI values superior to 91,3%, and values superior to 69,0% in size group IV. Finally, in Chapter 5, we analyzed the current situation of each silverside population as fishery resources. We assessed the various management measures applied and the results obtained, paying more attention to the situation of Cochicó lagoon, for being an environment with strong current fishery development; and we elaborated instructions to optimize the sustainable use of the silverside resource, in relation to the characteristics of each lagoon in the Encadenadas del Oeste lagoon system.

Los agroecosistemas son áreas disturbadas que se encuentran pobladas por una fauna numerosa de artrópodos. Entre éstos, las arañas se encuentran entre los depredadores dominantes de insectos en los ecosistemas terrestres, siendo un grupo útil como enemigos naturales de insectos plaga. Dentro de este contexto, conocer la fauna de artrópodos que habita dichos ambientes es de suma importancia para la gestión y manejo de los ecosistemas agrícolas. El objetivo general de la presente tesis fue estudiar la entomofauna y araneofauna realizando una descripción de la composición de las mismas y analizando la distribución de la abundancia de dichos artrópodos en el gradiente cultivo-borde y a lo largo del desarrollo fenológico de cultivos de avena y trigo. A su vez, se analizó la interacción araña-presa por medio de observación directa a campo y en laboratorio de las especies dominantes en los cultivos mencionados. En general, la composición, riqueza de órdenes y abundancia fue similar en ambos cultivos. Los órdenes más abundantes fueron Diptera, Collembola e Hymenoptera. En el estrato suelo no se registró un efecto marcado debido al gradiente cultivo-borde, aunque se detectó una leve tendencia a disminuir la abundancia de los artrópodos en los bordes de los cultivos. A su vez se encontró un incremento en la abundancia a medida que los cultivos se desarrollaban hasta un máximo en las últimas etapas fenológicas de los mismos. En el estrato herbáceo se hallaron diferencias significativas entre los sitios en el cultivo de avena, siendo la abundancia significativamente mayor fuera de los cultivos que dentro de los mismos, observándose la tendencia opuesta en trigo. Thomisidae, Anyphaenidae, Lycosidae, Linyphiidae y Araneidae fueron las familias de arañas dominantes. Se encontraron nueve gremios funcionales siendo errantes de suelo y cazadoras por emboscada los más abundantes. Se registró una abundancia y riqueza específica similar y una alta diversidad en ambos cultivos. Lycosidae y Linyphiidae fueron las familias dominantes en el estrato suelo. Se observó una distribución similar en cuanto a la abundancia de las arañas a lo largo del gradiente cultivo-borde disminuyendo ligeramente fuera de los cultivos. A su vez se halló una abundancia significativamente mayor en las últimas etapas fenológicas de los cultivos. Las dos especies más abundantes en suelo en ambos cultivos fueron Ostearius melanopygius (Linyphiidae) y Lycosa poliostoma (Lycosidae), siendo ambas potenciales especies agrobiontes de los cultivos de avena y trigo del sudoeste de Buenos Aires. En el estrato herbáceo las familias más abundantes fueron Araneidae, Thomisidae y Anyphaenidae. En cuanto al gradiente cultivo-borde no se hallaron diferencias significativas en la abundancia de arañas entre los sitios en ninguno de los dos cultivos. Las especies dominantes en este estrato para ambos cultivos fueron Lepthyphantes sp. (Linyphiidae) y Misumenops pallidus (Thomisidae). Esta última especie es un habitante común de los agroecosistemas del centro de Argentina. La dieta de Latrodectus mirabilis (Theridiidae) fue casi exclusivamente insectívora siendo sus principales presas las hormigas. Se encontró una respuesta funcional de tipo II de la viuda negra (Latrodectus mirabilis) frente a las hormigas negras (Acromyrmex lundii). Los resultados obtenidos indican que esta especie tiene potencial como agente de control biológico de la hormiga negra. En cuanto a las experiencias realizadas entre hembras de Lycosa poliostoma se observó un incremento en la ocurrencia de canibalismo entre arañas que se encontraban en ayuno en comparación con arañas bien alimentadas, indicando un efecto del nivel de hambre sobre el mismo. A su vez se detectó una fuerte influencia de la territorialidad sobre el grado de canibalismo en esta especie. / Agroecosystems are disturbed areas that are inhabited by a large arthropod fauna. Among these, spiders are one of the most dominant insect predators in terrestrial ecosystems, being a useful group as natural enemies of pest. In this context, the knowledge of the arthropod fauna that inhabiting these habitats is critical to the management and handling of agricultural ecosystems. The main goal of this thesis was to study the entomofauna and araneofauna of oat and wheat crops focusing in the taxonomic composition and the distribution of the abundance in crop-edge gradient and along the phenological development. Moreover, spider-prey interaction was analyzed through direct observation at field and laboratory experiences considering the dominant species in these crops. In general, the composition, orders richness and abundance were similar in both crops. Diptera, Collembola and Hymenoptera were the most dominant orders. At ground level, an effect due to crop-edge gradient was not recorded, although the abundance of arthropods had a slight tendency to decrease at crop´s edge. Indeed, an increase in the abundance of arthropods was observed in the last phenological stages of the crops. At herbaceous level, a significant difference among sites in oat crop was found, being the abundance significantly greater in the edge of the crop. The opposite trend was observed in wheat. The dominant families of spiders were Thomisidae, Anyphaenidae, Lycosidae, Linyphiidae and Araneidae. Nine functional guilds were found, being ground runners and ambushers the most abundant. In both crops, the abundance and species richness were similar and a high diversity was found. Lycosidae and Linyphiidae were the most dominant families at ground level. A similar distribution of the spider´s abundances throughout the crop-edge gradient was found, decreasing slightly out of crops. Besides, a significantly higher abundance was found in the last phenological stages of crops. Ostearius melanopygius (Linyphiidae) and Lycosa poliostoma (Lycosidae) were the most abundant species at ground level. Both species are potential agrobiont spiders of oat and wheat in South of Buenos Aires Province. At herbaceous level, the most dominant families were Araneidae, Thomisidae and Anyphaenidae. In crop-edge gradient, no significant differences were found in the abundance of spiders among sites. The dominant species for both crops were Lepthyphantes sp. (Linyphiidae) and Misumenops pallidus (Thomisidae). This last species is a common inhabitant of agroecosystems of Central Argentina. The diet of Latrodectus mirabilis (Theridiidae) was almost insectivorous, being ants the most common prey. A functional response type II was found in black widow (Latrodectus mirabilis)-black ants (Acromyrmex lundii) interactions. The results obtained indicate that this spider species has a potential as biological control agent of black ants. The experiences among females of Lycosa poliostoma showed an increased of cannibalism cases among hunger spiders, indicating that the hunger level of spiders has an important effect upon cannibalism. Further, a strong influence of territoriality upon the degree of cannibalism was detected.

Argentina se ha consolidado como uno de los principales países productores y exportadores de miel; internacionalmente reconocido por el volumen y calidad de su producción. En el sudoeste de la provincia de Buenos Aires se ha formado la Cooperativa Apícola Pampero que junto con la Cámara de Apicultores Pampero (ambas se denominan CAP) buscan el crecimiento y desarrollo de la actividad apícola en la región de forma sustentable. Es así que resulta de sumo interés para la CAP, contar con una herramienta de análisis que permita el estudio de la cadena de valor apícola, con la cual realizar sugerencias que optimicen el resultado del proceso productivo. En este sentido, el objetivo de la presente tesis es proporcionar un estudio preliminar de la cadena de la Cadena Apícola del Sudoeste de la Provincia de Buenos Aires, a partir de analizar el escenario de estado estacionario en un período determinado del negocio, que coincide con un ciclo completo del mismo. Para llevar a cabo el estudio de la Cadena Apícola, se utiliza un enfoque de Programación Lineal; para el cual se hace uso de tecnologías modernas de modelamiento y optimización, como los es el software General Algebraic Modelling Systems (GAMS). De modo que la presente tesis consiste en el desarrollo e implementación computacional de un modelo matemático que permite evaluar las decisiones de una empresa inmersa en la cadena de valor apícola, para optimizar el uso de los recursos y los costos y beneficios, en ambientes de gran incertidumbre y variabilidad económica como son los reales. Los resultados del caso de estudio, apuntan a sugerir que los productores coloquen todas las colmenas a polinizar únicamente en cultivos del valle y a producir núcleos, polen y miel. / Argentina has become one of the leading producers and exporters of honey countries; internationally recognized for the volume and quality of production. In the southwest of the province of Buenos Aires it has formed the Cooperativa de Trabajo Apícola Pamperotogether with the Cámara de Apicultores Pamepero (both named CAP) seeking growth and development of beekeeping in the region in a sustainable way. Thus it is of great interest to the CAP, have an analysis tool that allows the study of beekeeping value chain, with which to make suggestions to optimize the result of the production process. In this sense, the objective of this thesis is to provide a preliminary study of the chain of Beekeeping Chain of the Southwest of the Province of Buenos Aires, from analyzing the scenario of steady state in a given period of business, which coincides with a complete cycle of the same. To carry out the study of the Beekeeping Chain, linear programming approach is used; for which use of modern technologies of modeling and optimization is done, as is the software General Algebraic Modeling Systems (GAMS). So this thesis is the development and computational implementation of a mathematical model to evaluate the decisions of a company undergoing beekeeping value chain, to optimize the use of resources and the costs and benefits large environments economic uncertainty and variability are as real. The results of the case study, point to suggest that producers put all hives to pollinate crops only in the valley and produce cores, pollen and honey.

La intensificación en la cría de animales estabulados ha generado que localmente se reciclen cada vez menos nutrientes y que se concentren residuos y excretas en fincas y regiones cada vez más especializadas, mientras que los suelos agrícolas se empobrecen cada vez más porque no se reponen en su totalidad los nutrientes extraídos por las cosechas. Como una alternativa a esta problemática, se presenta el reciclado de nutrientes de abonos orgánicos para el cultivo de la cebolla. El objetivo de la presente tesis es optimizar las dosis de aplicación de diversas enmiendas y abonos utilizados en un cultivo ecológico de cebolla (Allium cepa L.), mediante el estudio de la mineralización del N y del P orgánico. Para ello: (1) se midió la capacidad de liberar N de un suelo fertilizado con siete abonos orgánicos aplicados a razón de 350 kg N ha-1 en condiciones ideales de laboratorio, (2) se cuantificó el efecto del tipo de suelo en la mineralización de tres enmiendas orgánicas en condiciones de laboratorio, (3) se realizaron ensayos in-situ para estudiar la cinética de mineralización de N y P de siete abonos orgánicos en condiciones de campo, (4) se realizó un ensayo de crecimiento vegetal de la cebolla INTA Valcatorce y se estudiaron las curvas y las tasas de absorción de macro y micro nutrientes (5) se realizó un ensayo de fertilización en campo donde se evaluaron 5 abonos orgánicos en 4 dosis distintas y se midió la evolución y el rendimiento del cultivo. Se comprobó que los abonos orgánicos presentan diferentes dinámicas de mineralización y que la mayoría presentan periodos cortos de inmovilización de N en las primeras semanas de incubación. La mayor disponibilidad de N inorgánico la presentó el suelo abonado con BioOrganutsa seguido por Estiércol Ovino, Equino, Gallinaza, Bovino y Lombricompuesto, Por lo que es necesario considerar estas diferencias para realizar una correcta sincronización de la absorción del cultivo y de las fechas de fertilización. Los suelos abonados presentaron mayor disponibilidad de P que los requerimientos de la cebolla, sin embargo se presentaron dos dinámicas de Pe durante la incubación: BioOrganutsa, Gallinaza y E. Ovino presentaron una alta disponibilidad P que se mantuvo estable durante la incubación, mientras que la gallinaza compostada, Lombricompuesto, el E. Equino y E. Bovino mostraron incrementos en Pe durante la incubación. Al estudiar el crecimiento y la acumulación de nutrientes de la cebolla se encontró que las tasas de absorción de los 12 minerales estudiados presentan picos máximos entre el día 70-89 después de trasplante, durante la etapa de crecimiento exponencial del cultivo. Mediante fertilización con abonos orgánicos se encontró rendimientos similares a los fertilizantes convencionales y la respuesta de la cebolla a la adición de BioO, GC, EB y G se ajustó a la ecuación y = -0.76x2 + 279.5x + 19.353, con un R2 de 0.99. En promedio estos tratamientos presentaron rendimientos máximos a dosis equivalentes de 184 kg N, mientras que la adición de EO presentó incrementos en la dosis de 75 kg N y posteriormente decreció a niveles similares o inferiores a los del testigo. / The intensification of animal husbandry has generated less local recycling of nutrients and increased concentration of waste and excreta on farms and specialized regions, while the agricultural soils are becoming poorer because not all the nutrients removed by crops are replaced. As an alternative to this problem, the nutrient recycling in organic fertilizers for onion crops is presented. The aim of this dissertation is to optimize the application of various organic amendments and fertilizers used in ecological cultivation of onion (Allium cepa L.), by studying the mineralization of organic N and P. To do this: (1) The ability of soil fertilized with seven organic fertilizers applied at a rate of 350 kg N ha-1 under ideal laboratory conditions was quantified, (2) the effect of soil type in the mineralization of three organic amendments under laboratory conditions was measured, (3) in an in-situ mineralization experiment the availability kinetics of N and P of seven organic fertilizers under field conditions was studied, (4) a plant growth experiment was carried out for the onion INTA Valcatorce, where curves and rates of absorption of macro and micro nutrients were studied, (5) An essay of organic fertilization of onion was performed with 5 organic manures in 4 different rates. Crop evolution and yield was measured. It was found that organic fertilizers have different dynamics of mineralization and most have short periods of immobilization of N in the first weeks of incubation. Greater availability of inorganic N was presented in soil fertilized with BioOrganutsa followed by sheep, horse, poultry, feedlot manure, and vermicompost. It is necessary to consider these differences for proper synchronization of crop uptake and fertilization dates. Manured soils had a higher availability of P than required for the onion crop, however two dynamics of extractable P occurred during incubation: BioOrganutsa, poultry and sheep manure presented high availability of P which remained stable during incubation, while the composted chicken manure, vermicompost, feedlot and horse manure showed increases in extractable P during incubation. In examining the growth and accumulation of nutrients in the onion plant, it was found that absorption rates of the 12 minerals studied showed peaks between days 70-80 after transplant, during the exponential growth stage of the crop. By fertilization with organic fertilizers it is possible to achieve similar yields to conventional fertilizers. The onion response to the addition BioOrganutsa, composted poultry, Feedlot and poultry manure was adjusted to the equation y=-0.76x2+279.5x+19.353, with R2 0.99. These treatments presented average maximum yields at equivalent doses of 184 kg N. Meanwhile the addition of sheep manure increased yield at the dose of 75 kg N and then decreased to levels lower or similar to the control with higher doses.

O presente trabalho tem como objetivo analisar, comparativamente, as políticas de atração, as atividades, os fluxos e deslocamentos dos imigrantes no Brasil e Argentina, focalizando mais especificamente as regiões de São Paulo e Buenos Aires, no período de 1870 a 1930. Procuramos, para os dois países e regiões, identificar as semelhanças e diferenças nas políticas implementadas visando a atração de imigrantes, observar o comportamento dos fluxos migratórios e examinar o papel dos imigrantes na composição das populações e a sua atuação em atividades econômicas nos meios rural e urbano. Examinamos também o fluxo de imigrantes entre o porto de Santos e o porto de Buenos Aires no período, analisando números e origem dos emigrantes assim como as motivações aventadas nas fontes e pela historiografia. As informações e dados compilados para a confecção deste trabalho foram coletados de diversos tipos de fontes: fontes governamentais, legislações, censos, relatório, estatísticas. Os arquivos consultados correspondem a acervos físicos e online. O trabalho está dividido em três capítulos. As fontes revelaram diferenças e semelhanças entre os processos migratórios para Brasil e Argentina. Durante todo o século XIX, tanto no Brasil quanto na Argentina, a necessidade de povoar territórios e encontrar mão de obra para sustentar o desenvolvimento da agricultura agroexportadora norteou os debates governamentais sobre o fomento da imigração. Além de ser uma solução para a falta de braços nas lavouras e para o povoamento de territórios, nos dois países a imigração era vista como o caminho para o progresso, para a modernização da sociedade e para o branqueamento da população. A partir de 1870 até 1930, período das grandes migrações, Brasil e Argentina foram os países que mais receberam imigrantes na América Latina. O Brasil recebeu mais 4,1 milhões de imigrantes e mais de 6,2 milhões se dirigiram para a Argentina. Nesse período, a política de subsídios, custeando as passagens transatlânticas, hospedagem e colocação nas fazendas de café, foi implantada com sucesso no estado de São Paulo. Na Argentina, houve o predomínio da imigração espontânea. As políticas liberais e os altos salários pagos nas épocas de colheitas do trigo e milho também tiveram êxito em atrair estrangeiros. As fontes revelaram também uma mobilidade geográfica e deslocamentos frequentes e de caráter sazonal dos imigrantes entre São Paulo e Buenos Aires. / The present work aims to analyze, comparatively, the policies for attraction, the activities, the flows and displacement of immigrants in Brazil and Argentina, specifically focusing on the regions of São Paulo and Buenos Aires from 1870 to 1930. We intend to identify, for both countries and regions, the similarities and differences of the implemented policies aimed to attract immigrants; to observe the pattern of the migration flows; and to examine the role of immigrants in the composition of these populations and their role within the economic activities at the rural and urban environments. We also examine the immigrants flow between the ports of Santos and Buenos Aires at the time, analyzing the numbers and place of origin of the immigrants, as well as their motivations, reported by the sources and the historiography. The information and data compiled to produce this study were collected from a variety of research sources: government data, laws, censuses, report statistics, among others. The archives consulted correspond to physical and online collections. This work is divided in three chapters. The sources revealed differences and resemblances between the migratory process to Brazil and Argentina. Throughout the nineteenth century, both in Brazil and Argentina, the governmental debates about the promotion of immigration were guided by the need of populating territories and finding labor to sustain the agro-export agriculture development. In addition to being a solution for the lack of work force on the lands and for the settlement of territories, in both countries the immigration was seen as the pathway to progress, society modernization and population whitening. From 1870 to 1930, considered the period with the higher occurrence of migration, Brazil and Argentina were the countries that received the largest amount of immigrants in Latin America. Brazil received more than 4.1 million of immigrants, while more than 6.2 million went to Argentina. In the period, the subsidy policy, financing the transatlantic travels, accommodation and location in the coffee farms, succeeded in São Paulo state. In Argentina, the spontaneous immigration prevailed. The liberal policies for immigrant attraction and the high weights paid on the wheat and maize harvest seasons also succeeded in attracting foreigners. Sources also revealed a geographic mobility and frequent displacements with a seasonal character by immigrants between São Paulo and Buenos Aires.

Refletindo sobre a idéia do espaço como elemento que ativa experiências e gera visualidades, este projeto caminha rumo à especificidade do lugar e adiciona um terceiro elemento, a ficção, ao perguntar: pode uma obra literária relativa ao lugar transformar-se em poética visual? O desenvolvimento desta questão propiciará reflexões na interface literatura, cinema, e artes visuais, além do entendimento e da experiência do espaço proposto, onde lugar físico e lugar ficcional sejam igualmente princípios ativadores do processo de criação de trabalhos audiovisuais. No aprofundamento do universo de autores como Jorge Luis Borges(1899-1986) e Marguerite Duras(1914-1996), esta pesquisa se dirige, através de uma práxis reflexiva, a um sentido inverso do encontrado no universo literário: na procura dos lugares reais a partir dos ficcionais, na constatação de uma memória construída a partir de um repertório relacionado a lugar, e nas possibilidades de transposição, transformação e permeabilidade dos discursos literário e visual. / Reflecting on the idea of space as an element that activates experiences and generates visuality, this project moves towards specificity of place and adds a third element, fiction, in order to ask: can a literary work about place turn into visual poetic? The development of this issue will provide reflections on literature, film and visual arts interface, beyond understanding and experience of the proposed space, where physical and fictional place activates, at the same time, the creation of audiovisual work. In deepening of the universe of authors such as Jorge Luis Borges (1899-1986) and Marguerite Duras (1914-1996), this research is directed through a reflective practice, to the reverse of that found in the literary universe: in search of the real places that comes from fictional, on finding a memory constructed from a repertoire connected to the idea of place, and on the possibilities of transposition, processing and permeability of visual and literary speech .

O presente trabalho tem como objetivo analisar, comparativamente, as políticas de atração, as atividades, os fluxos e deslocamentos dos imigrantes no Brasil e Argentina, focalizando mais especificamente as regiões de São Paulo e Buenos Aires, no período de 1870 a 1930. Procuramos, para os dois países e regiões, identificar as semelhanças e diferenças nas políticas implementadas visando a atração de imigrantes, observar o comportamento dos fluxos migratórios e examinar o papel dos imigrantes na composição das populações e a sua atuação em atividades econômicas nos meios rural e urbano. Examinamos também o fluxo de imigrantes entre o porto de Santos e o porto de Buenos Aires no período, analisando números e origem dos emigrantes assim como as motivações aventadas nas fontes e pela historiografia. As informações e dados compilados para a confecção deste trabalho foram coletados de diversos tipos de fontes: fontes governamentais, legislações, censos, relatório, estatísticas. Os arquivos consultados correspondem a acervos físicos e online. O trabalho está dividido em três capítulos. As fontes revelaram diferenças e semelhanças entre os processos migratórios para Brasil e Argentina. Durante todo o século XIX, tanto no Brasil quanto na Argentina, a necessidade de povoar territórios e encontrar mão de obra para sustentar o desenvolvimento da agricultura agroexportadora norteou os debates governamentais sobre o fomento da imigração. Além de ser uma solução para a falta de braços nas lavouras e para o povoamento de territórios, nos dois países a imigração era vista como o caminho para o progresso, para a modernização da sociedade e para o branqueamento da população. A partir de 1870 até 1930, período das grandes migrações, Brasil e Argentina foram os países que mais receberam imigrantes na América Latina. O Brasil recebeu mais 4,1 milhões de imigrantes e mais de 6,2 milhões se dirigiram para a Argentina. Nesse período, a política de subsídios, custeando as passagens transatlânticas, hospedagem e colocação nas fazendas de café, foi implantada com sucesso no estado de São Paulo. Na Argentina, houve o predomínio da imigração espontânea. As políticas liberais e os altos salários pagos nas épocas de colheitas do trigo e milho também tiveram êxito em atrair estrangeiros. As fontes revelaram também uma mobilidade geográfica e deslocamentos frequentes e de caráter sazonal dos imigrantes entre São Paulo e Buenos Aires. / The present work aims to analyze, comparatively, the policies for attraction, the activities, the flows and displacement of immigrants in Brazil and Argentina, specifically focusing on the regions of São Paulo and Buenos Aires from 1870 to 1930. We intend to identify, for both countries and regions, the similarities and differences of the implemented policies aimed to attract immigrants; to observe the pattern of the migration flows; and to examine the role of immigrants in the composition of these populations and their role within the economic activities at the rural and urban environments. We also examine the immigrants flow between the ports of Santos and Buenos Aires at the time, analyzing the numbers and place of origin of the immigrants, as well as their motivations, reported by the sources and the historiography. The information and data compiled to produce this study were collected from a variety of research sources: government data, laws, censuses, report statistics, among others. The archives consulted correspond to physical and online collections. This work is divided in three chapters. The sources revealed differences and resemblances between the migratory process to Brazil and Argentina. Throughout the nineteenth century, both in Brazil and Argentina, the governmental debates about the promotion of immigration were guided by the need of populating territories and finding labor to sustain the agro-export agriculture development. In addition to being a solution for the lack of work force on the lands and for the settlement of territories, in both countries the immigration was seen as the pathway to progress, society modernization and population whitening. From 1870 to 1930, considered the period with the higher occurrence of migration, Brazil and Argentina were the countries that received the largest amount of immigrants in Latin America. Brazil received more than 4.1 million of immigrants, while more than 6.2 million went to Argentina. In the period, the subsidy policy, financing the transatlantic travels, accommodation and location in the coffee farms, succeeded in São Paulo state. In Argentina, the spontaneous immigration prevailed. The liberal policies for immigrant attraction and the high weights paid on the wheat and maize harvest seasons also succeeded in attracting foreigners. Sources also revealed a geographic mobility and frequent displacements with a seasonal character by immigrants between São Paulo and Buenos Aires.

Refletindo sobre a idéia do espaço como elemento que ativa experiências e gera visualidades, este projeto caminha rumo à especificidade do lugar e adiciona um terceiro elemento, a ficção, ao perguntar: pode uma obra literária relativa ao lugar transformar-se em poética visual? O desenvolvimento desta questão propiciará reflexões na interface literatura, cinema, e artes visuais, além do entendimento e da experiência do espaço proposto, onde lugar físico e lugar ficcional sejam igualmente princípios ativadores do processo de criação de trabalhos audiovisuais. No aprofundamento do universo de autores como Jorge Luis Borges(1899-1986) e Marguerite Duras(1914-1996), esta pesquisa se dirige, através de uma práxis reflexiva, a um sentido inverso do encontrado no universo literário: na procura dos lugares reais a partir dos ficcionais, na constatação de uma memória construída a partir de um repertório relacionado a lugar, e nas possibilidades de transposição, transformação e permeabilidade dos discursos literário e visual. / Reflecting on the idea of space as an element that activates experiences and generates visuality, this project moves towards specificity of place and adds a third element, fiction, in order to ask: can a literary work about place turn into visual poetic? The development of this issue will provide reflections on literature, film and visual arts interface, beyond understanding and experience of the proposed space, where physical and fictional place activates, at the same time, the creation of audiovisual work. In deepening of the universe of authors such as Jorge Luis Borges (1899-1986) and Marguerite Duras (1914-1996), this research is directed through a reflective practice, to the reverse of that found in the literary universe: in search of the real places that comes from fictional, on finding a memory constructed from a repertoire connected to the idea of place, and on the possibilities of transposition, processing and permeability of visual and literary speech .

The dissertation examines Argentine immigration policy in 1852- 1914. It focuses on the immigration process itself, the attitude of the Argentine political cliques and population, the minority groups, the influence of immigration on the development of Argentina in the mentioned period, the living conditions of immigrants and the process of their acclimatisation. For a better understanding of the chosen topic, the work was divided into two parts, followed by individual chapters. As a result of the research of published and unpublished sources, professional literature and articles, historical publications and other available sources, the importance of European immigration to the country's economic development, modernisation, demographic and culture was confirmed. Although the immigration process was also linked to negative aspects, such as the disappearance of the indigenous population, social inequality and the significant influence of European societies on the domestic economy, the population growth, the integration of immigrants into the primary and secondary economic sectors and political consolidation made Argentina one of the world's fastest-growing economies.