Are environmental factors or hervibory controlling plantlet emergence in a floodplain of the Parana river?

La etapa de emergencia y establecimiento de plántulas es crítica en la regeneración de un bosque porque las plantas son más sensibles a las condiciones del medio. Se evaluó la influencia de la luz, humedad del suelo, nivel topográfico y el efecto de la herbivoría sobre la emergencia de plántulas en un bosque de la planicie proximal de inundación situado aguas abajo de la confluencia Paraná-Paraguay (27º26'S, 58º51'O) mediante observaciones de campo y ensayos de laboratorio. Hubo diferencias significativas entre el número de plántulas emergidas y la exposición solar en sitios abiertos y con cobertura vegetal densa, siendo mayor el número de individuos en los sitios más iluminados. No se encontraron diferencias significativas en el número de plántulas emergidas con relación a la humedad del suelo. La emergencia de plántulas fue mayor en la posición topográfica más baja, más inundable. La herbivoría fue intensa durante la primera fase del desarrollo. El establecimiento de las plántulas dependió principalmente de la disponibilidad de luz y de la presión ejercida por los invertebrados herbívoros..The germination phase and seedling establishment is critical in forest regeneration because plants are more susceptible to environmental conditions. The influence of light, soil moisture, topographic level and the influence of herbivory on seedling emergence in a forest in the proximal floodplain downstream of the Parana-Paraguay confluence (27º26'S, 58º51'W) was evaluated in field and laboratory approaches. There were significant differences between the number of seedlings that emerged and sun exposure in sites with dense vegetation cover. There was no significant difference between the number of seedlings that emerged and soil moisture. The emergence of seedlings was higher in the topographically lowest area of the forest. Hervibory was the main factor that controlled seedling development during the initial phases of development. The establishment of seedlings depended largely on light availability and pressure from invertebrate herbivores.Fil: Mari, Eliana Karina Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; ArgentinaFil: Galassi, María Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; Argentin

The role of the host-specific grasshopper <i>Cornops aquaticum</i> (Orthoptera: Acrididae) as consumer of native <i>Eichhornia crassipes</i> (Pontederiaceae) floating meadows

Cornops aquaticum is a widely distributed semiaquatic grasshopper in the Neotropics. The development, feeding and oviposition of C. aquaticum take place on Pontederiaceae, especially on species of Eichhornia. Several aspects of the feeding of C. aquaticum are studied because is one of the most important herbivores of the highly invasive floating Eichhornia crassipes in native areas. The aims of this paper were: (1) to quantify the amount of E. crassipes consumed by C. aquaticum, (2) to determine the growth rate and the conversion efficiency of food ingested by this grasshopper, and (3) to determine the possible effect of consumption on E. crassipes productivity. Thirty individuals from each specific age class were used in the experiment: nymphs A, nymphs B, adult males and adult females. Insects were individually confined in plastic pots with a leaf of E. crassipes. We estimated feeding by individual, consumption index (CI), relative growth rate (GR) and efficiency of conversion of ingested food to body substance (ECI). The impact of C. aquaticum consumption on E. crassipes floating meadows was assessed with the abundance of the grasshopper, and the available data on primary production of the host plant at the study site. Food intake of C. aquaticum was 11.23% of plant productivity. Food consumption, growth rate and food conversion efficiency of this grasshopper varied according to the specific age classes. Damage caused by C. aquaticum is high in comparison with the damage caused by other semiaquatic and grassland grasshoppers, however it is not enough to prevent the growth and coverage of native E. crassipes floating meadows because abundance of grasshoppers are realtively low and the growth rate and productivity of the host plant is high.Centro de Estudios Parasitológicos y de Vectore

¿Qué método es mas apropiado para las estimaciones de diversidad de invertebrados en la hojarasca de bosques riparios (Chaco, Argentina)?

El objetivo de este estudio fue evaluar la eficacia de los embudos Tullgren-Berlese, los extractores Winkler y las trampas de caída para capturar los invertebrados de la hojarasca de un bosque localizado en la planicie del río Paraná. Se registraron 9 clases y 26 órdenes de invertebrados. Los arácnidos (subclase Acari) fueron más abundantes que los colémbolos e insectos utilizando los métodos de Winkler y Tullgren-Berlese. Con la trampa de caída, Insecta fue el grupo más abundante. Los resultados sugieren una mayor similitud (95.27%) entre los métodos embudos Tullgren-Berlese y extractores Winkler, y una clara diferencia entre estos métodos y la trampa de caída, produciendo diferentes niveles de precisión taxonómica. Cada método fue selectivos para distintas familias de Coleoptera. Las curvas de acumulación de taxa calculadas para cada método no muestran una tendencia asintótica.Fil: Galassi, María Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; ArgentinaFil: Poi, Alicia Susana G.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; Argentin

Invertebrate assemblages associated with leaf litter in three floodplain wetlands of the Paraná River

We analyzed invertebrate abundance and richness associated with decomposing litter across three riverine wetlands with different inundation regimes located in the alluvial floodplain of the Parana´ River. Three replicate bags were incubated for different types of leaf litter that were dominant in each wetland for five sampling dates, yielding a total of 165 litterbags. The number of invertebrates per g of remaining leaf litter differed among wetlands and was affected by leaf litter type and incubation date within each wetland. In contrast to abundance, differences in invertebrate composition were more pronounced across wetlands than across leaf litter types within a wetland. Different species dominated in each of the three wetlands. When we compared the number of invertebrates per g remaining of a single litter type (Eichhornia crassipes) across the three wetlands, variability in density was explained by the NH4+ content of the water and dissolved oxygen concentration. Many invertebrates associated with litter may not be directly involved in shredding the material, and collectors dominated invertebrate assemblages at study sites. Although both litter quality and wetland condition affect the invertebrates colonizing leaf litter, our results suggest that spatial heterogeneity, linked to connectivity, plays an important role in determining invertebrate assemblages.Fil: Poi, Alicia Susana G.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; ArgentinaFil: Galassi, María Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; ArgentinaFil: Franceschini, Maria Celeste. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; Argentin

Is the biomass of waterhyacinth lost through herbivory in native areas important?

The lamina area damaged and biomass per leaves removed by invertebrate herbivores were measured across seasons on water hyacinth, Eichhornia crassipes (Mart.) Solms (Pontederiaceae). The amount of the leaf biomass permeter square lost through herbivory was also assessed in different sampling dates in the plant population. Ten leaves of water hyacinth were sampled in each of 18 site-habitat-date combinations. Sampling dates were chosen to follow the plant phenology. The lamina area damaged (surface abrasions and holes) was measured with the visual estimation method; biomass removed by herbivores (surface abrasions and holes) was calculated indirectly from the damaged lamina area. Significant differences in total damaged area and removed biomass per lamina were found between sampling dates at each site, with highest values in March (end of growth period). Total damaged area per lamina (surface abrasions + holes) varied between 11% in March and 6% in July (decay period). Total removed biomass (surface abrasions + holes) varied between 27% in March and 13% in July. Significant differences in biomass removed by herbivory were found between sampling dates at each site. Biomass of lamina removed by herbivores perm2 varied between 26 and 13% in different seasons. The herbivore damage of discrete samples and the indirect method to calculate the biomass removed is useful in sites with aquatic free floating plants, where experimental exclusion of insects may be difficult to carry outFil: Franceschini, Maria Celeste. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; ArgentinaFil: Poi, Alicia Susana G.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; ArgentinaFil: Galassi, María Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; Argentin

Theoretical study of W-values for particle impact on water

The W-values and the differential values w, were calculated by electron, proton and antiproton impact on liquid and vapor water. Two different theoretical approximations were used: the Fowler Equation (based on the Continuous Slowing Down Approximation), and the Monte Carlo code MDM, which does an event-by-event tracking of all generated particles in the media. The dependence on the type and charge of the projectiles and the relevance on the appropriate inelastic cross sections employed in the calculations were studied. For electron impact, results obtained with both models are in good agreement with experimental data and with other theoretical calculations. However, the MDM results are more representative of the stochastic nature of radiation-media interactions. The w-values for swift proton and antiproton impact on vapor water, calculated using the Fowler Equation, are in very good agreement with the results obtained by electron impact in the same velocity regime.Fil: Tessaro, Veronica Belen. Universite Claude Bernard Lyon 1. Institut de Physique Nucléaire de Lyon.; Francia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Poignant, F.. Universite Claude Bernard Lyon 1. Institut de Physique Nucléaire de Lyon.; FranciaFil: Gervais, B.. Universite de Caen Basse Normandie; FranciaFil: Beuve, M.. Universite Claude Bernard Lyon 1. Institut de Physique Nucléaire de Lyon.; FranciaFil: Galassi, María Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; Argentin

The role of the host-specific grasshopper Cornops aquaticum (Orthoptera: Acrididae) as consumer of native Eichhornia crassipes (Pontederiaceae) floating meadows

Cornops aquaticum es una tucura semiacuática Neotropical que vive asociada a las Pontederiaceae y constituye uno de los más importantes herbívoros de Eichhornia crassipes en áreas nativas. Los objetivos de este trabajo son: (1) cuantificar el consumo de C. aquaticum (2) determinar la tasa de crecimiento y la eficiencia de conversión del alimento ingerido de esta tucura, y (3) determinar el efecto del consumo en la productividad de E. crassipes. De cada categoría de edades de la población se utilizaron 30 individuos: ninfas A, ninfas B, adultos machos y hembras. Los insectos fueron confinados individualmente en recipientes con hojas de E. crassipes. Luego, se estimó el consumo por individuo, la tasa de consumo (CI), tasa de crecimiento (GR) y la eficiencia de conversión del alimento (ECI). La abundancia de C. aquaticum se determinó en verano y con los datos de productividad de la planta se calculó el efecto del consumo sobre E. crassipes. La tasa de consumo, tasa de crecimiento y la eficiencia de conversión del alimento varió entre las distintas categorías de edades de la población. C. aquaticum consume el 11% de la productividad primaria de E. crassipes. Si bien el consumo es alto, el daño no produce mermas importantes en los camalotales debido a la abundancia relativamente baja de C. aquaticum y la alta productividad de la planta huésped

The role of the host-specific grasshopper Cornops aquaticum (Orthoptera: Acrididae) as consumer of native Eichhornia crassipes (Pontederiaceae) floating meadows

Cornops aquaticum is a widely distributed semiaquatic grasshopper in the Neotropics. The development, feeding and oviposition of C. aquaticum take place on Pontederiaceae, especially on species of Eichhornia. Several aspects of the feeding of C. aquaticum are studied because is one of the most important herbivores of the highly invasive floating Eichhornia crassipes in native areas. The aims of this paper were: (1) to quantify the amount of E. crassipes consumed by C. aquaticum, (2) to determine the growth rate and the conversion efficiency of food ingested by this grasshopper, and (3) to determine the possible effect of consumption on E. crassipes productivity. Thirty individuals from each specific age class were used in the experiment: nymphs A, nymphs B, adult males and adult females. Insects were individually confined in plastic pots with a leaf of E. crassipes. We estimated feeding by individual, consumption index (CI), relative growth rate (GR) and efficiency of conversion of ingested food to body substance (ECI). The impact of C. aquaticum consumption on E. crassipes floating meadows was assessed with the abundance of the grasshopper, and the available data on primary production of the host plant at the study site. Food intake of C. aquaticum was 11.23% of plant productivity. Food consumption, growth rate and food conversion efficiency of this grasshopper varied according to the specific age classes. Damage caused by C. aquaticum is high in comparison with the damage caused by other semiaquatic and grassland grasshoppers, however it is not enough to prevent the growth and coverage of native E. crassipes floating meadows because abundance of grasshoppers are realtively low and the growth rate and productivity of the host plant is high. Rev. Biol. Trop. 59 (3): 1407-1418. Epub 2011 September 01.Cornops aquaticum es una tucura semiacuática Neotropical que vive asociada a las Pontederiaceae y constituye uno de los más importantes herbívoros de Eichhornia crassipes en áreas nativas. Los objetivos de este trabajo son: (1) cuantificar el consumo de C. aquaticum (2) determinar la tasa de crecimiento y la eficiencia de conversión del alimento ingerido de esta tucura, y (3) determinar el efecto del consumo en la productividad de E. crassipes. De cada categoría de edades de la población se utilizaron 30 individuos: ninfas A, ninfas B, adultos machos y hembras. Los insectos fueron confinados individualmente en recipientes con hojas de E. crassipes. Luego, se estimó el consumo por individuo, la tasa de consumo (CI), tasa de crecimiento (GR) y la eficiencia de conversión del alimento (ECI). La abundancia de C. aquaticum se determinó en verano y con los datos de productividad de la planta se calculó el efecto del consumo sobre E. crassipes. La tasa de consumo, tasa de crecimiento y la eficiencia de conversión del alimento varió entre las distintas categorías de edades de la población. C. aquaticum consume el 11% de la productividad primaria de E. crassipes. Si bien el consumo es alto, el daño no produce mermas importantes en los camalotales debido a la abundancia relativamente baja de C. aquaticum y la alta productividad de la planta huésped

Leaf Litter and Invertebrate Colonization: the Role of Macroconsumers in a Subtropical Wetland (Corrientes, Argentina)

We studied the breakdown rates and the invertebrate abundance and biomass for the litter of five native aquatic plants (Eichhornia crassipes, Eichhornia azurea, Thalia multiflora, Oxycaryum cubense and Hydrocotyle ranunculoides) in a shallow rain-fed lake using litter bags. The diets of the prawn Pseudopalaemon bouvieri and the amphipod Hyalella curvispina were determined and classified into five food items. Litter breakdown was fast (>0.010 day−1) for all species studied, although the breakdown rates were significantly affected by the litter species. The abundance of invertebrates colonizing the litter was significantly different among the species, but the biomass did not differ. The invertebrate taxa that colonized the litter of the different species were broadly similar, consisting primarily of oligochaetes, amphipods, prawns, ostracods, gastropods, water mites and several types of insect larvae (chironomids and mayflies). In terms of the number of individuals, naidid oligochaetes dominated the assemblages. In terms of biomass, P. bouvieri and H. curvispina reached 67.6 and 18.2 % of the total, respectively. Our results indicate that macroconsumers are involved in the breakdown process, since these species consume plant remains and detritus and highlight the importance of leaf litter composition on the abundance of invertebrates that colonize the litter.Fil: Poi, Alicia Susana G.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; ArgentinaFil: Galassi, María Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; ArgentinaFil: Carnevali, Romina Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; ArgentinaFil: Gallardo, Luciana Irene. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; Argentin