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Competencia en Cladocera: implicancias de la sobreposición en el uso de los recursos tróficos
MARTINEZ,GINGER; MONTECINO,VIVIAN;
Revista chilena de historia natural , 2000, DOI: 10.4067/S0716-078X2000000400020
Abstract: although numerous evidence reveals the use of different feeding strategies among cladocerans, the impact of trophic niche overlap on their patterns of coexistence has been underestimated due to the classical description of passive feeding behavior. under microcosm conditions, paired experiments of population dynamics were conducted for the cladocerans moina micrura (moinidae) and ceriodaphnia dubia (daphnidae), specialists on the resources chlorella sp. and oocystis sp. (chlorococcales) respectively, and for the generalist species daphnia ambigua (daphnidae), during 35 - 45 days. while, the specialists m. micrura and c. dubia did not show evidences of competition, their presence lead to a significant decrease in the density of the generalist d. ambigua and in some cases even led to extinction. although the generalist qualitatively affected the dynamics of each specialist, it did not affect their density, thus resulting in an asymmetrical interaction among each specialist with the generalist species. these results demonstrate that the feeding behavior and resource use overlap should be determinant conditions in the composition of cladoceran assemblages
Conducta alimentaria de Daphnia ambigua Scourfield 1947, Moina micrura Kurz 1874 y Ceriodaphnia dubia Richard 1895 (Cladocera) frente a un gradiente de concentración de alimento Feeding behaviour of Daphnia ambigua Scourfield 1947, Moina micrura Kurz 1874 and Ceriodaphnia dubia Richard 1895 (Cladocera) under a food concentration gradient  [cached]
GINGER MARTINEZ
Revista chilena de historia natural , 2000,
Abstract: Debido a que Cladocera es el grupo de microfiltradores más abundante del zooplancton límnico y cuyas poblaciones se encuentran usualmente limitadas por alimento, la respuesta de los individuos frente a un gradiente de concentración de recursos tendría significativas implicancias sobre los patrones poblacionales y comunitarios. Se comparó la conducta alimentaria de Moina micrura, Ceriodaphnia dubia y Daphnia ambigua (Cladocera) frente a las microalgas Chlorella sp. y Oocystis sp. (Chlorophyceae) mediante los siguientes parámetros: Tasa de Ingesta Máxima (Imax), Concentración Limitante Incipiente (CLI) y Eficiencia de Consumo (b), los cuales fueron obtenidos a través de un modelo de respuesta funcional. Los resultados mostraron que D. ambigua presentó las mayores Imax y CLI sobre ambos recursos, sin embargo, esta especie presentó la menor b. Mientras que D. ambigua no presentó diferencias en b sobre Chlorella sp. y Oocystis sp., M. micrura presentó una mayor b sobre Chlorella sp. y C. dubia sobre Oocystis sp. Estos resultados revelan significativas diferencias interespecíficas en la respuesta alimentaria de Cladocera, grupo que presentó un complejo comportamiento frente a variaciones en la disponibilidad de recursos alimentarios Because Cladocera is the most abundant group of filter-feeders in the freshwater zooplankton and their populations are usually found under limited resources conditions, the individual response under a resources concentration gradient has important consequences on the population and community patterns. Feeding behavior of Moina micrura, Ceriodaphnia dubia and Daphnia ambigua (Cladocera) on the microalgae Chlorella sp. and Oocystis sp. (Chlorophyceae) was compared by using the following parameters: Maximum Ingestion Rate (Imax), Incipient Limiting Concentration (ILC) and Consumption Efficiency (b), which were obtained through a model of functional response. Results indicated that D. ambigua showed the highest Imax and ILC on both resources, however, this specie presented the lowest b. Whereas, D. ambigua did not show differences in b on Chlorella sp. or Oocystis sp., M. micrura showed a higher b on Chlorella sp. and C. dubia on Oocystis sp. These results reveal significant interspecific differences in the feeding response of Cladocera, which showed a complex behavior exposed to variations in the availability of food resources
Trophic and microhabitat niche overlap in two sympatric dendrobatids from La Selva, Costa Rica
Cajade, Rodrigo,Schaefer, Eduardo Federico,Duré, Marta Inés,Kehr, Arturo Ignacio
Cuadernos de Herpetología , 2010,
Abstract: Se estudió la ecología trófica y uso del microhábitat de Dendrobates auratus y Oophaga pumilio en un área de simpatría entre las dos especies ubicada en la Estación Biológica La Selva, Costa Rica. En este sitio ambos dendrobatidos son simpátricos debido a la introducción y naturalización de D. auratus en los últimos 24 a os. La dieta de ambas especies se describió a partir del análisis de la técnica del lavado de estómago. Los microhábitas utilizados fueron definidos según el sitio donde cada ejemplar fue capturado. La relación en el uso del microhábitat y la ecología trófica entre ambas especies fue evaluada utilizando el índice de solpamiento de Pianka (Ojk) en el análisis de la dieta (proporción de presas y volumen) y en el uso del microhábitat. La dieta de ambos dendrobátidos estuvo caracterizada principalmente por el consumo de himenópteros (hormigas), ácaros, y colémbolos, resultando consecuentemente en un alto índice de solapamiento en la proporción y volumen de las presas, sin embargo, este alto solapamiento no fue significativo y no implicó la presencia de interacciones negativas entre ambas especies. El uso del microhábitat presentó un solapamiento muy bajo y no significativo, indicando una diferenciación en los microhábitats utilizados por cada especie. La ausencia de interacciones negativas en cuanto al uso de los recursos tróficos entre ambos dendrobátidos podría deberse a la diferenciación en el uso del microhábitat, y posiblemente, a la abundancia de presas en el área. El gran volumen de formícidos y ácaros en la dieta de estas dos especies son consistentes con la hipótesis del consumo de estos artrópodos como una fuente de alcaloides. We studied the trophic ecology of Dendrobates auratus and Oophaga pumilio in La Selva Biological Station, Costa Rica. At this site, both dendrobatids are sympatric due to the introduction and naturalization of D. auratus in the last 24 years. Diets of both dendrobatids were recorded by the analysed stomach flushing technique. Microhabitats uses were defined as the site where each individual was captured. The influence of microhabitat on diets was evaluated by the dietary (prey proportions and volume) and microhabitat overlapsusing Pianka’s (Ojk) overlap index calculated with EcoSim software. Diets of both dendrobatids were principally characterized by the preference of hymenopterans (ants), acarines and collembolans, resulted in a high overlapping in prey proportions and prey volume. However, diets overlaps were not significant, suggesting the absence of negative feeding interactions.Microhabitat use was lo
Trophic and microhabitat niche overlap in two sympatric dendrobatids from La Selva, Costa Rica
Cajade,Rodrigo; Schaefer,Eduardo Federico; Duré,Marta Inés; Kehr,Arturo Ignacio;
Cuadernos de herpetolog?-a , 2010,
Abstract: we studied the trophic ecology of dendrobates auratus and oophaga pumilio in la selva biological station, costa rica. at this site, both dendrobatids are sympatric due to the introduction and naturalization of d. auratus in the last 24 years. diets of both dendrobatids were recorded by the analysed stomach flushing technique. microhabitats uses were defined as the site where each individual was captured. the influence of microhabitat on diets was evaluated by the dietary (prey proportions and volume) and microhabitat overlaps using pianka's (ojk) overlap index calculated with ecosim software. diets of both dendrobatids were principally characterized by the preference of hymenopterans (ants), acarines and collembolans, resulted in a high overlapping in prey proportions and prey volume. however, diets overlaps were not significant, suggesting the absence of negative feeding interactions. microhabitat use was low overlapped and also not significant, suggesting a differentiation on the use of spatial resource. the absence of negative feeding interactions between dendrobates auratus and oophaga pumilio could be due to segregation in microhabitat use and possible by the abundance of trophic resource in the area. the great large volumes of formicids and acarines in the diet of this dendrobatids are in agreement with the hypothesis of these arthropods as a dietary source of alkaloids.
Trophic niche overlap between two Chilean endemic species of Trichomycterus (Teleostei: Siluriformes)
SCOTT,SERGIO; PARDO,RODRIGO; VILA,IRMA;
Revista chilena de historia natural , 2007, DOI: 10.4067/S0716-078X2007000400004
Abstract: trichomycterus areolatus and trichomycterus chiltoni are endemic siluriform fishes of chile. they are the only chilean species of this genus that live in sympatry and coexist in the biobio basin. high trophic niche overlap between both species was found. horn's index varied from 0.668 to 0.885 among seasons, without significant differences, and schoener's index varied from 0.639 to 0.912. also the discriminant analysis showed no significant differences in prey item between the two species. trophic composition of t. chiltoni and t. areolatus consisted mainly in chironomid larvae and other aquatic invertebrates. at all seasons t. chiltoni showed the greatest prey richness. principal component analysis (pca) showed a high similarity between diets of t. areolatus and t. chiltoni. these diet scores were significantly related with body size in t. chiltoni whereas t. areolatus showed a significant relationship with seasons. this may indicate a generalist strategy in t. areolatus by varying its diet in function of available prey items in each season, whereas t. chiltoni would be specialized in relation to individual size and intraspecific habitat partitioning
Overfishing of Small Pelagic Fishes Increases Trophic Overlap between Immature and Mature Striped Dolphins in the Mediterranean Sea  [PDF]
Encarna Gómez-Campos, Assumpció Borrell, Luis Cardona, Jaume Forcada, Alex Aguilar
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0024554
Abstract: The interactions among diet, ecology, physiology, and biochemistry affect N and C stable isotope signatures in animal tissues. Here, we examined if ecological segregation among animals in relation to sex and age existed by analyzing the signatures of δ15N and δ13C in the muscle of Western Mediterranean striped dolphins. Moreover, we used a Bayesian mixing model to study diet composition and investigated potential dietary changes over the last two decades in this population. For this, we compared isotope signatures in samples of stranded dolphins obtained during two epizootic events occurring in 1990 and 2007–2008. Mean δ13C values for females and males were not significantly different, but age-related variation indicated δ13C enrichment in both sexes, suggesting that females and males most likely fed in the same general areas, increasing their consumption of benthic prey with age. Enrichment of δ15N was only observed in females, suggesting a preference for larger or higher trophic level prey than males, which could reflect different nutritional requirements. δ13C values showed no temporal variation, although the mean δ15N signature decreased from 1990 to 2007–2008, which could indicate a dietary shift in the striped dolphin over the last two decades. The results of SIAR indicated that in 1990, hake and sardine together contributed to 60% on the diet of immature striped dolphins, and close to 90% for mature striped dolphins. Conversely, the diet of both groups in 2007–2008 was more diverse, as hake and sardine contributed to less than 40% of the entire diet. These results suggest a dietary change that was possibly related to changes in food availability, which is consistent with the depletion of sardine stocks by fishing.
Servicio de transporte urbano de pasajeros: cuando la competencia puede no ser deseable  [cached]
Mario F. Mathieu
Ciencia, Docencia y Tecnología , 2010,
Abstract: En este artículo se pretende mostrar que introducir competencia en el servicio de transporte urbano de pasajeros es contraproducente, y se apunta a refutar las implicancias del paradigma competitivo en la teoría de la regulación. En la investigación que se expone se observó cómo evolucionó la prestación del servicio, entre los a os 1994 y 2004, en la ciudad de Paraná (Provincia de Entre Ríos, Argentina), que en el momento del Censo Nacional de 2001 tenía 237.968 habitantes y cubría una superficie urbana de 43 km2. En el a o 1994 se introdujeron medidas que implicaron una desregulación parcial del servicio de transporte urbano de pasajeros, y aquí se muestra por qué se consideraron como tal y se analiza cuál fue su impacto en el funcionamiento. Se espera que el examen de este proceso aporte a una visión crítica del paradigma competitivo y sus implicancias en la teoría de la regulación.
Subfossil faunal and floral remains (Cladocera, Pediastrum) in two northern Lobelia lakes in Finland Restes subfossiles faunistiques et floristiques (Cladocères, Pediastrum) dans deux Lobelia lacs du nord de la Finlande
Szeroczyńska K.,Zawisza E.
Knowledge and Management of Aquatic Ecosystems , 2011, DOI: 10.1051/kmae/2011066
Abstract: The analysis of lake sediment cores have been long used as historical integrators of environmental changes. Nutrient poor isoetid lakes remain under studied in the north boreal region. Hence, the bottom sediments of two north boreal Lobelia lakes, located in NE Finland were analysed for the presence of Cladocera and Pediastrum remains. Sediment cores from the littoral zones were sampled, sectioned every centimetre and aged with 210Pb. The number of taxa of both Cladocera and Pediastrum identified in the cores was high, while the number of individuals in each taxon was low. In Lake Kevoj rvi, twenty five Cladocera species and eight Pediastrum species were found. Along with widely distributed species, typical for north boreal regions, species preferring more temperate environments occurred. In Lake Pet j lampi, the species composition was similar. Twenty one Cladocera species and five Pediastrum species occurred there, however with a lower frequency of individuals in each taxon. In both Lobelia lakes, analyses of subfossil Cladocera and Pediastrum remains, from the sediments deposited within the last 30–40 years indicated a recent increase in trophic status. L’analyse des carottes de sédiments lacustres a longtemps été utilisée comme intégrateur historique de changements environnementaux. Les lacs à isoètes pauvres en éléments nutritifs demeurent sous-étudiés dans la région boréale nord. Ainsi, les sédiments de deux Lobelia lacs au nord boréal, situés dans le nord-est de la Finlande ont été analysés pour la présence de restes de Cladocères et Pediastrum. Les carottes de sédiments des zones littorales ont été échantillonnées, sectionnées à chaque centimètre et datées au 210Pb. Le nombre de taxons des Cladocères et Pediastrum identifiés dans les noyaux a été élevé, tandis que le nombre d’individus dans chaque taxon a été faible. Dans le lac Kevoj rvi, 25 espèces de Cladocères et 8 espèces de Pediastrum ont été trouvées. Parmi des espèces largement distribuées, typiques des régions du Nord boréal, des espèces préférant des milieux plus tempérés ont été trouvées. Dans le lac Pet j lampi, la composition des espèces a été similaire. Vingt et une espèces de Cladocères et cinq espèces de Pediastrum ont été trouvées, toutefois avec une fréquence plus faible d’individus dans chaque taxon. Dans ces deux Lobelia lacs, les analyses de subfossiles de Cladocères et Pediastrum, à partir des sédiments déposés dans les 30–40 dernières années ont montré une augmentation récente de l’état trophique.
Trophic niche overlap between two Chilean endemic species of Trichomycterus (Teleostei: Siluriformes) Sobreposición de nicho alimentario de dos especies endémicas chilenas de Trichomycterus (Teleostei: Siluriformes)
SERGIO SCOTT,RODRIGO PARDO,IRMA VILA
Revista chilena de historia natural , 2007,
Abstract: Trichomycterus areolatus and Trichomycterus chiltoni are endemic siluriform fishes of Chile. They are the only Chilean species of this genus that live in sympatry and coexist in the Biobio basin. High trophic niche overlap between both species was found. Horn's index varied from 0.668 to 0.885 among seasons, without significant differences, and Schoener's index varied from 0.639 to 0.912. Also the discriminant analysis showed no significant differences in prey item between the two species. Trophic composition of T. chiltoni and T. areolatus consisted mainly in chironomid larvae and other aquatic invertebrates. At all seasons T. chiltoni showed the greatest prey richness. Principal component analysis (PCA) showed a high similarity between diets of T. areolatus and T. chiltoni. These diet scores were significantly related with body size in T. chiltoni whereas T. areolatus showed a significant relationship with seasons. This may indicate a generalist strategy in T. areolatus by varying its diet in function of available prey items in each season, whereas T. chiltoni would be specialized in relation to individual size and intraspecific habitat partitioning Trichomycterus areolatus y Trichomycterus chiltoni son peces Siluriformes endémicos de Chile, siendo las únicas especies chilenas conocidas de este género que coexisten en simpatría. Se encontró alta sobreposición de nicho trófico entre estas dos especies. El índice de Horn varió de 0,668 a 0,885 entre estaciones, sin diferencias significativas, y el índice de Schoener varió de 0,639 a 0,912. Además el análisis discriminante no mostró diferencias significativas en las presas entre las dos especies. La composición de la dieta de T. chiltoni y T. areolatus consistió principalmente en larvas de chironómidos y otros invertebrados acuáticos. En todas las estaciones estudiadas T. chiltoni mostró una riqueza de presas mayor. El análisis de componentes principales (PCA) mostró una gran similitud entre las dietas de T. areolatus y T. chiltoni. Estos resultados se relacionaron significativamente con las medidas de tama o corporal en T. chiltoni mientras que T. areolatus mostró una relación significativa con las estaciones. Esto podría indicar una estrategia generalista en T. areolatus, variando su dieta en función de las presas disponibles en cada estación, mientras que T. chiltoni estaría especializado en función del tama o individual
Dieta, selectividad y solapamiento trófico entre las tallas del pez blanco Menidia humboldtiana (Atheriniformes: Atherinopsidae) en el embalse Tiacaque, México Diet, selectivity and trophic overlap between the sizes of Silverside Menidia humboldtiana (Atheriniformes: Atherinopsidae) in the reservoir Tiacaque, Mexico
Regina Sánchez,Abigahil Ochoa,Angélica Mendoza
Revista de Biología Tropical , 2013,
Abstract: Menidia humboldtiana es una especie nativa muy apreciada por su delicado sabor. Se determinó el espectro trófico, selectividad y solapamiento trófico de ésta, durante 1995 (épocas del a o), se obtuvieron muestras de zooplancton e identificaron a nivel genérico. Los peces capturados se agruparon en intervalos de longitud estándar para cada época. Se analizaron los contenidos estomacales (método volumétrico, Laevastu), selectividad (Chesson) y solapamiento trófico (Morisita). Se registraron 14 géneros de zooplancton; Bosmina el más abundante (29 625ind/10L) seguido por Cyclops (9 496ind/10L) ambos en primavera. Los peces peque os (1-4.9cm) consumen a Cyclops en altos porcentajes en primavera e invierno, 61.24-69.82% respectivamente. Ceriodaphnia es consumida por peces de 3-10.9cm y de 13-14.9cm con 72.41-95.5% en verano; en oto o las tallas peque as ingieren a Mastigodiaptomus y Ceriodaphnia; Daphnia y Bosmina por peces de 5-8.9cm y los más grandes (9-14.9cm) a Ceriodaphnia. M. humboldtiana realiza una depredación selectiva por Ceriodaphnia, Daphnia, Mastigodiaptomus, Bosmina y Cyclops. El solapamiento trófico fue muy marcado entre todas las tallas en primavera, oto o e invierno, a diferencia en verano los peces de 1-2.9 y 11-12.9cm no registraron un solapamiento con otros intervalos de longitud. M. humboldtiana es una especie zooplanctófaga, que realiza una depredación selectiva y un marcado solapamiento trófico entre los intervalos de longitud. Menidia humboldtiana, a native species of Mexico, is a common inhabitant of local reservoirs. It represents a highly appreciated fish of economic importance in the central part of the country because of its delicate flavor. Trophic behavior of this species is important to understand the relationships with other fish species in reservoirs. With the aim to study this specific topic, the trophic spectrum, selectivity coefficient and overlap, were determined among different sizes of the Silverside M. humboldtiana. For this, both zooplankton and fish samples were taken during four different seasons of 1995. Zooplankton samples were taken through a mesh (125micron), and all organisms were identified to generic level. Fish were captured and grouped into standard length intervals per season, and the stomach contents were obtained and analyzed. Trophic interactions included the stomach contents analysis (Laevastu method), the coefficient of selection (Chesson) and the trophic overlap (Morisita index modified by Horn) between sizes. A total of 14 zooplankton genera were identified, of which Bosmina was the most abundant (29
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