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Factors affecting the dominance hierarchy dynamics in a hummingbird assemblage

Current Zoology 2019年第3期65卷 261-268页

作者： Ubaldo mARQUEZ-luna Carlos lara Pablo CORCUERA Pedro Luis VALVERde Doctorado en Ciencias Biologicas y de la salud Universidad Autonoma Metropolitana-lztapalapa Ciudad de Mexico Mexico Centro de Investigacion en Ciencia Biologicas Universidad Autonoma de Tlaxcala. Km 10.5 Autopista Tlaxcala-San Martin Texmelucan San Felipe Ixtacuixtla Tlaxcala Mexico departamento de Biologia Universidad Autonoma Metropolitana-lztapalapa Ciudad de Mexico

Intra and in terspecific competiti on for n ectar play an imports nt role in hummingbird communities. Larger sized species usually exclude smaller species from the rich floral resources. However, it has been recently postulated that the competitive advantages of a large body size decline as the evolutionary distance between the contending species in creases. In this study, we analyzed dominance hierarchy dynamics in a hummingbird assemblage in central mexico. By monitoring hummingbird territories established in three plant species through 1 year, we assessed the effects of energy within territories and the territory owners identity in the frequency of inter and intraspecific encounters. We also evaluated if these factors affect the dominance of larger species when they compete against smaller distantly related contenders. Our results show that their frequency of intraspecific encounters was related with the identity of the territory's owner. On the contrary, the frequency of interspecific encounters was related with both the territory and the identity of the territory's owner. We did not find a significant difference between the number of encounters dominated by larger and smaller species and their conte nders. However, the in crease in genetic dista nee between contenders was positively associated with a higher frequency of encounters dominated by small *** results showed that the ecological factors and evolutionary relationships among contenders play important roles in the dominance hierarchy dynamics.

关键词： agonistic behavior competition hummingbirds resource quality territoriality

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Physicochemical and Rheological Characterization of an Acidic milk Product: Kefir Concentration Effect

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Journal of Food science and Engineering 2017年第2期7卷 86-92页

作者： Jorge Octavio Virues delgadillo m.guel de jesús luna lara Claudia Karina Lozada santillan Carmen Bulbarela sampieri López del Castillo Lozano micloth Facultad de Ciencias Químicas Universidad Veracruzana Lomas del Estadio S/N Xalapa Veracruz 91000 México

The main objective of this study was the analysis of physicochemical and rheological behavior of a drinkable beverage prepared with different concentrations (5%, 10% and 20% w/w) of Kefir. several rheological models were also evaluated to determine the model that better fit experimental data. Apparent viscosity was measured with a Brookfield Viscometer within shear rates of 0.26 rad/s to 2.09 rad/s; and with an Ar-2000ex TA Instruments Rheometer within shear rates of 0.01 rad/s to 1,000 rad/s. Physicochemical tests, such as titratable acidity, chloride percent, fat concentration, color, humidity, syneresis, and total solids, were determined using laboratory equipment. The main result observed in all samples tested with Brookfield viscometer was that Kefir drink behaved as a Newtonian Fluid within shorter strain rates (0.26 rad/s to 2.09 rad/s). However, when the same samples were tested with Ar-2000ex Rheometer, a different behavior was observed: Over a wider range of shear rates, the fully non-Newtonian behavior of Kefir samples was discovered. Besides, additional variables such as shear and normal stresses, and loss and storage modulus, were analyzed with Ar-2000ex Rheometer. The rheological model that better fitted the experimental data was Cross model, followed by Power Law model. statistical analysis of viscosity data acquired with Brookfield Viscometer from all Kefir concentrations was not significant (p values greater than 0.05); which demonstrated that the effect of Kefir concentration over shorter strain rates was not significant, and thus, the samples behave as a Newtonian fluid. On the other hand, p values lower than 0.05 were observed in most of the different Kefir concentration samples tested with Ar-2000ex Rheometer; which indicates that a statistical significant effect was observed and thus a non-Newtonian behavior of Kefir samples. All statistical analysis was performed with sPss v.16 software, selecting a Duncan Test with a confident interval of 95%

关键词： Food rheology viscosity shear rate kefir concentration

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