Browsing by Author "Bozinovic, F."

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    Ecological efficiency and legitimacy in seed dispersal of an endemic shrub (Lithrea caustica) by the European rabbit (Oryctol gus cuniculus) in central Chile
    (2008) Castro, S. A.; Bozinovic, F.; Jaksic, F. M.
    The European rabbit (Oryctolagus cuniculus) is an alien herbivore in central Chile. Although its diet is poorly studied, this rabbit is known to consume native fruits and seeds, and thus it could act as a seed-dispersal agent. We evaluated the effect of endozoochory by rabbits on the survival and germination of seeds of a native shrub (Lithrea caustica, Anacardiaceae), as well as its consequences for seed dispersal. We extracted seeds by hand from parental shrubs, and compared the germination dynamics of seeds passing once and twice throughout the rabbit's gut (simulating its coprophagy) versus control treatments (seeds not consumed). Additionally, in permanent 2 x 2 m sampling plots placed in the wild, we evaluated the abundance of L. caustica seedlings and of its seeds in rabbit droppings. Results indicate that rabbits reduced seed survival to 82% on average with the first gut passage, and to an additional 52% with a second passage. Nevertheless, germination variables such as initiation time and germination, as well as final germination rate, increased significantly in comparison to non-ingested seeds. Sampling plots showed that L. caustica seedlings were concentrated principally underneath woody patches, which are then regarded as safe sites. Outside shrub cover, seedling abundance small, this indicates that open places are unsafe sites. We recorded that feces (and seeds contained) were deposited in higher proportion beneath woody cover, Thus, the native shrub L. caustica may be dispersed by alien rabbits through endozoochory, which provides legitimacy and efficiency in this dispersal service. Alien rabbits may fill a similar role played by native mammals, which have been reduced in abundance by human agency in central Chile. We suggest that the generalist syndrome, common among plants and dispersers, may be an arena of positive effects in ecological interactions between alien and native species. (c) 2008 Published by Elsevier Ltd.
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    ENSO-associated response of field urine osmolality in the insectivorous marsupial Thylamys elegans
    (2008) Tirado, C.; Cortes, A.; Jaksic, F. M.; Bozinovic, F.
    From 1991 to 1994, we assessed physiological responses in field urine osmolality (Uosm) of an insectivorous marsupial (Thylamys elegans) of semiarid Chile faced with a complete cycle of El Nino Southern Oscillation (ENSO). El Nino phase of ENSO determined the initial 2 wet years at the Study site. while La Nina phase determined the 2 subsequent dry years. The marsupial showed marked temporal fluctuations in field Uosm values, with both seasonal and between-year patterns of physiological variability. Indeed, Uosm values during wet years were: 2.719 +/- 405mOsm/kg in summer versus 2.246+209mOsm/kg in winter. During dry years in summer, Uosm values were: 3.340 +/- 384 mOsm/kg versus 2.481+293mOsm/kg during winter. There were significant effects of dry versus wet years and between dry and wet seasons on Uosm values, as well as a statistical interaction year x season. We discuss how the integration of flexible physiological mechanisms enable an insectivorous marsupial to cope with seasonal and yearly water variability in a semidesert, and also the importance of using ENSO climate effects as a proxy for the study of future climate change in natural Communities and its subsequent impact on field physiological performance of desert mammals. (c) 2008 Elsevier Ltd. All rights reserved.
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    Enzymatic flux capacities in hummingbird flight muscles: a "one size fits all" hypothesis
    (2011) Fernandez, M. J.; Bozinovic, F.; Suarez, R. K.
    Hummingbirds (family Trochilidae) are among the smallest endothermic vertebrates representing an extreme, among birds, in their physiological design. They are unique in their ability to sustain hovering flight, one of the most energetically demanding forms of locomotion. Given that hovering metabolic rate (HMR) in hummingbirds scales allometrically as M-0.78 (M is mass), we tested the hypothesis that variation in HMR may be correlated with variation in maximal enzyme activities (V-max values) of key enzymes in glucose and fatty acid oxidation pathways in the flight muscles of four species of hummingbirds ranging in body mass from 4 to 20 g. We also estimated metabolic flux rates from respirometric data obtained during hovering flight. The data are striking in the lack of correlation between V-max values and flux rates at most steps in energy metabolism, particularly at the hexokinase and carnitine palmitoyltransferase reactions. In the context of hierarchical regulation analysis, this finding suggests that metabolic regulation (resulting from variation in substrate, product, or allosteric regulator concentrations) dominates as the proximate explanation for the interspecific variation in flux. On the other hand, we found no evidence of hierarchical regulation of flux, which results from variation in V-max and is based on variation in enzyme concentration [E]. The evolutionary conservation of pathways of energy metabolism suggests that "one size fits all" among hummingbirds.
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    Seasonal acclimation of energy and water balance in desert-dwelling rodents of South America
    (2024) Cavieres, G.; Bozinovic, F.; Coronel-Montigel, M.; Dacar, M. A.; Sassi, P. L.
    Seasonal changes in environmental conditions may induce reversible physiological adjustments in organisms. We studied the acclimatization for multiple stressors in energy expenditure and water balance in Galea leucoblephara, a diurnal hystricognath rodent native to South America that experiences significant changes in temperature, precipitation, and food availability among seasons. We conducted a field study in the Monte Desert of Mendoza, Argentina, where we evaluated adult individuals' physiological status during two contrasting seasons in terms of climate and primary productivity. Reduced temperature, rainfall, and primary productivity during winter were associated with a decrease of 70% in basal metabolic rate (BMR), 30% in total evaporative water loss (TEWL), and 9% in body mass (Mb). In contrast, higher water availability, high temperature, and primary productivity during summer, induced significant increases in energy expenditure and evaporative water loss. As expected, the proportion of dietary items consumed by G. leucoblephara varied seasonally, resulting in a more diverse diet during summer. Our results illustrate how G. leucoblephara can cope with high seasonal contrasts in water availability, temperature, and food availability by modifying its physiological performance. Our data provide support for the hypothesis of physiological flexibility in energetic traits and water balance in response to the environmental challenges of the Monte Desert.
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    Thermal constraints on daily patterns of aggregation and density along an intertidal gradient in the periwinkle Echinolittorina peruviana
    (PERGAMON-ELSEVIER SCIENCE LTD, 2008) Munoz, J. L. P.; Camus, P. A.; Labra, F. A.; Finke, G. R.; Bozinovic, F.
    Variations in environmental temperature have both direct and indirect effects that affect organisms at levels ranging from intra-cellular physiological processes to ecological patterns. These variations are especially important for intertidal marine ectotherms such as littorinids since they alternate between periods of immersion in seawater, and must also experience long periods of emersion. In central Chile, Echinolittorina peruviana is one of the most conspicuous species on rocky intertidal shores, occurring at high tidal levels and in the splash zone. The species is known to resist direct exposure to the sun for long periods, although juveniles tend to be restricted to protected microhabitats. Adults show seasonal variations in abundance and vertical distribution and may form aggregations that have been shown to help reduce water loss and body temperature. In this study, we evaluate the relationship between daily thermal variations throughout the vertical distribution of this species and how these affect the patterns of density and aggregation. Our results suggest that one of the leading determinants of the spatio-temporal variation of density in E peruviana may be operative temperature (TO: the amount of stored heat resulting from the balance between heat fluxes into and out of the body, measured with taxidermic mounts mimicking heat transfer properties of the snail). To showed a strong negative relationship with density and a strong positive relationship with aggregation in the highest intertidal level monitored. The strength of these relationships decreased in importance at lower levels. While To alone cannot explain the abundance of E peruviana throughout its range of distribution, our results show that it does have a strong influence that should be considered in addition to other ecological factors affecting the density of intertidal littorinids. (C) 2007 Elsevier Ltd. All rights reserved.