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Bettina Wachter Oliver P. Höner Marion L. East Waltraud Golla Heribert Hofer 《Behavioral ecology and sociobiology》2002,52(4):348-356
Avian models of facultative siblicide predict that rates of sibling aggression and the incidence of siblicide should be lower in prey-rich than prey-poor environments, and that siblicide should only occur when fitness benefits outweigh costs. We tested these predictions by comparing data from spotted hyena (Crocuta crocuta) twin litters in the Ngorongoro Crater, Tanzania, a habitat with a high density of resident prey (176 animals/km2) with similar data from the adjacent Serengeti National Park where density of resident prey is low (3.3 animals/km2). As predicted, rates of sibling aggression in Crater twin litters were substantially lower than those among twin siblings in the Serengeti. There was no evidence of siblicide in the Crater, in contrast to the Serengeti, where facultative siblicide occurs frequently. The growth rate of Crater cubs in singleton litters was similar to that of cubs in twin litters, whereas the growth rate of Serengeti singletons was higher than that of cubs in twin litters. Thus despotic behavior by dominant Crater cubs was unlikely to provide fitness benefits, while dominant Serengeti cubs that eliminated their sibling benefited from increased growth and enhanced survival. Previous studies have demonstrated biases in the sex-composition of hyena litters due to facultative siblicide. No such biases were apparent in Crater litters. Our results provide strong evidence that levels of sibling aggression in spotted hyenas are adjusted in an adaptive manner, and that siblicide is facultative and resource dependent. Our results do not support the idea of pre-natal manipulation of offspring sex by female spotted hyenas in response to changes in resource abundance. 相似文献
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In the conceptualization of thriving at work, it is emphasized that employees' learning and vitality are two equally important components of thriving and that thriving is facilitated by contextual features and available resources. In this study, we examined the effects of two challenge stressors (time pressure and learning demands) on thriving at work. Based on the literature on challenge and hindrance stressors, we proposed that challenge stressors positively affect learning and negatively affect vitality. To uncover underlying mechanisms, we measured challenge appraisal and hindrance appraisal of work situations in a diary study. A sample of 124 knowledge workers responded to three daily surveys (before the lunch break, during the afternoon, and at the end of the workday) for a period of five workdays. Results indicate that the indirect effects of learning demands and time pressure on learning are mediated by challenge appraisal, whereas indirect effects of learning demands on vitality are mediated by hindrance appraisal. Overall, our study shows that challenge stressors have a positive total effect on learning but no total effect on vitality. These differential relationships call for a finer distinction between the two components of thriving at work in future research. Copyright © 2016 The Authors Journal of Organizational Behavior Published by John Wiley & Sons Ltd. 相似文献
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Céline Dupont Francesca Romana Grati Kwong Wai Choy Sylvie Jaillard Jérôme Toutain Marie-Laure Maurin Jose Antonio Martínez-Conejero Claire Beneteau Aurélie Coussement Denise Molina-Gomes Nina Horelli-Kuitunen Azzedine Aboura Anne-Claude Tabet Justine Besseau-Ayasse Bettina Bessieres-Grattagliano Giuseppe Simoni Gustavo Ayala Brigitte Benzacken François Vialard 《黑龙江环境通报》2015,35(1):35-43
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This study presents a meta-analysis of a collective dataset describing the succession from abandoned fields to semi-natural
grassland and heathland vegetation over the past century. The study objectives were to develop a method for statistical discrimination
between abandoned fields and semi-natural habitats and to analyze the probability that an abandoned field had developed into
a semi-natural habitat. A statistical classification model was developed, based on lists of vascular plants from 2059 plots
from Danish semi-natural grasslands and heathlands, and abandoned fields of varying age. This model was shown to discriminate
effectively between abandoned fields and semi-natural habitats, and it was found to be potentially useful for the detection
of abandoned fields approaching semi-natural vegetation. We suggest that the model may help clarify restoration targets and
assess biological condition in formerly cultivated areas. Statistical modeling revealed that succession age, period of abandonment
and succession trajectory had significant effects on the probability that abandoned fields reached the semi-natural phase.
Our study indicates that restoration projects targeting grassland and heathland should take local species pools and soil fertility
into account.
Nomenclature: Species names follow Flora Europaea (Tutin and others 1964–1993). 相似文献