Worker reproduction in the ponerine ant Ophthalmopone berthoudi: an alternative form of eusocial organization

Summary Colonies of the ponerine Ophthalmopone berthoudi were collected throughout the year. The queen caste is absent. Dissection of large numbers of workers revealed that many of them (up to 100 in one nest) are inseminated and produce eggs. The ovaries are small and contain very few mature oocytes, indicating that there is a slow rate of egg-laying. Workers are produced throughout the year, and all are capable of becoming functional reproductives. However, only those that are sexually-attractive during the limited period of male activity become mated. Thus the percentages of mated laying workers (=gamergates) fluctuate seasonally (Fig. 2). Successive generations of gamergates do not overlap. Observation of nests in the field and in the laboratory indicated that gamergates were never active above ground. There is no aggression between them, and their numbers are not socially regulated. There are few interactions between gamergates and non-reproductive workers, and the former do not acquire more food during termite meals. The notion of parental oppression is undermined by the complete loss of the meen caste, while the nature of the breeding system of this ant leads to the prediction of low relatedness between nestmates.     

Incorporation of pesticides by soil micro-organisms as a way of bound residues formation

We studied the ¹⁴C-tagged biochemical compartments such as proteins, lipids and polysaccharides from bacterial and fungal cultures supplied with ¹⁴C-pesticides and ¹⁴C-glucose. We showed that ¹⁴C incorporation depends both on the substrate structure and on the nature of the micro-organism. Both bacterial and fungal cells incorporated glucose ¹⁴C mainly into cell wall proteins. By contrast, glyphosate ¹⁴C was mainly incorporated into cytoplasm carbohydrates by fungi. On the other hand, 2,4-dichlorophenoxyacetic acid ¹⁴C was mainly found in the carbohydrate fractions of the bacteria walls.     

Modelling Ecological Presence–absence Data along an Environmental Gradient: Threshold Levels of the Environment

A methodology for estimating environmental thresholds of binary presence–absence data is presented where the level of the threshold is parameterised. Presence–absence data is fitted to three complementary different models: an independent null-model, a monotonically increasing or decreasing model, and an optimum model. The range of the three models is strictly between zero and one and the models are therefore well suited for modelling presence probabilities. The results of the three models may be combined by using Bayesian model selection methodologies. The proposed methodology is exemplified on observed binary presence–absence data of Bauera rubioides along an elevation gradient. Received: May 2005 / Revised: July 2005 An erratum to this article is available at.     

Automatic construction of concept hierarchies: The case of foliage-dwelling spiders

In this paper, we present the hierarchical variable dependencies that were obtained from raw data with the use of two machine learning techniques on an ecological data set. The data set contains features of field margins and the corresponding number of spider species inhabiting them. This data set was used before by domain experts to construct a fuzzy qualitative model with hierarchical variable dependencies, which we use for comparison with our results. One of the machine learning methods constructs a hierarchical structure similar to the one in the experts’ model, while revealing some additional interesting relations of environmental features with respect to the number of spider species. The other method constructs a different hierarchy from the one proposed by the experts, which, according to our classification performance experiments, might be even more appropriate.     

Thriving on challenge stressors? Exploring time pressure and learning demands as antecedents of thriving at work

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.