The gambin model provides a superior fit to species abundance distributions with a single free parameter : evidence, implementation and interpretation

The species abundance distribution (SAD) has been a central focus of community ecology for over fifty years, and is currently the subject of widespread renewed interest. The gambin model has recently been proposed as a model that provides a superior fit to commonly preferred SAD models. It has also been argued that the model's single parameter (α) presents a potentially informative ecological diversity metric, because it summarises the shape of the SAD in a single number. Despite this potential, few empirical tests of the model have been undertaken, perhaps because the necessary methods and software for fitting the model have not existed. Here, we derive a maximum likelihood method to fit the model, and use it to undertake a comprehensive comparative analysis of the fit of the gambin model. The functions and computational code to fit the model are incorporated in a newly developed free-to-download R package (gambin). We test the gambin model using a variety of datasets and compare the fit of the gambin model to fits obtained using the Poisson lognormal, logseries and zero-sum multinomial distributions. We found that gambin almost universally provided a better fit to the data and that the fit was consistent for a variety of sample grain sizes. We demonstrate how α can be used to differentiate intelligibly between community structures of Azorean arthropods sampled in different land use types. We conclude that gambin presents a flexible model capable of fitting a wide variety of observed SAD data, while providing a useful index of SAD form in its single fitted parameter. As such, gambin has wide potential applicability in the study of SADs, and ecology more generally.

Silence in organizations and psychological safety : a literature review

In the business world, employees can contribute with information, ideas, concerns, opinions and proposals to their managers in respect of: (1) the way work could be performed, (2) what should / should not be done in the workplace, (3) how a particular decision can be implemented, and (4) how an organizational policy should be formed and executed (Rego, 2013). However, due to a diverse set of factors, employees often choose to remain silent in the workplace. One of these factors is psychological safety, which describes employees’ perceptions of the consequences of taking interpersonal risks in the workplace (Edmondson, 2014). The following paper is essentially a literature review and its aim is to, firstly, make a brief approach to factors reported in the literature that may affect employee voice and silence, followed up by an explanation of the types of silence that can be engaged by employees. Besides that, the authors will also make an approach to physical and psychological safety. Lastly, it will be reported some links, mentioned in the literature, between employee silence and psychological safety.