Читать книгу Statistical Approaches for Hidden Variables in Ecology - Nathalie Peyrard - Страница 11

Ecology is the study of living organisms in interaction with their environment. These interactions occur at individual level (an animal, a plant), at the level of groups of individuals (a population, a species) or across several species (a community). Statistics provides us with tools to study these interactions, enabling us to collect, organize, present, analyze and draw conclusions from data collected on ecological systems. However, some components of these ecological systems may escape observation: these are known as hidden variables. This book is devoted to models incorporating hidden variables in ecology and to the statistical inference for these models.

The hidden variables studied throughout this book can be grouped into three classes corresponding to three types of questions that can be posed concerning an ecological system. We may consider the identification of groups of individuals or species, such as groups of individuals with the same behavior or similar genetic profiles, or groups of species that interact with the same species or with their environment in a similar way. Alternatively, we may wish to study variables which can only be observed in a “noisy” form, often called a “proxy”. For example, the presence of certain species may be missed as a result of detection difficulties or errors (confusion with another species), or as a result of “noisy” data resulting from technology-related measurement errors. Finally, in the context of data analysis, we may wish to reduce the dimension of the information contained in data sets to a small number of explanatory variables. Note the shift from the notion of a variable which escapes observation, in the first cases, to a more generalized notion of hidden variables.

All three of these problems can be translated into questions of inference concerning variables which, in statistical terms, are said to be latent. Inference poses statistical problems that require specific methods, described in detail here. The ecological interpretation of these variables will also be discussed at length. As we shall see, while the statistical treatment of these variables may be complex, their inclusion in models is essential in providing us with a better understanding of ecological systems.