On the Origins and Dynamics of Biodiversity: the Role of Chance

What are the origins of chance? Although its existence has long been accepted as a fact, the theory of probability only allows us to examine the random events produced by chance without enabling us to determine what creates it - and this despite knowing that living systems (from the cell to organisms, populations, communities and ecosystems) need chance to survive. In this book on living systems, we identify two origins: one external, coming from the environment, and the other, internal, produced by biological mechanisms that are molecular as well as cellular, demographic and ecological. These internal mechanisms - veritable "biological roulettes" - are similar to the mechanical devices that bring about "physical chance". They are at once the products and the engines of evolution and they also generate biodiversity, often in response to the vagaries of the environment. By creating biodiversity, these biological roulettes act as a kind of a life insurance that, on an evolutionary scale, ensure that life will continue after great upheaval: within the wide variety of organisms, there are some that are potentially adapted to new environmental conditions. From among those that survive, a new living world will grow and diversify. By examining biodiversity at all scales and all levels, this book seeks to evaluate the breadth of our knowledge on this topical subject; to propose an integrated look at living things; and to assess the role of chance in the dynamics of biodiversity, from populations to ecosystems and the biosphere, and more generally in evolutionary processes. Finally, it suggests that by simultaneously examining the mechanisms of diversification, maintenance and extinction, we can model the dynamics of biodiversity to better understand it and predict its variations and, thus, to foresee the practical aspects for managing living systems.

Résumé
Chance is necessary for living systems from the cell to organisms, populations, communities and ecosystems. It is at the heart of their evolution and diversity. Long considered contingent on other factors, chance both produces random events in the environment, and is the product of endogenous mechanisms - molecular as well as cellular, demographic and ecological. This is how living things have been able to diversify themselves and survive on the planet. Chance is not something to which Life has been subjected; it is quite simply necessary for Life. The endogenous mechanisms that bring it about are at once the products and the engines of evolution, and they also produce biodiversity. These internal mechanisms veritable biological roulettes - are analogous to the mechanical devices that bring about physical chance. They can be modeled by analogous mathematical equations. This open the way of a global modeling of biodiversity dynamics, but we need also to gather quantitative data in both the laboratory setting as well as in the field. By examining biodiversity at all scales and all levels, this book seeks to evaluate the breadth of our knowledge on this topical subject, to propose an integrated look at living things, to assess the role of chance in its dynamics, in the evolutionary processes and also to imagine practical consequences on the management of living systems.

Contenu
Questioning Chance.- Chance in Living Systems.- Lessons for Managing Living Systems.- The Contribution of Models and Modelling: Some Examples.- Biodiversity and Ecological Theories.- Chance and Evolution.- Evaluating Biodiversity: The Example of French Guiana.- Conclusion.