Introduction to Part A

Local changes in biodiversity happen through migration or speciation and through extinctions. The latter have been at the focus of conservation biology since the field's inception, and the purpose of this opening part is to review the rich theoretical foundations for our understanding of population extinction.

Specifically, we aim to understand how mechanisms that operate at the level of individuals scale up to the dynamics of populations and thus determine extinction risks. In the context of evolutionary conservation biology, this step is necessary to identify potential targets that impact on population viability. Such targets include classic life-history traits (e.g., demographic parameters such as survival probabilities, fecundity, or age at maturity) and behavioral traits that determine the effective interactions between individuals (e.g., propensities to move or migrate, competitive ability, or mate choice).

Connecting individual characteristics to population properties is also necessary to understand the origin of the selective pressures by which populations exert a feedback to individuals. Adaptive evolution usually proceeds by small steps: new phenotypes arise from mutation or recombination, and the individuals thus affected must compete with their conspecifics. Questions of viability and extinction are therefore important to address in assessing whether evolutionary innovations are retained through the persistence of their carriers or, instead, are eliminated through their extinction.

The theoretical material in this part should also be relevant to investigators with a primary interest in population viability analysis (PVA).