The Importance of Effective Population Size in Conservation and Biodiversity Monitoring

ABSTRACT Effective population size ( N e ) is a key concept in biology and conservation. Stripped to its bare essentials, it reflects how much genetic drift a population experiences, expressed as a number of individuals of an ideal theoretical population. Superficially, N e seems like a fairly simple concept, but the more layers of the onion you peel, the more you feel like crying. Really understanding N e in all its facets is daunting, as there are various temporal, spatial, biological, and mathematical ways in which N e can be defined and approached, many of which are erroneously interchanged and often not distinguished. If that is not enough, understanding the intricacies and the assumptions of the many ways in which N e can be calculated is required to make sense of the concept. This is why a special issue on this topic, especially in relation to biodiversity monitoring, is timely. We assembled 19 original papers, perspectives, and reviews on effective population size estimation in relation to conservation to help practitioners in conservation research and practical management see the forest for the trees with regards to N e .