Recruitment

© 2008 Elsevier B.V. All rights reserved. Recruitment, the addition of new individuals to populations, is a fundamental process in population dynamics. Recruitment usually includes three main stages - the production of propagules, their survival, and their settlement. Recruitment is typically highly variable both in time and space, in response to a large range of biotic and abiotic factors. The contribution of variation in recruitment to changes in population abundance is scale dependent, species specific, and context specific. Consequently, recruitment is often more variable than other demographic processes. Over the short term, variation in recruitment has immediate numerical effects by changing population size. In structured populations, temporal variation in recruitment also affects population structure for several years, which in turn influences population abundance over the longer term. In addition, variation in individual quality of recruits from different cohorts can generate delayed effect on population dynamics. Despite many studies on terrestrial vertebrates, fish, marine invertebrates, annual and perennial plants, our understanding of why recruitment varies in space and time, and of its relative contribution to population changes, is still limited and requires further investigation.