Biological carryover effects: Linking common concepts and mechanisms in ecology and evolution

The term 'carryover effect' originally arose from repeated measures clinical experiments. However, the term has more recently been applied to ecological and evolutionary studies, often in migratory systems, which has led to an emphasis on non-lethal effects across seasons. In this article, we suggest that ecological carryover effects can also occur between life-history stages, developmental stages, physiological states, or social situations, and each will be associated with a discrete time-scale. Therefore, we propose the working definition: In an ecological context, carryover effects occur in any situation in which an individual's previous history and experience explains their current performance in a given situation. This concept of carryover effects provides an explicit but highly flexible context for examining the mechanisms that drive non-lethal interactions between distinct periods of an organism's lifetime, and unites the currently disparate fields investigating these effects in ecological systems. Greater communication among research fields and identifying mechanisms of carryover effects at different time scales will ultimately lead to a better understanding of the factors influencing variation in individual fitness.