Pace-of-Life Syndrome (POLS): Evolution of the Concept
Nina A. Vasilieva
Abstract
Abstract The pace-of-life syndrome (POLS) hypothesis is a recent but very influential concept in life-history theory. Due to the extreme progress in research in POLS over the last decade, a review of the origin and development of this concept is topical. The roots of the POLS hypothesis go back to the r/K selection theory of MacArthur and Wilson, authors of the first idea of predictable correlations among life-history traits. Following r/K selection theory, the idea of a fast–slow life-history continuum appeared in ecology, suggesting that life-history traits covaried and formed axes from fast to slow life histories. Species physiology was soon incorporated into the fast–slow continuum theory. Thus, animal species were supposed to vary from fast species with an early development and maturation, a high rate of metabolism, a high mortality, and a short lifespan to slow species with a late development, a low metabolic rate, and a long lifespan. The theory was well supported by empirical studies in various animal species. In parallel, the concept of personality emerged in behavioral studies. The concept suggested consistent and predictable between-individual variations in behavioral phenotypes formed by syndromes of various correlated behavioral traits. More recently, the concepts of personality and fast–slow life-history continuum formed the joint and more complex POLS idea of a multivariate adaptive integration of behavior, life history, and physiology among individuals within and between species. The POLS concept suggests that various traits form a continuum from aggressive, bold, active explorers with fast life histories to shy, nonaggressive individuals with low exploration outfits and a slow life. The predictions were tested in numerous studies, and empirical data have extended the basic idea of pace-of-life: the relationships appeared to be more complex and multidimensional. The POLS hypothesis presently includes covariations among life-history, behavior, immunity, hormones, and metabolic rates, with these relationships being modulated by the environment, development, population density, and social conditions. The POLS ideas, being of great applied and theoretical significance, and long-term empirical studies in the wild populations are in high demand.