R/K Selection Theory - Overview

Overview

In r/K selection theory, selective pressures are hypothesised to drive evolution in one of two generalized directions: r- or K-selection. These terms, r and K, are drawn from standard ecological algebra, as illustrated in the simplified Verhulst model of population dynamics:

where r is the maximum growth rate of the population (N), and K is the carrying capacity of its local environmental setting, d stands for derivative, and t for time (i.e. the equation describes the change in time of the population, N). As the name implies, r-selected species are those that place an emphasis on a high growth rate, and typically exploit less-crowded ecological niches and produce many offspring, each of which has a relatively low probability of surviving to adulthood (i.e. high r, low K). By contrast, K-selected species display traits associated with living at densities close to carrying capacity, and typically are strong competitors in such crowded niches that invest more heavily in fewer offspring, each of which has a relatively high probability of surviving to adulthood (i.e. low r, high K). In the scientific literature, r-selected species are occasionally referred to as "opportunistic", while K-selected species are described as "equilibrium".