Natural selection is the pervasive force shaping the evolution of living organisms. Selection can take several forms—directional, stabilizing, disruptive, indirect—and can act in different ways on different organismal traits.
In recent decades much research has been devoted to measuring the strength of the various types of selection on phenotypes and quantitative traits both in the wild and in the laboratory. Kingsolver et al. analyze this literature and uncover some unexpected patterns. In both vertebrates and plants, the strength of selection on morphological traits was twice as great as on life-history traits; strength of selection on some components of fitness such as fecundity or mating success was greater than on others such as survival; the strength and frequency of stabilizing selection, which keeps a trait constant, was no greater than that of disruptive selection. This synthesis provides a fresh view of the complexities of the evolutionary landscape and of the statistical hurdles that need to be cleared. — AMS
Am. Nat.157, 245 (2001).