Figure 4.

A phenotypic trait in an individual may be determined by a range of factors, including the individual's genotype and environmental variation; these effects are depicted by single-headed arrows. The diagram represents a scenario whereby both the trait of interest (such as body size) and a component of fitness change in a correlated manner owing to temporal variation (both within or between years), generating a statistical correlation between trait and fitness depicted by the double-headed purple arrow. The net result is a phenotypic covariance between trait and fitness, and hence the appearance of selection, but no potential for any evolutionary response. After [14,15], but considering, in particular, the confounding effects of temporal variation. (Online version in colour.)