A critique of methods for measuring life history trade‐offs

Abstract Constraints have important effects on the evolution of life history strategies, but several difficulties have been encountered in determining constraints empirically. Here we investigate methods for measuring a specific type of constraint known as a trade‐off. A trade‐off between two traits implies a perfect negative correlation between the traits. Trade‐offs may involve more than two traits, however, and pairs of traits involved in such a higher‐dimensional trade‐off may be positively correlated. If some of the traits involved in a trade‐off are omitted from the experimental design, the trade‐off may not even be detectable. Direct measures of trade‐offs are thus complicated, and indirect means of identifying trade‐offs may often provide the only feasible measures.