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1 Natural selection is generally thought to operate on organisms’ maximal abilities to perform ecological tasks in nature (i.e. whole-animal performance). However, selection may instead operate on the manner in which that performance trait is used (i.e. ‘ecological performance’). 2 I tested whether survival of adult Collared Lizards (Crotaphytus collaris) depended on maximal sprint speed capacity or on the speed at which they actually performed two important ecological tasks: chasing a prey item and escaping a predator. 3 Maximal sprint speed did not significantly predict annual survival as determined by daily censuses of the site the following season, nor did speed while foraging, but speed while escaping a predator did. Survival also was positively related to the proportion of maximal capacity used while escaping. 4 These results suggest that selection may operate on ecological performance that is constrained, but not necessarily determined, by maximal performance capacity, suggesting that researchers should consider how organisms utilize maximal performance in nature when testing for a performance–survival relationship.
Jerry F. Husak (Fri,) studied this question.