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The effect of metamorphosis on the repeatability of maximal locomotor performance in the Pacific tree frog Hyla regilla.
T B Watkins


Measuring the repeatability of inter-individual differences in locomotor performance is an important first step in elucidating both the functional causes and the ecological consequences of performance variation. Thus, repeatability of whole-animal performance traits provides a crucial link between functional and evolutionary biology. In the present study, repeatability of maximal burst locomotor performance was estimated for a single population of the Pacific tree frog Hyla regilla. Animals were reared individually from eggs through metamorphosis in the laboratory. Maximum burst swimming speed of tadpoles was measured before metamorphosis (Gosner stage 37) and again at the onset of the metamorphic climax (stage 42). Maximum jump distance was measured on the same individuals as juvenile frogs. Locomotor performance was repeatable over a 24h period for both premetamorphic tadpoles and juvenile frogs. Performance was not repeatable across metamorphosis or between any two of the three developmental stages investigated. A high-performance individual at one developmental stage does not necessarily retain that performance advantage at another stage. This lack of repeatability contrasts sharply with several previous studies on non-metamorphosing vertebrates, but concurs with a single previous study on a metamorphosing salamander. Metamorphosis appears to place strict temporal constraints on individual consistency in locomotor ability.