The paradox of the weakening combatant: trade‐off between closing force and gripping speed in a sexually selected combat structure

摘要: Summary 1. Previous evidence demonstrates that closing force decreases proportionally as fiddler crab claw size increases. Larger crabs do have greater absolute force, but less than would be expected if proportions were isometric. In the Mud Fiddler Crab, Uca pugnax , this is explained by a decrease in mechanical advantage with increasing size. 2. We here re-measure more direct method used previously; relationship of to was similar older indirect measure. Because simple lever, we predicted observed decline should compensated proportional increase speed. 3. tested hypothesis using high-speed video observe their major claws spontaneously under controlled conditions. Closing speed scaled positively length predicted, and value exponent conformed expectation from biomechanical model. 4. Evolution therefore involved trade-off for An adaptive explanation relative weakening body may lie increased ability rapidly grasp an opponent, crucial combat.