Data from: Levers and linkages: Mechanical trade-offs in a power-amplified system

Mechanical redundancy within a biomechanical system (e.g., many-to-one
mapping) allows morphologically divergent organisms to maintain equivalent
mechanical outputs. However, most organisms depend on the integration of
more than one biomechanical system. Here we test whether coupled
mechanical systems follow a pattern of amplification (mechanical changes
are congruent and evolve towards the same functional extreme) or
independence (mechanisms evolve independently). We examined the correlated
evolution and evolutionary pathways of the coupled 4-bar linkage and lever
systems in mantis shrimp (Stomatopoda) ultrafast raptorial appendages. We
examined models of character evolution in the framework of two divergent
groups of stomatopods – “smashers” (hammer-shaped appendages) and
“spearers” (bladed appendages). Smashers tended to evolve towards force
amplification, while spearers evolved towards displacement amplification.
These findings show that coupled biomechanical systems can evolve
synergistically, thereby resulting in functional amplification rather than
mechanical redundancy.