Functional and evolutionary synergy of trait components can explain the existence of leaf masquerade in katydids

One of the most enduring mysteries in biology concerns the evolution of complex adaptations made up of interacting component traits. When these component traits do not enhance fitness independently of one another, their origin requires that they evolve sequentially through intermediate steps that do not produce their full adaptive value as a combined trait, or alternatively, that they arise via simultaneous, synergistic evolution. We tested these alternatives using the powerful but accessible example of leaf masquerade in katydids, where in some species, highly modified wings strikingly mimic vegetation to avoid predator recognition. Combining a field predation experiment with a phylogenetic comparative analysis of wing morphology in 58 Neotropical katydid species, we show that color and shape synergistically interact to enhance survival in the wild, and modifications in both traits evolved concurrently during diversification of this clade. Our findings identify the adaptive value of masquerade camouflage in the wild and show how concordant evolutionary change in separate traits—evolutionary synergy—can generate extraordinarily specialized, multi-component adaptations.