Extraordinary adaptations: Functional and evolutionary synergy of trait components can explain the existence of leaf masquerade

Abstract

One of the most enduring mysteries in biology concerns the evolution of complex adaptations made up of interacting component traits. When these component traits lack an obvious adaptive function in isolation from one another, their origin requires either non-adaptive, intermediate evolutionary steps or their 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 51 Neotropical katydid species, we show that colour 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 functionality of masquerade camouflage in the wild and highlight how synergy between individual traits fosters evolution of extraordinarily specialised adaptations.