Adaptive evolution of flight in Morpho butterflies

The diversity of flying animals suggests that countless combinations of flight morphologies and behaviors have evolved with specific lifestyles, thereby exploiting diverse aerodynamic mechanisms. How morphology, flight behavior and aerodynamic properties together diversify with contrasting ecology remains to be elucidated. We studied the adaptive co-divergence in wing shape, flight behavior and aerodynamic efficiency among Morpho butterflies living in different forest strata, by combining high-speed videography in the field with morphometric analyses and aerodynamic modelling. By comparing canopy and understory species, we show that adaptation to an open canopy environment resulted in increased glide efficiency. Moreover, this enhanced glide efficiency was achieved by different canopy species through distinct combinations of flight behavior, wing shape and aerodynamic mechanisms, highlighting the multiple pathways of adaptive evolution.

Methods
The flight of 11 species of Morpho butterflies was quantified with high-speed stereoscopic videography in a large outdoor insectary (semi-field condition). A range of flight parameters was extracted from the three-dimensional flight trajectories.

Morphological measurements were performed on the studies specimens.

The aerodynamic performance during gliding flight was measured using Computational Fluid Dynamic simulations for 7 Morpho species.