Hummingbird and hawkmoth wing shape: Analysing functional convergence in analogous structures

Similar wing planform shapes have independently evolved in both hummingbirds and hawkmoths, indicating convergence. Functional analysis of bird wings has shown that the rigours of flight are a constraining influence on shape, resulting in evolution towards better functioning forms. Shape similarity in these analogous structures may therefore represent convergence upon a more functionally adapted morphology. Using theoretical morphospace, we test the performance of hummingbird and hummingbird-mimicking moth wings with birds and a dataset of other insect groups. When compared with birds, hummingbirds demonstrate a strong functional constraint, though this effect is absent when compared with insects that more closely match their flight mode. The phylogenetic signal of hummingbird wing shapes is minimal, though this result is likely clouded by variation introduced by sexual dimorphism. Evidence of functional constraint in the sampled planforms is small and varies according to taxa, with Macroglossum moths exhibiting the least constraint. This suggests that morphological convergence between hawkmoths and hummingbirds may result from selective pressures external to the functional constraints of flight.