Predation is a powerful selective force shaping many behavioural and morphological traits in prey species. The deflection of predator attacks from vital parts of the prey usually involves the coordinated evolution of prey body shape and colour. Here, we test the deflection effect of hindwing (HW) tails in the swallowtail butterfly Iphiclides podalirius . In this species, HWs display long tails associated with a conspicuous colour pattern. By surveying the wings within a wild population of I. podalirius , we observed that wing damage was much more frequent on the tails. We then used a standardized behavioural assay employing dummy butterflies with real I. podalirius wings to study the location of attacks by great tits Parus major . Wing tails and conspicuous coloration of the HWs were struck more often than the rest of the body by birds. Finally, we characterized the mechanical properties of fresh wings and found that the tail vein was more fragile than the others, suggesting facilitated escape ability of butterflies attacked at this location. Our results clearly support the deflective effect of HW tails and suggest that predation is an important selective driver of the evolution of wing tails and colour pattern in butterflies.

Predation is a powerful selective force shaping many behavioural and morphological traits in prey species. The deflection of predator attacks from vital parts of the prey usually involves the coordinated evolution of prey body shape and colour. Here, we test the deflection effect of hindwing tails in the swallowtail butterflyIphiclides podalirius. In this species, hindwings display long tails associated with a conspicuous colour pattern. By surveying the wings within a wild population ofI. podalirius, we observed that wing damage was much more frequent on the tails. We then used a standardised behavioural assay employing dummy butterflies with realI. podaliriuswings to study the location of attacks by great titsParus major. Wing tails and conspicuous coloration of the hindwings were struck more often than the rest of the body by birds. Finally, we characterised the mechanical properties of fresh wings and found that the tail vein was more fragile than the others, suggesting facilitated escape ability of butterflies attacked at this location. Our results clearly support the deflective effect of hindwing tails and suggest that predation is an important selective driver of the evolution of wing tails and colour pattern in butterflies.

Ecological interactions may fuel phenotypic diversification in sympatric species. While competition can enhance trait divergence, other ecological interactions may promote convergence in sympatric species. Within butterflies, evolutionary convergences in wing color patterns have been reported between distantly-related species, especially in females from palatable species, where mimetic color patterns are promoted by predator communities shared with defended species living in sympatry. Wing color patterns are also often involved in species recognition in butterflies, and divergence in this trait has been reported in closely-related species living in sympatry as a result of reproductive character displacement. Here we investigate the effect of sympatry between species on the convergence vs. divergence of their wing color patterns in relation to phylogenetic distance, focusing on the iconic swallowtail butterflies (family Papilionidae). We developed a new unsupervised machine-learning-based method to estimate phenotypic distances among wing color patterns from 337 species allowing to finely quantify morphological diversity at global scale within and among species, allowing to compute pairwise phenotypic distances between sympatric and allopatric species pairs. We found that sympatry promoted strong convergence, while divergence in sympatry was less frequent and weaker. The effect of sympatry on convergence was stronger on females than males, suggesting that differential selective pressures acting on the two sexes drove sexual dimorphism. Our results highlight the significant effect of ecological interactions driven by predation pressures on trait diversification in Papilionidae and evidence the interaction between phylogenetic proximity and ecological interactions in sympatry acting on macroevolutionary patterns of phenotypic diversification.