The evolutionary journey of the avian foot through its networks

The avian evolutionary pathway led to morphological adaptive variations in their feet. Diverse foot types are accompanied by a complex muscle system, allowing birds to adopt different primary lifestyles, and to display various locomotor and manipulative skills. We provide novel insights of evolutionary and functional significance on the avian foot architecture through Anatomical Network Analysis. Here we show that there is no link between the more complex foot networks and the ability to perform more specialized skills or a higher number of different tasks. Additionally, there is a trend towards the simplification of foot networks on a microevolutionary scale. The anatomical parts largely conserved in living birds and already present in ancestral dinosaurs exhibit the highest connectivity degree, a network parameter related to the constraint of an anatomical part or evolutionary change. Foot networks are phylogenetically constrained and conserved in all birds despite their foot type diversity. We suggest that this scenario could be the result of stabilizing selection, which led the connectivity of anatomical parts of the foot to be conserved.