Evolution of the jaw apparatus in true woodpeckers (Picidae: Picinae) in association with the available food sources and foraging habits

Abstract

The evolution of woodpecker behaviors in association with their morphological adaptations is not well understood. This investigation aimed to determine the relationship between the anatomy of the jaw apparatus, the type of food consumed and the foraging mode of these birds. We present detailed anatomical descriptions of all parts of the jaw apparatus of true woodpeckers. Their characteristics were mapped into a consensus phylogenetic tree to describe woodpecker evolution. When morphological analyses were associated with feeding/foraging behavior, distinct patterns emerged. The protractor quadrati and pterygoideus systems are more developed in species that adopt pecking/hammering behaviors, even as secondary habits. By comparing Hemicircus (frugivorous with a poorly developed jaw apparatus) with the last common ancestor of Picinae, the early evolution of the jaw apparatus was found to be related to the type of food consumed. However, it became more complex in the ancestral lineage of Picinae, which enabled these birds to catch insects by gleaning/probing. It is hypothesized that the jaw apparatus of Picinae has evolved in response to foraging tactics and not to the type of food consumed. Pecking/hammering, as a secondary behavior, has evolved independently in Dryocopus, Celeus, and Dendropicus. Moreover, it has become more complex in Piculus and the clade comprising Blythipicus/ Reinwardtipicus/Camphephilus, as they utilize pecking/hammering as their primary behavior.