On the origin of frictional adhesion in geckos: small morphological changes lead to a major biomechanical transition in the genus Gonatodes

The evolutionary history of vertebrate locomotion is punctuated by innovations that have permitted expansion into novel ecological niches. Frictional adhesion of geckos is an innovation renowned for enabling locomotion on vertical and inverted smooth surfaces. Much is known about the microstructure and function of the fully‐expressed gekkotan adhesive apparatus, although how it originated is poorly understood. Therefore, identifying species that exhibit the earliest stages of expression of frictional adhesion will provide significant insights into the evolution of this trait. Our previous investigation of digital proportions, shape, scalation, skeletal form, and subdigital epidermal micro‐ornamentation in the genus Gonatodes led us to hypothesize that Gonatodes humeralis expresses incipient frictional adhesion. To test this, we first conducted a phylogenetic analysis of Gonatodes and related sphaerodactyl genera to clarify the historical context of the evolution of frictional adhesive capability in the genus. We then measured the ability of G. humeralis and its close relatives to generate frictional adhesive force, examined their locomotor capabilities on low‐friction surfaces, and observed animals in their natural habitat. After accounting for body mass and phylogenetic relationships, we found that G. humeralis generates frictional adhesive force essentially equivalent to that of Anolis, and can scale vertical smooth surfaces. Gonatodes vittatus, a species that lacks...
Source: Biological Journal of the Linnean Society - Category: Research Authors: Tags: Research Article Source Type: research