Meeting Abstract
An evolutionary perspective on gecko adhesion was previously hampered by a lack of an explicit phylogeny for the group and of robust comparative methods to study trait evolution, an underappreciation for the taxonomic and structural diversity of geckos, and a dearth of fossil evidence bearing directly on the origin of the scansorial apparatus. With a multigene dataset as the basis for a comprehensive gekkotan phylogeny and the recognition that geckos comprise perhaps the most species-rich group of squamates, model-based methods have recently been employed to estimate the number of unique derivations of the adhesive system and its role in lineage diversification. However, a lack of resolution in parts of the tree and differences in assumptions and analytical approaches has led to differing conclusions. Evidence points to a single basal origin of the spinulate Oberhäutchen, which is a necessary precursor for the subsequent elaboration of a functional adhesive mechanism in geckos, but multiple gains and losses of the fully manifested scansors. Both time-calibrated trees and recently discovered amber fossils that preserve gecko toepads suggest that a fully-functional adhesive apparatus was not only present, but represented by diverse architectures by the mid-Cretaceous. Genomic approaches hold the promise of both further resolving gekkotan relationships and identifying the underpinnings of structural elaborations of gecko keratins. Further characterization and phylogenetically-informed analyses of the other components of the adhesive system (muscles, tendons, blood sinuses, etc.) will also permit a more comprehensive reconstruction of the evolutionary pathway(s) by which geckos have achieved their structural and taxonomic diversity.
