Parameters of the adhesive setae and setal fields of the Jamaican radiation of anoles (Dactyloidae: Anolis): potential for ecomorphology at the microscopic scale

The subdigital adhesive pads of Caribbean Anolis lizards are considered to be a key innovation that permits occupation of novel ecological niches. Although previous work has demonstrated that subdigital pad morphology and performance vary with habitat use, such investigations have only considered the macroscale aspects of these structures (e.g. pad area). The morphological agents of attachment, however, are arrays of hair-like fibres (setae) that terminate in an expanded tip (spatula) and have not been examined in a similar manner. Here we examine the setal morphology and setal field configuration of ecologically distinct species of the monophyletic Jamaican Anolis radiation from a functional and ecological perspective. We find that anoles occupying the highest perches possess greater setal densities and smaller spatulae than those exploiting lower perches. This finding is consistent with the concept of contact splitting, whereby subdivision of an adhesive area into smaller and more densely packed fibres results in an increase in adhesive performance. Micromorphological evidence also suggests that the biomechanics of adhesive locomotion may vary between Anolis ecomorphs. Our findings indicate that, in a similar fashion to macroscale features of the subdigital pad, its microstructure may vary in relation to performance and habitat use in Caribbean Anolis.