Can semicircular canal shape predict ecology?

The semicircular canals, found in the inner ear of all jawed vertebrates, are a significant functional component of the sense of balance, providing sensory feedback when the head is rotated. The morphology of these canals has been shown to have strong ties with the lifestyle and locomotion of mammals, particularly locomotory specialists such as the quick and agile gibbon or the slow and deliberate sloth. Understanding how the morphology of these canals evolves in living species enables us to infer locomotory and ecological characteristics of fossil species. To date, however, this system has been little explored outside the Mammalia, making it difficult to reconstruct the ecology of non-mammalian fossil species. This project aims to remedy this by characterizing the morpho-functional evolution of the semicircular canal system in the charismatic Caribbean lizards, Anolis. Over the last few decades, anoles have proven to be as significant a model group for understanding evolution as Darwin’s Finches. Of most importance to this research, anoles have been shown to encompass a high level of phylogenetic diversity, but with strongly constrained morphologies that fall within several distinct ecological niches. Using µCT scan data of skulls and 3D geometric morphometrics we are quantifying the extent of semicircular canal morphological variation within and among populations of distinct ecomorphs from the four main islands of the Greater Antilles. Moreover, we are also examining the canal morphology of 15-20my old fossil Anolis species preserved in amber to infer possible ecological characteristics and affinities to modern ecomorph groupings.

Graduate researcher: Blake Dickson     

Collaborators: Jonathan Losos (MCZ) and Emma Sherratt (University of New England)

 

3D reconstruction of the skull (transparent) and right semicircular canal (purple) of Anolis angusticeps.