Meeting Abstract

P1.83  Friday, Jan. 4  Geometric morphometric analysis of varanid skulls reveals comparable disparity among regions despite varying species diversity FERRER, E; Univ. of California, Berkeley eferrer@berkeley.edu

Extant Varanus are widespread in the Old World, but the geographic origin of the group is in question. The oldest known Varanus comes from the Late Eocene-Early Oligocene of Africa, with older varanoids in Asia, but present species diversity is highest in Indo-Asia and Indo-Australia. Recent molecular evidence shows some support for an Asian origin of monitor lizards. Although they are fairly conservative in morphology, varanids encompass a wide range of habitats and ecologies everywhere they are found. The main question of this study was whether low species diversity in African varanids translates to low morphological disparity as well. I conducted an exploratory analysis using geometric morphometrics to quantify the variation in the skulls of 25 species from African, Indo-Asian, and Indo-Australian regions. I photographed and landmarked 122 images of the skulls in several orientations using tpsDig to allow future comparison to fossil material. With the programs MorphoJ and R, I conducted a Procrustes superimposition and then ran principal component (PCA), canonical variate (CVA), and partial disparity analyses of species and regional groups. Based on the PCA and CVA analyses, African varanids encompass a large range of variation. They are generally situated in the middle of varanid morphospace, but they are also distinct when compared to monitors from other regions. There is considerable shape variation within varanids, although species such as V. komodoensis and V. exanthematicus expand the range of shape space greatly. Varanids from each of the main regions form closely related clades, but the species-poor African group still fills a substantial subset of the morphospace, indicating no lack of disparity relative to the overall shape space.