Biogeographic Analysis Using Geometric Morphometrics: Clines in Skull Size and Shape in a Widespread African Arboreal Monkey

Abstract

Despite the “renaissance” of biogeography in the last two decades with its central role in the study of biodiversity and evolution, and the “revolution” in morphometrics brought about by methods based on the analysis of Cartesian coordinates of anatomical landmarks, the use of geometric morphometrics in biogeographic studies has been rather limited. With this analysis we aim to provide an example of how geometric morphometrics can fruitfully be applied to the study of clinal variation in a widespread African monkey group by a simple extension of methods widely employed by macroecologists and biogeographers to multivariate shape data. Throughout the paper we aim to explain these techniques so that those who are new to them can use and adapt them for their own needs, in some cases providing specific instructions on how to perform certain operations in standard morphometrics and statistical software. Our hope is that this may stimulate morphometricians and scientists from other disciplines to explore geographic variation in size and shape using up-to-date geometric morphometric methods. The application of geometric morphometrics to ecological, biogeographic and phylogeographic studies has enormous potential for a thorough understanding of how form changes in space and time during evolution and in relation to genetic and environmental factors.