Promoters: Leonard Dewaele, Jamie MacLaren, Sam Van Wassenbergh
Subject: Pinnipeds (seals and sea-lions) are well known among carnivorans for exhibiting notable examples of sexual dimorphism. However, true seals (Phocidae) generally show little by way of sexual dimorphism compared to fur-seals or sea lions (Otariidae). Sexual dimorphism in phocids is generally limited to small differences in size between males and females, rather than wholesale differences in cranial or postcranial morphology. One genus of true seal shows a remarkably strong sexually dimorphic signal: Cystophora, the hooded seal. The sexual dimorphism in this species manifests in the presence of a fleshy proboscis in males, which has historically been used as a phylogenetic character uniting hooded seals with elephant seals (Mirounga). A morphometric analysis of the skull of Cystophora will yield valuable insights into how the proboscis develops and how the skulls of males and females differ. Moreover, such a study will also demonstrate how the skull becomes adapted to different lifestyles through ontogeny.
Materials and methods: A large database of 3D scanned models of Cystophora skulls has been compiled, comprehensively covering both sexes and multiple ontogenetic stages. No fieldwork or museum visits are strictly necessary; however, the supervisors intend to familiarize the student with scanning procedures and postprocessing the data to create 3D models of a target object. Morphometric methods (linear and geometric morphometrics) will be used to study the variation and changes in shape of the skull; these will be implemented through the R statistical environment. Other software will be used as well at various steps in the project, all of which are at the students disposal during the project.
Student profile: The ideal student should have a basic understanding of mammalian biology, and be familiar with evolutionary processes (e.g. sexual selection) and phylogenetics. Specific knowledge about morphometric analyses is beneficial, but not essential. Familiarity with the R statistical environment will be necessary, although all statistical and analytical steps will be performed in consultation with the main supervisor.