Forschung

Sektion Mammalogie

Insular evolution

One of my long term scientific goals is to understand insular evolution and the processes involved. This is best achieved using a cross-disciplinary approach to analyse size, morphology and development of island animals on all organismal levels. My projects so far have focused on various vertebrates using a range of analytical techniques to increase understanding of the combined influence of isolation in a mammalian predator-free environment.

I am currently working on a project on the effects of environment on growth and life history in island taxa. On islands, unbalanced faunas tend to consist of dwarfs and giants. Insular dwarfs have variably been reported to exhibit fast development, slow development or truncation of growth. These modes of dwarfing have different implications for the life history of the animals in question and their morphological plasticity. The modes of dwarfing described above have been found in different species, on different islands, and using different methodologies. It may, thus, be hypothesised that different taxa display a different response to an insular environment or that the difference in environment is the key to the different dwarfing modes. Alternatively, the different interpretations may even represent an artefact caused by the different methodologies. My research is aimed at discerning between these and determining the mode of dwarfing in insular mammals. To attain this goal, teeth and long bones are sectioned for examination under a microscope to determine growth rate and duration.

I am also a member of the Dodo Research Project, which brings together expertise from the Netherlands, the United Kingdom, Mauritius, the United States, Germany and Norway. The dodo (Raphus cucullatus), a large flightless pigeon once endemic to the island of Mauritius, is an icon of human-induced extinction. Unfortunately, very few fragmentary remains exist from specimens collected before the bird’s extinction in the 17th century, and many aspects of dodo anatomy and biology remain poorly known. Within our team, I am responsible for the acquisition and statistical analyses of traditional morphometric data to understand population structure and sexual dimorphism of this enigmatic insular giant.

Furthermore, I work on a project dealing with the skull biomechanics of Haast’s eagle (Harpagornis moorei), an insular giant from New Zealand, in collaboration with the FEAR lab at the University of New England (Australia). Haast’s eagle – an extinct predatory bird from New Zealand estimated to weigh nearly 50% greater than the largest modern eagles – is thought to have been capable of taking down large-bodied prey, including moa (~20-200 kg). We use finite element analysis to assess the mechanical performance of Haast’s eagle relative to some modern eagle and vulture species, during simulations of various killing and feeding behaviours.

Primate and human evolution

There are many hypotheses regarding the evolution of hominin bipedalism and many questions remain. For example, it is not yet clear to which extent and how the rise of bipedalism and tool use may be linked. In other words, were changes in hand morphology adaptations or exaptations for tool use? In human hands and feet, the first digit is longer and more robust compared to the lateral digits than in apes. These human traits may have coevolved in hands and feet due to a shared developmental pattern of these elements; evolutionary changes towards precision grip capabilities involving the thumb in the genus Homo could, therefore, be a by-product of selective pressures on the big toe. The aim of this project is to assess covariation in the phalanges of the hands and feet of modern humans and other primates to assess potential coevolution in these elements. Of special interest are the thumb and the big toe, because of differential selection pressure on the big toe relative to the other toes related to the rise of bipedalism in the human lineage.