Research

My main research interests in the field of ecology and conservation led to a specialisation during my early career in population genetics and biogeography, particularly of invasive species. So far it also has been strongly influenced by ratsy topics. I have been working on all three commensal rat species, Rattus rattus, Rattus exulans, and Rattus norvegicus, that invade pristine environments with the aid of humans. The common result is a severe disturbance of local faunal communities and particulary island communities and endemic species suffer from such invasives.

Besides the insights gained about historic events and timings which can be read from molecular data, knowledge about distribution pathways of these commensals help our understanding of how invasions occur and as such help develop protection schemes. Currently I am involved in an investigation on the Phylogeography of South Atlantic Norway rats, Rattus norvegicus.

Although my ecological interest in biological interrelations was the initial drive for my research, as a molecular geneticist I am deeply intrigued by genetic processes, the workings of DNA and the flexibility of the epigenetic imprint.

PhD Research:

In my PhD research at the University of Auckland, jointly supervised by Dr. Howard Ross, at the Bioinformatics Institute, School of Biological Sciences and Professor Lisa Matisoo-Smith, at the Department of Anatomy at the University of Otago, and generously supported by the Marsden Fund Council from Government funding, administered by the Royal Society of New Zealand, I investigated the population genetics of the Pacific rat, Rattus exulans, the third most widely distributed rat commensal, across its distributional range.

This species is of particular interest because it was a travel companion to a group of explorers who settled the islands of the Pacific Ocean, the last region on earth to be settled by humans. This phase of settlement, commencing around 3500 BP, is marked by the arrival of Oceanic Austronesian speakers from Island Southeast Asia and the appearance of the Lapita cultural complex, including R. exulans, in so called Near Oceania. Roughly, Near Oceania stretches across most small islands between Northern Papua New Guinea and the Solomons. The subsequent settlement of Remote Oceania, most islands in the Pacific beyond the visibility border, meant these explorers had to navigate in rather small canoes across far stretches of open Ocean without any visual contact to land. The Pacific rat (R. exulans, Kiore or Polynesian rat) served as a food item on these voyages and has been used as a proxy for tracing prehistoric human migration within Polynesia, because with this human aid they simultaneously reached every island that was settled during that time.

To test whether these rats can also help untangling the orgins of the Lapita peoples, which is widely discussed among disciplines from Anthropology via Linguistics to Biology, I investigated the population gentetics and dynamics within its current range. Using modern, museum, and archeological samples, requiring ancient DNA techniques, I utilised bayesian coalescent approaches with molecular dating for analyses to differentiate between the influence of a highly variable landscape and human mediation on the distribution of R. exulans. Results provide insight into colonisations of this non-volant small mammal species across water barriers in the species rich archipelago of Island Southeast Asia.

My thesis can be found under the title "Phylogeography of the commensal Rattus exulans with implications for its use as bioproxy for human migrations".

Diploma (Masters Thesis):

In my Diploma thesis, I worked on phylogeographical questions concerning the invasive species Rattus rattus on Madagascar. As part of global environmental change, the impact of invasive species is, next to degradation and destruction of habitats, known to be one of the biggest threats to biodiversity. Since McArthur & Wilson's work, it is a well known fact that island populations are more prone to suffer from such changes and impacts.

My thesis comprised one molecular genetic approach for the description of the genetic differentiation of Rattus rattus on Madagascar and another for the reconstruction of the colonisation pattern in southern Madagascar with special interest in the origin of the introduced species. Concerning these questions I worked with the non-coding hypervariable region 1 (HVR I) of the mitochondrial control region.

For a sample population in an exceedingly fragmented area in southern Madagascar I also analysed the coding DRB Exon2 gene of the major histocompatibility complex (MHC). In addition to the classification of antigen binding sites (ABS) and thus the magnitude of selective mechanisms, I compared the variabilities of the non-coding and coding marker.

The thesis with the title:

“Molekulargenetische Untersuchungen zur Populationsdifferenzierung von Rattus rattus auf Madagaskar”
(Molecular genetic analysis of population differentiation of Rattus rattus on Madagascar)

was submitted at the University of Hamburg, under supervision of Professor Jörg Ganzhorn, Department of Ecology and Conservation and Professor Simone Sommer, now at the Institut of Evolutionary Ecology and Conservation Genomics, University of Ulm.

Financial support: German Research Foundation (DFG) and Volkswagen Stiftung.

CV:

My CV is mailed upon request.