Disputation: Franziska Franeck
Doctorial Candidate Franziska Franeck at Natural History Museum will be defending the thesis Perspectives on the Great Ordovician Biodiversification Event: local to global patterns.
The PhD defence will be streamed directly using Zoom. The host of the session will moderate the technicalities while the chair of the defence will moderate the disputation.
Ex auditorio questions: the chair of the defence will invite the audience to ask ex auditorio questions either written or oral. This can be requested by clicking 'Participants -> Raise hand'.
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Paleobiogeography and plate tectonics.
Main research findings
About 467 Million years ago, during a geological period called the Ordovician, biodiversity increased dramatically. Multiple hypotheses exist about potential causes and underlying mechanisms for this increase. However, observed biodiversity is a balance of origination and extinction and it is biased by preservation and sampling. Therefore, we need to understand these individual components of diversification, before testing specific causal hypotheses.
This thesis quantifies origination, extinction and sampling rates for the Ordovician biodiversity increase. The analysis of a global fossil occurrence dataset shows that the observed increase happened due to a peak of origination rates, while extinction rates remained low. Different palaeocontinents, palaeoenvironments, and all major taxonomic groups show the same peak. This is new evidence for a globally acting driver behind the Ordovician biodiversity increase. Minor differences still exist. For instance, some hard substrate taxa, as echinoderms and bryozoans, had elevated origination rates already during the Early Ordovician. In addition, origination and extinction rates were persistently higher on the palaeoncontinent Baltica than on the palaeocontinent Laurentia throughout the Ordovician.
This thesis provides a new baseline for testing specific hypotheses about the common cause behind the Ordovician biodiversity increase in large geographic regions, ecological units and taxonomic groups.
Contact: Elisabeth Aronsen
Organizer: Natural History Museum