Biodiversity dynamics of semi-enclosed marine basins:

insights from Cenozoic molluscan faunas of Europe


A conception of the PhD study of Rafal Nawrot

financed by uni:doc fellowship progamme


MSc. Rafał Nawrot

uni:doc fellow at the Department of Palaeontology, University of Vienna



Supervisor of the PhD-project: Univ. Prof. Dr. Martin Zuschin




The goal of the present project is to investigate how biogeographic factors affect the fate of marine biodiversity during intervals of climatic changes by comparing two fundamentally different setting: semi-enclosed basins and open-ocean-facing continental shelfs.

We will take advantage of the rich marine fossil record of Central and Western Europe to track biotic responses to the Middle Miocene Climate Transition (MMCT; ~15–13.8 Ma ago) – the final step from “Greenhouse” to “Icehouse” state in the Cenozoic climate evolution.

We plan to document temporal shifts in diversity and composition of benthic molluscan faunas (primary bivalves and gastropods) on local and regional scales in two palaeogeographic entities: the Central Paratethys – a vast land-locked sea, and the Aquitaine Basin (SW France) – an open embayment of the eastern Atlantic Ocean.




We want to test the following hypotheses:

1) The Middle Miocene molluscs extinction and turnover represent a genuine biotic event rather than stratigraphic and sampling artefact related to the significant global sea level fall during the MMCT.

2) Temporal diversity trends across the MMCT in the Central Paratethys Sea and Aquitaine Basin are decoupled, directly reflecting their distinct palaeogeographic character:

·         in the semi-enclosed setting (Central Paratethys), where vulnerability of species to extinction was increased by presence of barriers to dispersal and enhanced environmental stress, both regional and local diversity decreased;

·         in the open shelf setting (Aquitaine Basin) diversity remained more stable in spite of taxonomic turnover, because latitudinal range shifts balanced local extinctions by immigration of cool-water taxa from the adjacent regions.

3) Nearshore assemblages in both regions were characterized by greater compositional persistence through the MMCT interval compared to more offshore faunas, since adaptation to local environmental variability may buffer against large-scale perturbations.


Research team

This PhD-project will be supported by an international research team, which will ensure the establishment of a rigorous taxonomic and stratigraphic framework inevitable for interpretation of diversity patterns:

·         Rafał Nawrot (a uni:doc fellow at the Department of Palaeontology, University of Vienna)


·         Martin Zuschin (supervisor of the project, Department of Palaeontology, University of Vienna),

·         Mathias Harzhauser (Natural History Museum, Vienna)

·         Oleg Mandic (Natural History Museum, Vienna)

·         Barbara Studencka (Museum of the Earth, Polish Academy of Sciences, Warsaw, Poland)

·         Bruno Cahuzac (Laboratoire de Recherches et Applications géologiques, Université Bordeaux-1, France)

·         Vitaliy Anistratenko (Schmalhausen Institute of Zoology, National Academy of Sciences

·         of Ukraine, Kiev, Ukraine)

·         Adam Tomašových (Geological Institute, Slovak Academy of Sciences, Bratislava, Slovakia)

·         Michał Kowalewski (Florida Museum of Natural History, Gainesville, Florida, USA)



We will use two partly independent and complementary approaches to assess temporal diversity patterns across the MMCT:

1) High-resolution relative abundance data from bulk samples collected in the field and placed in high-resolution stratigraphic and palaeoenvironmental context.

2) Species occurrences data extracted from the published literature and major museum collections

To account for the effects of scale and to explore how changes in diversity were accommodated in the regional diversity structure, hierarchical diversity partitioning approach will be used. Temporal trends in different scale-related diversity components will be compared between the two study areas and multivariate ordination methods will help to recognize compositional turnover in the analyzed faunas.



The project is funded by the University of Vienna in the framework of the uni:doc fellowship progamme. Initial data collection was supported by the Ernst Mach Scholarship at the Department of Palaeontology, University of Vienna founded by the Austrian Agency for International Cooperation in Education and Research.