2. Diversity in time and space: integrating across fossil and living mammalian species

This is the second main topic in the working group of Dr Susanne Fritz, where ., where we mostly work on large mammals through the Neogene (approximately 23-2 million years ago) until today. Here, we bring together paleontological data on past environmental conditions and extinct species with contemporary data on the current environment and living species. Research in ecology and evolution in general has usually been separate, with paleontological studies investigating extinct taxa through time while neontological studies reconstruct the evolutionary history from molecular phylogenies of only the living taxa. Using large mammals with their excellent fossil record in the Northern Hemisphere as a case study, we address integrative key questions across paleo-ecology and evolutionary biology: Which mechanisms generate spatial and temporal variation in diversity? How do diversity patterns in time and space depend on abiotic drivers such as climate? How do traits evolve, and how is trait evolution influenced by the environment? Which processes determine the temporal dynamics of geographical ranges and ecological niches?

Highlighted publications on fossil and living mammalian diversity
Huang, S., Eronen, J. T., Janis, C. M., Saarinen, J. J., Silvestro, D. & S. A. Fritz (2017). Mammal body size evolution in North America and Europe over 20 Myr: similar trends generated by different processes. - Proceedings of the Royal Society B: Biological Sciences 284: 20162361.
An empirical study applying modern Bayesian statistics to a large Neogene fossil record of ungulates (970 species). We show that the consistent trend of increasing body size over 20 million years was generated through different evolutionary processes in different taxa and regions; for example, large-bodied lineages of even-toed ungulates (Artiodactyla) had higher origination rates, suggesting active selection for larger bodies possibly due to environmental change.

Fritz, S. A., Eronen, J. T., Schnitzler, J., Hof, C., Janis, C. M., Mulch, A. Böhning-Gaese, K. & C. H. Graham (2016): Twenty-million-year relationship between mammalian diversity and primary productivity. - Proceedings of the National Academy of Sciences of the United States of America 113: 10908-10913.
Using fossil records of mammals and plants across North America and Europe, we show that higher primary productivity, i.e. net production of plant biomass, was consistently associated with higher mammalian diversity throughout the Neogene, indicating that this relationship is a general ecological pattern in time and space. However, we also show that present-day patterns do not match the fossil diversity-productivity relationship, suggesting that human activity and Pleistocene climate variability have modified a 20-million-year ecological pattern.

Fritz*, S.A., Schnitzler*, J., Eronen*, J.T., Hof*, C., Böhning-Gaese*, K. & C.H. Graham* (2013): Diversity in time and space: wanted dead and alive. - Trends in Ecology and Evolution 28: 509-516. (* equal contributions)
A conceptual framework for the integration of paleontological and neontological perspectives on fossil and living diversity. We highlight the opportunities arising from capitalizing on data and methods from both disciplines, and show how this integration will advance understanding of the fundamental processes that generate and maintain diversity in time and space.

Turvey, S. T. &  S. A. Fritz (2011): The ghosts of mammals past: biological and geographical patterns of global mammalian extinction across the Holocene. - Philosophical Transactions of the Royal Society B: Biological Sciences 366: 2564-2576.
This was a collaboration with Dr Sam Turvey from the IOZ London which investigated over 200 extinct mammalian species together with present-day extinction risk from the IUCN Red List across all living ~5000 species of mammals. We show high spatial and taxonomic selectivity in Holocene extinctions and present-day risk: during the Holocene (i.e. the last 10,000 years), large-bodied mammals have been more extinction-prone nearly everywhere, but today they are primarily threatened in the tropics. This suggests that human activities cause an extinction filter that has already affected big mammals in Europe, North America and Australia and is now striking across the tropics.

Press releases on fossil and living mammalian diversity
"New insights into the mechanisms of how ungulates got bigger in the Neogene" (English), (German)
"For 20 million years, the diversity of large terrestrial mammals depended on plant growth" (English) (German)
"Wanted dead and alive – New concept for a better understanding of biodiversity in time and space" (English) (German)

Other research themes

1. Macroevolution of ecological niches, seasonal migration, and diversification in passerine birds
3. Global macroevolution, macroecology, and biogeography – the big picture
4. Past, current, and future human impacts on biodiversity

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