Biodiversity patterns, palaeoecology and functional diversity across the "Great Ordovician Biodiversification Event" in the Basin and Range Province, USA
Final Report Abstract
Using quantitative palaeoecology based on extensive fieldwork and new collections of benthic macroinvertebrates from the Ordovician strata of the Basin and Range Province in Utah and Nevada, the project tried to reconstruct how different measures of biodiversity evolve over a diversification event. The time series progressions of alpha, beta and gamma diversity show that gamma diversity is generally generated by an increase in alpha diversity before higher diversity is additionally achieved by an increase in beta diversity, i.e. ecosystem differentiation. This development confirms an intrinsically controlled diversification model, suggesting that competition between species increases diversity in regions of habitats and is therefore an important driver of evolution at the local level. This basic idea has been decisively expanded with data from the Paleobiology Database and applied to the entire Phanerozoic. It could be shown that the particularly drastic increases in diversity since the Cretaceous (and other high diverse time intervals) are not accompanied by an increase in beta diversity and are probably due to changes in the macro-ecological regime of benthic ecosystems. The best explanation for this scenario is the increase in predations pressure, which reduces the abundance of particularly dominant species, thus releasing resources that can be used by otherwise restricted species. The project thus provided crucial evidence that ecosystem-inherent (intrinsic) factors decisively shape diversity dynamics in the Phanerozoic. Thus, it is not only environmental conditions alone that influence diversity through extinction mechanisms or favourable environmental parameters, but ecosystems themselves, due to their internal constitution (i.e. the presence of predators or "ecosystem engineers"), contribute to the development of diversity. Unexpected results concern above all the evidence of the hitherto little studied extinction at the boundary between the Lower and Middle Ordovician. It is particularly interesting that all investigated diversity measures behave according to the model used. There is great potential here to search for causes in conjunction with geochemical analyses in order to further deepen our understanding of the interaction between the biosphere and the ocean-atmosphere system. The bioturbation capacity of the fauna of an ecosystem controls important parameters such as nutrient supply, substrate consistency, sediment aeration and geochemical cycles. During field work, it was noticed that the low diversity interval of the Lower Ordovician is associated with extremely low biogenic sediment reworking. The follow-up of this aspect for taphonomic, stratigraphic, and analytical contexts in terms of geochemistry and biodiversity could be an important approach to reinterpret and understand fundamental mechanisms of system Earth.
Publications
- (2018): Diversity Partitioning in benthic marine ecosystems throughout the Phanerozoic. GeoBonn 2018
Hofmann, R., Tietje, M., Aberhan, M.
- (2018): Diversity patterns and palaeooecology of the Pogonip Group (western US). 3rd Annual Meeting of the IGCP 653, Athens, Ohio
Hofmann, R., Kehl, J.P.
- (2019): Biotic controls on Phanerozoic biodiversity. Geophysical Research Abstracts 21. EGU Meeting 2019
Hofmann, R., Tietje, M., Aberhan, M.
- (2019): Diversity partitioning in Phanerozoic benthic marine communities. Proceedings of the National Academy of Sciences. 116(1), 79-83
Hofmann, R., Tietje, M., Aberhan, M.
(See online at https://doi.org/10.1073/pnas.1814487116) - (2020): Diversity patterns and palaeoecology of benthic communities of the Kanosh Formation (Pogonip Group, Utah, western USA). Palaeobiodiversity and Palaeoenvironments. 100, 993-1006
Hofmann. R., and Kehl, J. P.
(See online at https://doi.org/10.1007/s12549-020-00426-3) - (2020): Firm evidence for a postextinction ichnofauna: An earliest Carboniferous Cruziana reticulata assemblage from the Anti-Atlas of Morocco. Lethaia. 53, 118-128
Hofmann, R, Gutwasser, B., Korn, D., and Hüneke, H.
(See online at https://doi.org/10.1111/let.12345)
