Global catastrophe or random decline? Evolutionary perspectives on the fall and rise of tetrapods across the Permo-Triassic boundary

Lead Research Organisation: University of Lincoln
Department Name: School of Life Sciences

Abstract

Around 251 million years ago, at the end of the Palaeozoic Era, a major crisis affected marine and terrestrial organisms, resulting in a catastrophic drop in animal and plant diversity. This crisis is known as the Permian mass extinction event. While the factors underlying this crisis are still unclear, one aspect of it stands out: life at large suffered a remarkable collapse. This extinction is the most dramatic of all large-scale biological crises that have taken place over the last 550 million years. The few survivors of the end Permian event are held to have undergone a slow recovery and were responsible for carrying out a 'critical mass' of diversity that allowed expansion of life at the beginning of the Mesozoic Era. This recovery was accompanied by a major remodelling of animal and plant communities, resulting in the dominance of certain groups that were poorly represented before the extinction, the emergence of new groups, and the establishment of modern-looking ecosystems and food chains. But just how dramatic was the end-Permian event? This project seeks to assess the impact of the Permian extinction on terrestrial vertebrate communities. Some groups of vertebrates appear to have carried on through the event seemingly unaffected; others showed a sudden or steady decrese in abundance and went extinct forever before the end Permian; yet others experienced an explosive radiation in the lowermost Triassic. It is clear that different vertebrates responded differently to the crisis, but the patterns and dynamics of the extinction require detailed scrutiny. This project therefore looks at ways in which data from the geological and fossil records can be amalgamated to offer a more precise characterization of a critical episode in the history of life, and to make sense of the patchy fossil documentation in terms of biological signal (evolution). There is much scope for clarifying whether an intense post-extinction 'rebound' is the sole or the main mechanism accounting for the elevated taxonomic richness (high diversity) of some groups in the lowermost Triassic (especially when compared to diversity values during the mid to late Permian), following a period of slow and steady recovery. But how slow was this recovery? So far, the analysis of evolutionary relationships of groups and studies of the organization and/or level of complexity of ecosystems have given contrasting answers and there are reasons to suspect that, once again, different types of vertebrates recovered at different rates. Furthermore, I aim to disentangle the complex interplay between originations and extinctions immediately before and after the extinction event and in order to assess the influence of secondary, small-scale (background) extinctions. This is important because it is known that some vertebrates disappeared or declined progressively some time before the Permian event. In addition, some other vertebrates went through a series of sudden diversification 'bursts' before the extinction proper. The project will attempt to tease out geographical or ecological factors that might drive patterns of declining diversity. In other words, the extinction may have selectively operated on groups that lived in certain regions and/or habitats. Finally, the project will determine whether observed variations in diversity before and after the Permo-Triassic extinction are strongly correlated with outcrop availability (extent and number of fossil-bearing localities) and whether abundance levels in some geological sections do in fact reflect real taxon richness. Corrections for missing portions of phylogeny are possible, and these provide a clearer picture of the extent to which groups are represented even in the absence of direct fossil evidence. Ultimately, this research aims to realise the potential of fossil vertebrates to uncover, refine or challenge evolutionary models during periods of major biotic disaster and large-scale faunal transformations.

Publications

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Related Projects

Project Reference Relationship Related To Start End Award Value
NE/F014872/1 01/01/2009 03/09/2012 £438,353
NE/F014872/2 Transfer NE/F014872/1 04/09/2012 03/01/2014 £117,258
 
Description Research so far has revealed:

1 The fossil record of limbed vertebrates is better than it is usually portrayed, and captured adequately key events of diversification.

2 The onset of ecological innovation and the acquisition of a key evolutionary trait do not always trigger increase in bodyplan complexity, and do not necessarily trigger a boost of diversification

3 Major radiations are not always adaptive, and there is often a decoupling between morphological variety (e.g. anatomical diversity) and group diversity (e.g. species number)
Exploitation Route The work I conduct uses the tetrapod fossil record to decipher the dynamics of biological change at morphological, functional, and ecological levels - the core themes of macroevolution. By providing measurable and testable models of group diversification and trait evolution, the fossil record offers the unique, deep time perspective on tempo and mode of major radiations, faunal turnover, and geo-biosphere interplay, all of which require urgent attention. To understand how extant biodiversity was shaped during millions of years of evolution, it is necessary to bring into sharp focus questions that have been debated since Darwin. Life today is hugely diverse, but why is this diversity accounted for by only very few groups? As an example, >85% of the 62,000 extant vertebrate species belong to just six major clades. In addition, the diversity of closely related groups is often skewed. For instance, crocodiles and birds shared a common ancestor ~245 Myr ago, but why is their modern biodiversity so different (23 and 10,000 species, respectively)? These and other observations require explanation in light of modern methods for modelling palaeodiversity fluctuations, including during the origin and diversification of major groups.
Sectors Education,Culture, Heritage, Museums and Collections

 
Description Informing undergraduate/postgraduate teaching Providing material for undergraduate/postgraduate research projects Augmenting scope and remit of fossil-based research
First Year Of Impact 2012
Sector Education,Culture, Heritage, Museums and Collections
Impact Types Cultural,Societal

 
Title Early tetrapod database 
Description Compilation of stratigraphic occurrences for tetrapods, ranging from Palaeozoic through to early Mesozoic (http://dx.doi.org/10.5061/dryad.44b50) 
Type Of Material Database/Collection of data 
Year Produced 2013 
Provided To Others? Yes  
Impact Extensive data mining addressing issues of fossil record quality and adequacy 
URL http://dx.doi.org/10.5061/dryad.44b50
 
Description Extinction and turnover at the Permo-Triassic boundary 
Organisation University of Bristol
Country United Kingdom 
Sector Academic/University 
PI Contribution Application of various metrics of faunal turnover to primitive tetrapods
Collaborator Contribution Provisions of large-scale compendia of tetrapod distribution in space and time
Impact Publication: RUTA, M. and Benton, M.J. 2008. Calibrated diversity, tree topology and the mother of mass extinctions: the lesson of temnospondyls. Palaeontology, 51: 1261-1288. Publication: Brusatte, S.L., Benton, M.J., RUTA, M. and Lloyd, G.T. 2008a. Superiority, competition, and opportunism in the evolutionary radiation of dinosaurs. Science, 321: 1485-1488. Publication: Brusatte, S.L., Benton, M.J., RUTA, M. and Lloyd, G.T. 2008b. The first 50 million years of dinosaur evolution: macroevolutionary pattern and morphological disparity. Biology Letters, 4: 733-736. Publication: Lloyd, G.T., Davis, K.E., Pisani, D., Tarver, J.E., RUTA, M., Sakamoto, M., Hone, D.W.E., Jennings, R. and Benton, M.J. 2008. Dinosaurs and the Cretaceous Terrestrial Revolution. Proceedings of the Royal Society of London: Biological Sciences, 275: 2483-2490. Publication: Thorne, P.M., RUTA, M. and Benton, M.J. 2011. Resetting the evolution of marine reptiles at the Triassic-Jurassic boundary. Proceedings of the National Academy of Sciences of the United States of America, 108: 8339-8344. Publication: Prentice, K.C., RUTA, M. and Benton, M.J. 2011. Evolution of morphological disparity in pterosaurs. Journal of Systematic Palaeontology, 9: 337-353. Publication: Brusatte, S.L., Benton, M.J., Lloyd, G.T., RUTA, M. and Wang, S.C. 2011. The evolutionary radiation of archosaurs (Tetrapoda: Diapsida). Earth and Environmental Science Transactions of the Royal Society of Edinburgh, 101: 367-382. Publication: Benton, M.J., RUTA, M., Dunhill, A.M. and Sakamoto, M. 2013. The first half of tetrapod evolution, sampling proxies, and fossil record quality. Palaeogeography, Palaeoclimatology, Palaeoecology, 372: 18-41.
Start Year 2006
 
Description Macroevolutionary analyses in early tetrapods 
Organisation Humboldt University of Berlin
Country Germany 
Sector Academic/University 
PI Contribution We are applying phylogenetic comparative methods to investigate trait evolution in various groups of early limbed vertebrates.
Collaborator Contribution My colleagues have supplied refined time calibration points for phylogenies of various early amphibian and reptile groups
Impact Publication: RUTA, M., Cisneros, J.C., Liebrecht, T., Tsuji, L.A. and Müller, J. 2011. Amniotes through major biological crises: faunal turnover among parareptiles and the end-Permian mass extinction. Palaeontology, 54: 1117-1137. Publication: Witzmann, F., Scholz, H. and RUTA, M. 2009. Morphospace occupation of temnospondyl growth series: a geometric morphometric approach. Alcheringa, 33: 237-255.
Start Year 2010