THE RISE AND FALL OF DISASTER TAXA: Ecosystem recovery following the Permo-Triassic mass extinction
Project Summary
The Permo-Triassic mass extinction (PTME; c. 252 Ma) was the most catastrophic biotic event of the Phanerozoic with up to 96% of marine animals going extinct (Dal Corso et al. 2022). Full recovery of marine biodiversity to pre-extinction levels did not occur until around 5 million years after the PTME due to prolonged environmental stress (Song et al. 2018). The initial recovery interval is characterised by low-diversity, high-abundance communities of opportunistic ‘disaster taxa’ (e.g. the bivalve Claraia: Figure 1). These communities dominated shallow marine assemblages in the earliest Triassic before seemingly being outcompeted by more specialised taxa as community succession occurred (Petsios & Bottjer 2016).
Despite biodiversity seemingly recovering by the Middle Triassic, the delay until full ecological recovery is more controversial. Some previous studies have suggested that ecological recovery was relatively quick and occurred in a step-wise bottom-up fashion of lower to higher trophic levels with full ecosystem recovery completed during the Middle Triassic (Chen & Benton 2012). However, others have suggested that full ecological recovery was much slower, and lasted throughout much of the Triassic (Song et al. 2018).
This project aims to evaluate the nature of ecosystem recovery, from the low diversity communities of the earliest Triassic, to the supposedly fully recovered marine ecosystems of the Middle-Late Triassic and to test alternative hypotheses: was recovery an intrinsic process of community reconstruction or was it controlled by the gradual amelioration of the harsh conditions that caused the mass extinction? The student will make use of community ecology methods in order to model ecosystem structural changes via food webs as well as spatial networks and evolutionary rate models to test hypotheses around the dynamics of community connectivity and how this might have driven origination and extinction rates during the recovery interval and beyond.
Objectives
- Model marine food webs to reconstruct a time series of fossil communities of interacting organisms through the extinction and recovery interval.
- Quantify changes in ecosystem structure and function, in order to determine the nature and timing of ecological and evolutionary changes across extinction and recovery interval.
- Model community-connectivity via spatial networks and test how this influenced evolutionary rates through the recovery interval and beyond.
Methods
The student will assemble community-level and global occurrence data and will model marine metacommunity food webs using the Paleo Food Web Inference Model (Shaw et al. 2022) in order to track changes in ecosystem structure across the mass extinction and recovery interval. The student will also model community connectivity using a bipartite network approach to track levels of cosmopolitanism and endemism and compare these to spatially explicit origination and extinction rates through the interval (Allen et al. 2022).
Impact and publications
This project will use cutting-edge methodologies to address some longstanding questions in palaeobiological research whilst also addressing questions relevant to modern day ecology and conservation biology by detailing the duration and nature of ecosystem recovery in the context of food web stability and proliferation of opportunistic taxa, following a major disturbance caused by rapid warming. The work is easily divisible into publications that form consecutive chapters of the PhD thesis.
A nurturing training and research environment
The student will gain experience in database construction, palaeoenvironmental analysis, ecological and macroevolutionary modelling. This will equip the student with the necessary expertise to become part of the next generation of palaeontological and ecological scientists. The student will be based within the lab of Dr Dunhill within the Earth System Science Institute (ESSI) at the University of Leeds. Dr Dunhill oversees a friendly and relaxed lab group that puts student development and well-being before all else. Together with the welcoming and collegiate atmosphere fostered within ESSI, this creates an ideal environment for students to flourish and express their academic creativity. The student will also have direct supervision for other world-leading experts on the supervisory team and will have opportunities to present their findings at a host of major conferences.
References
Allen BJ, Saupe EE, Clapham ME, Wignall PB, and Dunhill AM. 2022. Estimating spatial variation in origination and extinction in deep time: a case study using the Permian–Triassic marine invertebrate fossil record. Paleobiology in review.
Chen ZQ, and Benton MJ. 2012. The timing and pattern of biotic recovery following the end-Permian mass extinction. Nature Geoscience 5:375-383. 10.1038/ngeo1475
Dal Corso J, Song H, Callegaro S, Chu D, Sun Y, Hilton J, Grasby SE, Joachimski MM, and Wignall PB. 2022. Environmental crises at the Permian–Triassic mass extinction. Nature Reviews Earth & Environment 3:197-214. 10.1038/s43017-021-00259-4
Petsios E, and Bottjer DJ. 2016. Quantitative analysis of the ecological dominance of benthic disaster taxa in the aftermath of the end-Permian mass extinction. Paleobiology FirstView:1-14. doi:10.1017/pab.2015.47
Shaw JO, Dunhill AM, Beckerman A, Dunne JA, and Hull PM. 2022. Constructing and comparing ancient food webs using functional diversity data. Methods in Ecology and Evolution in revision.
Song H, Wignall PB, and Dunhill AM. 2018. Decoupled taxonomic and ecological recoveries from the Permo-Triassic extinction Science Advances 4:eaat5091. 10.1126/sciadv.aat5091