PhD: The rise and fall of disaster taxa: Ecosystem recovery following the Permo-Triassic mass extinction

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.