Ecological continuity and transformation after the Permo-Triassic mass extinction in northeastern Panthalassa

Abstract

The Permo-Triassic mass extinction (PTME) is often implicated in the transition from the Paleozoic evolutionary fauna (PEF) to the modern evolutionary fauna (MEF). However, the exact timing and details of this progression are unknown, especially regarding the vacating and filling of functional ecological space after the PTME. Here, we quantify the functional diversity of middle Permian and Early Triassic marine paleocommunities in the western US to determine functional re-organization in the aftermath of the PTME. Results indicate that while the PTME was selective in nature, many new Triassic taxa either re-filled functional roles of extinct Permian taxa or performed the same functional roles as Permian survivors. Despite this functional overlap, Permian survivors and new Triassic taxa differed significantly in their relative abundances within those overlapping functions. This shift in numerical emphasis, driven by an increase in abundance towards more MEF-style traits, may represent a first step in the transition between the PEF and MEF. We therefore suggest that the extreme impact of the PTME had significant and permanent re-organizational effects on the intrinsic structure of marine ecosystems. Early Triassic ecosystems likely bridged the gap between the Paleozoic and modern evolutionary faunas, as newly originated Triassic taxa shared ecospace with Permian survivors, but shifted functional emphasis.

Complex marine bioturbation ecosystem engineering behaviors persisted in the wake of the end-Permian mass extinction

“…The three ecosystem engineering behaviors present in the Permian -compression-gallery biodiffusion, backfill conveyor, and compression-biodiffusion -are still present even in the Induan. These results are in agreement with previous observations that, despite the high extinction rates and selectivity associated with the end-Permian mass extinction, there was little change in functional group diversity between pre-and post-extinction benthic ecosystems 33,34 .…”

“…1 and 2). The persistence of all ecosystem engineering behaviors likely reflects either behavioral redundancy in bioturbating ecosystem engineers or that new Early Triassic bioturbators rapidly refilled empty roles of the extinct Permian ecosystem engineers 34 .…”

A multiscale view of the Phanerozoic fossil record reveals the three major biotic transitions

“…Sepkoski formulated this three-phase model based on a factor analysis of family-level diversity 2 , which became a framework-setting assumption in studies on the evolution of marine faunas and ecosystems [3][4][5][6] , changing our view of the Phanerozoic history of life. However, while the hypothesis continues to serve as a conceptual platform for many recent studies 5,[7][8][9] , some analyses question the validity of Sepkoski's hypothesis 10 . Moreover, because Sepkoski's study predicts unusual volatility in the Modern evolutionary fauna starting during the mid-Cretaceous, a three-phase model fails to capture the overall diversity dynamics during long portions of the Mesozoic 11 .…”

Beyond functional diversity: The importance of trophic position to understanding functional processes in community evolution

“…The Permian-Triassic Mass Extinction (PTME) eliminated 69% of marine genera and was hence a transformative event for marine systems that was highly selective against stationary epifauna and other less energetically intensive life modes, resulting in liberated ecospace for more competitive successors to proliferate during the Mesozoic (Bush and Bambach, 2011;Dineen et al, 2019). In addition to changing guild diversity, there was a notable decrease in ntp, mcl, and log bs between the Anisian and Carnian stages.…”