Palaeophytogeographical Patterns Across the Permian–Triassic Boundary

Hendrik Nowak,Christian Vérard,Evelyn Kustatscher

doi:10.3389/feart.2020.613350

Abstract

It has long been recognized that terrestrial floras underwent major and long-lasting changes during the Permian and Triassic, some of which have been attributed to the end-Permian mass extinction. However, these changes are still poorly understood with regard to the late Permian and Early Triassic. In particular, the impact that ecological disturbances around the Permian–Triassic boundary had on the composition and palaeogeographical distribution of land plant communities needs to be scrutinized. We analyse this impact based on fossil floras from across the world, covering the Wuchiapingian to Ladinian time interval. The plant assemblages are assigned to biomes representing particular environmentally controlled community types. Variations in the distribution of biomes between stages indicate shifts in the environmental parameters affecting terrestrial floras, and provide insights into population turnover dynamics. A substantial shift towards increasing seasonality and a reduction of biome diversity occurs in the earliest Triassic and stabilised throughout the Middle Triassic. However, results also show that the stratigraphically and (palaeo-) geographically unequal distribution of sampled localities constitutes an important limitation for this kind of analysis.

Highlights

The Permian–Triassic transition was marked by drastic disturbances in marine and terrestrial ecosystems
We present here a stage-level analysis of the distribution of biomes based on land plant macrofossil assemblages from the Wuchiapingian to Ladinian, in an attempt to track global-scale climate shifts with an effect on plant communities
This study shows how the composition of biomes changes through time and how the patchiness of the plant fossil record affects the uncertainty regarding the boundaries between biomes

Summary

INTRODUCTION

The Permian–Triassic transition was marked by drastic disturbances in marine and terrestrial ecosystems. It is generally accepted that the community structure of terrestrial floras underwent important changes, and there is a growing consensus that these changes should primarily be understood as a matter of successive ecological disturbances, rather than a question of abrupt biodiversity loss (Hochuli et al, 2016; Mishra et al, 2017; Fielding et al, 2019; Nowak et al, 2019; Vajda et al, 2020) Palaeophytogeographical aspects of these changes on a global scale have mainly been studied through the recognition of different phytochoria (or phytoprovinces) – phytogeographical units that are defined on the presence of common taxa, and are stratigraphically constrained by the ranges of these taxa (e.g., Vakhrameev et al, 1978). Climate-indicative sediment data from the late Permian to Middle Triassic were extracted from Boucot et al (2013); see

MATERIALS AND METHODS

RESULTS

Findings

DISCUSSION