CLIMATE-DRIVEN BIOTIC CHANGE IN THE MARINE PERMIAN OF EASTERN AUSTRALIA DURING THE AFTERMATH OF THE LATE PALEOZOIC ICE AGE

Quantitative data from 73 Early Permian fossil assemblages in the Tasmania, Sydney, and Bowen Basins of eastern Australia reveal pronounced biotic change during global climate warming following the late Paleozoic ice age, from glacial communities dominated by the bivalve Eurydesma and the brachiopod Trigonotreta to postglacial assemblages with abundant brachiopods such as Terrakea and Echinalosia. Cluster analysis indicates that this shift was broadly synchronous across latitudinal zones, from polar regions in Tasmania to temperate settings in Queensland. However, the biotic shift may have occurred earlier in offshore habitats, suggesting that climate-linked oceanographic change was a major influence. Detrended correspondence analysis reveals that Artinskian communities, during the transition from glacial to postglacial climates, were substantially more variable than either Sakmarian glacial or Kungurian postglacial assemblages. This variability, including the development of assemblages dominated by otherwise uncommon genera, is similar to the rapid fluctuations previously observed in terrestrial plant communities during the same time interval and may be indicative of climatically-induced disruption of marine ecosystems. A global database of Permian fossil occurrences demonstrates that the dominant glacial genera Eurydesma and Trigonotreta exhibited very different postglacial biogeographic patterns, despite undergoing similar decreases in local dominance in eastern Australia. Eurydesma's geographic range contracted during postglacial warming as the genus became restricted to eastern Australia and ultimately died out in the Kungurian, whereas Trigonotreta became much less numerous but maintained a relatively wide Gondwanan distribution and persisted until the end of the Permian. These different responses by glacial genera to postglacial warming indicate that Permian cold-water taxa varied in their ability to adapt to climate change. Thus, the Permian record of eastern Australia implies that long-term global climate warming can drive major turnover in the taxonomic composition of marine communities and may trigger instability similar to that observed in the late Paleozoic terrestrial realm.