STABILITY, COLLAPSE AND RECOVERY OF TERRESTRIAL ECOSYSTEMS IN EAST GREENLAND ACROSS THE TRIASSIC-JURASSIC MASS EXTINCTION BOUNDARY

The contribution of vegetation change to vertebrate faunal extinction in the late Triassic and early Jurassic has received little attention. Yet, modern ecological theory predicts that a disruption or loss of primary productivity can result in a cascade of extinctions throughout the entire ecosystem from primary consumers to the highest trophic levels. Here we show that terrestrial vegetation underwent major ecological upheaval before and coincident with the Triassic-Jurassic mass extinction boundary in the region of Astartekløft in East Greenland. From a paleoecological database of 4303 fossil plant specimens we document (1) complete turnover of ecological dominance within the plant canopy, (2) loss of the mid canopy niche, and (3) loss in generic level richness and evenness. Our paleoecological analyses reveals that extinctions were highest amongst taxa of moderate abundance and with specialized reproductive strategies, that likely relied on insect vectors for pollination. Selective extinctions are also observed in understory and floodplain taxa with large leaves. Ecosystem recovery at the generic level was relatively rapid, particularly among peat forming plant communities, however plant communities in the post extinction interval were highly unstable, showing much higher species level turnover than observed in pre-boundary time. Despite relatively minor worldwide extinction among higher taxonomic groups at the Triassic-Jurassic extinction boundary, these marked paleoecological changes and species level extinctions were of sufficient magnitude to severely disrupt primary production and likely resulted in emigration and/or extinction of primary consumers contributing significantly to vertebrate turnover at the Triassic-Jurassic mass extinction boundary.