Plant turnover in response to climate change in the Cenozoic: Palynological insights from Myanmar, Southeast Asia and beyond

Palynology is an effective tool when reconstructing past vegetation, climate, and environment, and can contribute to unravelling the diversification and biogeographic histories of specific lineages with rich pollen fossil records. In this thesis, I aim to (a) document the composition of the late Eocene palynoflora in the Central Myanmar Basin (CMB) and investigate the role of the Burma Terrane (BT) in plant dispersal between India and Asia; b) reconstruct the vegetation, climate and environmental change, and species diversity in the late Eocene CMB; and c) disentangle regional and global diversification and biogeographic histories of palms (Arecaceae). To achieve this, I collected palynological samples from sedimentary rocks along the Kalewa section, northern CMB (a-b), and compiled a dataset of global pollen fossil record for ancestral lineages (i.e., Calamoideae and Nypoideae) (c). I found that the late Eocene Kalewa palynoflora is very diverse and dominated by palms and Sapotaceae, with plant composition driven by plate collision and tropical climate. Abundant Gondwanan and Laurasian components suggest that the BT is a crossroads for plant dispersal between Gondwana and Laurasia. Throughout the Kalewa section, lowland evergreen forests and swamps dominate, and global sea level change drives two transgressive-regressive depositional sequences, under the influence of monsoonal climate. Most palm lineages of Calamoideae and Nypoideae show a general decline in diversity and geographic range in concert with the contraction of tropical rainforests after the Eocene and is thought to be related to the generally cooler and dryer climates throughout the Cenozoic.