Nguyen, NgocBuettel, Jessie C.Brook, Barry W.2026-06-272026-06-270305-0270ORCID:/0000-0001-6737-7468/work/218726660https://hdl.handle.net/1885/733812107Aim: Australia's distinct geological history provides key insights into the diversity of its flora. While previous studies have predominantly focused on climate as the main driver of species richness, growing evidence suggests that geological factors also play an important role. This study aims to investigate the influence of Cenozoic volcanic lithologies on terrestrial vascular plant diversity in eastern Australia, disentangling the relative contributions of climate and geology to biodiversity patterns. Location: Eastern Australia. Taxon: Terrestrial vascular plants. Methods: We assessed the patterns of species richness in this region by examining whether sites with Cenozoic volcanic lithologies harbour greater vascular plant diversity, using a permutational multivariate analysis of variance (PERMANOVA). We then used a supervised machine learning algorithm (decision trees) coupled with partial canonical correspondence analysis (CCA) to discriminate the environmental variables influencing species richness and site composition in 230 sites in Queensland, New South Wales, Victoria and Tasmania. Results: Soil profile variability and terrain ruggedness, influenced by underlying volcanic lithologies, emerged as primary predictors of species richness. We found species composition, indicative of distinct ecological communities, showed greater similarity within lithological types and varied significantly across volcanic complexes at different latitudes. Notably, areas of higher species richness corresponded with a greater diversity of stratigraphic units within protected zones. Main Conclusions: Our study reveals a significant imprint of Cenozoic volcanic activity on present-day plant species richness and distribution in eastern Australia. We show that geological features, particularly lithology and site complexity, play a crucial role in shaping species richness beyond previously recognised climatic factors. These findings highlight the importance of integrating geological and edaphic factors into conservation strategies, thereby broadening our understanding of ecological dynamics, and guiding more effective biodiversity conservation.This research received funding from an Australian Research Council grant (grant number CE170100015). We extend our gratitude to Dr. Benjamin Cohen from the University of Glasgow for his invaluable insights and feedback on geological aspects. Data for this study were collected over two years with the assistance of many field volunteers. Permits for fieldwork in Queensland national parks, resource reserves and conservation parks were obtained under permit number P‐PTUKI‐100107005, and for state forests and forest reserves under permit P‐PTC‐100107002. In Tasmania, permits for public conservation areas and regional reserves were obtained under permit number ES21100. Permission for accessing private properties in Queensland nature refuges and Tasmania conservation covenants was granted by individual landowners with the assistance of Queensland Parks and Wildlife Services and the Tasmanian Land Conservancy. We also thank the many landowners in Queensland and Tasmania for their help and hospitality.14en©2025 The authorsbiodiversityconservationgeologylithologyspecies richnessterrain ruggednesstopographyvolcanic202510.1111/jbi.1503985208728299