Hill, RobertMunroe , Samantha (CSIRO)Hill , Kathryn (DeBill Environmental)Atkins, Rachel Amber2025-06-022025-06-022024https://hdl.handle.net/2440/144883Naracoorte Caves is an important palaeontological site that contains both faunal and floral remains, a combination that is rare due to differing preservation condition requirements. The information recorded by these fossils can help us to reconstruct the palaeoecosystems and palaeoclimate of the southeast region of South Australia and better understand how variable environmental influences led to change in the diversity, composition, and morphology of regional biota. To date, research efforts have primarily focused on the ancient fauna of Naracoorte. Only recently has attention been directed towards better understanding the palaeovegetation community. Robertson Cave is one of the only caves within the Naracoorte Caves World Heritage Area known to contain plant macrofossils. While there have been a handful of studies on the plant macrofossils of Robertson Cave, they have not been studied in detail. Therefore, I investigated the plant macrofossils of Robertson Cave to reconstruct the late Quaternary vegetation of the Naracoorte region and gain greater insight into the influences of climate on ancient plant communities and adaptation strategies. To use plant macrofossils as a tool for palaeovegetation reconstruction, they must be sufficiently preserved to be identifiable. I assessed the preservation quality of four taxa represented by the plant macrofossils by creating specific scoring criteria. The level of preservation varied among taxa and the type of plant organ, where robust fruit, seeds and leaves were better preserved than flowers. Preservation was only sometimes affected by the age of the specimen, where older specimens exhibited greater decay. Overall, the plant macrofossils were well-preserved. Recognisable plant macrofossils were identified using diagnostic features and, where diagnostic features were not available, comparative images from Plants of South Australia and the South Australian Seed Conservation Centre were used. Thirty-four taxa were successfully identified, representing 25 families. Plant macrofossils of Allocasuarina verticillata, Astroloma humifusum, Banksia marginata, and Eucalyptus were found to be the most abundant. Seventy-one percent of the taxa identified across the entire sedimentary sequence from macrofossils form a part of the modern plant community growing in the Naracoorte Caves World Heritage Area. The remaining 29 percent do not grow within this area but can be found in other regions across Australia. All identified taxa were used to reconstruct the type of vegetation that grew within the Naracoorte region during the late Quaternary. My research determined the Naracoorte region was likely an Allocasuarina, Banksia and Eucalyptus open woodland with a shrubby understorey, similar to what grows there today. However, while the overall vegetation type has not changed, I found strong evidence to indicate the composition of the understorey varied with the Marine Isotope Stages that spanned the late Quaternary. There was also evidence of morphological change influenced by the climate phases. Leaves of Banksia marginata became wider as the climate transitioned from glacial to interglacial. These observations indicate the regional plant community was responsive to climate change. My thesis has substantially enhanced the current understanding of the late Quaternary vegetation of southeast South Australia and the influence of palaeoclimate on plants more broadly. It also forms one of only a few Australian Quaternary plant macrofossil studies and provides a database for future plant macrofossil identification within the region. By reconstructing the palaeovegetation, predictive models can be created, based on the response of ancient flora to past climate change. This allows us to make informed assumptions about the impact of future climate on modern plant communities, which can aid in preventing species extinction by improving conservation efforts.enThesis