Song, Bofeng2025-11-122025-11-12https://hdl.handle.net/1885/733794069Pollination services play important roles for ecosystem function and societal well being, yet widespread reports suggest that pollinators have declined significantly. Orchids have attracted much attention for their pollination ecology because of their diverse morphologies and unique pollination syndromes. Orchid pollination is particularly vulnerable due to the specialised nature of orchids, making them sensitive indicators of environmental change, especially in the face of decreasing pollinator populations, anthropogenic climate change, and habitat modification and loss. This study investigates the long-term trends in pollination services for Australian orchids within the genus Caladenia, a genus which exhibits diverse pollination syndromes, including food deception, sexual deception and self-pollination. For this study, I examined 10,494 dried herbarium flowers of Caladenia at the Australian National Herbarium. Each specimen was critically assessed using a microscope, recording data for five key variables that infer whether pollination services have occurred - pollinia removal, fertilised ovaries, stigma pollen, insect parts, and accessible flowers. The primary objectives of this research were: (1) to quantify the changes in Caladenia pollination services over the past century, (2) to evaluate if different Caladenia species, with varying pollination syndromes and specialisation on different pollinator groups, exhibit differences in the level of pollination services they have received, and (3) to assess the influence of anthropogenic factors, such as habitat fragmentation and climate change, on pollination services. My results reveal that overall evidence of pollination services for Caladenia have declined by 27.1% over the past 100 years, with a marked acceleration after 1970 nearly four times the rate of decline compared to earlier decades (1925-1970). Moreover, the results indicate significant variation in pollination services and decline rates across different pollination syndromes: species using sexual deception had the highest evidence of pollination services, but also the greatest rate of decline. Compared to sexually deceptive species, food-deception species had a lower mean evidence of pollination services over all years and showed the second greatest decline. Self-pollinating species had the lowest evidence of pollination services over all years compared to species that are outcrossing via sexual or food deception and showed no significant decline. The decline in pollinator services since the 1970s was consistent in Caladenia cross species specialising on different pollinator taxa. I found a correlation between environmental changes, including rising temperatures and land-use changes and declines in pollination services, where increases in temperature anomaly were the most important predictor of pollination service decline over the last 100 years. These findings underscore that a major overarching anthropogenic driver is most likely responsible for declines in orchid pollination services.en-AU202410.25911/TH9X-QQ55