The biology and ecology of Genoplesium baueri R.Br., an endangered terrestrial orchid endemic to New South Wales, Australia

Admiration of flowering plants in the species-rich Family Orchidaceae spans many cultures of the world. The investigation of their fascinating biology by renowned scientists such as Charles Darwin in the 1800’s has helped inspire botanists and ecologists to continue researching them into the present day. Empirical observations on demographics, biology and ecology of individual species provide a knowledge base to such research and are essential in supporting our understanding and conservation of these species. However, species-specific knowledge has been found lacking for many south-eastern Australian orchids. Therefore, the overarching aim of this research was to examine the demographics and biology of the rarely collected terrestrial orchid species, Genoplesium baueri R.Br., an endangered species endemic to the Sydney Basin, New South Wales, with the aim of supporting its conservation into the future. This was done by carrying out a systematic ten-year study (2009-18) of all individual plants in two key populations on the northern periphery of Sydney. I found that the two populations contained more plants than previously known across the entire range of the species; that annual emergent population size was positively related to effective fruit set two years previously while plant size was positively related to November-April rainfall. Additionally, rainfall 1-2 weeks prior to one week of low rainfall was found to initiate population emergence. Investigation of reproductive effort found the number of flowers per plant, pollination rate and effective fruit set varied among years and across sites although effective fruit set was higher in plants that emerged in autumn compared to summer. These data were combined with natural history observations to construct a schematic diagram of the proposed lifecycle of G. baueri which captured and evaluated the above-and below-ground stages of plant development and loss. These northern populations of G. baueri are stable or increasing, so with continued site protection under current climatic conditions, these populations should persist into the future. Nevertheless, variability of population/plant size suggests that climate change may have a significant impact on fruit production which may negatively impact population size in Genoplesium baueri.