Format: ORAL

Evelin Krol1,2,3, Alicia Grealy3, Ashley R. Field2,4, Mark Clements5,Keith Mc Donald6, Heidi Zimmer5, Natascha D. Wagner1, Katharina Nargar2,3

1 Department of Systematics, Biodiversity and Evolution of Plants, Georg August University of Göttingen, Göttingen, Germany 2 Australian Tropical Herbarium, James Cook University, Cairns, Australia 3 National Research Collections Australia, Commonwealth Industrial and Scientific Research Organisation (CSIRO), Canberra, Australia 4 Queensland Herbarium, Department of Environment and Science, Mount Coot-tha Botanic Gardens, Brisbane, Australia 5 Centre for Australian National Biodiversity Research (Joint Venture between Parks Australia and CSIRO), Canberra, Australia 6 Queensland Museum, Brisbane, Australia

Conservation of wild species is a major responsibility given the global extinction crisis. Wild orchids face threats from illegal harvesting and trade, driven by demand for horticultural, ornamental, cosmetic, and medicinal use. For effective conservation management, it is crucial to accurately assess the genomic diversity of natural populations and determine their taxonomic boundaries. However, delimitation of species complexes in orchids remains a considerable challenge due to shallow genetic differentiation and conflicting morphological and genetic signals resulting from hybridization. The Cooktown orchid complex (Dendrobiumbigibbums.l.) comprises epiphytes and lithophytes with striking purple-pink flowers, rendering it a popular group for horticulture. Spanning over 140,000 km2, the complex primarily occurs in the subtropical Cape York Peninsula of Queensland (Australia) and represents the states floral emblem. Its popularity has caused overcollection in easily accessible areas, resulting in local extinctions and taxa of this complex being classified as endangered or vulnerable under national legislation. Despite being of high public interest, the taxonomic delimitation remains unclear. Since its original description, multiple species, subspecies and varieties have been proposed. This study uses next-generation sequencing to disentangle the evolutionary relationships within the Cooktown orchid complex. Over 200 individuals across its geographic distribution and morphological diversity were sampled, including associated taxa as well as intermediate forms. We compared the performance of three target capture bait kits regarding informativeness and capture efficiency: a universal bait set for all flowering plants (Angiosperms353), a custom bait set forOrchidaceae(Orchidaceae963), and a lineage-specific custom bait set forBulbophyllum/Dendrobium. Based on our assessment, we selected the best-performing kit to generate target capture data.Our results shed light on the evolutionary patterns and genetic diversity within this threatened orchid species complex, allowing for a reassessment of taxonomic delimitation andinforming conservation management to protect Queenslands botanical treasure.