Characterisation of Adelopetalum argyropus (Orchidaceae; Malaxideae) with the description of two related new species and two new combinations

The Adelopetalum argyropus species complex is distributed across eastern Australia, Lord Howe Island, Norfolk Island, New Caledonia and New Zealand. We undertook morphological examination of living plants and fresh flowers, dissected flowers mounted on cards, dried and spirit-preserved herbarium specimens and made images of living flowers. We characterise Adelopetalum argyropus as endemic to Norfolk Island. Two previously confused species, one from mainland Australia, A. continentale, and another from Lord Howe Island, A. howense, are described here as new. Extinction risk is preliminarily assessed for the three taxa: A. continentale was severely impacted by the 2019–2020 bushfires on mainland Australia, whereas A. argyropus and A. howense are each restricted to small oceanic islands; Norfolk Island and Lord Howe Island respectively.