Materials and methods
The measurements and descriptions were based on freshly collected materials. Multiple photographs were taken using Canon EOS 800D and coloured plates were prepared and edited in Affinity Photo software. Flowers were preserved in 70% ethanol and were subjected to stereomicroscopy. The general plant descriptive terminology follows Beentje (2016). Herbarium citations follow Index Herbariorum (Thiers 2023). Relevant specimens and literature of Thottea species from the Philippines and neighbouring countries were examined in different herbaria through high-resolution images from Global Plants on JSTOR accessed at https://plants.jstor.org/ or Global Biodiversity Information Facility (GBIF) accessed from https://www.gbif.org. An assessment of the conservation status was carried out following IUCN (2022), based on our current knowledge and using their terminology on categories, criteria and subcriteria.