Nine new species of Thottea (Aristolochiaceae) in Peninsular Malaysia and Singapore, with two taxa in Peninsular Malaysia redefined and a taxon lectotypified

Nine new species of the genus Thottea, namely T. anthonysamyi, T. kamarudiniana, T. longipedunculata, T. papilionis, T. piscodora, T. reflexa, T. ruthiae and T. terengganuensis from Peninsular Malaysia (eight species) and T. praetermissa from Peninsular Malaysia and Singapore (one species) are described and illustrated. Distribution maps are provided and conservation status is assessed for the new species. Thottea dependens and T. tricornis are redefined and T. parviflora is lectotypified. Thottea is now represented by 16 species in Peninsular Malaysia and two in Singapore. A spherical-ovoid shaped perianth with an aperture at the top is observed for the first time in Thottea. The white and bicoloured perianth are described for the first time in Peninsular Malaysian Thottea. Eight out of the nine novelties fall in the IUCN ‘Threatened’ category, and six of them are considered as ‘Critically Endangered’.