Thismiadomei and T.terengganuensis (Thismiaceae), two new species, and T.javanica, a new record from Terengganu, Peninsular Malaysia

Abstract Two new species of the mycoheterotrophic genus Thismia Griff. (Thismiaceae), Thismiadomei Siti-Munirah and T.terengganuensis Siti-Munirah from Peninsular Malaysia, are described and illustrated. Thismiadomei, characterized by its perianth lobes that are upright and curve inward, but are imperfectly connate, falls within sectionOdoardoa. Thismiaterengganuensis is characterized by its mitre with three appendages on its apex, so falls within sectionGeomitra. Both new species are unique and totally different from other described species, T.domei by the trichomes on its outer perianth tube surface and T.terengganuensis by its mitre with slender appendages. Thismiajavanica J.J.Sm, also from Terengganu, is a new record for Peninsular Malaysia.


Introduction
Thismia, a genus of small, mycoheterotrophic herbs, currently comprises about 70 accepted species (Hroneš et al. 2018;Suetsugu et al. 2018). In 2018, eight new species were described from East Malaysia (Sabah and Sarawak). We can expect more new species in future. Thismia is poorly known because the above-ground parts are ephemeral and are often overlooked due to their small size. Well-preserved herbarium specimens are rare but spirit-preserved material and field images are informative. Currently in Malaysia, including these two new species and the new record, there are 27 species. Thirteen occur in Peninsular Malaysia, namely: Thismia alba Holttum ex Jonker, T. arachnites Ridl., T. aseroe Becc., T. chrysops Ridl., T. clavigera F. Muell., T. crocea (Becc.) J.J.Sm, T. fumida Ridl., T. grandiflora Ridl., T. javanica J.J. Sm., T. kelantanensis Siti-Munirah, T. racemosa Ridl., (Jonker 1948, Siti Munirah 2018 and the two new species described here. However, based on Jonker (1948), T. crocea is considered as highly dubious for Peninsular Malaysia. Its status in Peninsular Malaysia needs to be revisited.
Endemism is high, about half the Peninsular Malaysian species are endemic to Peninsular Malaysia and T. kelantanensis, T. racemosa, T. grandiflora and T. chrysops have only been collected once. Thismia alba, T. arachnites, T. clavigera and T. javanica also occur in Thailand; and T. fumida and T. aseroe in Singapore. The most common species, which is found from many places in Peninsular Malaysia, is the bright yellow species, T. alba.
The two new species and Thismia javanica were discovered by the second author, Mr Dome Nikong during a photographic trip in the Hulu Telemong Forest Reserve (FR) area, in the state of Terengganu, Peninsular Malaysia (Map 1). Hulu Telemong FR, located to the north of Kenyir Lake, was previously logged for timber. However, some patches of pristine primary rain forest have survived.

Materials and methods
This study is based on material collected by the second author in November and December 2018 from Hulu Telemong FR, Kuala Berang District, Terengganu. The specimens were preserved in spirit. Morphological characters were studied using stereo microscope and high-resolution macrophotography. Measurements were taken from live and spirit material. The specimen details were compared in detail with original drawings and descriptions given in the protologues of Thismia species in the Malaysian region.

Taxonomic account
Thismia domei M.Y.Siti-Munirah, sp. nov. urn:lsid:ipni.org:names:77198712-1 Figures 1, 2, 3 Diagnosis. The whole plant is completely white translucent and the flower is strigose with white trichomes covering the outer surface of the perianth tube and ovary; the apex of the perianth tube is partially covered by the apical part of flower tube with a ring-like annulus and together with six perianth lobes are upright and curve inwards with a dorsal long appendage on each lobe.
Distribution. Endemic in Peninsular Malaysia, Terengganu. Currently known only from the type collection.
Ecology. In lowland dipterocarp forest on wet, moist soil in shade at an altitude of 207 m. Flowering in November-December. This new species was encountered on bamboo leaf litter near an elephant trail. When mature T. domei produces an unpleasant smell like rotting fish.
Etymology. The species is named after Mr Dome Nikong, professional photographer and freelance researcher, who first discovered this species and the other new species described below as well as T. javanica.
Conservation status. Critically Endangered (B2 ab(iii)). Following the 2012 IUCN Red List Categories and Criteria, (IUCN 2012), this species is assessed as critically endangered because it is only known from the type locality. It is very rare. Fewer than 10 individuals were observed, which included both flowering and fruiting individuals. The type locality is within a forest reserve in disturbed forest area near the river bank at an elevation of c. 207 m. The species is under threat because selective logging activities are currently on-going within the forest reserve.
Notes   curved inwards towards the perianth tube with an appendage on each lobe. However, T. domei differs from these species in that its perianth tube is fully covered with thick trichomes and it has six perianth lobes each with an appendage as opposed to being completely glabrous and T. taiwanensis from Taiwan has only three perianth lobes with appendages and the perianth of T. clavarioides forms a mitre from Australia. T. domei is unusual in its conspicuous cell inclusion white spot which appear to be aleurone grains. Diagnosis. Thismia terengganuensis is unique in its perfect mitre with the long filiform appendages not seen in any other species of Thismia. It has a racemose sessile inflorescence with large bracts. Its flower parts are brownish with brown striae with inner perianth lobes forming a dark brown mitre with a white slender appendage attached at apex. The outer perianth lobes at interval appear like a wing. It has creeping vermiform brown roots.
Distribution. Endemic in Peninsular Malaysia, Terengganu. Currently only known from the type locality.
Ecology. In lowland dipterocarp forest on wet, moist soil in shade at altitude 227 m. Flowering in November-December on forest floor under canopy of dense shrubs.
Etymology. The epithet refers to the state, Terengganu, where it was found. Conservation status. Critically Endangered (B2 ab(iii)). Following the 2012 IUCN Red List Categories and Criteria, (IUCN 2012), this species is assessed as critically endangered because it is only known from one locality where less than 5 individuals flowering and fruiting individuals were observed. Thismia terengganuensis is currently known only from the type locality and is certainly a very rare species. The locality is within the forest reserve but is threatened by selective logging activities within the forest reserve that are currently ongoing.  Notes. Thismia terengganuensis is most similar to species in sect. Sarcosiphon and sect. Geomitra in the shape of the perianth tube and mitre but differs in all other morphological parts, e.g. in its slender filiform appendages on the apex of mitre and also its connectives that are blunt without any apical appendages.
Notes. The specimens of Thismia javanica were found not far from the T. terengganuensis population. We believe that T. javanica has a wider distribution in Peninsular Malaysia based on photographs of a specimen from Langkawi, Kedah, by late Abd Ghani Hussain. Unfortunately, there are no specimen to verify this.