﻿Thismiakenyirensis (Thismiaceae), a new species from Taman Negeri Kenyir, Terengganu, Peninsular Malaysia

﻿Abstract A new mycoheterotrophic species, Thismiakenyirensis Siti-Munirah & Dome from Peninsular Malaysia, is described and illustrated. Thismiakenyirensis differs from other previously described species in the following characteristics: the flower tube is completely orange, with alternating darker and paler-coloured longitudinal lines on the outer and inner surfaces, the outer tepals are ovate (petaloid), the inner tepals are narrowly lanceolate, each ending with a long appendage. According to the IUCN Red List categories and criteria, T.kenyirensis is provisionally classified as Least Concern.


Introduction
Thismia Griff. is a genus of non-photosynthetic flowering plants belonging to the family Thismiaceae. Thismia species are small herbs, with scale-like leaves and actinomorphic or zygomorphic, urceolate to campanulate flowers. Thismia includes about 100 species worldwide (from Imhof 2010 onwards, Siti-Munirah et al. 2022) and it is the most widespread and species-rich genus in the family Thismiaceae with high endemism. Their range extends from tropical and subtropical Asia to northern and eastern Australia and New Zealand and from tropical South America to Costa Rica, with isolated occurrence in North America (POWO 2022). Many species are believed to be extremely rare and have a scattered range. They are easily overlooked in the wild due to their small size and the short-lived nature of their aboveground parts (Larsen and Averyanov 2007). In Malaysia, Terengganu is currently the state with the most Thismia records, with 11 reported species: T. alba Currently, five of the species reported in Terengganu are known from the Kenyir State Park (Taman Negeri Kenyir, TNK) (Siti-Munirah and Dome 2022b). The TNK is located in the eastern part of Peninsular Malaysia in the state of Terengganu (Map 1). It used to be part of the Tembat Forest Reserve (FR), but in 2018 and 2019, parts of Tembat FR were designated as TNK. The forest area includes part of the forest around Tasik Kenyir (Kenyir Lake), which is adjacent to Terengganu National Park (Taman Negara Terengganu) and also connected to Tembat FR forest and Kelantan State (Map 2). During the scientific expedition to the TNK on 8 September 2020, the second author and his team visited the Sungai Cendana area in the southern part of the TNK and discovered a population of an unknown Thismia plant, which he forwarded to the first author. Together, we revisited the populations in June 2022. After further investigation and comparison with known species of Thismia, we concluded that this plant is distinct from previously described species of the genus. We therefore report and describe it here as a new species for science.

Materials and methods
Our assessment is based on material collected in Taman Negeri Kenyir, Hulu Terengganu, Terengganu (Map 1). The specimens were preserved in 70% ethanol. All the specimens have been deposited in Kepong Herbarium (KEP) and have been examined for taxonomic treatment. Morphological characters and measurements were examined using an Olympus SZ61 stereo microscope and high-resolution macrophotography. Additionally, measurements were taken from spirit material. The specimen features were compared in detail with the original drawings and descriptions of morphologically similar species of Thismia provided by Jonker (1938), Larsen and Averyanov (2007), Mar and Saunders (2015), Chantanaorrapint (2018), Tanaka et al. (2018), Suetsugu et al. (2018), Siti-Munirah and Dome (2019) and Nuraliev et al. (2020). Description. Achlorophyllous herb, up to 130 mm tall. Roots vermiform, unbranched, ca. 1 mm in diameter, light brown. Stem erect, up to 90 mm long, 1.5-2 mm in diameter, pale brownish-orange, bearing 1-2 flowers. Leaves 2-4, spirally arranged, triangular to narrowly triangular, scale-like, acute, margin almost entire but slightly irregularly serrate, 2-6 mm long, ca. 1 mm wide at base, pale brown. Involucral bracts 3, similar to leaves but slightly larger, spirally arranged, triangular to narrowly triangular, scale-like, acute, entire, 8 mm long, ca. 1.5-2.5 mm wide at base, pale brown or pale orange. Pedicel up to 6 mm long at anthesis, elongating to ca. 10 mm long after anthesis, pale brown. Flowers terminal, actinomorphic, ca. 52 mm long (including ovary, floral tube and inner tepal with appendage); floral tube urceolate, 12-15 mm long, ca. 5 mm wide at base, ca. 6 mm wide at middle, ca. 7 mm wide distally; outer surface glabrous, orange to brownish-orange, with 12 darker orange longitudinal ribs alternating with 12 paler longitudinal lines, inner surface smooth or rough, almost similar to outer surface, without transverse bars or reticulate ornamentation; outer tepals 3, free, petaloid, ovate, apex acute, 8 mm long, ca. 4-5.5 mm wide (ca. 4 mm at base, ca. 5.5 mm above middle), glabrous, bright orange; inner tepals 3, free, narrowly lanceolate-linear, 8 mm long, ca. 1 mm wide, glabrous, dark orange, apically bearing a tentacle-like appendage; appendage narrowing towards apex, ca. 27-28 mm long, 0.5 mm wide, dark orange at base and bright orange at apex; annulus dark orange, glabrous. Stamens 6, pendent from the annulus, outer side greenish-orange or greenish-brown, inner side dark-brown to blackish and paler, filaments free, ca. 1 mm long, curved downwards; connectives flattened at inner surface, laterally connate to form a tube, ca. 4-5 mm long, narrow at base (ca. 0.8 mm wide) and broad at apex (ca. 1.7 mm wide), connective apex with 3 appendages, slightly curved inside, each appendage ca. 1.5 mm long; outer side of connective bearing a skirt-like lateral appendage protruding towards floral tube; lateral appendage not exceeding the tip of the connective appendages, with short translucent trichomes on margin, interstaminal glands greenish translucent, inserted on the line of fusion between connectives at the level of attachment of lateral appendages. Ovary inferior, unilocular; placentas 3, free, forming columns and arising from the bottom of the ovary; ovules numerous. Style dark brown-orangish, ca. 1 mm long; stigma ca. 1 mm long, papillose, 3-lobed, with lobes ± rectangular, bifurcate at apex, pale brown or orangish to whitish. Fruit cup-shaped, 3-5 mm in height, 4-6 in diameter, pale orange (or white to creamy orange), darker at upper part. Seeds unknown.   Distribution. Endemic to Terengganu, Peninsular Malaysia. Currently, the occurrence is only from the type locality, Sungai Cendana area (Map 1). In addition, T. kenyirensis was observed in two other populations in the vicinity of Tasik Kenyir. It was sighted near Sungai Saok and on the way to Gunung Gagau (Wong Pui May personal communication), both in the Tasik Kenyir region. However, there are still no specimens and GPS information to verify these findings. This means that only the occurrence of the population in Sungai Cendana has been confirmed.

Taxonomic account
Ecology. In moist shady areas of lowland dipterocarp forest on moist soil at elevations of 150-220 m a.s.l. Flowering and fruiting mostly from September to April, but also recorded to flower in June. Historically, the type locality was botanized as early as 2007. Based on the results of Lim et al. (2008), T. alba was also recorded during the survey in the Sungai Cendana area. This is in contrast to T. kenyirensis, which was not mentioned, implying that it was not seen or collected at that time. During our recent visit, we were also able to find T. alba not far from the original population of T. kenyirensis.
Etymology. The epithet refers to Lake Kenyir, Kenyir State Park (Taman Negeri Kenyir), where the species was found.
Conservation status. According to the IUCN standards (IUCN 2022), we propose to classify the preliminary conservation status of the species as Least Concern (LC). This is because the species is likely to be widespread in TNK, where it has been sighted a few times at the type locality (Sungai Cendana) and also by other observers at two other sites, and its entire habitat is in a fully protected forest area. In addition, nearby forests in Terengganu National Park (Taman Negara Terengganu) are also fully protected. As mentioned earlier, it is very likely that there are other populations in the vicinity of Tasik Kenyir. According to the second author's observations, four individuals were sighted near Sungai Saok and one on the way to Gunung Gagau on 22 November 2022. However, no specimens are available for confirmation. Thismia kenyirensis occurs in intact habitats in forested areas in TNK. However, the species is very common only during the flowering season and its populations are mostly scattered, as few individuals or solitary individuals were observed during the flowering season. During the first check of the type locality, the population in Sungai Cendana in 2020, about 20 adult individuals were found. However, during a revisit in 2022, only a single individual was observed.

Colour of floral tube
Orange  reconstruction provided by Shepeleva et al. (2020), T. javanica, T. hongkongensis, T. gardneriana and T. tentaculata occupied a relatively isolated and unstable position. All these species (and also T. kenyirensis) are characterised by free appendaged inner tepals and outer tepals without appendages. A more detailed phylogenetic analysis is required to test the monophyly of this morphological group, and the relationships of each of these species including T. kenyirensis.