Thismia sitimeriamiae Siti-Munirah, Dome & Thorogood, 2021

Siti-Munirah, Mat Yunoh, Dome, Nikong & Thorogood, Chris J., 2021, Thismia sitimeriamiae (Thismiaceae), an extraordinary new species from Terengganu, Peninsular Malaysia, PhytoKeys 179, pp. 75-89 : 75

Thismia sitimeriamiae Siti-Munirah, Dome & Thorogood sp. nov.

Figures 1 , 2 , 3 , 4

Diagnosis.

Thismia sitimeriamiae has a unique combination of morphological traits, by which it differs from all its congeners including its orange colour, its surface characteristics and its floral architecture: the flower is strigose with pale orange simple and stellate trichomes covering the outer surface of the floral tube, mitre and ovary; the upper surface of the annulus is covered by very short trichomes; the outer tepals are reduced and inconspicuous and the inner tepals are curved upwards, connate, forming an umbrella/parasol-like mitre with a flattish apex.

Type.

Malaysia. Peninsular Malaysia: Terengganu, Setiu District, Hulu Nerus Forest Reserve , ca. 209 m alt., 23 December 2019, Dome Nikong, FRI 91118 (holotype KEP!, spirit collection, No. barcode 280006) .

Description.

Achlorophyllous herb, ca. 2.2 cm tall. Roots coralliform, creeping, light brown. Stem 8 mm tall, erect-ascending, unbranched, 2 mm thick, whitish. Leaves ca. 6, spirally arranged, triangular, scale-like, acute, entire, 3-4 mm long and 1 mm wide at base, pale whitish. Bracts 3, widely triangular to ovate, entire, acute to acuminate, ca. 5 mm long, 2 mm wide, pale greenish to brown. Pedicel 1 mm long, elongating after anthesis, greenish. Inflorescence (flower) solitary, actinomorphic, ca. 1.5 cm long; pale to dark orange; floral tube (hypanthium) conical in shape, ca. 1 cm in height, widest (1.2 cm) in the upper part; outer surface bright orange, sparsely covered with pale orange, simple trichomes (occasionally apically stellate); inner surface partially convex/reticulum; outer tepals 3, rather reduced and inconspicuous, divided, forming a narrow overhanging fringe around the mouth of the perianth tube; inner tepals well-developed, each pale orange, distally connate, forming a flattish, umbrella-like mitre ca. 3-4 mm tall, proximally flattened with revolute margins, arching over the floral tube; mitre circular in outline, ca. 8-10 mm wide, the upper surface bright orange, covered sparsely with orange trichomes, the lower surface glabrous, bright orange; annulus (apical part of the floral tube) pale orange, rounded, ca. 1.2 cm wide, the rim raised, connected with the inner tepals; upper surface covered with short trichomes; aperture, ca. 4-5 mm, with a blackish margin; stamens 6, orange, pendent from the annulus; filaments orange, curved downwards, connectives laterally connate, forming a tube, ca. 3 mm long, glabrous on the inner surface, the apex of each connective with two lobes, each pointed with transparent trichomes; outer side of connectives forming a lateral appendage, protruding towards the floral tube, horn-like on each side, shallowly dentate and sparsely hairy on the free margins; thecae pale, surrounded by tufts of hairs; interstaminal glands inserted along the line of fusion between the connectives; ovary inferior, obconical, flushed pale orange and greenish, covered by bracts; placentas 3, parietal; pistil slender, clavate, pale greenish-orange; style ca. 1.5 mm long, slender, erect, glabrous; stigma ca. 1 mm, papillose, 3-lobed, narrowly-rectangle, each without furrowed, orange; fruit a cup-shaped capsule, greenish, borne on an elongated pedicel up to 6 cm long; seeds brown.

Additional specimen examined

(paratype). Malaysia. Peninsular Malaysia: Terengganu, Setiu District, Hulu Nerus Forest Reserve, ca. 209 m a.s.l., 25 December 2020, Dome Nikong FRI 91123 (KEP, spirit collection, barcode 28007).

Distribution.

Endemic to Terengganu, Peninsular Malaysia. Currently known only from the type locality (Map 1 ).

Ecology.

Lowland dipterocarp forest on moist soil in shade at an elevation of 209 m a.s.l. Flowering and fruiting from December to February.

Etymology.

Thismia sitimeriamiae is dedicated to Siti Meriam, the mother of the second author (Dome Nikong), in honour of her unparalleled support for the conservation activities pursued by Dome Nikong and her help in maintaining his plant collections.

Conservation status.

In accordance with the IUCN Red List Categories and Criteria ( IUCN 2019), Thismia sitimeriamiae is assigned as Critically Endangered (CR), based on criterion B2 (ab (ii,iii)), because it is only known from the type locality, where fewer than five individuals have been observed (both in flower and in fruit), since survey work began.

Figures

Figure 1. Thismia sitimeriamiae A the habitat in Gunung Sarut, in the State of Terengganu (PM) B the habit of flowering specimen C a fruiting specimen (in situ).

Map 1. Hulu Nerus Forest Reserve (black circle), the type locality of Thismia sitimeriamiae.

Figure 2. Illustration of Thismia sitimeriamiae A cross section of perianth showing pendulous stamens (above) and slender pistil (beneath) B pistil C aerial view of flower showing mitre and portions of apical part of floral tube and outer tepals D fruit E stamen (showing outer side of connective) F flower, lateral view G habit, showing inflorescence (flower) and roots. All illustrated from FRI 91118 (excluding D, in situ).

Figure 3. Thismia sitimeriamiae A habit with roots B flower, view from below C aerial view of floral tube (mitre removed) D flower, aerial view E mitre, lateral view F ovary and pistil, lateral view G flower, lateral view H mitre, lateral view I stellate trichomes on the outer surface of floral tube. All from FRI 91118 (A-F) and a plant photographed in situ (G-I). Images not to scale (see dimensions in description and Figure 2).

Figure 4. Flower structure of Thismia sitimeriamiae A longitudinally dissected flower, showing inner side of stamens and pistil B stamens, (inner view) C lateral view of stamens showing lateral appendage (arrow) D lateral view of outer stamens in which interstaminal glands (arrow) are discernible. All photos from FRI 91123. For dimensions, see description and Figure 2.