Thismia dasyantha Dančák, Sochor & Hroneš, 2025

Dančák, Martin, Hroneš, Michal, Sochor, Michal, Uvírová, Alena, Blažek, Vojtěch Tobias, Yunoh, Siti-Munirah Mat & Yiing, Ling Chea, 2025, Thismia velaris and T. dasyantha, two new species of Thismia section Thismia subsect. Odoardoa (Thismiaceae) from Sarawak, Malaysia, Phytotaxa 715 (2), pp. 117-128 : 122-125

Thismia dasyantha Dančák, Sochor & Hroneš , sp. nov. Fig. 3 & 4

Diagnosis: — Thismia dasyantha is distantly similar to T. pallida but differs in annulus indistinct, flat, with opening ca. 1 mm in diameter (vs. annulus distinct, raised, with opening ca. 2 mm), the opening resembling a schematic outline of a hexamerous angiosperm flower (vs. opening circular), tepals basally connate, 2.5–3 mm wide at the base (vs. free, ca. 2 mm wide at the base), tepal appendages 10–14 mm long (vs. ca. 3 mm long), three appendages (vs. five appendages) on supraconnective apex, the middle appendage being the shortest (vs. the longest), and stigma lobes deeply bifid (vs. shallowly notched).

Type: — MALAYSIA. Sarawak: Bintulu Division, Tatau District, Rumah Agau, small patch of primary lowland mixed dipterocarp forest 900 m NW from the longhouse, 50 m a.s.l., 2.6346689N, 112.9343375E, 21 November 2023, Dančák & Hroneš MDMH 2023/32 ( holotype SAR! [in spirit]).

Description:—Achlorophyllous herb, ca. 4–6 cm tall. Roots creeping, vermiform, ± horizontal, sparsely branched, ca. 1 mm thick, pale brown. Stem 2.5–4 cm long, erect or ascending, smooth, pale brown, bearing 1 or 2 flowers. Leaves 3.0–4.5 × 1.4–2.1 mm, spirally arranged, appressed, scale-like, narrowly triangular, acute, entire, of the same colour as stem. Bracts 3, similar to leaves but 7–12 × 1.7–3 mm. Flowers subsessile, actinomorphic,

ca. 12–16 mm long. Floral tube 9–11 mm long, 6–7.5 mm wide at the apex, symmetric, campanulate to funnelshaped; outer surface pale brown, sometimes tinged with orange or pink, set by few to numerous whitish verrucae up to 1.5 mm long, with 12 red to brown longitudinal veins clearly extending above the surface of the tube as low ribs; inner surface with whitish to cream reticulation, without transvers bars. Annulus indistinct, thin, flat, with gradual transition to tepal bases, brown to red-brown; opening very narrow, distinctly raised above the surface; inner margin forming a hexaradial figure resembling a schematic outline of a hexamerous angiosperm flower. Tepals 6, equal in shape and size, 4–6 mm long, 2.5–3 mm wide at base, narrowly triangular to broadly lanceolate in outline, fused with each other at the base, either uniformly pale brown to coral pink or bordered by darker shade; abaxial surface verrucose; filiform appendage arising from the abaxial side of tepal, 10–14 mm long (measured from the tepal tip), D-shaped in cross section (flat adaxially), apically unswollen, whitish to pinkish. Stamens 6, pendent from the top of floral tube; filaments arcuately curved in both transversal and longitudinal view, red-brown; connectives flattened, laterally connate to form a tube; each connective 3.6–3.9 × 1.5–1.8 mm, brown to red-brown at base, amber-coloured in the middle and colourless and translucent at the apex; supraconnectives free, apically with 3 appendages, outer appendages longer than the middle one; lateral appendage skirt-like, white translucent, with two bilobed lateral wings, the upper wing bearing several hairs; the middle part with dentate apical margin, not exceeding the apices of the supraconnective appendages; interstaminal gland inserted on the line of fusion between connectives, globose. Style ca. 0.8 mm long, dull grey-green to pinkish brown; stigma 3-lobed; lobes ca. 1 mm long, deeply bifid, hairy, concolorous with style or sometimes lighter. Ovary inferior, 3–3.7 × 3–4.5 mm, obconical, verrucose to hairy, cream to pale brown with dark vertical stripes in the upper half. Fruit an obconical pale brown capsule. Seeds not seen.

Additional field records: — MALAYSIA. Sarawak: Bintulu Division, Tatau District, Rumah Agau, small patch of primary lowland mixed dipterocarp forest 900 m NW from the longhouse, 50 m a.s.l., 2.6346689N, 112.9343375E, 3 December 2024, photo M. Hroneš.

Habitat: —The only population was found in lowland mixed dipterocarp forest on a steep slope at the bottom of a shallow valley in a small remnant of primary forest among logged forests and forest clearings.

Distribution: — Thismia dasyantha is only known from the type locality in central Sarawak.

Conservation status: —While the extent of occurrence (EOO) of T. dasyantha cannot be calculated from a single point, the area of occupancy (AOO) is formally estimated at 4 km ². However, the actual AOO is much smaller, as the only known population is confined to an isolated patch of primary forest not larger than 0.05 km ². Moreover, the site lies outside protected areas, and the number of known individuals is far below 50. Consequently, T. dasyantha is preliminarily assigned a conservation status of CR (B2ab, D) according to the guidelines of the IUCN Standards and Petitions Subcommittee (2025).

Etymology: —The specific epithet is derived from the Greek words dasýs, meaning “hairy” and ánthos, meaning “flower”, referring to the prominent verrucae present on the outer surface of the floral tube, ovary and the abaxial side of the tepals, which resemble hairs.

Notes: — Thismia dasyantha does not show a close morphological similarity with any previously known species of the genus. It is unique within Thismia sect. Thismia subsect. Odoardoa by the combination of basally fused tepals (so far observed within T. sect Thismia subsect. Odoardoa only in T. annamensis ) and hexaradial flower opening resembling a schematic outline of a hexamerous angiosperm flower ( Fig. 3F ). The other conspicuous feature of this species is the presence of verrucae covering the floral tube, ovary, and the outer surface of the tepals, particularly in flower buds and young flowers. The length ( 0.5–1.5 mm) and density of these verrucae vary among individual plants within the single known population, giving some individuals a “hairy” appearance ( Fig. 3E ). Although various terms are used to describe verrucae in other Thismia species, such as papillae in T. papillata Nuraliev & Yudina ( Nuraliev et al., 2024: 262) and tubercles in T. tuberculata Hatusima (1976: 4) , the term “verrucae” is applied here in the same sense as e.g., in T. nigricoronata Kumar & S.W. Gale ( Kumar et al., 2017: 234) and T. viridistriata Sochor, Hroneš & Dančák ( Sochor et al., 2018) .

In the diagnosis, we stated the newly described species to be most similar to T. pallida Hroneš, Dančák & Rejžek in Hroneš et al. (2018: 115), but the two species are not closely related phylogenetically ( Fig. 5 ). Instead, in our phylogenetic reconstructions, T. dasyantha clusters with the morphologically distinct T. neptunis and T. cornuta . The former has traditionally been placed in T. sect. Thismia subsect. Brunonithismia Jonker (1938: 242) or in its own section, T. sect. Sarawakia Schlechter (1921: 35) . However, the delimitation between T. sect. Thismia subsect. Brunonithismia and T. sect. Thismia subsect. Odoardoa , as well as the relationships of T. sect. Sarawakia requires further investigation.

Figures

FIGURE 3. Thismia dasyantha. A–C. Overall appearance. D. Top view of flower. E. Distinctly verrucose flower bud and dissected floral tube showing position of stamen tube. F. Annulus with a hexaradial figure resembling a stylised outline of a flower on its inner margin. G. Outer view of stamen. H. Inner view of stamens. I. Style and stigma viewed from above. J. Fruiting plant with elongated pedicel and capsule. Photos by V. T. Blažek (A, I) and M. Hroneš (B, D, E, G, H) from Dančák & Hroneš MDMH2023/32 and M. Hroneš (C, F, J) from uncollected plants recorded at the same site in 2024.

FIGURE 4. Thismia dasyantha. A. Habit of flowering plant. B. View of the flower from the top. C. Dissected floral tube showing outer view of stamens, style and reticulate structure on the inner surface of the floral tube. D. Dissected floral tube showing inner view of stamens, style and reticulate structure on the inner surface of the floral tube. Drawn by Nela Malá Dančák & Hroneš MDMH2023/32.

FIGURE 5. Bayesian phylogenetic tree based on five markers (LSU, ITS, SSU, atpA, matR) focused on the Thismia section Thismia subsect. Odoardoa, showing the phylogenetic positions of T. velaris and T. dasyantha; posterior probabilities are shown above branches.