Thismia brunneomitroides Suetsugu & Tsukaya, 2017

Suetsugu, Kenji, Tsukaya, Hirokazu, Tagane, Shuichiro, Suddee, Somran, Rueangruea, Sukid & Yahara, Tetsukazu, 2017, Thismia brunneomitroides (Thismiaceae), a new mycoheterotrophic species from southern Thailand, Phytotaxa 314 (1), pp. 103-109 : 104

Thismia brunneomitroides Suetsugu & Tsukaya , sp. nov. ( Figs. 1 & 2 )

Type:— THAILAND, Nakhon Si Thammarat Province, Khao Luang National Park, along trail to Kung Ching Waterfall, in lowland evergreen forest, 8°43’12.67”N, 99°40’31.11”E, elev. 285 m, 15 December 2015, Tagane S., Toyama H., Nagamasu H., Rueangruea S., Hemrat, C., Keiwbang W. T 4968 (holotype BKF!–a spirit collection, isotype TNS!–a spirit collection).

Diagnostic characters:— Thismia brunneomitroides is most similar to Thismia brunneomitra Hroneš, Kobrlová & Dančák (2015: 173) from Brunei Darussalam in having inner tepal lobes connate to form a mitre with three projections at the apex and large lateral appendage of the connective. However, it differs from T. brunneomitra in having ivory flowers with twelve pale orange to brownish orange vertical stripes on the perianth tube (vs. brown to blackish flowers with twelve darker vertical stripes on the perianth tube) and slightly dentate lateral appendage of the connective which does not exceed apical part of the connective (vs. entire lateral appendage of the connective which exceeds whole apical part of the connective).

Small, achlorophyllous mycoheterotrophic herbs. Underground parts coralliform, slightly branched towards the apex, hairy, whitish brown. Stem 5.0–8.0 cm tall, ascending to erect, simple, sparsely shortly hairy, ivory. Leaves spirally arranged, appressed, scale-like, triangular, ca. 5 mm long, 2–3 mm wide at base, apex acute, margin entire, pale orange to pale brown, membranaceous, glabrous. Inflorescence terminal, (1–)2–4 flowered. Floral bracts 3, similar in shape to leaves but slightly larger, 5–7 mm long, 3–3.5 mm wide at base, keeled, enveloping base of flower, pale orange to pale brown. Flowers bisexual, 1.3–1.6 cm long, 0.7–0.8 cm wide at top of perianth tube; perianth actinomorphic with 6 tepals fused to a perianth tube; outer surface verrucose with 12 longitudinal ribs, ivory with 12 vertical pale orange to brownish orange stripes; inner surface slightly verrucose, ivory; outer tepal lobes absent; inner tepal lobes well-developed, connate at top and forming mitre with three lateral holes, 4–6 mm in height; holes transversally elliptic to almost circular, 2–4 mm high, 3–5 mm wide; mitre pale orange to reddish-brown, topped by three acute projections. Annulus absent. Stamens 6, pendulous from top of perianth tube, pale brownish orange; connectives flattened, ribbon shaped, connate to form tube ; individual connective bearing 4 whitish thecae with 2 tufts of glandular hairs on adaxial side; teeth on free apical part terminated by tuft of glandular hairs, mostly 2, both teeth obtusely triangular, similar in shape and size; rarely 3, middle lobe narrowly triangular, lateral lobes larger, obtusely triangular teeth on free apical part; lateral appendage of connective flattened, wing-like, slightly dentate, not exceeding apical part of the connective, with marginal glandular hairs. Style short, ca. 0.4 mm long, with 3 bilobed stigmas, stigma ca. 1.2 mm long; ovary cup-shaped, with 12 pale brownish orange vertical ribs on surface. Capsule cup-shaped, pale brownish orange, strongly verrucose, topped by basal ring of perianth tube and withered style and stigmas. Seeds not seen.

Etymology: —The new species is named after the great morphological similarity to T. brunneomitra .

Habitat and Ecology: —Less than 10 individuals were found in shaded understory of lowland evergreen forest. No other mycoheterotrophic species were found in the locations in which the new Thismia were collected.

Preliminaryconservationassessment: —CriticallyEndangered,[CRD1].( IUCN2012). Thismiabrunneomitroides is currently known only from a single population in lowland evergreen forest in Khao Luang National Park. The population of contains less than 10 mature plants, and at present we are not aware of any other locality where this species persists. Therefore, T. brunneomitroides is classified as CR under Criterion D1.

Taxonomic notes: — Thismia brunneomitroides apparently belong to the section Sarcosiphon Blume (1850: 65) in having a coralliform underground part and inner tepal lobes fused at the top and forming a mitre. Among the members of the section Sarcosiphon , T. brunneomitroides is most similar to T. brunneomitra in having inner tepal lobes connate to form a mitre with three projections at the apex and large lateral appendage of the connective ( Hroneš et al. 2015), but these two species are distinguished by morphological characters shown in Table 1. Thismia brunneomitroides also resembles T. episcopalis ( Beccari 1877: 250) Mueller (1891: 235) but differs by the mitre having 3 acute projections at apex (vs. obtuse without any projection in T. episcopalis ) and mostly 2 teethed apical part of connective (vs. 3 teethed apical part of connective). Among Thai species, T. brunneomitroides is similar to Thismia sp. recently recorded as ‘ T. clandestina ’ ( Blume 1850: 65) Miquel (1859: 616) by Chantanaorrapint et al. (2015) from Peninsular Thailand. T. brunneomitroides and ‘ T. clandestina ’ in the sense of Chantanaorrapint et al. (2015) share outer morphological appearance such as ivory flowers with twelve pale orange to brownish orange vertical stripes on the perianth tube and verrucose outer surface of perianth tube. However, T. brunneomitroides is distinguished from ‘ T. clandestina ’ sensu Chantanaorrapint et al. (2015) by the mitre having 3 longer acute projections at apex (vs. very short acute projections at apex in ‘ T. clandestina ’ of Thailand) and much larger stigmas (ca. 1.2 mm long in T. brunneomitroides vs. ca. 0.5 mm long in ‘ T. clandestina ’ of Thailand). It should also be noted that T. clandestina sensu Chantanaorrapint et al. (2015) may be different taxonomic identity from T. clandestina (Blume) Miq. described from Java ( Miquel 1859, Smith 1911) because T. clandestina sensu Chantanaorrapint et al. (2015) has somewhat different morphological characters from T. clandestina from Java such as the teeth on the free apical part of connective (mostly 1, wide, triangular vs. 2–3, asymmetrical, with additional several bristlelike laciniae) and size of mitre (6 mm vs. 2–4 mm in height; Smith 1911, Hroneš et al. 2015, Chantanaorrapint et al. 2015). Further exploration will be needed to elucidate the taxonomic identity of ‘ T. clandestina ’ in the sense of Chantanaorrapint et al. (2015).

Figures

FIGURE 1. Thismia brunneomitroides from the type locality.A. Flowering plant. B–C. Flowers. D. Longitudinal section of perianth tube with anthers and style. E. Stamen with lateral appendage and thecae, outer view. F. Style. Bar = 1 cm (A–C), 5 mm (D) and 1 mm (E–F).

FIGURE 2. Thismia brunneomitroides. A. Flowering plant. B. Flower. C. Longitudinal section of flower. D. Immature fruit. E. Style. F. Stamen with apical lobes, inner view. G. Stamen with lateral appendage and thecae, outer view. Materials from Tagane et al. T4968. Drawn by Kumi Hamasaki. Bar = 1 cm (A–C), 5 mm (D) and 1 mm (E–G).