Sciaphila sugimotoi Suetsugu & T. Nishioka, 2017

Suetsugu, Kenji & Nishioka, Tatsuki, 2017, Sciaphila sugimotoi (Triuridaceae), a new mycoheterotrophic plant from Ishigaki Island, Japan, Phytotaxa 314 (2), pp. 279-284 : 280-282

Sciaphila sugimotoi Suetsugu & T. Nishioka , sp. nov. ( Figs. 1–2 )

Type:— JAPAN. Ryukyu. Okinawa Pref., Ishigaki City, Hirae , alt ca. 180m, 18 October 2016, T. Sugimoto s.n. (holotype KYO!; isotype OSA!) .

Diagnosis:— Sciaphila sugimotoi is similar to Sciaphila arfakiana Beccari (1890: 337) , but it differs by its shorter pedicel, its filament-connective not extended and its thick stem.

Mycoheterotrophic, perennial herb. Plant erect, pinkish purple to reddish purple, non-branched or branched at the base, white underground. Roots filiform, hairy. Scale leaves acute, ca. 1.5 mm long. Inflorescences glabrous, ca. 5–7 cm tall, ca. 0.6–0.8 mm thick. Rachis, 1–4 cm long, ca. 10–35 flowers spirally arranged all around with male flowers generally on upper part. Pedicels ca. 1.5–4.0 mm long, longer than flower, patent at 30–60°, straight or slightly apically recurved; bracts minute, linear acute, ca. 1–1.5 mm long, appressed to the pedicel. Male flowers ca. 1.5–2.0 mm across, perianth segments 6, connate at base, segments narrowly ovate, glabrous, apex acute with a globose knob at apex, three segments slightly broader than alternating three acuminate segments. Stamens three, filament-connective not extended; filaments sessile. Anthers four-lobed. Female flowers ca. 1.0– 1.5 mm across; perianth segments six, connate at base, more or less equal, ovate to triangular, apex acute without appendage. Carpels numerous, ca. 0.5 mm long, globose at apex; style subulate, acuminate, inserted laterally; fused along the side of carpel, ca. 0.5–0.8 mm long.

Distribution, phenology and conservation status: — To date, the distribution of Sciaphila sugimotoi appears to be restricted to two localities, separated by ca. 3 km, on central Ishigaki Island in the Ryukyu Islands (Okinawa Prefecture, Japan). The two known S. sugimotoi population occurs at an elevation of approximately 80–180 m within a humid evergreen broadleaf forest dominated by Castanopsis sieboldii (Makino 1910: 232) Hatusima (1971: 223) and Distylium racemosum Siebold & Zuccarini (1841: 179) . Sciaphila sugimotoi flowers in mid-September to mid-October and each location consists of only dozens of flowering individuals. The two population of S. sugimotoi contains less than 50 flowering plants, and at present, we are not aware of any other locality where this species persists. Therefore, S. sugimotoi should be assigned a risk of extinction of “Critically Endangered” [CR B1ab(iii)+B2ab(iii)+D1] following the IUCN Red List ( IUCN 2012). Since this mycoheterotrophic species is completely dependent on its unique relationship with its host fungi for survival (e.g. Suetsugu et al. 2014a), it would be necessary to conserve the entire ecosystem in order to protect these endangered plants.

Etymology:— The new species is named after Mr. Takaomi Sugimoto, who collected ample specimens of this new species for the comparative study.

Additional specimens examined: — JAPAN. Okinawa Pref., Ishigaki City, Miyaera , alt. ca. 80 m, 21 October 2016, T. Sugimoto s.n. (OSA) ; Hirae , alt ca. 160m, 30 September 2016, T. Nishioka s.n. (OSA) .

Taxonomic note:— Sciaphila sugimotoi is similar to S. arfakiana Beccari (1890: 337) in having a stipitate globose to ellipsoid knob without hairs in apices of all male perianth segments. However, it is clearly distinguishable by its shorter pedicel (1.5–4.0 mm vs typically 7–9 mm), status of filament–connective (not extended vs. extended into a long appendage, ca. 1.3 mm long), thick stem, (0.6–0.8 mm vs 0.3–0.5 mm), shorter style (0.5–0.8 mm vs 1.0 mm). Sciaphila sugimotoi is also similar to the species that Hsieh et al. (2003) recorded as S. ramosa Fukuyama & Suzuki (1936: 410) , due to the similarity of a stipitate globose to ellipsoid knob without hairs in apices of all male perianth segments. It should be noted that S. ramosa sensu Hsieh et al. (2003) should have different taxonomic identity from original S. ramosa , because of the number (6 for S. ramosa sensu Hsieh et al. (2003) vs 4–6 for original S. ramosa ) and character (equal in shape and size without a knob at apex for S. ramosa sensu Hsieh et al. (2003) vs. three larger alternating with three smaller segments each with a stipulate globose knob at apex for original S. ramosa ) of male perianth segments. Considering these facts, it is even possible that S. ramosa sensu Hsieh et al. (2003) is identical to S. sugimotoi . Further exploration is needed to elucidate the taxonomic identity of S. ramosa sensu Hsieh et al. (2003) .

Figures

FIGURE 1. Habit (A) and microscopic images (B, C, D) of Sciaphila sugimotoi. A. Flowering plant.B–C. Male flower. D. Female flower. Photographed by Takaomi Sugimoto in the type locality.

FIGURE 2. Sciaphila sugimotoi from type locality.A. Flower plants, B. Male flower, C. Female flower. D. Female flower at fruiting stage with persistent perianth segments. E. Anthers with floral disc. F. Immature carpel with stigma. G. Immature fruit. Bar = 1 cm (A), 1 mm (B–D) and 0.1 mm (E–G). Drawn by Kumi Hamasaki.