Taxonomic treatment
Asarum pubitessellatum C.T. Lu & J.C. Wang, sp. nov.—TYPE: TAIWAN. Miaoli Hsien: Nanchuang Township, Mt. Chialishan, alt. 1,400 m, 12 Dec. 2005, C. T. Lu 812 (holotype: TNU; isotype: TAIF).
(Figure 1).
Diagnosis: Asarum pubitessellatum C.T. Lu & J.C. Wang is similar to A. crassisepalum S.F. Huang, T.H. Hsieh & T.C. Huang and A. taipingshanianum S.F. Huang, T.H. Hsieh & T.C. Huang but differs from the latter two by having larger plant body (20–30 cm vs. less than 10 cm tall); shortened rhizome; larger perianth-tube (ca. 1.5 cm vs. 1–1.2 cm in diam.); multicellular simple trichomes (vs. glandular trichomes) on the inner surface of perianth-tube.
Perennial herb. Rhizome short. Leaves 2 on each annual branchlet, with petiole 10–23 cm long. Leaf lamina triangular-ovate to sagittate, thick, 8.5–13 × 6–7.5 cm, acute to acuminate at apex, auriculate at base, base of the sinus 3–4.7 cm wide, glabrous adaxially, with white blotches along mid-vein, glabrous and pale green abaxially. Flowering branch with 2–3 cataphylls at its base, ovate, 16–18 mm long, margin ciliate, shed when leaves fully grown. Flowers solitary, facing downward, yellow-greenish to purple-greenish, perianth-tube conical, ca. 13–15 mm long, lower portion 12–13 mm in diam., upper portion 8–10 mm in diam., peduncle 10–18 mm long; outer surface glabrous, pale yellow-greenish and with numerous brownish red spots; internal surface purplish red, tessellated and with ca.12 longitudinal ribs, covered with numerous pubescences along longitudinal and transverse ribs. Tube throat slightly constricted, annual ca. 1–1.5 mm wide, orifice ca. 3–5 mm. Perianth-lobes 3, broadly triangular-ovate, yellow-greenish to purple-greenish, ca. 10–11 × 12–14 mm, spread, without forming semicircular pulvinate areas between the lobes and orifice. Stamens 12 in two whorls, filaments very short, anthers 2.5 mm long, with connective obtuse; ovary superior, 6-locular, styles 6, free, with slightly bifid apices; stigma oblong-ovoid, lateral, inserted in apex notch, extrorse; ovules 8 in each locule.
Pollen morphology
Pollen grains in A. pubitessellatum are oblate spheroidal to suboblate, penta-colporate in equatorial view (Figure 2C), ca. 25.5 × 27 μm–27 × 28.6 μm (P × E). Pollen tectum is perforate without supratectum granules (Figure 2F).
Habitat and geographical distribution
To date, this new species is only known from the type locality in Mt. Chialishan, Miaoli Hsien, Taiwan. It was found under a shaded and moist plantation of the coniferous species Cryptomeria japonica (L.f.) D. Don. The habitat is similar to those of its allies, A. crassisepalum and A. taipingshanianum, which grow in mixed coniferous-broadleaf forests, often among mosses. These three species all occur in cloudy forest zones at middle elevation but in geographically different areas. Asarum crassisepalum inhabits the mountainous area around Yuanyang Lake in Hsuehshan Mountain Range, A. taipingshanianum inhabits the mountainous area of Taipingshan in the Central Mountain Range, and A. pubitessellatum can only be found on Mt. Chialishan on the western side of the Hsuehshan Mountain Range (Figure 3).
Conservation assessment
Only two localities with less than 50 plant individuals of A. pubitessellatum have been found. The area of occurrence is estimated to be 10 km2. According to the IUCN red list categories (IUCN 2001) criteria, this species is categorized as critically endangered CR (B2abiii, C2a).
Etymology
We name this species A. pubitessellatum based on the inner surface of its perianth-tube being covered with numerous simple trichomes along ridges. This character is different from other Taiwanese, Chinese, and Japanese Heterotropa species, which have perianth-tubes that are covered with glandular trichomes.