Hosta alata Hatus. ex Yahara, 2021

Yahara, Tetsukazu, Hirota, Shun K., Fuse, Kengo, Sato, Hiroyuki, Tagane, Shuichiro & Suyama, Yoshihisa, 2021, Validation of Hosta alata (Asparagaceae) as a new species and its phylogenetic affinity, PhytoKeys 181, pp. 79-93 : 79

Hosta alata Hatus. ex Yahara sp. nov.

Figs 5 , 6 Japanese name: Bungo-giboshi

Diagnosis.

Hosta alata is distinguished from H. pulchella by the presence of more leaves (5-9 vs. 3-4), larger leaf blades (8.5-24.5 cm long vs. 2.7-8.0(-8.9) cm long), more lateral veins (5-9 pairs vs. 3-4 pairs), wider-winged petioles (0.4-1.4 cm wide vs. 0.2-0.4 cm wide), more flowers (9-40 flowers per scape vs. 3-4 flowers), longer pedicels (1.1-2.3 cm long vs. 0.5-0.8 cm long), and fertile bracts which are purplish green in color (vs. pale green).

Type.

Japan. Oita Pref.: Ogata-cho, Mt. Karasu-dake (recorded as Karasu-yama), September 15, 1995, with flowers, K. Nogami s.n. (holotype: KAG 151816!) .

Description.

Herbs perennial, up to 48 cm in height, including scape. Plants green (not whitish-green). Leaves basal, spiral, long petiolate, 5-9 per ramet; blades ovate or oblong-ovate, 8.5-20.5 × 3.7-15.0 cm, thinly papery, glabrous on both surfaces, base cuneate to subcordate, apex acute to short acuminate, acumen to 1 cm long, margin entire, veins in 5-9 pairs, smooth on the lower surface; petioles 6.0-15.5 cm long, 0.4-1.4 cm wide, winged, wings 0.5-2.0 mm wide, glabrous, reddish maculate proximally. Scape 20-48 cm, terete. Raceme 9-40-flowered; sterile bracts at low to middle part of rachis 2, longer than 3 cm, apex not seen (broken and disappeared); one fertile bract subtending each flower, vivid (not withering) in anthesis, erect or diagonally, purplish green, oblong-lanceolate, boat-shaped, 0.8-2.4 × 0.2-0.6 cm, membranous, glabrous, apex acuminate. Flowers not fragrant, 4.2-7.4 cm long; pedicels 1.1-2.3 cm long, glabrous. Perianth light purple, funnel-form, 3.0-5.4 cm long, glabrous, 6-lobed; tube ca. 0.2 cm wide at base, abruptly dilated from apical 2/3, to 0.7-1.4 cm wide at throat, lobes narrowly triangular, 0.9-1.2 cm long, apex acute. Stamens 6, slightly shorter than perianth, not exserted; filaments white, free, 3.4-4.2 cm long, glabrous, anthers yellow, 2.5-3.5 mm long. Ovary oblong-ellipsoid, ca. 8 mm long, glabrous, style 3.7-4.5 cm long, upwardly curved at the distal part, subequal to 0.2-0.3 cm exserted from perianth, glabrous, stigma capitate. Capsule dark purple, dotted, cylindrical, 1.7-2.3 × 0.3-0.5 cm, 3-angled.

Phenology.

Flowering from late August to late September, and fruiting in late September and probably to October.

Distribution and habitat.

Oita Prefecture, Japan (endemic). This species grows on rock cliffs in the southern part of the Oita Prefecture on the main island of Kyushu.

Etymology.

The specific epithet is derived from its winged petioles.

Conservation status.

This species is listed in the Red Data Book Oita ( Anonymous 2011) as Endangered (EN). The total number of fertile individuals in the two localities was estimated to range between 50 and 100. While the population of Mt. Sobo is located in the protected area of the Sobo Katamuki National (Kokutei) Park, the population occurring in Mt. Karasu-dake is not protected. It grows on steep rocky cliffs and the localities are not commonly known, and thus the populations appear stable. However, the formal description of this species may increase the collection pressure. Protection measures are currently being planned with administration.

Additional specimens examined.

Japan. Oita Pref.: Ogata-cho, Mt. Karasu-dake, on cliff, 676 m elevation, September 24, 2020, with flowers, T. Yahara et al. JPN2280 -2283(FU!); Ogata-cho, Ogouchi Forest Road, 780 m elevation [in the vicinity of the JPN2280 - 2283 collection site at Mt. Karasu-dake], September 19, 2001, photographs taken by M. Arakane (KAG 151818!); Mt. Sobo , August 23, 2000, with flowers, M. Arakane AR-43465 (KAG 151817!); Mt. Sobo , September 26, 2020, sterile, T. Yahara et al. JPN2350, 2351, 2372 (FU!) .

Figures

Figure 5. Holotype of Hosta alata Hatusima ex Yahara. (Nogami s. n. KAG 151816, available from https: // dbs. kaum. kagoshima-u. ac. jp / musedb / s _ plant / picture / KAG 151816 / KAG 151816. jpg).

Figure 6. Depiction of Hosta alata Hatusima ex Yahara in its natural habitat in Mt. Karasu-dake, Oita Pref., Japan. A leaves with winged petioles B flowering plant C front view of a flower. Scale bars: 2 cm (A); 10 cm (B); 1 cm (C). Photographs taken by K. Fuse on September 24, 2020.